Lead Frame Recess Structure for Wire Bond Stress Relief
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Solution Overview
Problem
The stress occurring at the bonding interface between the lead frame and the epoxy-based solid resin due to differing linear expansion coefficients during heat generation in semiconductor devices leads to potential cracking or disconnection of wires.
Innovation Solution
A semiconductor apparatus with a lead frame featuring a recess on its surface to increase the contact area and adhesive force with the sealing material, thereby reducing stress and preventing wire disconnection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If epoxy-based solid resin is used for sealing material, then heat resistance and insulation are improved, but stress occurs at bonding interface due to linear expansion coefficient difference
Solution Approach 1:
The patent introduces a recess portion in the lead frame at the bonding interface location, creating a localized structural feature that specifically addresses the stress concentration problem at that critical area while maintaining the overall rigid structure of the lead frame for heat resistance
2Reliability
If epoxy-based solid resin is used for sealing material, then insulation is improved, but wire may be cracked or disconnected due to stress
Solution Approach 1:
The recess portion is designed in advance to compensate for thermal expansion stress before it can damage the wire. The recess acts as a buffer zone that absorbs the stress generated during temperature cycles, preventing wire cracking or disconnection before they occur
3Strength
If recess is formed on lead frame surface, then adhesive force with sealing material is improved, but device complexity increases
Solution Approach 1:
The recess portion divides the bonding interface into two distinct surfaces: the bottom surface of the recess and the surrounding flat surface. This segmentation increases the total adhesive contact area between the lead frame and sealing material, improving bonding strength while keeping the structural modification simple and localized
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 recessed design enhances the adhesive force and heat dissipation, preventing the peeling of the interface between the lead frame and the solid resin, thus suppressing connection failures between the lead frame and the wire.
Implementation Method 1
a first recess 20 is formed on an upper surface of the lead frame 2... the adhesive force and heat dissipation, preventing the peeling of the interface between the lead frame and the solid resin
Implementation Method 2
semiconductor devices generate heat as switching operations are performed... the adhesive force and heat dissipation
Implementation Method 3
when the linear expansion coefficient of the solid resin and the linear expansion coefficient of a lead frame differ from each other, a stress occurs at a bonding interface between the solid resin and the lead frame as respective temperatures of the solid resin and the lead frame rise
Data Source
AI summary
A semiconductor apparatus includes a substrate, a semiconductor device arranged on an upper surface of the substrate, a lead frame bonded to an upper surface of the semiconductor device via a bonding material, the lead frame having a first recess on an upper surface thereof, a wire connected to the first recess, and a resin that seals the substrate, the semiconductor device, the lead frame, and the wire.