PCB Bump Formation via Masked Laser Ablation
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Solution Overview
Problem
The existing printed circuit board manufacturing processes incur additional costs due to the requirement of surface treatments and the formation of a second metal layer during the bump formation process, which also degrade the quality of the solder resist and increase manufacturing complexity.
Innovation Solution
The process involves forming a conductive layer with copper alloy as a seed layer, embedding bumps in the solder resist openings using laser machining, and omitting the desmear process to reduce costs and improve quality, with the bumps being made of copper or tin alloys and having the same area as the mask windows, thus minimizing additional processing steps and protecting the solder resist surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If surface treatment and second metal layer formation are performed during bump formation, then adhesion and electrical conductivity are improved, but manufacturing cost increases
Solution Approach 1:
The patent removes the unnecessary surface treatment step from the conventional manufacturing process. By using a mask structure that inherently provides adhesion during bump formation, the separate surface treatment process is extracted and eliminated, reducing manufacturing cost while maintaining reliability
Solution Approach 2:
The mask structure serves multiple functions: it defines the bump pattern, provides adhesion during bump formation, and acts as a protective layer. This multi-functionality eliminates the need for separate surface treatment steps, resolving the contradiction between reliability and manufacturing cost
2Reliability
If surface treatment is performed on solder resist, then adhesion between solder resist and metal layer is improved, but solder resist quality degrades
Solution Approach 1:
The patent extracts and removes the surface treatment step that degrades solder resist quality. By using the mask structure to provide adhesion instead, the harmful surface treatment process is eliminated while maintaining the necessary adhesion properties
Solution Approach 2:
The mask acts as an intermediary structure that provides adhesion during bump formation without directly treating the solder resist surface. This mediator approach maintains solder resist quality while achieving the necessary adhesion for reliable bump formation
3Reliability
If additional processing steps are performed, then bump formation reliability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent merges the adhesion function and pattern definition function into a single mask structure. This consolidation reduces the number of separate processing steps while maintaining bump formation reliability, thereby reducing manufacturing complexity
Solution Approach 2:
The mask structure performs multiple functions simultaneously: pattern definition, adhesion provision, and protection. This multi-functionality reduces the total number of processing steps required, resolving the contradiction between reliability and manufacturing complexity
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 reduces manufacturing costs, enhances the quality of the printed circuit board by eliminating the desmear process, and provides a stable and reliable product with improved reliability and surface protection of the solder resist.
Implementation Method 1
the pad 4 is formed by electroplating the first metal layer 2 using first metal layer 2 as seed layer
Implementation Method 2
forming the window exposing the pad by performing a laser machining on the stacked mask
Data Source
Figure 1a~1d
Figure 1e~5
Figure 6~9
AI summary
A printed circuit board according the presrnt embodiment includes an insulating layer; at least one circuit pattern or pad formed on the insulating layer; a solder resist having an opening section exposing the upper surface of the pad and formed on the insulating layer and a bump formed on the pad exposed through the opening section of the solder resist and having a lower area narrower than the upper area.