UV-Cured Silver Die Attach for Corrosion-Resistant Chip Bonding
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Solution Overview
Problem
Silver-based die-attach materials are prone to corrosion, functional deterioration, and failure when exposed to moisture and corrosive gases, leading to issues such as silver sulfide formation, increased resistance, and whisker growth, which can cause short circuits. Additionally, traditional solutions like hermetic cavity packages increase package size, and overmolding materials can degrade under light exposure.
Innovation Solution
A method and material involving silver particles within a UV curable resin are used to attach a chip to a submount. The material is heated to sinter the silver particles, which act as a heat conduction path, and the UV curable resin is cured with UV light to form a polymer that protects the sintered silver from corrosion without increasing package size or material costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hermetic cavity packages are used to protect silver from corrosion, then corrosion resistance is improved, but package size increases
Solution Approach 1:
The patent extracts the protective function from the entire hermetic cavity package and applies it locally only to the die-attach material surface. By forming a polymer coating specifically on the silver-containing die-attach material, the solution provides corrosion protection without requiring a full hermetic package, thus reducing overall package size while maintaining reliability.
Solution Approach 2:
The patent applies protective properties locally to the die-attach material surface rather than protecting the entire package. The polymer coating is formed specifically on the silver particles within the die-attach material, providing targeted corrosion protection where it is most needed while leaving the rest of the package structure minimal and compact.
2Reliability
If overmolding materials are used to protect against corrosion, then corrosion resistance is improved, but material degradation occurs under light exposure
Solution Approach 1:
The patent changes the chemical composition parameters of the protective material by using UV curable resin instead of traditional overmolding materials. This UV curable resin forms a polymer through photopolymerization that is stable under light exposure, unlike conventional overmolding materials that degrade. The resin contains silver particles and forms a cross-linked polymer network that resists both corrosion and light-induced degradation.
3Temperature
If silver particles are used for thermal conduction, then heat conduction is improved, but corrosion and whisker growth occur
Solution Approach 1:
The patent creates a composite material system consisting of silver particles embedded within a UV curable resin matrix. The silver particles provide excellent thermal conduction properties, while the resin matrix provides corrosion protection and suppresses whisker growth. This composite structure combines the advantages of both materials while mitigating their individual disadvantages.
Solution Approach 2:
The UV curable resin acts as an intermediary protective layer between the silver particles and the corrosive environment. The resin coating on the silver particles provides a barrier against moisture and corrosive gases, preventing silver sulfide formation and whisker growth, while still allowing thermal conduction through the silver particles.
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 protects sintered silver from corrosion and deterioration while maintaining thermal conductivity and preventing whisker growth, thus ensuring reliable chip attachment without the drawbacks of increased package size or material costs.
Implementation Method 1
irradiating, with UV light, the UV curable resin to obtain a polymer on the sintered silver particles
Implementation Method 2
heating a material including silver particles within an ultra-violet (UV) curable resin to obtain the UV curable resin on sintered silver particles
Data Source
AI summary
A die attachment material may include an ultra-violet (UV) curable resin and silver particles to attach a chip to a submount, where the silver particles are positioned within the UV curable resin. A method may include heating the die attachment material to obtain the UV curable resin on sintered silver particles, where at least a portion of the die attachment material is position between a chip and a submount. The method may further include irradiating, with UV light, the UV curable resin to obtain a polymer on the sintered silver particles. The polymer may form a layer on the sintered silver particles.