Meaning of those pads at the border of some perfboards

[tonyfer]

Hi everyone,

Does somebody know what is the meaning of these pads showed in the picture and how can we use them?


Thanks,
Antonio

[Terrius]

I'm guessing they are so you can connect multiple prototype boards together? They seem to line up with the columns of holes so my other guess would be to use them as attachment points for your VCC/GND so that you can create bus rails?

I've always wondered what their intended purpose is, I've never bothered using them for anything.

[tonyfer]

Look at this board. There is no alignment between those pads and the holes.

[Red Squirrel]

I wonder if they are meant for inserting into a slot, is there any slot types that have that spacing?  Could be handy.

[tonyfer]

Yes, I had also thought about slot connection. But there are some problems: the board needs to be cut exactly at the same size as the female slot, the solder would invade the entire space of the pad and leave very little space to attach a wire to the main holes of the board. The boards in the first picture I showed are too small to connect to a slots. In the second picture, the board is single-face and double-face are usually used in slot connection to avoid bad contact. So, for me, these pads doesn't make any sense in these boards. There should be some historical reason or some mechanical explanation for these pads.

[xrunner]

Aren't they simply solder pads for external wiring? 

[tonyfer]

It could be. But there are no holes. If so, this technique would mix "surface mount" with "through holes" exactly where the junction between two boards would be mechanically favorable to the use of the "through holes" technique ("through holes" are mechanically much stronger than "surface mount"). That would not make sense either.

[tonyfer]

Perhaps these pads are used only in the factory for drilling control, allowing alignment of the drills with the mask of the pads. They would not be to be used. Anyone who knows the manufacturing process of these boards could confirm this?

[tablatronix]

I know you can solder to these horizontally, Like on edge. I am going to bet the larger one that does not line up is 5mm for large terminal block spacing.

I checked mine just now, and it seems I have some that are .1" pitch aligned and another that is odd, seems to be ~4.18mm I do not have any 3.5mm terminal blocks to check alignment on. Cant think of any other pitch, besides 2mm every other perhaps ?

EDIT:

4.20mm (.165") is molex pin pitch

[tautech]

It could be. But there are no holes. If so, this technique would mix "surface mount" with "through holes" exactly where the junction between two boards would be mechanically favorable to the use of the "through holes" technique ("through holes" are mechanically much stronger than "surface mount"). That would not make sense either.

Think of them as just pads around the periphery for I/O's. Strain relief can be accomplished with cabling threaded through an adjacent TH and onto the pad.

There's heaps of variants of prototyping perfboards with all manner of edge pads, some are quite neat like eurocard styles and others are the most BS basic. Want something to suit a particular style.........spend some time looking for something that suits.