Prototyping lead-free solders on hand-soldered, through-hole circuit boards

Conference · Fri Dec 31 00:00:00 EST 1993

OSTI ID:10133084

Vianco, P T ^[1]; Mizik, P M ^[2]

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1. Sandia National Labs., Albuquerque, NM (United States)
2. Allied-Signal Aerospace Co., Kansas City, MO (United States). Kansas City Div.

The lead-free solders 96.5Sn-3.5Ag (wt %), 95.5Sn-4.0Cu-0.5Ag, 91. 84Sn-3.33Ag-4.83Bi were used in the assembly of a through-hole circuit board to determine the feasibility of their suitability in hand soldering processes. Prototypes assembled with 63Sn-37Pb solder were manufactured to serve as control units. Implementation of the lead-free alloys were performed with a rosin-based, mildly activated (RMA) flux and a 700{degree}F soldering tip. A procedure was developed to remove the tin-lead finish from the leaded components and replace it with a 100Sn hot dipped coating. Assembly feasibility was demonstrated for all three lead-free solders. Defect counts were greater than observed with the tin-lead control alloy; however, the number of defects diminished with experience gained by the operator. Visual examination of the solder joints indicated satisfactory wetting of both the device leads and circuit board land with no apparent damage to the underlying laminate nor to the device packages. Cross sections of the lead-free solder joints showed that the were more susceptible to void formation within the holes than was the case with the tin-lead solder. Some cracking was observed at the interface between the Sn-Ag-Bi solder and the copper lands; the relatively high strength of this solder and fast cooling rate of the hand assembly process was believed responsible for this defect.

• Research Organization: Sandia National Labs., Albuquerque, NM (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC04-94AL85000
• OSTI ID: 10133084
• Report Number(s): SAND-93-2586C; CONF-940658-2; ON: DE94007866; BR: GB0103012
• Resource Relation: Conference: 7. International Society for the Advancement of Material and Process Engineering materials processes electronics conference,Parssipany, NJ (United States),21-23 Jun 1994; Other Information: PBD: [1993]
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
36 MATERIALS SCIENCE
METALLURGICAL FLUX
MATERIALS TESTING
LEAD
MATERIAL SUBSTITUTION
ELECTRONIC CIRCUITS
FABRICATION
SOLDERING
TIN BASE ALLOYS
SILVER ALLOYS
COPPER ALLOYS
BISMUTH ALLOYS
MANUFACTURING
WETTABILITY
426000
360101
COMPONENTS
ELECTRON DEVICES AND CIRCUITS
PREPARATION AND FABRICATION