Bing
Keep the paste but change your component supplier!
Brian
Milanie Racuya wrote:
> Hi guys,
> Regarding this process of getting rid of oxides on IC leads with the
> help of ultra-high activated flux on the solder paste-is this an
> effective move? We are experiencing unsoldered joint on our IC leads. We
> have adjusted a lot on our reflow profile, within specs solder paste
> height and good solder printing but still we experience unsoldered
> joints. We are suspecting it on the solder plating of the IC's but we
> don't have the means of testing the degree of solder plating.
> Should you advice me to change paste? I have tried same paste but with a
> higher flux activation level but still unsoldered joint occurs. Even
> tried another type and so far, initial results are better. Does this
> mean that the paste is not compatible with our existing process??? or
> materials???
> I need helllppp!!!
>
> Thanks,
> Bing
>
> Brunker Ed wrote:
>
> > No it's no coincidence.
> > Soldering is a nasty process. High flux activity means low soldering
> > defects. The flux is doing a job, breaking up barriers which would
> > prevent
> > wetting. The more aggressive tyhe flux the better it will break up the
> >
> > oxides on the surfaces. The issue is what are the implications for the
> > long
> > term life of the assembly. Many assembly locations don't even consider
> > this,
> > the DPMO is the bottom line. (Probably aren't monitoring that anyway).
> >
> > Anyway, life is a balance. These figures fall nicely in the range
> > where you
> > will have good soldering but still be reasonable for long term
> > reliability.
> > Who is your customer, what is the application? Do we really need
> > XE+10?
> > Regards
> > Ed Brunker
> > Principal Process Engineer
> > Sendo
> >
> > -----Original Message-----
> > From: Amanda.Mountain [mailto:[log in to unmask]]
> > Sent: Thursday, August 24, 2000 2:41 PM
> > To: [log in to unmask]
> > Subject: [TN] SIR Interpretation
> >
> > Hi all. I'm hoping to pull on the experience on this list...
> >
> > Performing a flux evaluation, we performed SIR tests with 8 different
> > conditions (4 fluxes, 2 temperatures). The IPC coupons were processed
> >
> > through our wave soldering/spray fluxing process, doing our best to
> > simulate
> > regular production. The fluxes we are evaluating are all VOC free/no
> > clean/water soluble/low solids/low residue fluxes.
> >
> > The test was performed to Bellcore standards.
> >
> > The SIR results we received were lower than expected - ranging from
> > 2.74E+9
> > to 4.27E+10. The pass value assigned by the laboratory is 3.2E+10.
> > Only 3
> > of 32 samples actually passed this standard. 6 of the 32 samples
> > passed the
> > Bellcore minimum value (2.0E+10). What sort of implications can we
> > expect
> > with selecting a flux with slightly lower SIR results than the minimum
> >
> > value? Each of the flux vendors provided their own passing SIR test
> > results.
> >
> > One other thing that was noted was that the boards with the fewest
> > defects
> > came back with the poorest SIR results, and vice versa. Is this just
> > a
> > coincidence, or is there a solid explanation for this?
> >
> > Thanks in advance,
> >
> > Amanda Mountain
> >
> > Amanda Mountain
> > Process Engineering
> > Leitch Technology International Inc.
> > Phone: (416) 445-9640 ext. 3852
> > Fax: (416) 445-7927
> > http://www.leitch.com/
> >
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