I want to make a decent PCB

[mstechca]

I have Ivex Winboard, and Ivex Windraft on my PC. I used Ivex Winboard to create my ROM programmer schematic, and in the schematic, there are about 8 or so IC's (I haven't counted them :lol: ).

I was able to generate a netlist and convert it to Winboard, but since I do not and cannot afford Specctra autorouting program that should have come shipped with Windraft, I cannot have it route the tracks for me.

HOWEVER, I took advantage to the fullest extent and use the built-in netlist utility. The good part about it is that it shows me how to connect each track in turn.

The problem is that when 1/2 the circuit is complete, the next connect it shows works best IF i cut across several tracks at once. No track can touch any other track, because if it does, the chances of a short circuit have risen.

I want to know if any of you guys have actually routed a complex PCB yourself and how you did it. I am willing to thin my tracks, but going less than 0.4mm is asking for trouble. I am able to squeeze 2 tracks between 2 pins of an IC.

Are there any tricks to a perfect PCB? if there are, I would like to know.
I want to avoid downloading anything else.

And what is the absolute smallest size a track can be without having the track broken by the heat of a soldering iron. and a drill hole? (I think mine is 30W or 45W, I'm not sure).
Also, I drill my holes after developing and after etching the board.

 

[rancid rock]

"GOOGLE it"

 

[eblc1388]

No track can touch any other track, because if it does, the chances of a short circuit have risen.

Good spirit.

Most people would assume they already have a short circuit. May be you have a better chance of not having a short circuit even if you touch the tracks together.

 

[justDIY]

The problem is that when 1/2 the circuit is complete, the next connect it shows works best IF i cut across several tracks at once. No track can touch any other track, because if it does, the chances of a short circuit have risen.

I want to know if any of you guys have actually routed a complex PCB yourself and how you did it. I am willing to thin my tracks, but going less than 0.4mm is asking for trouble. I am able to squeeze 2 tracks between 2 pins of an IC.

assuming you're doing most of your routing on the bottom layer, you need to put in some via's and jump to your top layer... then once you have bridged over the traces, another via back down to the bottom layer. now set the drill size on your vias to something realistic like 0.032". now, you don't have to etch a double sided board, you just do the bottom layer, and solder in jumper wires into the via holes.

i wouldn't thin your tracks down ... it increases the chances they will get washed out during etching. just because the program lets you draw tiny tracks doesn't mean your fabrication process will let you get away with it . using photolithography I've sucessfully made 12 mil tracks, but I generally try to stick with 24 mil

 

[mstechca]

assuming you're doing most of your routing on the bottom layer, you need to put in some via's and jump to your top layer

I only use one layer. I'm using a single-sided board.

i wouldn't thin your tracks down ... it increases the chances they will get washed out during etching.

I'm not using a marker to draw my tracks. I use the photo transfer method (print the tracks on a transparency, expose the board with the transparency on it under bright light for an hour, and then etch). I can't see anything being washed away.

just because the program lets you draw tiny tracks doesn't mean your fabrication process will let you get away with it .

Sure it does. I explained it above.

using photolithography I've sucessfully made 12 mil tracks, but I generally try to stick with 24 mil

I don't know mils, but I can successfully make tracks that are 0.6mm wide.

"GOOGLE it"

It is kinda hard to google it when I am referring to a specific program and a specific feature.

 

[DirtyLude]

Unfortunately there's no autorouter that's going to perform magic for you. I haven't worked with extremely expensive commercial products, but most are only good for simple tasks and you can always manually do a better job.

There's no real tricks here. You have to move components around constants, try and retry routings to see what the best placement/routing is that will cause the least routing conflicts.

There are times when you just have to resort to via's. If you want you can get 0 ohm SMD 1206 resistors if you dont want to drill holes, which will allow you to 'jump' a trace, but I wouldn't overuse that.

 

[mstechca]

I wasn't expecting pure magic, but I hoped for some insight from someone that may have had experience making complex PCB's on a CAD program.

thanks anyways.

 

[jrz126]

I want to know if any of you guys have actually routed a complex PCB yourself and how you did it. I am willing to thin my tracks, but going less than 0.4mm is asking for trouble. I am able to squeeze 2 tracks between 2 pins of an IC.

That will never work...I doubt a professional PCB manufacturer would be able to do that. Are you able to set up any sort of spacing rules in your software?

Are there any tricks to a perfect PCB? if there are, I would like to know.
I want to avoid downloading anything else.
.....
.....
I wasn't expecting pure magic, but I hoped for some insight from someone that may have had experience making complex PCB's on a CAD program.

thanks anyways.

Dude, several experienced people gave you plenty of good advice. Sounds like they told you that you were making your board wrong, so you choose to ignore it?

Maybe some pictures would help...

assuming you're doing most of your routing on the bottom layer, you need to put in some via's and jump to your top layer

I only use one layer. I'm using a single-sided board.

You add little jumper wires to the top layer. This is the first PCB I made.
**broken link removed**
I had a lot of tracks that needed to jump. As you can see, I added several jumpers. (about 40 total )

oh and 1 mil = 1/1000 of an inch.

 

[mstechca]

I wasn't ignoring anyone.
But for some reason, todays motherboards are built without 50 gazillion jumpers.

 

[Nigel Goodwin]

I wasn't ignoring anyone.
But for some reason, todays motherboards are built without 50 gazillion jumpers.

Todays motherboards are multi-layer, so you can't see the jumpers as they are on an internal PCB layer. Most motherboards are probably four layer or more?.

With a single layer board you generally need jumpers - though I doubt a single-sided PC motherboard PCB, using todays technology, is possible?.

By clever design of your single sided PCB you can reduce the number of jumpers - but there's no point getting too carried away about it!.

 

[DirtyLude]

I do toner transfer and don't have any problem running .3mm traces between standard PDIP pins. You should be able to get away with that fairly easy with photoresist.

If you want to, you can do double sided board as well. It takes a bit of lining everything up, but I have successfully done this a few times.

 

[justDIY]

i think that 0.3mm (aka 12 mil) is about the smallest most pcb fab methods can support ... most small order fab houses (which use photoresist) usually draw the line at 12 or 16 mil (0.3 / 0.4mm)

I did find a house claiming a minimum trace width of 8 mil (0.2mm), which is pretty impressive

 

[philba]

really? Most houses I've seen do 6-8 mil min.

I do dual sided toner transfer boards with 12 mil traces all the time. You have to manually insert wire in your vias but that's pretty easy and you have to remember than you don't get plated through holes.

I hand route all my boards. I use eagle and it's autorouter is, to be kind, complete garbage. But so are most others. Friends don't let friends autoroute.

It's really not that hard to manually route your board. Before you actually route, spend some time playing with the layout. The goal is to minimize the number of crossed air-wires. Don't be afraid to move everything around. look at swapping pins or gates to help get a simpler layout. Then, route the short, obvious wires. Now plan your Vcc and gnd. I often run Vcc on the other side of the board and use vias to drop the power down to the chips. The rest of the wires should route ok now.

Don't be afraid to start over if it's just not working. I often start with one layout and if it gets really messym I punt it and start over. At least i know what doesn't work well.

 

[Oznog]

Fabs I know do 10 mil or 8 mil for no additional charge.

Eagle is a great program BTW, and has a pretty effective autorouter for two sides boards. You can set it to not use the top layer and thus make a single sided board, but unfortunately many boards are impossible to do without jumpers and Eagle's autorouter is in no way close to laying out effective jumpers. That is, it leaves the traces unrouted and a jumper would often have to go diagonally across the board and cross over other jumpers and components.

Sure wish Eagle had a better strategy for this.