Lead Frame Resin Structure for Thin Heat-Dissipating Packages
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Solution Overview
Problem
The use of two kinds of resin in semiconductor devices, specifically high-heat dissipating and low-stress resins, results in poor adhesion between the resins and the lead frame, leading to potential detachment and deficiencies in the molded resin, especially in transfer molding processes.
Innovation Solution
The semiconductor device integrates a thinly-molded portion covering the heat dissipating surface of the lead frame and lead frame space filled portions, which are molded from a high-heat dissipating resin, improving adhesion and strength by increasing the area of contact with the lead frame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a high-heat dissipating resin with high filler content and high viscosity is used, then heat dissipation performance is improved, but resin fluidity deteriorates and adhesion to lead frame and low-stress resin becomes poor
Solution Approach 1:
The patent applies parameter changes by controlling the viscosity of the high-heat dissipating resin to be within a specific range (100 to 500 Poise at 150°C) and adjusting the filler content to 30-70 wt%. These parameter optimizations resolve the contradiction by ensuring the resin has sufficient heat dissipation capability while maintaining adequate fluidity for proper wetting and adhesion during transfer molding.
Solution Approach 2:
The patent uses a composite material system consisting of two different resins (high-heat dissipating resin and low-stress resin) with complementary properties. The high-heat dissipating resin provides thermal management with optimized filler content, while the low-stress resin provides mechanical flexibility and stress relief. This composite approach allows each resin to perform its specialized function without compromising the other's performance.
2Temperature
If the mold resin on the heat dissipating surface is formed thinly to improve heat dissipation, then heat dissipation performance is improved, but adhesion between lead frame and resin decreases and insulation becomes insufficient
Solution Approach 1:
The patent applies local quality by using different resin types in different regions: the high-heat dissipating resin is applied specifically on the heat dissipating surface where thermal performance is critical, while the low-stress resin is used in other regions where mechanical flexibility and adhesion are more important. This regional differentiation allows thin molding on the heat dissipating surface without compromising overall adhesion and insulation.
Solution Approach 2:
The composite resin system enables thin molding on the heat dissipating surface by compensating with the low-stress resin in other areas. The high-heat dissipating resin provides the necessary thermal performance in the thin layer, while the low-stress resin contributes to overall adhesion and mechanical integrity, resolving the contradiction between thin molding and sufficient adhesion/insulation.
3Productivity
If transfer molding with gate portion is used, then manufacturing efficiency is improved, but gate break mark remains on semiconductor device and initial detachment is liable to occur
Solution Approach 1:
The patent applies parameter changes by optimizing the viscosity of the high-heat dissipating resin to be within 100 to 500 Poise at 150°C. This viscosity control ensures the resin has sufficient fluidity to properly wet the lead frame and low-stress resin during transfer molding, preventing initial detachment at the gate break mark while maintaining high molding efficiency.
Solution Approach 2:
The patent applies preliminary action by ensuring the high-heat dissipating resin is properly prepared with optimized viscosity and filler content before the molding process. This preliminary optimization of resin properties ensures adequate wetting and adhesion occur during the transfer molding process, preventing detachment issues at the gate break mark while maintaining production efficiency.
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
This approach enhances adhesion between the mold resins and the lead frame, reduces the likelihood of detachment or deficiencies, and improves heat dissipation and insulation in the semiconductor device.
Implementation Method 1
a high-heat dissipating resin with thermal conductivity of 4 to 10W/m · K
Implementation Method 2
adhesion of the molded high-heat dissipating resin to the low-stress resin and lead frame is low
Data Source
Figure 1~3
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AI summary
In a semiconductor device (100), a thinly-molded portion (8b) covering a whole of a heat dissipating surface (2b) portion of a lead frame (2) and a die pad space filled portion (8c, 8d) are integrally molded from a second mold resin (8), because of which adhesion between the thinly-molded portion (8b) and lead frame (2) improves owing to the die pad space filled portion (8c, 8d) adhering to a side surface of the lead frame (2). Also, as the thinly-molded portion (8b) is partially thicker owing to the die pad space filled portion (8c, 8d), strength of the thinly-molded portion (8b) increases, and a deficiency or cracking is unlikely to occur.