Steve,

Sounds like a relatively straightforward variant of thermocompression
beam-lead bonding.

Vlad is correct in asking for the evidence left on the flying lead.  That is
where you need to go next.

You can also get a good deal of hydrogen embrittlement of the copper from
the plating operations, but would tend to believe this would balance out
between them.

Might the difference in apparent pull strength be a result of a difference
in strength/rigidity of the leads, resulting in differing force vectors on
the bond?

Steve C

-----Original Message-----
From: Steve Kelly [mailto:[log in to unmask]] 
Sent: Wednesday, January 06, 2010 8:51 AM
To: 'TechNet E-Mail Forum'; 'Steven Creswick'
Subject: RE: [TN] Pull strength of thermosonic wire bondable gold

Hi Steve et al,
Unfortunately this is not as easy as it sounds. First the lower pull
strengths are not necessarily a failure- they are just not as good. This was
an experiment designed between ourselves and our customer. The initial
problem is we have a .0032 wide flying lead ( about 150 of them) with no
kapton support. A chip/die is "compression bonded" onto the lead - from what
I can gather it is a combination of heat/pressure/ultrasonic and some kind
of proprietary magic. The reason we went to the lower nickel is because the
leads being so fragile they often crack during the process so we tried the
lower nickel to alleviate this issue. With the lower nickel pull is approx.
5-7 grams. With the higher nickel 9-11 grams. There is a gold bump on the
die and when the failure happens the gold bump separates from the lead with
no damage to the gold bump. At present this is as much as I know. Thanks for
the input so far. Steve Kelly

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steven Creswick
Sent: January-05-10 6:14 PM
To: [log in to unmask]
Subject: Re: [TN] Pull strength of thermosonic wire bondable gold

Steve,

If you can send me the data sets in an Excel format, I can provide you with
some insight based on magnitude and grouping by Weibull plot.  

If there is a big mix of failure modes, this interpretation will be pretty
generic.  

Its free input, however   :-)

Just send it direct.

Steve C

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Kelly
Sent: Tuesday, January 05, 2010 4:17 PM
To: [log in to unmask]
Subject: [TN] Pull strength of thermosonic wire bondable gold

Hi All,

I have a wire bond question to the wire bond gurus who have helped me out a
lot in the past. Made 2 versions of a flex circuit - only varied the nickel
thickness. Application is thermosonic gold wire bonding.

Flex circuit lead is .0032 wide - version 1 - nickel is 150 microinches -
soft gold is 50 microinches- pull strength is X

                                                        Version 2 - nickel
is 40 microinches - soft gold is 50 microinches - pull strength is approx.
½X  of version 1-

Is this what I should expect?



Regards Steve Kelly



Steve Kelly (PLEASE NOTE NEW E-MAIL ADDRESS)

(416) 750-8433 (work)

(416) 750-0016 (fax)

(416) 577-8433 (cell)




---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16
for additional information, or contact Keach Sasamori at [log in to unmask] or
847-615-7100 ext.2815
-----------------------------------------------------

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16
for additional information, or contact Keach Sasamori at [log in to unmask] or
847-615-7100 ext.2815
-----------------------------------------------------

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------