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January 1998

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Subject:
From:
Steve Schrader <[log in to unmask]>
Reply To:
TechNet Mail Forum.
Date:
Fri, 9 Jan 1998 11:16:20 -0500
Content-Type:
text/plain
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text/plain (82 lines)
Alan,

Someone may have already replied with this information and I just missed it,
but
from an assembly point of view, the biggest benefit of the immersion gold
over the HASL
is the flatness achieved on the pads on fine pitch surface mount parts.
This is critical
for 20 mil and below fine pitch assembly yields.

Steve


>Hi Alan,
>
>>From an assembly point of view, the added benefits of switching from HAL
>solder to gold, may not be as strong. The major benefit is eliminating lead
>and the messy HAL operation that pose air quality problems, within the PCB
>fabrication plant. Additionally, the solder joints are all within IPC specs
>and soldering actually occurs on the nickel layer, not on the gold.
>
>Regards,
>Lenny Kurup
>
>On Wed, 7 Jan 1998, Alan Shaw wrote:
>
>> We are wave soldering double sided PHT boards using  a No Clean flux.
>> There is a proposal to replace the hot air levelled solder over bare
>> copper(HAL ) finish with gold flash, about 5u inch thick, over 100u inch
>> of nickel.
>>
>> The proposal would allow us to drop the carbon ink screening requirement
>> used for contacts to a rubber keypad.
>>
>> I see no other benefits to this, only the following problems:- gold
>> contamination of the solder pot and weaker solder joint strength. Does
>> anyone know of any other benefits?
>> Alan Shaw
>>
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