THROUGH-HOLE SOLDERING
MECHANICAL ASSEMBLY, POWER SEMICONDUCTORS & HEATSINKS
power semiconductor
MECHANICAL ASSEMBLY
POWER SEMICONDUCTORS & HEATSINKS

Power semiconductors and heatsinks present a unique challenge to the printed wiring board (PWB) designer. Power devices are capable of producing significant amounts of heat and are typically of greater mass than other components.

Body types vary from ceramic/ epoxy/ sandcast bodied and axial components requiring thermally-conductive staking and/or heatsinks; metallized housings with mounting tabs/feet; to axial, radial and multi-conductor/flatpack components with intergral heatsinks.

electrical clearance integral heatsink component

ACCEPTABLE

ELECTRICAL CLEARANCE (C)

The mounting of hardware shall not violate minimum electrical spacing requirements.

Best Workmanship Practice

ACCEPTABLE

INTEGRAL HEATSINK COMPONENTS

Component and mounting hardware are installed per engineering documentation. Heatsink body and dielectric are undamaged and in full contact with no air gaps.

Best Workmanship Practice

power diode power tab

ACCEPTABLE

POWER DIODE INSTALLATION

Component and mounting hardware are properly installed.

Best Workmanship Practice

ACCEPTABLE

POWER TAB INSTALLATION

Component and mounting hardware are properly installed.

Best Workmanship Practice

NASA WORKMANSHIP STANDARDS
NASA logo Released:
06.27.2002
Revision:
Revision Date:
Book:
6
Section:
6.04
Page:
1










THROUGH-HOLE SOLDERING
MECHANICAL ASSEMBLY, POWER SEMICONDUCTORS & HEATSINKS (cont.)
power transistor damaged heatsink

ACCEPTABLE

POWER TRANSISTOR INSTALLATION

Component and mounting hardware are properly installed.

Best Workmanship Practice

UNACCEPTABLE

DAMAGED HEATSINK

Heatsink body exhibits gouging and deformation, resulting in exposed base metal. Reliability issue.

Best Workmanship Practice

improper mounting hardware installation sequence improper mounting hardware installation sequence

UNACCEPTABLE

IMPROPER MOUNTING HARDWARE
INSTALLATION SEQUENCE

Mounting hardware is improperly installed: the toothed surface of the flat washer is in contact with the insulator, which may result in insulator cut-through and reduced compression pressure.

Best Workmanship Practice

UNACCEPTABLE

IMPROPER MOUNTING HARDWARE
INSTALLATION SEQUENCE

Mounting hardware is improperly installed: the lock washer is located between the terminal lug and component case, rather than between the terminal lug and the nut.

Best Workmanship Practice

NASA WORKMANSHIP STANDARDS
NASA logo Released:
06.27.2002
Revision:
Revision Date:
Book:
6
Section:
6.04
Page:
2





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