Silk screen is not dot matrix! - Page 1
Forum section: electronics / general

author: vlad777
author_rank: Frequent Contributor
timestamp: September 07, 2017, 09:35:00 pm
content: Hi,Dave I heard you say, that silk screen is dot matrix printed, but I think this is wrong.I think that the artifacts come from the screen (grid of fibers) in screen printing.In the video we see silk applied in a Chinese factory.19:42

author: ataradov
author_rank: Super Contributor
timestamp: September 07, 2017, 09:49:40 pm
content: There are many ways silk screen may be applied. Some use printers, which is convenient because you don't need to manufacture the screen itself, and labors costs are way less.In a Chinese sweat shop environment old style silk screen is going to be prevalent, since labor is cheap. Those printers are not cheap to buy and maintain.

author: vlad777
author_rank: Frequent Contributor
timestamp: September 07, 2017, 09:56:08 pm
content: If you have a visual example, I would like to see it. (Really , just adds on to my experience.)

author: ataradov
author_rank: Super Contributor
timestamp: September 07, 2017, 10:00:20 pm
content: I think Dave had a video tour of some factory where they use direct printing.Here is a random video from YouTube:

author: vlad777
author_rank: Frequent Contributor
timestamp: September 07, 2017, 10:03:33 pm
content: Inkjet - no artifacts.

author: Cerebus
author_rank: Super Contributor
timestamp: September 07, 2017, 10:38:43 pm
content: Why do you think an inkjet print would have no artefacts? It does at the scale of ordinary household inkjet printers and with the high ink deposition and viscosity necessary for a board I'd expect it to have more, and in practice it does.On the other hand 'silk' screen prints, done properly, show no hint of the screen in the finished print. Find a screen printed tee shirt and try to find any printing artefacts and you won't, barring the odd manufacturing error, and they use much coarser meshes than PCBs. The stencils used provide a continuous edge to the print and if you run the right amount of ink (usually requiring a 'flood pull' with the screen out of contact with the printing surface before you make the actual printing pull) the ink flows to fill in any areas where the screen might block ink from the print.On longer runs of medium quality boards (certainly down to 8/8mil) screen printing is used to apply the patterned resist before etching, the patterned solder mask after and the final silk screen and if either of the first two had artefacts the board would fail completely

author: vlad777
author_rank: Frequent Contributor
timestamp: September 07, 2017, 10:58:53 pm
content: I would like to see a video of a dot matrix print head in action , of depositing white paint ...

author: ataradov
author_rank: Super Contributor
timestamp: September 07, 2017, 11:01:58 pm
content: Quote from: vlad777 on September 07, 2017, 10:58:53 pmThat would be hard to do, since all machines I've seen have pretty closed volume for the board. And I doubt there is a video of the head outside of the machine. I mean, can you find such a video for a regular ink jet printer head?

author: vlad777
author_rank: Frequent Contributor
timestamp: September 07, 2017, 11:05:43 pm
content: Quote from: ataradov on September 07, 2017, 11:01:58 pmYeah, someone should do that.

author: Cerebus
author_rank: Super Contributor
timestamp: September 07, 2017, 11:47:47 pm
content: Quote from: ataradov on September 07, 2017, 11:01:58 pmOne might just manage to do it with a USB endoscope (or similar) while printing on clear acetate, if there's room below the medium as the print head flies past. One would probably have to examine dozens of printers to find one that it would be possible on. Itwouldmake a cool video.On second thoughts this might actually be easier to do on a printer specialized in handling rigid media (like PCBs) as there's more probability of finding some space below the medium where an inkjet printer would have a platten for continous support but a PCB printer might just have occasional rollers alternating with empty space.

author: EEVblog
author_rank: Unknown
timestamp: September 08, 2017, 12:12:21 am
content: Quote from: vlad777 on September 07, 2017, 09:35:00 pmThere are three ways I am aware off:1) Traditional silkscreen. I don't think anyone actually uses this any more.2) "Dot matrix" inkjet type printed. Very common on cheap boards and you can clearly see it under magnification.3) Photoimagable (like copper and solder masks are done.

author: EEVblog
author_rank: Unknown
timestamp: September 08, 2017, 12:16:52 am
content: I have a video of the photoimagable process here.Starts at 14:00

author: vlad777
author_rank: Frequent Contributor
timestamp: September 08, 2017, 12:17:34 am
content: Quote from: EEVblog on September 08, 2017, 12:12:21 amI think the video (in my original post) shows the "traditional" type , in a very modern and high end factory.I am not sure if you should use words "dot matrix" if it refers to inkjet.

author: vlad777
author_rank: Frequent Contributor
timestamp: September 08, 2017, 12:24:07 am
content: Quote from: EEVblog on September 08, 2017, 12:16:52 amThe guy is using screen printing with no pattern , just to apply the photosensitive white paint.(Let me watch the whole video.)Edit:Excuse me, photoimageable material that happens to be white.

author: helius
author_rank: Super Contributor
timestamp: September 08, 2017, 01:59:18 am
content: The resemblance to screen printing is very close and I'm sure that isn't accidental. The difference is that the UV-curing (photoimagable) liquid is exposed and hardened directly on the board, instead of on a screen. There is less generation loss—with silk screening, the quality of the print is variable based on how many prints have been pulled through a screen and how many times the screen has had to be cleaned of ink (each time it is put away). With this process, there is no need to store the screens for each project, as they are effectively all blank for every project.What you cannot do (anywhere near as easily) is to print in multiple colors, as you can with screen printing using a screen per ink color.

author: EEVblog
author_rank: Unknown
timestamp: September 08, 2017, 02:14:34 am
content: Quote from: vlad777 on September 08, 2017, 12:17:34 amErr, inkjets work exactly like old dot matrix printers, they deposit drops of ink, i.e. "dots".

author: vlad777
author_rank: Frequent Contributor
timestamp: September 08, 2017, 02:59:49 am
content: Quote from: EEVblog on September 08, 2017, 02:14:34 amLogically you are correct.But is that the industry lingo? (I don't know ,just asking honest question.)

author: EEVblog
author_rank: Unknown
timestamp: September 08, 2017, 03:31:44 am
content: Quote from: vlad777 on September 08, 2017, 02:59:49 amSure. Anyone in the industry would know exactly what I mean.A lot of younger people would more readily identify "inkjet" with dot printing, because that's what they grew up with. But older people might more readily identify with "dot matrix" printers using pin heads and ink tape.Both are the same thing, except one squirts ink through a nozzle, and the other fires a steel pin against an ink soaked ribbon.Both are "dot matrix" because the printed characters are formed with a matrix of ink dots.

author: Brumby
author_rank: Unknown
timestamp: September 08, 2017, 03:38:55 am
content: In my experience, the lingo has evolved with the technology.Since impact printers are not as prevalent, the process of creating an image (whether it be text, graphics or photos) on a medium by using a matrix of dots has allowed the term to extend into the area of inkjets ... IMO.Quote from: EEVblog on September 08, 2017, 03:31:44 amExactly.

author: vlad777
author_rank: Frequent Contributor
timestamp: September 08, 2017, 03:43:22 am
content: Heeeyyyy....Is there a small version of this inkjet that prints in thick, etching resistant paint?This could make my life much easier when it comes to etching a board.(I usually go with thick traces, so somewhat low res may not be a problem.)

author: Brumby
author_rank: Unknown
timestamp: September 08, 2017, 03:47:45 am
content: Quote from: EEVblog on September 08, 2017, 03:31:44 amAbsolutely ... and if there was any doubt, context would resolve it.QuoteThis is the evolution of language at work. An established term takes on new meaning through changes in the features and/or processes of the original subject. Happens all the time.

author: EEVblog
author_rank: Unknown
timestamp: September 08, 2017, 06:08:21 am
content: Quote from: vlad777 on September 08, 2017, 03:43:22 amYes, many people have tried this with varying result directly onto copper clad PCB.Epson printers are go I believe because the ink/head used.

author: Ampera
author_rank: Super Contributor
timestamp: September 08, 2017, 07:52:55 am
content: Funnily enough, I still use a dot matrix impact printer for occasional prints. It's slow, but the ribbons aren't that expensive, and it works with everything (Unless it has windows 10, thanks BILL GATES) even a Commodore 64.

author: vlad777
author_rank: Frequent Contributor
timestamp: September 08, 2017, 09:00:08 am
content: Quote from: EEVblog on September 08, 2017, 06:08:21 amAny links, if I may ask, thanks!Edit:Oh , there is a ton of videos on YouTube , sorry.Well , mounting a inkjet head on a CNC seems to me like most reasonable thing to do.

author: Cerebus
author_rank: Super Contributor
timestamp: September 08, 2017, 01:10:42 pm
content: Quote from: EEVblog on September 08, 2017, 12:12:21 amOh, it still is. The people who make 100,000 single sided SRBP power supply boards aren't going to go with the time and expense of:Applying photo imageable resist/inkexposing itdeveloping itrinsing itdrying itwhen the whole thing can be prepared in few seconds by screen printing a UV drying resist/ink onto the board. It's a niche, but it's a niche that makes millions of boards a year.It's possible that some people in this market segment are switching to flexography (which has been getting more precise year on year) in the same way that people in mass packaging manufacture have moved from screen printing to flexography.