Do DIP holes function a thru-vias?

I'm routing traces for my first ever PCB and I want to make sure I understand how the component traces work. For surface mount and BGA/LGA components, the traces always have to start on the top layer and have to use vias to get to other layers, but DIP component traces can start on any layer, right? So do DIP holes essentially function as vias? Like can I use the GND pin hole for a DIP chip to simultaneously route a GND trace to another layer?

Yes - the holes for through-hole components are normally plated through holes, so they act as vias.

Awesome, thank you! Follow-up question, could I use an NC pin hole via as a cost saving measure, or does running signals/power to an NC pin risk damaging the IC?

DrAzzy: Yes - the holes for through-hole components are normally plated through holes, so they act as vias.

But you must solder both top and bottom for this to work. Some components aren't amenable to this as the pins come direct from the underside (relays, non-axial electrolytics).

Raddy13: Awesome, thank you! Follow-up question, could I use an NC pin hole via as a cost saving measure, or does running signals/power to an NC pin risk damaging the IC?

Depends if it really is not connected, or is actually a don't-connect. Probably worth checking with a multimeter to be sure - if a pin is infinite resistance to all the power rails its almost certainly isolated.

I believe some N.C. pins on some chips are actually used for debug or production testing by the manufacturer. They would have an undocumented circuit attached to them with unknown specs. Best to leave those unconnected.

One can always bend the NC pins on a DIP part up out of the way and use the thruhole as a via.

If it will be a factory made board, a 12mil via can be placed just about anywhere tho.

MarkT: But you must solder both top and bottom for this to work. Some components aren't amenable to this as the pins come direct from the underside (relays, non-axial electrolytics).

No you don't, unless you have some weirdo board house that doesn't do plated through holes. They are plated through-holes, there is metal on the inside of the hole connecting the two sides of the board (and if you're soldering the parts on correctly, the solder should wick up between the pin and this plating)

Why would using a pin as a via be a cost-saving measure? Nowadays, typical board manufacturing prices are based on the size of the board (as well as number of layers, and extras like support for finer feature size or more expensive surface treatments). In the past it was commonplace to charge by the hole, or by the via, but that's not how it's done anymore. I get charged the same rate if I get a 4" x 4" piece of blank PCB with nothing on it, or if I put holes every 0.1" to make my own prototyping board .

Ah, you were talking about professionally manufactured 2-layer boards? All holes are plated through as standard. I thought you were talking about homebrew.

MarkT: Ah, you were talking about professionally manufactured 2-layer boards? All holes are plated through as standard. I thought you were talking about homebrew.

He didn't specify - but only a fool or a masochist would make a 2-layer board at home considering the prices for beautiful professionally made PCBs now.

DrAzzy:
…but only a fool or a masochist would make a 2-layer board at home…

While I do not make boards myself there are some on this forum who do. A few have mentioned making 2-layer boards.

In addition, high quality CNC machines are becoming readily available. Armed with such a machine making a 2-layer board is essentially child’s play.

I bring this up because calling such people fools / masochists might be considered a personal insult. Were you to call me either for making a 2-layer board I would certainly be insulted.

I suggest checking your assumptions and stop the name calling.

Armed with such a [CNC] machine making a 2-layer board is essentially child's play.

Meh. I have an LPKF. It pretty much sucks these days. You don't get plated-through holes or vias, you don't have soldermask, resolution is not as high as you need for modern parts, and tool cost is higher than you think. It was great for really small SS boards with DIP or maybe SOIC parts, at least until places like OSHPark started their $5/in^2 pricing. Now... I don't use it much any more, and I feel sorry for the people that think CNC is going to be "nearly the same" as professionally made PCBs.

I agree.
It can help you if you are in a hurry and you need a prototype board very very quickly. But, if the devices get even smaller packaged, this will increase the challenge.

In this case I help myself with little adapters and the prototype might be larger than the final release of the adapter- less pcb. But imho the meaning of a prototype is to show the expected function, not the best design.

I've made 2-layer etched pcb's for simple stuff when I was in a hurry. It worked, but not very pretty .

There are lots of people who'll do you very nice double sided plated through on FR4 with reasonable accuracy at low prices.

But for multi-layers, bga's, microvias, special (PTFE, ceramic) substrates , micron accuracy etc, go to a specialist and pay the money. At > 30GHz you have to be fussy. Printed filters require great accuracy and very small spacings..

Allan

DrAzzy: Why would using a pin as a via be a cost-saving measure? Nowadays, typical board manufacturing prices are based on the size of the board (as well as number of layers, and extras like support for finer feature size or more expensive surface treatments).

I was not aware of that, I thought more vias = more money to prototype. However, after reading through some prototype shop design guidelines, you're right!