PCB Positioning Hole Photolithography for Optical Alignment
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Solution Overview
Problem
Conventional printed circuit boards with positioning holes have low positioning accuracy between optical semiconductor elements and guide holes, making precise alignment of optical fibers and semiconductor elements difficult.
Innovation Solution
A printed circuit board design featuring a solder resist layer with a positioning hole formed by photolithography above the guide hole, providing a high positioning accuracy of ±15 μm or less, allowing for precise alignment of optical fibers and semiconductor elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If drilling is used to form the guide hole, then the guide hole can be formed with a diameter suitable for optical fiber positioning, but the positioning accuracy deteriorates to about ±50 μm
Solution Approach 1:
The patent replaces the mechanical drilling process with a photolithography-based positioning hole formation process. The positioning hole is formed by exposing and developing a photoresist layer, eliminating the need for mechanical drilling and achieving much higher positioning accuracy of about ±15 μm or less.
2Manufacturing precision
If photolithography is used to form the opening in the solder resist layer, then the opening can be formed with high positioning accuracy of about ±15 μm, but the manufacturing process becomes more complex
Solution Approach 1:
The patent merges the formation of the positioning hole and the opening in the solder resist layer into a single photolithography process. Both features are formed simultaneously by exposing the photoresist layer to light through a mask, eliminating the need for separate positioning and opening formation steps.
3Manufacturing precision
If the positioning hole diameter is made smaller than the guide hole diameter, then the positioning accuracy improves, but the ease of operation for alignment deteriorates
Solution Approach 1:
The patent introduces the positioning hole as an intermediary reference feature that is precisely positioned relative to the guide hole. This positioning hole serves as a mediator that transfers the high positioning accuracy to the optical fiber alignment process, allowing the guide pin to be accurately positioned relative to the semiconductor element.
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 high accuracy positioning hole enables precise positioning of optical fibers and semiconductor elements, improving the alignment of light-receiving or light-emitting units and optical fibers, enhancing the overall positioning accuracy.
Implementation Method 1
the positioning hole having a diameter smaller than that of the guide hole and formed by photolithography above the guide hole
Data Source
AI summary
There is provided a printed circuit board including an insulating substrate having a guide hole, a solder resist layer coated on a surface of the insulating substrate, and a connection pad arranged on the surface of the insulating substrate and having an outer periphery covered with the solder resist layer and a central portion exposed in an opening formed in the solder resist layer. The solder resist layer has a positioning hole having a diameter smaller than that of the guide hole and formed by photolithography above the guide hole simultaneously with the opening.