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January 2009

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Subject:
From:
Tan Geok Ang <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Tan Geok Ang <[log in to unmask]>
Date:
Thu, 15 Jan 2009 17:26:51 +0800
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text/plain (239 lines)
Hi Paul,

      Please refer to below:

 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Paul Edwards
Sent: Thursday, 15 January 2009 11:52 AM
To: [log in to unmask]
Subject: Re: [TN] Possible cause on open

 

GA Tan...

 

A couple of questions....

Pitch and ball size of BGA --> 40mils, 19mils

PCB pad size -->16mils

PCB material and thickness --> FR4, 1.6mm

Underfill material - SunStar 991

What solder and ball metalllury --> SAC 

Top and bottom heater temps 

Time above 230C --> about 45sec

Cooldown ramp rate--> 2.8 sec

How was 16G force generated and how was the coupon mounted to the
generator --> fixture

 

 

 

 

Paul

 

Paul Edwards

Surface Art Engineering

 

 

 

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

From: TechNet [mailto:[log in to unmask]] On Behalf Of Tan Geok Ang

Sent: Wednesday, January 14, 2009 5:27 PM

To: [log in to unmask]

Subject: [TN] Possible cause on open

 

Hi Steve,

 

            Please help to download these pictures TechNet, thanks.

 

 

 

 

 

 

 

Hi All experts,

 

            Testing (combine test of 16G at 85 oC) was performed on

evaluation boards with under-filled BGAs. Open issue (cracks) was

detected only at some corners of the BGA (35x35mm with 1156 balls) after

the test. Lead-free process and PCB with ENIG surface finish. Peak

temperature is 248 oC with a 65 sec above 217 oC.

 

FYI, the service lab has not come out a report.

 

            What are the possible causes? (CET mismatches, Lead-free

alloy related, material, processes)

 

 

 

            Thank you in advance.

 

 

 

Regards

 

GA Tan

 

 

 

 

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