Below are the questions asked during the event, along with their respective answers.
Q: So what guidance to choose between seemingly similar GR80 and PG80?
A: Materials are similar with respect to bulk conductivity, but they differ in other mechanical characteristics. If you are not worried about compression and you need a stiffer resilient material then GR80A is good. Otherwise, PG80B is typically a better option due to the low hardness.
Q: The compression range is in percentage, is there any absolute pressure value accordingly?
A: The absolute pressure at each compression ratio is listed on the datasheets. We can also provide you with a custom test report.
Q: Can you give some insight as to why Fujipoly chose a compression speed of 5mm/min(.2in/min)? I the typically PWA assembly process the compression speeds are typically much higher.
A: Compression in manufacturing can vary. We chose 5mm/min as it is about 50% compression of our thickness pads in 30 seconds. There is no specific technical reason for it.
Q: Are these Bulk thermal conductivities or the effective thermal conductivities that we get in TIM tests?
A: These are the bulk conductivities.
Q: Did Fujipoly observe any performance change between TIM tester results and actual applications?
A: Other than heat flux that does not flow through the TIM the thermal resistance is in line with what we report.
Q: How do you estimate bulk K vs. the thermal-contact resistance at each interface?
A: We use ASTM 5470D to calculate thermal conductivity based on thermal resistance. We also use other methods such as hot wire and hot disk.
Q: Do putties have similar dielectric properties compared to standard gap pads?
A: The dielectric properties are similar. Just keep in mind the putties are easily compressed and may be more susceptible to puncture and voltage breakdown.
Q: The putty pads will spread as you compress? So do you have to undersize the pad dimensions? How much should you undersize them?
A: The pads will expand volumetrically. It is a good idea to undersize in order to lower cost and reduce the compression force required.
Q: Can the putty type materials be stacked?
A: Yes, putty materials stack very well with little to no difference in performance between a stacked sheet and a homogeneous sheet.
Q: Can we order GR130 and GR80A directly from the site or are they supplied based on the order(B2B)?
A: You can order direct from Fujipoly America.
Q: Have you done any load-displacement tests at different temperatures? Do TIMs show different mechanical response at different temperatures?
A: We have not but there is likely some change in displacement stress. At room temperature +/-10C it would be negligible.
Q: How does a putty hold up under dynamic loading?
A: Putty pads have little to no elasticity and undergo plastic deformation so they will not recover. They do have very good adhesive characteristics so they can tolerate some vibration and thermal expansion.
Q: Can you talk more about the performance of putty-type vs silicone elastomer-based TIM over time?
A: Thermal performances would not vary from putties to non-putties but compression range varies a lot. Putties can be compressed beyond 60% but non-putties will create a lot more stress above 35%.
Q: Have you measured the force required when the plattens are larger than the gap filler
A: We have done this kind of testing both with platens of equal size and of sizes larger than the materials.
Q: How is thermal stability in a wide range of operation temperatures? Any hardening cracking issues?
A: All of our materials are put through 1,000 hours of durability testing which includes elevated temperatures, low temperature, high relative humidity, and cycles of heat shock from -40C to 125C. The materials are required to exhibit little variation over the course of testing. Some materials harden at prolonged elevated temperatures but not enough to impact the thermal performance when used according to our recommendations.
Q: What is the minimum bond line thickness recommended for the putty material? Would < 0.5mm work?
A: Bond lines under 0.5mm can be achieved. We can provide some more in-depth information for particular materials.
Q: It seems like some of your materials are completely plastically deformable (putty) and others offer some form of elastic resistance. Can you speak a little more about how much force is required to compress the plastically deformable materials? For instance, some might be “thicker” and some might be “softer” but both compress.
A: Yes, the putty materials are plastically deformable. The force usually has a relationship with the density of conductive fillers. The force can vary depending on the surface area, compression ratio, and compression velocity.
Q: The thermal conductivity and thermal resistance are tested based on Fujipoly modified methods, is there any deviation from the conventional ASTM 5470 test method?
A: We follow the method as closely as possible. The modifications stem from the customization of measurement equipment and test setup. The nice thing about the 5470 test is that it can be reproduced using a wide range of equipment and sampling methods.
Q: How many thermal cycles can the putty type TIM go through? And by how much does the thermal resistance increase over multiple cycles?
A: Our durability test performs 30-minute cycles of -40C to 125C over the course of 1,000 hours with no change in thermal resistance.
Q: Are there low molecular siloxane problem in putty type?
A: The content of low molecular siloxane in our materials is very low, to begin with. We pass all of our products through Nasa ASTM E595 test for outgassing which measures condensable and mass loss of the compound.
Q: What is the operating temperature range for these putty pads?
A: Recommended -40C to 150C. -60C to 200C is the maximum recommendable operating temperature for short durations.
Q: Can you speak more to the anisotropy of some materials? ASTM5470 doesn’t consider anisotropy so doesn’t that mean it isn’t really a good test for modern materials?
A: Our materials are not anisotropic. I think the ASTM method is a fine analysis of thermal resistance and calculating bulk conductivity. It can easily be put together in a lab using different types of equipment and sample sizes. We are using more Hot Disk method these days because of the consistency of the results especially as conductivity gets higher.
Q: Could you please give a few use case examples of putty in automotive applications?
A: Putty materials have been popular in the control units of infotainment and communication systems of the vehicles due to the use of die-cast enclosures and their accompanied mechanical tolerances. I can also think of some camera applications which are part of the ADAS systems of the vehicles.
Q: You showed how it settles over time. Do you have data of any variation in thermal conductivity for thermal cycling, as the settling/compression at high temp may be more?
A: All of our materials are put through 1,000 hours of durability testing which includes elevated temperatures, low temperature, high relative humidity, and cycles of heat shock from -40C to 125C. The data is available on our technical datasheets.
Q: Are samples of putty type TIM readily available for evaluation?
A: Samples are available upon request. Our website is a handy resource for data and sample requisition all in one.
Q: are the Zarcom products rated for outdoor applications (-40C to 70C)?
A: Yes, the recommended operating temperatures are typically around -60-150C.
Q: What is the typical shelf life of Fujipoly TIM’s
A: Depends on the type of material. The solid film and gap filler types can be up to 5 years depending on construction. Dispensable materials will vary from 6-18 months depending on the type of package.
Q: Is there any product suitable for 5G/ IoTs application?
A: Absolutely. Our products are widely used by the telecom industry. We have high-performance gap fillers for the most demanding needs as well as general-purpose cost-effective solutions.