Vinit Verma wrote:
>
> I have recently been facing a problem after reflow soldering. Almost every
> chip component (approx. 60-70%) has a solder ball attached to the component
> on one side between the solder joints. This ball detatches if moved with a
> tweezer or something sharp.
>
> The paste quality has been checked, reflow profile has been fine tuned and
> checked, PCB has been baked to take care of any moisture entrapped. But the
> problem still remains. However, after baking of the PCB the occurence of the
> problem has reduced (to approx. 20-30% of chip components)
>
> If anyone of you has ever encountered this problem and knows of a possible
> cause and the solution to the same, please forward it to me.
>
> Regards
> Vinit Verma
> Bharti Telecom Ltd., Gurgaon, India
> Tel: +91-124-372721,22,23 (O)
>         +91-11-7871747 (R)
> Fax: +91-124-372724 (O)
>         +91-11-5783571 (R)
>
> --------------------------------------------------------------
> Bharti Telecom Limited, Gurgaon, India
>
> ################################################################
> TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
> ################################################################
> To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
> To subscribe:   SUBSCRIBE TechNet <your full name>
> To unsubscribe:   SIGNOFF TechNet
> ################################################################
> Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information.
> For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
> ################################################################

Vinit:

There are many factors that affect solder ball formation- solder paste
composition, solderability of pad and component leads, reflow
environment i.e. air or nitrogen, soldermask surface size of particles
in solder paste, excessive paste volume and moisture in the
flux/paste[1].

Drying process is critical to solder ball formation. Try higher metal
content solder paste and or slightly larger particle size in the
paste[1].

By the way, I am from Gurgaon also. What does Bharti Telecom build and
where it is located? When I visit Gurgaon in 1999, will it be possible
to tour Bharti Telecom?

[1] Failure modes and Mechanisms in Electronic Packages- P. Viswanadham
and Pratap Singh Chapman & Hall 1998.

################################################################
TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE TechNet <your full name>
To unsubscribe:   SIGNOFF TechNet 
################################################################
Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################