Inge,
Good ideas. I have tried a plumbing type dye and height guages with a flat plate before but that was unsuccessful. I will try that if given the opportunity.
Kat
Sent via BlackBerry from Cingular Wireless
-----Original Message-----
From: Hfjord <[log in to unmask]>
Date: Thu, 26 Apr 2007 23:15:48
To:[log in to unmask]
Subject: [TN] SV: [TN] BGA Weights
Kathy,
I've some small tests, that I use when the measuring machine is not
available.
Do you have a piece of white ceramic like Al2O3, LTCC or AlN? Polished
aluminum oxide is best. Do you have an old fashioned stamp pad, still
with that typical blue or red ink. Good. Take the BGA and put it with a
light hand on the stamp pad, then immediately place it on the white
ceramic. Press a little with your finger with the 2 carat diamond ring
on. You will get a picture of the coplanarity when you lift up the BGA.
If the BGA is very warped, you will get no marks on several sites.
Then, take the board immediately after solder paste printing and let the
board pass your soldering oven without components on. Study the wetted
BGA pads. Did you get good wetting on all the pads? If there is a
wetting problem, you'll see that clearly. If you use a good flux, you
should see a line of flux residues around the molten solder as well.
Another shortcut is to use a thin preparation glas plate. Wet the stamp
pad with dye penetrant ink. Same procedure as before, place the BGA on
the stamp pad, then place the BGA with the balls up on your stereo
microscop board. Place the glass plate vertically and cautiously on the
balls and have a look in the microscope. If the BGA is very warped,
you'll see that clearly.
And this one, if you have UV microscope. Place the BGA from above on
the glass plate and remove the BGA, then immediately place the glass
plate under the UV microscope. It takes you just two seconds to see if
all sites shines blue.
Not very scientific a method, but better than kicking the whole box of
BGAs out through the window. In all cases, you must not wet the balls
too much, because then it won't work.
I have used these little methods on superBGAs with up to 2,500 balls,
don't know if it works with small ones.
My two milligrams
Inge
-----Ursprungligt meddelande-----
Från: TechNet [mailto:[log in to unmask]] För Kathy Kuhlow
Skickat: den 25 april 2007 22:33
Till: [log in to unmask]
Ämne: Re: [TN] BGA Weights
Weighting it down is only a band aid fix, maybe duct tape would help. Is
it
possible to support the PCB and reflow/replace the BGA's?
Is there a thermal issue that caused the bga's to be open or do you
think
the flexing has created opens?
Kat
-----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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