# Will we ever see SMD PedalPCBs?



## bengarland (Apr 11, 2020)

Will we ever see SMD PedalPCBs?

Coming from the world of DIY synth, I actually prefer SMD if it's 0805 or 1206 size -- this is big enough that you don't need any specialized equipment.

I realize that some boards can't really be physically shrunk down more since there are limitations imposed by the spacing needs of pots and switches, but I'd really like to see SMD anyway because I find it's easier to do, easier to troubleshoot, easier to source most parts, etc. Then again, I'm probably in the minority so I doubt it's worth the effort from a business standpoint.

Thoughts?


----------



## Chuck D. Bones (Apr 11, 2020)

Personally, I have no interest in SMD boards.  To me, they are harder to build _correctly_. They are not as robust as thru-hole and are easily damaged by shock and vibration. Hand-soldering is not a good way to assemble SMD boards because it is nearly impossible to hand solder parts without stressing them thermally. When I worked in aerospace, it was forbidden to touch an SMD capacitor with a soldering iron because too many of them failed in the field due to stresses induced during hand soldering. The right way to solder SMD boards is with solder paste and a reflow oven.

SMD has advantages if you mass produce and need the high packing density.  Other than that, meh.

Thru-hole JFETs are rare now and I expect that SMD JFETs will go the same way because there is not that much demand for discrete JFETs in any package.


----------



## bengarland (Apr 11, 2020)

That's a good point, I suppose guitar pedals go through much more abuse than my modular synth which I treat like it's a baby 

I didn't realize SMD components are possibly more heat sensitive and failure prone than THT. Is this still true nowadays? I haven't seen this issue mentioned specifically for SMD (beyond the general heat warnings that apply equally to THT components) but I'd like to read more about it and make sure I'm using best practices. I learned most of my SMD stuff from watching videos by Dave at EEVblog but I'm always looking to improve my technique. So far I haven't fried anything  

There are good arguments on both sides of the debate, and I figure there must be some great reasons that the DIY guitar pedal scene is still largely THT. I'm so new at this that I definitely defer to the knowledge and wisdom of the veterans around here!


----------



## Vildhjuggah (Apr 11, 2020)

If I was making pedals for people, and I let an oven do all the soldering and checked it after then i'm sure it'd save time, but unless i'm doing that I don't see any pros besides that desoldering would be easier.


----------



## Barry (Apr 11, 2020)

SMD takes all the fun out of it, can't socket and experiment with different values, too tiny for my ancient eyes and there's just something about firing up the iron and threading components that I like and so far SMD is just meh.


----------



## vigilante398 (Apr 12, 2020)

I do all SMD for my pedal designs. I have a cheap reflow oven and I buy stencils when I get my PCBs, I only ever have to hand-solder when I'm troubleshooting or modding. I like being able to squeeze things small (my best so far is a deluxe memory man in a 1590B), also if you get creative with things there are a lot more component options like voltage regulators or specialized ICs that they don't bother making in through-hole.

I don't work in a production house for aerospace stuff, but I work in aerospace R&D and we've had plenty of flying prototypes with hand-soldered PCBs. Obviously you have to have certified technicians doing the soldering, but if the techs know what they're doing there's nothing wrong with hand-soldering SMD components. If you're using low-quality components sure you can have problems, but if you're using X5R or better (we're not allowed to design around anything below X7R at work) caps you should be fine.

Also how often do you vibrate or flex your pedals? I have been doing SMD for years now and have never once had a component pop off.

SMD rocks


----------



## lcipher3 (Apr 13, 2020)

vigilante398 said:


> I do all SMD for my pedal designs. I have a cheap reflow oven and I buy stencils when I get my PCBs, I only ever have to hand-solder when I'm troubleshooting or modding. I like being able to squeeze things small (my best so far is a deluxe memory man in a 1590B), also if you get creative with things there are a lot more component options like voltage regulators or specialized ICs that they don't bother making in through-hole.
> 
> I don't work in a production house for aerospace stuff, but I work in aerospace R&D and we've had plenty of flying prototypes with hand-soldered PCBs. Obviously you have to have certified technicians doing the soldering, but if the techs know what they're doing there's nothing wrong with hand-soldering SMD components. If you're using low-quality components sure you can have problems, but if you're using X5R or better (we're not allowed to design around anything below X7R at work) caps you should be fine.
> 
> ...



Aerospace here too - same experience (FADEC / ECU design, etc)  Amazing what you can do in RD with a tech that has hands and eyes of a surgeon.   Ever see a 1mm strain gage wheatstone bridge soldered with 40AWG wire?!  I'm good but not that good.


----------



## phi1 (Apr 13, 2020)

Cool thread, lots of good info.  I was planning on doing a design with hybrid smd and thru hole to increase desnsity.  I was already planning on doing smd chips, resistors, and diodes, but thru hole capacitors, since in my experience smd capacitors are a little harder and I don't like working with them since there's no labeling.

I'm not a certified solderer haha.  Chuck, you specifically mentioned capactiors, is there more concern with thermal stress on capacitors than the other components, because of there structure?

Anyone have any other recommendations for hand soldering smd, like max iron temp, or max amount of time with heat applied?  (and of course using a small tip).


----------



## bengarland (Apr 13, 2020)

I'm not an expert but based on almost a year of building a few dozen SMD boards for synths I use the same tip for 0603 (or larger) SMD as I do for thru hole. It's a Hakko "BC" (angle cut) style about 2mm in diameter. I quickly found that smaller tips don't transfer heat nearly fast enough -- I only use the small tip when I'm fixing solder bridges on super fine pitch ICs like a STM32 with 16 pins on each side. Dave at EEVblog also uses large size tips for most SMD and I tend to defer to his expertise. "SMD needs small tips" is one of those things that sounds correct, but isn't, in most situations.

I use a Hakko FX-888D soldering station set to 345C with 60/40 solder. Works great for me. Other people recommend 400C. Of course that depends on what tip you're using and how well your station can maintain heat at the tip. Try a few different temps and see what works best for you. The important thing is to get in, get out. It's better to heat with a high temp for shorter duration, than a lower temp for twice as long.


----------



## bengarland (Apr 13, 2020)

It just occurred to me that another benefit of THT for guitar pedals is that it's so common to do personal mods like adding extra switches and knobs (from wires easily inserted into existing holes on the PCB) or sometimes bridging two legs of an IC or jumping wires from one part of the board to another or to a breadboard. That's a LOT harder to do with SMD. It's not impossible with good magnet wire and some practice, but it's not something I'd want to do regularly.


----------



## steelplayer (Apr 14, 2020)

Great thread, lots to read and learn here!

I'm getting ready to make my first order for some boards and I'd love to build the Bohemia.  My soldering skills are ok and I have a decent temp controlled station, --hobby builder here-- so my question is about the SOT23 through-hole adapter boards for CMPF4393.  I've seen lots of different opinions concerning soldering difficulty, reliability and temperature sensitivity.

--How difficult to solder? 
--Hot-air rework station a good route to go?
--Adapter board fit ok on Bohemia board mounted with right angle pins?


----------



## vigilante398 (Apr 15, 2020)

I use a hot air rework station for removing components, but never for soldering them down. For whole boards I use a cheap ($200) reflow oven I got on amazon, and it does a great job. For modding or rework I use my typical solder station. I generally keep it around 650 degrees (F), as mentioned above that will depend on your iron, your solder, your tip, and how well your iron heats the tip, but the tip itself counter-intuitive. I've seen a lot of people go to a tiny tip for SMD soldering, but I recommend a chisel tip. You want to be able to heat up the joint as quickly as possible so you don't have to park your iron on the component for a long period of time, because that's how you kill your components.

As for difficulty of soldering, it depends on component size. I don't go below 0805 for passives on pedals, because most of the time there isn't any need to. I can squeeze just about anything into a 1590B with 0805 passives. I also don't like doing anything tighter than standard SOIC package IC's. Most of the parts you need for pedals you can get in a standard SOIC packages, going smaller pitch increases the risk of bridging pins.


----------



## giovanni (May 10, 2021)

I read somewhere that pedals built with SMDs have a lower noise floor. Is that a thing?


----------



## JetFixxxer (May 10, 2021)

giovanni said:


> I read somewhere that pedals built with SMDs have a lower noise floor. Is that a thing?


I'm going to say there is some truth to that (but I'm not an expert), because of thru-hole components have more of their leg/pins exposed. Which could act like an antenna.  Again I just dabble in the world of electronics.


----------



## Chuck D. Bones (May 10, 2021)

giovanni said:


> I read somewhere that pedals built with SMDs have a lower noise floor. Is that a thing?


It might have a better noise floor if we were building microwave hardware.  The advantages of SMD assemblies are:

The boards can be smaller for the same part count.  Or you can cram more parts on the same sized board.  It's also possible to populate both sides of the board to save space.   I have a Chinese Klon Clone that is all SMD except the Ge diodes.  It fits in a 1590A box and cost me $35. 
Which gets us to the next advantage: Production cost.  If you want to bang these out 1,000 at a time, then the recurring cost of running boards thru an SMD assembly line is lower than a thru-hole assembly line.
PCB fabrication cost.  PC fabricators charge by the square cm and by the hole when they sell boards in bulk.  SMD boards will have more vias, but a lot less thru-holes than a conventional thru-hole board.
Some parts, like new production J201s, are only available in SMD packages.
Now for the disadvantages:

Ever tried to put an SMD in a socket?  Mounting it on a carrier board so it becomes a thru-hole part is cheating.
Soldering SMDs requires a lot more skill, time and better tools.  Clearances between pads and traces are smaller, making alignment critical.
Soldering a leadless part is very stressful (to the part), particularly chip resistors and capacitors.  In hi-rel SMD assembly, it is forbidden to touch capacitors and resistors with a soldering iron because it significantly degrades their reliability.  The right way to solder SMD boards is in a reflow oven.
Assembled SMD boards are more fragile than thru-hole boards.  When an SMD board is flexed, all of the stress concentrates at the solder joints and across the smallest parts.  No board is perfectly flat and the mounting holes are not perfectly aligned.  Between mechanical tolerances, shock and vibration, board flexing will happen.  Leaded parts can accommodate more board flex because the leads will bend and relieve some of the stress.  The rigors of the road will break a SMD board long before they break a thru-hole board.
As an aside, any part that can be mounted thru-hole can also be surface-mounted, it's just a matter of forming the leads and having the right pad pattern.  I've seen it, I've done it.

Back in the later 80's and up to around the turn of the century, the Aerospace industry was busy qualifying design and manufacturing processes for military & space applications.  They understood the advantages of SMD production and invested considerable effort and expense to get it right.  I was there and I saw first-hand what is possible when it goes well and what happens when it doesn't.

For sure guys like Josh Scott will sing the praises of SMD boards because they are more profitable.  Nothing wrong with that, but you need to understand the motivation when someone tells you "SMD boards are better."


----------

