Lead Frame Scale Structure for Void-Free Semiconductor Molding
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Solution Overview
Problem
Conventional resin sealing methods for semiconductor devices often result in voids due to air entrapment, which reduce insulation, moisture-proof, and heat dissipation properties, and require costly mold modifications to address unexpected voids.
Innovation Solution
A semiconductor device with scale-like portions on the lead frame across resin boundaries allows air discharge during molding, eliminating the need for mold vents and enabling high-function, reliable devices at lower costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If air vents are provided in the mold to discharge voids, then void occurrence is reduced, but mold complexity and manufacturing cost increase
Solution Approach 1:
The patent extracts the air vent function from the mold structure and relocates it to the lead frame. The scale-like portions are formed directly on the lead frame surface, separating the void discharge function from the mold itself. This allows the mold to remain simple while still achieving effective void inhibition through the lead frame's integrated scale-like structures.
Solution Approach 2:
The scale-like portions on the lead frame act as an intermediary structure between the molding resin and the void discharge path. Instead of requiring direct mold modification, the lead frame surface features serve as the mediating element that enables air entrapment prevention during resin injection, resolving the contradiction between reliability improvement and mold complexity.
2Reliability
If air vents are provided in the mold, then void occurrence is reduced, but manufacturing time and cost increase due to mold working
Solution Approach 1:
The scale-like portions are pre-formed on the lead frame before the molding process begins. This preliminary structuring of the lead frame surface eliminates the need for time-consuming mold modifications. The void discharge pathways are already in place through the scale-like features, allowing immediate use without additional mold working time.
Solution Approach 2:
Instead of permanently modifying the expensive mold structure, the patent uses the lead frame as a disposable or replaceable component that incorporates the void discharge function. The scale-like portions are formed on the lead frame which can be replaced if needed, avoiding the time and cost of mold reworking while maintaining reliable void inhibition.
3Ease of manufacture
If conventional resin sealing is performed without scale-like portions, then manufacturing is simpler, but voids occur reducing insulation and heat dissipation properties
Solution Approach 1:
The patent applies local quality changes to the lead frame surface by forming scale-like portions only in specific areas where void entrapment is likely to occur during resin injection. This localized structuring maintains ease of manufacture for the overall device while providing targeted void inhibition exactly where needed, preserving both insulation and heat dissipation properties without complicating the general manufacturing process.
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 scale-like portions effectively inhibit voids without mold modifications, ensuring high reliability and functionality while reducing production costs by allowing air discharge during the resin sealing process.
Implementation Method 1
the scale-like portion provided over both sides across the resin boundary portion on the lead frame, whereby air present inside the resin can be discharged to the outside of the mold during a resin sealing process
Data Source
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AI summary
In a semiconductor device (101), on a heat dissipation portion (2B) of a lead frame (2) opposite to a mounting portion (2A) on which a semiconductor element (1) is mounted, a thin molding portion (9d) having a thickness of about 0.02 mm to 0.3 mm is formed by a second molding resin (9) which is a high-heat-dissipation resin. A scale-like portion (3b) on which scale-shaped projections are consecutively formed is provided over both sides across a resin boundary portion (2c) of the heat dissipation portion (2B). The scale-like portion (3b) reaches abutting surfaces of an upper die and a lower die of a mold used in a molding process. Thus, the same void inhibition effect as with an air vent is obtained.