Semiconductor Package Resin Buffering for Solder Expansion Cracks
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Solution Overview
Problem
Existing semiconductor devices face challenges with crack generation in the molding resin and moisture ingress when using solder for heat dissipation, especially during high-temperature soldering processes.
Innovation Solution
A semiconductor device design that includes a heat spreader, semiconductor element, insulating sheet, lead frames, and molding resin, with a hole filled with a low Young's modulus resin to accommodate solder expansion and prevent moisture entry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If grease is replaced with solder to improve heat dissipation performance, then thermal resistance is reduced, but cracks are generated in the molding resin due to solder volume expansion during melting
Solution Approach 1:
A hole is formed in the molding resin before soldering to provide a predetermined space that can accommodate the volume expansion of solder during melting. This pre-prepared cushioning space prevents the solder from spurring out and causing cracks in the molding resin, thus resolving the contradiction between improving heat dissipation and maintaining resin integrity.
2Strength
If a hole is formed in the molding resin to accommodate solder expansion, then crack generation is suppressed, but moisture enters through the hole causing deterioration in withstand voltage and corrosion
Solution Approach 1:
An inert gas or vacuum is introduced into the hole formed in the molding resin to act as an intermediary that prevents moisture from entering through the hole. This mediator fills the hole with a substance that does not cause corrosion or deterioration, thus resolving the contradiction between preventing cracks and blocking moisture ingress.
3Volume of moving object
If the semiconductor device is miniaturized to increase power density, then device size is reduced, but heat dissipation performance deteriorates
Solution Approach 1:
The thermal conductivity parameter of the heat dissipation path is changed by replacing grease with solder, which has superior thermal conductivity. This parameter change compensates for the reduced heat dissipation capacity caused by miniaturization, thus resolving the contradiction between reducing device size and maintaining heat dissipation performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The low Young's modulus resin effectively absorbs solder expansion, reducing internal pressure and preventing crack formation in the molding resin, while also suppressing moisture ingress to prevent corrosion and voltage degradation.
Implementation Method 1
the low Young's modulus resin filled in the hole is softened and deformed in the direction of forming a space in the hole, so that the excessive solder corresponding to the volume expansion can be accommodated in the hole
Implementation Method 2
since the hole is filled with the low Young's modulus resin, entry of moisture from the outside can be suppressed
Data Source
AI summary
An object is to provide a technique capable of suppressing generation of a crack in a molding resin and suppressing entry of moisture from the outside. A semiconductor device includes a heat spreader, a semiconductor element provided on an upper surface of the heat spreader, an insulating sheet provided on a lower surface of the heat spreader, a lead frame joined to an upper surface of the semiconductor element via solder, and a molding resin that seals one end side of the lead frame, the semiconductor element, the heat spreader, and the insulating sheet. A hole is formed from an upper surface of the molding resin to a joining surface of the lead frame with the semiconductor element, and the hole is filled with a low Young's modulus resin having a Young's modulus lower than that of the molding resin.