Printed Wiring Board Solder-Resist Surface Roughness Control
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Solution Overview
Problem
Existing printed wiring boards face challenges in achieving consistent underfill flow and enhanced adhesive strength between the solder-resist layer and the underfill material, leading to issues with void formation and reliability under thermal cycling.
Innovation Solution
A method involving a solder-resist layer with a controlled surface roughness, achieved through leveling and roughening treatments, to create conductive pads for electronic component mounting, ensuring a consistent underfill flow and improved adhesive strength by maintaining a maximum surface roughness of 0.3-7.5 μm and an arithmetic mean deviation of 0.2-0.7 μm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the solder-resist layer surface is left smooth (conventional approach), then the manufacturing process is simple, but the underfill flow is inconsistent and adhesive strength is poor
Solution Approach 1:
The patent applies parameter changes by controlling the surface roughness of the solder-resist layer within specific ranges (Ra: 0.2-0.7 μm, Rmax: 0.3-7.5 μm). This quantitative parameter control transforms the surface morphology to optimize underfill flow and adhesion, resolving the contradiction between simple manufacturing and reliable bonding.
Solution Approach 2:
The patent implements preliminary action by performing surface leveling and roughening treatments on the solder-resist layer before underfill application. These preparatory surface modifications create optimal surface conditions in advance, ensuring consistent underfill flow and strong adhesion while maintaining a manageable manufacturing process.
2Reliability
If the surface roughness is increased to enhance adhesion, then the adhesive strength improves, but void formation increases
Solution Approach 1:
The patent resolves this contradiction through precise parameter changes by defining specific roughness ranges (Ra: 0.2-0.7 μm, Rmax: 0.3-7.5 μm). These controlled parameter changes optimize the balance between adhesion enhancement and void prevention, ensuring that the surface is rough enough for strong bonding but not so rough as to trap voids.
3Reliability
If no surface treatment is applied (conventional approach), then the manufacturing process is simple, but underfill flow is inconsistent
Solution Approach 1:
The patent applies parameter changes by controlling surface roughness within specific ranges to achieve consistent underfill flow. This quantitative control transforms the surface properties to optimize capillary action and fluid dynamics, ensuring reliable underfill penetration while maintaining a practical manufacturing process.
Solution Approach 2:
The patent implements preliminary surface treatment actions (leveling and roughening) before underfill application. These preparatory steps create optimal surface conditions in advance, ensuring consistent underfill flow behavior during assembly while keeping the overall manufacturing process manageable and repeatable.
Data Source
AI summary
A method of manufacturing a printed wiring board includes preparing a wiring substrate having a conductive circuit, coating a solder-resist layer over the conductive circuit, leveling a surface of the solder-resist layer so as to obtain a maximum surface roughness in a predetermined range, removing the resin film from the surface of the solder-resist layer, and forming multiple openings in the surface of the solder-resist layer to expose multiple portions of the conductive circuit so as to form multiple conductive pads for mounting an electronic components.