Bob:

As long as I'm on a roll, we can give this one shot.

With a well controlled wave solder system, you should not have any problems forming a good solder
fillet.  One problem you will encounter is replacement of the component soldered directly into
the plane.  Large quantities of heat are required to melt the solder joint on that component
(could require as much as a 60 watt iron).  One alternative is to use thermal reliefs on the
component lead and small vias tied directly into the plane to handle the power.  My sketching
skills using ascii characters are not very good.  If you would like a sketch, please sent me your
FAX number off-line.

Regards,
Don Vischulis
ITO Industries
[log in to unmask]

Bob Walker wrote:

> Hi All,
>
> I first want to thank John and Don for responding to my layer stack-up
> question. I now have a question concerning the need for thermal reliefs
> on a plane layer. I know that using thermals helps in creating a good
> solder fillet on the component side of a leaded component, but I was
> wondering how many designs are done without using them. Are there any PWB
> assembly houses that can comment on their experiences with running boards
> through a wave that doesn't contain thermals? A design that I am working
> on will contain a ground plane on the bottom layer (solder side) and I'm
> thinking that I might be able to get away without using thermals on it
> because it will not be an internal layer and thus will be making direct
> contact with the wave and not necessarily drawing off all of the heat
> needed to produce a good solder joint up the lead of the component . I
> will be using 2 oz. copper and have some high currents in certain areas
> that would make not using thermals a benefit in designing the board. All
> responses would be greatly appreciated.
>
> Regards,
> Bob Walker

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