PCB Thermal Pad Solder Mask Layout for Void-Resistant Reflow
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Solution Overview
Problem
The existing interconnection methods between thermal pads on integrated circuits and printed circuit boards often result in uneven or intermittent solder connections due to issues like air bubbles in the solder paste during reflow, leading to reduced thermal dissipation and potential damage to the integrated circuit.
Innovation Solution
A method of forming a solder connection by creating a solder mask on a thermal pad of a printed circuit board, which leaves unmasked portions and forms mask stripes extending from the edges towards the center, allowing for improved solder paste deposition and reflow to form a more reliable solder connection between the thermal pads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If solder paste is deposited on the entire thermal pad surface, then complete coverage is achieved, but air bubbles form during reflow causing uneven or intermittent connections
Solution Approach 1:
The solder mask is segmented into multiple stripes extending from the edge toward the center of the thermal pad, creating multiple unmasked regions. This segmentation allows solder paste to be deposited in controlled zones, preventing air bubble formation while maintaining connection uniformity across the thermal pad surface.
Solution Approach 2:
Different regions of the thermal pad have different properties: the unmasked portions receive solder paste deposition while the masked portions do not. This local differentiation ensures solder paste is applied only where needed, improving connection reliability by preventing defects in specific areas while maintaining overall connection quality.
2Reliability
If the solder mask covers the entire thermal pad, then solder paste deposition is prevented, but thermal conduction is reduced due to incomplete solder connection
Solution Approach 1:
The solder mask is divided into striped patterns rather than covering the entire thermal pad, creating multiple unmasked regions that allow solder paste deposition. This ensures adequate solder connection for thermal conduction while the masked portions prevent excessive paste application and associated defects.
Solution Approach 2:
The solder mask is applied selectively to specific regions of the thermal pad while leaving other regions unmasked. This local application ensures solder paste is deposited only in areas where it is needed for thermal conduction, maintaining thermal dissipation efficiency while ensuring connection integrity.
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
The proposed method enhances the interconnection between thermal pads, improving thermal conduction and dissipation, thereby reducing the risk of damage to the integrated circuit and extending its operational life.
Implementation Method 1
The solder paste is then reflowed, meaning the solder paste is subjected to heat to melt the solder in the solder paste and thereby form a solder joint or connection between the two thermal pads.
Data Source
AI summary
A method of forming a solder connection includes forming a solder mask on a thermal pad of a printed circuit board. The solder mask leaves unmasked portions of the thermal pad and forming the solder mask includes forming a plurality of mask stripes extending from edges of each unmasked portion towards a center of the unmasked portion. The method includes depositing solder paste on the unmasked portions of the thermal pad and placing an exposed thermal pad of an integrated circuit package on the solder paste deposited on the thermal pad of the printed circuit board. The method includes forming a solder connection by heating the solder paste between the unmasked portions of the thermal pad on the printed circuit board and the exposed thermal pad of the integrated circuit package.