Mounting Board Opening Configuration for Solder Void Reduction
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Solution Overview
Problem
Existing mounting boards face challenges in establishing reliable connections with electronic components due to voids created during the reflow process, which increase electrical resistance and decrease mechanical strength, and can lead to short circuits from solder spreading on the solder resist.
Innovation Solution
The proposed mounting board features an insulating resin layer with electrode pads and a solder resist layer having specific opening configurations, where the second opening region is larger in the Y1-Y2 direction than the distance between its ends, allowing solder paste to flow into and fill voids, reducing the likelihood of voids between the electrode pads and electronic component electrodes, and preventing solder from spreading onto the solder resist.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional opening configuration is used in the solder resist layer, then the structure is simple and easy to manufacture, but voids are created during reflow process that increase electrical resistance and decrease mechanical strength
Solution Approach 1:
The opening in the solder resist layer is divided into two distinct regions: a first opening region positioned over the electrode pad and a second opening region positioned adjacent to it. This segmentation allows each region to serve a specific function - the first region enables solder paste application while the second region provides a reservoir to collect excess solder and prevent short circuits, thereby improving connection reliability without excessive complexity
Solution Approach 2:
The second opening region acts as an intermediary reservoir between the electrode pad and the surrounding solder resist area. It collects and contains excess solder paste that flows during reflow, preventing it from creating short circuits on the solder resist while maintaining a controlled interface for reliable electrical connection
2Reliability
If the second opening region is made larger to prevent solder spreading, then short circuits are prevented, but the amount of solder paste required increases
Solution Approach 1:
The opening configuration implements local quality by creating a second opening region with specific dimensional characteristics - its maximum dimension in the first direction is greater than the distance between the third and fourth sides. This localized expansion in a specific direction provides effective solder containment and short circuit prevention while minimizing the overall opening area and solder paste consumption
Data Source
AI summary
A mounting board includes an electrode pad and an insulating protective film on an insulating resin layer. In a plan view, the electrode pad includes first and second sides running parallel in a first direction. The insulating protective film includes an opening including first and second regions adjoining each other in the first direction. The first region lies over the electrode pad to expose part of the electrode pad. The second region exposes part of the insulating resin layer. The first region is defined by third and fourth sides that are between the first and second sides in a second direction perpendicular to the first direction and run parallel in the first direction. The maximum dimension of the second region in the second direction is greater than the distance between respective ends of the third and fourth sides at which the first region adjoins the second region.