PCBs (Part 3)

Part 1, 2, 3, 4

Once we have our gerber files ready, it is time for “printing” the PCB. For a long time (and a long time ago) I used single sided coated copper Bakelite boards. Then I would copy the circuit  on copper using a special permanent ink pen (in negative) and immerse the board in a iron perchloride bath… Well, I understand that you could laugh at that, however, it was a quite standard manufacturing procedure in the so called “radio clubs” in the 70’s, and I recently heard that a mixing table (deluxe type, featuring 8 channels !) that I made in 1978 is still operating in a band!

After that came the time of circuits drawn with bitmap editors (once again, I understand that it sounds like prehistory) printed on transparent plastic sheet (at the time of the overhead projectors…) using my good ol’HP 4L laser printer which was perfect for the job. Then I used these printed slides in a custom made UV light box. After a revelation step, the PCB would be immersed in a more ecologic acid bath activated by air bubbles. Quite good results could be obtained, however the quality was very much dependent on the the quality of products: copper board (the insulation layer is aging), UV light tubes (aging too, requiring longer exposure times), acid bath (pH varies with temperature and engraving cycles), etc. In other words, this whole process was working fine with fresh products and for small series of PCBs but you could not expect reliable manufacturing for intermittent use.

An alternative consists in using a CNC machine to crave the PCBs resulting in typical engravings such as this example. I used to call this design style “à l’anglaise” but I could not find evidence of the correctness of this expression.

Thanks to advanced code and proper machining tools, most recent CNCs will produce very decent PCBs looking like “normal” ones such as the one produced next

Although this option looks interesting it suffers from few drawbacks which make the result of machined PCBs still look amateur. As the raw material is made of epoxy and copper, no plating will protect the pads, no coating will protect tracks and help soldering SMDs and no component labels or useful labeling shall be printed. In addition, track clearance may depend very much on the cutting tools and XY table resolution and tolerances.

The ultimate alternative is to subcontract the production of PCBs to one of the specialized companies. Most of them built their economical model on a highly automated process which enables the production of one to many boards in very short times. European companies benefit from quick delivery times while Asian companies offer low prices and decent delivery times. As a professional, I am frequent customer of BetaLayout, however, as a hobbyist I am looking for low cost suppliers offering reasonable delivery times and fares.

After a quick glance at the market lead me to PCBWay, a China Shenzhen-based PCB manufacturer which offers PCB making, board assembling operating under a streaming Quality Control (improperly advertised as Quality Assurance). PCBWay web site is clean and simple, using a lot of illustrations which come handy for setting the correct specifications and getting what you really want. This is very convenient for those who make an intermittent use of these services; early website were lacking such clarity and drove me to some disappointments and frustrations. Next is a screen capture of the parameter settings to be completed before getting the online quote.

The ordering process is fairly simple and lies on few stages:

Manufacturing tracking is available from PCBWay website while email are sent on each stage completion.

I have been used to receiving pictures of my own PCB while being manufactured which is very convenient for urgent orders: although these pictures may show frustrating flaws, it helps correcting them instantly and preparing a new order snappy. PCBWay may consider this option later on.

So far so good, I gave PCBWay a try and ordered the previously described PCB. The clock is now ticking and I am eager to share with you the results of this first run…

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