Surface-Mount PCB Corner Mini-Pads for Warpage Mismatch
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Solution Overview
Problem
Warpage in surface-mount packages and printed circuit boards leads to reduced joint yield and increased risk of solder bridges, affecting board-level and system-level reliability as package sizes increase.
Innovation Solution
The use of mini-pads with varying shapes and thicknesses applied to the corners of the printed circuit board joint area to compensate for warpage, reducing the degree of mismatch between the package and the PCB, thereby preventing solder bridges during soldering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If package sizes are increased to meet high-performance computing demands, then computing power and capacity are improved, but warpage of the package increases leading to reduced joint yield and increased solder bridges
Solution Approach 1:
The patent applies different thicknesses of the joint area in different locations - specifically, the joint area has varying thickness with greater thickness at corners compared to center regions. This local variation in geometry compensates for warpage effects that occur during soldering, maintaining proper alignment between the package and PCB corners even as package size increases, thereby preventing solder bridges while preserving the benefits of larger package volume.
2Volume of moving object
If package sizes are increased, then computing capacity is improved, but the degree of warpage increases causing solder bridges
Solution Approach 1:
The joint area is designed with non-uniform thickness, specifically thicker at the corners and thinner at the center. This local quality variation creates a geometric compensation mechanism that counteracts warpage-induced misalignment during the soldering process, preventing solder bridges from forming between adjacent pads even when the overall package size is large.
Solution Approach 2:
The patent introduces a third dimension (thickness variation) to the joint area geometry to solve a two-dimensional alignment problem. By varying the thickness of the joint area in the Z-direction, the patent compensates for warpage effects in the X-Y plane, effectively using dimensional transformation to eliminate solder bridges.
3Ease of manufacture
If uniform joint area thickness is used, then manufacturing is simplified, but warpage-induced misalignment causes reduced joint yield
Solution Approach 1:
Rather than using a uniform joint area thickness, the patent implements local quality variation with different thicknesses at different locations (thicker at corners, thinner at center). This approach maintains manufacturability through standard PCB fabrication processes while achieving the precision needed to compensate for warpage and ensure proper alignment during soldering.
Data Source
AI summary
Methods for improving joinder between a surface-mount package and a printed circuit board are disclosed. The warpage at a corner of the surface-mount package and at a corresponding corner of a joint area on the printed circuit board are measured to determine the degree of mismatch. A mini-pad is applied to the corner between the surface-mount package and the joint area on the printed circuit board. The thickness of the mini-pad pushes against the surface-mount package and the printed circuit board, reducing the degree of mismatch below a critical dimension of a ball grid array of the surface-mount package. The surface-mount package can then be soldered to the joint area, reducing or preventing the formation of solder bridges and short circuits.