There is PCB and then there is PCB

[mooreamps]

Now to the million dollar question: what do the military use today?

I leave the question open for anybody qualified to answer.

Depends on the application.... For aerospace, it's pcb ; non-conformal coated. But all the parts must pass fine and gross leak to check for device seal and out-gassing.. On the other hand, for cards used in the Bradley tanks, 12 of them as I recall in the main control Fire Box, they are pcb's which are conformal coated... For crypto, those cards are pcb, non-conformal coated..

-g

[Steve Conner]

Haven't you noticed the diminishing availability of through hole components?

Well, here's one I designed and had assembled for me earlier. The main board is 6 layers, and a little thicker than 1/8".

[Alex/Tubewonder]

Well, here's one I designed and had assembled for me earlier. The main board is 6 layers, and a little thicker than 1/8".
[ATTACH=CONFIG]12690[/ATTACH]

So, how does it sound

[J M Fahey]

So, how does it sound

Don't think it "sounds" very much or at all.
It looks like something Saddam would have *loved* to have.
Or worse.
Just in case, I'm wrapping my head in tinfoil and *grounding* it. (that's what all those non-technical nuts always forget to do)

[GregS]

Now to the million dollar question: what do the military use today?
PTP in any of its forms or PCB?
I leave the question open for anybody qualified to answer.

I don't know what the military use today but the obvious answer is PCB. However, not all PCB's are the same in terms of their robustness and reliability. I seriously doubt that those found in modern cheap mass produced amps would be up to military standards. They fail from use in amps so they would not be suitable in any application where reliability was paramount.

Which leads me to the question of how the PCB's are manufactured in modern guitar amps. I have a recollection reading somewhere that the components are physically inserted on the boards by a machine and that the whole board is dipped in a solder bath. Areas of the board not to receive solder are masked off. Is this how it's done?

One thing that doesn't make sense to me is components already on the board being immersed in hot solder. Anyway, according to some, this method of soldering is the reason for non-substantial solder joints which eventually fail.

[MWJB]

most boards in guitar amps are single sided, there would be no reason to dip the whole board in solder.

It's rarely the method of soldering during construction that causes solder joints to fail (which in itself is pretty rare, I for one am very skeptical of all these claims of, " I reflowed the joints and all my woes were cured"), it's more often heat related, either hot components like tubes direct into the PCB, or resistors that have to dissipate a lot of heat soldered with too little lead length to allow them to expand & contract safely. More often than not, it is the component itself that fails...& it would fail in the same environment were it in an eyelet board.

I worked for a defense contractor, all circuit boards that I saw were PCB.

[Jazz P Bass]

Which leads me to the question of how the PCB's are manufactured in modern guitar amps. I have a recollection reading somewhere that the components are physically inserted on the boards by a machine and that the whole board is dipped in a solder bath. Areas of the board not to receive solder are masked off. Is this how it's done?

One thing that doesn't make sense to me is components already on the board being immersed in hot solder. Anyway, according to some, this method of soldering is the reason for non-substantial solder joints which eventually fail.

The "masking" is specified as part of the PCB design process.
When you layout the board there are levels.
One is the solder mask.
The mask is where you do not want solder to adhere.
So when you look at a bare, unstuffed board, there are shiny areas where components are mounted.
The board manufacturer is responsible for putting down the mask layer.
And yes, most assembly is by machine.
Pick & Place.
The solder process is usually "Wave Soldering".
A titanium rack full of stuffed boards is soldered by a vacuum pulled wave of solder.
A preheat time is called for before soldering.

[Steve Conner]

Modern SMT boards are usually done by reflow soldering. The board is screenprinted with solder paste, then the pick and place machine plops the components into it, and finally the board travels through something not unlike a giant toaster oven, melting the solder and sticking the components firmly in place when it cools. Wave soldering was for through-hole.

You can run SMTs through wave soldering, but it needs special board design, not to mention dabs of glue to stop the tiny helpless things from being swept to their doom by a tidal wave of molten lead.

You can also reflow solder through-hole components, but it's tricky. This is one of the forces driving the adoption of SMTs. Once you've started using some of the little buggers on your board, there's a strong compulsion to change to reflow soldering and eliminate as many of the through-hole parts as you can. As a compromise, the board I showed above is reflow soldered on the top, and wave soldered on the bottom, so it only has SMTs on the top. The other guys I was working with really wanted the daughtercard connectors to be through-hole for mechanical strength.

The solder mask is the green lacquer stuff.

[Ronsonic]

Now to the million dollar question: what do the military use today?
PTP in any of its forms or PCB?
I leave the question open for anybody qualified to answer.

Good question that brings up a good point but obscures other good points. Mostly mil-spec stuff is PCB through-hole and hand soldered.

Here's what is ignored - the mil-spec stuff of the 40s onward still works. A proven record like that is inarguable. However reliable today's spec is, it doesn't have all those decades of proven reliability. Even the electronics in artillery shells and missiles was once PTP vacuum tube stuff, proximity fuses and the like.

We don't exactly have military budgets, either.

Anyway, it is a good point. PCBs can be extraordinarily reliable and are just plain the only sensible way to produce a lot of modern designs.

Either technology requires careful design work for best results. I can design a Hiwatt style cable loom as could others here. But if some schmoe just got the idea to bundle his wires like that it would be a disaster. Same with PCB layout.

I'd also point out that Leo's board is well under the standard of what I've seen in mil-spec gear of the 50s and 60s. I don't think that warpy phenolic board would've passed muster.

[mooreamps]

most boards in guitar amps are single sided, there would be no reason to dip the whole board in solder.

So what are you saying... Amps that are single ended have one side pcb's ; and amps that are push/pull are double-layer boards.. :}
So, that's how they do that...

-g

[Alex/Tubewonder]

You didn't know this? Dipping the board in solder is a much more efficient in hiding evidence of a rip off than gooping.

[Ronsonic]

most boards in guitar amps are single sided, there would be no reason to dip the whole board in solder.

It's rarely the method of soldering during construction that causes solder joints to fail (which in itself is pretty rare, I for one am very skeptical of all these claims of, " I reflowed the joints and all my woes were cured"), it's more often heat related, either hot components like tubes direct into the PCB, or resistors that have to dissipate a lot of heat soldered with too little lead length to allow them to expand & contract safely.

You aren't working in our world. Wave solder is at its worst with large components which soak up a lot of heat and components mounted near the edges of the board where the wave doesn't propagate fully. This gets worse when the manufacturer pushes the throughput and economizes on the solder. The most common solder failures are on things like jacks and pots that are well away from the heat. The main advantage of double sided boards is the plated through holes. Those produce much more robust joints than single sided. There's a reason most mil-spec stuff is hand soldered, you don't have the issues of wave soldering.

[Chuck H]

But wave soldering is eventually how most of the crap from the big MFG's will be done. I've read a few nightmare stories about current attempts with wave soldering using lead free solder. Just to add another aspect to this discussion. As I see it the failures prone to PCB's are exacerbated by lead free solder while other hand wired methods are more easily compensated. It's a moot point really because who can afford to sell a hand wired amp? Probably best to find the most durable and servicable PCB system at this point. At least from a MFG perspective. I still build on eyelet boards so what do I really know about it.

[R.G.]

But wave soldering is eventually how most of the crap from the big MFG's will be done.

Just to be factual, it's also how most of the *entire* production of manufacturers of any size, up to the biggest ones, whether low end crap or the finest high dollar stuff, is done. And wave soldering can be amazingly consistent once you get the line tweaked in.

I've read a few nightmare stories about current attempts with wave soldering using lead free solder.

I could add one for you. They were doing the lead free changeover in our factory when I was getting the Workhorse amps up and running. We had to ride herd on the factory until the changeover was up and running correctly. You may have read my comments on lead-free solder as being the work of the devil in other posts.

But it's something you work through. Production engineering is an acquired skill, just like learning to take a full wrap on a solder turret or lug before soldering. The true disasters are people who don't know that to get quality you have to work at it. And work at it. And work at it...

Building a few of anything is the worst situation. You can't afford the time to hand-tune every one, and you can't afford to throw away the first hundred while you get the process/line tweaked in and running right.

[gbono]

Now to the million dollar question: what do the military use today?
PTP in any of its forms or PCB?
I leave the question open for anybody qualified to answer.

Mmmm sorry if we tell you that - you will be terminated with extreme prejudice

What frequencies do you want to propagate? That dictates what construction and materials will be need - you can't use FR4 at 6GHz.

The US (and other industrial military complexes) have moved more programs to COTS procurement to save $$. The spooky stuff still gets made by hand though