Solder Paste Bump Formation for Narrow Electrode Gaps
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Solution Overview
Problem
The challenge is to form solder bumps on electronic components with narrow electrode gaps (less than 25 μm) without encountering bridging or solder dewetting issues, which are common in existing methods.
Innovation Solution
A solder paste with very fine solder particles and a high content of volatile dispersion medium is used, where the dispersion medium is volatilized to form a solder particle-containing layer, and then the solder is melted in a reducing atmosphere to create uniform solder bumps, suppressing bridging and dewetting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional solder paste is used on narrow electrode gaps, then solder bumps can be formed, but bridging occurs between adjacent electrodes
Solution Approach 1:
The solder paste is segmented into very fine particles (average particle size of 10 μm or less) and distributed with a high content of volatile dispersion medium (30% by mass or more), allowing controlled volatilization that prevents bridging while ensuring complete electrode coverage
Solution Approach 2:
The invention changes the physical parameters of the solder paste by using very fine particles and a high content of volatile dispersion medium, and controls the volatilization process through specific heating conditions to prevent bridging while ensuring complete electrode coverage
2Manufacturing precision
If conventional solder paste is used on narrow electrode gaps, then solder bumps can be formed, but solder dewetting occurs on electrode surfaces
Solution Approach 1:
The volatile dispersion medium is preliminarily incorporated in large amounts into the solder paste before application, and through controlled volatilization heating, creates optimal conditions for solder wetting on electrode surfaces before the final reflow step
Solution Approach 2:
The invention changes the composition parameters by incorporating 30% by mass or more volatile dispersion medium, and controls the thermal parameters through two-stage heating (volatilization step followed by reflow step) to prevent dewetting and ensure complete electrode coverage
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
This method effectively forms solder bumps on narrow gaps without bridging or dewetting, ensuring reliable connections and uniformity, even with tight electrode spacing.
Implementation Method 1
a step of heating the member and the solder paste at a temperature T1 below a melting point of solder constituting the solder particles to volatilize the dispersion medium in the solder paste
Implementation Method 2
a step of heating the member and the solder particle-containing layer in a reducing atmosphere at a temperature T2 equal to or higher than the melting point of the solder constituting the solder particles to melt the solder particles in the solder particle-containing layer
Data Source
AI summary
A method for forming solder bumps by using a solder paste containing solder particles and a volatile dispersion medium, the method including: applying a solder paste on a member having a plurality of electrodes on the surface; heating the member and the solder paste at a temperature below the melting point of solder constituting the solder particles to form a solder particle-containing layer; heating the member and the solder particle-containing layer in a reducing atmosphere and at a temperature equal to or higher than the melting point of the solder constituting the solder particles to form solder bumps; and removing, by cleaning, a residue of the solder particle-containing layer remaining between adjacent solder bumps, in which the solder particles have an average particle size of 10 μm or less, and the content of the dispersion medium in the solder paste is 30% by mass or more.