Package attachment to core by means of boltdown method

AN3232

16/26

Doc ID 17594 Rev 3

9

Package attachment to core by means of boltdown

method

9.1

Required hardware

The recommended fastener system consists of:

●

Printed circuit or wiring board (PCB or PWB)

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Core layer, normally copper

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Boltdown STAC package

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Choice of TIM

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2 each of 4-40 UNC-2A (or M3) TORX, HEX, or PHILLIPS cap screws (one for each

end of the package body)

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2 each of spring washers, ID=0.150"(3.81 mm) OD=0.275"(6.98 mm), t=0.015"(0.38

mm), h=0.025"(0.62mm)

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Means of measuring torque

9.2

Considerations

The ideal screw-center spacing for STAC244B and STAC265B packages is 1.1 inch (27.94

mm). This dimension is the same as recommended for legacy "GEMINI" package outlines

such as M244, M252, M265 as well as other familiar equivalents in the industry. Regardless

of the spacing, the key objective is to insure that long and short centerlines of the package

body are centered along and between the screws, respectively. This alignment procedure

insures that the clamping forces are correctly balanced, such that the STAC clamping

design directs pressure down and towards the center of the package body.