TECHNET Archives

November 2001

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
"<Peter George Duncan>" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 16 Nov 2001 16:52:53 +0800
Content-Type:
text/plain
Parts/Attachments:
text/plain (113 lines)
Hi, Peter,

I was at a seminar earlier this year where BGA's and their solder joints
were discussed at some length. The received wisdom is that voids in solder
joints are not of themselves a 'defect' unless they break out through the
side of the ball. In fact, they make the joint more "flexible" - better
able to withstand creep fatigue - so are beneficial, up to a point.

What causes them is often outgassing of volatiles in the solder paste flux
during the reflow process, though the size and shape of voids increases and
changes when there are via-in-pad features as well. About the only way to
detect them is by X-ray, and to judge from previous TechNet postings, there
are some pretty fancy machines around now that can give you a very much
clearer view of the balls than is normally the case ... if you have cash to
splash!

Peter Duncan




                    Peter Lee
                    <ppwlee@YAHOO        To:     [log in to unmask]
                    .COM>                cc:     (bcc: DUNCAN Peter/Asst Prin Engr/ST
                    Sent by:             Aero/ST Group)
                    TechNet              Subject:     [TN] BGA voids
                    <[log in to unmask]
                    ORG>


                    11/16/01
                    04:25 PM
                    Please
                    respond to
                    "TechNet
                    E-Mail
                    Forum."






Hello,





I am encountering voids after reflow on several micro BGAs on one PCA
product. The voids that I $B!G (Bve observed (with Xray) contribute to as high as
60-70% of the joint area. My reflow profile was designed by running a
sample board with dummy components and thermalcouples attached right at the
joint. I also inspected the PCB lands and didn $B!G (Bt see any via on pad.





Does anyone know the possible reasons for voids formation in BGA (micro)
reflow?





In general, in step by step how would one trouble shoot such a defect?





Rgds,


Peter






















[This e-mail is confidential and may also be privileged. If you are not the
intended recipient, please delete it and notify us immediately; you should
not copy or use it for any purpose, nor disclose its contents to any other
person. Thank you.]

---------------------------------------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
---------------------------------------------------------------------------------

ATOM RSS1 RSS2