Semiconductor Package Stem Symmetric Plate Protrusion Warping
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Solution Overview
Problem
Existing semiconductor package stems face challenges in reducing warping, which affects the bonding and airtightness of the cap, due to differences in thermal expansion coefficients between the plate and frame materials.
Innovation Solution
A stem design where the plate protrudes equally from the top and bottom surfaces of the frame, with a lead holding member and insulating sealing parts, to balance thermal stress and reduce warping, using materials like copper for the plate and metals for the frame, and silver braze for bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the plate and frame are bonded using materials with different thermal expansion coefficients, then the bonding strength is improved, but warping occurs due to thermal stress during heating and cooling processes
Solution Approach 1:
The patent changes the geometric parameter of the plate by making it protrude equally from both the top and bottom surfaces of the frame. This symmetric configuration balances the thermal stress distribution, allowing the use of materials with different thermal expansion coefficients while preventing warping during temperature changes.
Solution Approach 2:
The patent introduces asymmetric bonding area distribution by having the plate protrude from both surfaces of the frame. The bonding areas at the top and bottom are made equal, creating a balanced asymmetric structure that compensates for differential thermal expansion between materials.
2Strength
If the bonding area between plate and frame is increased, then the bonding strength is improved, but the warping is exacerbated due to greater thermal stress accumulation
Solution Approach 1:
The patent optimizes the bonding area parameter by distributing the bonding interface symmetrically at both ends of the frame. This configuration reduces thermal stress accumulation compared to a large concentrated bonding area, while still providing sufficient bonding strength through the distributed bonding interfaces.
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 design effectively reduces warping to less than 50 μm, allowing for reliable bonding and improved airtightness of the semiconductor package by balancing thermal expansion stresses and minimizing the bonded area.
Implementation Method 1
differences in thermal expansion coefficients between the plate and frame materials
Implementation Method 2
silver braze for bonding
Data Source
AI summary
A stem for a semiconductor package, includes a plate, a frame, positioned on an outer periphery of the plate in a plan view, and bonded to the plate, and a lead terminal held in a state insulated from the plate and the frame. The plate protrudes from a top surface and a bottom surface of the frame, and a protruding amount of the plate from the top surface and a protruding amount of the plate from the bottom surface are the same.