I'm a little bummed because I'd really like to start learning how to work with SMD components, but there seems to be a huge resistance to it in the DIY community. From my understanding, once you get the hang of it there are nothing but benefits (cheaper parts, less drilling, smaller boards, etc.)
Your take?
- Hard to solder
- Can't read cap values
- Not readily available at our favourite suppliers (smallbear, aron's, banzai, etc.)
- Not available in small quantities
Those are just some things I associate with SMD, not based on actual experience
^ What ~arph just said.
Plus, I'm old, and don't like change. I've been using through hole components for my whole life, dag nabbit, and I'm not about to change now!
Seriously, I don't see the need to change.. I've been stocking up on all this thru-hole stuff, and now I'm supposed to start stocking up on SMDs too? Grrr...
I could make an acception, I suppose, like maybe using one of those converter-daughter board things, to "convert" a surface mount IC for use on an otherwise thru-hole board. And of course, once I had a little bit of SMD experience under my belt, I might be less intimidated by all of it. So, I won't ever rule out SMD.. I'm just not ready to take the plunge yet.
Plus, it don't have the mojos. :icon_lol: :icon_rolleyes:
Quote from: John Lyons on December 10, 2010, 11:00:31 AM
Plus, it don't have the mojos. :icon_lol: :icon_rolleyes:
You mean they don't make SMD Orange Drops or tropical fish caps? ::)
I have been using SMD components for a while now, I have to say they make life much easier for the most part
Some advantages i have found.
- Easy to solder
- Cheaper components
- Readily available where i shop.
- Caps available even if you just want one.
- If I need to replace an IC it's far easier and quicker to remove without causing any damage.
- No holes to drill, well relatively few,
One Dis sadvantage is that quality capacitors, can be very large so there is no space saving benefit here. (tant beads excepted)
I believe most people are against SMD because they think it's difficult to do
Tools i use are small soldering iron (same as i use for thru hole components) tweezers to hold a component in place, and lastly a hot air soldering iron for flowing ic pins (cost £30 from maplin)
SMD is not hard to solder, it just takes a different set of techniques. 1206s are not hard to solder, soldering tiny pads for through hole components are harder than soldering these things. I can solder 0603 no problem, but I have issues reading the resistor values.
No cap values are an issue. A cap tester can solve this, I just don't own one.
Mouse/Digikey/whoever sells them in singles no problem
This comes from making designs and sourcing parts for said projects and hand soldering them myself. I actually prefer SMD to through hole for basic components. No need to flip the board, snip leads, or any of that crap. I have issues not socketing ICs though.
I just received my first smd components last week, so I will be using them soon. It's SSM2166 in SOIC14 btw.. I guess that's doable with my tiny tipped weller. Still pondering wheter I need this flux stuff...
So Ice-9 Just gave us another disadvantage :P
- You need special tools
Quote from: therecordingart on December 10, 2010, 11:01:52 AM
Quote from: John Lyons on December 10, 2010, 11:00:31 AM
Plus, it don't have the mojos. :icon_lol: :icon_rolleyes:
You mean they don't make SMD Orange Drops or tropical fish caps? ::)
There is no such thing as Mojo. :-\ ::)
Quote from: ~arph on December 10, 2010, 11:08:15 AM
I just received my first smd components last week, so I will be using them soon. It's SSM2166 in SOIC14 btw.. I guess that's doable with my tiny tipped weller. Still pondering wheter I need this flux stuff...
So Ice-9 Just gave us another disadvantage :P
- You need special tools
Kna you don't need any special tools, i can hand solder a 48pin TSOP chip with my little antex iron, but it is a little easier with a portable hot air iron
Yeah, but a magnifying glass and tweezers? stuff I normally don't use..
For the record, I am seriously considering going to SMD. I am hesitant as this will mean a restock. Plus I still need the through hole stuff for the breadboard.
Breadboarding means two sets of components. Thats probably the best point i have heard against up to now.
Quote from: Ice-9 on December 10, 2010, 11:41:33 AM
Breadboarding means two sets of components. Thats probably the best point i have heard against up to now.
That's a pretty big one for me, since I tend to breadboard everything before building. Having two sets of components isn't out of the question, of course, but it is a drawback.
SMD all the way ...through hole is solely for breadboarding & big girls blouses.
Advantages (for me)...
Parts are cheaper.
Some of the cutting edge parts are only available SMD
no tedious drilling
no tedious hand soldering (use paste & then either 'flow' via an oven or hand held hot air tool)
smaller footprint (size costs)
quicker to make a board up.
Easier to store (eg http://cgi.ebay.co.uk/50x-Electronic-Case-Component-Box-Storage-SMT-SMD-Kit-/160466782264?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item255c90c838 )
neater (less DIY look!)
probably others but you get the gist....
The only thing I bought to help was a pneumatic solder paste dispenser.
As far as I know, there's no equivalent of vero or perf for SMD, so for me as well as learning to solder it I'd have to switch to making PCBs. As a DIYer who only ever builds one of anything, that's just too much hassle for no real advantage.
Quote from: Gurner on December 10, 2010, 12:05:00 PM
SMD all the way ...through hole is solely for breadboarding & big girls blouses.
The only thing I bought to help was a pneumatic solder paste dispenser.
Hi Gurner, do you have a link for the pneumatic paste dispenser, i've been wanting to try this way for a while.
I use SMD components for some things, usually to avoid standing up resistors on consecutive rows when using vero, but the main reason why I don't think I'd ever be interested in using them exclusively is because I can't see any point whatsoever for most of the things I build to miniaturise it any more. Virtually everything I want to build will fit comfortably in a 1590B, even a lot of the time when using axial components, so I can't think of many good reasons to make future servicing of the pedals more difficult.
Quote from: slacker on December 10, 2010, 12:09:47 PM
As far as I know, there's no equivalent of vero or perf for SMD, so for me as well as learning to solder it I'd have to switch to making PCBs. As a DIYer who only ever builds one of anything, that's just too much hassle for no real advantage.
Ah, yeah.. I mostly use perfboard, so SMD won't work for me in those cases..
I have no objection whatsoever to SMD chips, and maybe even transistors and some caps, but resistors? Fuggedaboudit.
Quote from: Ice-9 on December 10, 2010, 12:13:20 PM
Hi Gurner, do you have a link for the pneumatic paste dispenser, i've been wanting to try this way for a while.
Yep, here's the one I bought -
http://cgi.ebay.co.uk/Solder-paste-glue-liquid-auto-dispenser-SMD-PCB-Pro-/180524776997?pt=LH_DefaultDomain_0&hash=item2a081d7e25
I knocked up my own compressor (taken out of a fridge at the local refuse tip!) ...it all works very well (I buy the paste from Deal Extreme for about $3 delivered ....you can buy the syringe tips from them too).
My resistance to smd has been that it's a little confusing. How many different sizes of SMD exist? The costs aspect I like, but from the little I've done, it's a bit fiddly.
I think also for those that build and sell their pedals, aside from digital stuff there is an undeserved stigma attached to SMD construction that guitarists think it doesn't sound as good. Not really a big selling point for a boutique builder.
Quote from: tiges_ tendres on December 10, 2010, 01:09:17 PM
Not really a big selling point for a boutique builder.
Yeah, that's true. Does anyone have a link to how to work with the stuff? Solder paste, hot air iron etc? My eyes are shot to the point where I work with a magnifier anyway so bumping it up a notch might not be difficult. Those itty-bitty little parts though...
I'm with the perf/vero guys. I don't really have a reasonable location in which to perform etchings (small apartment, iffy ventilation, etc.), so I generally go the perf/vero route.
Quote from: Gordo on December 10, 2010, 01:37:25 PM
Quote from: tiges_ tendres on December 10, 2010, 01:09:17 PM
Not really a big selling point for a boutique builder.
Yeah, that's true. Does anyone have a link to how to work with the stuff? Solder paste, hot air iron etc? My eyes are shot to the point where I work with a magnifier anyway so bumping it up a notch might not be difficult. Those itty-bitty little parts though...
spark fun elctronics has some great tutorials on working with smd. I use a standard soldering station and solder. Paste is for automated work. An air station is good if you need to remove ICs.
why o SMD...no GE-transistors...just kidding....my main complaint would be it's so much harder to modify/"cut and paste" on an allready stuffed board...I've done years and years of SMD board repairs and have no problem soldering the little buggers(including 128pin processors), but for our purposes I dont see the point..our circuits are small and simple ..and they look silly on a smaller than a stamp-boards...and beside, I like legs.. ;D
J
Quote from: Gordo on December 10, 2010, 01:37:25 PM
My eyes are shot to the point where I work with a magnifier anyway so bumping it up a notch might not be difficult. Those itty-bitty little parts though...
If your eyes are starting to fail (mine are!) ...then it's likely your hand isn't as steady as it was (mine isn't!)....and contrary to what you might think SMD can be easier ....but you'd need to go the solder paste route - then capillary action becomes your best buddy!
Basically dispense a tiny bit of paste onto the PCB pad for each component location (like I say I use a pneumatic paste dispenser & a desktop mounted illuminated magnifiying glass)...plop your components on (they don't have to align that well)....slap the board in a cheap benchtop kitchen oven (should have a fan - and needs to be dedicated for your hobby ....don't cook stuff in their too!), turn it on....after about 90 seconds, marvel at all the components self aligning themselves as the solder paste flows.
Remove, & be amazed at how everything aligned so well.
The oven temperature is meant to follow a temperature 'profile', and when I first began, I made sure I monitored the temperature with a thermocouple...into a DVM (with temp capabilities) so I could manually control the temperature to mimic the desired 'temperature profile' but after a while I decided that it was a load of old bollocks & now just watch for the solder to flow after about 90 seconds!
Type 1206 SMD resistors & caps are not
that small....easy enough to handle with the right kit (good pair of tweezers)
Never did a SMD thing, but it looks to me that the difficult part woud be making the PCB! Tighter tolerances... Iron-on transfer methods aren´t too precise (PnP, magazine paper, etc etc)... How do you small people (err, I mean SMD people) make the PCB´s?
Quote from: Morocotopo on December 10, 2010, 03:00:30 PM
Never did a SMD thing, but it looks to me that the difficult part woud be making the PCB! Tighter tolerances... Iron-on transfer methods aren´t too precise (PnP, magazine paper, etc etc)... How do you small people (err, I mean SMD people) make the PCB´s?
I leave irons to my wife - never touch the things ...I don't understand them (do you find yourself straying onto shopping channels when making PCBs this way?)
Eagle->laser printer-> homemade UV box (pre sensitized board) ->caustic soda->ferric chloride .... Job done (I can work down to 0.65mm pitch.....0.5mm pitch is just taking the p1ss)
Do you SMD guys use a conformal coating or tin plating on your boards?
I have no resistance to SMD.
In fact I would really like to learn how to solder those little buggers properly and save money on parts and high speed bits.
I have seen some serious SMD kits for not alot of cash on the bay.
Aside from the fact that most modern designs utilize SMD components,I would like to make something cool that would fit in my guitar cavity without extra routing or drilling.
I have worked on both through-hole and SMD and one disadvantage of SMD for small components that has not been mentioned is the lack of strain relief. If you flex a through-hole board, nothing happens because the leads bend. If you flex an SMD board, devices lose contact or fall off. Leadless components (passives and leadless IC's) do not work very well over the temperature range you would expect to see as a touring musician. As a studio queen, they may be OK. Gullwing devices are generally OK. Over the temperature range, the temperature coefficient of the circuit board is much larger than the ceramic components. The most important thing to design for is abuse and they do not tolerate much of it. Quite often you get intermittent connections that work some of the time but are simply pushed together with a fractured solder connection. Through hole may have this problem, but it would be the quality of the solder joint, not the fundamental design that is at fault.
I have an old board with some SMD to get some practice soldering, but I haven't really worked with SMD yet. It would increase the stuff I would consider working on.
With SMD I guess you could still use vero, but it seems more limiting to the point that you're almost forced into etching a PCB. With through hole parts, you can use perf, vero, or a PCB.
For those using solder paste and an oven - what temperature is used, and do you ever have thermal damage to any components?
Quote from: Electron Tornado on December 10, 2010, 09:20:11 PM
I have an old board with some SMD to get some practice soldering, but I haven't really worked with SMD yet. It would increase the stuff I would consider working on.
With SMD I guess you could still use vero, but it seems more limiting to the point that you're almost forced into etching a PCB. With through hole parts, you can use perf, vero, or a PCB.
For those using solder paste and an oven - what temperature is used, and do you ever have thermal damage to any components?
A lot of SMD components have a temperature vs. time soldering profile as part of their specification. You cannot put a board in an oven and turn it on without killing components or getting cold solder joints. You have to have the oven up to temperature. SMD components are usually soldered using vapour-phase equipment or infrared ovens with a conveyor that moves the board past certain temperature spots with a defined temp vs. time profile. For the individual experimenter, it is better to solder the parts using a fine-point iron.
It's all about the aesthetic, I find a well laid out, populated through hole board a thing of beauty, a mini piece of architecture. a miniature cityscape. I don't get the same buzz from a SMD board, impressive but rather plain and boring by comparison.
Found this tutorial helpful on the road to SMD work.
http://tangentsoft.net/elec/movies/tt03.html
dave
call me a dinosaur. i want my tone flowing through large bits of metal wherever possible. someone could show me 500 pages of data proving why tiny parts cannot electronically be inferior to larger components, my old guy brain still wants to believe.
a good friend of mine built two versions of the same popular OD pedal . one used small parts , the other used amplifier sized caps, wire, etc.
guess which one sounded bigger and better?
why does zvex avoid opamps for signal path wherever possible?
jack orman told me years ago that caps of different construction could not possibly sound any different from each other. my ears told me a different story in tightly controlled (ear)testing.
signed,
the 50 year old.
Quote from: amptramp on December 10, 2010, 09:30:18 PM
Quote from: Electron Tornado on December 10, 2010, 09:20:11 PM
I have an old board with some SMD to get some practice soldering, but I haven't really worked with SMD yet. It would increase the stuff I would consider working on.
With SMD I guess you could still use vero, but it seems more limiting to the point that you're almost forced into etching a PCB. With through hole parts, you can use perf, vero, or a PCB.
For those using solder paste and an oven - what temperature is used, and do you ever have thermal damage to any components?
A lot of SMD components have a temperature vs. time soldering profile as part of their specification. You cannot put a board in an oven and turn it on without killing components or getting cold solder joints. You have to have the oven up to temperature. SMD components are usually soldered using vapour-phase equipment or infrared ovens with a conveyor that moves the board past certain temperature spots with a defined temp vs. time profile. For the individual experimenter, it is better to solder the parts using a fine-point iron.
Like I say, I initially used a thermocouple in sa bog standard bench top kitchen mini (pizza) oven .....I'd try to ramp the temperature up in accordance with the profile. (bit of a faff, adjusting the oven on/off switch, opening the door to vent off extra heat etc!). But now I set the temp to about 190C, turn it on & watch the solder reflow at about 180C (takes a couple of minutes to get to this heat).....give it about 20-30 seconds to reflow, then open the door.
Whilst I concur, this would not be up to commercial standards, but I've had no component failure or bad joints arising from this method (a couple of dry joints where I hadn't sipensed enough paste....but they're easy to spot)
Quote from: joegagan on December 11, 2010, 06:01:29 AM
call me a dinosaur. i want my tone flowing through large bits of metal wherever possible. someone could show me 500 pages of data proving why tiny parts cannot electronically be inferior to larger components, my old guy brain still wants to believe.
a good friend of mine built two versions of the same popular OD pedal . one used small parts , the other used amplifier sized caps, wire, etc.
guess which one sounded bigger and better?
why does zvex avoid opamps for signal path wherever possible?
jack orman told me years ago that caps of different construction could not possibly sound any different from each other. my ears told me a different story in tightly controlled (ear)testing.
signed,
the 50 year old.
Did you measure all the part values before hand and make sure they matched?
Thanks to both amptramp and Gurner for the replies. I'll have to try both methods with a defunct PCB with some SMD parts on it.
Making a PCB for a project using SMD would be a bit of a challenge to get pads small enough and close enough, and making sure to get a etch resistant that is consistent and reliable.
The reason I'm not interested in SMD is because I'm not interested in using PCBs for hobby builds. I prefer perf so that puts me in the "no SMD" camp by definition. Otherwise I don't have much of an opinion about it one way or another.
That's exactly my position Doug.
Thinking about it I'm not sure there is much actual resistance to it, it's more just the case that for hobbyists it doesn't really offer any advantages. I've yet to see a project anywhere, not just here, that couldn't just as easily be built using through hole. The only thing that tempts me to use it is the Spin FV1 chip, but even then I'd probably just use an SMD to DIP converter and do everything else through hole.
quote, by doug:
Did you measure all the part values before hand and make sure they matched?
if you are referring to the OD my friend made, i am not sure. he is pretty scientific, but i don't know for sure. also, the well documented effect of the expectation affecting one's perception could certainly come into play. i did not hear these two pedals myself, this was related to me verbally.
as far as my own cap testing , it is admittedly haphazard, but the apparent tone difference has occurred enough over a 10 yr period, i believe i can trust if for my own beliefs.
Quote from: joegagan on December 11, 2010, 06:01:29 AM
why does zvex avoid opamps for signal path wherever possible?
Knowing zvex, it's because then he'd have fewer SHOs in there, and everyone knows the more SHOs the better the pedal
hayyyyoooo
Quote from: joegagan on December 12, 2010, 09:22:49 AM
as far as my own cap testing , it is admittedly haphazard, but the apparent tone difference has occurred enough over a 10 yr period, i believe i can trust if for my own beliefs.
I had pretty much sold myself on using high voltage ceramics instead of silver micas in amps. Then just yesterday I subbed a silver mica for a ceramic and much preferred it. In the end I use what I have on my bench that sounds the best. I don't have an LCR meter so I can't really measure them accurately to check for differences in values due to tolerance. I don't know what the reason is for the sonic differences I hear. So I don't make generalizations anymore about "this type vs. that type". I just use what I have on hand that sounds best.
QuoteI had pretty much sold myself on using high voltage ceramics instead of silver micas in amps.
There was a really good discussion over at Music Electronics Forums that hashed out the ceramic cap thing. Basically breaking down the different grades of ceramic caps (I didn't know there were grades of ceramic caps until I read this) and how some are better for amps than others. May be worth the read. Now that I'm stocking up on parts, I need to go back and re-read it.
Just a thought.....if you put a big splosh of solder paste on the pad/lead junction of a through hole board, couldn't you then flow the paste in an oven a la SMD? Isn't that the best of both worlds, given that the uber-miniaturisation of SMD doesn't seem to be a big plus point for everybody?
Quote from: amptramp on December 10, 2010, 07:38:22 PM
I have worked on both through-hole and SMD and one disadvantage of SMD for small components that has not been mentioned is the lack of strain relief. If you flex a through-hole board, nothing happens because the leads bend. If you flex an SMD board, devices lose contact or fall off. Leadless components (passives and leadless IC's) do not work very well over the temperature range you would expect to see as a touring musician. As a studio queen, they may be OK. Gullwing devices are generally OK. Over the temperature range, the temperature coefficient of the circuit board is much larger than the ceramic components. The most important thing to design for is abuse and they do not tolerate much of it. Quite often you get intermittent connections that work some of the time but are simply pushed together with a fractured solder connection. Through hole may have this problem, but it would be the quality of the solder joint, not the fundamental design that is at fault.
Excellent points! These exact points were told to me by a designer that uses smd with advanced degrees in engineering he stated simply don't put parts near the jacks (input/output/power) which is where a huge manufacturer makes their mistakes.
The best pro point for smd, that I can see is you can fit a lot of stuff in a small package.
That being said I suggest making the same exact pedal with smd, 1/8 watt through hole, 1/4 watt through hole and 1/2 watt through hole and tell me if you hear the difference.
I did this with an over drive pedal and the difference made smd a "no sale" to me.
Smd would probably be better suited to applications other than OD so perhaps modulation based effects or tuners smd would be fine.
Funny how it all seems to be about the ease of build, size or cost.....what about the tone ?
IPods are cool but I dont want my rig to sound like one but I play out and dont just build these things...got to use them in the real world.
It comes down to the impression it leaves on others in the live application, imho.
I've always been taught that solder is not a mechanical connection in and of itself. It is intended purely as an electrical connection. So I wonder how SMD gets away with "breaking the rules".
Quote from: markeebee on December 13, 2010, 09:45:06 AM
Just a thought.....if you put a big splosh of solder paste on the pad/lead junction of a through hole board, couldn't you then flow the paste in an oven a la SMD? Isn't that the best of both worlds, given that the uber-miniaturisation of SMD doesn't seem to be a big plus point for everybody?
Ah yes. That's reflow soldering. I should have known that.
why do we gotta get all hung up on the rules , man? can't we all just do our own thing and hang out in the park like the old days?
:icon_mrgreen: :icon_mad: :P ::) ???
Quote from: joegagan on December 13, 2010, 03:53:14 PM
why do we gotta get all hung up on the rules , man? can't we all just do our own thing and hang out in the park like the old days?
:icon_mrgreen: :icon_mad: :P ::) ???
The parks are much smaller nowadays, so SMD techniques are essential if you want a decent go on the swings.
Quote from: DougH on December 13, 2010, 11:00:59 AM
I've always been taught that solder is not a mechanical connection in and of itself. It is intended purely as an electrical connection. So I wonder how SMD gets away with "breaking the rules".
You should see what happens when you put parts on both sides of the board - you attach one side by vapour phase soldering then flip the board over and the surface tension of the solder is supposed to hold the parts on the board even when they are facing down as you solder parts on the other side. Basically, the parts are so light that there is very little strength needed.
Quote from: amptramp on December 13, 2010, 05:55:05 PM
Quote from: DougH on December 13, 2010, 11:00:59 AM
I've always been taught that solder is not a mechanical connection in and of itself. It is intended purely as an electrical connection. So I wonder how SMD gets away with "breaking the rules".
You should see what happens when you put parts on both sides of the board - you attach one side by vapour phase soldering then flip the board over and the surface tension of the solder is supposed to hold the parts on the board even when they are facing down as you solder parts on the other side. Basically, the parts are so light that there is very little strength needed.
Having never ventured into double sided SMD, I could be wrong here - but isn't that when they use glue (cream) on SMD components .....ie for flipping the board over & not having the components fall off?
Quote from: DougH on December 13, 2010, 11:00:59 AM
I've always been taught that solder is not a mechanical connection in and of itself. It is intended purely as an electrical connection. So I wonder how SMD gets away with "breaking the rules".
I don't understand what you mean Doug...
there is diffusion (ion migration) going on at junction.
http://www.aws.org/wj/supplement/sangha/sangha.html
N.B. Some SMD work is/swas done by holding the component in place with a dot of epoxy before soldering. When this is/was done, later soldering didn't move the part.
Personally, I use through-hole stuff because I find it easier to work with. BUT, if I need to make something small, or to use something which is only available in SMD, then I'll use SMD.
For those interested in doing SMD, though, I just stumbled across THIS (http://www.engadget.com/2006/03/07/how-to-make-a-surface-mount-soldering-iron/), which you might find interesting/useful.
Gabriel
Quote from: frank_p on December 13, 2010, 08:25:54 PM
Quote from: DougH on December 13, 2010, 11:00:59 AM
I've always been taught that solder is not a mechanical connection in and of itself. It is intended purely as an electrical connection. So I wonder how SMD gets away with "breaking the rules".
I don't understand what you mean Doug...
there is diffusion (ion migration) going on at junction.
http://www.aws.org/wj/supplement/sangha/sangha.html
Is that the right link? That paper talks about diffusion brazing of copper/tin joints in a nuclear environment at temperatures/pressures that are not at all representative of electronics soldering.
Quote from: defaced on December 13, 2010, 11:09:38 PM
Quote from: frank_p on December 13, 2010, 08:25:54 PM
Quote from: DougH on December 13, 2010, 11:00:59 AM
I've always been taught that solder is not a mechanical connection in and of itself. It is intended purely as an electrical connection. So I wonder how SMD gets away with "breaking the rules".
I don't understand what you mean Doug...
there is diffusion (ion migration) going on at junction.
http://www.aws.org/wj/supplement/sangha/sangha.html
Is that the right link? That paper talks about diffusion brazing of copper/tin joints in a nuclear environment at temperatures/pressures that are not at all representative of electronics soldering.
I was searching broadly microscope shots where we could see a diffusion layer. This might not be the same temperature and context of use but I tought that in * general brazing process* there is this layer and it provides a good mechanical bonding. Not just good electrical contact. Here are *macroscopic* views in a more appropriate context tthat show where cracking happens. I have *a belief* that brazing is a pretty good mechanical joint even at the *electronic soldering* temperatures.
http://www.espec.co.jp/english/tech-info/field_report/2-1/detail2-1.html
Cu3Sn is the closest phase layer there is near the Cu layer, then Cu6Sn5. Those intermetallic phases start at 200 deg. C. on the phase diagram I have just under my nose. Go up at 350 and you can have 5 different phases coexisting with each other.
http://www.metallurgy.nist.gov/phase/solder/cusn.html
The diagram shows that copper is soluble in tin at low temperatures.
CuPb phase diagram:
http://www.metallurgy.nist.gov/phase/solder/cupb.html
For your soldering wire:
http://www.metallurgy.nist.gov/phase/solder/pbsn.html
So this intermetallic layer DO exist at *our 350 deg.* temperature (and by extent are part of the mechanical structure of the bond). I doubt that the pad could even be wettable if one of those phases could not occur, but of course I may be wrong.
Quote from: Gurner on December 10, 2010, 02:49:09 PM
turn it on....after about 90 seconds, marvel at all the components self aligning themselves as the solder paste flows.
Remove, & be amazed at how everything aligned so well.
Hmmm, you've got my interest now...
QuoteI was searching broadly microscope shots where we could see a diffusion layer. This might not be the same temperature and context of use but I tought that in * general brazing process* there is this layer and it provides a good mechanical bonding. Not just good electrical contact. Here are *macroscopic* views in a more appropriate context tthat show where cracking happens. I have *a belief* that brazing is a pretty good mechanical joint even at the *electronic soldering* temperatures.
I'll gather that Doug's comment is that you shouldn't rely on the mechanical properties of the joint for support of the component. Yes, brazed and soldered joint have mechanical properties. There are even test in welding code documents on how to test these joints for procedure and operator qualification. I bet you can find ASTM codes that outline it too. Typical brazed structural joints have strengths in the vecinity of 90ksi. That's 90,000 psi. That's more than most structural welds performed, which are around 70 ksi.
Assuming you're working with eutectic solder, which melts/solidifies at ~175c, the Cu-Sn phase diagram at that temp shows four possible phases. However, the copper never melts. Phase diagrams shows what happens when you take an alloy from melting and cool it under equilibrium conditions to whatever temperature indicated. It says nothing about when you take a solid (Cu) and a liquid (Pb&Sn) and warm it up. Thus, no intermetallic phase can be formed during our soldering operations (which isn't necessary the only source of mechanical strength).
The diffusion part of the process mentioned in that paper is caused by time, temperature, pressure, and alloys. If you remove one of those, namely time and pressure in our case, diffusion does not take place.
The solder cracking paper is discussing what happens in the solder joint itself, and the addition of elements to the solder which form intermetallics within the joint - not forintermetallics between the joint and the base metal - to prevent cracking. It's a grain size issue, same thing happens in welds, particularly with ferritic stainless steels.
Here's an interesting link about using solder paste with SMD in a toaster oven!
http://www.seattlerobotics.org/encoder/200006/oven_art.htm
Heres a nice little hands on demo using the minimum of tools to do a great job.
http://www.youtube.com/watch?v=0OIMmQkAuDQ&feature=related
Tweezers can be used to place the components and a cheap gas hot air iron from maplins is what i use instead of the expensive soldering iron and pre heater in the vid.
I'm tempted to go to SMD, just because it's a different bunch of skills to learn and therefore might be interesting and rewarding.
Now I'm guessing, but on a normal stompbox size PCB I might save 10 minutes in production time? And maybe a quid in components?
So if I make 30 boxes a year, that's a saving of about 2.5 hours and thirty quid? But I'd need to stock up with SMD components and buy a hot air iron.
If I was only interested because of the potential savings, I don't think it stacks up.
Well, you can fit more in a box, that for me is the biggest benefit
Yeah depending on what you build i can see that either getting more in a box or being able to use a smaller box is an advantage, but for a lot of pedals through hole is small enough and things like the number of controls dictate the size of the box more than the size of the board does.
I'd agree with Mr Bee, for DIY builders the potential savings aren't that big, and through hole componets are cheap enough to start with. For most pedals the cost of the components you'd convert to SMD is only a small proportion of the total cost of the pedal, the off board hardware makes up the vast majority of the cost so per pedal, or for small amounts of pedals, the saving's not significant.
As this is esentially a leasure activity, I don't see any advantage to saving time.
You don't need hot air to solder SMD. This is how I do mine and it's very very easy and I don't need an extra tool on my bench. http://www.sparkfun.com/tutorials/101 (http://www.sparkfun.com/tutorials/101)
That looks to me like a recipe for frying your board and components.. but I'll learn this soon enough as I will probably do the same soon. :icon_rolleyes:
Quote from: Gurner on December 13, 2010, 03:58:08 PM
Quote from: joegagan on December 13, 2010, 03:53:14 PM
why do we gotta get all hung up on the rules , man? can't we all just do our own thing and hang out in the park like the old days?
:icon_mrgreen: :icon_mad: :P ::) ???
The parks are much smaller nowadays, so SMD techniques are essential if you want a decent go on the swings.
Just make sure you epoxy your butt to the swing and you'll be okay.
Quote from: ~arph on December 16, 2010, 08:47:37 AM
That looks to me like a recipe for frying your board and components.. but I'll learn this soon enough as I will probably do the same soon. :icon_rolleyes:
Working fast is an important thing, so is a very hot iron. Funny, I think the same thing about hot air and ovens. There's examples on that site where the technique with a hot air station de-laminated the FR-4. The whole hot air/oven thing just seems totally counter intuitive to what I've been taught and experienced, but hey, it obviously works because cause that's how it's being done. I think the important point is that as long as you control the max temperature and the time spent up at elevated (melting) temperatures, you can use whatever heating device you want.
- I'll gather that Doug's comment is that you shouldn't rely on the mechanical properties of the joint for support of the component. Yes, brazed and soldered joint have mechanical properties.
Don't know why I didn't hear it that way... What I understand now, is that it is not a good practice to count on those for holding everything: that's the PCB's job.
I understand the point of view now. For brazing teeth on endmills : it's not the same *preoccupation* than securing a chip to the copper layer. A similar science might be behind, but the goals are not the same.
- The diffusion part of the process mentioned in that paper is caused by time, temperature, pressure, and alloys.
Yes
- If you remove one of those, namely time and pressure in our case, diffusion does not take place.
I am not sure that you have to melt the copper to have ion diffusion of copper into the brazing alloy. The copper becomes soluble, it does not melt completely. In brasing, the base metal never melts anyways. And the interface exists. If the interface of the copper and the tin solution exist at the eutectic point then the copper can become fluid in the tin since the eutectic point is the condition at which two (or more) metals can begin to coexist in liquid form.
- Assuming you're working with eutectic solder, which melts/solidifies at ~175c, the Cu-Sn phase diagram at that temp shows four possible phases. However, the copper never melts. Phase diagrams shows what happens when you take an alloy from melting and cool it under equilibrium conditions to whatever temperature indicated.
Yes, you are describing a normal way of forming the alloys crystals from the liquid alloy. The eutectic is the lowest temperature where there was alloy in liquid form while cooling down. This is the standard way of describing the phase diagrams.
- It says nothing about when you take a solid (Cu) and a liquid (Pb&Sn) and warm it up.
It says at what temperature some fluid alloy can exist at the interface of the solid metals phases at equilibrium temperature. Because they are in contact with each other at the interface copper is soluble in Tin. It does not say that copper melts by itself.
- Thus, no intermetallic phase can be formed during our soldering operations.
Their presence is not to the advantage of the solder if the diffusion layer is too big : mechanical or electrical wise : these alloy phases seems unwanted and a problem mainly in Pb free solder.
http://www.metolit.by/imc_ysb/txt38_0.php
Scroll down to (the page is pretty long) :
EVOLUTION OF MICROSTRUCTURE IN THE BOUNDARY OF SOLDERED JOINT AFTER THERMAL INFLUENCE
The paper talks about annealing a SnAG/Cu joint at different temperatures and for different lapses of time. OK, OK... there is some temperature and time involved, but not THAT high for both.
- The solder cracking paper is discussing what happens in the solder joint itself, and the addition of elements to the solder which form intermetallics within the joint - not forintermetallics between the joint and the base metal - to prevent cracking.
It's a grain size issue, same thing happens in welds, particularly with ferritic stainless steels.
http://www.absoluteastronomy.com/topics/Solder
Search for section :
Intermetallics in solders
Also:
http://www.dfrsolutions.com/uploads/publications/2001_IEEE_Kinetics_IM_Alloys.pdf
*While the frequency of use of no-Pb solder continues to
increase, electronic solder joints are still generally fabricated
using Pb-Sn eutectic solder reflowed in contact with the
metallic surfaces to be joined. Upon reflow new intermetallic
alloys grow at the interface solder/pad and ensure bonding.
For instance for Cu metallizations, Cu6Sn5 with some Cu3Sn
forms at the Sn/Cu interface [1,2,3]. If these alloy layers are
too thick, they have deleterious effects on the mechanical
reliability of the joints [4]. Therefore, over the years, the
composition of electronic leads has changed from a single
metal, usually Cu, to multi-layered structures with two or
more metallic layers stacked on top of each other. A thin
coating of a noble metal such as Au or Pd is frequently used to protect the surface from oxidation, while a second layer, commonly Ni, is used as a diffusion barrier to prevent the Cu
underneath it from interacting with solder. A number of
investigators have shown that Ni/solder intermetallics grow
more slowly than Cu/solder intermetallics during reflow
[5,6,7].*
------------------------------------------------------------------------------------------------------------------------------
http://en.wikipedia.org/wiki/Brazing
*Interaction with base metals
For successful wetting, the base metal has to be at least partially soluble in at least one component of the brazing alloy. The molten alloy therefore tends to attack the base metal and dissolve it, slightly change its composition in process. The composition change is reflected in the change of the alloy's melting point and the corresponding change of fluidity. For example, some alloys dissolve both silver and copper; dissolved silver lowers their melting point and increases fluidity, copper has the opposite effect.
The melting point change can be exploited. As the remelt temperature can be increased by enriching the alloy with dissolved base metal, step brazing using the same braze can be possible.
Alloys that do not significantly attack the base metals are more suitable for brazing thin sections.
Nonhomogenous microstructure of the braze may cause non-uniform melting and localized erosions of the base metal.*
-----------------------------------------------------------------------------------------------
It seems diffusion is necessary for bonding but not too much of it.
Using non-trough holes SMD components and lead free solder seems much less rugged than leaded ones and using standard Pb containing solder.
Are people still using gold to prevent oxidation on component leads? I thought the experiences we and everyone else had on spacecraft would have deep-sixed that long ago. We had 2N2222A transistors with leads that were gold over kovar with the leads rusting away due to the porous gold layer forming an electrolytic cell with the kovar. Add to that, the gold forms intermetallic compounds known as "purple plague" because of its appearance.
I don't foresee much need for SMD in stompboxes except where components like microcontrollers may only be available in SMD. The main savings is not having to drill holes in the board as holes are expensive - the board wears down drill bits quickly, especially with epoxy-glass boards.
I did alot of SMD back in the late 80s while I was working at JPL.
We soldered all that by hand with the aid of a microscope (the typical one you might find in a high school lab).
I had no problems with it, but it does take some time getting used to.
We didn't have hot air irons, just really small soldering iron tips. Although I modified mine to heat each side of an SMD component at the same time.
Would I build pedals, etc. with SMD stuff today. Maybe if I had a microscope. Eyes aren't what they used to be.
Yeah, we have a microscope in our lab too. Not for doing smd but for inspecting boards and other hw, and doing detailed work. One of my issues with doing anything super tiny anymore is the eyesight.
continuing last post (on the phone)- I don't see a lot of practical use for smd in analog stompboxery. Seems to be an attitude of let's do stuff just to do it. Fiine for learning but I don't usually grab a hammer from the toolbox unless I really need one.
QuoteFor successful wetting, the base metal has to be at least partially soluble in at least one component of the brazing alloy. The molten alloy therefore tends to attack the base metal and dissolve it, slightly change its composition in process. The composition change is reflected in the change of the alloy's melting point and the corresponding change of fluidity. For example, some alloys dissolve both silver and copper; dissolved silver lowers their melting point and increases fluidity, copper has the opposite effect.
and also from Wiki
QuoteLead-tin solder layers on copper leads can form copper-tin intermetallic layers; the solder alloy is then locally depleted of tin and form a lead-rich layer. The Sn-Cu intermetallics then can get exposed to oxidation, resulting in impaired solderability.[78]
...
# Cu6Sn5 – common on solder-copper interface, forms preferentially when excess of tin is available; in presence of nickel (Cu,Ni)6Sn5 compound can be formed
# Cu3Sn – common on solder-copper interface, forms preferentially when excess of copper is available, more thermally stable than Cu6Sn5, often present when higher-temperature soldering occurred
Ok, intermetallics are formed because of some diffusion/solubility between the solid Cu and liquid Sn/Pb mixture. I don't fully understand how, they kinda skipped over that stuff in my phase diagrams class apparently, and I was more interested in focusing on welding metallurgy and arc physics than brazing/soldering/solid state joining processes. Now the phrasing of the notes about the different intermetallics makes me want to know more about the particulars of what's happening.
Just out of curiosity, what's your background? I gather you're probably a welding engineer or a really practical metallurgist or something of that ilk.
Quote from: defaced on December 17, 2010, 02:23:17 PM
Just out of curiosity, what's your background? I gather you're probably a welding engineer or a really practical metallurgist or something of that ilk.
I did Mech. Eng.. But the reason why I was relatively interested in that kind of stuff is because I worked in R&D for securing blades on hi-speed wood shaping tools for industrial cutting machines. I had to do some resistance testings protocols and a bit of microscope inspecting on the carbide brazings with a lab assistant at the university. The guy was autistic, but for I don't know for what reason, he had memorised all the metallurgy encyclopedias he had in his lab and he could identify and calculate the % of each phases of metal samples just by looking rapidly in the microscope. Then he would talk endlessly about grains while playing in his nose and scratching his balls :icon_eek: . But that was 10 years ago... and all I remember about brazing is that the science behind is quite complicated and mysterious.