Hi, Genny,
I made a home run on board finish for BGA's - started off with NiAu, heard
all the nasty stories, got worried, investigated a lot of possible
alternatives and their processes and came right back to NiAu a lot wiser
than when I started. In terms of flatness of finish and good solderability,
it's very good, but if the board's not made well, it can be the worst
("black pad", etc). The secret is to choose a good fab house that changes
its plating baths regularly before the phosphor levels get too high and
knows the processes well. I can give you the fab notes I arrived at for
specifying this type of board off-line, if you're interested.
We have only assembled a few prototype boards with BGA's and this board
finish, but under close attention to the board fab and assembly stages, and
so far they're working well. Immersion tin is maybe a bit cheaper and has
its followers, but also has its detractors. If you're more comfortable with
that finish, it's OK.
Hope this helps to relieve some of the concerns.
Peter Duncan
ST Aerospace
Genny Gibbard
<Genny.Gibbard@W To: [log in to unmask]
AVECOM.CA> cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST
Sent by: TechNet Aero/ST Group)
<[log in to unmask] Subject: Re: [TN] BGA's in design
>
11/07/01 06:15
AM
Please respond
to "TechNet
E-Mail Forum."
Thanks to all suggestions. I found a good app note on the Xilinx site for
Board Routability Guidelines for Fine Pitch BGA Packages which is very
helpful.
As I expected, I got a few direct solicitations from board fab places,
mostly US, but no good testimonials of good experienced Canadian fab
houses.
I really do not want to go across the border at this time as we currently
do
not use any fab places outside the country, and it adds a whole other level
of complexity to shipping as well as possible delays especially with
heightened security these days.
Regards,
Genny.
To open another can of worms, most datasheets or app notes have said 'use
NiAu or OSP finishes'. We have 99.99% of the time so far used HASL (no
BGA's), have been made very wary of NiAu and have never tried OSP. We have
tentatively approved immersion Tin as an alternate finish in select cases
but have not used it, and I'm hearing a lot about immersion Ag these days.
Survey: What do you use for your BGA board finish?
---------------------------------------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
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 delivery of Technet send the following message: SET
Technet NOMAIL
Search previous postings at: www.ipc.org > On-Line Resources & Databases >
E-mail Archives
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for
additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700
ext.5315
---------------------------------------------------------------------------------
[This e-mail is confidential and may also be privileged. If you are not the
intended recipient, please delete it and notify us immediately; you should
not copy or use it for any purpose, nor disclose its contents to any other
person. Thank you.]
---------------------------------------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
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 delivery of Technet send the following message: SET Technet NOMAIL
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
---------------------------------------------------------------------------------
|
