Saturday, December 19, 2009
Wednesday, December 16, 2009
Surface Finish Pros and Cons
Pros & Cons of HASL | |
Pro | Cons |
Inexpensive | Environment Consequences |
Cu/Sn solderjoint | Poor fine pitch assembly |
Re-workable | Solder bridging |
Widespread availability | Plugged PTH |
Thermal damage to board | |
Not Flat | |
Thick intermetallics | |
Pros & Cons of Immersion Gold (ENIG) | |
Pros | Cons |
Pb Free | Comparatively expensive |
No copper dissolution | Brittle Ni/Sn solderjoint |
Surface contacts | Signal loss at RF frequencies |
Long shelf life | Black-pad, black-line nickel |
Strong PTH "rivet" | Solder Mask "attack" |
Fine pitch assembly | Not re-workable |
Widespread availability | Comparatively complicated |
Pros and Cons of Organic Solderability Preservative (OSP) | |
Pros | Cons |
Least expensive finish | Handling sensitive |
Flat, fine pitch assembly | Poor PTH soldering |
relatively simple process | Shorter shelf life |
Widespread availability | Degrades with multiple reflow |
Cu/Sn solderjoint | No direct thickness measurement |
Pb free | High surface contact resistance |
High productivity at fabrication | Not inspect able prior to assembly |
Re-workable | Exposed copper on final assembly |
Pros and Cons of Immersion Silver | |
Pros | Cons |
Flat, fine-pitch assembly | Tarnish |
Comparatively inexpensive finish | Attack at solder mask interface |
No Pb | Dendrite formation |
Re-workable | Exposed silver can corrode |
Easy thickness measurement | Solder joint microvoid history |
Excellent surface contact functionality | Handling Sensitive |
No degradation with multiple soldering reflow | |
High productivity at fabrication |
Pros and Cons of Immersion Tin | |
Pros | Cons |
Flast, fine-pitch assembly | Handling sensitive |
Comparatively inexpensive finish | Solder mask attack |
No Pb | Corrosion of Whiskers |
Functionality | Difficult thickness measurement |
Multiple reflow soldering | Degredation with time/heat |
Less visible tarnish | Use of thiourea |
Reworkable |