Thermocompression bond tips and related apparatus and methods
A bond tip for thermocompression bonding a bottom surface includes a die contact area and a low surface energy material covering at least a portion of the bottom surface. The low surface energy material may cover substantially all of the bottom surface, or only a peripheral portion surrounding the die contact area. The die contact area may be recessed with respect to the peripheral portion a depth at least as great as a thickness of a semiconductor die to be received in the recessed die contact area. A method of thermocompression bonding is also disclosed.
1. A thermocompression bonding apparatus, comprising:
a bond tip having a bottom surface comprising:
a die contact area on a bottom surface of the bond tip comprising an area oriented parallel to a surface of a semiconductor die to be bonded; and
a low surface energy (LSE) material located entirely within a footprint of the bottom surface of the bond tip and secured against removal during a thermocompression bonding operation on at least a portion of the bottom surface of the bond tip.
2. The apparatus of claim 1 , wherein the bottom surface comprises a length and a width greater than a length and a width of the die contact area, and a peripheral portion of the bottom surface surrounds the die contact area.
3. The apparatus of claim 2 , wherein the LSE material covers substantially an entirety of the bottom surface.
4. The apparatus of claim 2 , wherein the LSE material covers only the peripheral portion of the bottom surface outside the die contact area.
5. The apparatus of claim 4 , wherein a length and a width of the die contact area substantially corresponds to a length and a width of a semiconductor die to be received on the die contact area.
6. The apparatus of claim 4 , wherein the bottom surface comprises a single planar surface and the low surface energy material covering the peripheral portion protrudes from the bottom surface.
7. The apparatus of claim 4 , wherein the peripheral portion of the bottom surface is recessed with respect to the die contact area to a depth, and a thickness of the LSE material is substantially equal to the depth of the recessed peripheral portion.
8. The apparatus of claim 4 , wherein a length and a width of the die contact area substantially corresponds to a length and a width of a semiconductor die to be received on the die contact area, and the die contact area of the bottom surface is recessed from the peripheral portion to a depth at least as great as a thickness of a semiconductor die to be received in the recessed die contact area.
9. The apparatus of claim 8 , wherein the depth is equal to the thickness of the semiconductor die to be received in the recessed die contact area plus a portion of a height of pillars protruding from the semiconductor die.
10. The apparatus of claim 8 , wherein a transition between each sidewall of the recessed die contact area and an adjacent area of the peripheral portion of the bottom surface comprises a chamfer extending laterally outwardly from the sidewall.
11. The apparatus of claim 10 , wherein each chamfer lies at about a 30° angle to about a 60° angle to an associated sidewall.
12. The apparatus of claim 10 , wherein the LSE material covers the chamfer.
13. The apparatus of claim 1 , wherein the low surface energy material is selected from the group consisting of a parylene material, a polytetrafluoroethylene (PTFE) material, a perfluoroalkoxyl (PFA) material, graphene, or diamond-like-carbon (DLC).
14. The apparatus of claim 1 , wherein the low surface energy material is formulated to accommodate application of heat and remain in a solid state substantially without decomposition at a temperature required for thermocompression bonding.
15. The apparatus of claim 14 , wherein the temperature required for thermocompression bonding lies within a range of about 220° C. to about 400° C.
16. A method of thermocompression bonding a semiconductor die comprising pillars protruding from a surface thereof, the method comprising:
picking the semiconductor die bearing a non-conductive film (NCF) material over a pillar-bearing surface from which the pillars protrude with a die contact area of a bottom surface of a bond tip of a thermocompression bonding apparatus, the bottom surface oriented parallel to a top surface of the semiconductor die, the top surface opposite the pillar-bearing surface of the semiconductor die, the bottom surface having a length and a width greater than a length and width of the semiconductor die, leaving a peripheral portion of the bottom surface around the die contact area exposed, the bottom surface having a low surface energy (LSE) material located entirely within a footprint of the bottom surface and secured on at least a portion thereof including at least part of the exposed peripheral portion; moving the semiconductor die with the bond tip to a position with the pillars aligned with conductive elements of a substrate;
applying heat to the semiconductor die and transforming NCF material to a flowable state;
applying force to the semiconductor die with the bond tip during application of heat to press the pillars against the aligned conductive elements, fill a bondline between the semiconductor die and the substrate with flowable NCF material around and between the pillars and cause at least one fillet of the flowable NCF material to extrude from at least a portion of a periphery of the semiconductor die and contact the at least part of the exposed peripheral portion of the bottom surface of the bond tip;
bonding the pillars to the aligned conductive elements and letting the NCF material at least partially cure; and
retracting the bond tip from the semiconductor die with the LSE material secured to the at least a portion thereof and without adhesion of the NCF material of the at least one fillet to any of the at least a portion of the bottom surface to which is secured the low surface energy (LSE) material.
17. The method of claim 16 , wherein bonding the pillars of the semiconductor die to the aligned conductive elements of the substrate comprises one of reflowing solder of the pillars in contact with the aligned conductive elements by heating, and letting the solder cool to a solid state; and diffusion bonding metal of the pillars to the aligned conductive elements by the heating and cooling.
18. The method of claim 16 , wherein moving the semiconductor die with the bond tip to a position with the pillars aligned with conductive elements of a substrate comprises moving the semiconductor die to a position with the pillars aligned with conductive elements of another semiconductor die.
19. The thermocompression bonding apparatus of claim 1 , wherein the thermocompression bonding apparatus is configured to apply heat and pressure to a product through the bond tip.