An evaluation of the blind lap joint for the surface mount attachment of chip components

Conference · Wed Jan 01 04:00:00 EST 1992

OSTI ID:7047010

Vianco, P T; Dal Porto, J F

Blind lap solder joints were used to attach leadless ceramic chip resistors to polyimidequartz circuit boards. Hand soldering and vapor phase reflow techniques were evaluated. The solder was 62Sn-36Pb-2Ag (wt.%). The integrity of the solder joints was assessed by microstructural examination and room temperature shear tests. These analyses were performed on as-fabricated circuit boards as well as an those samples exposed to thermal cycling (308 cycles; {minus}55{degree} to 125{degree}C; 6{degree}C/min ramps; 120 min hold periods;) or thermal shock (100 cycles, {minus}55{degree}C to 125{degree}C; liquid-to-liquid transfer; 10 min hold periods). In all cases, microscopy revealed no cracks within the solder joints. The shear strengths of the joints were 13.4 lb (59 N), as-fabricated; 10.5 lb (47 N), 308 thermal cycles; and 14.0 lb (62 N), 100 thermal shock cycles. All values were well within acceptability limits for the particular application. Measurements of the intermetallic compound thicknesses at the copper land/solder interface indicated that the additional heating cycle of the hand soldering step decreased the layer thickness as compared to non-hand soldered joints. The successful implementation of the blind lap joint can provide increased device densities on circuit boards by reducing bonding pad extension beyond the ceramic chip foot print.

• Research Organization: Sandia National Labs., Albuquerque, NM (United States)
• Sponsoring Organization: DOE; USDOE, Washington, DC (United States)
• DOE Contract Number: AC04-76DP00789
• OSTI ID: 7047010
• Report Number(s): SAND-92-0212C; CONF-9208104--1; ON: DE92017045
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
426000* -- Engineering-- Components
Electron Devices & Circuits-- (1990-)
ALLOYS
CRYSTAL STRUCTURE
ELECTRONIC CIRCUITS
EVALUATION
FABRICATION
JOINING
JOINTS
LEAD ALLOYS
MATERIALS TESTING
MECHANICAL TESTS
METALLURGICAL FLUX
MICROELECTRONIC CIRCUITS
MICROSCOPY
MICROSTRUCTURE
OPTICAL MICROSCOPY
SHEAR
SILVER ALLOYS
SOLDERED JOINTS
SOLDERING
TESTING
TIN ALLOYS
TIN BASE ALLOYS
WELDING