dirtyhanfri

Pcb Making
« on: June 30, 2018, 02:18:25 PM »
Hi guys

As I promised a few months ago I'm gonna share my pcb fabrication method, it evolves different processes and methods but seems to be a reliable way to get pcbs properly done.

I'm trying to show the steps, I'm not any kind of expert, but this method seems to work fine for me.

****DISCLAIMER*** PLEASE READ***

I'm just showing you how I do it, don't do this at home if you're not absolutely sure about what are you doing. Lasers can damage seriously your eyes, CNC routers can take one of your fingers in a fraction of a second, Acids evolved for pcb etching are bad for skin, lungs and eyes, FR4 dust coming from drilling and cutting pcb's is really bad, don't breathe it. Used acid with copper particles should be disposed accordingly to your local regulations, don't drink it.

I'm not advising to do the same as I do and won't take any responsibility if you damage yourself, or others while trying to replicate this

***END OF DISCLAIER, LET'S GO WITH SOME INTERESTING STUFF***

Jigs and other details about how to get the job done should be adapted to your needings and way to work.

First of all, I buy 130x180mm copper clads, no UV sensitive, just plain copper over a FR4 board.

Then I drill some 6mm holes in the boards, which will be used to hold the board during different steps.

I need these holes to be exactly in their position, so I do it in a CNC Router, five boards at a run. I built a simple jig with marks for the boards, and programmed a simple Gcode program to drill the holes with the same distance between them, nothing fancy, but as the boards doesn't have the same exact size, I found this is the most reliable way to get them done.

I just stick the boards using double sided face, as it's just drilling operation and no horizontal forces are evolved, it keeps the boards in place



After drilled, we're going to paint them black. Clean the boards with some alcohol and compressed air to get them free of dust and particles. Then I hang them in a corckboard with some nails, which are inserted in the holes, holding the pcb with the copper looking to the external side.

Get the cheapest black paint spray can and paint the board trying not so use so much paint but getting them with a consistent black cover, I use to do 2 light passes, with a pair of hours between them, you don't want or need to get a hard paint coat, we're going to remove it few steps later.

Never tried with different colors, but I thought matt black would absorb more light power than other colors



Once the paint is dry, I attach the board to their jig using 4x6mm pins, and mount the jig in my sightly modified 3020 CNC Machine.



This machine is running GRBL via a Rpi, with bCNC as gcode sender.

First of all, I run a laser program which draws the isolation lines between traces, as well as a x0,y0 point, which I'll use as a reference for drilling and cutting operations.



I'm using a 5,5W Laser diode module driven by the PWM signal coming from Pin 11 in Arduino, this way I can manage the laser power according to my needs via GCode.

My parameters are: Feedrate: 500mm/min, laser: Full power, 2 passes

Now, you should clearly see the exposed copper which will be removed afterwards.

After that I mount a 0.8mm bit in the milling head of the CNC and position it in the x0,y0 point I engraved previously.



For this purpose I have a endoscopic USB camera attached to the CNC, bCNC has a nice solution for camera probing easy to configure and reliable.



I run all the drilling operations with different drill sizes and then a cutout program with a chipbreaker bit.

In this program I let some holding tabs in order to keep the pieces in place inside the big copper clad.

I clean all the dust in the board and give it a bit of alcohol with a paper towel, just enough to clean the exposed copper while not damaging the paint.

Then, with clean and dust free boards, we're going to etch them in our favorite etching solution.

I don't show pictures of this process as I' not happy with it at the moment, just a simple plastic container with etching solution and an aquarium pump



I'm toying with the idea of laser engraving silkscreen layer of the pcb on the top side, perfectly doable with my jig system with reasonable aligment results, I did some tests and it will work after adjusting laser power and speed.

This leads me to think in double sided boards, that's my next challenge.

That's all I have by the moment. For board protection I use pine resin based varnish which helps with soldering and stopping oxidation.

I'm looking for a reasonable way to put solder mask on the boards, if possible. I tried with those ebay UV curable soldermask paint few years ago and they're really messy and hard to deal with to get consistent and repeatable results. Maybe those film sheets work nicely, but seeing videos in youtube it seems to be tricky at least.

Looking in perspective, the time needed for learning and experimenting (almost 3 years, you know, life) maybe I'm crazy but damn, I can have a working prototype with a walk to the electronics shop and a morning in the shop.

Also, the learning process and the feeling when things come together pays every hour invested in this.

« Last Edit: June 30, 2018, 02:21:38 PM by dirtyhanfri »
Working on it...


boji

Re: Pcb Making
« Reply #1 on: July 01, 2018, 01:54:59 AM »
Quote
"I'm using a 5,5W Laser diode module driven by the PWM signal coming from Pin 11 in Arduino"

Sexah!  U made my day Dirtyhanfri.  :)

 So, have you ever ablated powdercoated aluminum with your laser? Does it sufficiently expose the aluminum beneath? I ask because I'd like to cermark what I could exposed to get scratch resistant color engravings by finalizing with a powdercoat clear finish.

dirtyhanfri

Re: Pcb Making
« Reply #2 on: July 01, 2018, 04:00:22 AM »
Hi Boji

Glad this helped you. I didn’t get much into details in order to avoid a too long post. Getting the laser to work with pwm signal was a bit tricky.

Basically I had to use a modified post processor in my CAM software, it sends a M3 S1000 code before any movement except G0’s which start with a M5 code to turn off the laser for the rapid movements.

It’s a brute force approach, but it works flawlessly.

Also is worth to note PWM signal in Pin#11 is available in GRBL 1.1 (not sure if 0.9 too, but I advice to use GRBL 1.1) Not sure if previous versions have PWM signal in another pin.

Regarding powder coating.

I made some test with powder coated aluminum and it works nicely, it exposes the bare metal, never tried to put color on it.

Also works on anodized aluminum surfaces.

I’m writing another post showing my front panel fabrication method. It includes machining aluminum, anodizing and laser marking. Just waiting for a new current regulator for my anodizing jig.
« Last Edit: July 01, 2018, 04:04:16 AM by dirtyhanfri »
Working on it...

boji

Re: Pcb Making
« Reply #3 on: July 01, 2018, 07:43:59 PM »
Quote
"I made some test with powder coated aluminum and it works nicely, it exposes the bare metal"

Sweet that's reassuring to hear, using only a 5 watter. 

The cermark idea being you second pass the laser over the exposed area coated with laser color fixative.

boji

Re: Pcb Making
« Reply #4 on: July 01, 2018, 08:09:18 PM »
I appreciate your DIY kit, but you got me thinking about scooping one off evilbay so I can keep on with my current projects... 

When some sellers say '4 axis' do they mean 3 axis with laser power control or just on off?   I suppose this is what you figured out with PWM...

dirtyhanfri

Re: Pcb Making
« Reply #5 on: July 07, 2018, 06:34:09 AM »
Just an small update.

I etched a few boards this week using Ferric Chloride, and the results are way better than using the H202 + hydrochloric acid I used previously.

Other update I tried was using plumber's paste to protect the copper from oxidation. Visually results are good, even knowing this doesn't replace soldermask I think at least will keep the boards clean.

The method is simple as hell, just cover the boards with a good layer of paste and heat it using a hot air gun until the paste goes dry, then rinse in tap water and use a sponge to take out the paste.

The hardest part for me was try to make an even paste layer on the boards.

Working on it...

gyraf

Re: Pcb Making
« Reply #6 on: July 10, 2018, 04:12:16 AM »
You can get spray-can solderable flux laquer, named SK10 iirc..

Jakob E.
..note to self: don't let Harman run your company..

buildafriend

Re: Pcb Making New
« Reply #7 on: July 10, 2018, 03:52:08 PM »
Thanks for sharing  ;D

What CNC/laser did you use? *edit - I see 3020. What ratings are the laser?

For etching double sided boards drilling two small holes in the board somewhere helps me a lot with lining up dual layer PCBs. For your approach jigging perfectly with perfectly cut / square materials might be the key to double layer success?

All the best,
« Last Edit: July 10, 2018, 03:59:12 PM by buildafriend »


 

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