I don't think it's only Texas Instruments that makes such heavy BGA's. I'm having bridging underneath some Altera BGA652's (EP20K400) that have a heavy metal coolingplate. According to Altera the part has no history of bridging problems, so (until the present discussion) I thought I was all alone with this nasty phenomenon of balls collapsing more than usual.
I think the explanation for the fact that some assemblers have a problem with these heavy BGA's and others don't, is strongly related to the footprint-design (given the fact that these BGA's are more critical than the normal PBGA's).
If - as a subcontractor - you have to assemble designs with a footprint that "just happened to be in the footprint-library", it's all to easy to end up with defective boards. By the time you realize that you should have used "shims", you'll probably already have an unsatisfied customer.
To my opinion the real challenge is to have your customers make their BGA-designs more robust, so that these heavy BGA's result in defect levels comparable to normal PBGA's.
Daan Terstegge
Unclassified mail
Personal website: http://surf.to/smtinfo
>>> Rick Thompson <[log in to unmask]> 05/05 8:44 pm >>>
Bob,
Are we talking about the same parts? The earlier 'C6201 parts weren't a
problem. To my knowledge, the current heavier heat slug package was only
introduced on the 'C6201 parts with a recent die rev change.
Rick Thompson
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Bob Perkins
Sent: Friday, May 05, 2000 10:37 AM
To: [log in to unmask]
Subject: Re: [TN] Texas Instrument BGA's...
I have sure heard a lot of concern regarding this part, however we have
placed thousands of these BGA's and have only seen a few that have
collapsed. It was my feeling that the reason it collapsed was do to a chain
reaction of shorts, from either a bad print or smudged paste after bumping
the part while still wet. Yes this BGA is a challenging to look at under
x-ray (we have had to purchase a CR Tech) and reflow, but realistically we
have had no problem with this part and "no shims". We have a product that
has four side by side, profiling was the biggest issue to get these to
reflow without damaging the rest of the board, go slow (6)min and reflow
over two zones with lower temperature seems to work.
Bob Perkins
Automation Technician/
Manufacturing Engineer
Aimtronics
-----Original Message-----
From: Stephen R. Gregory [mailto:[log in to unmask]]
Sent: May 4, 2000 6:44 PM
To: [log in to unmask]
Subject: [TN] Texas Instrument BGA's...
Hey ya'll,
I finally talked to an engineer from Texas Instruments about the problems
with their BGA's (PN# TMS320C6201GJC200), and expected the "song and dance"
that I got.
The person that I spoke with first stated that from their tests there
weren't
any manufacturability issues with the part, but when I spoke about hearing
first hand that there have been shorting problems unless the part was
"shimed", the person I was speaking with said that there has been some
problems reported from users to that effect (he first denied any such
problems), but he told me that the problems that he knew of, was because the
BGA location was in the center of the board, and was susceptable to the
bridging problem because of the fab warping during reflow...I don't buy
that.
I asked if Texas Instruments was doing anything to address the issue, such
as
high temp balls, and he said no...because there isn't a problem with the
part. He also stated that there isn't a need for x-ray with this part;
"because of the self-centering" characteristics that the part has. He also
stated that the balls will be collapsed more because of the added weight of
the heat sink...sheesh! Tell me something I don't know!
I wanted to know what I could do to prevent from having to rework this BGA
due to bridging, and what, if anything, Texas Instruments was doing to
address the issue.
I might as well have been talking to a wall...
-Steve Gregory-
##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following
text in
the body:
To subscribe: SUBSCRIBE TECHNET <your full name>
To unsubscribe: SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information.
If you need assistance - contact Keach Sasamori at [log in to unmask] or
847-509-9700 ext.5315
##############################################################
##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following
text in
the body:
To subscribe: SUBSCRIBE TECHNET <your full name>
To unsubscribe: SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information.
If you need assistance - contact Keach Sasamori at [log in to unmask] or
847-509-9700 ext.5315
##############################################################
##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in
the body:
To subscribe: SUBSCRIBE TECHNET <your full name>
To unsubscribe: SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information.
If you need assistance - contact Keach Sasamori at [log in to unmask] or
847-509-9700 ext.5315
##############################################################
##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in
the body:
To subscribe: SUBSCRIBE TECHNET <your full name>
To unsubscribe: SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information.
If you need assistance - contact Keach Sasamori at [log in to unmask] or
847-509-9700 ext.5315
##############################################################
|
