EEVblog #939 - How Is A PCB Manufactured - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: November 03, 2016, 04:41:46 am
content: How is a double sided plated through hole solder masked and silk screened component olverlay PCB manufactured?Take a ste-by-step tour of a PCB manufactuing plant.http://www.pcbzone.netDesing for manufacture tutorial:DFM Automated PCB Panel Testing:Alba PCB Group Video:Eurocircuits Video:

author: ludzinc
author_rank: Unknown
timestamp: November 03, 2016, 06:27:24 am
content: If you're ever in Canberra you should visit Lintek.http://www.lintek.com.au/products-and-capabilities/#processThey clad their substrates using vacuum deposition so can deal with exotic materials.Nice guys too!

author: trophosphere
author_rank: Frequent Contributor
timestamp: November 03, 2016, 06:55:13 am
content: Another awesome video Dave. I have actually never looked deeply into how PCBs get made (just knew the general process) even though I got my undergraduate degree in EE back in 2009. Now I am on a PCB manufacturing video binge on Youtube.

author: julian1
author_rank: Frequent Contributor
timestamp: November 03, 2016, 07:09:22 am
content: Interesting video. Especially the negative photo-resist process, where they tin the copper in the areas of no resist. And then remove the resist, and etch the copper.Does tin resist ferric chloride, or any of the other common etchants?

author: Brumby
author_rank: Unknown
timestamp: November 03, 2016, 07:16:11 am
content: Quote from: julian1 on November 03, 2016, 07:09:22 amI thought about that for a moment - and the reasoning is quite simple.The negative resist process allows for the retention of the plated through holes. Otherwise, a positive resist process would need to find its way into the holes or they would get etched away.

author: julian1
author_rank: Frequent Contributor
timestamp: November 03, 2016, 07:32:41 am
content: Tin may also be superior in resisting the harsh etching conditions, compared with the thin layer of UV cured polymer. Meaning less undercut, and/or stronger etchant/faster process.

author: EEVblog
author_rank: Unknown
timestamp: November 03, 2016, 07:40:30 am
content: Quote from: ludzinc on November 03, 2016, 06:27:24 amYep, used them back in the military days for exotic boards. That's all they do now, there is no general mass production PCB manufacturer left in this country.

author: Moshly
author_rank: Regular Contributor
timestamp: November 03, 2016, 07:44:13 am
content: Here is a video on how tek did it in 1969 ->I like the way they use gold as the enchant resist.

author: sleemanj
author_rank: Super Contributor
timestamp: November 03, 2016, 07:55:29 am
content: Quote from: julian1 on November 03, 2016, 07:32:41 amI expect economics plays a role.By using the film resist to mask the bits you don't want, you can then plate on the copper to thicken out the bits you want to keep, plate tin on top of those bits to mask it, strip the film which is non-recoverable, etch away the copper you didn't want, which is recoverable, and then strip the tin, which is also no doubt recoverable, so the non-recoverable materials in the etch process is limited to one application of film.Doing it the other way (using the film to mask the bits you don't want) would mean that you'd either have to apply and strip film twice (once to copper plate to thickness, and then again to etch away the bits you don't want), or start with PCB which is totally copper clad to finished thickness increasing the time to etch significantly, and I expect while the copper etched is recoverable there would be losses so if you are etching more copper, there'd be more losses.Applying film twice would also mean you increase the chance of registration errors between applications of film, where as because you are tinning through a single film application you don't have that problem. And you'd be doing the second film application over a non-flat surface which would be fault prone I expect.

author: timb
author_rank: Super Contributor
timestamp: November 03, 2016, 10:38:30 am
content: Quote from: Moshly on November 03, 2016, 07:44:13 amThat was great! Good ole' Tek, doing it all in house.I swear, that narrator sounds *a lot* like Dr. McCoy from Star Trek...

author: free_electron
author_rank: Super Contributor
timestamp: November 03, 2016, 01:49:46 pm
content: the double plating step is simple : save copper AND create a more uniform copperreason 1 : anything you plate on you need to etch off.They plate a thin layer of copper first on the entire board.then apply resist in negative.then grow copper again . the copper only grows on the exposed area's ( which are what you want to keep anyway ... )tinplate, strip resist . etch.reason 2 : uniformity. the layer thickness in the holes is much more controllable if the entire board is pure copper. imagine this: a thin small sliver of a trace with a tiny 0.1mm via. 1 cm away from it is a big fat trace with a 2cm hole. if you try to plate that the big hole will grow copper faster than the tiny one. simply because the current in the hole is given by the contact surface area ...the current is pulled out of the copper plate by the plating electrode , but the current goes in through the plating liquid. so that tiny trace gets less current than the thick one.. as the current determines the plating speed ... by not having photo resist all holes benefit of the entire contact surface to the liquid. so they all grow uniformly.once there is copper in the hole it doesn't matter anymore. this effect only happens to get the copper initially in the hole.

author: zapta
author_rank: Super Contributor
timestamp: November 03, 2016, 03:02:11 pm
content: Dave, why do you need non plated holes? Can't you just isolate them on one or more layer?

author: Len
author_rank: Frequent Contributor
timestamp: November 03, 2016, 03:28:40 pm
content: Quote... while a silkscreening process is being shown.

author: G7PSK
author_rank: Super Contributor
timestamp: November 03, 2016, 05:03:46 pm
content: When plating through hole what makes the copper stick to the bare pcb edge of the drilled hole, is it pre treated in some way. If you want plastic plated you have to have a vapour or chemical surface applied first.

author: timb
author_rank: Super Contributor
timestamp: November 03, 2016, 07:18:55 pm
content: Quote from: G7PSK on November 03, 2016, 05:03:46 pmOld Style Method: Basically, they immerse it in a bath that contains a copper solution. It creates a very light plating inside the holes, which is then thickened during the electroplating step.They show this in the Tektronix video above, if you want to see it in action.Not sure if it's any different with a modern process.

author: ion
author_rank: Regular Contributor
timestamp: November 03, 2016, 07:22:07 pm
content: Quote from: G7PSK on November 03, 2016, 05:03:46 pmThat's what I was thinking - I guess there's no footage of that step.A few years ago I came across a chemical kit form MG Chemicals specifically to make bare PCB material conductive so it can be plated. Seems to be discontinued now and I'm not surprised - it was an expensive, multiple step process and you'd be left with several containers of toxic waste once the chemical baths reached the end of their (very short) shelf life. I'd imagine most poeple wouldn't go through all that for a prototype or DIY project.

author: rrinker
author_rank: Super Contributor
timestamp: November 04, 2016, 12:16:27 am
content: Now that I've had a chance to watch Dave's video as well as the Tek one - it's kind of amazing how much HASN'T changed. Still a significant amount of manual operation.And that NC drill in the Tek video - now that is an old bit. GE C100 maybe, even older than the GE 550 we had at my first job - like the 550, the one in the Tek video does no storage of the program, it simply runs step by step reading the paper tape. After one run, the tape is rewound for the next set of boards. You can control stuff like feed rates, but you can't edit the program on the machine. The 550 dates from the mid 60's and lasted until GE released their first true CNC control in the 1050 in 1974 (we had one of those, too). The one in Tek's plant is much older, early 60's or maybe even late 50's vintage. But in our shop, that 550 was just as reliable as newer fancier controls and put in a full day's work every day, so no reason to replace it.Kind of funny watching the worker silkscreen on the photosensitive solder mask and labelling materials while Dave is saying "in the past this was a silkscreen process but now it's photosensitive" Yes, not really silkscreening when you have no pattern in the screen, but still funny.

author: WattSekunde
author_rank: Regular Contributor
timestamp: November 04, 2016, 08:56:01 am
content: I remember inspecting a pcb production because of a quality problem with the via hole positions in some boards. And yes we used teardrop vias. We looked through the whole process and found the problem at the drilling stage. It was caused by drilling too much boards at once in a stack. The drill bend sometimes sidewards on the lowest boards in the stack. The manufacturer had to reduce to 4 boards in a stack to fulfill our quality needs.

author: vzoole
author_rank: Regular Contributor
timestamp: November 04, 2016, 09:16:24 am
content: Quote from: G7PSK on November 03, 2016, 05:03:46 pmThe answer is here:Black HoleThis machine fill the whole board and holes with graphite then remove it from the surface, so the holes still conductive too.https://youtu.be/T7S40GYESbY?t=3m57s

author: ludzinc
author_rank: Unknown
timestamp: November 04, 2016, 09:47:33 am
content: Quote from: EEVblog on November 03, 2016, 07:40:30 amThey still do boring 2 and 4 layer FR4 stuff. But they now have a cool laser drill too!

author: ali_asadzadeh
author_rank: Super Contributor
timestamp: November 04, 2016, 11:25:27 am
content: Maybe they could use TI DLP for direct exposing to the PCB, or maybe they could use a 4K LCD panel for direct exposing. they are just plain awesome Ideas.

author: timb
author_rank: Super Contributor
timestamp: November 04, 2016, 11:41:41 am
content: Quote from: rrinker on November 04, 2016, 12:16:27 amYeah, I was wondering about the drill in the Tek video. So, it's purely a mechanical solution then? No electronics? (Aside from the motors, naturally.)I assume it works a bit like those old player pianos? I always wondered how they automated this sort of thing before CNC came about. The aforementioned pianos have been around since at least the mid to late 1800's, so I figured it would be something like that.

author: vzoole
author_rank: Regular Contributor
timestamp: November 04, 2016, 12:50:09 pm
content: Quote from: ali_asadzadeh on November 04, 2016, 11:25:27 amThis direct imaging technology is already exist (at 5:03):https://www.youtube.com/watch?v=T7S40GYESbY&feature=youtu.be&t=5m3s

author: peterjohnston
author_rank: Newbie
timestamp: November 04, 2016, 01:37:50 pm
content: Dave, you need to retool your silkscreen so you've got all the letters on your OSHW logo!

author: free_electron
author_rank: Super Contributor
timestamp: November 04, 2016, 04:57:02 pm
content: Quote from: ali_asadzadeh on November 04, 2016, 11:25:27 amThis was invented By Maskless Imaging here in San Jose. they use 4 DLP engines to direct expose the board. there is a dithering process so they can create perfect rounded corners that are not possible with classic scanned laser direct imaging. they could make like 30 micron traces .. ( on 1/3 ounce copper) that is 1.1 mils trace and 1.1 mils gap ....I saw these machines in action about 4 years ago at APCT here in San Jose. they had 3 of them. very impressive.

author: rrinker
author_rank: Super Contributor
timestamp: November 04, 2016, 04:57:36 pm
content: Quote from: timb on November 04, 2016, 11:41:41 amNo, there's plenty of electronics inside it. The tapes are coded with instructions that tell it to say move the X axis 5.845" positive, and the axis motors on machine tools like that are servo feedback, not steppers like on a cheap home unit or 3D printer - WAY more accurate and repeatable. I don't think those early ones could do repeating instructions, withotu a micro. SO if you wanted to move 5" left, drill, move 5" left, drill, 4 times you repeated the instructions on the tape. Once they had microprocessors, they could code repeat instructions so you could say 4x move left 5" and drill. Plus you just loaded the tape once, into the computer memory,a dn then stored it safely off the shop floor. The old 550 we had was retrofited with a simple 8080 based control box that fit onto the paper tape reader and had 7 lamps, one for each row, and you could run the paper tape through and it would store it in the 8080's memory and then play it back using the lamps feeding the reader. Very kludgy but it worked. It was an interesting time in my life, done with school and truly on my own for the first time. Didn't pay that well but I learned a lot of interesting things.

author: nixfu
author_rank: Unknown
timestamp: November 07, 2016, 03:20:13 pm
content: I can't believe how manual the process is.This makes me amazed at how cheap PCB's can be ordered from china.I thought they were cheap because of increased automation, and figured it was almost as automated as a pick/place/reflow process.

author: seb30
author_rank: Contributor
timestamp: November 11, 2016, 06:52:42 pm
content: Interesting video that answer a question I ask myself for a long time : why we must use a PTH hole for reference coordinatein a design ? This is because PTH are drilled first and all the film are aligned on them !

author: Deridex
author_rank: Regular Contributor
timestamp: December 07, 2016, 06:35:37 pm
content: Quite interresting Video, that showed me some sides of my work i didn't know.