With regards to the sprays that can cool the circuit packs down for
troubleshooting, personally I would avoid the ones that are pure
perfluorinated hydrocarbons. Yes, they are non-flammable, non-toxic
(with normal use - however, anything can kill you if you work at it),
non-carcinogenic, non-mutagenic, non-teratogenic; BUT they are
incredible global warmers. I would say irrespective of which side of the
fence you are on with regards to man made global warming from carbon
dioxide emissions, we should seriously consider the possibility of
consequences of putting stuff into the atmosphere that has a lifetime of
thousands of years.
An alternative that we successfully used when I was at Nortel was CO2
from a compressed liquid tank applied using an attachment from a company
called Vatran.
http://www.vatran.com/parts.html
One word of caution though. Someone since then questioned me about ESD
safety of such a system and I do not have an answer for that. Seems to
me that would also apply to the cans of fluorocarbons as well.
Regards,
Bev
RIM
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dehoyos, Ramon
Sent: Thursday, April 26, 2007 10:55 AM
To: [log in to unmask]
Subject: Re: [TN] BGA Weights
Ron:
There are sprays that make a component very cold and a heat gun
will get them hot. These trouble shooting tools are used by test
technicians for instances like it is described.
If warpness of the board and the BGAs are the cause and weights
are used over the BGA it has to not soak up heat (cold solder joints )
and not too heavy to totally collapse the balls( cause shorts ). I would
say it is risky.
On the other hand if you need to try something, there are some bean
bags that I have seen being used in a previous life that were used on
PGAs and other big components over the solder wave to keep them from
floating up from the surface of the board. If you can not find bean
bags, try metal squares of different wights till you find what works.
Just remember that the reflow profile needs to be adjusted by using a
mole profiler. Desperate situations require desperate solutions.
Regards,
Ramon
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Thursday, April 26, 2007 10:28 AM
To: [log in to unmask]
Subject: Re: [TN] BGA Weights
I am not an expert in this. The protection circuitry is different for
various BGAs. I do know that the protection feature does not always work
properly, and can be triggered by 100F body heat. Information on thermal
protection was in the websites for Intel and STI and others.
I found this out the hard way, getting a complete lot of BGAs where the
sensor circuit was bad, but they did not test for that particular
function. After doing a lot of work to verify first that it was not the
solder process, and that it was not caused by timing issues on the
assembly, I finally had to set up a golden network card with a BGA
emulation socket, and began testing different lots of BGAs. Only the
units from the one lot failed, and heating them slightly with a hot air
gun caused them to start functioning. Or you could simply place your
finger on it for a second and it would start up.
-----Original Message-----
From: Ron Peeler [mailto:[log in to unmask]]
Sent: Thursday, April 26, 2007 7:27 AM
To: Stadem, Richard D.
Subject: RE: [TN] BGA Weights
Richard,
Could you explain more about the protective circuit in the BGA. I am
trying to understand how it can act like a trigger. Naturally a circuit
needs to stay cool so they don't overheat and short-circuit. I am
having trouble understanding how certain temperatures can cause them to
operate or shut down. Also I a having trouble understanding how placing
your finger on it is enough to trigger the BGA to work sometimes. I
have seen this issue before but usually reflowing them was the answer to
getting the board to work. I am now wondering if the cases were
reflowing the BGA didn't work wasn't just b/c we had a bad BGA, it may
have been something else.
Thanks
Ronald D. Peeler Jr., B.S. IE
Process Engineer
SWEMCO
Moorestown, NJ 08057
Tel: (856).222.9900 ext. 31
Cel: (484).948.0779
Fax: (856).222.0700
[log in to unmask]
-----Original Message-----
From: Stadem, Richard D. [mailto:[log in to unmask]]
Sent: Wednesday, April 25, 2007 4:38 PM
To: TechNet E-Mail Forum; Ron Peeler
Subject: RE: [TN] BGA Weights
Whoa, Ron.
On many BGAs there is a protective circuit inside that triggers it to
operate or shut down at certain temperatures. Placing your finger on it
is sometimes enough to trigger that. Don't always think that just
because you apply pressure with your finger and it either starts working
or stops working that therefore you have a bad solder joint. That is
quite often not the case. I have seen this phenomena more than once, and
it was proven not to have anything to do with the solder joints.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ron Peeler
Sent: Wednesday, April 25, 2007 3:23 PM
To: [log in to unmask]
Subject: [TN] BGA Weights
Hello TechNet
I was wondering is there anything in the industry that is used to weigh
BGA's down? We are having an issue @ our shop with BGA's not soldering
effectively to one of our boards. Currently we have a board that is
suppose to go through a boot process, however it has problems doing so.
The issue is resolved when you press down in the middle of the BGA and
fails again once the BGA is released. It doesn't help that our board
warps easily as well. Is there anything, small gram weights or so that
can weigh down a BGA without shorting it?
Thanks
Ronald D. Peeler Jr., B.S. IE
Process Engineer
SWEMCO
Moorestown, NJ 08057
Tel: (856).222.9900 ext. 31
Cel: (484).948.0779
Fax: (856).222.0700
[log in to unmask]
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