Hi Rex,



Can you X-section one of the BGAs? It would be a good start and tell a lot. If you don't have the capabilities, I can help you.



Regards,



Vladimir

SENTEC

SENTEC

11 Canadian Road, Unit 7.

Scarborough, ON M1R 5G1

Tel: (416) 899-1882

Fax: (905) 882-8812

www.sentec.ca





-----Original Message-----

From: Rex Waygood <[log in to unmask]>

Date:         Wed, 4 Nov 2009 16:35:52 

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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