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

From: [log in to unmask]>[log in to unmask]

To: [log in to unmask]>[log in to unmask]

Sent: Tuesday, November 20, 2001 1:47 AM

Subject: RE: Re: [TN] BGA voids

I have gone  to your website today and downloaded some data what I need. What I still want to know is,
1, how to do outgassing oil test
2,  it is plated in via, so what is the rootcause of void? Do you agree it cause by the solder paste flux during the reflow process

Thanks
tony

-----Original Message-----
From:   Bob Willis [SMTP:[log in to unmask]]
Sent:   Monday, November 19, 2001 12:17 PM
To:     Tony Zhang-0343CE
Subject:        Re: Re: [TN] BGA voids

I may be able to send you information but you need to tell me what you want or wait till your server is working.
 
Bob Willis
Electronic Presentation Services
2 Fourth Ave, Chelmsford, Essex, CM1 4HA England
 
See us at APEX 2002  www.bobwillis.co.uk/workshops/apex/apex.htm <http://www.bobwillis.co.uk/workshops/apex/apex.htm>
 
www.bobwillis.co.uk <http://www.bobwillis.co.uk>
Tel: (44) 01245 351502 Fax: (44) 01245 496123
 
Single solution to your seminar, conference or roadshow www.seminar-registrations.com <http://www.seminar-registrations.com>

----- Original Message -----
From: [log in to unmask] <mailto:[log in to unmask]>
To: [log in to unmask] <mailto:[log in to unmask]>
Sent: Monday, November 19, 2001 2:48 AM
Subject: RE: Re: [TN] BGA voids




Willis,
     Our sever downed for daoys, so I can not go to your website to see the detail information, Could you pls send the information to me?

Thanks
Tony Zhang
Process Engineer
Hangzhou Motorola






        -----Original Message-----
From:   Bob Willis [SMTP:[log in to unmask] <[log in to unmask]">mailto:SMTP:[log in to unmask]>]
Sent:   Friday, November 16, 2001 5:59 PM
To:     [log in to unmask]
Subject:             Re: [TN] BGA voids

        We have experienced voiding with via in pad, I know it ws stated that the pads don't have vias in them but if they did they can somtimes gass through the plating, its not the air traped by the paste. I have investigated this with my old outgassing oil test which showes up the problem and will contribute to voiding.

         
Bob Willis
 
See us at APEX 2002  www.bobwillis.co.uk/workshops/apex/apex.htm <<http://www.bobwillis.co.uk/workshops/apex/apex.htm>>
 
www.bobwillis.co.uk <<http://www.bobwillis.co.uk>>
Tel: (44) 01245 351502 Fax: (44) 01245 496123
 
Single solution to your seminar, conference or roadshow www.seminar-registrations.com <<http://www.seminar-registrations.com>>

        ----- Original Message -----
From: Peter George [log in to unmask] <<mailto:Peter> George [log in to unmask]>
To: [log in to unmask] <<mailto:[log in to unmask]>>
Sent: Friday, November 16, 2001 8:52 AM
Subject: Re: [TN] BGA voids

        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] <<mailto:[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






















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