Die-Die Stacking Mesh Layout for Thermal Stress Resistance
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Solution Overview
Problem
Existing die-die stacking structures face issues such as void formation, delamination, die cracking, and inefficient space utilization due to fully filled underfills, which can lead to popcorn failure and thermal stress-induced damage.
Innovation Solution
A die-die stacking structure with a mesh layout formed by connection members and a protection material, where the protection material bridges the connection members and dummy bump units, eliminating the need for full underfill and providing enhanced thermal stress resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If underfill is fully filled between dies and substrate to strengthen stability, then bump stability is improved, but void formation and delamination risk increase
Solution Approach 1:
The underfill application is segmented into two distinct stages: first applying underfill to fill gaps between adjacent dies, then applying a second amount to fill gaps between the stacked die assembly and substrate. This segmentation prevents void formation by ensuring complete gap filling without trapping air, while maintaining bump stability through progressive saturation of the structure.
2Reliability
If underfill is fully filled to protect bumps, then bump protection is improved, but die cracking and popcorn failure increase due to thermal stress
Solution Approach 1:
The underfill application process is divided into sequential steps: first filling inter-die gaps, then filling the gap between the die assembly and substrate. This segmented approach ensures complete saturation without over-filling, preventing the formation of high underfill fillets that generate thermal stress and cause die cracking or popcorn failure during reflow or thermal cycling.
3Stability of the object's composition
If underfill is applied to fill all gaps, then structural support is improved, but space utilization and layout efficiency decrease
Solution Approach 1:
The patent applies underfill in controlled partial amounts - first sufficient to fill gaps between adjacent dies, then an additional amount to fill gaps between the die assembly and substrate. This partial action approach provides necessary structural support without excessive underfill that would create large fillets and waste宝贵的 layout space, thereby improving area utilization efficiency.
4Reliability
If underfill is used to fill fine pitch bump gaps, then bump stability is improved, but process cycle time increases due to slow underfill flow
Solution Approach 1:
The underfill dispensing process is segmented into two distinct dispensing operations: first dispensing underfill to fill gaps between adjacent dies, then dispensing an additional amount to fill gaps between the die assembly and substrate. This segmentation allows each dispensing step to be optimized independently, reducing overall cycle time compared to attempting to fill all gaps in a single slow process.
Data Source
AI summary
The present invention relates to die-die stacking structure and the method for making the same. The die-die stacking structure comprises a top die having a bottom surface, a first insulation layer covering the bottom surface of the top die, a bottom die having a top surface, a second insulation layer covering the top surface of the bottom die, a plurality of connection members between the top die and the bottom die and a protection material between the first insulation layer and the second insulation layer. The plurality of connection members communicates the top die with the bottom die. The protection material bridges the plurality of connection members to form a mesh layout between the first insulation layer and the second insulation layer. The structure and method of present invention at least provide more strength and stress buffer to resist die warpage and absorb thermal cycling stress, and then prevents the bump and dielectric materials in the die-die stacking structure from cracking caused by thermal stress or external mechanical stress.