Solder Interconnect Reflow Normalization After Test Board Removal
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Solution Overview
Problem
The removal of circuit package modules from test boards results in uneven solder ball heights, making it difficult to remount the modules on different test boards or clamp them to test fixtures.
Innovation Solution
A system and method involving a fixture with a recess and a stencil having apertures aligned with solder interconnects, where solder paste is applied through the stencil onto the interconnects, followed by reflow to normalize their height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If circuit package modules are removed from test boards for subsequent testing, then the modules can be reused for different tests, but the solder balls become uneven in height making remounting difficult
Solution Approach 1:
The patent applies preliminary action by performing the solder paste application and reflow process immediately after module removal from the test board. The stencil is positioned and solder paste is applied to the solder balls before any damage or contamination occurs, ensuring the solder balls are normalized while still in their original locations, making them ready for subsequent remounting operations.
Solution Approach 2:
The patent utilizes parameter changes by controlling the reflow process parameters (temperature, time, atmosphere) to selectively add solder material to the solder balls. The reflow process melts the solder paste and allows it to flow onto the solder balls, changing their height parameter. After cooling, the solder balls achieve uniform height, resolving the height uniformity issue while maintaining reusability.
2Ease of operation
If solder paste is applied to normalize solder ball heights, then remounting becomes easier, but additional process steps are required
Solution Approach 1:
The patent introduces a stencil as an intermediary tool that facilitates the solder paste application process. The stencil with precisely positioned apertures acts as a mediator between the solder paste and the solder balls, ensuring accurate material deposition only where needed. This intermediary device simplifies the overall process by providing a straightforward, repeatable method for normalizing solder ball heights without requiring complex equipment or multiple process steps.
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
The method effectively normalizes solder interconnect heights, improving planarity and facilitating remounting on test boards or clamping to fixtures, with reduced variation from 44 μm to less than 16 μm.
Implementation Method 1
heating the circuit package module to reflow the solder interconnects with the added solder paste
Data Source
AI summary
A method for normalizing the solder interconnects (e.g., normalizing the height of the solder ball interconnects) in a circuit package module (e.g., dual-sided mold grid array package module) after removal from a test board includes receiving in a fixture the circuit package module upside down and removably coupling a stencil to the fixture and over the circuit package module. The stencil has a pattern of apertures that coincides with the pattern of solder interconnects of the circuit package module. The method also includes applying solder paste over the stencil to pass through the apertures to add solder paste to the solder interconnects. The method also includes removing the stencil-from over the fixture, and removing the circuit package module from the fixture. The circuit package module can be heated to reflow the solder interconnects with the added solder paste.