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Topic: Homemade pcb with Photoresist method (Read 4081 times) previous topic - next topic

allanhurst

I had that problem years ago with a laser printer on acetate, giving 'whiskering' which had to be cleaned up.

My through hole plating was a bit of 22swg tcw.

I generally used pre-coated boards from eg Farnell.

double sided by drilling marker holes through  the acetate and board to align. Ferric chloride etch in an agitated bath.

Long time ago.

And no good for fancy stuff. But quick. Well, quicker than the slow boat or the local specialist. And cheaper . Back in the 90's I paid about £200 for a batch of 10 smallish double sided plated-thru  boards with a 7-day turnaround.

Allan

aster94

Using the negative method i find that most printers cannot do large areas of dense black weather they are inkjet or laser.
i agree, i tried to do it on a simple paper and my printer wasn't able to do it all black

larryd

The link I made in post #1 mentions my method using an 8600 ink jet printer with clear overhead material.


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aster94

Another important question:

Which do you consider to be safe values for the width of the traces and the isolation? Obviously talking about homemade pcb

I use 16mil for the traces and 24mil of isolation,, you?

larryd

I like 25mil traces 50 and 75 for power and grounds.
15 mil in tight places.
Use ground/power plains.
Thermal relief vias as needed.

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CrossRoads

Ground vias also to connect the top & bottom ground planes.

More ground plane area also equals less copper to be removed for faster etching.

A trace width to current carrying capability calculator will show that 10 mil wide trace of 1 oz thick copper can carry 1A current with minimal temperature rise over the length of the trace.
http://www.pcbco.com.au/tracecalc.html
For example, I entered 1A, 10C rise 1 oz copper, 20C ambient, 20mm trace length (2cm, getting close to an inch).
A 10 mil trace is all that is needed.
So 10 mil for mA or uA signals is all you need, and nearly 2A supply current can be met with a 25mil wide trace.

Use ground planes, don't snake ground traces all over the place.

I'm pretty sure there are other calculators which use the latest IPC model where you can enter width, length, thickness, etc. and get a current capacity out of it, but I'm having trouble finding one. Most seem to go other way, start with current etc and get the needed trace width.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

larryd

#36
May 18, 2017, 06:46 pm Last Edit: May 18, 2017, 06:51 pm by larryd
Old eyes and shaky hands like 80 mil pads for PTH components.
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aster94

@cross I used the same calculator once. i needed to make a bench power supply, and since i doesn t have any idea about these formulas i found it very helpful. Anyway i use 16mil instead of the 10 because i am scared to "lost" a trace with the homemade process

@larryd you use very big traces! Is it due to the current of your pcb or for the method you use to make them?

CrossRoads

'Old eyes and shaky hands' is why MrsCrossRoads puts parts on the boards we build.
I can handle solder paste with a stencil, and sometimes have to do a board a couple of times when the stencil alignment is a little off, or I was a little uneven with squeegee pressure, or the paste got too thin over some pads while I squeegied, lots of ways to mess that up.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

larryd

IMO larger width traces have very little drawback.
Larger traces gives: more surface contact to the substrate, less resistance which can help in less noisy signals and more heat tolerance.

I am not a fan of widths 10mils or less, especially if there is room for say 25mils.

Narrow widths have their place especially with high density designs.
However, it doesn't seem reasonable to have a 60-80mil pad and then an exiting 10mil trace especially if a wider trace can be accommodated.

Do not forget to incorporate good path way layout and proper power supply decoupling.


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larryd

"is why MrsCrossRoads puts parts on the boards we build."
Make sure you revisit her salary now and then.   ;)


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CrossRoads

Well, she is driving a new 2L Turbo Convertible Beetle these days ;)

Actually it's a 2015, someone had traded it with just 1450 miles, on it, so we got a great deal on in it in December.  Baby blue, just like the '67 Beetle I had in college, that I taught her how to drive a standard in, only this one's got way less rust and the heat works and it has AC and it'll go more than 70mph on the highway without shaking 8)
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

allanhurst

I take it , like Bob Pease, you're fond of old beetles. My brother had one, and I thought it was awful....

Allan

CrossRoads

Not me, was just a car I could afford as a poor college student. It was gone when I went off to senior year, tired of dropping the engine to fix oil leak that made the clutch slip and ongoing electrical problems ...
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

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