Someone recommended us the Immersion silver for Al wire bonding. Does
anyone use the immersion silver (Alpha Level) for Al wire bonding pads? Any
test data for long term stability and reliabiity you can share? Any
humidity related issues (electro-migration)? any interface issues (conformal
coating compatibility)? Thanks in advance.
Best regards,
jk
At 09:53 AM 6/9/99 +1000, you wrote:
>Hi Mike
>
>As I said ; I'm stuck with NiAu because of the switch pads ;
>I tested the Alpha Level(which Neil made sure he did not mention)just from
>curiosity, for life (vacuum packed); solderability ; and abrasion, on
>switching ; all in line with what Kathy reported .
>However ; being as good as it is (good enough); I agree with Neil as well it
>does tarnish more readily than tin .
>Mind you again ; I did not find the tarnish (greasy fingerprints mainly)
>impeding the solderability to noticeable degree.
>
>It must be actually a real hasl of a pick even from fab folks investment
>point of view (crossroads) ;
>as here one major house invested to silver ; while other came to me with tin
>samples ; and my HK buddy is doing nothing but gold .
>
>The solid deposit I went through ages back ; again the switching precluded
>me from implementation ;
>it must have it's uses (some positive feedback sits in archives); not for
>efficiency freaks like me .
>
>It really depends on applications ; on mass telephone phenolics the organic
>copper did fine as well .
>There 's nice and simple "finish line" page 13 in IPC Review (June 99) ;
>giving the trends vectors so far .
>
>See you
>
>Paul Klasek
>http://www.resmed.com
>
>-----Original Message-----
>From: [log in to unmask] [mailto:[log in to unmask]]
>Sent: Wednesday, June 09, 1999 12:38 AM
>To: 'IPCtechnet'
>Subject: Re: Immersion Silver [HASL Alternatives] <IPC TN>
>
>
>Kathy, Paul-
>
>We've started looking into Immersion Tin (Dexter's FST) and solid solder
>deposit [Masktek, in Anaheim CA, and SiPAD [licensed from Siemens], through
>board supplier MPCS, in Round Lake Beach, Illinois). I have to admit to not
>considering/knowing about immersion silver.
>
>A paper on immersion tin was presented at IPC PC EXPO'99, at Long Beach
>earlier this year, co-authored by Dexter Elec Materials and DSC Alcatel
>(TX). The test data presented by the user is worth checking out.
>
>Have you considered these as alternatives to HASL [what an appropriate
>acronym!]? In HASL's defense, "...nothing solders like solder.", an
>observation from a supplier of an alternative finish. And, HASL has served
>it's purpose up to the realm of fine pitch SMT patterns [pitch > 0.5
>mm/.0196.. inch].
>
>NOTE: the May 1999 issue of Circuits Assembly Magazine has a concise, well
>written article on alternative finishes, by Matt Kehoe of MPCS.
>
>
>Check out sites...
>
>http://www.dexelec.com/pwb/products/advanced_process/plating_tech.html
>
>
>
>http://www.midwestpcb.com/sales/fullnasa.htm
>
>
>
>http://www.masktek.com/our_products.htm
>
>
>-Regards,
>
>Michael Alderete
>Aerojet, Azusa CA
>
>
>
>you wrote...
>----------------------------------------------------------------------
>
>Date: Mon, 7 Jun 1999 16:56:07 -0700
>From: Paul Klasek <[log in to unmask]>
>Subject: Re: Immersion Silver
>
>Concur with Kathy on all points .
>On the switching (contact points) we tested with no resistivity changes on
>carbon pill mounted in silicon pad action up to 50K cycles before we got
>down to copper .
>On the contact however ; once you wear the organic from top ; it does
>oxidize ;
>therefore unsuitable for more repeated low force low current switching . OK
>for edge con's in commercial applications , just.
>
>Which was the only reason why we keep NiAu ; which is not such a dream to
>solder ; as we have the silipad switching .
>
>Paul Klasek
>http://www.resmed.com
>
>-----Original Message-----
>From: Kathy Palumbo [mailto:[log in to unmask]]
>Sent: Tuesday, June 08, 1999 9:35 AM
>To: [log in to unmask]
>Subject: Re: [TN] Imersion Silver
>
>
>Charles,
>
>I did an extensive analysis (temperature cycling, vibration, humidity, lead
>pull testing, and cross sectioning) on completed assemblies with this
>coating on the PCB prior to approving it as an alternative coating to HASL.
>I found that the coating is a direct drop in replacement to HASL. In other
>words you can use the coatings interchangeable with no problems. The
>storage life is equivalent to HASL. The coating has no special handeling,
>or storage requirements. Keep in mind that if you are using the coating on
>your PCB as a contact point (i.e. a KEY BOARD) then the silver immersion
>coating is not the way to go (too thin). If you intend to solder to the
>coating, then it is not a problem.
>
>We have been using silver immersion as an alternative coating to HASL for
>more than 1 1/2 years with no problems. The wetting action of the solder to
>the pads was better than HASL coated PCB's, and the cross sectioning of
>several solder joints showed an even better fill of the solder under the
>leads than with HASL (which had quite a few voids). The biggest advantage
>was the elimination of bridging issues on fine pitch devices caused by the
>variance of the HASL deposit. We have virtually eliminated all of our
>bridging issues on fine pitch devices. This includes our PCMCIA Fax Modem
>product, which use to be our worse yeild and now is one of the best.
>
>Contact Steve Biegle with Alpha at (219) 922-7990. He has a lot of good
>data which you can review and use to set-up your own testing/evaluation
>process.
>
>If you have more specific questions regarding the testing I did you can
>contact me direct.
>
>Good Luck!!
>
>Kathy Palumbo
>Manufacturing Engineer
>Viking COmponents
>BUS.: (949) 643-7255
>
>----- Original Message -----
>From: CharlesC <[log in to unmask]>
>To: <[log in to unmask]>
>Sent: 07 June 1999 14:33
>Subject: [TN] Imersion Silver
>
>
>> Once again I need help.
>> I am looking for information on Alpha Metal's "AlphaLevel" Imersion
>silver
>> deposition. I have never built boards made with this process and would
>like to
>> know what experience anyone else may have had with this (good or bad ).
>The PWB
>> is mixed, some through hole mostly surface mount. I would especially like
>to
>> know about solderability and storage life.
>>
>> Thanks in advance.
>>
>> Charles Caswell
>> Process Lead,
>> Printed Circuit Board Dept.
>> Frontier Electronic Systems
>>
>
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