Ground planes and wave solder

[audiox]

I visited the library of the local university today. While waiting my friend I studied an intresting book about PCB design (I don't remember the name or author anymore). It was written in late 90s but still there was a warning not to use large ground planes on the solder side of the PCB. The reason was that it collects heat from the wave solder and bends the board.

I think that was a good advise in the good old days when there was no solder mask. The bare copper collected thick layer of tin and a board with uniform ground plane really bended (cross hatch was used to avoid that).

Nowadays practically all boards come with solder mask that effectively inhibits solder stucking to the unwanted areas. So there is no reason to avoid to use bottom side ground planes anymore.

The author of the book must be expert in his area, so why he is distributing that kind of old information. Is there something that i haven't taken into account?

 

[Ptownkid]

Well, as we've seen many times before, there are a lot of topics in electronics that "experts" don't even unanimously all agree on.

 

[JohnRoberts]

A more likely reason for avoiding large unprotected ground planes is to prevent sopping up too much solder, while I have seen this done on purpose inside power amps to make traces lower resistance.

Another design consideration I recall from my old gig where we fabricated our own circuit boards was a house rule to fill in all empty areas with copper. The reason was to reduce consumption of the copper etchant. Of course an additive process might suggest an opposite rule.

Be careful about taking old design rules as law. Rules can change.

JR

 

[Ptownkid]

Be careful about taking old design rules as law. Rules can change.

Yup, this is very true. I always flood as it makes producing boards, via numerous different ways, much easier.

 

[PRR]

> bends the board.

So? Electrons go around curves.

I had a Hercules PC Video card that was so warped it wanted to set its far end in the next bracket over, 0.75" to the right of the slot it was in. Worked fine for most of a decade.

Also remember: the guys busy doing-it don't have time to write books.