Test Board Design for Qualifying PCB Assembly and Repair Processes
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Solution Overview
Problem
Standard fabrication and assembly methods lack suitable materials and methods to evaluate inner layer quality and solder joint quality in Class 3 circuit boards, which are critical for maintaining high-quality and reliable circuits.
Innovation Solution
A method and test board design that includes primary and secondary process specifications for assembling and repairing circuit boards, featuring functional and non-functional sections with SIR and CAF test patterns to assess surface cleanliness and inner layer build quality, respectively, and exposing samples to thermal, humidity, and vibration test conditions to evaluate process quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard fabrication and assembly methods are used, then manufacturing simplicity is maintained, but inner layer quality and solder joint quality cannot be evaluated
Solution Approach 1:
The test board is divided into multiple independent sections (first section with functional circuits, second section with non-functional daisy-chained circuits) that can be tested separately. Each section includes specific test patterns (SIR, CAF) designed to evaluate particular quality attributes, allowing systematic assessment of inner layer quality and solder joint quality without requiring complete board functionality.
Solution Approach 2:
The patent creates simplified test circuit boards that replicate specific critical features of the production boards rather than building complete functional boards. The test boards include simplified versions of circuit sections with embedded test patterns that copy the essential structural characteristics needed for quality evaluation, reducing complexity while maintaining measurement capability.
2Reliability
If comprehensive quality evaluation is implemented, then reliability is improved, but manufacturing cost increases
Solution Approach 1:
Instead of testing the entire board uniformly, the patent applies localized test patterns (SIR patterns for surface cleanliness, CAF patterns for inner layer quality) at specific locations where quality evaluation is most critical. This allows comprehensive quality assessment focused on key areas rather than uniform testing of the entire board, reducing overall testing complexity and cost.
Solution Approach 2:
The test boards are designed with embedded test patterns and test structures built into them during the fabrication process itself, before assembly and testing. This preliminary incorporation of test capabilities allows quality evaluation to be performed as part of the manufacturing process rather than requiring separate, additional testing steps, thereby reducing overall manufacturing cost while maintaining reliability.
3Adaptability or versatility
If lead-free assembly process is used, then environmental compliance is improved, but process qualification difficulty increases
Solution Approach 1:
The test board design serves multiple functions simultaneously: it evaluates surface cleanliness (SIR patterns), inner layer quality (CAF patterns), solder joint quality, and circuit functionality. This multi-functional test board can be used to qualify lead-free assembly processes, rework processes, and repair processes, making the qualification system universally applicable to different process types and reducing the need for separate qualification procedures for each process.
Data Source
AI summary
A method for qualifying circuit board fabrication, assembly, and repair processes includes establishing primary assembly process specifications and secondary repair process specifications. A group of test circuit boards is assembled using the primary assembly process, with each board having a section of components linked together to provide functional circuits and a section of components daisy-chained together to provide non-functional circuits, and with each section also including SIR test patterns and CAF test patterns. A subset of the assembled test boards is then repaired using the secondary repair process. A sample of each set of the test boards is exposed to test conditions including thermal cycle test conditions, humidity test conditions, and vibration test conditions. Inner layer build quality, surface cleanliness, circuit performance, and solder joint quality are then evaluated using the provided circuitry.