PCB through hole plating

[akis]

Is there a clever/cheap/easy way that I may have missed to plate through holes? I have seen a riveting machine for sale, but Christ, you'd have to plate each hole individually and you'd have to insert appropriate sized rivets manually - it sounds like it would take ages. The other solution is to solder on both sides of the board but sometimes this is impractical, eg underneath components with not much space to work.

[kripton2035]

well today it is soooo cheap to make boards in china with itead or seeed that for prototypes I don't bother anymore...
I only do single sided boards, or with very low via counts at home.

[sleemanj]

There's realistically only 4 options

1. go from one side to the other by way of through hole component legs soldered top and bottom
2. solder bits of wire in via holes
3. rivets
4. plating

Rivets work ok, I use (and sell in NZ) 0.8mm OD ones, I etch vias to have 0.4mm centers with a larger diameter ring this allows some wiggle-room for slight mis-alignment, drill with 0.8mm bit, insert rivets (press fit in the holes), flare the back side slightly with a drawing pin, and press flat using a rod chucked in my drill press, then a dab of solder both sides to ensure a lasting connection. 

Electroplating is of course the ideal, but just isn't easy to do at home.  There's a couple of youtube videos of people doing through hole plating at home, essentially find some conductive ink, suck it through the drilled board (not etched of course), dry, then electroplate copper, a lot harder than it sounds. 

[free_electron]

Is there a clever/cheap/easy way that I may have missed to plate through holes? I have seen a riveting machine for sale, but Christ, you'd have to plate each hole individually and you'd have to insert appropriate sized rivets manually - it sounds like it would take ages. The other solution is to solder on both sides of the board but sometimes this is impractical, eg underneath components with not much space to work.

Yes there is.
Drill holes, dip pcb in electroless copper solution, electroplate , clean, apply photoresist , tinflash , strip resist, etch.

Very simple. Millions of boards are made like that every day. Dirt cheap in china.
If they can do it, why not you ?

Back to reality: no there isn't a home solution. The whole process fails with the first step: the drilling. Even of you can overcome that because you have a cheapo cnc machine you face trouble with application of the dryfilm and exposure.

[akis]

OK thanks all for the replies, it seems I will have to solder the components from the appropriate sides and design the PCB so that there is no need to solder under difficult components.

[RossK]

I know you're not in the US but this site is what i use http://oshpark.com/. They are a batching house with virtually no minimum size (i think the minimum is something like 1/2 a square inch!) Once i went to real fabbed boards i'm never going back

[akis]

I used to send my Gerber files to someone who then "magically" produced a minimum of 4 copies of the PCB for me - in 4-5 weeks. However, during the initial phases nothing beats being able to have a PCB in your hand with all the corrections in less than 2 hours. And there are a lot of corrections And once the prototype has worked, well, that's it, no need for extra PCBs then.

[mamalala]

Back to reality: no there isn't a home solution. The whole process fails with the first step: the drilling. Even of you can overcome that because you have a cheapo cnc machine you face trouble with application of the dryfilm and exposure.

That's simply not true. I have done many through-plated PCB's myself. Yes, it takes some time, but it is quite doable. Heck, i even hand-drilled the holes. Sure, that is no longer an option if you want very small via's or very thin restrings, which would definitely require a CNC to do the drilling. But trouble with the dryfilm and exposure? Are you kidding?

Here is how i do it, if i want/need to, with manually drilled holes:

- Get a proper film (litho) for the layout and drill-markings done in a print shop
- Apply the drill-marking template onto a bare PCB
- Drill the holes, slightly larger than they have to be in the final product
(I have mounted a small B/W camera below my mini drill press. I overlay a crosshair onto the image, which in turn is displayed on a small B/W tv screen. That way there is no problem with alignment)
- Squeeze slightly dilluted carbon ink through the holes. I use a conductive carbon ink made for screen-printing
- Suck out the ink with a vacuum
- Clean the surfaces of the PCB
- Cure the ink in an oven, 10-15 minutes at the proper temp will do
- After curing, clean the surfaces a bit more with fine grit sandpaper
- Electroplate the PCB
- Apply dry film, expose, develop, then etch
- Strip dry film, and if wanted, apply solder mask dry film and expose/develop/cure it.

That's all there is to it. With a little practice one can do that at home. Are the results perfect? Depends on how skilled one is. They probably won't hold up to commercially produced boards, but still, the end result are plated through PCB's that work just fine. Attached are two images of the results i got. One is a PCB right after plating, the other is a final PCB after applying chemical tin.

Seriously, trouble with applying the dry film and exposure? That must be a joke.

Greetings,

Chris

[kripton2035]

congrats, beautiful home made board !
but what machines do you use ? electroplate the pcb ? with what ? thk.

[mamalala]

congrats, beautiful home made board !
but what machines do you use ? electroplate the pcb ? with what ? thk.

For drilling i use a simple, small drill-press from Proxxon. In the table i mounted a small B/W cam looking upwards (see pic). A simple circuit with a µC creates an adjustable crosshair-overlay (syee other pic). Electroplating is done in a simple copper-sulfate bath:

1700 ml H2O (DI water)
490 ml H2SO4 38% (battery acid)
280 grams CuSO4 (copper sulfate)
300 miligrams NaCl (salt)
1 ml Tween 20 (polysorbate, to reduce surface tension)

Copper electrodes are solid copper plates, 6mm thick. Carbon conductive ink is SD 2843 HAL from Lackwerke Peters. I thin it down with alcohol to get a consistency like warm honey. Dry film laminate (Tenting) can be bought online in sheets, for example in Germany from http://www.octamex.de/shop/?page=shop/browse&category_id=5848924494118370762daa6f026e22f7&/PCB_Laminate_/_Dry_Film_kaufen.html. I apply the laminate by heating the PCB on a "hot" plate (well, not that hot) and rub it on manually with a cotton cloth. Exposure is done with a simple UV exposure box, same as used for presensitized PCB material.

I use an ols oscillating fan, without the blades, to have tthe PCB move back and forth in the electroplating bath. Supply is a simple 12V toroid transformer to which i addeed extra taps every 1 volt (secondary is the outer winding, so that is simple to do), going to a big bridge rectifier. Electroplating copper is no black magic, after all. Yes, it requires a bit of effort to do, but it's not that hard. The only real nasty chemical stuff is the electroplating bath. The other two chemicals are the soda for developing, and the NaOH for stripping.

Sharp drill bits are important (i buy those sets of used tungsten carbide drill bits that you can get on eBay for cheap), and so is the litho/film used for the drill-marks and layout (they have to match perfectly, forget using a laser printer. Dunno about inkjet).

Greetings,

Chris

Edit: To clean the PCB after applying the ink, i use some old, thin cotton cloth dabbed in alcohol. I put that around a block of cork to get an even surface. The important point here is to not apply too much pressure, to make sure that there still is good contact between the ink on the hole-wall and the thin copper cladding (i start with 17µ copper cladding). After curing the ink in the oven, the additional cleaning with fine grit sand-paper is to remove oxidation from the copper surface, as well as to remove some left-over ink fillms that may sit there. Otherwise it would be embedde3d between the two copper layers (original and the electroplated) and subsequently hinder etching, since that ink is etchant resistant. (i use ferric chloride for etching, cheap and works well).

[akis]

Not in topic but I had the idea that I could sandwich two thin PCBs, one double sided and one single sided to end up with a 3 layered PCB. For example the double sided PCB would be the middle and bottom layer and the single sided PCB would be the component layer. Has anyone ever done this?

[Mike S]

Not in topic but I had the idea that I could sandwich two thin PCBs, one double sided and one single sided to end up with a 3 layered PCB. For example the double sided PCB would be the middle and bottom layer and the single sided PCB would be the component layer. Has anyone ever done this?

I've been wanting to try that too, but haven't yet had the need for a 3 layer board. How would you hold the two boards together? Some type of glue, or maybe put a short piece of wire through each corner and solder the top and bottom layer together?

[akis]

Not in topic but I had the idea that I could sandwich two thin PCBs, one double sided and one single sided to end up with a 3 layered PCB. For example the double sided PCB would be the middle and bottom layer and the single sided PCB would be the component layer. Has anyone ever done this?

I've been wanting to try that too, but haven't yet had the need for a 3 layer board. How would you hold the two boards together? Some type of glue, or maybe put a short piece of wire through each corner and solder the top and bottom layer together?

Surely that is the easiest thing to do: a couple of wire joints in the through holes will hold everything together better than any glue.

My only problem would be the correct alignment during manufacture. Currently even the "simple" dual sided board is hard to get right.

[akis]

Actually I just thought about this: it would not work for the home project. You would need to rivet all the through holes and in a way that it connects with the middle layer(s).

[SArepairman]

You could do two boards, I have been contemplating this using some kind of film between them, or some kind of coating ? Perhaps you can etch two double sided boards and then put a bake on coating on one of them with some holes that you put solder pads on, make matching solder pads on the other board and just leave them in a oven like a sandwich.

I'm thinking two etched boards then put a toner coating on one of them so they only short out in the places that you want when you melt them together.


Another way to do it is to use one board as a power board and connect it to your other board via header connectors, so you have a little board sandwich, and separate the boards using stand offs.

[akis]

I think I have just found a simpler solution.

The problem is that if we have a middle layer we will not be able to solder components to it. Fine. So what we do is we design it with a very simple rule:

Rule: components/vias which need connections on the middle layer must not have connections on the bottom layer.

Optional rule: components/vias which need connections to the bottom layer must not have connections in the middle layer (well they could but it will be harder to double solder and leave enough untrimmed leads to reach the bottom layer afterwards).

Then the process of building is very simple. Create a 3 layer design. Use a double sided board for the component and middle layer. Place components and solder as normal. Use a single sided board for the bottom layer. Connect and solder the remaining components which pass but do not connect to the middle layer by design. The various connections will keep the sandwich together.

[HooRide]

I recently found this on eBay to help repair some through hole plating that came out along with the leads of a few TO-3 transistors on a 25 year old amplifier. They work really well and were pretty reasonable priced.

http://www.ebay.com/itm/280751380393?var=580075154654&ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649