System and Method for Uniform Pressure Gang Bonding

Abstract

A uniform pressure gang bonding device and fabrication method are presented using an expandable upper chamber with an elastic surface. Typically, the elastic surface is an elastomer material having a Young's modulus in a range of 40 to 1000 kilo-Pascal (kPA). After depositing a plurality of components overlying a substrate top surface, the substrate is positioned over the lower plate, with the top surface underlying and adjacent (in close proximity) to the elastic surface. The method creates a positive upper chamber medium pressure differential in the expandable upper chamber, causing the elastic surface to deform. For example, the positive upper chamber medium pressure differential may be in the range of 0.05 atmospheres (atm) and 10 atm. Typically, the elastic surface deforms between 0.5 millimeters (mm) and 20 mm, in response to the positive upper chamber medium pressure differential.

Claims

1. A uniform pressure, electronic component gang bonding device comprising: a lower plate having a top surface to accept a substrate; a heating unit underlying the lower plate top surface; an expandable upper chamber comprising: an orifice to accept a pressurized upper chamber medium; and, an elastic surface overlying the lower plate top surface, deformable in response to the pressurized medium.

2. The bonding device of claim 1 wherein the elastic surface deforms in a direction towards the lower plate top surface in response to an increase in upper chamber medium pressure.

3. The bonding device of claim 2 wherein the lower plate occupies an environment with an ambient atmospheric pressure; and, wherein the elastic surface deforms in a direction towards the lower plate top surface in response to an upper chamber medium pressure greater than the ambient atmospheric pressure.

4. The bonding device of claim 3 further comprising: an environmental control lower chamber comprising: an orifice accepting a lower chamber gas medium selected from the group consisting of ambient air, an inert gas, a forming gas, formic acid, and combinations thereof; and, wherein the lower plate top surface occupies the environmental control lower chamber and is exposed to the lower chamber gas medium.

5. The bonding device of claim 4 wherein the environmental control lower chamber is an ambient control lower chamber comprising: a seal formed from the upper chamber elastic surface; the orifice accepting the lower chamber gas medium; wherein the lower plate occupies the ambient control lower chamber; and, wherein the elastic surface deforms in a direction towards the lower plate top surface in response to an upper chamber medium pressure greater than the lower chamber gas medium pressure.

6. The bonding device of claim 5 wherein the ambient control lower chamber gas medium is selected from a group consisting of a vacuum, a partial vacuum, ambient air, an inert gas, a forming gas, formic acid, and combinations thereof.

7. The bonding device of claim 1 wherein the upper chamber medium is selected from the group consisting of a gas or a liquid.

8. The bonding device of claim 1 wherein the elastic surface is an elastomer material having a Young's modulus in a range of 40 to 1000 kilo-Pascal (kPA).

9. The bonding device of claim 1 further comprising: a substrate overlying the lower plate top surface, having a top surface with a plurality of electrical interfaces; a plurality of components overlying the substrate top surface, each component having electrical contacts overlying corresponding electrical interfaces on the substrate top surface; and, wherein the component electrical contacts are bonded to the substrate electrical interfaces in response to heating the substrate and the elastic surface compressing the components into the substrate top surface.

10. The bonding device of claim 9 wherein the elastic surface creates a uniform pressure on the plurality of components.

11. The bonding device of claim 1 further comprising: a coarse positioning mechanism for changing the distance between the lower plate top surface and the elastic surface.

12. The bonding device of claim 1 wherein the expandable upper chamber further comprises: a rigid top surface overlying the elastic surface; and, rigid sidewalls connecting the rigid top surface to the elastic surface.

13. The bonding device of claim 1 wherein the elastic surface is deformable in a range between 0.05 millimeters (mm) and 20 mm, in response to the pressurized medium.

14. The bonding device of claim 1 wherein the elastic surface is deformable in response to a pressure differential in a range of 0.5 atmospheres (atm) and 10 atm.

15. The bonding device of claim 3 wherein the elastic surface has a first surface area; wherein the substrate top surface has a second surface area greater than the first surface area; and, the bonding device further comprising: a traversing mechanism for changing the relative overlying orientation of the elastic surface with respect to the substrate top surface.

16. A uniform pressure gang bonding method comprising: providing a lower plate and an expandable upper chamber with an elastic surface; depositing a plurality of components overlying a substrate top surface; positioning the substrate overlying the lower plate, with the substrate top surface underlying and adjacent to the elastic surface; creating a positive upper chamber medium pressure differential in the expandable upper chamber; deforming the elastic surface; and, in response to deforming the elastic surface, applying a uniform pressure on the plurality of components.

17. The method of claim 16 further comprising: simultaneous with applying the uniform pressure, heating the substrate; and, in response to the uniform pressure and heat, bonding the components to the substrate top surface.

18. The method of claim 17 wherein depositing the plurality of components overlying the substrate top surface includes depositing semiconductor devices with electrical contacts overlying corresponding electrical interfaces on the substrate top surface; and, wherein bonding the components to the substrate top surface includes solder bonding the semiconductor device electrical contacts to the substrate electrical interfaces.

19. The method of claim 16 wherein positioning the substrate top surface underlying and adjacent to the elastic surface includes the substrate top surface occupying an environment with an ambient atmospheric pressure; wherein creating the positive upper chamber medium pressure differential in the expandable upper chamber includes creating an upper chamber pressure greater than the ambient atmospheric pressure; and, wherein deforming the elastic surface includes deforming the elastic surface in a direction towards the substrate top surface.

20. The method of claim 19 wherein positioning the substrate top surface underlying and adjacent to the elastic surface includes the substrate top surface occupying an environmental control lower chamber with an ambient atmospheric pressure and controlled type of gas medium selected from the group consisting of ambient air, an inert gas, a forming gas, formic acid, and combinations thereof.

21. The method of claim 16 wherein positioning the substrate top surface underlying and adjacent to the elastic surface includes the substrate top surface occupying an ambient control lower chamber, with a seal formed by the elastic surface of the expandable upper chamber; wherein creating the positive upper chamber medium pressure differential in the expandable upper chamber includes creating an upper chamber pressure in the expandable upper chamber greater than the pressure in the ambient control lower chamber; and, wherein deforming the elastic surface includes deforming the elastic surface in a direction towards the substrate top surface.

22. The method of claim 21 wherein creating the pressure in the expandable upper chamber greater than the pressure in the ambient control lower chamber includes creating a pressure in the ambient control lower chamber using a medium selected from the group consisting of a vacuum, a partial vacuum, ambient air, an inert gas, a forming gas, formic acid, and combinations thereof.

23. The method of claim 16 wherein creating the positive upper chamber medium pressure differential in the expandable upper chamber includes creating an upper chamber pressure using a medium selected from the group consisting of a gas or a liquid.

24. The method of claim 16 wherein providing the expandable upper chamber with an elastic surface includes providing an elastic surface made from an elastomer material having a Young's modulus in a range of 40 to 1000 kilo-Pascal (kPA).

25. The method of claim 16 wherein depositing the plurality of components overlying the substrate top surface includes depositing first components having a first profile height and depositing second components having a second profile height, different than the first profile height; and, wherein applying the uniform pressure on the plurality of components includes applying a uniform first pressure on both the first and second components.

26. The method of claim 25 wherein applying the uniform first pressure on the first and second components includes applying a pressure with difference of less than or equal to 5 kPA for a difference in profile height of up to 100 microns.

27. The method of claim 16 wherein deforming the elastic surface includes deforming the elastic surface in a range between 0.05 millimeters (mm) and 20 mm, in response to the positive upper chamber medium pressure differential.

28. The method of claim 16 wherein creating the positive upper chamber medium pressure differential includes creating a pressure differential in a range of 0.5 atmospheres (atm) and 10 atm.

29. The method of claim 17 wherein providing the elastic surface includes supplying an elastic surface having a first surface area; wherein depositing the plurality of components overlying the substrate top surface includes depositing components over a substrate top surface having a second surface area greater than the first surface area; the method further comprising: subsequent to bonding a first group of components to the substrate top surface, changing the relative overlying orientation of the elastic surface with respect to the substrate top surface; and, repeating the steps required for bonding a second group of components.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1 is a partial cross-sectional view of a surface mount emissive element (prior art, U.S. Pat. No. 9,825,202).

[0027] FIG. 2 is a schematic view of an emission substrate enabled with a first plurality of active matrix (AM) drive circuits (prior art).

[0028] FIGS. 3A and 3B illustrate fabrication steps comparing conventional TCB bonding of FIG. 3A with 2-step gang bonding of FIG. 3B (prior art).

[0029] FIG. 4 is a diagram depicting the application of uniform pressure onto chips with various thicknesses using hydrostatic pressure (prior art).

[0030] FIGS. 5A and 5B are a partial cross-sectional view of a uniform pressure, electronic component gang bonding device.

[0031] FIGS. 6A and 6B are partial cross-sectional views depicting variations in the gang bonding device.

[0032] FIGS. 7A and 7B are partial cross-section views of the gang bonding device after the creation of a positive upper chamber medium pressure differential.

[0033] FIG. 8 is a force diagram depicting a conventional gang bonding apparatus (prior art).

[0034] FIG. 9 is a force diagram for the gang bonding device described herein.

[0035] FIG. 10 is a flowchart illustrating a method for uniform pressure gang bonding.

[0036] FIG. 11 is a partial cross-sectional view of a gang bonding device incorporating a traversing mechanism.

DETAILED DESCRIPTION

[0037] FIGS. 5A and 5B are a partial cross-sectional view of a uniform pressure, electronic component gang bonding device. The gang bonding device 500 comprises a lower plate 502 having a top surface 504 to accept a substrate 506. The substrate 506 may be a printed circuit board (PCB), glass, or a silicon (Si) integrated circuit (IC). PCB substrates are used for conventional electronic package, while a glass substrate may be used for a mini-light emitting diode (mLED) or a micro-light emitting diode (LED) array or display, and a Si IC wafer may be used for a 3D IC package. A plurality of components 508 overlies the substrate top surface 510. The components 508 may be same or different type devices. A heating unit 512 typically underlies the lower plate top surface 504. However, the bonding device is not limited to any particular means of heating the substrate 506. An expandable upper chamber 514 comprises an orifice 516 to accept and supply a pressurized upper chamber medium. An elastic surface 518 overlies the lower plate top surface 504, deformable in response to the pressurized medium. The dotted lines indicate the position of the elastic surface prior to the creation of a positive upper chamber pressure differential. The upper chamber medium may be either a gas or a liquid.

[0038] The elastic surface 518 deforms in a direction towards the lower plate top surface 504 in response to an increase in upper chamber medium pressure. In one aspect as shown, the upper chamber 514 is enabled as an elastic sealed bag, in which case all the surfaces are elastic and they expand in response to a positive upper chamber pressure differential. However, the lower surface of the upper chamber bag may deform differently that the other bag surfaces. For example, the upper chamber bag upper surface may be made of a stiffer material that does not expand, or that expands less that the lower surface. Typically, the elastic surface 518 is an elastomer material having a Young's modulus in the range of 40 to 1000 kilo-Pascal (kPA). In one aspect, the elastic surface 518 is deformable in a range between 0.05 millimeters (mm) and 20 mm, in response to the upper chamber pressurized medium. It is also typical that the elastic surface 518 is deformable in response to a pressure differential in a range of 0.5 atmospheres (atm) and 10 atm.

[0039] Also shown in FIG. 5A, the lower plate 502 occupies an environment with an ambient atmospheric pressure, and the elastic surface 518 deforms (expands) in a direction towards the lower plate top surface in response to an upper chamber medium pressure greater than the ambient atmospheric pressure. That is, the substrate is not placed in a controlled pressure environment.

[0040] The gang bonding device of FIG. 5B depicts an ambient control lower chamber 520 comprising, in part, a seal formed from the upper chamber elastic surface and an orifice 522 accepting and supplying a lower chamber gas medium. The lower plate 502 occupies the ambient control lower chamber 520. Otherwise, the lower chamber 520 is an environmental control lower chamber, which includes the gas medium orifice 522, but the environmental control lower chamber is not sealed, leaving the lower plate exposed to the surrounding ambient atmospheric pressure, which is typically 1 atm. In either case, the elastic surface 518 deforms in a direction towards the lower plate top surface 504 in response to an upper chamber medium pressure greater than the lower chamber gas medium pressure. The lower chamber gas medium may be a vacuum, partial vacuum, ambient air, an inert gas, a forming gas, formic acid, and combinations thereof. FIG. 5B also depicts a coarse positioning mechanism 524 for changing the (vertical) distance between the lower plate 502 and the elastic surface 518. A coarse positioning mechanism can also be used in the gang bonding device variations depicted in FIGS. 5A, 6A, 6B, and 11.

[0041] FIGS. 6A and 6B are partial cross-sectional views depicting variations in the gang bonding device. In both figures the expandable upper chamber 514 further comprises a rigid top surface 600 overlying the elastic surface 518. Rigid sidewalls 602 connect the rigid top surface 600 to the elastic surface 518. Thus, in this case the elastic surface 518 is a film or membrane forming a seal along the bottom surface of the upper chamber 514. In FIG. 6A the lower plate 502 occupies an ambient control or environmental control lower chamber, as in FIG. 5B. In FIG. 6B, or in the case of the environmental control lower chamber of FIG. 6A, the lower plate 502 is simply located in an atmosphere of ambient air, inert gas, forming gas, formic acid, or a combination of these elements, with an ambient pressure (i.e., not sealed in a pressure controlled chamber).

[0042] FIGS. 7A and 7B are partial cross-section views of the gang bonding device after the creation of a positive upper chamber medium pressure differential. In FIG. 7A the substrate 506 overlies the lower plate top surface 504, and it has a top surface 510 with a plurality of electrical interfaces 700, which are more clearly seen in FIG. 6A. In this case, components 508 may be semiconductor devices overlying the substrate top surface 510, with each semiconductor device having electrical contacts 702 overlying corresponding electrical interfaces 700 on the substrate top surface 510. The semiconductor device electrical contacts 702 are bonded, typically solder bonded, to the substrate electrical interfaces 700 in response to heating the substrate 506 and the elastic surface 518 compressing the semiconductor devices 508 into the substrate top surface 510. The elastic surface 518 acts to create a uniform pressure on the plurality of semiconductor devices 508. In other aspects, device 500 can aid in the adhesive bonding of components to substrates, without the use of solder or without making electrical connections.

[0043] FIG. 7B depicts a substrate 506 such as might be used in the fluidic assembly of a micro-LED display. In this case the substrate top surface 510 includes wells 704, typically formed by etching the substrate top surface. LED component 508a occupies a first well, and includes a post or navigation keel 706 extending the LED above the plane 710 of the substrate top surface 510. LED component 508b occupies a second well and its upward facing surface 708 does not extend as far as the substrate top surface plane 710, so that the combination of the well and LED 508b create a concavity. Component 508c is formed on the substrate top surface. The elastic surface 518 is able to create a uniform pressure on all three components 508a, 508b, and 508c, despite the differences in profile height.

[0044] As shown in FIGS. 6A and 7A, the gang bonding tool 500 is composed of two chambers 514 and 520, and an elastomer membrane 518 separating the chambers. The lower chamber 520 is heated and the atmosphere can be controlled to facilitate the bonding process. The upper chamber 514 is used to introduce a gas or liquid pressure medium to deform the elastomer membrane. The product substrate 506 typically contains electrical wiring and bonding pads 700 with the chips 508 to be bonded already assembled, and it is placed in the lower chamber on a heated chuck 512. In FIGS. 6A and 7A, the heated chuck 512 is shown as located outside the lower chamber, but in some cases the heated chuck may be situated inside the lower chamber, as shown in FIG. 5B for example. In FIG. 6A, the chip electrodes 702 and substrate bonding pads 700 are shown purposely separated by a gap indicating that a bond has not yet been formed even though the two electrodes may be in physical contact. In some cases, solder paste may be placed between chip electrodes and substrate bonding pads.

[0045] FIG. 11 is a partial cross-sectional view of a gang bonding device incorporating a traversing mechanism. In this aspect the elastic surface 518 has a first surface area and the substrate top surface 510 has a second surface area greater than the first surface area. In this two-dimensional figure, the larger area of the substrate top surface 510 is represented by a greater length 1100 than the length 1102 of the elastic surface 518. The bonding device 500 further comprises a traversing mechanism, represented by arrow 1104, for changing the relative overlying orientation of the elastic surface 518 with respect to the substrate top surface 510. The traversing mechanism 1104 can be enabled by moving either the upper chamber 514 or lower plate 502, or both. Although not explicitly shown, the lower plate may occupy an environmental or ambient control lower chamber as described above.

[0046] An exemplary bonding process proceeds as follows. Please note that these steps may occur simultaneously or sequentially, and the step number does not necessarily imply the process sequence: [0047] 1. Ambient control. In some aspects, process bonding in an oxygen free environment is preferred, so the ambient environment can be inert gas, vacuum, or even a reducing environment. The common inert gases include argon (Ar) and nitrogen (N.sub.2). The reducing environment can be a forming gas (H.sub.2+N.sub.2 mixture), formic acid, or similar mixture. The pressure of lower chamber is denoted as P.sub.2 in FIG. 7A. [0048] 2. Pump pressure medium into top chamber to pressure P.sub.1. When the upper chamber pressure P.sub.1 is higher than the bottom chamber pressure P.sub.2, the elastomer membrane 518 is deformed pushing downward. At some pressure difference, the membrane 518 reaches the chips 508 and exerts a downward force to reduce the gap between the chip electrode 702 and substrate bonding pad 700. This mechanical contact between electrode and pad can also disrupt any surface oxides that may impede bonding. [0049] 3. Apply heat. Rapidly ramp up the heater to reach the eutectic bonding or solder bonding temperature so the chip electrodes 702 and the substrate bonding pads 700 begin to interact and fuse together. [0050] 4. Hold. Maintain temperature and pressure for a period of time to let chip electrodes 702 and the substrate bonding pads 700 form the desired intermetallic compound (IMC). [0051] 5. Cool. After forming the IMC layer that ensures strong bonding between chips and substrate, remove the pressure and cool down the system so the product substrate can be removed.

[0052] Initially, when the elastomer touches to the chip surface, the net force applied to the chip is the pressure difference (P.sub.1P.sub.2) times the chip surface area. When the chip electrode and substrate pad are in intimate contact, the force applied to the chip is higher than the initial condition. More importantly, the magnitude of the pressure applied to the chips is the same regardless of their thicknesses. Note that the force is pressure times the chip surface area, so the magnitude of force applied to the chips is the same if the chip area is the same.

[0053] P.sub.1 can be in the range of 100-1000 kPA and P.sub.2 in the range of 0.001-100 kPA.

[0054] The elastomer material can be polydimethylsiloxane PDMS with Young's modulus 40-1000 kPA.

[0055] The elastomer material may have a thickness of 0.1-10 mm. The system can have an upper chamber only, with the lower chamber at regular atmospheric conditions (FIGS. 5A, 6B, and 11), or with the lower chamber having environmental (gas medium) control, or with the lower chamber having ambient (gas medium and pressure) control (FIGS. 5B and 6A).

[0056] For a quick analysis of the force exerted on devices during bonding using the elastomer medium, one can assume that the deformation of the elastomer is small and the elastic material exhibits a linear elasticity that can be described by Hooke's law as a linear relationship between the stress and strain. Although Hooke's law only holds for materials under certain loading conditions, it is sufficient to analyze the pressure on devices during bonding. Hooke's law can be stated as a relationship between tensile (or compression) force F and corresponding extension displacement x,

F=k x,

[0057] where k is a constant known as the rate or spring constant. Furthermore, Hooke's law can also be stated as a relationship between stress o and strain

=E ,

[0058] where E is the elastic modulus or Young's modulus. Furthermore, strain is dimensionless, indicating the fractional change in length,

=L/L.

[0059] so the stress (for pressure, P) can be presented as

=F/A.

[0060] FIG. 8 is a force diagram depicting a conventional gang bonding apparatus (prior art). The forces exerted on different chips in the conventional gang bonding apparatus are shown. The thickness difference between Chip 1 and Chip 2 is exaggerated for a clearer description. The forces on Chip 1 and Chip 2 are:

F.sub.1=A.sub.1.sub.1=A.sub.1E.sub.1=A.sub.1E(y.sub.1/y)

F.sub.2=A.sub.2.sub.2=A.sub.2E.sub.2=A.sub.2E(y.sub.2/y)

[0061] The stresses on Chip 1 and Chip 2 are linearly proportional to the strain occurring in the elastic material directly above the chips. For this gang bonding set up, it can be seen that uniform stress is difficult to apply on all chips. The total force on the bonding head (F.sub.T) equals to the total forces applied to the chips (F.sub.1+F.sub.2+ . . . ).

[0062] FIG. 9 is a force diagram for the gang bonding device described herein. Focusing on the dotted-line box in the figure, F.sub.g (the gas force applied to the membrane with an area equal to the chip size) equals F.sub.3 (the force applied to the chip by the membrane), so the system is in balance. If F.sub.g is different from F.sub.3, the elastomer deforms until the forces are in balance. Therefore,

F.sub.g=F.sub.3=A.sub.3.sub.3=A.sub.3E.sub.3=A.sub.3E(y.sub.3/y)

[0063] Furthermore, Fg is the force applied on Chip 3 and it equals the gas pressure times the chip area, i.e.,

F.sub.g=PA.sub.3=A.sub.3.sub.3.fwdarw.P=.sub.3

[0064] Similarly,

F.sub.g=PA.sub.4=A.sub.4.sub.4.fwdarw.P=.sub.3=.sub.4

[0065] From this analysis, it is clear that the stress applied to each chip is the same regardless of the chip thickness. Alternatively stated, if two chips have the same surface area, then the force applied to each chip is the same regardless of the chip thicknesses. Again, the gang bonding device described herein provides a way to apply uniform stress (or pressure) on chips for group bonding or gang bonding applications.

[0066] In summary, the gang bonding apparatus provides a uniform pressure onto many chips regardless of the chip thickness. The apparatus uses a chamber with one surface made of elastomer membrane. A medium pressure in the chamber is uniformly applying to the elastomer membrane, and the elastomer membrane applies uniform pressure onto chips that eventually bond to substrate. A heated surface supports the product substrate. As noted above, the system can have an upper chamber only, with the lower part being an ambient gas and/or pressure environment. Alternatively, a lower chamber may be used to control the environment (gas medium) and pressure.

[0067] FIG. 10 is a flowchart illustrating a method for uniform pressure gang bonding. Although the method is depicted as a sequence of numbered steps for clarity, the numbering does not necessarily dictate the order of the steps. It should be understood that some of these steps may be skipped, performed in parallel, or performed without the requirement of maintaining a strict order of sequence. Generally however, the method follows the numeric order of the depicted steps and corresponds to the device descriptions presented above. The method starts at Step 1000.

[0068] Step 1002 provides a lower plate and an expandable upper chamber with an elastic surface. Typically, the elastic surface is made from an elastomer material having a Young's modulus in a range of 40 to 1000 kPA. Step 1004 deposits (assembles) a plurality of components overlying a substrate top surface. Step 1006 positions the substrate overlying the lower plate, with the top surface underlying and adjacent to the elastic surface. Step 1008 creates a positive upper chamber medium pressure differential in the expandable upper chamber. Typically, Step 1008 creates a pressure differential in a range of 0.5 atm and 10 atm. The upper chamber medium may be either a gas or a liquid. Step 1010 deforms the elastic surface. Typically, Step 1010 deforms the elastic surface in a range between 0.05 mm and 20 mm, in response to the positive upper chamber medium pressure differential. In response to deforming the elastic surface, Step 1012 applies a uniform pressure on the plurality of components.

[0069] In some aspects, simultaneous with the application of the uniform pressure in Step 1012, Step 1014 heats the substrate. In response to the uniform pressure and heat, Step 1016 bonds the components to the substrate top surface. In one aspect, depositing the plurality of components overlying the substrate top surface in Step 1004 includes depositing semiconductor devices with electrical contacts overlying corresponding electrical interfaces on the substrate top surface. Then, bonding the components to the substrate top surface in Step 1016 includes solder bonding the semiconductor device electrical contacts to the substrate electrical interfaces.

[0070] In one variation, positioning the substrate top surface underlying and adjacent to the elastic surface in Step 1006 includes the substrate top surface occupying an environment with an ambient atmospheric pressure or an environmental control chamber where the type of gas (atmosphere) medium is controlled. Then, creating the positive upper chamber medium pressure differential in the expandable upper chamber in Step 1008 includes creating an upper chamber pressure greater than the ambient atmospheric pressure, and deforming the elastic surface in Step 1010 includes deforming the elastic surface in a direction towards the substrate top surface. In the case of an environmental control lower chamber being used, the type of gas medium being supplied in Step 1006 is ambient air, an inert gas, a forming gas, formic acid, or a combination of these elements. In another variation, positioning the substrate top surface underlying and adjacent to the elastic surface in

[0071] Step 1006 includes the substrate top surface occupying an ambient control lower chamber, with a seal formed, in part, by the elastic surface of the expandable upper chamber. Creating the positive upper chamber medium pressure differential in the expandable upper chamber in Step 1008 then includes creating an upper chamber pressure in the expandable upper chamber greater than the pressure in the ambient control lower chamber, and deforming the elastic surface in Step 1010 includes deforming the elastic surface in a direction towards the substrate top surface. The pressure in the ambient control lower chamber can be created using one of the following mediums: a vacuum, a partial vacuum, ambient air, an inert gas, a forming gas, formic acid, and combinations thereof. The gases may be used for the purposes of etching or prevention oxidation for example.

[0072] In one aspect, depositing the plurality of components overlying the substrate top surface in Step 1002 includes depositing first components having a first profile height and depositing second components having a second profile height, different than the first profile height. The differences in profile heights may be the result of different component thicknesses or topologies (e.g., navigation keels), a non-planar substrate top surface, or a combination of these factors. It should also be noted that the substrate surface may include wells, with components occupying the wells having a top surface beneath the level of the substrate surface surrounding the well. Then, applying the uniform pressure on the plurality of components in Step 1012 includes applying a uniform first pressure on both the first and second components. More explicitly, applying the uniform first pressure on the first and second components may be described as applying a pressure with difference of less than or equal to 5 kPA for a difference in profile height of up to 100 microns. For example, at a bonding pressure of about 3 atm, the pressure difference of 5 kPA represents a pressure non-uniformity of less than 2%. A 5 kPA pressure difference at 10 atm would yield a non-uniformity of less than 0.5%.

[0073] In one aspect, Step 1002 supplies an elastic surface having a first surface area and Step 1004 deposits components over a substrate top surface having a second surface area greater than the first surface area. Then, the method further comprises Step 1018 subsequent to bonding a first group of components to the substrate top surface in Step 1016. Step 1018 changes the relative overlying orientation of the elastic surface with respect to the substrate top surface, and Step 1020 (represented by the connecting arrow in the figure), repeats the steps required for bonding a second group of components (Steps 1008 through 1016).

[0074] A uniform pressure gang bonding device and associated fabrication method have been provided. Examples of particular materials, dimensions, profiles, and circuit layouts have been presented to illustrate the invention. Although emissive elements, particularly LEDs, have been presented, the methods described herein are also applicable to other devices such as semiconductor ICs, photodiodes, thermistors, pressure sensors, piezoelectric devices, and passive devices. Other variations and embodiments of the invention will occur to those skilled in the art.