Ni-P-Cu Solder Joint Interface for Thermal Cycling Reliability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The repeated heat generation and cooling of power semiconductor elements cause strain and deterioration of solder joints, leading to reliability issues, especially in high-temperature and corrosive environments.
Innovation Solution
A solder joint configuration using a Ni—P—Cu plating layer with a specific composition, including a microcrystalline layer at the interface with the solder joint layer, which contains phases of NiCuP ternary alloy, (Ni,Cu)3P, and Ni3P, to enhance reliability and prevent defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If Sn-Ag based Pb-free solder is used for joining semiconductor elements, then joinability and mechanical properties are improved, but reliability under repeated thermal cycling and corrosive environments deteriorates
Solution Approach 1:
The invention employs a composite plating structure consisting of a Ni-P-Cu layer combined with a Cu-Sn intermetallic compound layer. This composite material approach allows the Ni-P-Cu plating to provide corrosion resistance and structural stability, while the Cu-Sn intermetallic layer provides excellent solder wettability and mechanical bonding, thereby achieving both ease of manufacture and high reliability under thermal cycling conditions.
Solution Approach 2:
The invention optimizes the compositional parameters of the plating layer, specifically controlling the P content at 3-10 mass% and Cu content at 0.5-8 mass%. By precisely adjusting these parameters, the plating layer forms a microcrystalline structure that suppresses harmful intermetallic compound growth while maintaining good solderability, thus improving reliability without sacrificing joinability.
2Temperature
If Cu is used as electrical connection material to reduce thermal resistance, then heat dissipation is improved, but corrosion resistance and migration resistance deteriorate
Solution Approach 1:
The Ni-P-Cu plating layer acts as an intermediary protective barrier between the Cu electrical connection material and the corrosive environment. This plating layer maintains the high thermal conductivity of Cu while providing resistance against sulfide gas corrosion and preventing Cu ion migration, thus resolving the contradiction between heat dissipation and corrosion resistance.
Solution Approach 2:
The composite plating structure combines Ni, P, and Cu elements to create a multi-functional layer that simultaneously provides thermal conductivity (from Cu), corrosion resistance (from Ni-P-Cu alloy), and migration resistance. This composite material approach allows the system to achieve both excellent heat dissipation and protection against harmful environmental factors.
3Object-affected harmful factors
If Ni-P plating is applied to improve corrosion resistance, then protection against sulfide gas is improved, but solder joint reliability under thermal stress deteriorates
Solution Approach 1:
The invention creates a composite plating system where the Ni-P-Cu plating layer provides corrosion resistance while the controlled formation of Cu-Sn intermetallic compounds at the interface enhances solder joint reliability. The Cu element in the plating (0.5-8 mass%) promotes beneficial intermetallic formation that strengthens the solder joint under thermal stress, unlike conventional Ni-P plating that lacks this capability.
Solution Approach 2:
By adjusting the P content to 3-10 mass% and Cu content to 0.5-8 mass% in the plating layer, the invention modifies the plating composition to form a microcrystalline structure. This parameter optimization ensures that the plating maintains corrosion resistance while promoting the formation of a reliable solder interface that can withstand thermal cycling stresses.
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 solder joint configuration significantly reduces the occurrence of defects over time, improving the product's lifespan and reliability, especially in demanding applications with high current specifications and high temperatures.
Implementation Method 1
the Ni—P—Cu plating layer has a microcrystalline layer at an interface with the solder joint layer, and the microcrystalline layer includes a phase containing microcrystals of a NiCuP ternary alloy, a phase containing microcrystals of (Ni,Cu)3P, and a phase containing microcrystals of Ni3P
Data Source
AI summary
In an example, use of a solder joint may include a solder joint layer having a melted solder material containing Sn as a main component and further containing Ag and/or Sb and/or Cu; and a joined body including a Ni—P—Cu plating layer on a surface of the joined body in contact with the solder joint layer. The Ni—P—Cu plating layer may contain Ni as a main component and may contain 0.5% by mass or greater and 8% by mass or less of Cu and 3% by mass or greater and 10% by mass or less of P, and the Ni—P—Cu plating layer may have a microcrystalline layer at an interface with the solder joint layer.