THERMAL NEWSLETTER l AUGUST 2021
A MESSAGE FROM OUR CEO

Things continue to go well at ASC, and we are continuing on a solid growth path despite having to meet the challenges of the day from laminate shortages to labor shortages to the Delta wave of Covid. 
I would say that the thing we are the most proud of is how our team has come together to meet all of these challenges, working tirelessly to make sure that we do all that we can to keep our customers satisfied and happy.

We continue to expand our technology by adding more high technology equipment from a VEGA Ultra R6DL series PCB blind routing machine to HIOKI 1116-74 and 1270 Electrical Testers, as well as a new Orbotech AOI. We also have increased our fine line capabilities by adding the Averatek’s A-SAP process.

On another note, one of the fastest growing segments of our marketplace is Thermal Management. We want to remind all of you that Thermal Management, including using special high end thermal materials as well as metal backed technology, is one of our strongest areas of technology. We even have our own in house milling machines for fabricating heatsink metals for our Thermal PCBs.

We like to say that we were in the Thermal Management business before it was cool!

One last thing, unfortunately because of the newly rising numbers of Covid cases, our factory has returned to a full CDC complaint status including mandatory masking and social distancing. We don’t like it but right now it is a fact of life. Please keep this in mind if you are planning a visit to our facility in the near future.

Meanwhile please stay safe and well and as always thank you for your business.

Anaya Vardya
President and CEO
American Standard Circuits
Thermal Properties Explained

A thorough understanding of a number of different thermal properties is needed to be able to design the appropriate IMPCB solution to a thermal condition.
Thermal Conductivity

Measurement of the ability of a substance to conduct heat, Measured in W/mK.
A material property, meaning that it does not change when the dimensions of the material change, as long as it is made up uniformly.
For example: the thermal conductivity of a cm3 of gold is exactly the same as the thermal conductivity of a 100m3 of gold.
Generally obtained in the industry using one of two tests, either the D-5470 test, or the E-1461 standard ASTM tests.
The D-5470 test measures the thermal impedance in Ccm2/W (Celsius, centimeters squared per Watt) of the sample and gets a value of the thermal conductivity through the relation:

Thermal Conductivity = Thermal Diffusivity * Specific Heat Capacity * Density


Thermal Impedance

This is the opposite of thermal conductivity. It is a measurement of the ability of a material to oppose the flow of heat, so from a PCB point of view, we want this value to be low. The lower the thermal impedance, the quicker heat flows through the PCB and to the heat sink where it is dissipated.

Its value is dependent on the thermal conductivity of the material and its thickness; in other words, this is not a material property, but is an object property, as changing the thickness of the material will change this value. Saying that, changing the area of the material will not change this value (as long as the thickness stays constant).
For example: the thermal impedance of a sheet of laminate is the same as the thermal impedance of a cut piece of the laminate, say a cm2 of it. Whereas the thermal impedance of a sheet of gold of 1mm thickness is different to the thermal impedance of a sheet of 2mm thickness.

This is generally obtained using the D-5470 test mentioned above and relates to the thermal conductivity via the relation:

Thermal Impedance = Thickness / Thermal Conductivity


Thermal Resistance

Thermal resistance (measured in Kelvin / Watt) is basically the same as the thermal impedance. The difference is that it takes into account the area of the sample as well as the thickness and conductivity.
Changing either the thickness or the area of the material will change the associated value of the thermal resistance.

Thermal Resistance = Thickness / (Thermal Conductivity * Sample Area)

(excerpted from Chapter 2 of "Thermal Management: A Fabricator's Perspective." A link to download your own free copy is directly below.)
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UPCOMING WEBINARS

Performance and Reliability Benefits
of Thin-Film Resistive Foil
August 25, 2021
10:00 am to 11:00 am (CST)
This live webinar will be hosted by Bruce Mahler, VP & GM Ohmega Technologies. In this webinar Mr. Mahler will provide an overview on thin-film resistive foil technology and provide insights on how the technology is proving to be a critical tool in solving today’s complex PCB design challenges.

All Our Past Webinars Are Available On Demand

You Can Watch Any Or All Of Our Five Thermal Related Webinars Here:
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IMPCBs:
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Common Applications
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