Electronics Forum | Wed Jan 17 20:48:14 EST 2001 | davef
We find that the raw BGA's pad sheared surface has the SnPb solder at various Z heights whereas the assembled BGAs pad leave a smooth layer of SnPb along the pad. Like to understand the cause for the difference. Who could guess? Solder joint streng
Electronics Forum | Thu Jan 18 21:52:24 EST 2001 | arul2000
>>>>Dave, The BGA substrate surface finish is NiAu, while the PCBA pad surface is HASL. The solder ball composition is SnPb 63/37 and the solder paste used on the PCBA is also the same but with 2% Silver.>>> Dave, sorry I don't have the picture with
Technical Library | 2012-12-13 21:20:05.0
First published in the 2012 IPC APEX EXPO technical conference proceedings. We investigated the micro-void formation of solder joints after reliability tests such as preconditioning (precon) and thermal cycle (TC) by varying the thickness of Palladium (Pd) in Electroless Nickel / Electroless Palladium / Immersion Gold (ENEPIG) surface finish. We used lead-free solder of Sn-1.2Ag-0.5Cu-Ni (LF35). We found multiple micro-voids of less than 10 µm line up within or above the intermetallic compound (IMC) layer. The number of micro-voids increased with the palladium (Pd) layer thickness. Our results revealed that the micro-void formation should be related to (Pd, Ni)Sn4 phase resulted from thick Pd layer. We propose that micro-voids may form due to either entrapping of volatile gas by (Pd, Ni)Sn4 or creeping of (Pd, Ni)Sn4.
| https://www.eptac.com/wp-content/uploads/2007/10/webinar_eptac_10_17_07.pdf
| http://etasmt.com/cc?ID=te_news_industry,3561&url=_print
. Ni-Pd as an alternative lead-free solder was introduced by Texas Instruments to the semiconductor industry in 1989. Since then, TI has shipped millions of units that used this "lead-free" lead finish material
