Michael,
It depends (Dough Trade Mark) on what oxide thickness yoú have. Normal
oxide will be taken care of by the flux (RMA grade), thicker oxide by
stronger flux (RA grade), even thicker oxide by various halides and if the
later doesn't work , there is something very wrong with the DIPs.
5,000 pcs is pretty lots of packages, so if I were in your situation, I
would start with a crossection examination of the leads with a SEM or
a microprobe to see what hides below the surface. Sometimes, it's not an
oxidation problem, but a finish one. For instance, a bad nickel plate or no
finish at all.
It may be worth doing. It's an hour or two job, depending on what resources
you have and also how experienced the analyst is.
Inge
On 14 October 2011 14:58, Forrester, Michael (H USA) <
[log in to unmask]> wrote:
> We have about 5000 lead -free surface mount 8 pin Dip/so ICs with
> oxidation on the leads. The will be used on a tin/lead assembly. The
> plan it send the parts out to have them pre-tinned.
> We have the option of pre-tinning with lead-free or tin/lead solder.
> The lead-free tinning is about $1.20/part and the leaded is about $0.70.
> My thinking is that since we are
> going to use tin/lead to attach it to the PCB why spend the extra $2500
> to get lead free. The vendor is pushing that since the parts where
> originally lead free we should pre-tin them lead free.
> What I'm not sure is, is ther a real reason to pre-tin the parts using
> lead free solder or is the vendor just trying to make more money? I
> then started to think, is this the best method to get
> oxidized parts soldererable? Is there a better way (ultasonic cleaning,
> etc.)? THank you in advance.
>
> Best Regards,
>
> Michael Forrester
> Sr. Product Engineer
>
> Siemens Healthcare Diagnostics
> 101 Silvermine Rd.
> Brookfield, CT 06804
> PH: (203) 740-6452
>
>
>
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