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Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


HAL vs. Silver Coated

John Sims

#4680

HAL vs. Silver Coated | 10 March, 2000

We're quoting out a new board design, and one of the prospective suppliers is pitching a silver coating process over hot air leveling. We haven't had experience with boards of this type, and I am concerned about any processing issues that may come up. We are currently using a no clean process. Would these boards require post solder cleaning? Would our soldering temperature have to change (We're at 485)? Would we have any need to change our preheat profiles? Our purchasing department is sold on it because we would get a good price, but I can't blindly listen to the salesman.

Any advice would be a great help.

Thanks,

John

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#4681

Re: HAL vs. Silver Coated | 10 March, 2000

Hi John,

we had one shot with silver coated PCBs. With "no clean" and no changes in process parameters ( we had no input on necessary changes from the boardhouse ) we encountered wetting problems in the first reflow soldering process. Later it was said that something with the coating at that time wasn�t perfect. Nevertheless we decided not to work with that coating nor do I know of any companies we are associated with that they work with this coating. I would check - with the board house if they have any information on process specification especially compared to your current processes - a sample lot in your assembly checking solderability through all stages including rework

M2c

Wolfgang

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Peter Barton

#4682

Re: HAL vs. Silver Coated | 17 March, 2000

John,

I have had previous experience of immersion silver coated PCB's in place of HASL coated type using no-clean processing with little or no problem at all. All of the process parameters were left unchanged.

There is a very minor difference in the amount of wetting compared to HASL but much less than using an electroless nickel/immersion gold finish (assuming you use the same solder paste/flux type and process settings).

Benefits of the silver process are the flatness of the pads (same as gold). Also the bare PCB manufacturing process is less aggressive as the coating process does not require the high temperatures used in HASL and the process chemicals are much less environmentally harmful than those used when applying gold.

I understand that the shelf life is pretty good too.

Pete B.

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