REGISTER | LOGIN
Home    Bloggers    Blogs    Article Archives    Messages    About Us   
Tw  |  Fb  |  In  |  Rss
Analog Angle

Can we get "printed" circuit boards which really are printed?

Bill Schweber
Page 1 / 2 Next >
eafpres1
eafpres1
10/27/2015 11:36:10 AM
User Rank
Blogger
A few more thoughts
Hi Bill--first, thanks for a great article.  Here are a few thoughts, we did a LOT of prototyping in our labs when I was in an antenna company:

1) A lot of our stuff was 2 sided, so it is "easy" to make a proto by removing copper with a purpose-built milling machine.  We had one that could take Gerber files and then machine the board.

2) LPKF and others will sell you an entire benchtop line if you want--the ability to SMT etc.  Pretty spendy for most labs.

3) Over the years there has been interest in certain applications, such as analog front ends, made using LTCC.  In some instances, you want to embed components inside the layers.  You cannot do that with rigid boards regardless of how many layers, unless you were super crafty and milled out a hole to make room for a component on another layer.  LTCC makes this a bit easier.  Here is an example from MuRata:  MuRata LTCC

So, the additive machine means you can prototype such a design!  AFAIK that isn't really feasible with any other benchtop process.

 

50%
50%
bobdvb
bobdvb
10/23/2015 10:03:12 AM
User Rank
Newbie
Re: Additive vs subtractive
I think one of the trade offs is not just scale but remember that an additive method could have the following advantages:
  • Energy usage: subtractive production may be efficient but only at bulk, it is inherrently an energy intensive process to keep the chemical baths hot and to do the lithography.
  • Chemicals: The subtractive process uses horrible chemicals that create safety and enviornmental risks. I think some companies would prefer a cleaner method even if it was a bit more expensive.
  • Waste: Substractive designs might be more wasteful, or at least require expensive reprocessing to recover the copper lost.

Sometimes the simple up-front cost isn't as big as the wider picture.

50%
50%
Bill_Jaffa
Bill_Jaffa
10/21/2015 5:25:17 PM
User Rank
Blogger
Re: Niche product
All very good points. Tube-based design is increasingly a lost art (and it is "art"--all designs and layouts are) and their support compoments are also harder to find.

Yet the audio world does do a surprising amount of tube-amplifier new designs, and tubes are still used for high-power transmitters and even TWTs in communication satellites. Of course, those transmitters do not use PC boards as we usually think of them at those currents and voltages.

50%
50%
comfusn
comfusn
10/21/2015 5:19:16 PM
User Rank
Newbie
"Handwired"
It was Zenith that boasted of hand-wired craftmanship.

50%
50%
jimfordbroadcom
jimfordbroadcom
10/21/2015 3:39:54 PM
User Rank
Artist
Re: Niche product
That's LPKF, not LKPF; sorry for the dislexia.

I forgot to mention about the superiority of PCB's vs. hand-wired circuitry.  The way I understand it is that hand-wired point-to-point wiring is better for vacuum tube circuits.  It makes sense when you realize that tubes (valves, to the Brits out there) are high-voltage, low-current devices for the most part; they are characteristically high-impedance devices.  Transistors, OTOH, are typically high-current, low-voltage devices - low impedance.  So what happens when you try to put a tube on a PCB with groundplanes like we typically use with transistors?  Well, all that capacitance makes the tubes very unhappy (as the late, great Bob Pease would say [RIP, RAP]) and they oscillate and roll off the high frequencies and other assorted nasties (probably another Pease-ism).  Transistors take it in stride, as long as you don't get crazy with the shunt capacitance.  Now, trying to make transistor circuits with (relatively) large inductances to ground and between stages from the long, isolated wires doesn't work well, either.  Can't use sockets for anything but the slowest transistor circuits or IC's.  Not a problem for tubes, though.

This is not to say that tubes can't be used on PCB's with their high-volume, low-cost, low labor intensity tendencies.  I think it's just a different philosophy of PCB design; keep one point for ground instead of a plane and route as much as possible on one layer, don't cross over signals if possible and make them cross at right angles if you have to make them cross (hey, we do that on transistor boards anyway), etc.  Anybody know where I can get surface-mount tube sockets?

50%
50%
jimfordbroadcom
jimfordbroadcom
10/21/2015 12:32:41 PM
User Rank
Artist
Niche product
This is definitely a niche product.  I previously worked at a company that had a board milling machine, and in about 2.5 years, I used it once.  The advantage was speed; we had a test board in about an hour, vs. at least 1 day for etched wiring boards (EWB's, as the military used to call them - I've been out of that circle for >20 years so I don't know what they call them today) if you want to pay big $$.  If you can wait a couple of weeks, OSH Park has boards for extremely low prices; I paid less than $90 for 3 boards this summer!  Other shops charge more of course, and finer lines and spaces and quicker delivery drives up the cost.  We find that the minimum order for say 10 boards is about $1500-2000, and for the finest pitch boards, we can spend upwards of $20,000 for a batch.  I think if you have to have your simple boards very quickly, or as the LKPF people like to point out, you're the FBI or CIA and absolutely have to have your boards built in-house to keep your secrets secret, a circuit board printer is the way to go.  Otherwise, it doesn't make sense not to use an outside fab shop.

50%
50%
Bill_Jaffa
Bill_Jaffa
10/21/2015 7:35:44 AM
User Rank
Blogger
Re: Additive vs subtractive
I think the real benefit here would for prototyping, to test out a circuit concept or get a quick board so you could write and debug the software. That's where prototypes wihc are not "geometrically" equivalent to the final board cause problems. So if this printed technique used real PC board substrate such as FR-4, and the tracks had the same geometry, that would be a big help in the product development/debug phase. I agree that it might have serious shortcoming for full production, but that's later in the cycle.

50%
50%
David Ashton
David Ashton
10/20/2015 6:33:06 PM
User Rank
Artist
Printing circuit boards
There would be certain advantages to "printing" circuit boards, depending on the process.  You could print certain tracks not only wider but thicker - and if you could make them thicker you needn't have them as wide for the same current-carrying capability.  And if the printing was robust enough you could get over the problem of tracks separating from the board due to mechanical stress (eg power connectors).  But depositing molten copper on fibreglass is probably not the way to go - you'd have to come up with some other material.  Not to knock the voltera machine, but it probably wouldn't cut it for high-current stuff.

50%
50%
dick_freebird
dick_freebird
10/20/2015 5:34:02 PM
User Rank
Teacher
Additive vs subtractive
Subtractive copper plated boards (if you only need 2-sided)

are so commoditized (ditto etchant, the EPA aside) that an

additive process would have an impossible time competing.

Once you get to internal layers, things are no longer so

clear - plenty of fine work inside the sandwich that must now

be built up. Probably quasi-additive in some sense, but still

the PCB houses attempt to squeeze out cost by panelizing

and batch processing at steps where they can.

 

Silver ink? That's adding cost. And taking you off the map

as far as reliability design rules (let alone UL recognition). 

Maybe fine for playing around, but what happens when you

decide you want to run serious current + temperature on

this print-head-friendliness-first composition trace?

50%
50%
More Blogs from Analog Angle
As technology evolves and advances, long-established parameters may no longer be relevant or useful, and new ones take their place.
Analog circuits inherently have some inaccuracies; if these exceed the allowable specification, there are three general strategies to dealing with them.
It has to hurt when your released product is cancelled and goes into the dumpster, but should it?
The “down to earth” world of analog components and functions is a reality-based counterweight to the relentless. overhyped views of the direction and impact of technology advances.
Analog, discrete-element filters have served us well for over a hundred years, but maybe we now need to focus education on filters for the GHz world, such as SAW and BAW devices?
flash poll
educational resources
 
follow Planet Analog on Twitter
Planet Analog Twitter Feed
like us on facebook
our partners
Planet Analog
About Us     Contact Us     Help     Register     Twitter     Facebook     RSS