Dip Soldering for Low-Profile Wafer-Level Package Bumps
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Solution Overview
Problem
Current semiconductor packaging methods for solder bump formation, such as electroplating and ball placement, are expensive, time-consuming, and challenging for thin wafer handling, limiting further thickness scaling and increasing costs significantly as bump profiles shrink.
Innovation Solution
A dip soldering process that involves a molten solder bath with flux for forming low-profile solder bumps on wafer-level packages, using a system that can handle wafers individually or in batches, with controlled temperature and dipping angles to reduce package thickness and processing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electroplating or ball placement methods are used for solder bump formation, then reliable board attachment is achieved, but manufacturing cost increases and processing time extends
Solution Approach 1:
The patent employs a disposable stencil that is attached to the wafer, exposed to define bump patterns, and then removed. This eliminates the need for expensive reusable masks and complex alignment systems required in traditional electroplating and ball placement methods, significantly reducing manufacturing cost while maintaining reliable solder bump formation for board attachment
Solution Approach 2:
The patent extracts and eliminates the expensive mask/stencil design and photo/alignment tool steps from the traditional process. By using a simple disposable stencil that can be directly exposed and removed, the complex alignment and masking infrastructure is taken out of the manufacturing flow, reducing both equipment cost and processing time
2Reliability
If electroplating or ball placement methods are used for solder bump formation, then solder bumps are formed, but processing time increases
Solution Approach 1:
The patent enables continuous processing by using a disposable stencil that can be quickly applied, exposed, and removed without requiring complex alignment procedures. The stencil remains in place during the solder bump formation process, allowing continuous production flow without the time-consuming alignment and repositioning steps required in traditional methods
Solution Approach 2:
The disposable stencil eliminates the need for expensive, time-consuming alignment and repositioning operations. The stencil is simply attached, exposed, and removed in a straightforward sequence, dramatically reducing processing time compared to traditional methods that require precise alignment of reusable masks and stencils
3Reliability
If traditional solder bump formation methods are used, then bumps are formed on wafers, but package thickness cannot be scaled down further
Solution Approach 1:
The patent changes the solder bump formation parameters by using a dip soldering process with controlled immersion depth and angle. By adjusting the dipping parameters rather than relying on fixed mask-defined bump heights, the process achieves consistent low-profile bumps that enable ultra-thin package scaling while maintaining reliable electrical connections
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
Enables further package thickness scaling with a significant reduction in costs, achieving a 50% height reduction in solder bumps compared to traditional methods, facilitating the production of ultra-thin wafer-level packages and quad-flat no-leads packages.
Implementation Method 1
A dip soldering process that involves a molten solder bath with flux for forming low-profile solder bumps on wafer-level packages
Data Source
AI summary
Techniques are described herein for a dip soldering process which provides a low-profile, low-cost solder bump formation process which may be implemented to promote package thickness scaling (e.g., reduce the overall package thickness). For example, the dip soldering process disclosed herein may enable ultra-thin wafer-level packages (WLP), ultra-thin wafer level quad-flat no-leads (WQFN) packages, or the like.