Lead Frame Through-Hole Welding for Low-Heat Die Attach
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Solution Overview
Problem
The joining of heat dissipation plates with frame members in semiconductor devices can cause deformation or damage due to heat, especially when laser welding is used, leading to potential quality issues in the lead frame and semiconductor device.
Innovation Solution
A lead frame design featuring through-holes in the support portions of the frame member, allowing for low-output laser welding with shorter irradiation times, which prevents unnecessary deformation and damage by focusing the laser energy only on the vicinity of the through-holes for efficient welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser welding is used to join frame member and heat dissipation plate, then welding efficiency is improved, but thermal deformation and damage occur due to high heat input
Solution Approach 1:
A groove is formed in advance at the joining position between the frame member and heat dissipation plate. This preliminary action allows the laser beam to be concentrated in a predefined region, enabling efficient welding while limiting heat spread to surrounding areas, thus preventing thermal deformation and damage.
Solution Approach 2:
The groove structure creates a localized welding zone with specific geometric characteristics. The laser energy is concentrated in this localized region, achieving sufficient welding penetration without excessive heat input to adjacent areas, thereby resolving the contradiction between welding efficiency and thermal damage prevention.
2Manufacturing precision
If laser output is increased to ensure adequate welding, then welding quality is improved, but deformation and damage of surrounding areas occur
Solution Approach 1:
The groove is pre-formed to define the welding zone boundaries. This allows the use of higher laser output for adequate welding penetration while the groove geometry confines the heat-affected zone, preventing deformation and damage to surrounding areas.
Solution Approach 2:
The groove geometry (depth, width, angle) is optimized to control heat distribution during welding. By adjusting these parameters, sufficient welding quality is achieved with controlled heat input, preventing thermal damage to surrounding areas even at higher laser outputs.
3Strength
If laser irradiation time is extended to ensure proper welding, then welding strength is improved, but heat-affected zone expands causing deformation
Solution Approach 1:
The groove is prepared in advance to concentrate the laser energy path. This allows for extended irradiation time to achieve strong welding penetration while the groove walls confine and conduct heat away from surrounding areas, preventing heat-affected zone expansion and deformation.
Solution Approach 2:
The groove structure creates a localized heat conduction path along its walls. Extended laser irradiation strengthens the weld within this localized region while the groove geometry directs heat flow, preventing excessive temperature rise and deformation in surrounding areas.
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 ensures reliable welding of the heat dissipation plate to the frame member without causing deformation or damage, maintaining the quality of the lead frame and semiconductor device by controlling the laser output and irradiation time.
Implementation Method 1
laser welding is used for joining fine parts such as joining of a frame member and a heat dissipation plate
Implementation Method 2
laser is radiated until the frame member formed of a thin plate is penetrated through to weld the frame member and the heat dissipation plate
Data Source
AI summary
A lead frame includes: a support portion having a through-hole formed in as end; a lead; and a heat dissipation plate welded with the support portion in one opening of the through-hole. A manufacturing method of a lead frame includes: shaping a frame member from a metal plate, the frame member including a support portion having a through-hole formed in an end, and a lead; and welding a heat dissipation plate with the support portion in one opening of the through hole.