LEADED PACKAGES/PARTS-ROUND OR FLATTENED "COINED" LEADS
ROUND OR FLATTENED (COINED) LEADS
This category encompasses discrete component and integrated circuit packages, which share requirements of through hole soldering (NASA-STD-8739.3) and surface mount technology soldering (NASA-STD-8739.2). In typical applications, the leads are formed and bent in a pattern configuration similar to "Gull-Wing" devices. Leads may be in the original round cross-section, or flattened to increase sufrace contact to the land/pad.
See Section 7.01 "Surface Mount Soldering, General Requirements", for common accept/reject criteria.
PREFERRED
The parts are properly oriented to the land pattern, with each lead centered across the width of the land. Lead feet are in full contact with the termination pad, fillets are shiny and concave and heel fillet is evident.
NASA-STD-8739.2 [12.8.1], [12.9.2.a]
NASA-STD-8739.3 [13.6]
PREFERRED
COPLANARITY
The lead's foot should be parallel to, and in full contact with the termination pad.
NASA-STD-8739.2 [7.1]
NASA-STD-8739.3 [8.5]
ACCEPTABLE
COPLANARITY
The maximum acceptable variation in planarity between any portion of the lead foot and the termination pad shall not exceed 0.26 mm (0.010").
NASA-STD-8739.2 [7.1], [12.8.1.h]
NASA-STD-8739.3 [8.5.1]
UNACCEPTABLE
IMPROPER COPLANARITY
Excessive non-planarity may result in open or mechanically weak solder terminations, excessive part tilt, or violate minimum electrical spacing requirements.
NASA-STD-8739.2 [12.8.2.a.10], [12.9.2.b.3]
NASA-STD-8739.3 [13.6.2.a.5], [13.6.2.a.22]
