Talk:Printed circuit board

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Testing section, mentioning bed of nails tester and boundary scan testing, and maybe test coupons. panelization

Contents 1 Page split suggestion 2 Photo for use in this article 3 substrate 4 Design 5 Conductive Inks used on PCBs 6 Cordwood construction don't belong here any more 7 Technology Limits 8 New Section: Important things to consider when engineering a PCB 9 External links 10 EDA 11 Link farm 12 Multiwire boards 13 Featured article 14 Hey some help in writing a paper? 15 Etching- where is it? 16 Populated pcbs 17 Steel substrates 18 Merge tag 19 Too many external links 20 Introduction

[edit] Page split suggestion

Does anyone think we should break this page up into "Circuit boards", "Circuit Board Design", and "Circuit Board Manufacturing" pages? Of course link all three together, so a reader can navigate. These three topics seem like they could be entries on their own, and circuit board seems like it is getting long.

Your plan sounds fine to me. Perhaps we need another article on prototyping boards, such as stripboard (Veroboard), tagboards, perfboards, wire-wrap, Speedwire. -- Heron 19:18, 12 May 2004 (UTC)

OK, I added stuff about prototyping electronic circuits at Prototyping. --DavidCary 21:01, 28 Dec 2004 (UTC)

[edit] Photo for use in this article

Please see Talk:Microcontroller -- maybe the photo in question (shown) could be of use here instead? --Wernher 01:51, 24 Oct 2004 (UTC)

[edit] substrate

The article once said "The simplest PCB is a layer of copper foil glued to a sheet of plastic (referred to as the substrate), often an epoxy glue reinforced with fiberglass."

Yes, fiberglass-reinforced epoxy is the most common PWB. But is it technically plastic ? It's definitely a composite material.

--DavidCary 21:01, 28 Dec 2004 (UTC)

PCBs based on FR4 or other epoxy based materials are sometimes called "plastic" in contrast with circuits on ceramic substrates (what we used to know as "hybrid" circuits).

--borborygmus 18:32, 2005 Apr 25 (UTC)

Removed reference to "'Pertinax' (a phenol formaldehyde resin), or a fiberglass-reinforced epoxy composite material." This appears to be a bogus entry. Search for this brand name at http://www.thomasnet.com turned up nothing, and in 30 years of working with PCBs I've never heard of the stuff. You'll find this reference all over the Web, usually in conjunction with a discussion of Roman emperor Publius Helvius Pertinax, but it appears to have been gathered from Wikipedia by 'bots. -- Quicksilver 04:10, 11 Jun 2005 (UTC)

• No, Pertinax is indeed the term used for the resin type board, for instance in Finland. (May be a German trademark?) "Pertinax printed circuit board" gives 294 Google hits. --Janke | Talk 20:07, 25 August 2005 (UTC)

[edit] Design

The statement "Multilayer PCBs have alignment marks and holes " ist not correct, all PCB's need alignment for production. You can design very dens and very fine pitch on 1 and two sided PCB for eg. IC package. -- Cello 08:22, 24 Jun 2005 (MET)

Fixed. --Heron 08:45, 24 Jun 2005 (UTC)

The statement, "Also, a PCB etches more consistently and tends to resist warpage if all regions have the same average ratio of copper to bare board.", is not entirely true. The advent of spray etching equipment in circuit board job shops has resulted in consistent etching regardless of metal-to-nonmetal ratios. Quicksilver 00:32, 14 October 2005 (UTC)

[edit] Conductive Inks used on PCBs

I believe that conductive inks were in fact used on early PCBs. Hence the term Printed Circuit Board. I'm sure it used to say something about the man who did this in this very article. Will try to find refs before reinserting. Light current 21:15, 24 August 2005 (UTC)

• Yes please, refs are always nice. "Printed", IMHO, refers to the silk screen printing used to make the etch resistant mask. --Janke | Talk 20:03, 25 August 2005 (UTC)

I think you are right about 'printed' refering to a silk screen but I havent found any proof of it yet. There is no mention of how Eisler first did it in the article [1] on him. Light current 22:26, 25 August 2005 (UTC)

I'd be surprised to find that PCBs have ever used a much different process than either the good-old subtractive process (print the resist on the copper, etch away the rest) or the (semi-)additive process (which usually involves plating extra copper and then tin/lead into the unmasked areas, followed by a brief etch that removes the original copper from the unplated areas), but there was a brief flirtation with actual printed wiring for the purposes of accomplishing ECOs (Engineering Change Orders). The Wired Ink corporation were the big proponents of this ca 1978 or so, but I don't think they ever quite got all the bugs worked out of their technology; the company I worked for at the time investigated using this process but ultimately rejected it.

Atlant 23:53, 23 May 2006 (UTC)

Yeah but Im talking EARLY (very early-- before we were born!) pcbs! 8-)--Light current 00:04, 24 May 2006 (UTC)

Another pair of topics, though, where Wiki has no coverage (at least according to Google earlier today) are thick- and thin-film circuitry. There, the conductive patterns definitely are screened directly onto the (usually-ceramic) substrates.

Atlant 00:09, 24 May 2006 (UTC)

Yes thats correct. I think thats how the very first PCBs were made by Eisler but I cant find the refs! 8-(--Light current 00:13, 24 May 2006 (UTC)

Nowadays, Google reveals Conductive Circuits, Inc. using the printing-for-rework process.

Atlant 00:18, 24 May 2006 (UTC)

OK. If you were Eisler, what would you have used as a conductive ink. (must have been available in the fifties) 9-)--Light current 00:22, 24 May 2006 (UTC)

Photographs (on "paper") are also called "prints", even though they are manufacturered with some opto-chemical process (no "real printing" in the "Gutenberg sense").

A circuit board can be drawn with a paint which contains silver grains. This stuff is readily available in car supply shops (for repair of the heating traces in the car's rear window). Conductive "paint" is also used for the shielding of electronical devices - for exa,ple, CRTs (TV tubes). Such stuff may be based on graphite, but there also paints which apparently conduct better the graphite-based stuff - at a higher price, but still cheaper than anything with a significant amount of silver in it. Nowadays such stuff can be readily bought in electnics shops, typicaly in the form of spray cans. Such stuff may have been available in the 50s as well.

And finally, there are paints which are resistant against the etching chemicals. Nowadays, this stuff is typically sold in the form of pens, so a PCB designed can simply draw the traces with such a pen, put the board into the etching chemical (no development needed, as with litographic processes) and finally rub off the paint again (with some "sanding block", for example, to improve the quality of the soldering on the traces). Obviously, similar point can also be used in printing machines.

Which of these explanations denotes the cause for the naming of PCBs is obviously unknown by me. --Klaws 12:41, 5 March 2007 (UTC)

[edit] Cordwood construction don't belong here any more

It seems now that 'cordwood construction' does not fit into this article on PCBs as there is no 'printing' involved in it. Any suggestions on where it might be moved to? Light current 17:22, 30 August 2005 (UTC)

So there you go.. I was wrong again!!--Light current 18:11, 25 February 2006 (UTC)

We have an embryonic section in the Prototyping article called "Electronics prototyping". You could move it there. I think Electronics prototyping ought to be a separate article, eventually, so that we can include other non-printed and even non-soldered methods. --Heron 17:34, 30 August 2005 (UTC)

Yes but its not really a 'prototyping' technique(it was definitely used in missile telemetry and fuzes). Its more of an old fashioned contruction technique. Light current 17:37, 30 August 2005 (UTC)

Oh, I didn't realise that. In that case, you could look at Electronics under "See also" where a few construction methods are listed. Perhaps this list could be separated and expanded. --Heron 19:02, 30 August 2005 (UTC)

OK Ive added link in see also in Electronics but that page is going to need some work. Also cordwood page needs modifying as it presently only refers to building construction. Light current 22:01, 30 August 2005 (UTC)

Cordwood construction, as described, has nothing to do with printed circuit board technology, and never belonged in this article from the start. (There was a version of cordwood that sandwiched components between two PCBs, but I've only read about it, and have never, ever encountered an example, either in industry or prowling through electronics surplus stores.) The section needs to be deleted from this article. It could be set up as a separate Wikipedia historic footnote article. It should not be included in prototyping, as cordwood was too costly a construction method for that purpose. Early in my career I heard older engineers jokingly calling for prototyping with cordwood, but from the context it was clear that they were joking; nobody ever actually did it in the lab, for obvious reasons. The technique has been obsolete since the late 1960's, pushed aside by integrated circuits. Wherever the article ends up, it should be rewritten in the past tense. Quicksilver 09:06, 4 September 2005 (UTC)

What joins the components together? Is that a PCB (or two) I can see??

--Light current 18:08, 25 February 2006 (UTC)

Cordwood construction using PCBs was commonly used in the Control Data Corporation family of computers. One of these days, I'll get the time to shoot a picture of a CDC module that I still have.

One might also make the argument that a billion Japanese transistor radios used a sort of "half-cordwood" construction. Surely we've all seen 1960s radios that have all the resistors standing vertically with the upper axial lead folded-back to pass down the side of the resistor and re-join the PCB. The resistors even included insulation on the leads to support that packaging method.

Atlant 12:00, 11 May 2006 (UTC)

Yes I ve seen those Japanese radios- very tightly packed. 8-)--Light current 12:51, 11 May 2006 (UTC)

[edit] Technology Limits

Should there be something in here about number of layers vs thickness? Concepts of trading off laminate thickness vs characteristic impedance? What about buried capacitance, this technology does not seem to be mentioned... Likewise microvias (laser drilling) Should these be added?

[edit] New Section: Important things to consider when engineering a PCB

Just some ideas, feel free to work this anyway you want. (atleast a few of these caught my attention, being seemingly absent from the article)

• prototyping
• measurements
• lead spacing
• lead/hole diamaters
• multiple qualifying parts (eg, what if you run out of compenent D1, and need to order a compatible substitute?)
• voltage/current requirements

 * track thickness, width, spacing

• noise
• testing/troubleshooting
• supplementry/addon subcicuits
• FCC ID

Embarrasing as it was, I once adjusted the wrong layer (flip side) for a mating contact on the edge of a board. Stupid things like this cost big bucks if you're too rushed for QA.

66.219.200.235, when you leave comments on the Talk page, please remember to log into Wikipedia with your Username, sign your contributions with ~~~~, and preview your post for glaring formatting and spelling errors before clicking the Save page button. It would also be helpful to not label new sections "New Section", because in a short while it becomes an old section. -Quicksilver 18:51, 11 November 2005 (UTC)

[edit] External links

This article is in danger of becoming a link farm, contrary to Wikipedia policy. -Quicksilver^{T @} 21:58, 6 January 2006 (UTC)

There's a list of CAD packages near the bottom, but no mention of anything by Cadence, including the OrCAD package (which has been around for years) and Allegro. I think it should be added to the list of PCB layout programs but I don't want to add to the link farm problem, so I'm mentioning it here.

Allegro is added, but it points to the wrong place! --24.46.164.83 02:35, 3 March 2007 (UTC)

[edit] EDA

The EDA information is very good. In my organization we are generally working with high frequencies, so that we do all of our component placement and routing by hand; and I'm not real familiar with what's possible in automated placement. But, the description of placing all the components on a rectangular grid seems specific to certain types of design, like large scale 7400-series logic designs. In a design with irregularly sized parts, like a single 50 mm square FPGA surrounded by a mess of 0402 capacitors and a few power supply components, for example, placing the passives on the same grid as the FPGA doesn't seem sensible. Is there a way to describe the auto-placement and routing process that isn't specific to certain types of design? -- The Photon 06:30, 10 February 2006 (UTC)

[edit] Link farm

Gotta watch this page does not become a link farm!--Light current 22:04, 18 March 2006 (UTC)

[edit] Multiwire boards

This technique of interconnection with machine routed insulated wires embedded in a non conducting matrix was used during the 1970' to 1980s. Should this be mentioned here or on its own page? --Light current 01:59, 20 March 2006 (UTC)

It should at least be referenced here and, I'd argue, included here.

Atlant 23:58, 23 May 2006 (UTC)

Included it. But now the name of the page will need to be changed from PCB to Circuit board possibly. 8-|--Light current 17:22, 1 June 2006 (UTC)

[edit] Featured article

I feel this is now getting near to the quality of a featured article. Any comments for/against?--Light current 03:40, 21 March 2006 (UTC)

Never hurts to put it up for Peer review, at least. -- The Photon 05:50, 21 March 2006 (UTC)

[edit] Hey some help in writing a paper?

Hey, i was just wondering what kind of information would sound good in a report about the History of comps. So far i have used a lot of encyclapedias (actualy book) but it seemed to me like they all said the same exact thing. Could any one help plaese? Im running out of information on this main page!

sorry person above is Glitch481

[edit] Etching- where is it?

Have I missed it, or is there actually nothing on this page on the important subject of actually ETCHING the board? THis omission needs to be remedied quickly!--Light current 04:08, 30 May 2006 (UTC)

It was there, but now it's more obvious.

Atlant 13:47, 30 May 2006 (UTC)

Yeah Ok. But I think we need quite a bit more detail on the (chemical) etching process.

• different sorts of etchants (FeCl3, ammonium persulphide, copper sulfate, etc)
• track undercutting,
• definition,
• problems etc etc.

Could turn into a page all of its own after being nurtureed and fed here! --Light current 17:04, 30 May 2006 (UTC)

[edit] Populated pcbs

Moved here from page beacuse testing of populated pcbs is not really about pcbs, its about completed electronics assembly testing ATE etc

After the board is populated, the interconnection between the traces and the ICs may be tested by boundary scan techniques. In boundary scan testing, test circuits integrated into various ICs on the board form temporary connections between the pcb traces to test that the ICs are mounted correctly. Boundary scan testing requires all the ICs to be tested to use a standard test configuration procedure, and the most common one is the Joint Test Action Group (JTAG) standard.

--Light current 17:13, 30 May 2006 (UTC)

Yes, you are right. But by the same argument, the entire section on populating and conformal coating are not relevant to this article. Furthermore, the disambiguation page PCA has a link here. Also, very few people in common talk make a distinction between a PCB and a PCA. A general encyclopedia reader, seeing a PCA in their VCR or TV set and trying to find out how its made is more likely to look it up as a PCB than as a PCA. Rather than try to fork off a new article for Printed circuit assembly, I've added a bit of verbiage to the lead section to expand the scope of this article to include PCAs as well. I've also rearranged the test and populating sections to reflect the distinction between PCA and PCB -- the PCB test is done before populating. Finally I put the JTAG material back in, but into the section on populating, again to clarify the distinction between a PCA and a PCB. Seem reasonable? -- The Photon 04:57, 31 May 2006 (UTC)

Well wouldnt it be better to rename this article Printed circuit assembly or Circuit board which is a more common name, with redirect from Printed Circuit Board? 8-|--Light current 15:02, 31 May 2006 (UTC)

At the moment, Circuit board redirects here. Problem is, that's not really correct since wire-wrap and other types of circuit construction probably also would be considered circuit boards. -- The Photon 04:26, 1 June 2006 (UTC)

[edit] Steel substrates

On disassembling a defunct 3.25 FDD recently, I was surprised to find that the PCB substrate appeared to be steel. I dont know the reason for this and its the only one Ive ever seen. Anyone have any more info on steel substrates and their advantages? 8-?--Light current 16:39, 31 May 2006 (UTC)

Some metallic substrate exist (Power electronic substrate), but as far as I know, they are mainly made of aluminium, and sometimes copper. I can't remember having seen any of those made of steel. Maybe it is for EMI shielding purposes? - CyrilB 17:05, 31 May 2006 (UTC)

Yeah but this was definitely steel- I tested it with a magnet. Only reason I can see for them using it is that its cheaper than copper or aluminium 8-?--Light current 17:37, 31 May 2006 (UTC)

In the case of a HDD, it might be used to protect the disc from magnetic fields. Is the substrate part of the motor? This kind of setup is sometimes used in VCRs. - CyrilB 19:11, 31 May 2006 (UTC)

Could it have been structural? In small disk drives, there's a very definite contention between the total available thickness and the thickness consumed by the platter stack-up; making the PCB a stressed member might mean that there's no need for some separate structural member so they can fit a millimeter or two worth of platters in there. Remember, disk drive frames have to be quite rigid to absorb the forces of the head-positioning mechansisms yet keep the heads on track.

Atlant 00:48, 1 June 2006 (UTC)

Well I think it may have been structural altho' it did not seem to be part of the platter assy. But I cant tell now as I think I have thrown it away as being useless (silly me). Ive got so much junk you wouldn't believe it (OK maybe you would) 8-)--Light current 00:56, 1 June 2006 (UTC)

I'd believe it! ;-)

Atlant 01:01, 1 June 2006 (UTC)

Yeah. Anything that goes wrong I take apart and, if I cant fix it (which is usually the case), I completely dismantle it and say to myself of a component or assy (or bit of metal even): that looks interesting -- I may be able to use that in the future. So I keep it - sometimes for years (and years). Does this sound familiar to anyone? --Light current 01:13, 1 June 2006 (UTC)

[edit] Merge tag

The merge should not be carried out for the article PCB layout guidelines should be transwikied to Wikibooks since it is a how-to like manual. Lincher 02:20, 17 September 2006 (UTC)

[edit] Too many external links

The number of external links on this page is far more than even a liberal reading of Wikipedia:External links would suggest is healthy. Right now, it seems to be serving as a links directory for software, design documents, magazines, and more. There are 35 (!) links in the section right now. Ideally, it would be no more than five, though I can't see pruning this list to so few, realistically. Particularly, the software and magazines should go—the software because it's already internally linked (them that are notable enough to have articles) above in the see also section, and the magazines because we're not a links directory (if any have article, a see also link would be apropriate). If there are no major objections after a while, I'm going to clean the external links section out. — Saxifrage ✎ 04:42, 4 October 2006 (UTC)

[edit] Introduction

Could the inroduction please put pcb's in better context with a sentance such as "PCB's form the basis of most electronic devices from TV remotes to personal computers". The introuction is too technical and offers no clue as to how widespread pcb's are. —The preceding unsigned comment was added by 68.226.90.205 (talk) 03:14, 6 April 2007 (UTC).