Hi Rob
I've made few comments on this line few weeks back , we are currently
validating AL on exactly the same grounds .
That is switching from silicon keypads via carbon pads to AL .
In that touch & skid application ; relatively unstressing , the wear is
about 10 : 1 , where we had 1M cycles on flash gold without sign , we
achieved 100K on AL , sufficient in some application .
The initial resistivity is surprisingly not impaired by the organic
layer .
It does age (oxide) and wear at the same time , than you are on copper .
(Ni below Au holds status that much better , with trace of Au on top,
indirectly by economics of plating it is a hard gold , not pure, working
for you again )
I'll try to find the charts & graphs , AL x NiAu .
At this moment we stick with NiAu , after years in telecom we found the
CuNiAu bonds ideal laminate for contact within economic and process flow
of assembly , previously we did the same ( selective plating -
overdesigned ) where we found just what you did , = paid dearly in more
ways than one by working the "old" ways .
The problems you are describing , apart obviously being the bond nature
perhaps also indicate the useless and expensive deposits .
Therefore : up to 50K - 100K you have reasonable chance ON KEY PAD
application only .
Other applications like slide action fingers and seriously mechanical
switching would not hold with AL in long term ;
life test for short term .
Despite the fact the AL's solderability is miles ahead of NiAu , I
personally thing NiAu is the most versatile surface, in the flash form
even cheaper than HASL , with concrete future ahead . Most of the
mobiles for example have direst solder & switch on NiAu , working in
extreme conditions in every aspect ( volume, both shocks, life span,
etc.)
Let me know your address , I have few spare test boards with switch
lands in AL ; send them over and see yourself .
Pack you couple of A4 sizes double sized boards for solderability (or
wearability) tests as well .
Alpha Metal's themselves do not recommend AL for switching , after tests
I start to almost believe them .
See you Rob
paul
Paul Klasek ; ResMed ; http://www.resmed.com
>----------
>From: Rob Emery[SMTP:[log in to unmask]]
>Sent: Wednesday, 25 March 1998 1:16
>To: [log in to unmask]
>Subject: [TN] AlphaLevel as replacement for Electroplated Nickel Gold
>
><<File: ATT00299.html>>
>We've recently had some problems with flaking of gold plate on keypad fingers
>on a pcb.
>
>Consequently, we're considering changing the finish to AlphaLevel, although
>we've been unable to find any major examples of companies who are using
>AlphaLevel 'unsoldered' in this type of application.
>
>Does anyone have any experience of the long term problems we might encounter
>if we make this change, eg degradation of contact causing erratic keypress
>operation?
>
>Regards
>
>Rob
>
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