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Maybe someone has experience in this field.

I'd like to overmold a PCBA, which has SMT components, with a low pressure molding process. I am concerned about the temperature of the hotmelt material when it reaches the PCBA. The temperature should be between 200°C and 215°C.

Does anyone know if this material temperature could be a problem for the electronic components? Do I have the risk that the solder melts? Is this stress too harmful for the components?

I am not quite sure if the components will be able to withstand this temperature or if I should take as a reference the reflow temperatures of the components.

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    \$\begingroup\$ What soldering temperture profile do the component allow according to the datasheets? As for will it melt solder, that is another obvious thing to get from the specs. Look up the melting point of whatever solder you are using then compare it to 215 degC (that really should have been obvious). All that said, this doesn't sound like a good idea. That sounds like a lot of heat for a long time. \$\endgroup\$ – Olin Lathrop Feb 11 '14 at 14:07
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    \$\begingroup\$ There's a reason there are specially developed "potting compounds" for this purpose that DON'T involve such high temperatures. \$\endgroup\$ – Brian Drummond Feb 11 '14 at 14:44
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Each component's data sheet will have to be examined for temperature ratings. If the component can handle 215C in non-operational state, then you should be fine. If it's maximum non-operational temperature is below that, then you might look into the solder reflow profile, which may allow short periods of high temperatures. The profile will tell you for how long you can maintain a high temperature without violating the manufacturer's specification. If you can keep your potting process temperature under the reflow curve over time, then you should be fine. Some components are rated for only one pass through a reflow process though, so make sure to read the fine print.

If a component doesn't fit your needs, you can look for a replacement that does, or you can discuss your requirements with the manufacturer to find out what additional information they can give you on temperature resistance.

Alternately, talk with your potting supplier about lower temperature potting compounds, or change your process to allow for a conformal coat to provide enough thermal insulation that the components themselves experience a lower temperature.

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In answer to your question, yes I know those temperatures could (would) be a problem for some components. Many SMT parts would survive just fine, but all it takes is one or two problem ones and your scrap goes up and reliability goes down the WC.

When cooling, the differential CTE (coefficient of thermal expansion) can put enormous forces on parts, shearing off leads and causing other damage. Less rigid molding materials are much better than more rigid ones.

I assume this is a serious application requiring water resistance or other environmental protection since the process you're talking about involves mold NRE and other costs. You should talk to the applications people at the material suppliers and contract manufacturers for application guidelines.

For example, these guys: http://cavistmanufacturing.com/low-pressure-molding/ enter image description here

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