Surface Mount Plunge - what should I know?

[Kevin Mitchell]

I'm working on at least two project where I've toyed with the idea of using 0805 resistors. I figured those shouldn't be too difficult to hand solder as long as there's adequate pad space provided. I'm drawn to SMD because it allows for a tight layout with easier track routing. But it's not something I've worked with yet.

I think I'm going to need flux. Applying flux would be more sufficient than adding solder if something needs a reflow. Any suggestions on what kind?

I have a hot air station that I've never really used - it was given to me. What temp would be an average to work with? I guess I'd only need it if I'm using solder paste or removing a surface mount IC and the temp would depend on what I'm trying to melt - without damaging any parts or the board itself.

I'm sure I'll think more questions. These were my first thoughts as I know I'll have to invest in some more tools.
Just placed a Tayda order and included like 4 different kind of tweezers

[marcelomd]

Hot air: Same as  soldering iron, I think. About 350C. I used 400C to desolder stuff, but never to solder. Heat the work area first. Don't hover too long over a single spot or you'll burn the board.

0805 is more about eyesight than skill. Super easy technique is:
- Put a small blob of solder on a pad;
- With tweezers, align the part. Either on the side or on top of the solder;
- Melt the pad and slide the part to the final place;
- Solder the other pad;
- Touch up the first pad.
I like to do one side first for all the parts, then come around and do the other side. Don't want to overheat anything.

I had good results with 1mm rosin core. No extra flux.

[nickcordle]

0805 is awesome 

Flux content of the solder seems to matter a lot but when it's lower, I've had great results out of a Kester 2331-ZX water soluble pen.  I'm in the habit now of just marking up the whole board at the start.  The scrub at the end is not optional, but worth it.  I went through a few "no-clean" types before this and had a few weird glitchy things happen which I choose to blame on a tiny bit of extra conductivity.  (probably user error, but hey ...)

Consider a magnifying lamp if you don't have one?  I have one that's 4x I think, clamps onto the desk, swivels around ... my eyesight isn't great and 0805 is not a problem -at all- with a little magnification.

[soggybag]

I did a couple eurorack kits with surface mount parts it was easier than I thought it would be. Get some teweezers and some liquid flux.

- overall the process was easier than expected.
- a magnifier is helpful
- watch a couple videos, there are a few techniques that are useful for certain parts
- get a little bowl or ashtray to hold the part you're working with until you need it
- I threw away more garbage for a handful of parts smaller than a grain of rice, which was really disappointing.

I used a regular tip on my soldering iron. If you can find a fine point tip that would be good.

The markings on some parts is different, for example one-amps and diodes keep your eye on these and double check the orientation.

[imJonWain]

0805 stuff is pretty easy to deal with once you get the hang of it.  I personally like using a "hoof" type tip for SMD work.  Then just good tweezers and decent flux.  I like quickchip flux for no real reason.  Hot air gun makes rework easier but you don't "need" one.  I prefer fork style tips for removing individual parts but not al irons have that option. 

[deadastronaut]

following as a smd noob too:

i just bought a ''smd practice board pcb''  which comes with some components of varying sizes as i also felt like dipping my toe into this world of tiny, fiddly, lil bstd bits..so i figured a practice board would be ideal...

mrs astro bought me a new solder station with hot air too so i may as well try it.....

do you guys use hot air?..if so have you ever killed a component with hot air?

what flux?
what paste?

[bushidov]

I've been hand soldering (and de-soldering) SMD components now for about 10 years now (part of my day job). As many have said, it's mostly about eye-sight and a semi-steady hand. As of what we use at work, for solder, we use:
https://www.amazon.com/gp/product/B0032UVNJW

We have two old Hakko 703 digital solder/de-solder rework stations and one heat-gun station. Typically, I solder and de-solder at 685 F (363 C) and typically don't use the heat gun much. As of de-soldering, if it's a two contact part, like an 0805 capacitor, resistor, ferrite chip bead, etc, I just use the solder gun and de-solder gun as a set of heated tweezers and apply to both sides of the parts and lift.

Maybe its just where we get our PCBs from, but I rarely burn the boards or lift pads this way. This really only happens where I am doing things like really thin quad flat-packs and I do the "ring around the rosey" de-soldering technique, where I blob solder on all 4 sides and use both the soldering gun and de-soldering gun to heat two opposite sides into liquid and then quickly rotate to the next adjacent sides, and keep doing that. If I let the sides that I move away from cool too quickly, I might lift pads, but once you do this enough, you get the timing down.

As of our heat gun station, I've burned PCBs more often on those, which I why I use the above method when I can, as it rarely turns into anything damaging.

As of killing components, I've killed with the hot-air gun things like GPS receivers like the Telit 869 (https://www.digikey.com/en/products/detail/telit/SL869GNS115T001/5056809), but that's because the heat-gun takes off that metal shielding, which is pretty much impossible to get back on. As of ICs, we use a lot of 74' series logic chips, microcontrollers, and PMICs, and it really hasn't been a problem on any of those. The one warning I will give, though, are SMD LEDs. You don't want your solder gun on them any longer than you have to. If you look under a microscope, you may see that the "housing" for the anode and cathode starts to melt and might push them into each other, causing a short.

As of tweezers, we use these:
https://www.digikey.com/en/products/detail/swanstrom-tools-usa/OO-SAH/10819773

Pricey? A bit, but you buy one and never buy another again. The foam is heat resistant, so when holding a piece in place, the heat doesn't travel up the metal and burn your fingers.

As of flux and paste, I really don't use any because the solder I have has a good amount of rosin in it. I am also hand-soldering too. However, at home, I am about to re-purpose a toaster oven to do SMD soldering, so I will be getting into solder paste with that. I just watched Andreas Spiess's video on this, and feel I am ready to try it:

[Yazoo]

My recommendation would be to grow a nice long thumb nail to hold the parts with while you make your first anchor solder. I go with the advice of putting an initial solder blob on the board to do this. I've tried using tweezers but it's difficult not to shake or twitch and once those parts fly off, they are really hard to find.

[Ripthorn]

Here are some things that I have found useful:

- I use RMA223 no clean flux for IC's. It really helps the solder wick under the pads well
- Get ceramic tipped tweezers. The fine point stainless steel ones have more give and result in more flying parts.
- I use a 2mm hoof style tip for pretty much everything
- An optivisor type thing is very handy, but don't go too much magnification, or you have to be too close to the parts.
- I use a 10x loupe for inspection after soldering when I can get good and close to the board
- I use hot air when removing ICs. For most parts, I just assume that if I am removing the part that I won't be able to salvage it, as I would rather spend a few extra pennies replacing the part than have to spend a bunch of time running down a single bad component.
- 0805 is pretty easy to work with, as are SOT23, SOIC, etc.
- Get fine diameter solder to keep waste down (.015" is great)
- Haven't done paste yet, but working my way there.

[iainpunk]

i don't know much about SMD but i am a proponent of surface mount mains connectors, instead of those through hole ones in use today.
i want to accelerate darwin.

cheers, Iain

[amptramp]

The biggest problem is holding parts down because the surface tension of the solder is greater than the weight of the part.  The solder and flux have to be deposited first, the part positioned where you want it and the heat applied.  You can solder with an iron but it is difficult to hold the device in position because if you solder one side of a resistor and it is firmly attached, as soon as you solder the other side, the heat is transferred and the part is floating again.  In fact, if parts are close enough on a board, soldering one component may liquify the solder of other nearby components.

The benefits of surface mount are:

1. smaller boards.
2. fewer drill holes and drilling is expensive - drilling through glass and resin burns out drills rapidly so you may get manufacturing charges of some amount like a few cents a hole (depending on diameter) but this adds up.
3. ability to get small consistent circuits as needed for UHF frequencies or fast logic edge rates and beyond.
4. The ability to solder everything at once.

Some sort of clamp like a hemostat may be the best idea for holding parts down.  There is not much in the way of audio that requires surface mount or gives any benefit other than cheaper boards.  We had a number of boards manufactured by accurate placement followed by infrared or vapour phase soldering  This is definitely better in a production environment but may not work as well for prototype quantities.

[marcelomd]

On holding parts. Something as simple as this will help.

[Kevin Mitchell]

Wow so many awesome responses!

Okay so here's my shopping list after reviewing the replies and also thinking further about my situation.
An assortment of solder tips
Spool of solder with a lot of flux - such as the Kester 24-6040-0027
A flux pen such as the Kester 2331ZX
A desk magnifier with built in LEDs
An ESD mat so I'm less likely to lose or damage parts


Just got my first round of 0805 resistors. I must have sneezed or something because I'm already missing the three I took out to inspect  . Honestly they're much smaller than I had expected - they look larger when they're actually soldered. Fleas get bigger than these resistors.

Also the one's I had just gotten (2.21M ohms) doesn't have any markings. So if I ever have to measure one to verify it's value, pray for me.

I'll chime in with my first SMD board soon. I may draw up an easy layout to etch a test board. Thanks again everyone!

[marcelomd]

One more thing. Where do you guys store SMD passives?

I was thinking about using these vials:

[R.G.]

Get a bottle of liquid flux. This is rosin dissolved in alcohol to a liquid consistency. Use a Q-tip to swab the whole area. This dries to a sticky coating as the alcohol evaporates. If you're using commercial boards they are usually solder coated on the pads. If it's a home brew board or one without tin/lead plating, touch a well tinned soldering iron to one pad of each component footprint on the board, leaving a whiff of solder on the pad - note: don't leave a mound of solder, it makes what follow more difficult. Place a component with tweezers. The sticky rosin will nearly always hold the component in place until you can touch the soldered pad and stick the part down.
For pre-tin/lead plated boards, you can usually skip the solder-one-pad step before placing. A fluxed pad on a tin-lead board will usually have enough solder to make a tiny joint on the heated pad/component, enough to hold it firmly in place.
When they're all stuck down, solder them all.
If you use solder paste, touch the pads with a toothpick dipped into paste, then place the components. The paste has enough flux to temporarily hold them in place. Then (ab)use a Goodwill toaster oven to flow the solder, watching it carefully for just enough temperature * time.

[Ripthorn]

I use Aidetek boxes for SMD components. A 144 compartment one holds all capacitors and resistors, some transistors and other IC's.

I also recommend a set of multimeter leads for SMD and a set of tweezer multimeter leads. Super handy. Amazon has a set of both for something like $15.

[Kevin Mitchell]

Thanks for chiming in R.G.! That's great to know.

On a somewhat relevant note, is this normal for SMD orders? 

I feel like I'm being punished by the folks at Newark lmao

[deadastronaut]

 

They are doing the organizing for you too....great service lol...

[patrick398]

Thanks for chiming in R.G.! That's great to know.

On a somewhat relevant note, is this normal for SMD orders? 

I feel like I'm being punished by the folks at Newark lmao

Sometimes my through hole caps come in individually sealed plastic bags, like one cap per bag...which is really annoying when you have ordered about 400 each of 10 different values. So much plastic, so little time

[vigilante397]

Somehow I missed this thread when it started. Most of what I would have said has been covered, except that I only recommend hot air for desoldering, I find it finnicky to work with while soldering. I use a cheap ($200) reflow oven for baking my boards and love it. I've seen people modify toaster ovens to do reflow profiles, but didn't want to deal with that.

I use these boxes for component storage, 4 boxes (resistors, caps, semiconductors, and large components) holds everything I need.