Wax Printing Mask Patterning for PCB Run-Out Compensation
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Solution Overview
Problem
Current methods for patterning soldermask layers in printed circuit manufacturing face challenges such as large run-out variations, requiring multiple masks and increasing process errors, and wax patterning systems that are cumbersome due to additional removal steps.
Innovation Solution
A method using a wax printing technique to create a mask pattern on a soldermask layer, where single drops of wax are applied with specified gaps, allowing for uniform patterning of both large and small areas without loading effects, and the wax pattern and soldermask are removed during development, maintaining compatibility with existing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple masks are used to match layer-to-layer alignment due to large run-out variations, then alignment accuracy is improved, but process complexity and run time increase
Solution Approach 1:
The patent applies preliminary action by pre-compensating for run-out variations during the mask design stage. The mask pattern is digitally stretched and adjusted before fabrication to account for anticipated board deformation, eliminating the need for multiple physical masks during the actual patterning process. This preliminary correction maintains alignment accuracy while reducing process complexity.
2Manufacturing precision
If multiple masks are used to handle large run-out variations, then alignment is improved, but run time increases
Solution Approach 1:
The mask is pre-designed with digital stretching to compensate for run-out variations before the patterning process begins. This preliminary action eliminates the need for multiple mask changes during production, significantly reducing cycle time while maintaining alignment accuracy.
3Adaptability or versatility
If wax patterning is used to pattern the mask layer, then patterning flexibility is improved, but process complexity increases due to additional removal steps
Solution Approach 1:
The patent utilizes phase transitions of wax material, which melts at elevated temperatures to allow easy removal from the PCB. This phase change enables the wax mask to be applied flexibly for various patterns and then cleanly removed in a single thermal step, maintaining patterning versatility while simplifying the removal process.
4Ease of manufacture
If conventional photomask methods are used, then process simplicity is maintained, but run-out variations cause scraping and reduced yield
Solution Approach 1:
The mask pattern is pre-distorted through digital stretching to compensate for anticipated run-out variations during the PCB manufacturing process. This preliminary correction ensures that the final pattern aligns correctly even when the board deforms, eliminating the need for scraping and improving yield while maintaining process simplicity.
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 approach improves layer-to-layer accuracy, reduces process errors, and enhances productivity by allowing for run-out matching, while being transparent to current industry practices, enabling better registration and even patterning without additional development time for different area sizes.
Implementation Method 1
the printed circuit board 10 is exposed to, for example, ultraviolet light through the pattern mask 16. In the case where a negative photoactive soldermask is used, areas that are not masked, such as areas 18, in the soldermask are cross-linked during the exposure.
Implementation Method 2
these systems require that extra steps be taken in the process to remove the wax, which can be difficult
Data Source
AI summary
The presently described embodiments use a printing process, e.g. a wax printing technique, to pattern a mask layer (such as a soldermask layer) of, for example, a printed circuit. Substantially all other conventional processes in developing soldermask and exposure processes can be maintained. According to the presently described embodiments, each printed circuit will have a unique pattern that matches uniform and non-uniform runout. In one form, the pattern is comprised of wax single drops having a specified gap to make the process transparent to the current industry practice. Furthermore, the single drops can be used for both large and small areas without any development time differences. In at least one form, the wax pattern and the soldermask in the gap are removed during development.