METHOD OF FORMING A PROTECTED CONNECTION AND CONNECTOR COMPRISING SAID CONNECTION

Abstract

A method of forming a protected connection between a first connecting element, optionally mounted on a support (202), and a second connecting element, the method comprising: (i) depositing a protective material (210) on the first connecting element and/or on the support; (ii) optionally depositing an overlying coating (212) on the protective material; and (iii) pushing the second connecting element and establishing a connection between the first connecting element and the second connecting element, the connection being protected by the protective material.

Claims

1. A method of forming a protected connection between a first connecting element, optionally mounted on a support, and a second connecting element, the method comprising: (i) depositing a protective material on the first connecting element and/or on the support; (ii) optionally depositing an overlying coating on the protective material; and (iii) pushing the second connecting element and establishing a connection between the first connecting element and the second connecting element, the connection being protected by the protective material.

2. The method of claim 1, wherein step (iii) additionally comprises pushing the second connecting element into the protective material.

3. The method of claim 1 or 2, wherein step (iii) additionally comprises pushing the second connecting element through the overlying coating.

4. The method of any one of the preceding claims, wherein in step (i) the protective material is deposited on the first connecting element.

5. The method of any one of the preceding claims, wherein in step (iii) the second connecting element is pushed into the protective material, and optionally through the overlying coating, to establish a connection between the first connecting element and the second connecting element.

6. The method of any one of the preceding claims, wherein the support is a printed circuit board.

7. The method of any one of the preceding claims, the method comprising: (i) depositing a protective material on the first connecting element; (ii) optionally depositing an overlying coating on the protective material; and (iii) pushing the second connecting element into the protective material, and optionally through the overlying coating, to establish a connection between the first connecting element and the second connecting element, the connection being protected by the protective material.

8. The method of any one of the preceding claims, wherein the protective material is a self-healing material.

9. The method of any one of the preceding claims, wherein the protective material is a gel.

10. The method of any one of the preceding claims, wherein the protective material has a hardness value of less than 100 according to Shore OO hardness, as determined by ASTM D2240.

11. The method of any one of the preceding claims, wherein the protective material has a hardness value of 1 mm/10 or more according to the penetration hardness scale as determined by ISO 2137, 9.38 g hollow cone.

12. The method of any one of the preceding claims, wherein depositing the protective material comprises use of a base material, which optionally comprises silicone rubber, and a catalyst, which optionally comprises platinum.

13. The method of any one of the preceding claims, wherein depositing the protective material comprises curing, optionally UV curing and/or thermal curing.

14. The method of claim 12 or 13, wherein the viscosity of a mixture of the base material and the catalyst is from 100 cPs to 400,000 cPs.

15. The method of any one of the preceding claims, wherein the connection is an electrical connection.

16. The method of claim 15, wherein the first connecting element and the second connecting element constitute an electrical connector, and the electrical connector is selected from electrical connectors that include spring-type contacts, electrical connectors with contacts that comprise spring-loaded pins, plug-in type electrical connectors, contact pads, board-to-board (B2B) connectors, and zero insertion force (ZIF) connectors.

17. The method of any one of the preceding claims, wherein the method comprises step (ii) of depositing an overlying coating on the protective material.

18. The method of any one of the preceding claims, wherein depositing the overlying coating in step (ii) comprises forming a plasma deposited layer.

19. The method of claim 18, wherein depositing the overlying coating in step (ii) comprises exposing the protective material to a plasma comprising a monomer compound for a period of time sufficient to allow the overlying coating to form.

20. The method of claim 19, wherein the monomer compound is a compound of formula (I): ##STR00034## wherein each of R.sup.1, R.sup.2 and R.sup.4 is independently selected from hydrogen, halogen, optionally substituted branched or straight chain C.sub.1-C.sub.6 alkyl, optionally substituted C.sub.3-C.sub.8 cycloalkyl, optionally substituted C.sub.3-C.sub.12 aryl, and R.sup.3 is selected from: ##STR00035## wherein each X is independently selected from hydrogen, halogen, optionally substituted branched or straight chain C.sub.1-C.sub.6 alkyl, optionally substituted C.sub.3-C.sub.8 cycloalkyl, and optionally substituted C.sub.3-C.sub.12 aryl, and n is an integer from 1 to 27.

21. The method of claim 19 or 20, wherein the monomer compound is a compound of formula (Ia): ##STR00036## wherein each of R.sup.1, R.sup.2, R.sup.4, and R.sup.5 to R.sup.10 is independently selected from hydrogen and optionally substituted C.sub.1-C.sub.6 branched or straight chain alkyl; each X is independently selected from hydrogen and halogen; a is from 0 to 10; b is from 2 to 14; and c is 0 or 1; or wherein the monomer compound is a compound of formula (Ib): ##STR00037## wherein each of R.sup.1, R.sup.2, R.sup.4, and R.sup.5 to R.sup.10 is independently selected from hydrogen and optionally substituted C.sub.1-C.sub.6 branched or straight chain alkyl; each X is independently selected from hydrogen and halogen; a is from 0 to 10; b is from 2 to 14; and c is 0 or 1.

22. The method of claim 21, wherein a and c are each independently 0 or 1; and b is from 3 to 7.

23. The method of any one of claims 20 to 22, wherein each X is F.

24. The method of any one of claims 20 to 23, wherein each of R.sup.1, R.sup.2 and R.sup.4 is independently selected from hydrogen and methyl.

25. The method of claim 24, wherein each of R.sup.1, R.sup.2 and R.sup.4 is hydrogen.

26. The method of any one of claims 21 to 25, wherein each of R.sup.5 to R.sup.10 is independently selected from hydrogen and methyl.

27. The method of claim 26, wherein each of R.sup.5 to R.sup.10 is hydrogen.

28. The method of any one of claims 20 to 27, wherein the monomer compound is a compound of formula (Ic): ##STR00038## wherein m is from 1 to 10.

29. The method of claim 28, wherein the compound of formula (Ic) 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).

30. The method of any one of claims 20 to 27, wherein the monomer compound is a compound of formula (Id): ##STR00039## wherein m is from 1 to 10.

31. The method of claim 30, wherein the compound of formula (Id) is selected from 1H,1H,2H,2H-perfluorohexyl methacrylate (PFMAC4), 1H,1H,2H,2H-perfluorooctyl methacrylate (PFMAC6) and 1H,1H,2H,2H-perfluorodecyl methacrylate (PFMAC8).

32. The method of any one of claims 19 to 31, wherein in step (ii), the protective material is exposed to a plasma comprising the monomer compound and a crosslinking reagent.

33. The method of claim 32, wherein the crosslinking reagent comprises two or more unsaturated bonds attached by means of one or more linker moieties.

34. The method of claim 32 or 33, wherein the crosslinking reagent has a boiling point of less than 500 C. at standard pressure.

35. The method of any one of claims 32 to 34, wherein the crosslinking reagent is independently selected from a compound of formula (II) or (III): ##STR00040## wherein Y.sup.1, Y.sup.2, Y.sup.3, Y.sup.4, Y.sup.5, Y.sup.6, Y.sup.7 and Y.sup.8 are each independently selected from hydrogen, optionally substituted branched or straight chain C.sub.1-C.sub.6 alkyl, optionally substituted C.sub.1-C.sub.6 cycloalkyl, and optionally substituted C.sub.1-C.sub.6 aryl; and L is a linker moiety.

36. The method of claim 35, wherein for the compound of formula (II), group L has the formula: ##STR00041## wherein each Y.sup.9 is independently selected from a bond, O, OC(O), C(O)O, Y.sup.11OC(O), C(O)OY.sup.11, OY.sup.11, and Y.sup.11O, wherein Y.sup.11 is an optionally substituted branched, straight chain or cyclic C.sub.1-C.sub.8 alkylene; and Y.sup.10 is selected from an optionally substituted branched, straight chain or cyclic C.sub.1-C.sub.8 alkylene and a siloxane group.

37. The method of any one of claims 32 to 36, wherein the crosslinking reagent is independently selected from divinyl adipate (DVA), 1,4-butanediol divinyl ether (BDVE), 1,4-cyclohexanedimethanol divinyl ether (CDDE), 1,7-octadiene (17OD), 1,2,4-trivinylcyclohexane (TVCH), 1,3-divinyltetramethyldisiloxane (DVTMDS), diallyl 1,4-cyclohexanedicarboxylate (DCHD), 1,6-divinylperfluorohexane (DVPFH), 1H,1H,6H,6H-perfluorohexanediol diacrylate (PFHDA) and glyoxal bis(diallyl acetal) (GBDA).

38. The method of claim 37, wherein the crosslinking reagent is divinyl adipate (DVA).

39. The method of any one of claims 35 to 38, wherein for the compound of formula (III), group L is selected from a branched or straight chain C.sub.1-C.sub.8 alkylene or an ether group.

40. The method of any one of claims 32 to 39, wherein in step (ii), the monomer compound and the crosslinking reagent are introduced to a plasma deposition chamber in the liquid phase and the volumetric ratio of the crosslinking reagent to the monomer compound is from 1:99 to 20:80.

41. The method of claim 40, wherein in step (ii) the volumetric ratio of the crosslinking reagent to the monomer compound is from 5:95 to 15:85.

42. The method of any one of claims 32 to 41, wherein in step (ii), the monomer compound and the crosslinking reagent are introduced to a plasma deposition chamber and the molar input flow ratio of the crosslinking reagent to the monomer compound is from 1:20 to 1:1.

43. The method of claim 42, wherein in step (ii) the molar input flow ratio of the crosslinking reagent to the monomer compound is from 1:14 to 1:6.

44. The method of any one of the preceding claims, wherein the protective material has a thickness of from 0.1 mm to 5 mm.

45. The method of any one of the preceding claims, wherein the overlying coating layer has a thickness of from 250 nm to 10000 nm.

46. The method of any one of the preceding claims, wherein the method further comprises depositing one or more additional coating layers.

47. The method of any one of the preceding claims, wherein the second connecting element is not coated.

48. The method of any one of claims 1 to 47, wherein the method further comprises depositing the protective material, and optionally the overlying coating, on the second connecting element before making the connection in step (iii).

49. The method of any one of the preceding claims, wherein making the connection between the first connecting element and the second connecting element in step (iii) involves punching the protective material, and optionally the overlying coating, prior to making the connection.

50. A protected connection obtainable by the method according to any one of claims 1 to 49.

51. A connector comprising a first connecting element and a second connecting element forming a connection, the connection being protected by a dot of protective material bearing an overlying coating, optionally wherein a portion of the protective material is interposed between the connecting elements.

52. The connector of claim 51, which is an electrical connector.

53. The connector of claim 52, wherein the connector is selected from the electrical connectors defined in claim 10.

54. The connector of any one of claims 51 to 53, wherein the protective material is as defined in any one of claim 8 to 11 or 44.

55. The connector of any one of claims 51 to 54, wherein the protective material is obtainable by deposition as defined in any one of claims 1 or 7 to 14.

56. The connector of any one of claims 51 to 55, wherein the overlying coating comprises a plasma deposited layer.

57. The connector of any one of claims 51 to 56, wherein the overlying coating is obtainable by deposition as defined in any one of claims 18 to 43.

58. The connector of any one of claims 51 to 57, wherein the overlying coating is as defined in claim 45.

Description

[0195] One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0196] FIG. 1 shows electrical test apparatus for determining the resistance of a coating.

[0197] FIG. 2 shows schematic examples of a protective material (in the form of a gel blister) dispensed over (a) a contact pad and (b) a spring connector.

[0198] FIG. 3 shows schematic diagrams of (a) a plan view of a board-to-board socket (or header) surrounded by protective material and (b) a side view of a board-to-board socket (or header) surrounded by protective material, after plasma coating.

[0199] FIG. 4 shows a schematic diagram of the process of applying a protective material and a plasma coating to a ZIF connector, then inserting the cable through the protective material and plasma coating to make an electrical connection.

EXAMPLES

[0200] Plasma Deposition Process

[0201] Plasma polymerization experiments were carried out in a metallic reaction chamber with a working volume of 22 litres. The chamber consisted of two parts, a shallow cuboid cavity with a single open face, oriented vertically, which was sealed to a solid metallic door via a Viton O ring on the outer edge. All surfaces were heated to 37 C. Inside the chamber was a single perforated metal electrode, area per the open face of the cavity, also oriented vertically and attached via connections at the corners to the door, fed by an RF power unit via a connection through the centre of the metallic door. For pulsed plasma deposition the RF power unit was controlled by a pulse generator.

[0202] The rear of the chamber was connected via a larger cavity, achieving a total volume of 125 L, to a metal pump line, pressure controlling valve, a compressed dry air supply and a vacuum pump. The door of the chamber comprised several cylindrical ports for connection to pressure gauges, monomer delivery valves (inner surfaces of which were heated to 70 C.), temperature controls and gas feed lines which were in turn connected to mass flow controllers.

[0203] In each experiment a sample was positioned vertically on nylon pegs attached to the perforated electrode, facing the door.

[0204] The reactor was evacuated down to base pressure (typically <10 mTorr). Process gas was delivered into the chamber using the mass flow controllers, with typical gas flow values being between 2-25 sccm. The monomer was delivered into the chamber, with typical monomer gas flow values being between 5-60 sccm. The chamber was heated to 37 C. The pressure inside the reactor was maintained at between 20-30 mTorr. The plasma was produced using RF at 13.56 MHz. The process usually contains at least the steps of a continuous wave (CW) plasma and a pulsed wave (PW) plasma. Optionally, these steps can be proceeded by an initial activation step using a continuous wave (CW) plasma. The activation CW plasma, if used, was for 1 minute, the CW plasma was for 1 or 4 minutes and the duration of the PW plasma varied in different experiments. The peak power setting was 160 W in each case, and the pulse conditions were time on (t.sub.on)=37 s and time off (t.sub.off)=10 ms. At the end of the deposition the RF power was switched off, the monomer delivery valves stopped and the chamber pumped down to base pressure. The chamber was the vented to atmospheric pressure and the coated samples removed.

[0205] For each experiment, 4-6 test printed circuit boards (PCBs) and accompanying 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.

[0206] Analytical Methods

[0207] A number of properties of exemplary coated surfaces formed according to the invention were investigated, using the following methods.

[0208] Resistance in Tap Water

[0209] 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.

[0210] FIG. 1 shows an electrical test apparatus 100. The coated PCB 110 to be tested is placed into a beaker 112 of water 114 and connected to a power source (not shown) via connections 116,118. The coated PCB 110 is centred horizontally and vertically in the beaker 112 to minimise effects of local ion concentration (vertical location of the coated PCB 110 is very important; water 114 level should be to the blue indicator line 120). When the coated PCB 110 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 coated PCB 110 is held at the set voltage for 13 minutes, with the current being monitored continuously during this period.

[0211] The coatings formed by the different process parameters are tested. It has been found that when coatings have resistance values higher than 10 MOhms, the coated device will successfully pass 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).

[0212] Resistance in Salt Water

[0213] This test method is identical to the method described above for Resistance in tap water, except that salt water is used instead of tap water. The composition of the salt water is 5% w/v NaCl, i.e. 5 g NaCl per 100 ml water.

[0214] Coating Thickness

[0215] The thickness of the coatings formed was measured using spectroscopic reflectometry apparatus (Filmetrics F20-UV) using optical constants verified by spectroscopic elipsometry.

[0216] Spectroscopic Ellipsometry

[0217] 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 and phase difference . A broad band light source is used to measure this variation over a range of wavelengths and the standard values of and 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 and values, such as film thickness and refractive index.

[0218] 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 and . To extract parameters of interest, such as thickness or optical constants, a model has to be set up to allow theoretical calculation of and . 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.

[0219] Spectroscopy Reflectrometry

[0220] 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.

[0221] 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.

[0222] Alternative techniques for measuring thickness are stylus profilometry and coating cross sections measured by SEM.

[0223] Monomer Compound

[0224] The monomer compound used in these examples was PFAC6, i.e. 1H,1H,2H,2H-perfluorooctylacrylate (CAS #17527-29-6) of formula:

##STR00032##

[0225] Crosslinking Agent

[0226] The crosslinking agent used in these examples was divinyl adipate (DVA) (CAS #4074-90-2) of formula:

##STR00033##

Example AFormation of Plasma Coating

[0227] A 2500 nm thick coating is deposited onto printed circuit boards (PCBs) and accompanying Si wafers in a gas phase plasma deposition process as described above, using a perfluorinated acrylate monomer, PFAC6, and a cross-linker, DVA, which were introduced to the plasma deposition chamber in the liquid phase, pre-mixed at the volumetric ratio 9:1.

[0228] The barrier performance of the coating on the PCBs is tested via the tests described above and the results are shown in Table 2.

TABLE-US-00002 TABLE 2 Performance of the plasma deposited coating Resistance in tap water >10 MOhms (8 V, ) Average from all samples Resistance in 5% salt water >10 MOhms (8 V, ) Only one sample

Example 1Using a Self-Healing Gel to Protect a Spring Connector

[0229] A self-healing gel is dispensed on an area of a printed circuit board (PCB) where an electrical connection needs to be made, for example a spring connector or a contact pad. Dispense of the gel can be manual or automated. The gel can be dispensed as one or more discrete units. The dimensions of a unit once dispensed can be around 2.5 mm in width and 1 mm in height.

[0230] The self-healing gel is a silicone rubber. The base material (before curing) is a silicone rubber blend. The catalyst contains a platinum additive.

[0231] The self-healing gel has the following properties: [0232] Base material viscosity before cure: 55,000 cPs at 25 C. [0233] Catalyst viscosity before cure: 1,000 cPs at 20 C. [0234] Mixed viscosity before cure: 42,000 cPs at 23 C. [0235] Mix ratio: 10:1 base material: catalyst by volume [0236] Curing mechanism: UV curable with broadband UV source [0237] Penetration hardness after cure (ISO 2137, 9.38 g hollow cone): 70 mm/10 [0238] Dielectric strength: >23 kV

[0239] The gel is cured under a 365 nm UV LED (cure time 19 s, distance 10 mm) and then treated with a fluoropolymer plasma deposited coating as described in Example A.

[0240] After the fluoropolymer treatment, the gel can be punched prior to reassembly using a spring-loaded punch at defined speed and diameter to ensure that the contact can push through the gel.

[0241] FIG. 2 (a) shows a schematic example of a PCB 202 having a contact pad 220 for connection with a component 204 having a spring connector 230. In this example, gel 210 is dispensed over the contact pad 220 such that the contact pad 220 is completely encased within the gel 210. A fluoropolymer coating 212 is subsequently deposited over the PCB 202 and the gel 210. As the component 204 is brought towards the PCB 202 to make a connection, a contact portion 232 of the spring connector 230 comes into contact with the fluoropolymer coating 212. The gel 210 under the fluoropolymer coating 212 acts as a cushion, thereby making the fluoropolymer layer 212 brittle. The contact portion 232 of spring connector 230 is therefore able to break through the brittle fluoropolymer layer 212 and engage with the contact pad 210 within the gel 210.

[0242] FIG. 2(b) shows a schematic diagram of a PCB having a spring connector 230 for connection with a component 204 having a contact pad 220. In this example, gel 210 is dispensed over the spring connector 230, such that a contact portion 232 of the spring connector 230 is completely encased within the gel 210. A fluoropolymer coating 212 is subsequently deposited over the PCB 202, part of the spring connector 230, and the gel 210. The gel 210 acts as a mask, thereby preventing coating of the contact portion 232 of the spring connector 230 by the fluoropolymer.

[0243] As the component 204 is brought towards the PCB 202 to make a connection, the gel 210 under the fluoropolymer coating 212 acts as a cushion and allows the contact pad 220 to push through the brittle fluoropolymer layer 212. No demasking step is required and the contact pin 232 and pad 220 is protected from corrosion by the self-healing gel 210.

[0244] Alternatively, a separate tool may be used to break the a hole in the fluoropolymer layer 212 in a preliminary step prior to bringing the component 204 towards the PCB 202 to make a connection.

Example 2Using a Self-Healing Gel to Protect a Board-to-Board Connector

[0245] A self-healing gel is dispensed on an area of a printed circuit board (PCB) where an electrical connection needs to be made, for example around the perimeter of either the socket or header of a board-to-board connector pair. Dispense of the gel can be manual or automated and the thickness of the gel should be greater than the height of the component. The exact quantity of gel depends on the dimensions and layout of the board to board connector but there must be enough gel to cover and protect the outside terminals on the untreated connector, when the connectors are paired. The gel may be applied such that there is a gap between the board to board connector and gel. The gel may be applied only to those sides of the board to board connector that have exposed terminals.

[0246] The self-healing gel is a silicone rubber. The base material (before curing) is a silicone rubber blend. The catalyst contains a platinum additive.

[0247] The self-healing gel has the following properties: [0248] Base material viscosity before cure: 55,000 cPs at 25 C. [0249] Catalyst viscosity before cure: 1,000 cPs at 20 C. [0250] Mixed viscosity before cure: 42,000 cPs at 23 C. [0251] Mix ratio: 10:1 base material: catalyst by volume [0252] Curing mechanism: UV curable with broadband UV source [0253] Penetration hardness after cure (ISO 2137, 9.38 g hollow cone): 70 mm/10 [0254] Dielectric strength: >23 kV

[0255] Following dispense, the gel is cured under a 365 nm UV LED (cure time 19 s, distance 10 mm) then treated with a fluoropolymer plasma deposited coating as described in Example A.

[0256] The other connector does not need to be separately processed so the connecting pair can then be mated.

[0257] FIG. 3 shows schematic diagrams of (a) a plan view of a board-to-board socket 320 surrounded by gel 310 and (b) a side view of a board-to-board socket 320 surrounded by gel 310, after plasma coating to form a fluoropolymer plasma deposited coating 312. An (untreated) board-to-board header 322 is brought into contact with the board-to-board socket 320 and pushes through the fluoropolymer plasma deposited coating 312 to form a connection. Terminals 324, 326 on either side of the (untreated) board-to-board header 322 are protected by the gel 310 when the socket 320 and header 322 are paired. Alternatively, socket 320 may be a header and (untreated) header 322 may be a socket.

Example 3Using a Self-Healing Gel to Protect a ZIF Connector

[0258] A self-healing gel is dispensed on an area of a printed circuit board (PCB) where an electrical connection needs to be made, for example over a ZIF connector. Dispense of the gel can be manual or automated and the quantity of gel depends on the dimensions and layout of the ZIF connector. There must be enough gel to ensure the terminals on the inserted ZIF jumper cable are fully submerged and protected.

[0259] The self-healing gel is a silicone rubber. The base material (before curing) is a silicone rubber blend. The catalyst contains a platinum additive.

[0260] The self-healing gel has the following properties: [0261] Base material viscosity before cure: 55,000 cPs at 25 C. [0262] Catalyst viscosity before cure: 1,000 cPs at 20 C. [0263] Mixed viscosity before cure: 42,000 cPs at 23 C. [0264] Mix ratio: 10:1 base material: catalyst by volume [0265] Curing mechanism: UV curable with broadband UV source [0266] Penetration hardness after cure (ISO 2137, 9.38 g hollow cone): 70 mm/10 [0267] Dielectric strength: >23 kV

[0268] Following dispense, the gel is cured under a 365 nm UV LED (cure time 19 s, distance 10 mm) then treated with a fluoropolymer plasma deposited coating as described in Example A.

[0269] The ZIF cable does not need to be separately processed and can be inserted, through the gel, into the ZIF connector and the lever closed.

[0270] FIG. 4 shows a schematic diagram of the process of applying a gel and a plasma coating to a ZIF connector, then inserting the cable through the gel and plasma coating to make an electrical connection. In more detail, referring to FIG. 4(a), gel 410 is dispensed over a portion of a ZIF connector 420 on a PCB 402, the ZIF connector 420 having its lever 422 in the down (closed) position. A fluoropolymer coating 412 is subsequently deposited over the PCB 402, gel 410 and portion of the ZIF connector 420 not having gel 410 dispensed thereon, as shown in FIG. 4(b). The lever 422 is then moved into the up (open) position and a ZIF cable 430 inserted through the brittle fluoropolymer coating 412, and through the gel 410 into the ZIF connector 420, as shown in FIG. 4(c). Referring to FIG. 4(d), the lever 422 is returned to the down (closed) position to lock the ZIF cable 430 in the ZIF connector 420.

[0271] Gel 410 may be dispensed over a portion of a ZIF connector 420 when its lever 422 is in the up (open) position.