Peter,
Bill is right about the need to avoid trimming leads after solderwave. The
thicker the lead and/or cheaper the cutter the more likely there will be a
cracked solder joint. IPC class-2 says that this cracked solder joint does
not need to be remelted and class-3 says it does. Class-2 recommends 60-100
mils lead length unless otherwise specified by the customer. If you are
building to Class-2 and you don't want a possible lab or field failure
because of a cracked solder joint then think and plan ahead to avoid having
to trim. The thinking and planning includes the final assembly the PCA will
be in. For instance, clearance for slot cards to slid in and out. Connector
leads under a front panel even with an insulation strip can cut through the
insulation eventually fail. I had a customer who wanted me to trim 70 mil
plus diameter pins to 30 mils on the off the shelf power supply instead of
ordering the right length leads. They would have to be machined to do that
which can lead to other defects.
Dorothy Lush
> ----------
> From: Kasprzak, Bill (sys) USX[SMTP:[log in to unmask]]
> Reply To: TechNet E-Mail Forum.;Kasprzak, Bill (sys) USX
> Sent: Thursday, July 12, 2001 12:58 PM
> To: [log in to unmask]
> Subject: Re: Lead protrusion
>
> Peter:
>
> Personally, I like .090", but typically I have to hold between .040 and
> .060. In my mind, I think you would like to install parts with the correct
> lead length prior to wavesoldering. Avoid having to trim after soldering
> is
> always a good idea.
>
> Bill Kasprzak
> Moog Inc., Electronic Assembly Engineering
>
>
> > -----Original Message-----
> > From: PL [SMTP:[log in to unmask]]
> > Sent: Thursday, July 12, 2001 2:26 AM
> > To: [log in to unmask]
> > Subject: [TN] Lead protrusion
> >
> > Hello,
> >
> > Does anyone know what is the standard used for prepping
> > the leads for through-hole boards?
> >
> > What are the critical parameters one should consider
> > when determining the amount of trimming on the leads?
> >
> > Rgds,
> > Peter
> >
> >
> > _________________________________________________________
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> >
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