I'm not a PWB shop person, but I've supported many in the past. I'm not
sure the shops are set up for 0.5um resolution. I'm not comfortable with
those Beuer polish set ups for 1um resolution, but I don't know the product
in detail. I'd like to know if there is a need and I'll send in my
suggestions (as one who has done microscopy 1nm-10um samples on a research
basis for years). But I'll save that lengthy verbage for later.
I've found cross-sections can be very misleading because of metal smear at
thicknesses of ~1um. It is critical that the last polish be done parallel
to the interface of gold/nickel with much care. I'm not a fan of the XRF
technique because it relies on mathematically modeling your metal system-
perfectly flat interface, no thickness variations over sample area, and the
interactions for fluorescence in each layer.
I suggest you do some hard work up front, but then it will become routine
and easy later: find a selective etch for gold or nickel (you'll probably
have more luck with the latter) or one that highlights the interface (takes
advantage of that mismatch of metal-metal interface...back to that wire
bonding story, Inge!). This also means, you can't just put your sample on
the automatic polisher without paying good attention to the last step. You
may do it by hand using 600 grit (I think that is per square inch) followed
by 1000 grit sand paper. A true polish (<0.2 um in your case) may be
needed, but I'd try to avoid it because it's a hassle to keep a clean plate
for that. And don't contaminate your polish plates with dirty parts
holders.
-----Original Message-----
From: TOE /Torben Østeraa <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Tuesday, October 05, 1999 1:05 AM
Subject: Re: [TN] Measurements of Gold over Nickel
Ingemar, and others:
While we're on the subject:
We also use 'stoneage' technique to inspect nickle/gold
plating from sub-contractor. He's using some sort of
non-destructive method to verify thickness, and we do not
always agree on the result.
Apart from the obvious problem of thichness variation over
the panel, is there a predictable difference in thickness
found using different techniques?
Regards
Torben Østeraa
Printca AS
Denmark
>>-----Original Message-----
>>From: Ingemar Hernefjord (EMW)
>>[mailto:[log in to unmask]]
>>Sent: Tuesday, October 05, 1999 8:42 AM
>>To: [log in to unmask]
>>Subject: Re: [TN] Measurements of Gold over Nickel
>>
>>
>>Edward,
>>we have found that there is nothing better than ordinary
>>stoneaged crossectioning and study in a metalographic
>>microscope. In mass production, samples are usually enough.
>>Such examinations don't take time and they tell a lot more
>>than betascope. And...you can store the images and have a
>>look back up and then.
>>Regards
>>Ingemar Hernefjord
>>Ericsson Microwave Systems
>>
>>
>>I am looking after alternative method of measuring of
>>electroplated Gold
>>over Nickel for production .Gold thickness is in range from
>>0.75 to 2.5
>>microns.
>>I have in my plant beta scope with Promethium source with lot
>>of problems.I
>>have also XRF,that can not be placed in production area.
>>Any sugestions?
>>
>>Edward Szpruch
>>Eltek , Manager of Process Engineering
>>P.O.Box 159 ; 49101 Petah Tikva Israel
>>Tel ++972 3 9395050 , Fax ++972 3 9309581
>>e-mail [log in to unmask]
>>
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