[Coco] assembly questions?

[jdaggett at gate.net]

Mark

The biggest problem with BGA is when the BGA pads on the PCB 
themselves. I have sliced and dice enough PCBs with BGA joint 
and looked at joints under a scanning electron microscope to know 
about how any BGA joint can fracture. 

The BGA pads need to be protected at all stages after initial etch. In 
the line of work that I used to do, 90% of the failures were at the 
PCB/Ball joint. Often due contaminations from the PCB processing 
that even presolder cleaning will not correct. Often what happens is 
when a weakened joint is exposed to high stress and board flexure, 
there is an icreased risk of failure. 

Simply this, if you solder to copper chloride the joint is going to fail. 
Almost invariably the contaminat is chlorine. 

james


james
On 26 Jul 2004 at 15:57, mmarlett at isd.net wrote:

From:           	mmarlett at isd.net
To:             	coco at maltedmedia.com
Date sent:      	Mon, 26 Jul 2004 15:57:08 -0500
Subject:        	RE: [Coco] assembly questions?
Send reply to:  	mmarlett at isd.net,
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> David,
> 
> We have no internal Xray, all done at the vendor. The thing you have
> to watch out for is that when the boards are assembled they are clean,
> parts are clean. Thus you have contact, poor, but contact. So you
> functionally test and the board passes. As oxidation occurs you now
> start to have problems in the field, the worst kind to have, $$$$$$. 
> 
> We are all new to this and haven't had alot of rework on the BGA side.
> Our rework station will do just about anything. Get the correct nozzle
> and you are set.
> 
> Mark
> Cloud-9
> 
> >Ya, we've been looking at getting it for my work to repair our new
> >boards which would be BGA.
> >
> >The actual board stuffing takes place at our board house vendor.  As
> >far as X-Ray analysis, we're just planning on doing a functional
> >burn-in test to make sure they work instead.
> >
> >You probably have to go thru all that for mil-spec stuff which can
> >add greatly to the cost of the board over just getting the board
> >stuffed.
> >
> >
> >Dave
> >
> >-----Original Message-----
> >From: coco-bounces at maltedmedia.com
> >[mailto:coco-bounces at maltedmedia.com] On Behalf Of mmarlett at isd.net
> >Sent: Monday, July 26, 2004 3:16 PM To: coco at maltedmedia.com Subject:
> >RE: [Coco] assembly questions?
> >
> >Dave,
> >
> >$12k, that is a bargin. Ours is $85K. Not Cloud-9's either, this is a
> >hobby for me. That would be my REAL job's machine.
> >
> >Regards,
> >
> >Mark
> >Cloud-9
> >
> >>BGAs really need to be set on a board by machine.
> >>
> >>Normally both sides of the board are heated for a predetermined time
> >>and/or temperature when the chip is set.
> >>
> >>You can see what a small BGA rework station looks like at
> >>coopertools.com
> >>
> >>The Weller one is real nice for small scale stuff, and it's a
> >>bargain
> >at
> >>12 grand!  ;)
> >>
> >>
> >>Dave
> >>
> >>-----Original Message-----
> >>From: coco-bounces at maltedmedia.com
> >[mailto:coco-bounces at maltedmedia.com]
> >>On Behalf Of Kevin Diggs
> >>Sent: Monday, July 26, 2004 2:28 PM
> >>To: CoCoList for Color Computer Enthusiasts
> >>Subject: Re: [Coco] assembly questions?
> >>
> >>Hi,
> >>
> >>	Regarding previous discussions on this thread, Is there
> >>no way to use these new packages (BGA) with some kind of
> >>adapter on older circuit boards that hobbyists can make?
> >>
> >>					kevin
> >>
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> >>
> >>
> >>
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> >>
> >
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> >
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