climber@uvicctr.UVic.CA.UUCP (climber) (05/29/90)
I am designing double sided boards that I am planning to etch myself. Now, I want to start using pin arrays and realized that I will now need plated thru holes (where the copper lines the hole itself making a nice connection between top and bottom traces). Is there a way I, a hobbyist with measly resources, can build a two-sided board with plated thru holes? I would like to avoid the following: tremendous equipment expense having to spend more than $10 per prototype board (outside the costs of blank PC board) Has anyone tried this? How does the big-wigs in the industry do it? Send any responses to: climber@sol.UVic.ca Any help would be greatly appreciated. Craig
thouse@uvicctr.UVic.CA.UUCP (thouse) (05/29/90)
> I am designing double sided boards that I am planning to etch myself. > Now, I want to start using pin arrays and realized that I will now need > plated thru holes (where the copper lines the hole itself making a nice > connection between top and bottom traces). Is there a way I, The plated through hole process is very complicated and time consuming.We used to have a machine to make the boards here but gave up because of the number of steps required.
irwin@m.cs.uiuc.edu (05/30/90)
/* Written 2:57 pm May 28, 1990 by climber@uvicctr.UVic.CA.UUCP in m.cs.uiuc.edu:sci.electronics */ /* ---------- "plated thru holes" ---------- */ >I am designing double sided boards that I am planning to etch myself. >Now, I want to start using pin arrays and realized that I will now need >plated thru holes (where the copper lines the hole itself making a nice >connection between top and bottom traces). Is there a way I, >a hobbyist with measly resources, can build a two-sided board >with plated thru holes? I would like to avoid the following: > tremendous equipment expense > having to spend more than $10 per prototype board (outside the costs > of blank PC board) >Has anyone tried this? How does the big-wigs in the industry do it? >Send any responses to: climber@sol.UVic.ca >Any help would be greatly appreciated. >Craig /* End of text from m.cs.uiuc.edu:sci.electronics */ Though I responded to Craig with e-mail, I thought I might put some of what I sent to him here, as it may be of interest to others. I am with the Department of Computer Science, at the University of Illinois. Years ago, about 15 or so, we used to have a complete printed circuit board lab, complete with cameras, PCB layout group, etch facilities, plating equipement and a wave soldering machine. The process which we used for plated through holes may have changed since then, and again, it may still be done in much the same manner. I will describe the process for the hungry minds on the net. We started by first drilling the boards (double sided), with what I believe was called a Panograph. It was simular to the machines used to make name plates and badges, or engraving. There was a master template which one followed with the cursor, and the electric drill followed your every move in the X/Y direction. We used a brass plate to make the template, making a center punch in the template for each hole to be drilled in the boards. The cursor had a sharp pin that dropped into the center punch hole, which positioned the drill over the correct spot in the boards and they were stacked and drilled 4 or 5 at a time. The drill was air operated, so as one placed the cursor into position, they pushed the air button and the holes were drilled. After the holes were drilled, the board was placed into a copper bath, and electrodes (2) were connected from a power supply to the opposite sides of the board, such that when the board was placed into the bath, a current flowed from one side of the board to the other, through the bath. This plated the copper through the hole. After the copper plate, the board was photo sensitized, dried and exposed to the image via a negative, or I should say, a positive. The image was developed, leaving the photo resist on the board where you did NOT want to have any copper remain. This stripped the resist from the area that would become the trace or conductors on the board. It was then again placed in a bath and plated, this time with tin. The tin was to act as the etch resist in the final process, so, the trace and plated through holes were tin plated. The image was then stripped, which removed the photo resist, and the board was then etched, the tin being the resist. There was also a seperate process for plating the contacts, if it was to be a "plug-in type board". The contacts had to be I think first nickel plated, then gold, over the original copper. This was done prior to the tin plating. After it was etched, it was trimmed to size, parts loaded and then passed over the wave solder machine. In summary, for one to do this on a small scale, one would need the chemicals to make up the copper and tin bath, the power supply for plating, the photo resist to apply to the board, an oven to dry it, and so on. It takes quite a bit of equipement. We also emersed the board in dye, which dyed the image of the resist on the board black in color, and one could check the quality of the image. If flaws were found, they could be patched up with nail polish (of all things) or, the board could be stripped of the resist and done again. The board had to be scrubbed with a fine powder like used at the kitchen sink to clean copper bottom pans, before any of the above process was started, to remove the oxide, or one would not obtain good results. All in all, it was not an easy process. I do not know if the technology has changed much, but I would suspect that the steps taken today are much the same. I do think that there is a silkscreen process, that provides the component identification on the board, plus acting as a resist to the tin plating, though we did not do this with our boards. Al Irwin Univ of IL Dept of CS Urbana, IL irwin@m.cs.uiuc.edu
thouse@uvicctr.UVic.CA.UUCP (thouse) (05/30/90)
> I am designing double sided boards that I am planning to etch myself. > Now, I want to start using pin arrays and realized that I will now need > plated thru holes (where the copper lines the hole itself making a nice > connection between top and bottom traces). Is there a way I, > a hobbyist with measly resources, can build a two-sided board > with plated thru holes? I would like to avoid the following: > > tremendous equipment expense > having to spend more than $10 per prototype board (outside the costs > of blank PC board) > > Part of my last message was missing so here is my answer again. The process of making boards with plated through holes is very time consuming and requires a lot of different chemicals. We used to have a system here but got got rid of it for this reason. I doubt very much whether you would ever make a board for the price you are quoting.
henry@utzoo.uucp (Henry Spencer) (05/30/90)
In article <1109@uvicctr.UVic.CA.UUCP> climber@uvicctr.UVic.CA.UUCP (climber) writes: >... Is there a way I, >a hobbyist with measly resources, can build a two-sided board >with plated thru holes? ... As far as I know, the basic answer is "no". The plating process used to lay down copper within the holes needs precise control of temperature and solution chemistry if you want dependable results. After masking off the no-copper-here areas, the surface of the board is exposed to a catalyst, a very thin layer of copper is laid down by a chemical process, and then electroplating is used to build it up to a useful thickness. Even the electroplating is a slightly fussy job if you want a smooth, even, solid, well-bonded layer of copper, and the less said about the chemical process, the better. It's not a million-dollar investment to make it work, but you can't do it on a shoestring either. If all you want is a demonstration technique that sometimes works and sometimes doesn't, no problem, but if you're after trustworthy boards, that's different. -- As a user I'll take speed over| Henry Spencer at U of Toronto Zoology features any day. -A.Tanenbaum| uunet!attcan!utzoo!henry henry@zoo.toronto.edu
herman@marlin.NOSC.MIL (John W. Herman) (05/31/90)
-- I vaguely recall seeing an ad for a machine that puts sleeves in PC board holes the claim being that the sleeves could be put in for much less than plating through holes. I only remember seeing the ad and not much else. -- John Herman ARPA: herman@marlin.nosc.mil Phome: (619)553-1466 Naval Ocean System Center Code 712 271 Catalina Blvd San Diego, Ca. 92512-5000
a143@mindlink.UUCP (Ed Meyer) (05/31/90)
Replying to a message by Greg Ebert (Grass Valley Group), I thought I'd mention something which happened to me. While diagnosing a computer board fault (ruggedized board for environmental data acquisition) I came to the conclusion that one or more plated through holes in one section must not have been plated through. Well, careful conductivity checking verified my suspicions. But then came the surprise -- I'd heard about this kind of thing before but never experienced it myself until that time -- the holes were falling out! One inner wall cylinder was just in its hole and several of the other tiny cylinders were at the bottom of the case, no kidding. So, even though the board shop was making plated through holes, {_a quality problem existed which didn't show up till much later.
wbrown@beva.bev.lbl.gov (Bill Brown) (05/31/90)
In article <1422@marlin.NOSC.MIL> herman@marlin.nosc.mil.UUCP (John W. Herman) writes: > >-- >I vaguely recall seeing an ad for a machine that puts sleeves in >PC board holes the claim being that the sleeves could be put in >for much less than plating through holes. I only remember seeing >the ad and not much else. >-- ---And round and round it goes.... 'Way back in the Jurassic age, BPTH, (Before Plated Through Holes) eyelets, AKA rivets were used for making connections between the two sides of a double-sided board. They were sort of squashed or swedged into place, which was supposed to make a permanent connection. Of course they usually became intermittent over time, perhaps due to working caused by thermal expansion. The next step was to solder the rivets to the artwork. Eventually, this also failed intermittently, probably for the same reason. Usually, we ended up running wire through the rivets which was then soldered to the artwork. Seems like we ued #24 soft copper, as best I can recall. You've never lived until you've tried to trouble shoot a fair sized system (in those days a few thousand gates built out of discrete components, six 2-input nands per board) full of rivets which sometimes conducted and sometimes didn't. Rivets. Bah! Humbug!! Might as well use wire in the first place. Be sure to make gentle bends in the wire on either side of the board, and leave a tad-bit of slack for expansion/contraction. -bill wlbrown@lbl.gov Disclaimer: These opinions are my own and have nothing to do with the official policy or management of L.B.L, who probably couldn't care less about employees who play with trains.
grege@gold.GVG.TEK.COM (Greg Ebert) (05/31/90)
In article <1422@marlin.NOSC.MIL> herman@marlin.nosc.mil.UUCP (John W. Herman) writes: > >-- >I vaguely recall seeing an ad for a machine that puts sleeves in >PC board holes the claim being that the sleeves could be put in >for much less than plating through holes. I only remember seeing >the ad and not much else. >-- I saw such a machine demonstrated at NEPCON in 1984(?). You clamp-in a pre drilled board, pour a few thousand sleeves in the tank, and then the board vibrates. I was astonished to see that, yes indeed, the holes were filled. I don't know how reliable the process was. Many moons ago I was a tech, and I distinctly remember a particular CPU board nobody else could fix because every time you touched it with a scope probe, it died. Guess what! It was a hole that wasn't plated through.
raoul@eplunix.UUCP (Nico Garcia) (06/01/90)
In article <1109@uvicctr.UVic.CA.UUCP>, climber@uvicctr.UVic.CA.UUCP (climber) writes: > connection between top and bottom traces). Is there a way I, > a hobbyist with measly resources, can build a two-sided board > with plated thru holes? I would like to avoid the following: Ummm, after a little bit of experience and lots of reading and asking questions, my answer is "no". The best you can do with hobbyist level equipment is to drill a hole, put pads around it on both sides, solder a piece of wire through it on both sides, and run traces from that. It takes up a bit more room, but not much if you're careful. Remember also, things like resistor leads and IC pins can be soldered on *both* sides of the board: it makes them tougher to replace, but they can carry your signal for you. And if you have to replace it, plated through holes are a pain to desolder anyway. -- Nico Garcia Designs by Geniuses for use by Idiots eplunix!cirl!raoul@eddie.mit.edu
otmar@hpcvia.CV.HP.COM (Otmar_Borchard) (06/01/90)
> I am designing double sided boards that I am planning to etch myself. > Now, I want to start using pin arrays and realized that I will now need > plated thru holes (where the copper lines the hole itself making a nice > connection between top and bottom traces). Is there a way I, > a hobbyist with measly resources, can build a two-sided board > with plated thru holes? I would like to avoid the following: > > tremendous equipment expense > having to spend more than $10 per prototype board (outside the costs > of blank PC board) > > Craig --------- I worked in an electronics repair shop for the USMC a few years ago. We did a lot of work on double sided boards and used a lot of products from a company called PACE, Inc. They specialize in printed circuit rework and repair. They have something called a CIR-KIT that has parts to repair runs and plated through holes. If your boards will have a small number of plated through holes you could use some of the eyelets they sell. To install an eyelet, you drill a hole through the run and the board, place the eyelet through the hole, flare the ends of the eyelet, then tap them flat with a hammer and punch. After you solder them to the runs they make a reliable plated through hole. Pace makes a variety of sizes to fit different thickness of boards and different diameter component leads. I'll stick their address on here in case you want to contact them. Good luck! --- Otmar Borchard Hewlett-Packard Corvallis, Oregon Pace Inc. Pace US-West 9893 Brewers Court <or> 14451 Chambers Road, Suite 100 Laurel Maryland 20707 Tustin, California 92680-6913 (301)490-9860 (714)838-8100