PCB Heat Transfer Pattern Segmentation for Solder Bridge Prevention
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Solution Overview
Problem
Conventional printed wiring boards with heat sinks face challenges in heat dissipation and connectability due to variations in stand-off values and solder paste dispersion, leading to potential non-connection issues between the heat sink and heat transfer pattern, especially in components with narrow pitches.
Innovation Solution
A printed wiring board design featuring a heat transfer pattern with through holes and conductive patterns thermally connected to the heat transfer pattern, covered with solder resist to expose connecting lands that facilitate effective heat dissipation and reliable connections by controlling solder flow and cohesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the solder paste thickness is decreased to prevent bridge between leads, then the risk of bridge is reduced, but the connectability between heat sink and heat transfer pattern deteriorates due to stand-off variation and solder paste dispersion
Solution Approach 1:
The heat transfer pattern is segmented into multiple connecting lands (first land group and second land group) that are spatially separated and distributed. This segmentation allows the solder paste to form multiple independent connection points, ensuring that even if some connections are weak due to stand-off variation, other connections remain reliable. The segmentation also prevents solder bridge between leads while maintaining adequate thermal connection area.
Solution Approach 2:
Different regions of the heat transfer pattern are assigned different functions through local quality variation. The first land group adjacent to through holes provides primary thermal connection with enhanced solder volume, while the second land group not adjacent to through holes provides secondary connection and prevents solder overflow. This local differentiation optimizes both connectability and bridge prevention in specific areas.
2Temperature
If a through hole is provided for heat dissipation, then the heat dissipation effect is improved, but the solder paste may flow into the through hole causing connection issues
Solution Approach 1:
The connecting lands are segmented into two groups based on their position relative to the through hole. The first land group is adjacent to the through hole and benefits from solder paste accumulation, while the second land group is positioned away from the through hole to prevent solder overflow issues. This spatial segmentation resolves the conflict between heat dissipation and connection reliability.
Solution Approach 2:
The solder resist layer acts as an intermediary that selectively exposes different regions of the heat transfer pattern. By controlling which areas are exposed and which are covered, the solder resist mediates between the through hole (for heat dissipation) and the connecting lands (for reliable connection), preventing solder paste from flowing into the through hole while ensuring adequate connection areas.
3Object-affected harmful factors
If the solder paste is printed only on the solder area avoiding solder resist, then solder bridge is prevented, but the cohesive effect that raises solder due to surface tension is lost
Solution Approach 1:
The solder resist pattern is segmented to expose specific regions (connecting lands) while covering others. This selective exposure allows the solder paste to be printed on areas that need connection (providing cohesive effect and surface tension rise) while avoiding areas where solder bridge would occur. The segmented approach enables both bridge prevention and connection strength enhancement.
Solution Approach 2:
Different regions have different solder paste application characteristics through local quality variation. Areas with exposed heat transfer pattern receive solder paste that benefits from cohesive effect and surface tension, while areas near leads have solder resist coverage to prevent bridge. This local differentiation resolves the contradiction between preventing bridge and maintaining connection strength.
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
Enhances heat dissipation and connectability between the heat sink and heat transfer pattern, ensuring reliable joint formation even with variations in stand-off values and solder paste dispersion, thereby improving the overall performance of electronic components with heat sinks.
Implementation Method 1
using such a cohesive effect that the solder paste in a portion on the solder resist moves to an exposed portion of the heat transfer pattern and rises due to the surface tension when the solder paste is fused
Implementation Method 2
the heat transfer pattern and a through hole conductor thermally connected to the conductive pattern are formed within the through hole
Data Source
AI summary
A printed wiring board has a heat transfer pattern facing a heat sink of an electronic component, on a first surface layer on which the electronic component having the heat sink is mounted. The printed wiring board has a through hole conductor formed in a through hole penetrating the printed wiring board corresponding to the heat transfer pattern, and thermally connected to the heat transfer pattern. The heat transfer pattern has a plurality of connecting lands exposed so as to be connectable to the heat sink of the electronic component by solder while being divided by a solder resist. The plurality of the connecting lands include lands adjacent to the through holes, and lands not adjacent to the through holes. The heat dissipation of the electronic component is enhanced while enhancing the connectability of the heat transfer pattern with the heat sink of the electronic component, at being mounted.