Lead Frame Rolling Trace Alignment for Laser Welding
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Solution Overview
Problem
Conventional power semiconductor modules face challenges in heat dissipation due to high current density, leading to elevated joint temperatures, and inconsistent laser welding of lead frames results in reduced visibility for camera detection and increased manufacturing costs.
Innovation Solution
The semiconductor device features lead frames with rolling traces aligned in the same direction, allowing for improved visibility during laser welding by tilting the optical axis of the laser beam, reducing fluctuations in reflected light intensity and preventing false detection, thereby enhancing the welding process and reducing manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If lead frames are laser-welded with random rolling trace directions, then welding can be performed on all lead frames, but camera visibility deteriorates and false detection increases
Solution Approach 1:
The invention changes the orientation parameter of the rolling traces by rotating the lead frame so that the rolling trace direction becomes substantially perpendicular to the projection axis of the visible light. This parameter change optimizes the reflection characteristics of the rolling traces, improving camera visibility and detection accuracy while maintaining welding performance.
2Ease of manufacture
If lead frames are laser-welded with random rolling trace directions, then manufacturing can proceed without additional steps, but manufacturing cost increases due to false detection and inconsistent welding
Solution Approach 1:
The invention performs a preliminary action by rotating the lead frame to align the rolling traces perpendicular to the projection axis before laser welding begins. This preliminary orientation adjustment prevents false detection and inconsistent welding, reducing rework and manufacturing costs without significantly complicating the overall process.
3Manufacturing precision
If the optical axis of the laser beam is tilted, then welding quality improves, but reflected light intensity fluctuations increase causing false detection
Solution Approach 1:
The invention introduces asymmetry in the optical configuration by tilting the laser beam optical axis relative to the vertical line on the lead frame surface. This asymmetric arrangement optimizes welding quality by improving laser beam coupling with the rolling traces while the perpendicular orientation of rolling traces to the projection axis compensates for reflection fluctuations.
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 configuration improves camera visibility, reduces false detection during laser welding, and decreases inconsistent welding results, allowing for a more efficient and cost-effective manufacturing process by aligning rolling traces perpendicular to the projection axis of the laser beam.
Implementation Method 1
a laser beam 64 is radiated from a laser emitting unit 63 onto the upper lead frame 61, to melt and solidify the upper and lower lead frames 60 and 61
Implementation Method 2
capturing light reflected off of the sections to be laser-welded using a camera
Implementation Method 3
a semiconductor chip 58 attached onto a conductive pattern 55 of the patterned insulating substrate 56 with a solder 57 therebetween
Implementation Method 4
a resin case 62 that is attached to the heat dissipating base 51 by a silicone adhesive 62a
Data Source
Figure 1
Figure 2
Figure 3(a)~3(b)
AI summary
A purpose is to reliably laser-weld a plurality of lead frames with less inconsistency, and to improve the visibility of the camera to reduce false detection of the sections to be welded. Arranging the direction (rolling direction) of the rolling traces (19) of each of the lead frames (10, 11) in the same direction allows uniform absorption of the laser beam (14) on each of the lead frames (10, 11), which reduces the fluctuations of laser welding in each of the lead frames (10, 11). As a result, the number of points to be welded can be reduced, lowering the manufacturing costs. In addition, fluctuations in the intensity of the light reflected off of each of the lead frames (10, 11) can be reduced by arranging the direction (rolling direction) of the rolling traces (19) of each of the lead frames (10, 11) in the same direction, which improves the visibility of the camera (25) and reduces false detection of the sections to be welded.