Textured PCB Test Pads for Reliable OSP Contact
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Solution Overview
Problem
Existing printed circuit board (PCB) test pads coated with organic solderability preservative (OSP) coatings face challenges in maintaining consistent electrical contact during testing, leading to reduced first pass yields and increased costs due to corrosion and the need for additional processing steps.
Innovation Solution
The PCB test pads are textured with dimples and vertical surfaces to enhance electrical contact, allowing probes to penetrate the OSP coating and establish a reliable connection, thereby increasing the conductive probe surface area and reducing contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a non-conductive corrosion-resistant coating (e.g., OSP) is applied to the test pad, then corrosion resistance is improved, but electrical contact quality deteriorates
Solution Approach 1:
The test pad surface is textured with dimples that create localized regions with different properties. The peaks provide corrosion-resistant coating coverage while the valleys maintain exposed conductive material for electrical contact, achieving both corrosion resistance and good electrical contact simultaneously
Solution Approach 2:
The surface is transformed from flat to three-dimensional with vertically extending surfaces and dimples. This dimensional change creates multiple contact points and pathways for electrical contact while maintaining corrosion protection on the outer surfaces
2Object-generated harmful factors
If a textured surface with vertical surfaces and dimples is created on the test pad, then electrical contact quality is improved, but manufacturing complexity increases
Solution Approach 1:
The test pad surface is segmented into multiple dimples arranged in a pattern. Each dimple creates localized vertical surfaces that enhance probe contact. This segmentation approach achieves the desired electrical contact improvement through a systematic, repeatable pattern that can be manufactured using standard PCB processes
Solution Approach 2:
The surface morphology is changed by controlling the depth, diameter, and spacing of dimples. By optimizing these parameters, the textured surface provides enhanced electrical contact while remaining compatible with existing PCB manufacturing capabilities
3Measurement precision
If multiple test retries are performed to achieve sufficient testing yield, then testing accuracy is improved, but productivity decreases
Solution Approach 1:
The test pad surface is pre-textured during PCB manufacturing to ensure optimal electrical contact characteristics before testing. This preliminary action eliminates the need for multiple test retries by ensuring that the first test contact is successful, thereby maintaining high testing accuracy while maximizing productivity
Data Source
AI summary
A printed circuit board includes a substrate and at least one electrical circuit provided at least partially on a surface layer of the printed circuit board. The electrical circuit includes an electrical trace that is in electrical connection with a test pad provided for accessibility on the surface layer, the test pad being sized and shaped for probing to test an aspect of the circuit, the test pad having a conductive probe surface that is structured to provide at least one vertical surface that extends from the probe surface toward the surface layer and thus providing an edge between the vertical surface and the probe surface, the probe surface having a coating of a material to protect the conductive probe surface from corrosion.