Pcb Making

[dirtyhanfri]

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.

 

[boji]

"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]

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.

 

[boji]

"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]

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]

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.

 

[gyraf]

You can get spray-can solderable flux laquer, named SK10 iirc..

Jakob E.

 

[buildafriend]

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,

 

[dirtyhanfri]

What ratings are the laser?

It’s a 5W laser diode savaged from a laser engraver kit from AliExpress.

I run it via PWM but actually always run at full power, for pcb work it seems like it could work maybe at 60-75% power but why take the risk? Two passes at full power 400mm/sec and you can see shiny copper even through the green laser protective googles.

Today I’ve been doing a laser 19” front panel, powder coated.

I had problems with my big CNC machine losing steps so I had to avoid doing traditional engraving.

Just placed it in the laser, fixed with double sided tape and it took off the powdercoat easy and nicely, no stress about 0.1mm bit tips breaking or lack of flatness of the surface messing up the whole piece.

It’s funny how a device I bought almost as a toy is giving me nice results, I think I’m gonna buy another one as a spare.

About double sided pcbs, with my current jig should be feasible, just need to get some double sided pcbs to try.

I tried laser engraving silkscreen top layer on single sided boards, which is basically the same as doing double sided boards. and the alignment is reasonably good for the alignment method I used.

 

[dirtyhanfri]

Just an update.

After some boards, I realized the etched lines were so narrow, so I had some hard times soldering the boards.

So I tried to tweak a bit the CAM settings, and instead doing two passes in depth, as the second one wasn't really needed. I set it to one pass, but added a second engraving, programmed setting a bigger tool (I'm using 0.1mm tool width usually), so it offsets a bit to the outside, giving me bigger exposed areas, resulting in better and faster etching, and also way more comfortable soldering.

I also changed the order of the steps, as etching the boards with the drilling done resulted in etching solution eating copper inside the pad, around the drill.

So now, I etch the boards just after engraving them. I'm using barley hot Ferric Chloride with an sponge and works like a charm, but it's dirty stuff...

After etched I drill and cut them to size in the CNC. No problems with pad lifting by the moment.