Hi Tetsuro,
so the pad design will have to change, but how? Could you suggest any
guidelines, like apply this coefficient, or change from rectangular to oval,
etc.?
Thanks,
Ioan
> -----Original Message-----
> From: Tetsuro Nishimura [SMTP:[log in to unmask]]
> Sent: Friday, July 23, 2004 2:35 AM
> To: [log in to unmask]
> Subject: Re: [LF] LeadFree and Land Patterns (Wave solder)
>
> 1, In general, LF solder has a greater surface tension and a inferior
> wetting than those of Sn/37Pb. Therefore, according to our experience, the
> incidence of shorts and/or nonwetting increase by converting LF solder. To
> cope with that, pad pattern should be optimized by changing for LF solder.
> Taking a consideration for that is recommended.
>
> 2, In case of a XPC laminate, a C-cut pad will be effective. Nevertheless,
> the other kinds of board does not need a C-cut pad. Any how, a larger
> fillet
> provides greater strength, so larger fillet is desirable.
>
> 3, Since melting point of LF solder is higher than that of Sn/37Pb, LF
> solder becomes solid very quickly when heat input stops. So the risk of
> short incidence increases in case of LF solder. Therefore, the shape of
> and/or pitch of termination should be optimized to minimize such
> incidence.
>
> Tetsuro Nishimura
> Nihon Superior Co.,Ltd.
> [log in to unmask]
> www.nihonsuperior.co.jp
>
> ----- Original Message -----
> From: "William E. Hunt" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Thursday, July 22, 2004 5:21 AM
> Subject: Re: [LF] LeadFree and Land Patterns (Wave solder)
>
>
> > Has anyone seen changes for LF wave solder pad geometries? Our contract
> > mfg has requested pad changes for a component that is hand soldered
> after
> > the board passes through wave solder. The pad was collecting too much
> > solder and filling the hole. Then the hole would need to be cleaned out
> > and the part hand soldered to the board. The change was to a C-cut pad.
> > The idea of a C-cut pad is to prevent solder from filling the hole
> during
> > wave soldering so the component can be easily inserted and hand soldered
> > post wave. Instead of having just one opening in the pad the CM proposed
> > openings on both sides (leading and trailing edges) of the pad. This is
> a
> > high volume, simple type III assembly using a XPC laminate. We are
> still
> > investigating the need for this change and continue to test but I'm
> > interested in other experiences with LF wave soldering.
> >
> > What are your experiences with LF wave solder?
> >
> >
> >
> > Bill Hunt
> > Eastman Kodak
> > Office: 585-726-4892
> > Fax: 585-726-3278
> >
> >
> >
> >
> > Pratap Singh <[log in to unmask]>
> > Sent by: Leadfree <[log in to unmask]>
> > 07/21/2004 03:13 PM
> > Please respond to "(Leadfree Electronics Assembly Forum)"; Please
> respond
> > to Pratap Singh
> >
> >
> > To: [log in to unmask]
> > cc:
> > Subject: Re: [LF] LeadFree and Land Patterns
> >
> >
> > Roger,
> > No need to fret. Land pattern should not be affected by converting to LF
> > solder. Depending upon the solder used, reflow profile settings will
> > change since LF solders flow at higher temperature.. Visual inspection
> > and void inspection should also remain same.
> >
> > _____________________
> > pratap singh
> > Tel./Fax: (512) 255-6820
> > email: [log in to unmask]
> > www.rampinc.com
> >
> >
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