We started out not using paste, only applying flux during BGA rework.  After we got our x-ray system we found some of the connections were not wetting well and running out to the edges of the pads.  Now we use solder paste on all BGA’s, down to 0.8mm pitch.  We found it is best applied with a paste dispensing system rather than a stencil.

 

Jim Kittel

 

-----Original Message-----
From: bbarr [mailto:[log in to unmask]]
Sent: Thursday, October 26, 2000 5:57 AM
To: [log in to unmask]
Subject: Re: [TN] BGA REWORK

 

We do not use solder paste with eutectic balls. In the beginning we did use solder paste just for its flux content. Then we tried using just paste flux and results have been excellent. Our process is:

 

Remove BGA using hot gas rework station

Wick residual solder from lands

Clean

Apply thin layer of paste flux to lands

Attach new BGA with hot gas rework station

Clean

 

One thing to keep in mind is the nozzle design of the rework station. Some nozzles have a build in standoff to account for the thickness of the solder paste. If you are not using the paste it is possible for the BGA to be dropped onto the lands when the vacuum is turned off after alignment. That may result in misregistration. Do not over apply the flux because that may cause splattering and solder balls.

Bob


Robert Barr
Manufacturing Engineering
Formation, Inc.
Voice: 856-234-5020 x3035
Fax: 856-234-6679
email: [log in to unmask]

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Bogdan Gabi
Sent: Thursday, October 26, 2000 5:03 AM
To: [log in to unmask]
Subject: [TN] BGA REWORK

Dear Technetters

We are starting to rework BGA's.

A controversy arised about the necessity of solder paste for BGA's with eutectic solder balls.

Please send your opinion and your general procedure.

Thank you,

Gaby