What PCB fabrication methods for *prototypes* are used by professional engineering departments today?

Question

Ten years ago, I worked at a small engineering department within Philips Semiconductors that prototyped all designs before getting them professionally fabricated outside. The method was pretty standard:

• Print artwork using a cheap laser printer onto semi-transparent film
• Tape down top artwork onto bottom artwork and visually align them.
• Cut a PCB to approx size, drill a hole at edge where a wire can be inserted to hold the PCB between insertions in chemicals.
• Insert PCB between artworks, and expose using a homemade UV light box.
• Hook wire into hole on PCB and dunk in a vertical tank containing Sodium Hydroxide and wait until developed
• Put in spray tank and spray with clean water.
• put in vertical tank containing Ferric Chloride etch and leave until etched.
• put in spray tank and spray with clean water
• put in etch remover until etch removed
• Put in vertical tin tank for tinning.

The results were beautiful looking PCBs that were very easy to solder and professional looking, despite a lack of solder mask and screen.

Is this the standard method still used by professional engineering departments when making prototype PCBs today, or are there other methods that give similar great results?

Answer 1

None that I know of. 15+ years ago I also worked for a small engineering firm that did what you described above. Today, in my basement, I can layout PC boards with free or low cost software, generate a Gerber file, email those files to a circuit board house and have boards made for less than $3/sq in with better quality that I can dream of doing. Mask and silkscreen are typically included for the same price. Turnaround is between 5-15 working days depending on how much you want to pay.

It's no longer reasonable to make PC boards yourself unless you need turnaround time measured in minutes. It's so cheap that if you place a reasonable value on your time, you lose money doing it onsite.

Answer 2

About 15 years ago I hired an EE straight out of U.C. Santa Barbra. His first week on the job he asked me, "How do you prototype PCB's? Wire wrap, breadboards, or what?" My answer then is just as valid now. We design a normal PCB, have it professionally made, and if they work we ship the product. If it doesn't work, we fix it, build new ones, and try again.

There are PCB shops and contract manufacturers that specialize in making prototype quantities of bare PCB's.

The vast majority of companies make their prototypes in the same way. There are exceptions, of course. Some companies etch their own PCB's. Some use something like a milling machine for PCB's. Some will do wire wrap. And some will use breadboards or perf. board. But for anything but the simplest of boards probably 95+% of companies just get prototype PCB's made from a professional PCB fab shop.

While this method seems to cost more, in the end it is cheaper. We spend less time debugging, building, and futzing around with potentially low-quality and unreliable prototypes. Plus, we are able to use 4+ layer PCB's with plated holes-- which is HUGE. In the past 15 years I've designed maybe FOUR 2-layer boards and 40+ more complex boards.

Answer 3

I feel like someone should mention PCB milling as a prototyping method. Quicker and less messy than a chemical process, and the same machine that does the milling can also drill holes and rout the the board edges.

Two-sided boards are accomplished by drilling a few registration holes in the board that drop on to pins on the milling machine. Mill one side, flip, mill other side.

Still probably not very common in professional environments since prototype runs are so cheap, but for times when faster turnaround than a prototype run can provide is needed, milling is pretty great.

Answer 4

Time has definitely moved on from those days and I endorse what the other answers say/imply about the cost of getting proper multilayer PCBs made externally but I'll add something else.

In my experience the use of circuit simulation tools means that you can reduce the number of PCB iterations to get a design correct. Add this to the almost insignificant cost of multilayer boards and there is no real need for in-house prototyping any more.

Answer 5

I work at a small laboratory at colege. Here you have to make a gerber file (usually using Altium), and then send to the person responsible for prototyping (me), who will use a LPKF S42 to make the board. Sadly it looks pretty homemade.

I attached this picture from one of our prototypes. The left one (multilevel green) is made in some Board House; the right one (kind of brown) I made by myself.

Answer 6

So this is what we follow in our Lab. Only for a two layer board. More than two layer boards end up going to the vendor.

1. Take a print out of the board image (original size) and make sure only the bottom, drills, pads, via and dimension layers are on the image. We use Eagle for this. Use photographic pages of GSM less than 140.

2. Tear the page suitably to place over a PCB of certain size and iron (yes using an Electric Iron) the board keeping the printed side on the copper. Do this for atleast 15 minutes till you are sure that the tracks would have transferred onto the board.

3. Put the board in water and remove the excess paper and etch the board using Ferric Chloride as you mentioned. Once etched see the original design and using a compass make holes on all places where drills need to be done. Use appropriate bits for drilling (depending on the size of the component you wish to fit). Also, drill all the vias and add jumpers on the top layer (if applicable).

So, This is the final result. :)

Edit: A few parts, which i thought were self explanatory, added now.

Answer 7

I'm not sure how professional we'd count as being, as we're a small design house rather than a huge multinational electronics corp...

Generally, very basic prototypes are done with a scalpel & copper-clad board if needed, or if more complex, we just send it out to Seeedstudio / Iteadstudio for $20, it's a no-brainer. If we need something done quick, we pay a more local "proper" PCB house to do a one-off or very short run. It costs, but that's business.

Answer 8

Typically, we send our stuff out to be printed for us, even for prototypes. Sometimes this can get expensive - 10 revisions of our work and there's over $10k. But for an initial investment of $7k, you can buy a CNC mill that will cut out dual layer PCBs very nicely. This isn't bad for prototyping, but not the best answer for mass production. We tend to steer away from chemical etch because it has a tendency to etch unevenly, and when your PCB has over a pound of copper on a small board (power supplies) you can create hotspots. For LV projects, chemical etch isn't too bad.

Answer 9

I use the cold method of DIY PCB creation. I have a cheap Brother laser printer than can do 1200x, I use this mode for most 48pin and 62pin MCU boards. If I don't need the resolution, I use the standard 600x and double the toner print.
I don't get fancy as far as via's go, I drill a 1mm hole where ever I need one, slide a wire just a little smaller and solder both sides(I'll also use old solder wick to tie top and bottom layers together if I poured a top ground). The paper I use is Fedex-Kinko's light glossy paper, works like a charm.

Pre-step, cut board to correct size using a high speed rotary tool.

1. Clean board using very fine grit sandpaper. Then wipe down with the same mix I'll use apply the toner mask. 5 parts 80% alcohol to 3 acetone, with no added water due to the alcohol not being 99%.
   2.Cut the reversed toner mask to correct size. Apply a decent bubble of the above mixture to the board, apply mask, aligning at least one edge on both board and mask.
   Use a simple rubber roller to get most of the air out from between board and mask.
   Then put the board down on an old piece of prototype board paper up, add another old board and apply one or more clamps depending on size. After about 10 min, remove clamps and board, and let air dry.
   2a Now I'll put the board into a shallow dish with some water and give it at least an hour to loosen up and then remove the paper. Wipe down the board with water. Ensure clean.
   ++ Next I'll take my hot air wand to it, making sure to soften the toner everywhere. You should only heat it enough to cause the toner to become slightly softened and fill any holes left by the transfer. Since I started doing this, after etching and removal of the toner, you can easily see any pattern left over from the initial sanding.
   -+- If I have signal traces on the bottom, I'll cover up the top mask using painters tape(That's the blue tape that really does not stick to much). This is just to keep any of the mix from being able to reach the front.
   I'll now repeat steps 2 and 2a and remove any blue tape.
   ++ Next I'll take it outside and etch using a combo of Hydrogen Perioxide and Muratic Acid(aka weak Hydrochloric). Etch until it looks good and flush with water. I'll pour all of the etchent (Unless I'm planning on making more in the next hour) into an old apple cider bottle. That goes back on a shelf in the shed; I live in Arizona and in less than a week all the water is gone.
2. Remove all toner using 100% acetone and napkins. Wipe down with mix.
3. Drill required through holes, vias, etc. If it's small I'll just hand assemble using a tooth pick to lay down some refurbed paste(I add a little flux to it and mix), spot the part and use my hot air wand to reflow. If it's big, I use some of my good paste and a mask to lay it down. Carefully using tweezers, bright light and a head mag, I'll put all the parts on, put it carefully in the toaster oven, attach temp probe and reflow that way.

I've used this method to make all kind of boards including RF boards up to 2.5G. Hope I did not forget anything...

Answer 10

We scarcely need yet another go-around of this question, but since it is here, for completeness the clothes iron & junk mail paper laser toner transfer method is a useful and faster alternative to the photo etch method for those same-day one-off experiments.