METHOD FOR FORMING A COATING ON AN ELECTRONIC OR ELECTRICAL DEVICE

Abstract

An electronic or electrical device or component thereof having a coating formed thereon by exposing said electronic or electrical device or component thereof to a plasma comprising one or more monomer compounds for a sufficient period of time to allow a protective polymeric coating to form on a surface thereof; wherein the protective polymeric coating forms a physical barrier over a surface of the electronic or electrical device or component thereof; wherein each monomer is a compound of formula I(a):

##STR00001##

or a compound of formula I(b)

##STR00002##

Claims

1. An electronic or electrical device or component thereof having a coating formed thereon by exposing said electronic or electrical device or component thereof to a plasma comprising one or more monomer compounds for a sufficient period of time to allow a protective polymeric coating to form on a surface thereof; wherein the protective polymeric coating forms a physical barrier over a surface of the electronic or electrical device or component thereof; wherein each monomer is a compound of formula I(a): ##STR00028## wherein each of R.sub.1 to R.sub.9 is independently selected from hydrogen or halogen or an optionally substituted C.sub.1-C.sub.6 branched or straight chain alkyl group; each X is independently selected from hydrogen or halogen; a is from 0-10; b is from 2 to 14; and c is 0 or 1; and wherein when each X is F or when at least one X is halogen, in particular F, the FTIR/ATR peak intensity ratio of CX.sub.3/C═O of the coating is less than (c+1)0.6e.sup.−0.1n±0.01 where n is a+b+c+1; and wherein when each X is H the FTIR/ATR intensity ratio of CX.sub.3/C═O is less than (c+1) 0.25±0.02; or a compound of formula I(b): ##STR00029## wherein each of R.sub.1 to R.sub.9 is independently selected from hydrogen or halogen or an optionally substituted C.sub.1-C.sub.6 branched or straight chain alkyl group; each X is independently selected from hydrogen or halogen; a is from 0-10; b is from 2 to 14; and c is 0 or 1; and wherein when each X is F or when at least one X is halogen, in particular F, the FTIR/ATR intensity ratio of CX.sub.3/C═O of the coating is less than (c+1)0.6e.sup.−0.1n where n is a+b+c+1; and wherein when each X is H the FTIR/ATR intensity ratio of CX.sub.3/C═O is less than (c+1) 0.25±0.02, optionally wherein the barrier is a conformal physical barrier.

2. An electronic or electrical device or component thereof according to claim 1, wherein the halogen is fluorine.

3. An electronic or electrical device or component thereof according to claim 1 or claim 2, wherein each of R.sub.1 to R.sub.9 is independently selected from hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, sec-butyl, n-pentyl, neopentyl, n-hexyl, isohexyl, and 3-methylpentyl.

4. An electronic or electrical device or component thereof according to claim 3, wherein each of R.sub.1 to R.sub.9 is independently selected from hydrogen or methyl

5. An electronic or electrical device or component thereof according to any preceding claim, wherein a and c are each independently 0 or 1; and b is from 3 to 7.

6. An electronic or electrical device or component thereof according to any preceding claim wherein each X is H.

7. An electronic or electrical device or component thereof according to any of claims 1 to 5, wherein each X is F.

8. An electronic or electrical device or component thereof according to any preceding claim wherein R.sub.1 and R.sub.2 are both hydrogen.

9. An electronic or electrical device or component thereof according to any preceding claim wherein R.sub.3 is hydrogen or methyl.

10. An electronic or electrical device or component thereof according to any preceding claim, wherein R.sub.8 is hydrogen and R.sub.9 is C.sub.1-C.sub.6 branched or straight chain alkyl group.

11. An electronic or electrical device or component thereof according to claim 10, wherein R.sub.9 is methyl.

12. An electronic or electrical device or component according to any preceding claim, wherein each of R.sub.4 to R.sub.7 is hydrogen.

13. An electronic or electrical device or component according to any preceding claim wherein each of R.sub.1 to R.sub.9 is hydrogen, each X is H, a=0 and c=0.

14. An electronic or electrical device or component thereof according to any of claims 7 to 12, wherein the compound of formula I(a) has the following formula: ##STR00030## where n is from 2 to 10.

15. An electronic or electrical device or component thereof according to any of claims 7 to 12, wherein the compound of formula I(a) has the following formula: ##STR00031## where n is from 2 to 10.

16. An electronic or electrical device or component thereof according to claim 14, wherein the compound of formula I(a) is selected from 1H,1H,2H,2H-perfluorohexyl acrylate (PFAC4), 1H,1H,2H,2H-perfluorooctyl acrylate (PFAC6), 1H,1H,2H,2H-perfluorodecyl acrylate (PFAC8) and 1H,1H,2H,2H-perfluorododecyl acrylate (PFAC10).

17. An electronic or electrical device or component thereof according to claim 15, wherein the compound of formula I(a) is selected from 1H,1H,2H,2H-pefluorohexyl methacrylate (PFMAC4), 1H,1H,2H,2H-perfluorooctyl methacrylate (PFMAC6) and 1H,1H,2H,2H-perfluorodecyl methacrylate (PFMAC8).

18. An electronic or electrical device or component thereof according to any of claims 8 to 13, wherein the compound of formula I(a) has the following formula: ##STR00032## wherein a and c are each independently 0 or 1, b=3-7 and n is 4 to 10, where n=a+b+c+1.

19. An electronic or electrical device or component thereof according to any of claims 1 to 13, wherein the compound of formula I(b) has the following formula: ##STR00033## where n is 2 to 12.

20. An electronic or electrical device or component thereof according to claim 18 or claim 19, wherein the compound of formula I(a) is selected form ethyl hexyl acrylate, hexyl acrylate, decyl acrylate, lauryl dodecyl acrylate and iso decyl acrylate.

21. An electronic or electrical device or component thereof according to any of claims 1 to 13, wherein the compound of formula I(b) has the following formula: ##STR00034## where n is from 3 to 13.

22. An electronic or electrical device or component thereof according to claim 21, wherein the compound of formula I(b) has the following formula: ##STR00035## where n is from 3 to 13.

23. An electronic or electrical or component according to any preceding claim, wherein the physical barrier is a conformal physical barrier.

24. An electronic or electrical device or component thereof according to any preceding claim, wherein the electronic or electrical device or component comprises a housing and wherein the coating forms a conformal physical barrier over an internal surface of the housing.

25. An electronic or electrical device or component thereof according to any of the preceding claims, wherein the coating is substantially pin-hole free.

26. An electronic or electrical device or component thereof according to claim 25, wherein ΔZ/d is less than 0.15, where ΔZ is the average height variation on an AFM line scan in nm and d is coating thickness in nm.

27. An electronic or electrical device or component thereof according to any of the preceding claims, wherein the coating is electrically insulating.

28. An electronic or electrical device or component thereof according to any of the preceding claims, wherein the electronic or electrical device or component thereof can withstand immersion in up to 1 m of water for over 30 minutes without failure or corrosion whilst power applied to electronic or electrical device or component.

29. An electronic or electrical device or component according to any of the preceding claims, wherein the coating has a resistance of 8 MOhms or higher when submerged in water and a voltage of 8V is applied for 13 minutes.

30. An electronic or electrical device or component according to one of the preceding claims, wherein the coating has a thickness of 50 nm-10,000 nm.

31. An electronic or electrical device or component according to any one of the preceding claims, wherein the coating has a thickness of 250 nm-2000 nm.

32. An electronic or electrical device or component according to any of the preceding claims, wherein the coating is electrically insulating and wherein the coating is sufficiently compliant that electrical connectors can be joined to the electronic or electrical device or component thereof and an electrical connection made between the electrical connectors and electronic or electrical device or component thereof without the requirement to first remove the coating.

33. An electronic or electrical device or component according to any of the preceding claims, wherein the coating is electrically insulating and has a thickness of 1-2.5 microns and wherein a force of 20-100 g applied to the coating allows an electrical connection to be made with the electronic or electrical device or component thereof in the local area where the force has been applied.

34. An electronic or electrical device or component according to any of the preceding claims, wherein the coating is electrically insulating and has a thickness of less than 1 micron and wherein a force of less than 5-20 g applied to the coating allows an electrical connection to be made in the local area of the coating where the force has been applied

35. An electronic or electrical device or component thereof according to any of the preceding claims wherein the coating forms a water repellent surface defined by a static water contact angle (WCA) of at least 90°.

36. An electronic or electrical device or component thereof according to any of the preceding claims, wherein X is F and wherein the coating forms a water repellent surface defined by a static water contact angle (WCA) of at least 100°.

37. An electronic or electrical device or component thereof according to any of the preceding claims, wherein the electronic or electrical device or component thereof is selected from mobile phones, smartphones, pagers, radios, sound and audio systems such as loudspeakers, microphones, ringers and/or buzzers, hearing aids, personal audio equipment such as personal CD, tape cassette or MP3 players, televisions, DVD players including portable DVD players, video recorders, digi and other set-top boxes, computers and related components such as laptop, notebook, tablet, phablet or palmtop computers, personal digital assistants (PDAs), keyboards, or instrumentation, games consoles, data storage devices, outdoor lighting systems, radio antennae and other forms of communication equipment, and printed circuit boards.

38. A method for treating an electronic or electrical device or component thereof as defined in any preceding claim, comprising: exposing said electronic or electrical device or component thereof to a plasma comprising one or more monomer compounds for a sufficient period of time to allow a protective polymeric coating to form on the electronic or electrical device or component thereof, the protective polymeric coating forming a physical barrier over a surface of said electronic or electrical device or component thereof; wherein each monomer is a compound of formula (Ia): ##STR00036## wherein each of R.sub.1 to R.sub.9 is independently selected from hydrogen or halogen or an optionally substituted C.sub.1-C.sub.6 branched or straight chain alkyl group; each X is independently selected from hydrogen or halogen; a is from 0-10; b is from 2 to 14; and c is 0 or 1; or a compound of formula (Ib): ##STR00037## wherein each of R.sub.1 to R.sub.9 is independently selected from hydrogen or halogen or an optionally substituted C.sub.1-C.sub.6 branched or straight chain alkyl group; each X is independently selected from hydrogen or halogen; a is from 0-10; b is from 2 to 14; and c is 0 or 1.

39. A method according to claim 38 wherein the barrier is a conformal physical barrier.

40. A method according to claim 38 or claim 39, wherein the step of exposing said electronic or electrical device or component thereof to a plasma comprises a first continuous wave (CW) deposition step and second pulsed (PW) deposition step.

41. A method according to claim 40 wherein the pulses of the pulsed plasma are applied in a sequence which yields a ratio of time on:time off in the range of from 0.001 to 1.

42. A method according to claim 40 to 41, wherein the pulsing conditions are time on=10-500 μs and time off=0.1 to 30 ms.

43. A method according to any of claims 40 to 42, wherein the monomer is introduced during the pulsing at a flow rate of between 1.5 to 2500 sccm.

44. A method according to any of claims 40 to 44, wherein the power to monomer flow ratio during the pulsed plasma is between 2-60 W/sccm.

45. A method according to any of claims 38 to 44, wherein the compound of formula I(a) is selected from 1H,1H,2H,2H-perfluorohexyl acrylate (PFAC4), 1H,1H,2H,2H-perfluorooctyl acrylate (PFAC6), 1H,1H,2H,2H-perfluorodecyl acrylate (PFAC8) and 1H,1H,2H,2H-perfluorododecyl acrylate (PFAC10).

46. A method according to any of claims 38 to 44, wherein the compound of formula I(a) is selected from 1H,1H,2H,2H-pefluorohexyl methacrylate (PFMAC4), 1H,1H,2H,2H-perfluorooctyl methacrylate (PFMAC6) and 1H,1H,2H,2H-perfluorodecyl methacrylate (PFMAC8).

47. A method according to any of claims 38 to 44 wherein the compound of formula I(a) is selected from ethyl hexyl acrylate, hexyl acrylate, decyl acrylate, lauryl dodecyl acrylate and iso decyl acrylate.

48. A method according to any of claims 38 to 47, further comprising a preliminary activation step of applying a CW plasma in the presence of an inert gas.

49. An electronic or electrical device comprising a housing and an internal electronic or electrical component, wherein the internal component comprises a coating, wherein the coating is formed by any of the methods of claims 38 to 48 and/or the internal component is a component according to any one of claims 1 to 37.

50. A method according to any of claims 38 to 49, wherein the electronic or electrical device or component thereof is selected from mobile phones, smartphones, pagers, radios, sound and audio systems such as loudspeakers, microphones, ringers and/or buzzers, hearing aids, personal audio equipment such as personal CD, tape cassette or MP3 players, televisions, DVD players including portable DVD players, video recorders, digi and other set-top boxes, computers and related components such as laptop, notebook, tablet, phablet or palmtop computers, personal digital assistants (PDAs), keyboards, or instrumentation, games consoles, data storage devices, outdoor lighting systems, radio antennae and other forms of communication equipment.

Description

[0152] The present invention will now be further described with reference to the following non-limiting examples and the accompanying illustrative drawings, of which:

[0153] FIG. 1 illustrates the electrical test apparatus for determining the resistance of the coating;

[0154] FIG. 2 shows a tapping mode image of the coatings over 5×5 m.sup.2 field of view (left) and a representative contour line indicating height variation (z-axis) of the coating (right);

[0155] FIG. 3 is a FTIR/ATR spectrum of a 1000 nm thick coating formed from PFAC8 monomer;

[0156] FIG. 4 is a graph of Resistance in water of PW PFAC8 coatings at 8V after 13 min hold versus the FTIR/ATR CF3/C═O peak area ratio;

[0157] FIG. 5 is a graph of the resistance in water of PW PFAC10 coatings at 8V after 13 min hold versus the FTIR/ATR CF3/C═O peak area ratio;

[0158] FIG. 6 is a graph of the resistance in water of PW PFAC6 coatings at 8V after 13 min hold versus the FTIR/ATR CF3/C═O peak area ratio;

[0159] FIG. 7 is a graph of the resistance in water of PW PFAC4 coatings at 8V after 13 min hold versus the FTIR/ATR CF3/C═O peak area ratio;

[0160] FIG. 8 is a graph showing the ATR area ratios for the different perfluoro acrylate monomers;

[0161] FIG. 9 is a graph showing the critical ATR ratio values as a function of the side chain length of the initial monomer;

[0162] FIG. 10 is a graph showing the resistance in water of PW PFMAC8 coatings at 8V after 13 min hold versus the FTIR/ATR CF3/C═O peak area ratio;

[0163] FIG. 11 is a graph showing the resistance in water of PW PFMAC6 coatings at 8V after 13 min hold versus the FTIR/ATR CF3/C═O peak area ratio;

[0164] FIG. 12 is a graph showing the resistance in water of PW PFMAC4 coatings at 8V after 13 min hold versus the FTIR/ATR CF3/C═O peak area ratio; and

[0165] FIG. 13 is a graph showing the critical FTIR/ATR ratio values as a function of the side chain length of the initial perfluoro-acrylate (PFACn) or perfluoro methacrylate (PFMACn) monomer;

[0166] FIG. 14 illustrates possible cross linking mechanisms for PFAC8; and

[0167] FIG. 15 is a graph of resistance (with applied 8V for 13 mins) against FTIR/ATR C═O/total area for PFAC8; and

[0168] FIG. 16 is a graph of resistance (with applied 8V for 13 mins) against FTIR/ATR CF3/total area for PFAC8; and

[0169] FIG. 17 is a graph of resistance (with applied 8V for 13 mins) against FTIR/ATR CF3/C═O;

[0170] FIG. 18 is a graph of (A) FTIR/ATR C═O/total against power and (B) FTIR/ATR CF.sub.3/total against power, both for PFAC4 coatings;

[0171] FIG. 19 is a graph of contact force Fc against coating thickness;

[0172] FIG. 20 is a graph of the resistance in water of ethyl hexyl acrylate coatings at 8V after 13 min hold versus the FTIR/ATR CH3/C═O peak area ratio;

[0173] FIG. 21 is a graph of the resistance in water of hexyl acrylate coatings at 8V after 13 min hold versus the FTIR/ATR CH3/C═O peak area ratio;

[0174] FIG. 22 is a graph of the resistance in water of iso decyl acrylate coatings at 8V after 13 min hold versus the FTIR/ATR CH3/C═O peak area ratio;

[0175] FIG. 23 is a graph of the resistance in water of several non-fluorinated coatings at 8V after 13 min hold versus the FTIR/ATR CH.sub.3/C═O peak area ratio; ethyl hexyl acrylate coating represented by diamonds; hexyl acrylate represented by squares; decyl acrylate represented by triangles; lauryl (dodecyl) acrylate represented by crosses; isodecyl acrylate represented by strikethrough crosses.

EXAMPLE 1

[0176] Process Set Up and Parameters

[0177] Plasma polymerization experiments were carried out in a cylindrical glass reactor vessel with a volume of 2.5 liters. The vessel was in two parts, coupled with a Viton O-ring to seal the two parts together under vacuum. One end of the reactor was connected to a liquid flow controller which was heated at 70° C. and this was used for delivering monomer at a controlled flow rate.

[0178] The other end of the reactor was connected to a metal pump line fitted with pressure gauges, pressure controlling valve, liquid nitrogen trap and a vacuum pump. A copper coil electrode was wrapped around the outside of the reactor (11 turns of 5 mm diameter piping) and this was connected to a RF power unit via an L-C matching network. For pulsed plasma deposition the RF power unit was controlled by a pulse generator.

[0179] The monomer used for this example was PFAC-8, i.e. 1H,1H,2H,2H-heptadecafluorodecylacrylate (CAS #27905-45-9) of formula

##STR00019##

[0180] A range of experiments were carried out using the parameters shown in Tables 1A-1D. In each experiment a sample was placed inside the glass reactor vessel such that it sat on the bottom of the reactor vessel and inside the volume surrounded by the copper coil electrode. The reactor was evacuated down to base pressure (typically <10 mTorr). The monomer was delivered into the chamber using the flow controller, which typical monomer gas flow values being between 2-25 sccm. The chamber was heated to 45° C. The pressure inside the reactor was maintained at 30 mTorr. The plasma was produced using RF at 13.56 MHz and the process typically consisted of two main steps; the continuous wave (CW) plasma and the pulsed wave (PW). The CW plasma was for 2 minutes and the duration of the PW plasma varied in different experiments. The peak power setting was 50 W in each case, and the pulse conditions were time on (T.sub.on)=37 μs and time off (T.sub.off)=6 ms. Two coatings were formed using T.sub.on=37 μs and T.sub.off=20 ms. At the end of the deposition the RF power was switched off, the flow controller stopped and the chamber pumped down to base pressure. The chamber was the vented to atmospheric pressure and the coated samples removed.

[0181] For each experiment, two test PCBs and two Si wafers were used. The Si wafers allow physical properties of the formed coating to be measured, for example AFM for surface morphology and XRR for coating density. The metal tracks of the test PCBs were gold coated copper. The Si wafers were placed on the top front side of the PCBs.

[0182] Tables 1A-1D show the different process parameters for coatings formed in this example and the measured properties of these coatings.

EXAMPLE 2

[0183] A number of properties of exemplary coated substrates formed according to the invention were investigated.

[0184] Resistance at Fixed Voltage Over Time

[0185] This test method has been devised to evaluate the ability of different coatings to provide an electrical barrier on printed circuit boards and predict the ability of a smart phone to pass the IEC 60529 14.2.7 (IPX7) test. The method is designed to be used with tap water. This test involves measuring the current voltage (IV) characteristics of a standardised printed circuit board (PCB) in water. The PCB has been designed with spacing of 0.5 mm between electrodes to allow assessment of when electrochemical migration occurs across the tracks in water. The degree of electrochemical activity is quantified by measuring current flow; low current flow is indicative of a good quality coating. The method has proved to be extremely effective at discriminating between different coatings. The performance of the coatings can be quantified, e.g. as a resistance at 4 and 8V and 21 V. The measured resistance on the untreated test device is about 100 ohms when 16V/mm are applied.

[0186] The coated PCB 10 to be tested is placed into a beaker 12 of water 14 and connected to the electrical test apparatus via connections 16,18 as shown FIG. 1. The board is centred horizontally and vertically in the beaker to minimise effects of local ion concentration (vertical location of the board is very important; water level should be to the blue line). When the PCB is connected, the power source is set to the desired voltage and the current is immediately monitored. The voltage applied is for example 8V and the PCB is held at the set voltage for 13 minutes, with the current being monitored continuously during this period.

[0187] The coatings formed by the different process parameters are tested and the results are shown in Tables 1A-1D. It has been found that when coatings have resistance values higher that 8 MOhms, the coated device will pass successfully an IPX7 test. The nature of the device being coated (for example the type of smart phone) will influence the test, for example due to the variations in materials, ingress points, power consumption etc).

[0188] Critical Force (Fc)

[0189] The electrical conductivity of a coating can change significantly when a compressive stress is applied to the coating. The change in the electrical conductivity will depend on the amplitude of strain experienced by the coating, amount of defects and type of polymer matrix of the coating. This behaviour is explained on the basis of formation or destruction of a conductive network, which further depends on the viscosity (stiffness) of the polymer matrix. To evaluate the ability of the coating to provide electrical contact under relatively low force, a contact force test is performed.

[0190] The contact force test is an electrical test procedure which involves measuring the critical force (Fc) or pressure (Pc) that has to be applied to the insulating coating via a flat probe, for electrical break down through the coating to occur. The test can be used either on PCBs of smart phones or on strip boards (Test PCBs) which are placed as witness samples during processes.

[0191] The test uses a flat probe e.g 1 mm in diameter (or e.g a spherical probe of 2 mm diameter), contacting the planar film's surface. The probe is mounted on a support stand and the arrangement is such that variations in the force applied by the probe to the surface of the sample are immediately recorded by a weighing scale (or load cell) on which the sample is placed. With this arrangement the resolution in applied pressure is about 15 KPa (force 5 g).

[0192] The normal procedure is to manually ramp the force applied by the probe on the planar surface of the sample while observing the resistance between the probe and the conductive substrate. The force is manually or automatically increased up to the point (Fc) where current break down through the film occurs.

[0193] This test allows the electrical insulation characteristics of the sample to be analyzed at a number of different points across the surface thus providing an idea of the uniformity of the surface layer.

[0194] The Fc values for the coated PCB coatings formed in Example 1 are shown in Tables 1A-1D.

[0195] FIG. 19 is a graph of Fc against coating thickness for PFAC8 made according to Example 1. This shows that a force of 20-100 g can be applied to the coating with a thickness of 1-2.5 microns to allow an electrical connection to be made.

[0196] Typical Fc values for a coating with thickness of about 1000 nm is circa 35 g. The coating can achieve barrier functionality at relatively low (250-800 nm) thickness, making it possible to achieve electrical contact after the application of relatively low (<15 g) force. This is the advantage that coating of the present invention can provide when compared with other standard barrier coatings.

[0197] Coating Thickness

[0198] The thickness of the coatings formed in Example 1 was measured using spectroscopic reflectometry apparatus (Filmetrics F20-UV) using optical constants verified by spectroscopic elipsometry.

[0199] Spectroscopic Ellipsometry Spectroscopic ellipsometry is a technique for measuring the change in polarization between incident polarized light and the light after interaction with a sample (i.e. reflected, transmitted light etc). The change in polarization is quantified by the amplitude ratio Ψ and phase difference Δ. A broad band light source is used to measure this variation over a range of wavelengths and the standard values of Ψ and Δ are measured as a function of wavelength. The ITAC MNT Ellipsometer is an AutoSE from Horiba Yvon which has a wavelength range of 450 to 850 nm. Many optical constants can be derived from the Ψ and Δ values, such as film thickness and refractive index.

[0200] Data collected from the sample measurements includes the intensities of the harmonics of the reflected or transmitted signal in the predefined spectral range. These are mathematically treated to extract intensity values called Is and Ic as f(I). Starting from Ic and Is the software calculates Ψ and Δ. To extract parameters of interest, such as thickness or optical constants, a model has to be set up to allow theoretical calculation of Ψ and Δ. The parameters of interest are determined by comparison of the theoretical and experimental data files to obtain the best fit (MSE or X.sup.2). The best fit for a thin layer should give an X.sup.2<3, for thicker coatings this value can be as large as 15. The model used is a three layer Laurentz model including PTFE on Si substrate finishing with a mixed layer (PTFE+voids) to account for surface roughness.

[0201] Examples of optical properties of coatings formed in Example 1 are given in table 2. This data relates to coatings 9 and 10 in Tables 1A-1D.

[0202] Spectroscopy Reflectrometry

[0203] Thickness of the coating is measured using a Filmetrics F20-UV spectroscopy reflectrometry apparatus. This instrument (F20-UV) measures the coating's characteristics by reflecting light off the coating and analyzing the resulting reflectance spectrum over a range of wavelengths. Light reflected from different interfaces of the coating can be in- or out-of-phase so these reflections add or subtract, depending upon the wavelength of the incident light and the coating's thickness and index. The result is intensity oscillations in the reflectance spectrum that are characteristic of the coating.

[0204] To determine the coating's thickness, the Filmetrics software calculates a theoretical reflectance spectrum which matches as closely as possible to the measured spectrum. It begins with an initial guess for what the reflectance spectrum should look like, based on the nominal coating stack (layered structure). This includes information on the thickness (precision 0.2 nm) and the refractive index of the different layers and the substrate that make up the sample (refractive index values can be derived from spectroscopic ellipsometry). The theoretical reflectance spectrum is then adjusted by adjusting the coating's properties until a best fit to the measured spectrum is found. Measured coatings must be optically smooth and within the thickness range set by the system configuration requirements is shown in table 3.

[0205] The thicknesses of the coatings produced in Example 1 are shown in Tables 1A-1 D, which typical thickness being 750-3500 nm.

[0206] Alternative techniques for measuring thickness are stylus profilometry and coating cross sections measured by SEM.

[0207] Surface Morphology

[0208] The surface morphology of the coatings is measured using atomic force microscopy (AFM). Analyses are carried out with a Veeco Park Autoprobe AFM instrument, operated in the tapping imaging mode, using Ultrasharp NSC12, diving-board levers with spring constants in the range 4-14 N/m, and with resonant frequencies in the range 150-310 kHz. A high-aspect ratio probe, with a radius of curvature at the tip apex of <10 nm and opening angle <20° was used. Fields of view of 10×10, 5×5 and 1×1 m.sup.2 were imaged, with the larger field of view being the more informative. Surface roughness, RMS (root mean square), was calculated by standard software, for each field of view. The images obtained were 256×256 pixels in all cases.

[0209] From the AFM morphological analysis of the coatings two parameters can be extracted; (a) the RMS roughness (r) of the coating and b) the ratio ΔZ/d whereas d is the thickness of the coating and ΔZ is explained below.

[0210] FIG. 2 shows a tapping mode image over 10×10 m.sup.2 field of view (left hand side) of a specimen example (thickness d=1230 nm) prepared according to Example 1 and a contour line plot (right hand side) showing the data used for calculation of RMS roughness. The ΔZ value indicated on the plot has been taken over an area of the graph that represents the majority of the coating. Peaks that lie above the ΔZ range indicate large particles and troughs that fall below the ΔZ range show voids or pinholes in the coating. The width of the peaks also gives an indication of the particle size. The example shown is sample 7 in tables 1A-1D with RMS roughness(r) was 35±3 nm and ΔZ=80±10 nm giving ΔZ/d=0.065.

[0211] It has been shown that ΔZ/d<0.15, indicates a pinhole free coating. Morphological parameters are good indicators for pinhole free coatings. However, this property alone does not account for the high performance of the coating.

[0212] Chemical Analysis

[0213] For samples with a thickness higher than 200 nm, a Fourier Transform Infra-Red Spectroscopy (FTIR) using an Attenuated Total Reflection (ATR) sampling technique is used for chemical characterization and coating quality assessment (FTIR/ATR analysis). The spectrometer used was an MIR Standard Perkin Elmer Frontier equipped with the Frontier UATR Diamond/ZnSe with 1 Reflection Top-Plate producing high quality spectra through the use of a pressure arm allowing good contact of the sample with the diamond crystal. Scan range of all measurements was 4,000-650 cm.sup.−1 with 0.4 cm.sup.−1 resolution and 10,000/1 pk-pk noise for a 5 second scan.

[0214] For the technique to be successful, the sample must be in direct contact with the ATR crystal. As with all FT-IR measurements, an infrared background is collected, in this case, from the clean ATR diamond crystal. The crystals are usually cleaned by using a solvent soaked piece of tissue. After the crystal area has been cleaned and the background collected, the solid sample is placed onto the small crystal area. The pressure arm should be positioned over the sample. Force is applied to the sample, pushing it onto the diamond surface. After the spectrum has been collected, the user must check that the crystal area is clean before placing the next sample on the crystal.

[0215] A typical FTIR/ATR spectrum from a 1000 nm thick coating prepared as described in Example 1 is shown in FIG. 3. Assignments of the absorption peaks are also shown.

[0216] To analyse the data, a baseline is automatically subtracted from the spectrum, the integrated area under certain peaks of interest is measured, followed by the calculation of certain peak area ratios.

[0217] The peak areas used for this analysis are shown in FIG. 3 by rectangles surrounding the peaks of interest. The band assignments and the integration limits are shown in table 4.

[0218] The ratio between these two peak areas A (1335)/A(1737) is an important parameter characterising the chemistry and more specifically the degree of cross linking in the coating. It is found that coatings with thickness d>800 nm and A(1335)/A(1737<0.23±0.01 have undergone sufficient cross linking to have the desired functionality, providing they evenly cover the surface of the item under protection. It is established that plasma treatment would lead to the formation of a polymeric material that is far more cross-linked than its conventionally polymerised counterpart. Cross linking would affect the abundance of —CF3 functionalities in the coating.

[0219] Coatings with thickness d<800 nm require a correction to be applied to the measured ratio value A(1335)/A(1737) to account for the effect of the reduced thickness on the intensity of the selected FTIR/ATR peaks.

[0220] In this case, the corrected ratio=measured A(1335)/A(1737)−(−0.0003*d+0.255) where d=coating thickness in nm.

[0221] Physical Density Measurements

[0222] The physical density of the coatings prepared in Example 1 was estimated gravimetrically and also by XRR for more accuracy on very thin coatings. The polymer coating with the desired properties has been found to have a higher density than the corresponding monomer due to cross linking, which is in agreement with the FTIR/ATR findings.

[0223] Table 5 shows the densities of three monomers and their resultant coatings, measured by X-ray Reflectometry (XRR). The coating formed from (I) is formed using the present method, whereas the coating formed from (II) is formed using a prior art method. The density values for Parylene C have been derived from literature [1].

[0224] It can be seen that the coating (I) formed from PFAC8 according to the present invention is significantly denser than coating (Ill) formed from the same monomer using prior art methods. It is also significantly denser than Parylene C coating, a conventionally used barrier coating.

[0225] Relationship Between Resistance and FTIR/ATR Data

[0226] The relationship between the resistance value of the coating and the FTIR/ATR ratio of the CF3/C═O intensities is shown in FIG. 4, using the data from tables 1A-1D. The resistance value is resistance at 8V for 13 minutes in tap water and the FTIR/ATR ratio refers to A(1535)/A(1737).

[0227] As discussed earlier, coatings with values for R higher than 8 MOhms will pass an IPX7 test. FIG. 4 shows that coatings with FTIR/ATR CF3/C═O values of less than 0.23±0.01 meet this criterion. Looking at the results in tables 1A-1D, it can be seen that coatings 1, 2, 3 and 4 do not meet these criterion. These coatings have been produced with the lowest flow settings (˜2.2 sccm) while coatings 1 and 2 have the lowest average power setting.

[0228] From the Fc results in tables 1A-1D, it is also apparent that the coatings can be produced so that they provide Fc values below 45 g. These values can become even lower (<10 g) when the coatings are thinner than 800 nm.

[0229] Other Perfluoroacrylate Monomers

[0230] Similar high performing coatings have been produced with other perfuoro acrylate and methyl acrylate monomers with different side chain lengths (n=4, 6, 8 and 10), which are described in the following examples.

EXAMPLE 3—PFAC10

[0231] The experiment of example 1 was repeated using PFAC10 (1H,1H,2H,2H-perfluorododecyl acrylate; CAS no. 17741-60-5) instead of PFAC8.

[0232] FIG. 5 is a graph of resistance in water of PW PFAC10 coatings at 8V after 13 min hold versus the FTIR/ATR CF3/C═O peak area ratio.

[0233] Looking at coatings with values for R higher than 8 MOhms (which will pass an IPX7 test), the critical value of the ATR CF3/C═O area ratio is 0.19±0.01.

EXAMPLE 4—PFAC6

[0234] The experiment of example 1 was repeated using PFAC6 (1H,1H,2H,2H-perfluorooctyl acrylate; CAS no. 17527-29-6) instead of PFAC8.

[0235] FIG. 6 is a graph of resistance in water at 8V after 13 min hold versus the FTIR/ATR CF3/C═O peak area ratio is shown

[0236] Looking at coatings with values for R higher than 8 MOhms (which will pass an IPX7 test), the critical value of the ATR CF3/C═O area ratio is 0.3±0.01.

EXAMPLE 5—PFAC4

[0237] The experiment of example 1 was repeated using PFAC 4 (1H,1H,2H,2H-perfluorohexyl acrylate; CAS no. 52591-27-2) instead of PFAC8.

[0238] FIG. 7 is a graph of resistance in water at 8V after 13 min hold versus the FTIR/ATR CF3/C═O peak area ratio is shown.

[0239] Looking at coatings with values for R higher than 8 MOhms (which will pass an IPX7 test), the critical value of the ATR CF3/C═O area ratio is 0.36±0.02 Analysis of perfluoroacrylate monomers.

[0240] For the examples 3-5, the FTIR/ATR area ratio between the peak representing the stretching mode of the end CF3 terminal group and the stretching mode of the C═O ester bond from the acrylate have been measured for each monomer and for each plasma polymer produced from those monomers.

[0241] The area limits used for these measurements are shown in Table 6.

[0242] The monomers PFAC4-PFAC10 all have formula (II) below,

##STR00020##

where n is 4 for PFAC4, 6 for PFAC6, 8 for PFAC8 and 10 for PFAC10.

[0243] FIG. 8 is a graph of the FTIR/ATR critical ratio (i.e. below which the coating provides good barrier functionality) against n and shows that the selected ATR area ratio for each monomer increases exponentially with the length of the side chain. This is expected because during the ATR measurement the evanescent wave will interact with dipoles in the film in all orientations defining the C—F bonding envelope of each substance measured. As the length of the side chain increases the intensity of the peak representing the CF3 stretching will increase along with the signal of peaks representing CF2 and CF2-CF3 vibration modes.

[0244] For each type of the plasma polymer prepared there is a corresponding functionality line like the one presented in FIG. 4 for PFAC8 and a critical ATR ratio value. FIG. 9 shows theses critical values for each polymer, as a function of the side chain length n of the monomer used to prepare this polymer.

[0245] It can be clearly seen that the values are related to the length (n) of the side chain by an exponential relationship. The applicants have realized that a coating with an FTIR/ITR ratio A(1)/A(2)<0.56e.sup.−0.11n (integration limits given in Table 8) is a polymer with the desired functionality.

[0246] To identify the monomer from which the plasma polymer is produced, the ATR spectrum can be used. Table 7 shows the main features that differentiate the ATR spectra of the polymers.

[0247] Perfluoro Methacrylate Monomers

[0248] High performing coatings have also been produced with perfluoro methyl acrylate monomers with different side chain lengths as defined in formula (IV)

##STR00021##

where n=4, 6, 8 and 10. The resultant coatings are described in the following examples. The area limits used for these measurements are shown in Table 8.

EXAMPLE 6—PFMAC8

[0249] The experiment of example 1 was repeated, using PFMAC8 (1H,1H,2H,2H-perfluorodecyl methacrylate; CAS no. 1996-88-9) in place of PFAC8.

[0250] A graph of the resistance in water of PW PFMAC8 coatings at 8V after 13 min hold versus the FTIR/ATR CF3/C═O peak area ratio is shown in FIG. 10.

[0251] The critical value of the ATR CF3/C═O area ratio is 0.19±0.01

EXAMPLE 7—PFMAC6

[0252] The experiment of example 1 was repeated, using PFMAC6 (1H,1H,2H,2H-perfluorooctyl methacrylate; CAS no. 2144-53-8) in place of PFAC8.

[0253] A graph of the resistance in water of PW PFMAC6 coatings at 8V after 13 min hold versus the FTIR/ATR CF3/C═O peak area ratio is shown in FIG. 11.

[0254] The critical value of the ATR CF3/C═O area ratio is 0.24±0.02

EXAMPLE 8—PFMAC4

[0255] The experiment of example 1 was repeated, using PFMAC4 (1H,1H,2H,2H-pefluorohexyl methacrylate; CAS no. 1799-84-4) in place of PFAC8.

[0256] A graph of the resistance in water of PW PFMAC4 coatings at 8V after 13 min hold versus the FTIR/ATR CF3/C═O peak area ratio is shown in FIG. 12.

[0257] The critical value of the ATR CF3/C═O area ratio is 0.31±0.02 Analysis of PFACn monomers and PFMACn monomers.

[0258] FIG. 13 shows the critical FTIR/ATR ratio values as a function of the side chain length for the initial perfluoro-acrylate (PFACn) or perfluoro methacrylate (PFMACn) monomer and the resulting plasma polymers.

[0259] It can be seen that the critical FTIR/ATR CF3/C═O values for PFMACn coatings with the desired behavior follow the same trend as the PFACn coatings with an exponential relationship. For compounds of formula III, the applicants have realized that a value of the FTIR/ATR ratio A(1)/A(2), 0.50e.sup.−0.12n results in a coating with the desired functionality.

EXAMPLE 9—PARYLENE

[0260] The properties of Parylene coatings prepared by chemical vapour deposition (CVD) on the same substrates as the coatings described in examples 1 and 3-8, are shown in Table 16 for comparison purposes.

[0261] As shown in Table 9, Parylene coatings with resistance values above 8 MOhms can only be achieved with coatings thicker than 2500 nm. When reaching these high thicknesses the coating detrimentally affects the operation of the device, as shown by the high critical force of over >250 g. With such a high thickness, the coating does not allow sufficient electrical contact to be made under typical contact forces, making masking of contacts a necessary operation before the coating application.

[0262] High performing coatings have also been produced with non-fluorinated monomers as shown in Examples 10 to 12.

EXAMPLE 10

[0263] The experiment of example 1 was repeated, using ethyl hexyl acrylate (CAS no. 103-11-7) in place of PFAC8.

##STR00022##

[0264] A graph of the resistance in water of ethyl hexyl acrylate coatings at 8V after 13 min hold versus the FTIR/ATR CH3/C═O peak area ratio is shown in FIG. 20.

[0265] The critical value of the ATR CH3/C═O area ratio is 0.16±0.01.

EXAMPLE 11

[0266] The experiment of example 1 was repeated, using hexyl acrylate (CAS no. 2499-95-8) in place of PFAC8.

##STR00023##

[0267] A graph of the resistance in water of hexyl acrylate coatings at 8V after 13 min hold versus the FTIR/ATR CH3/C═O peak area ratio is shown in FIG. 21.

[0268] The critical value of the ATR CH.sub.3/C═O area ratio is 0.16±0.01.

EXAMPLE 12

[0269] The experiment of example 1 was repeated, using iso decyl acrylate (CAS no. 1330-61-6) in place of PFAC8.

##STR00024##

[0270] The process parameters and coating properties are given in Table 10.

[0271] A graph of the resistance in water of iso decyl acrylate coatings at 8V after 13 min hold versus the FTIR/ATR CH.sub.3/C═O peak area ratio is shown in FIG. 22.

[0272] The critical value of the ATR CH.sub.3/C═O area ratio is 0.30±0.01.

[0273] Summary of Non-Fluorinated Monomers

[0274] A graph of the resistance in water of several coatings at 8V after 13 min hold versus the FTIR/ATR CH.sub.3/C═O peak area ratio is shown in FIG. 23. This graph includes data from coatings formed from the following monomers: ethyl hexyl acrylate, hexyl acrylate, decyl acrylate, lauryl dodecyl acrylate and iso decyl acrylate.

[0275] The structures of decyl acrylate (CAS no. 2156-96-9) and deodecyl(lauryl) acrylate (CAS no. 2156-97-0) are given below:

##STR00025##

[0276] FTIR/ATR analysis of the CH3/C═O peaks for the monomers in FIG. 23 show that, with the exception of iso decyl acrylate (IDA), they all produce the desired coatings (i.e. having resistance values higher that 1×10.sup.7 Ohms) at the same critical ATR ratio CH3/C═O=0.16±0.01. This critical ATR ratio is independent of chain length. The area limits used for these measurements are shown in Table 11.

[0277] The only exception is IDA for which the critical ATR ratio=0.30±0.01, i.e. double that of the coatings formed from the other monomer in FIG. 23. This is explained by the fact that IDA has two CH3 terminal groups at the end of the side chain.

[0278] The applicants have been able to identify a general chemical structure for both fluorinated and non-fluorinated monomers which gives the desired performance. The monomer is a compound of formula I(a):

##STR00026##

wherein each of R.sub.1 to R.sub.9 is independently selected from hydrogen or a C.sub.1-C.sub.6 branched or straight chain alkyl group; each X is independently selected from hydrogen or halogen; a is from 0-10; b is from 2 to 14; and c is 0 or 1; [0279] and wherein when each X is F the FTIR/ATR intensity ratio of CX.sub.3/C═O of the coating is less than (c+1)0.6e.sup.−0.1n±0.01 where n is a+b+c+1; [0280] and wherein when each X is H the FTIR/ATR intensity ratio of CX.sub.3/C═O is less than (c+1) 0.25±0.02; or
the monomer is a compound of formula I(b):

##STR00027##

wherein each of R.sub.1 to R.sub.9 is independently selected from hydrogen or a C.sub.1-C.sub.6 branched or straight chain alkyl group; each X is independently selected from hydrogen or halogen; a is from 0-6; b is from 2 to 14; and c is 0 or 1; and wherein when each X is F the FTIR/ATR intensity ratio of CX.sub.3/C═O of the coating is less than (c+1)0.6e.sup.−0.1n±0.01 where n is a+b+c+1; and wherein when each X is H the FTIR/ATR intensity ratio of CX.sub.3/C═O is less than (c+1) 0.25±0.02.

EXAMPLE 13

[0281] The experiment of example 1 was repeated using vinyl decanoate (CAS no. 4704-31-8). The process parameters and coating properties are shown in table 12.

[0282] All of the coatings in the examples have a coating thickness in the range of 250 nm to 5000 nm. On examination the coatings were found to be conformal and the fact that all of the coatings either exceed the IPX7 test or are close to it are indicative that they form physical barriers. The use of plasma polymerisation to deposit the coating has the advantage that the coating can be made sufficiently thick to provide a physical barrier whilst being significantly thinner than prior art conformal coatings. This thickness range has the advantage that it is sufficiently thick to form a physical barrier yet thin enough to allow electrical connections to be made without first removing it.

[0283] The use of plasma polymerisation also has the advantage that good ingress of the monomer during the plasma polymerisation technique ensures that the coating covers all of the desired areas, for example the entire external surface. Where the electronic or electrical device comprises a housing, the entire internal surface of the housing can be coated (by exposing the open housing to the plasma) to protect the electronic components inside the housing once the device is assembled.

TABLE-US-00001 TABLE 1A Process parameters and coating properties for coatings formed from PFAC8 Monomer: PFAC8 PW processes Parameter Units 1 2 3 4 5 6 7 CW time min 2 2 2 2 2 Ton μs 36 36 36 36 36 Toff ms 20 6 6 6 6 monomer pressure mtorr 30 30 30 30 30 PW power Watts 50 50 50 50 50 flow rate (STP) sccm 2.2 2.20 2.2 2.63 2.63 Chamber T ° C. 45 45 45 45 45 PW time min 30 10 25 45 15 power/volume Watts/litre 20 20 20 20 20 power/flow Watts/(sccm) 23 23 23 19 19 monomer ml/min 0.028 0.028 0.028 0.034 0.034 volume/min

TABLE-US-00002 TABLE 1B Process parameters and coating properties for coatings formed from PFAC8 Monomer: PFAC8 PW processes Parameter Units 1 2 3 4 5 6 7 Thickness (d) Si nm 1000 1059 1185 1947 3770 934 1263 Thickness (d) SB nm 997 1117 938 1631 2760 832 1150 density (ρ) g .Math. cm−3 1.6 1.83 Δρ from g .Math. cm−3 0 0.23 5 monomer RMS roughness nm  45±8  50±10 26±2  35±3  ΔZ nm 200±20 200±50  70±5  80±10 Topography ΔZ/d by AFM 0.19 0.17 0.02 0.06 CF3/C═O on SB 0.28 0.26 0.28 0.25 0.18 0.23 0.22 R at 8 V 13 min Ω 8.00E±05 6.50E±05 1.50E±05 2.40E±06 1.50E±07 1.00E±07 3.70E±07 R/d (13 min) Ω/nm 8.02E±02 5.82E±02 1.60E±02 1.47E±03 5.43E±03 1.20E±04 3.22E±04 Critical force g 38 60 35 56 44 37 35

TABLE-US-00003 TABLE 1C Process parameters and coating properties for coatings formed from PFAC8 Monomer: PFAC8 PW processes CW Parameter Units 8 9 10 11 12 13 14 CW time min 2 2 2 10 15 Ton μs 36 36 36 n/a n/a Toff ms 6 6 6 n/a n/a monomer pressure mtorr 30 30 30 30 30 PW power Watts 50 50 50 50 25 flow rate (STP) sccm 8.50 8.50 19.32 19.32 2.60 Chamber T ° C. 45 45 45 45 45 PW time min 5 10 10 0 0 power/volume Watts/litre 20 20 20 20 10 power/flow Watts/(sccm) 6 6 3 3 9.6 monomer ml/min 0.110 0.110 0.250 0.250 0.033 volume/min

TABLE-US-00004 TABLE 1D Process parameters and coating properties for coatings formed from PFAC8 Monomer: PFAC8 PW processes CW Parameter Units 8 9 10 11 12 13 14 Thickness (d) Si nm 798 1627 2023 969 1194 5258 2250 Thickness (d) SB nm 1035 1466 1624 1053 962 5142 2620 density (ρ) g .Math. cm−3 2.69 2.54 2 Δρ from g .Math. cm−3 1.09 0.94 0.4 monomer RMS roughness nm 65±05 50±10 80±10 ΔZ nm 100±50  175±50  150±50  Topography ΔZ/d by AFM 0.13 0.09 0.13 CF3/C═O on SB 0.2 0.18 0.19 0.22 0.23 0.14 0.10 R at 8 V 13 min Ω 6.00E±07 2.30E±08 6.20E±08 3.80E±07 7.40E±06 5.40E±07 1.44E±10 R/d (13 min) Ω/nm 5.80E±04 1.57E±05 3.82E±05 3.61E±04 7.69E±03 1.05E±04 5.50E±06 Critical force g 36 95 98 134 169 >1000 >1000

TABLE-US-00005 TABLE 2 Example of optical properties of coatings Wavenumber of 438.5 632.8 incident light (nm) Refractive index (n) 1.3461 1.3372 Optical constant (k) 0.0003 0.0001

TABLE-US-00006 TABLE 3 Configuration requirements for thickness measurements (F20 UV) Thickness range Thickness when F20 UV range measuring n and k Precision.sup.1 1 nm-40 um 50 nm and up 0.2 nm .sup.1Standard deviation of 100 thickness readings of 500 nm SiO.sub.2 film on silicon substrate

TABLE-US-00007 TABLE 4 Band assignments and integration limits Wavenumber (cm-1) 1730 1335 Assignment C═O CF3 (s) Integration limits 1840-1630 cm-1 1357-1309 cm-1

TABLE-US-00008 TABLE 5 Monomer and coating densities (measured by XRR for PFAC8 coatings) and by gravimetric analysis for Parylene C Monomer Coating density Monomer Density (g/cc) (g/cc) (I) PFAC8 1.63 1.9 present invention method (II) Parylene C 1.23 1.29 (III) PFAC8 1.63 1.2 prior art method

TABLE-US-00009 TABLE 6 Integration limits for the calculation of ATR ratios of different perfluoro acrylate monomers and the corresponding polymers. Assignment C═O (s) CF3 (s) Integration PFAC8 1840-1640 cm-1 1357-1309 cm-1 limits PFAC10 1840-1640 cm-1 1362-1314 cm-1 PFAC6 1840-1640 cm-1 1376-1329 cm-1 PFAC4 1840-1640 cm-1 1376-1322 cm-1

TABLE-US-00010 TABLE 7 ATR features of different PFAC.sub.n polymers Spectral areas and peak positions (cm.sup.−1) polymers 1330-1355 1080-1090 980-1020 840-900 PFAC10 Single peak Strong peak Single peak strong doublet 1345 cm.sup.−1 1085 cm.sup.−1 shoulder 990 cm .sup.−1 888-900 cm .sup.−1 PFAC8 Doublet Weak peak Single with Weak doublet 1333-1343 1085 cm .sup.−1 shoulder 880-827 cm.sup.−1 cm.sup.−1 980 cm .sup.−1 PFAC6 doublet Weak peak Weak doublet Strong doublet 1351-1364 1081 cm .sup.−1 1010-1020 cm.sup.−1 845-808 cm.sup.−1 cm.sup.−1 PFAC4 Single Very weak shoulder Strong strong peak peak doubled with Single peak 1353 cm.sup.−1 1079 cm .sup.−1 1021 cm.sup.−1 880 cm.sup.−1

TABLE-US-00011 TABLE 8 Integration limits for the calculation of ATR ratios of different perfluoro meth acrylate monomers and the corresponding polymers. Assignment C═O (s) CF3 (s) Integration PFMAC8 1840-1640 cm-1 1359-1309 cm-1 limits PFMAC10 1840-1640 cm-1 1362-1314 cm-1 PFMAC6 1840-1640 cm-1 1376-1329 cm-1 PFMAC4 1840-1640 cm-1 1376-1322 cm-1

TABLE-US-00012 TABLE 9 Properties of CVD prepared Parylene coatings Parylene C Parameter units Thickness (d) Si nm 1200 1500 2850 Thickness (d) SB nm 1200 1500 2850 density* (p) g .Math. cm-3 1.289 1.289 1.289 Δp from monomer g .Math. cm-3 0.06 0.06 0.06 RMS roughness nm 5.2 ± 1 ΔZ nm 30 Topography ΔZ/d by AFM 0.025 CF3/C═O on SB N/A R at 8 V 13 min Ω 1.03E−05 1.14E−06 2.01E−07 R/d (13 min) Ω/nm 8.61E+01 7.62E+02 7.04E+03 Critical force g 28 ± 5 g 30 ± 5 g >250 g

TABLE-US-00013 TABLE 10 process parameters and coating properties for coatings formed from iso decyl acrylate Parameter Monomer units IDA Process Sample No 1 2 3 4 5 6 7 8 CW time min 1 1 1 1 1 Ton μs 37 37 37 37 37 Toff ms 0.1 0.1 0.1 0.1 0.1 monomer pressure mtorr 60 60 60 60 80 CW Power 50 50 50 120 50 PW power Watts 80 80 50 120 80 flow rate sccm 4.0 4.0 4.0 4.0 4.0 Chamber T ° C. 45 45 45 45 45 PW time min 10 25 30 20 20 power/volume Watts/litre 32 32 20 48 32 power/flow Watts/sccm) 20 20 12 30 20 monomer volume/min ml/min 0.040 0.040 0.040 0.040 0.040 monomer use g 0.4 0.9 1.1 0.7 0.7 Coating Thickness nm 408 462 1033 1093 1861 850 850 643 CH3/C═O 0.3 0.3 0.29 29 0.18 0.38 0.37 0.27 performance Resistance at 8 V Ω 1.34E ±06 4.99E ±04 8.20E ±06 1.80E ±07 1.39E ±10 1.80E ±04 8.00E ±04 4.90E ±07 13 min

TABLE-US-00014 TABLE 11 Integration limits for the calculation of ATR ratios of different non fluorinated monomers and the corresponding polymers. Assignment C═O (s) CF3 (s) Integration Iso Decyl Acrylate 1845-1630 cm-1 1410-1326 cm-1 limits Dodecyl Acrylate 1845-1630 cm-1 1410-1319 cm-1 Hexyl Acrylate 1845-1630 cm-1 1410-1320 cm-1 Ethyl Hexyl 1845-1630 cm-1 1410-1320 cm-1 Acrylate

TABLE-US-00015 TABLE 12 process parameters for forming coatings from Vinyl Decanoate and resultant properties of the coating Parameters Units Value CW time min 2 Ton μs 37 Toff ms 0.5 monomer pressure mtorr 70 PW/CW power Watts 50 monomer flow rate sccm 2 (STP) Chamber T ° C. 45 PW time min 40 power/volume Watts/litre 20 power/flow Watts/sccm 25 Resistance Ohms 2.3 × 10.sup.8 Monomer vol./min ml/min 0.018 Thickness nm 2150 ATR CH3/C═O ml/min 0.20