Insulating Protrusions on Circuit Board Lands for Solder Reliability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The long-term reliability of solder bonding in circuit boards is compromised due to stress and strain from thermal expansion differences between substrates and components, leading to cracks and fractures, which are difficult to prevent with existing methods that either increase solder thickness or result in solder extrusion and short circuits.
Innovation Solution
The implementation of insulating protrusions on conductive lands, which support electrodes with solder, allowing a thicker solder layer to remain between the land and electrode, reducing stress and strain, and preventing cracks and fractures by maintaining solder thickness during thermal cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If solder thickness is increased to improve bonding strength, then bonding strength is improved, but solder extrusion occurs causing short circuits
Solution Approach 1:
The patent applies local quality by creating a stepped portion on the land surface that concentrates the solder layer thickness variation in a specific location. The solder layer is made thicker at the stepped portion (first thickness) compared to other areas (second thickness), locally enhancing bonding strength at the critical electrode-land interface while preventing excessive solder spread that causes short circuits.
Solution Approach 2:
The patent introduces a vertical dimension (thickness variation) to the otherwise uniform solder layer by creating a stepped portion. This dimensional change allows the solder to be thicker where needed (at the stepped portion for enhanced bonding) while maintaining appropriate thickness elsewhere, resolving the contradiction between bonding strength and short circuit prevention.
2Reliability
If solder thickness is increased to resist thermal stress, then reliability under thermal cycles is improved, but device complexity increases due to additional structural features
Solution Approach 1:
Instead of uniformly increasing solder thickness throughout the entire land area (which would increase complexity), the patent applies local quality by creating a stepped portion only in specific areas. This localized thickening provides the necessary thermal stress resistance where the electrode connects to the land, while keeping other areas simpler with standard solder thickness.
Solution Approach 2:
The stepped portion is formed on the land surface before solder application, preliminarily preparing the structure to guide and retain solder in the desired thick configuration. This preliminary structural preparation ensures that during thermal cycling, the solder maintains sufficient thickness to resist stress without requiring complex real-time adjustments or additional components.
Data Source
AI summary
An electronic apparatus is provided including a substrate, a conductive land formed on a surface of the substrate, an electronic component including an electrode, at least one insulating protrusion formed on the land in an overlapping region between the land and the electrode in plan view, and a solder that bonds the electronic component to the land, the solder being formed between the electrode and the land in the overlapping region in a normal direction to the surface of the substrate.