Micro-module hot channel sealing method

Micro-module hot channel sealing is typically achieved using solder-based or direct bonding techniques, such as Au-Sn eutectic bonding or copper-to-ceramic/copper bonding, to ensure leak-free, high-thermal-conductivity microchannels.

Overview of Sealing Methods

Micro-module hot channels in high-power electronic devices require robust sealing to prevent coolant leakage while maintaining excellent thermal performance. Common approaches include:

• Eutectic Bonding: Gold–tin (Au-Sn) eutectic bonding is widely used to seal microchannels in multilayer structures. This method provides strong mechanical adhesion and high thermal conductivity, making it suitable for microchannels embedded in substrates like DBC (Direct Bonded Copper) or LTCC (Low-Temperature Co-fired Ceramic) .
• Solder-Joint Integration: In microchannel coolers, the DBC substrate can be soldered directly to the liquid-cooled base plate. This eliminates the thermal barrier of intermediate layers and ensures a sealed interface for the hot channel .
• Copper-to-Ceramic and Copper-to-Copper Direct Bonding: These techniques allow stacking multiple inner layers with high surface area for heat transfer. The top and bottom sealing layers, along with inlet and outlet openings, are bonded to form a leak-proof microchannel network .

Structural Considerations

• Multilayer Assembly: Microchannel coolers are often built by stacking 8–10 inner layers with hexagonal or pillar-shaped structures. The sealing layers on top and bottom encapsulate the channels, while posts and wings inside the channels guide fluid flow and enhance heat transfer .
• Thermal and Mechanical Reliability: Proper sealing ensures minimal thermal resistance at the interface and prevents mechanical failure under high heat fluxes. Techniques like Au-Sn bonding also allow for high-temperature operation and long-term reliability .

Practical Implementation

1. Surface Preparation: Substrate surfaces are cleaned and functionalized (hydrophilic or hydrophobic) to improve bonding quality.
2. Layer Alignment: Inner microchannel layers are precisely aligned to ensure uniform flow and avoid leakage.
3. Bonding Process: Eutectic soldering or direct bonding is performed under controlled temperature and pressure to seal the channels.
4. Testing: Sealed microchannels are tested for leakage, pressure tolerance, and thermal performance to validate the sealing method .

Summary

The micro-module hot channel sealing method relies on high-precision bonding techniques such as Au-Sn eutectic bonding, solder-joint integration, and copper-to-ceramic/copper direct bonding. These methods provide leak-proof, thermally efficient, and mechanically robust microchannels, essential for high-power electronic cooling applications in CPUs, GPUs, and power modules. Proper multilayer assembly, surface preparation, and testing are critical to ensure long-term reliability and optimal heat dissipation.