FAQs for Sockets-SM

Will the silver balls in the SM column disintegrate over multiple cycles?

No, the silver balls do no disintegrated over multiple cycles

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Is solder mask necessary? Is mask defined pad or copper defined pad better for SM socket?

Solder mask is recommended however at a 0.4mm pitch it is better to remove solder mask in the socket area for better connectivity to the silver ball column.

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Does the mounting screws need to be mounted with specific torque? Does the central compression screw need a specific torque?

The mounting screws should be torqued using the supplied hex key until they are finger tight. The recommended torque for the central compression screw is given on the part drawing.

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How often does the SM elastomer need to be cleaned? When do we need to clean the PCB pads?

SM should be inspected and cleaned when there is debris in the socket
Cleaning instructions are given here:
Assembly Cleaning Instructions

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Why do we have to go with custom insulation plate with cutouts as opposed to 5 post backing plate?

The SM elastomer has more force per ball than the SG elastomer, the 5 post backing plate doesn’t provide enough support.

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How can we prevent SM elastomer damage from over compression?

Use the recommended torque, there is an over compression stop built in, however it can still be damaged if you try hard enough.

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When do we need an IC frame that sits on top of the IC package?

An IC frame is needed if your chip has a mold cap

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What is the maximum IC co-planarity that can be accommodated by SM socket?

0.2mm, standard BGA co-planarity

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Can SM elastomer used for HTOL application?

Yes. After 1 HTOL cycle, SM needs to be replaced.

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In case of QFN, how much heat can be dissipated through the SM elastomer?

Thermal resistance of SM elastomer is 3 deg C/Watt

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