PCB Solder Bump Height Correction Using Low-Melting Metal Balls
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Solution Overview
Problem
Current methods for forming solder bumps on printed wiring boards often damage the conductor pad surface when adjusting bump height, leading to reduced connection reliability and inability to achieve desired height within a narrow allowable range.
Innovation Solution
A manufacturing method involving the use of low melting point metal balls to adjust bump heights by loading and melting them, ensuring the conductor pad is not damaged and maintaining connection reliability, with precise selection and positioning using flux and laser heating to achieve desired heights.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the solder bump having a small height is melted and removed to correct the height, then the height of the solder bump can be adjusted, but the conductor pad surface is likely to be damaged and connection reliability drops
Solution Approach 1:
Instead of removing the solder bump to correct height (conventional method), the invention inverts the approach by adding a low melting point metal ball to the existing solder bump. This addition allows height adjustment without damaging the conductor pad, thereby maintaining connection reliability while achieving the desired solder bump height.
2Reliability
If the solder ball is replaced before reflow to detect and replace abnormal solder balls, then connection reliability can be improved, but this cannot address solder bumps with insufficient height after reflow
Solution Approach 1:
The invention performs preliminary height adjustment by adding a low melting point metal ball to the solder bump before the final reflow process. This preliminary action allows the solder bump height to be corrected in advance, and the subsequent reflow process integrates the added metal ball into the bump, achieving both reliability improvement and height correction capability.
3Productivity
If a large number of solder bumps are arranged on the package board, then the quantity of connections increases, but each solder bump must be miniaturized and height dispersion narrows, making height correction more difficult
Solution Approach 1:
The invention changes the physical state parameter of the correction material by using a low melting point metal ball that can be melted and integrated into the existing solder bump. This parameter change allows precise height adjustment of miniaturized solder bumps without affecting the overall high-density arrangement, maintaining both productivity and manufacturing precision.
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 method effectively adjusts bump heights within a requested range without damaging the conductor pad, enhancing connection reliability and reducing heat history on the printed wiring board, allowing for precise and reliable solder bump formation.
Implementation Method 1
loading a low melting point metal ball to a detected low bump or the place in which no bump is formed so as to adjust the height; and (d) intensifying the height of the low bump by melting the low melting point metal ball by heating
Implementation Method 2
intensifying the height of the low bump by melting the low melting point metal ball by heating
Data Source
AI summary
A solder ball is loaded on a bump having a small height (FIG. 5(B)) and the height of the bump is intensified by melting the solder ball by heating with laser (FIG. 5(C)). Thus, the heights of the bumps are adjusted within a requested allowable range. Because the bump is not removed by heating when the height of the low bump is intensified, the printed wiring board is not subjected to local heat history thereby intensifying reliability of the bump of a printed wiring board.