D.I.Y. double sided PCBs NO plated through holes.
Whenever I make a PCB board, I try to limit the design to a single side with jumpers. For 80% of the time I am quite happy with the results. These are made from positive pre-sensitized 1/16” material.
Every now and then I need to use a double sided design as the jumper method will not suffice. For years now I have used a method described below, IMO, a reasonable alternative to the double sided PCB with plated through holes.
Step:
Design a double side circuit board with your favorite PCB software.
Purchase pre-sensitized singled sided 1/32” (thirty second) PCB, cut two pieces slightly larger than your board size.
Transfer the top side of your board (MIRRORED) to the first 1/32” material as per manufacturer’s instructions. Etch, and cut to the final size.
Transfer the bottom side of your board to another piece of 1/32” material. Etch & cut to size.
As accurately as you can, drill the two boards.
Mount/solder your PTH components on top of the PCB and SMDs on the bottom (use thin 1206 or smaller). You only need to solder a lead if it goes to a path on this board. Do not cut off the PTH leads! KEEP YOUR FILLETS SMALL and LOW.
Slip the second PCB over the component leads in step 6 (which can be frustrating) and solder each PTH component lead. Mount bottom SMDs to the foil side of the second PCB.
Since you are soldering two PCBs stacked on top of each other there is no need for plated through holes (I keep VIAs to a minimum by using the existing PTH component leads).
Obviously there is some distance between the two 1/32” boards as the fillets and any SMDs will be on the BOTTOM, foil side, of the TOP board.
The next time I make one of these I will add a picture of it to this post.
Hope this method works for you as it has for me.
I'm having some trouble understanding what you mean.
Is it:
"layer" 1 - Through hole components
"layer" 2 - PCB
"layer" 3 - SMD components and soldering the leads of the through hole components you need on this layer (soldered to the layer 2 PCB)
"layer" 4 - Another PCB
"layer" 5 - Soldering the leads from the through hole components
Am I getting it right?
Also, I'm having trouble understanding what you mean when you say plated through hole vs. via.
Plated thru hole vs via - look at your Uno board. The little tiny 12mil (0.012 inch) dots where signals go from one side of the board to the other are vias. The Large holes that component leads go into that have decent sized pads for soldering are plated thru holes. The hole inner diameter is like 35mil, and the outer pad shape is larger. Can be square (usually indicates pin 1), round, octagon, over shaped, offset oval shape, I think those are common choices in eagle anyway.
Think of the 2 boards as 4 layers, 1Top 1Bottom, 2Top 2 Bottom.
1Bottom will sit on 2TOp.
Components will then mount on 1Top and 2Bottom. Thru hole components will have their legs soldered to 1Top and 2Bottom.
1Bottom and 2Top have no traces.
Yeah, I understand that, but it all pretty much goes down the drain when discussing low tech DIY manufacturing.
On the UNO PTHs are primarily there for mechanical support and not electrical contact, right? Vias are used for connections.
Also, when talking about DIY, are you actually plating the through holes?
If you look at any board, like the Uno, you will see that many PTHs are also used to transition signals from top to bottom, so not just for holding a part in place.
This method uses the leads of devices as a poor-man's PTH.
Hobbyists do not have the means to actually plate the holes. Best you can do is solder a wire (or a device lead) to pads on both layers. Maybe glom enough solder in a hole so top & bottom make contact.
Yeah, that's how I made vias last week when I really had no choice but to do double sided.
The toner transfer method on the vinyl was pretty accurate. I managed to line up the layers well enough. I made 1.5 mm diameter pads for vias and when drilled with 0.8mm bit through the center on one layer in most cases entire hole was inside the pad on the other side. On some it was just partly outside but still easily solderable.
All in all I botched it on several fronts so the final board looks messy, but it is fully functional and since it was my first 2 sided attempt it was more of a proof of concept.
