Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Dale

#10569

Optimizing PCB for SMT | 16 July, 1999

We are converting from COB to SMT on a product line and want to optomize the PCB as far as Laminate, plating, passivation etc. This is a high temp application 150C. We are presently using BT Laminate but would like to get away from this. We are looking at high temp FR4. Any concerns? We are trying to decide between NiAu and HASL (components are 0.025" pitch) what are advantages and disadvantager of these? Not a lot of time has been spent with regards to passivation, any suggestions? Any help would be greatly appreciated.

Regards, Dale

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Glenn Robertson

#10570

Re: Optimizing PCB for SMT | 16 July, 1999

| We are converting from COB to SMT on a product line and want to optomize the PCB as far as Laminate, plating, passivation etc. This is a high temp application 150C. We are presently using BT Laminate but would like to get away from this. We are looking at high temp FR4. Any concerns? We are trying to decide between NiAu and HASL (components are 0.025" pitch) what are advantages and disadvantager of these? Not a lot of time has been spent with regards to passivation, any suggestions? | Any help would be greatly appreciated. | | Regards, | Dale | Dale - I assume you mean that the product operates in a 150C environment. This may be too hot for Getek or some of the newer laminates (Rogers, Nelco, GIL) but I'm sure the suppliers can provide that data. If you can use one of them, be sure your fab board shop has experience with the drilling process, because I have heard there can be some surprises there. NiAu generally works well as long as you don't need to install a compliant-pin connector on the module. The pros and cons of HASL have already been discussed (and cussed) in lots of articles. You might consider an immersion-Sn finish like the Dexter FST. Also, your solder alloy will obviously have to be suitable for your operating temperature. I hope this helps.

Glenn Robertson Alcatel USA

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