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Components
Improper lead forming resulting in part damage
Failure of this glass bodied diode was attributed to
a crack induced by stresses imposed during the lead
forming process. The operator did not support the part
lead on the body side of the lead during the forming
process. Also the bend in the lead should have been
further from the part body a (minimum of 2 lead diameters)
before the first bend.
Reference :
NASA-STD-8739.3 Parts
Mounting, 8.1 General
6. Lead Bending and Cutting.
a. During bending or cutting, part leads shall be supported
on the body side to minimize axial stress and avoid
damage to seals or internal bonds. The distance from
the bend to the end seal shall be approximately equal
at each end of the part. The minimum distance from the
part body or seal to the start of the bend in a part
lead shall be 2 lead diameters for round leads and 0.5mm
(0.020 inch) for ribbon leads. The stress relief bend
radius shall not be less than the lead diameter or ribbon
thickness. The direction of the bend should not cause
the identification markings on the mounted part to be
obscured. Where the lead is welded (as on a tantalum
capacitor) the minimum distance is measured from the
weld.
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