Below are the questions asked during the event, along with their respective answers.
Q: Are these made internally or outsourced?
A: Wakefield-Vette outsources the vapor chambers with strategic long-term partners for products sold through our distribution channels as well as custom parts for OEM manufacturers.
Q: What is diffusion welding?
A: Diffusion welding/bonding is a process where two metal surfaces are brought together under high pressure and temperature and the materials are allowed enough time to diffuse into one another and form a strong joint. This is in contrast to typical welding or bonding where solder or braze material is inserted at the joint.
Q: How wide is the perimeter seal? How much room does it take away from the working size of the VC?
A: The perimeter seal is typically 2-3mm. This is subtracted from the VC working size.
Q: What qualifies as “high volume” to keep unit costs down?
A: Although this is a question for each individual design, a production run of 1000 units or more is a typical MOQ for production. However, runs of smaller volumes can be fabricated.
Q: Is there an “effective thermal conductivity” that can be used in an FEA/CFD model to simulate the vapor chamber spreading without actually modeling the phase change process?
A: Typically, the effective thermal conductivity one can use in FEA/CFD modeling is on the order of 5000 W/mK. However, this should be tuned based on temperature difference, e.g. the thermal conductivity should be tuned until a temperature difference of 3-7K is reached. This should give good agreement with realistic performance.
Q: Are there any patent issues with through holes?
A: There are patents for some types of through holes, but our partner has IP protection for the structures we use.
Q: How the heat capacity that a vapor chamber can transfer is calculated? What’s the theory behind it?
A: The capacity of a vapor chamber is based on the heat capacity of the volume of fluid vapor and internal volume of the vapor chamber.
Q: Can chambers be designed to work vertically?
A: Yes, but gravity effects may lower performance depending on the location of the heat source. If the heat source is at the “bottom” of the vapor chamber (lowest gravity position), then the vapor chamber will work much better than if the heat source is “higher” on the vertical vapor chamber.
Q: Are there structural mechanical limitations to prevent the use of vapor chamber in server applications?
A: The internal supports can be designed to give high structural strength and se we do not see any fundamental limitation to prevent VC use in server applications.
Q: What is the max pressure that we can add to a typical 3mm or 5mm VC plate?
A: Wakefield-Vette suggested maximum pressure is 90psi.
Q: What is the typical life span of vapor chamber?
A: Vapor chambers can have long life as long as they are not mechanically damaged. Life of the product application is typical.
Q: How is the seal integrity of the diffusion bond compared laser welds; what is the typical working life?
A: Diffusion bonding is a long life process and is comparable to laser welds or other brazed joints.
Q: Over the evaporator region (e.g. the device case area?), what is the max heat flux a typical vapor chamber can support? In other words, will a 100W (Qmax) vapor chamber work for a 1cm² source?
A: As in all VC applications, much of the performance depends on all aspects of the system working together. The final heat exchange will help set up the overall temperature difference in the VC which will define the wattage the evaporator can manage.
Q: What is the flatness of vapor chamber surface (per sq inch) that is in contact with heat source?
A: Flatness of the vapor chamber surfaces is typically better than 0.1mm as built, but this can also be a custom designed for tighter tolerances.
Q: Can the internal wick structure be optimized to help offset gravity losses when used against gravity?
A: Yes, the mesh system is actually a combination of different meshes and can optimized for different applications.
Q: Is there a particular solution for RF power transistors, normally screwed to the heatsink?
A: VC solutions can be applied in many cases, there is not particular solution they are best matched with.