TECHNET Archives

November 2006

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
Steve Gregory <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Steve Gregory <[log in to unmask]>
Date:
Thu, 16 Nov 2006 10:12:34 -0600
Content-Type:
text/plain
Parts/Attachments:
text/plain (98 lines)
It doesn't Victor. The situation probably is that he's building
assemblies that doesn't need to comply with RoHS, but the only BGA's
that are available have lead-free spheres...

-Steve- 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Victor G. Hernandez
Sent: Thursday, November 16, 2006 10:01 AM
To: [log in to unmask]
Subject: Re: [TN] Separation in BGA joints

Ioan,
   Early on the discussion you stated:   "Due to pressures from our
customers we run many lead-free BGAs on leaded paste at 220C. If this
forms joints, why LF on LF would not form joints at 246C, or let's say
230C if I am really off in my temp measurements? "

How does this comply with RoHS?

Victor,


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Tempea, Ioan
Sent: Thursday, November 16, 2006 8:12 AM
To: [log in to unmask]
Subject: [TN] Separation in BGA joints

Thanks to everybody who replied, including the non-metallurgists ;-} I
have certainly learned things!

I think the secret lies in that 270C melting point. I use a regular
SAC305 soldering recipe (right semantics, not profile; see, I got this
one Werner), hence the 240C target peak. Of course this will not move
the 1.75%Cu alloy.

One thing is that the component data sheet says the alloy is SAC305. But
it also recommends 260C for peak temperature. I find this very weird,
since somebody told me we need to solder at MP + 20C, so my 246C should
be more than OK. Not to mention that many ICs on the board are speced
per J-STD-020C for max peak of 250C.

Question 1: why this 260C recommendation, when 240C should be OK?

Then, I would like to know more about the case of high temp solder
balls. Why a joint will be formed around 210C between SnPb paste and
90/10 balls and the solder would not wet at 246C on a 270C solder ball?
The flux cushion is there in both cases. And why the SAC ball should
melt anyway, if solder wets on 90/10, why shouldn't it wet on other
higher temp balls? Is it because the Pb goes into solution with the Sn
whereas the high concentration Sn-Sn interfaces absolutely have to mix?

Thank you very much,

Ioan



---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e 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 1.8e 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 1.8e
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
-----------------------------------------------------

ATOM RSS1 RSS2