Copper only (OSP) 22.5% 23.0% HASL 55.3% 40.6% Lead-free HASL 23.0% 37.3% SnPb
plate and reflow 18.9% 12.3% Im.
There was considerable debate and distress over what alloy would replace dependable SnPb
. Considerations included reliability, process compatibility and cost.
For example, there are cases in which a project specification calls for SnPb
or eutectic solder paste, but the assembler receives BGA components with Pb-free solder balls.
"For companies that manufacture products that must have high-reliability and long-service-life, the rationale for staying with SnPb
assembly is very clear--the reliability of Pb-free assembly has not been sufficiently demonstrated for long-life, mission-critical applications," said Ken Stuchlik, SCN processor and I/O technical manager for Lucent Technologies, and co-chair of iNEMI's SnPb
BGA Availability Task Group.
THROUGH-HOLE AND SURFACE mount electrolytic capacitors can pop or blowout during operation or soldering in a SnPb
or Pb-free process.
It is offered in a SnPb
BGA package and is stipulated over the complete military temperature range (-55AC to +125AC).
or SAC 305 solder preforms were placed between two ENIG coated 1.25" x 0.375" x 0.008" copper-oxidized and non-oxidized substrates and reflowed in air (FIGURE 1).
Compared with SnPb
systems, Pb-free joints are characterized by larger and a higher amount of voids.
alloys are usually run at temperatures of 250[degrees] to 260[degrees]C, whereas SnCuCo alloys are processed at temperatures in the range of 260[degrees] to 270[degrees]C and SAC305 at 255[degrees] to 265[degrees]C in HAL, wave and SMT soldering equipment.
This can occur, for instance, when raw materials for fabrication are optimized for SnPb
technology, yet the PCB is assembled using Pb-free technology.
In working to develop this unique alloy, it was critical to ensure processability that was much like a traditional SAC alloy, but temperature cycling performance that was superior to SAC and consistent with or better than conventional SnPb
solders, explains Mark Currie, Global Product Manager for Henkel.
High-speed connectors often have finished PTH nominal diameters ranging from 0.46 to 0.60mm and, in accordance with RoHS, will have PTH finishes other than SnPb
. These finishes may include immersion tin or electroless NiAu and require PTH tolerances often more stringent than those associated with SnPb