High-Aspect-Ratio Connection Pin With Solder Barrier Layers
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Solution Overview
Problem
There is a need for connection materials with improved stability and reliability, especially for semiconductor connections with narrow pitch spacings, where existing materials like metal pins and solder pins face challenges in bridging, heat dissipation, and manufacturing methods.
Innovation Solution
The development of solder paste for connection pins with a specific composition and structure, including a metal pin with a solder layer, to enhance electrical and thermal conductivity, and a semiconductor package design that ensures excellent connection reliability even at high aspect ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal pin or solder pins are used for connection, then bridging risk is reduced and thermal conductivity is improved, but manufacturing complexity and process development needs increase
Solution Approach 1:
The connection pin is divided into distinct functional segments: a metal pin body for structural support and thermal conduction, a solder layer for bonding, and a diffusion barrier layer for preventing intermetallic compound formation. This segmentation allows each layer to be optimized independently for its specific function while simplifying the overall manufacturing process by using standard plating techniques.
Solution Approach 2:
The connection pin employs a composite structure with multiple materials: a copper or copper alloy pin body providing high thermal and electrical conductivity, a solder layer (tin-based) for reliable bonding to substrates, and a diffusion barrier layer (nickel or similar) to prevent unwanted diffusion. This composite approach maximizes the advantages of each material while mitigating their individual limitations.
2Length of moving object
If high aspect ratio connection pins are used, then narrow pitch spacing is achieved, but connection stability and solder paste reliability deteriorate
Solution Approach 1:
The connection pin applies local quality by providing different properties at different locations: the pin body maintains high aspect ratio for narrow pitch spacing, while the bottom surface receives a specially engineered solder layer with optimized composition and thickness for enhanced bonding. The diffusion barrier layer is applied locally at the interface where it is most needed to prevent intermetallic compound formation that would compromise connection stability.
Solution Approach 2:
The invention changes critical parameters of the solder layer to improve high aspect ratio pin reliability: the solder layer thickness is optimized to 1-10 μm (thinner than conventional), silver content is controlled at 1.5-4.0 weight % to balance strength and ductility, and the composition is specifically tailored to prevent excessive intermetallic compound formation during reflow, thereby maintaining connection stability despite the high aspect ratio.
3Strength
If solder layer thickness is increased, then bonding strength is improved, but thermal conductivity and electrical conductivity decrease
Solution Approach 1:
The solder layer parameters are precisely optimized to resolve the contradiction between bonding strength and conductivity: thickness is controlled at 1-10 μm (much thinner than conventional solder layers), silver content is limited to 1.5-4.0 weight %, and the composition is specifically designed to form minimal intermetallic compounds. This parameter optimization ensures the thin solder layer maintains adequate bonding strength while preserving the high thermal and electrical conductivity of the underlying metal pin.
Solution Approach 2:
The connection pin uses a composite structure where the solder layer acts as a thin bonding interface rather than the primary load-bearing and conduction path. The metal pin body (copper or copper alloy) provides the main thermal and electrical conduction pathway, while the solder layer's primary function is bonding, allowing it to be much thinner than in conventional designs where solder is the main structural element.
4Ease of manufacture
If conventional solder paste is used, then manufacturing process is simple, but corrosion and hardening issues occur during pin mounting
Solution Approach 1:
The diffusion barrier layer (nickel or similar material) acts as an intermediary between the copper pin body and the tin-based solder layer. This intermediate layer prevents direct contact between copper and tin, blocking the diffusion that would otherwise cause corrosion and hardening of the solder paste during the mounting and reflow processes. The barrier layer is applied using standard electroplating techniques, maintaining process simplicity while solving the reliability issues.
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 solution significantly reduces defect rates in semiconductor connections, enhances electrical reliability, improves productivity, and ensures stability and accuracy in manufacturing, while maintaining high thermal conductivity and reliability at high aspect ratios.
Implementation Method 1
The solder layer is plated onto the exterior surface of the metal pin
Implementation Method 2
a diffusion layer introduced to prevent the formation of intermetallic compounds by the diffusion of metal alloy atoms in the metal pin with tin or other metal atoms in the solder layer
Implementation Method 3
since the metal pin or solder pins are made of metals with high thermal conductivity, they also exhibit a heat dissipation effect, releasing the heat generated in the semiconductor to the substrate
Implementation Method 4
solder paste for connection pin that offers excellent connection reliability when connecting pins to semiconductors and other components
Data Source
AI summary
In one aspect of the present invention, the connection pin comprises a columnar structure with a diameter ranging from 60 to 500 micrometers (μm) and an aspect ratio (length to diameter) ranging from 1 to 10. Furthermore, the angle formed between the horizontal and vertical surfaces of the said structure is characterized by being between 90°±3°.