Virgil,

This still sounds like a solderability issue on the mounting hole  The
solder reflowing and forming into a ball indicates non wetting.  If the
solder is hot enough to reflow it should not form into a ball unless it
never wetted to the pad that it is on or is de-wetting.

Ken





 (Embedded
 image moved   Virgil Lenton <[log in to unmask]>
 to file:      05/26/99 01:39 PM
 pic00210.pcx)




To:   Kenneth Kirby <[log in to unmask]>
cc:    (bcc: Kenneth Kirby/ElectrovertUS/Cookson)
Subject:  Re: [TN] Solder balls forming on top side during wave soldering.




Ken

As you previously requested, here are some pics of the
solder balls.

The PWB's in question are HASL plated. We currently have a
board out for solderability testing.

The thermal properties of this board make it a little
difficult to wave. The bottom side of the board is one big
ground plane. The mounting holes are connected to this
plane, which probably explains why enough heat is being
transferred to the top side to cause reflow.

We manually added flux to the topside of the mounting
holes thinking it might improve a solderablilty problem.
The flux got hot enough to sizzle and the solder balls
continued to form.

I now think that what is happening is that the plating on
the topside and within the PTH is being heated enough to
become molten but not hot enough to properly flow.
Spot mask pressure against the side of the PTH forces the
solder up. Since it isnt flowing well but still has to
accumulate somewhere, it forms balls. Does this sound
logical?

We have tried many solderwave settings trying to solve the
this problem. Current settings seem to be optimum. Any
setting changes seem to cause poor flowthru or solderpeaks.
We may have to mask the board from top and bottom and live
with the extra time taken to do so.

Thanks
Virgil

On Fri, 14 May 1999 11:23:22 -0500 Kenneth Kirby
<[log in to unmask]> wrote:

>
>
>
> Sounds like you already know the problem.  Are these
boards HASL,roller > plated or ???    I would however
question why the solder is being reflowed > on the top of
the board if the bottom side of the pad and hole is solder
> masked.  You may have to reduce your topside board
temperature during > preheat or increase the conveyor speed
to reduce the contact time in the > wave to prevent the top
of the board from reaching reflow temperature.  One > or
both methods may be required depending on your current
setting.  I would > also have to question the plating
quality of the boards so maybe a board > dip solderability
test is in order and a talk with your board vender.  IPC >
spells out the board solderability test in ANSI/J-STD-003.
> >
> Ken Kirby >
> >
> >
>  (Embedded >  image moved   Virgil Lenton
<[log in to unmask]> >  to file:      05/14/99 10:13 AM
>  pic32359.pcx) >
> >
> > To:   Kenneth Kirby
<[log in to unmask]> > cc:
TechNet@IPC>ORG@COOKSON (bcc: Kenneth
Kirby/ElectrovertUS/Cookson) > Subject:  Re: [TN] Solder
balls forming on top side during wave soldering. >
> >
> > Thanks for your quick response.
> No, the pot does not have the Omega option. > No, it is
not coming from a hole close by. > Ive watched the
solderballs form with my own eyes. It is > like the plating
is becoming molten and then dewetting to > form
solderballs. I'll see if can arrange some pictures. >
> On Fri, 14 May 1999 08:31:47 -0500 Kenneth Kirby >
<[log in to unmask]> wrote: >
> > > >
> > > > Virgil,
> > If you can get pictures of this it would help.  Does
the > > new pot have the Omega option?  If so you may be
running > it > too high and it is forcing solder around the
mask and > into > the mounting hole.  Could the solder ball
be coming > from > another through hole close by?
> > > Ken Kirby > > Product Specialist > Speedline
> > > > > >
> > > > >  (Embedded >
> >  image moved   Virgil Lenton <[log in to unmask]> > >
>  to file:      05/13/99 04:14 PM > > >  pic32295.pcx) >
> > > > > >
> > > To:   [log in to unmask] > > cc:    (bcc: Kenneth
Kirby/ElectrovertUS/Cookson) > > Subject:  [TN] Solder
balls forming on top side during > wave > soldering.
> > > > > >
> > Hi > We are having a problem with solder balls forming
> around > and in mounting holes that have been spot
masked. > The > problem seems to have surfaced after
upgrading our > Hollis > wave machine to use an Electrovert
Lambda Wave > Solder pot. > Other than the Solder balls
forming, > soldering quality is > very good.
> > > Any Suggestions would be appreciated. > > > Flux -
RMA thinned to Manufacturer's recommendations. > > Spot
Mask - Tech Spray Water Washable > Solder >
Temperature(SN63) - 500F > Top Board Temp before solder pot
> - 200F > > > Thanks > Virgil


----------------------
Virgil Lenton - Manufacturing Engineering
SED Systems Inc   18 Innovation Boulevard
P.O. Box 1464    Saskatoon, SK    S7K 3P7
Ph. (306)931-3425       Fax (306)933-1486
Email:[log in to unmask]