PCB Solder Resist Opening Design for High-Density Component Mounting
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Solution Overview
Problem
As electronic components are downsized, it becomes challenging to reduce the size of spacers between components and the printed wiring board while maintaining high accuracy, which can lead to short-circuit failures due to excessive solder projection.
Innovation Solution
The design involves a printed circuit board with chip components and a printed wiring board, where the components are aligned such that the distance between them is minimized, and the solder resist film openings are sized to match the components, controlling the solder projection and preventing short-circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If electronic components are downsized to reduce printed wiring board size, then component size is reduced, but the distance between adjacent components decreases making short-circuit more likely
Solution Approach 1:
A spacer is introduced as an intermediary element between the electronic component and the printed wiring board. The spacer physically separates the component from the board surface, preventing solder from projecting excessively and causing short-circuits between adjacent components. This mediator enables high-density mounting while maintaining electrical isolation.
Solution Approach 2:
Instead of increasing horizontal distance between components to prevent short-circuits, the solution moves to the vertical dimension by using a spacer to elevate the component. This dimensional transition allows components to be placed closer horizontally while maintaining adequate solder projection control through vertical separation.
2Reliability
If a spacer is disposed between the electronic component and the board to prevent sinking and reduce solder projection, then short-circuit risk is reduced, but the spacer becomes difficult to downsize and position accurately with smaller components
Solution Approach 1:
The spacer structure is merged with the printed wiring board by forming it as an integral part of the board substrate. This integration eliminates the need for separate spacer components and their associated positioning challenges, while still providing the necessary elevation and solder projection control for high-density component mounting.
3Productivity
If the distance between adjacent electronic components is reduced for high-density mounting, then productivity is improved, but solder projection may cause short-circuits
Solution Approach 1:
The spacer serves as a mediator that enables high-density component placement by controlling solder projection. It allows components to be mounted closer together while preventing solder from bridging adjacent components, thus maintaining both high productivity and reliability.
Data Source
AI summary
A printed circuit board includes a first chip component, a second chip component, and a printed wiring board. The first chip component and the second chip component each has a length L2 in the longitudinal direction. A relationship of 0.894≤L2/L1≤1.120 is satisfied, where L1 represents a length of the first opening in the longitudinal direction. A relationship of 0.894≤L2/L4≤1.120 is satisfied, where length L4 represents a length of the second opening in the longitudinal direction. A relationship of 0.183≤LOA/LiA≤0.309 is satisfied, where LiA represents a length of the first land in the longitudinal direction, and LOA represents a thickness of solder on an end surface of the first electrode. A relationship of 0.183≤LOB/LiB≤0.309 is satisfied, where LiB represents a length of the second land in the longitudinal direction, and LOB represents a thickness of solder on an end surface of the second electrode.