First PCB

oh. I guess I should ask about the next thing to do. I will go ahead and try and use the photoetch method and see how that works then maybe the laser method(have to buy a laser printer first though) if it doesn't work well.

Two things I'm worried about are drilling the holes and putting some type of insulation over the trace. The smallest bit I have right now is 1/16 and I was thinking about trying to figure out some way to drill the holes easier. I do have a dremel and will try to do it by hand but not sure how sucessefull that will be.

Not sure about some type of coating to "spray" over the traces to protect them from shorting out incase some metal falls across them or something... surely there is something like this?

Thanks, Jon

I've done a lot of PCB design in the same way as you, for rather small circuits just drawing them by hand and sizing components.

I would suggest for a first attempt to make a simpler circuit, something with larger spaces between components, thicker traces, and larger pads. Instead of using the laser method (which is definitely a good idea for larger projects) you can just transfer the PCB design using a resist ink marker or even just a black Sharpe pen. Dip in the iron chloride solution etc.

You should try it with a trivial design fist so you get a sense of how much copper is etched away. Good to learn on a disposable attempt so you don't get too upset when more copper is etched away than you think, because this for example will break thin wires.

Anyway practice makes perfect

On Tue, 14 Feb 2006 19:31:05 -0600 in sci.electronics.design, Jem Berkes wrote,

Black Sharpie is terrible, IMHO. Best I have tried is a Staedtler Lumocolor #313 (Red) from the art supply store. The clear red lacquer ink does not have the porosity problem of the pigmented black ink. I would try a red Sharpie before a black one.

That's an interesting tip, the ink pigment has an effect on resisting the etching? I really don't know much about the chemicals. What I thought was a black Sharpie, by the way, turned out to be a pen made specifically for the job although it did look suspiciously like a classic Sharpie.

Anyway I have comfortably made a lot of boards just using pen and ruler. One trick I use to make sure the components are comfortably spaced for the physical clearance is laying a paper draft of my PCB board on a standard spaced perforated board. This way I can plug the components right in and see if everything fits.

The only thing I wish I had used all these years is a drill press. Drilling the holes has by far been the most difficult part for me, especially when I want to use something like an IC socket. Headache.

Use surface mount (SMD) components and you won't have to drill nearly as many holes! Sooooooo much easier when making your own boards. Stick to large size SMD devices (1206/0805, SO etc) and you shouldn't have any problems soldering.

Dave :)

One major suggestion would be to print the layout 1:1 on stiff paper and then try dry fitting all of the components. The default footprints may or may not give you the room that you'd really like to have when it come times to assemble it. You can, if needed, stand some of the axial components "on end" to free up real estate.

Your ground already makes just more than a complete circle. Consider doing a copper pour as a ground plane instead. You'll need to add thermal reliefs around the affected pads, of course. A benefit to doing a pour is that you end up with much less copper to remove.

Mounting holes?

--
Rich Webb   Norfolk, VA

Consider using a round-tipped high speed steel cutter like this

(note: never bought from these guys, their link just happened to be high on the googlelist). I've seen packs of them at many hardware stores so they're not hard to find. The rounded tip is a bit more forgiving about drilling angle. Use a spring punch to set a dimple before drilling.

jameco has a small drill press that might help, also. A little more flexible that I'd like but that's work-aroundable. Search their site for their p/n 26711.

Try "Testors 1601 Transparent Candy Emerald Green"

--
Rich Webb   Norfolk, VA

The (bigger) SMT parts are easier on the board for repairs, too. It takes only seconds to heat both ends of an SMT resistor (sequentially, quickly) to get it to come off the board... much easier than digging the leaded resistors out of their drilled holes.

Now, 0402 size parts are a bit tougher to use...

Drilling: a dremel in a drill press made for the Dremel and ball end dental burrs. The burrs are *vastly* superior to drill bits.

Etching: do *not* get ferric cloride on anything. It *will* stain. Agitate while etching and keep the solution warm with a hot plate. If you are going to do a lot more in thr future, get an etching tank made for the purpose that has a heater and an air bubbler.

Ed

Are these the little drill bit like things that have different shapes at the end and look like iron bits or something?

I was thinking about trying to do it by hand at first and see how that went ;/ Then try to make a simple press... and then order one later.

I got that. I made a glass tank that has a heater and bubbler in it. I tried to make it thin so I wouldn't have to use so much etchant in it to do smaller boards.. Not as thin as I like but hopefully will do the job.

Thanks, Jon

I did that at first. I printed the pcb on paper then stuck the paper over some styrofoam and stuck the components in to get an idea. It seems to come out ok. Some things are bit close but it looks like it will work. I might have to change some things if I need to add more room but I think I might just try it as is so I can actually get into etching the pcb.

I thought about standing them up like you said but that was after the fact ;/ I might end up redoing it but I doubt it. I just need one working on for now so I can get my psu working to do other more important things.

Not sure what you mean by this. Complete circle? Does it count even if they don't connect?

I added some large copper areas's that you can see.. they are not grounded but I wasn't sure if I should do that or not since it makes the possibility of shorts more likely? Those large black regions can easily be extended to include the ground... I mainly did them though to take up space so less etchant was used. Is it ok to "hook" them to ground?

Heh, something I forgot ;/ Wasn't a big deal though as I can mount it by just glueing it down or something(not a good way but good enough for now). Maybe some hot glue or something like that.

Thanks, Jon

ok. I think I have some of those that came with the dremel. I was thinking about trying to use them since they are much smaller than what I have as a "normal" drill.

ok. I will try to do it by hand first just to see how far I can get. If its to hard then I will probably try to rig a quick press up from something and see how that works... then I'll look to buy one.

ok. Thanks.

Thanks, Jon

Yeah, I brought a marker to do this but I don't think its a good idea. Seems much harder to do IMO unless you have very large traces(like 1/2 in thick or something). Although you are right that I should play around with it anyways. Might not be as hard as I think. What I was planning on doing was make two or three as sure I will either mess up in the etching or in the drilling.

Actually when I was doing this I thought I made the pads and traces etra big but it turns they are not to big ;/ They looked huge in the pcb editor ;/

I'm not worried about screwing up to much as its just hobby but I do want to get the pcb done so I can get my psu working to do other projects... hopefully I will get lucky on the etching and it will come out decent... I think I can handle the drilling after a try or two.

Thanks, Jon

I thought about doing this but I was wondering how you keep from overheating the components? I thought they used some method like reflow or something to do SMD and you had to bake them?

Thanks, Jon

Most surface mount components, with the exception of BGAs can be soldered conductively, by hand. The method you use depends on the device, but in general I use a technique that the instructor refered to as the dry tack method. A simple example: you want to put an 0805 resistor on the board. First, use a flux pen to put a small amount of flux over the pads. Next, position the resistor on the pads and press down on it from the top with a pair of tweezers (small curved ones help) as does resting one end of the tweezers on a flat surfface. DO NOT hold the device with pliers or tweezers on the sides - press down on it from the top. Use your soldering iron and touch it to one end (pad and component) of the device, which should quickly change appearance to look wet and then remove the soldering iron. The device should now be tacked in place. Solder the other end of the device by placing your solder (wire) where the pad and device meet and then briefly touch this with the iron and you should get a nice solder fillet. The amount of solder to use depends on the the solder thickness and the device size - but I typically use about 1 pad width with 0.38mm solder on an 0805 part.

Well I guess after doing one, its easier to keep on going. One trouble, sometimes the part will move while heating the second pad with heat applied. Holding the tweezer down is sometimes necessary. Little tiny caps do this easily.

greg

In general what is wrong with using tweezers to hold it?

I have made a couple of boards and found PCB Wizard, very simple to use and as you spend more time with it can do more things than I will ever do, the best thing it as $49.00. The board looks great, how did you do all those lines? I had used the press on stuff from radio shack and that was still hard for me...I used the etching process and added a aquarium heater and aquarium pump to somewhat agitate the material.

I found a "drill press" rig for my drill which enables you to drill straight down for each hole.

The problem with holding the part on the sides is that it causes the part to be lifted and it leaves a gap between the component and the board. This in turn changes the mechanics of the fillit that forms which affects the mechanical strength of the joint. When I took the SMT training and certification classes (IPC Class 3 standards) , I made this mistake once and was quickly corrected.

With a little bit of practice, you will probably find that it is MUCH easier to simply push the part down than to try and hold as the stability is dramatically improved. As I said, a small pair of curved tweezers works best. Set the butt of the tweezers on the table, holding them like a pencil. then use the point of the tweezers to press down on the device. The stability this way is good enough that you can align and tack both small chip components and 200+ pin flat packs.