High-Power Module TIM Fabrication via Nano-Silver Sintering
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Solution Overview
Problem
Current high-power modules using SnAgCu alloy for thermal interface materials are prone to intermetallic compound formation at high temperatures, leading to reduced mechanical strength and poor heat dissipation, and existing dispensing technologies risk damaging substrates due to touching methods.
Innovation Solution
A method involving a nano-silver-based slurry with a 9:1 to 1:1 ratio of nano-silver to micron-silver particles, using a non-touching needle dispensing technology and thermocompression sintering to form a TIM layer with over 99% pure silver, avoiding intermetallic compound formation and substrate damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SnAgCu alloy is used as thermal interface material, then the module can be sealed and protected, but intermetallic compounds form at high temperature causing reduced mechanical strength and poor heat dissipation
Solution Approach 1:
The patent changes the material composition parameters by using pure silver (99.99% purity) instead of SnAgCu alloy, and controls the particle size distribution with 90-100 mesh accounting for 70-80% of the silver powder. This parameter change prevents intermetallic compound formation while maintaining mechanical strength and thermal conductivity at high temperatures.
Solution Approach 2:
The patent creates a composite structure by combining silver particles of different sizes (90-100 mesh and finer particles) with organic vehicle, forming a slurry that produces a composite thermal interface material with optimized packing density and thermal conductivity, avoiding the intermetallic compound issue of traditional alloys.
2Ease of manufacture
If touching needle dispensing method is used, then the slurry can be applied to substrate, but the substrate or coating layer is damaged due to height difference on substrate surface
Solution Approach 1:
The patent introduces a non-contact dispensing method as an intermediary approach between the needle and substrate. The slurry is deposited through a non-contact mechanism (such as aerosol or liquid jet deposition) that eliminates mechanical contact, thereby preventing substrate damage while still achieving precise slurry application.
3Object-affected harmful factors
If Pb-free solder alloy is used to reduce hazardous substances, then environmental safety is improved, but intermetallic compounds form at high temperature reducing welding strength to one-third of original
Solution Approach 1:
The patent fundamentally changes the material parameter from Pb-free solder alloy to pure silver (99.99% purity) with specific particle size distribution. This change eliminates the formation of brittle intermetallic compounds (Cu6Sn5 and Cu3Sn) that occur in SnAgCu alloys at high temperatures, while maintaining environmental safety by excluding Pb and other hazardous substances.
Solution Approach 2:
The patent uses pure silver particles with organic vehicle as a disposable thermal interface material that is applied as a slurry and then cured to form a permanent bond. This approach replaces the reusable solder alloy with a single-use slurry formulation that achieves the desired thermal and mechanical properties without intermetallic compound formation.
4Duration of action of stationary object
If holes form in long term heat cycle, then thermal resistance increases, but heat dissipation is eliminated and module fails
Solution Approach 1:
The patent changes the material composition to pure silver with 90-100 mesh particle size accounting for 70-80% of the total, which maintains structural integrity and thermal conductivity during long-term heat cycling. This prevents hole formation and maintains low thermal resistance, ensuring continuous heat dissipation capability and module reliability.
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 provides a stable TIM layer with enhanced thermal conductivity, reduced organic content, and improved mechanical properties, capable of operating above 150°C without embrittlement, while avoiding substrate damage and reducing material costs.
Implementation Method 1
a thermal-interface-material (TIM) layer is formed through thermocompression with sintering
Data Source
AI summary
A method is provided to fabricate a high-power module. A non-touching needle is used to paste a slurry on a heat-dissipation substrate. The slurry comprises nano-silver particles and micron silver particles. The ratio of the two silver particles is 9:1˜1:1. The slurry is pasted on the substrate to be heated up to a temperature kept holding. An integrated chip (IC) is put above the substrate to form a combined piece. A hot presser processes thermocompression to the combined piece to form a thermal-interface-material (TIM) layer with the IC and the substrate. After heat treatment, the TIM contains more than 99 percent of pure silver with only a small amount of organic matter. No volatile organic compounds would be generated after a long term of use. No intermetallic compounds would be generated while the stability under high temperature is obtained. Consequently, embrittlement owing to procedure temperature is dismissed.