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Conformal Coat Thermal Conductivity

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Cecil

#49108

Conformal Coat Thermal Conductivity | 18 April, 2007

We currently have an assembly that we have to mask the surface of several (24)SMT components where thermal compound is applied at a latter operation. These component packages vary from BGA's to QFP's. After the thermal compound is applied the PWA is then attached to a heat sink plate. Conformal coating used is Humiseal 1B31. I am trying to get thermal conductivity info from Humiseal but in the mean time thought I would see is any of the experts here have dealt with this in the past.

I am just wondering if it is really necessary to mask off the components. Is pretty labor intensive and would like to eliminate this step if possible. Does anyone apply thermal compound over CC then mount your heat sinks? Has anyone performed any experiments in the past to determine if conformal coating reduces thermal transfer efficiency?

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#49111

Conformal Coat Thermal Conductivity | 18 April, 2007

We use 1B73 Acrylic and coat right over an IBM processor which gets a heat sink mounted on top. Never had an issue after 5 years of production. Dont forget to post if you find anything out though.... JD

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#49122

Conformal Coat Thermal Conductivity | 18 April, 2007

Thermal conductivity [W/m-*C] * Conformal coating [AR, ER, UR]: 17-21 * Epoxy molding compound: 0.6

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cecil

#49130

Conformal Coat Thermal Conductivity | 19 April, 2007

Dave, Where did you find that info?

having a hard time getting info from Humiseal.

Thanks

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#49131

Conformal Coat Thermal Conductivity | 19 April, 2007

Look here: http://www.humiseal.com/cc_handbook/cchandbookpage4.html

Maybe those dead-butts at Humiseal should pay us

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cecil

#49134

Conformal Coat Thermal Conductivity | 19 April, 2007

Thanks for the link!!! Don't know why I couldn't find it. Seems like every day is Monday this week!!

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cecil

#49144

Conformal Coat Thermal Conductivity | 19 April, 2007

Dave, When we converted the Humiseal thermal conductivity info into W/m-*C we came up with .167 - .209.

Did we do somthing wrong with our conversion?

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#49151

Conformal Coat Thermal Conductivity | 19 April, 2007

reflow oven profiler

SMT in-printer dispensing