External Electrode Alloy Layer for Solder Burst Prevention
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Solution Overview
Problem
Existing electronic parts with surface plating layers are prone to solder burst and whisker generation during soldering, leading to short circuits and unreliable joint strength, especially when exposed to high temperatures.
Innovation Solution
Incorporating a Cu—Ni or Cu—Mn alloy layer with a Sn-containing layer on the surface, which rapidly reacts to form an intermetallic compound with a high melting point, preventing solder burst and whisker formation by expelling Sn and ensuring strong solder joints at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a plating layer is formed on the external electrode surface to improve solder wettability, then solder wettability is improved, but solder burst occurs during soldering due to vaporization of trapped plating solution
Solution Approach 1:
The external electrode is segmented into multiple functional layers: a compact base layer (Cu thick-film electrode) that prevents solution penetration, and a surface plating layer (Ni or Sn) that provides solder wettability. This layered structure resolves the contradiction by isolating the plating solution from the electrode interior while maintaining surface functionality.
Solution Approach 2:
The external electrode uses a composite structure combining Cu thick-film electrode material with Ni or Sn plating materials. The Cu thick-film provides structural integrity and solution barrier properties, while the Ni/Sn plating layers provide solder wettability, creating a composite material system that simultaneously achieves both requirements.
2Object-affected harmful factors
If the external electrode is densified to prevent solution penetration, then solder burst is suppressed, but glass component dissolution in plating solution cannot be completely prevented
Solution Approach 1:
The compact Cu thick-film electrode layer is formed beforehand as a barrier structure before applying the plating solution. This preliminary compact layer prevents or minimizes glass component dissolution by blocking solution penetration into the electrode interior, thereby stabilizing the plating process and preventing solder burst.
Solution Approach 2:
The Cu thick-film electrode acts as an intermediary barrier between the plating solution and the electrode interior. It mediates the interaction by selectively allowing controlled glass component dissolution at the surface while preventing solution penetration deeper into the electrode structure, thus stabilizing the plating process.
3Reliability
If a Sn plating layer is used as the outermost layer, then solder wettability is improved, but whiskers are generated causing short circuits
Solution Approach 1:
The Ni plating layer serves as an intermediary barrier between the Sn plating layer and the Cu thick-film electrode. This intermediate Ni layer suppresses Sn whisker generation by preventing direct contact between Sn and the Cu substrate, while still allowing the Sn layer to maintain its solder wettability function.
Solution Approach 2:
The dual-layer plating structure (Ni + Sn) creates a composite material system where the Ni layer provides whisker suppression functionality and the Sn layer provides solder wettability. This composite plating structure simultaneously achieves both requirements without the harmful effects of single-layer plating.
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 solution effectively suppresses solder burst and whisker generation, achieving reliable high-temperature joint strength and preventing short circuits, while maintaining good solder wettability and preventing oxidation-related solder quality deterioration.
Implementation Method 1
the alloy layer rapidly reacts with the Sn-containing layer by a rapid diffusion action at an interface between the Cu—Ni alloy layer and/or the Cu—Mn alloy layer and the Sn-containing layer to produce and solidify an intermetallic compound having a high melting point
Implementation Method 2
produce and solidify an intermetallic compound having a high melting point (for example, a melting point of 400° C. or more), and therefore rapid generation of water vapor from within the external electrode
Data Source
AI summary
An electronic part that includes an electronic part main body and an external electrode on the surface of the electronic part main body. The external electrode includes at least one alloy layer selected from among a Cu—Ni alloy layer and a Cu—Mn alloy layer, and a Sn-containing layer on the outer side of the alloy layer. The Sn-containing layer is the outermost layer of the external electrode. The Sn-containing layer is in contact with the alloy layer.