I'm guessing VOC free and foam fluxer. An alcohol based flux should not be
doing this to you.

Does your machine have and air knife? Try changing the angle of the knife,
pressure and/or volume of air.

What kind of preheater? IR?

You might consider the aggressive approach of adding a home-made manifold in
the preheat zones to stir the air. Copper pipe, drill some small holes in
the pipe add an air flow regulator and you can augment the preheat action
with a little convection.




> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of Jorge Rodriguez
> Sent: Friday, January 11, 2002 2:10 PM
> To: [log in to unmask]
> Subject: [TN] Solder Balls on Wave Solder
>
>
> Technetters,
>
>         My company is having a solder ball problem on the wave solder. The
> issue is primarily caused by overly large un-masked  vias on both
> sides. The
> via diameter is 25 mils with an annular ring of 25 mils on a .062"  board.
> On the wave solder process, the flux gets entrapped inside the vias and no
> matter what we do on the pre-heating section there still flux remaining
> inside that causes the solder to explode into tiny solder balls
> when it gets
> to the laminar section of the wave, like a volcano effect on the component
> side. These boards have also a good amount of the same vias under
> fine pitch
> QFP devices , this narrows our process window  if we want to heat
> the board
> even more. Heating the board more on the preheaters to resolve the solder
> ball problem leads on re-reflowing of the leads of those devices
> and quality
> problems as a result of that, the QFP pins pop up and become un-soldered.
> The customer does not want to use smaller vias or get them masked
> off since
> vias are used for test and rework purposes, they want to be able to insert
> wires inside the vias in case they need to change the board configuration.
> Any ideas on what to do with the wave process to resolve this issue?
>
>
>         Any ideas would be greatly appreciated.
>
>
>
> Jorge Rodriguez
> Process Engineer
> Varian Electronics Manufacturing
> 615 South River Drive
> Tempe, AZ 85281
> Phone: (480) 968-6790 X 4258
> Fax: (480) 829-4000
> E-mail: [log in to unmask]
>
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>

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