Critical Component Requirements for Vapor Phase Soldering Leadless Components on Circuit Board Assemblies for Military Electronics

Hagge, J.K.

doi:10.1109/tchmt.1983.1136200

Cited by 6 publications

(1 citation statement)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Although the list of mechanical properties of Au in Sn/Pb solder tested over the years is impressive, i.e., UTS [ 11], bend strength [11,27], hardness [40], shear strength [11,13,27,96], peel strength [9,11,21,24,25,37,51,53,72], wettability [10,13,40,42,53,66,83,92], impact strength [11], thermal cycling [24,34], torque [24], shock [24,34], and vibration [24,34], data on isothermal creep properties is lacking. This lack ',"NIIl'lll _"_,,,rr",l,'"l,"llfr "',l"tll' "'_"' '_,"",1111 ...... ,r""_"rI!l"F" .,_r_l'l"'Illr _rlINIl"'"'llr'l r lllll,'ln'""_011"'lllll TM q'"l_'r'"l'l!l_IIIl'l_l I of creep test information is disturbing, since creep is the major deformation mechanism at room temperature and above for the eutectic and near-eutectic Sn/Pb alloys, as these temperatures are greater than half the absolute melting temperature of such alloys (Tru = .…”

Section: Creepmentioning

confidence: 99%

The effect of low Au concentrations on the properties of eutectic Sn/Pb

Kramer¹

1992

View full text Add to dashboard Cite

The objective of this study was to detem_ine the effects moderately low Au concentrations ('_:10 wt%) have on the mechanical properties and the microstructure of an eutectic Sn/Pb alloy. Vibration (60-90 Hz swept sine wave Ibr 30 hours) and thermal cycling (0'C-110"C for 1450 cycles) reliability tests were performed on fine pitch leaded chip carriers using eutectic Sn/Pb solder on PCBs (printed circuit boards) with 0 gin, 5 lain, 10 girt, 20 gin, and 50 gin nominal Au thicknesses. Testing was also performed on double shear creep specimens consisting of arrays of regular pitch joints with nominal Au plating thicknesses the same as for the reliability joints. Two interesting microstructural features were observed. First, there was a dramatic increase in the number of joints containing voids with increasing Au concentration, an effect more pronounced in the creep joints _han in the reliability joints. These voids tended to coalesce and grow during rework simulation of the reliability joints. Second, AuSn4 intermetallics present in the toe of the 4.8 wt% (50 lain) Au vibration joints rotated from their initial, generally vertical (where vertical indicates perpendicular to the surface of the PCB metallization), solidification positions to roughly horizontal (where horizontal indicates parallel to the plating surface) orientations during rework simulation and during aging of the parts. In addition, the AuSn4 intermetallics in the toe of the 4.8 wt% (50 lain) • Au reflowed joints were observed to have rotated after vibration testing. No failures of the joints were observed in either the vibration tested or the them'_ally w cycled specimens for any of the conditions tested. Cracks formed in some of the vibration tested specimen joints under the heel of' the gull-wing lead at Pb-rich phases. Thermally cycled specimens showed evidence of eutectic microstructure and intermetallic coarsening without crack formation. Creep tests showed a loss of the superpla.sticity regime in eutectic Sn/Pb alloys with even the lowest Au concentration tested of 0.2 wt% Au_ Intermetallic rotation was not found to be a fac:or in crack propagation, but void presence was. Cracks tended to form in joints containing voids before forming in void-free joints. Crack propagatioli followed Sn/Sn grail; boundaries at.

show abstract