Hi Rex!

Yeah I was wondering what kind of email I was getting there. Outlook tells
you in a little pop-up window that it's downloading a message, but doesn't
you who it's from. You have to look in your inbox when it's done to see
that. I saw that it was taking a long time and thought it might be one of
the huge gerber files that we get from our design center. We've gotten some
that have to be sent in 3 or 4 emails (30mb+) because they're so big!

Anyways, I have your pictures posted now after I shrunk them down some
myself. They're here:

http://stevezeva.homestead.com/BGA_P1.JPG

http://stevezeva.homestead.com/BGA_P1_Oblique.JPG

http://stevezeva.homestead.com/PCB_P1.JPG

http://stevezeva.homestead.com/PCB_P1_Oblique.JPG

Steve

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Rex Waygood
Sent: Wednesday, November 04, 2009 11:36 AM
To: [log in to unmask]
Subject: [TN] BGA Balls

We have built a batch of pcbs for a customer who supplied the pcbs. They
are 2mm thick 6 layer with 0.2mm vias and ENIG finish. None work fully,
they work intermittently at best. 

The customer was suspicious that we had not reflowed the BGAs correctly.

Our under BGA temp on a similar pcb is 245C (We now have some samples to
profile correctly)

The customer is suspicious due to the comment on page 753
http://www.atmel.com/dyn/resources/prod_documents/doc6221.pdf
<http://www.atmel.com/dyn/resources/prod_documents/doc6221.pdf>  where
it states a min of 250C

Close x-ray evaluation of the BGAs showed tear dropping along tracks,
uniform balls, everything looked tickety boo.

We offered to remove a BGA to see what was happening underneath.

2 corners showed a similar issue with the ball where it separated from
the BGA rather than the pcb.

The removal technique was to use a PDR IR rework station, under board
heating to bring topside pcb temp to 170C and then a lead free reflow
profile to bring the device up to reflow, manual removal.

I didn't have dye for dye and pry so thought this might show if there
was an ENIG problem.

I was surprised by the almost complete removal of ball at the device and
lack of evidence of solder.

Was this just caused by my investigation processes?

Was the ball device interface broken which prevented it from melting the
ball?

Any other clues?

Thanks

Rex

 

Hopefully Steve has received the images (sorry about the size!)

 
Rex Waygood
Technical Manager

Hansatech EMS provides value manufacturing through engineering and
quality

________________________________


Hansatech EMS Limited
Benson Road
Nuffield Industrial Estate
Poole
Dorset BH17 0RY
United Kingdom


Tel:
Fax:
DDI: 	+44 (0)1202 338200
+44 (0)1202 338202
+44 (0)1202 338222 	
[log in to unmask]
www.HansatechEMS.com <http://www.hansatechems.com/>  
 

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