A Beginners Guide to Soldering Surface Mount Components

[KL27x]

the physical effect in question is the Marangoni effect, which describes movement of mass under a gradient of surface tension, which in the case of soldering is caused by a thermal gradient.

I'm a scientific type. I like to use exact language. I don't care how conventional it may be for someone famous to inaccurately describe something.

In the case of the protoboard, you're seeing wicking effect. Because the board has no soldermask. Yes, you can move the tip around to avoid reaching reflow temp on areas you don't want to be wetted with solder. You are also moving a huge portion of the surface area (the tip of the iron) in this equation. On a soldermasked board, the entire wettable area of pad will quickly be wetted, and solder has nowhere else to go in order to try to minimize its surface area. Temp gradient has nothing further to say on the matter.

Besides. Have you never seen Dave solder?

[KL27x]

No, I didn't.

The capillary action is over once the surface is wetted. What you're describing is only affecting large areas/plane of copper, or solid metals like in welding/brazing/soldering jewelry. Yes, if there is part of the metal that is not hot enough to liquefy the brazing/soldering material, it will not be able to have any capillary action. Because it's not a liquid.

When you solder a board like OP has posted, the entire pad will be above the melting temp of solder. The entire solder bead will be fluid. And the entire wettable surface will be covered. There are no capillaries left to have capillary action. What determines the amount that sticks with the iron vs what stays on the pad is primarily left to surface tension and gravity. It doesn't matter if the board is on a preheater and set at 350C. Unless you are using tiny tip on large exposed pad/plane, you're not concerned with Italian-dude-phenomenon.

*ok, I was curious and looked. I think you're making a strange connection to even bring it into the thread. Different fluids have different surface tension. They have example of alcohol and water. So what that has to do with solder?  In soldering you have solder and flux, but the flux doesn't mix with the solder. It is not soluble in solder. It just drips off the solder and pools around the edges of the joint. There's no reason for the hotter part of the solder bead to have higher surface tension than the cooler part, as long as the entire bead is molten. Please connect just one dot for me.

[KL27x]

Again, what makes you a bigger expert than the actual subject matter experts, who routinely observe and describe the effect?

Maybe you're starting with a false assumption, here. I have never heard anyone use this Margoni effect in the way you are trying to make a square peg fit a round hole.

For example, where I normally see it is on protoboard with multi-pin pads, or on stripboard. Suppose a 4-pin pad, to which I want to solder something to each end. If I apply the iron to the inside side of the first pin, and then the solder from the opposite side, the solder tends to encroach on the adjacent hole, because it's drawn toward the iron. If instead I apply the iron to the outside side of the pin, and again apply solder from the opposite side, the solder encroachment is reduced, because the solder is, again, drawn toward the iron. (Solder mask isn't really relevant to these things, since they almost never have per-pin solder mask on multi-pin pads, even when they do have solder mask otherwise!)

It's drawn towards the surface area of the iron. Once that filet between pin and iron wicks in, the iron becomes part of the surface area of the bead. The bead naturally wants to make the smallest surface area possible, which now includes all hot enough parts of the pad/pin and soldering iron tip. If you take two soldering iron, one set for 300C and one set for 400C with identical tip shape, and you put one on each side of the pin, what do you think will happen? Do you think the COM of the bead will be pulled towards the hotter iron?

Glass of water/alcohol sitting unmolested is different from solder for other reason, too. Even if flux or a second fluid with a significant evaporation rate was soluble in the solder, the solder bead isn't sitting in a static environment. There is a very hot spot on one end, and heat sinks on the other end. And there are convention currents in the bead. It is going to get mixed up.

[mrpackethead]

Like anything SMT Hand soldering is a set of skills that is learned, but perfected by practice..  there was a time i woudl not have ever dreamed of hand soldering 0402 parts, or 0.4mm pitched IC's..  thats routine and normal.. When i first started, a 1.27mm SOIC seemed 'impossible'.   I'm now doing 0201 parts..

Theres a technique and process for everthing.. the big thing is *never* give up!

[KL27x]

Different temperature = different surface tension

So this is a fact in your mind? And you have researched it to your satisfaction? I find this statement curious.

Wanna test this and show that it's not just ordinary surface tension? Take a cut-off diode lead or similar very straight solid wire. Melt a generous blob of solder onto it -- as much as you can without it dripping off. Cool it off, then brush on some new flux to eliminate the effect of surface oxidation. Secure the wire horizontally so that gravity won't affect the experiment. Now, take your iron (with a small amount of solder as a thermal bridge) and hold it to the wire near the blob, but not close enough to touch it. Wait for the blob to melt, and then wait a bit longer for the heat to build a bit. The blob will then move towards the iron.

Try this. Take the lead and fully coat it with solder, so it's all wetted. Fix it in a vice so it stays perfectly horizontal. Put a solder blob anywhere you want on it, fully melting the solder and lead above melting temp. Let it cool. Now use IR heat on one end or the other to make it move.

[KL27x]

I'm so over your arrogance, KL27x. Be arrogant and stay ignorant if you want. YOU are the one disputing a well-known, commonly-taught fact. I have no obligation to justify myself, and at least I've actually made an effort to research my claims instead of hiding behind condescension.

I'm not hiding anywhere. I think you prefer it if I did. I am not arrogant. When someone says something that is illogical, I sometimes point it out.

You hide behind fancy-pants-phenomenon, apparently without enough understanding to realize it does not support your argument.

[KL27x]

Quote from: KL27x on Today at 12:02:16 PM

Quote
Different temperature = different surface tension


So this is a fact in your mind? And you have researched it to your satisfaction? I find this statement curious.


Again with the arrogance, trying to gaslight me by phrasing me as some kind of delusional kook.

It's not a fact in my mind. It's simply a fact: http://fsz.ifas.ufl.edu/surfacetensionandcapillarity/html/en_tension.htm

Quote from: KL27x on Today at 12:02:16 PM

In general, surface tension decreases when temperature increases because cohesive forces decrease with an increase of molecular thermal activity.  The influence of the surrounding environment is due to the adhesive action liquid molecules have at the interface.

Again, I ask you to connect some dots, here.

IR heating is too diffuse to be of use for this experiment.

This is a thought experiment which is meant to be fairly obvious the expected outcome.

 

I gave you a real-world experiment you can reproduce easily at home, and one that's actually relevant.

And for real world experiment, I already gave you one. You actually believe the hotter iron will pull a solder bead towards it? (COM, btw, is me using acronym for center of mass). You would actually bother doing this if you had two identical irons? Again, I think the outcome will be pretty obvious.

First you claim to be a man of science, then you dismiss the science as "fancy-pants". Fuck off.

Dismissing Margoni effect and not understanding how it is applicable, here, are two different things. I claim the latter. I claim ignorance of your full argument. It does not make sense to me. You make too many assumptions on my understanding of what you know (or what you think you know).

Please, don't take it personally. I could care less.

[KL27x]

Do you doubt a chef about how cooking works just because they can't explain the molecular changes happening in a Maillard reaction?

Wot?

And yes, the outcome in the soldering iron experiment is obvious: the solder would pull towards the hotter iron. (Heck, solder even does that on my 0.4mm chisel tip: it's so thin that the point stays cooler, and so solder actually likes to bead up just above the point, even though the point itself is hot enough to melt the solder.)

I understand how people would think what you do. Probably because people have been saying things like this since the beginning of time. I thought the same thing 10 years ago. But it doesn't hold up to deeper reasoning.

Here's my explanation (excerpted from my reply #24 in this thread, in case you want to read the whole thing):

... In the case of a pointed conical tip, the bead will natural suck up, away from the tip due to larger surface area at the base of the cone. If you consider the total surface area of bead + wettable iron surface, the surface area is smaller when the bead is higher up on the tip...

In case you are not getting it, this essentially means surface tension is beating gravity. I will be happy to dissect it and connect the dots in case you are missing a logical leap, here or there.

[KL27x]

Here is a 1 minute way to see this for yourself. I just did this.

Take 2 wooden Q tips. Sharpen one to a nicely tapered point.

Take the pointy stick and coat it with mineral oil, then put a little drop on and point it straight down. Watch the bead form at the tip. Now, because the surface tension to weight ratio of mineral oil is lower than for molten solder, it WILL actually make it to the tip. But tilt the tip 45 degrees, and watch what happens.

Do the same with unaltered Q-tip.

[nugglix]

Thanks for derailing this way to useful thread. 

[ez24]

   .

[KL27x]

There's no missing logical leap: whether you like it or not, it DOES happen, and I don't need to have some pissant on the internet condescend to me and talk at me like I'm a short-bus child just because YOU refuse to accept that something is true, just because you don't understand it. I don't need to understand it to know that it happens, and there's no reason for me to doubt actual scientists who can explain it.

This is so weird, because I find it irritating when someone directly contradicts me and cites vague stuff that is supposed to explain things, but it doesn't. And I don't know why it is arrogant to question that? Socially erudite, perhaps. Arrogant? You just said you're not a physicist or an expert; you said you did a quick google search, essentially. So why are you offended if I question your reasoning?

there's no reason for me to doubt actual scientists who can explain it.

This part is not clear to me. I don't know why you think actual scientists/physicists (or soldering experts) are using Maragoni effect to explain that solder is drawn towards heat. You keep stating "facts,"  but all you did was link a Wikipedia article on Maragoni effect???

Nobody is disputing the effect there. But there's no temperature gradient here, so not a comparable situation.

If it explains why a liquid bead on an inverted cone will defy gravity and behave just like a soldering iron, all while in absence of a temperature gradient, why do you need to invoke Maragoni effect (which you admit you don't even understand how it furthers your cause) to explain what needs no further explanation? Worse yet, how do you credit the temp gradient and/or Maragoni effect for producing a result that you just stated is going to happen in absence of temp gradient, anyway? If you think the temp gradient between the base of the tip and the point is doing this, you could touch the very tip of the iron onto an ice cube to see if the bead climbs higher. But this is dumb; we know it won't.

*edited, (sorry)

Stop trying to belittle me just because I'm not a physicist

I'm not trying to belittle you. I'm trying to understand what you see or experience or understand (or think you understand; and again, this is not belittling you.. you admit you aren't a physicist and don't seem to have thought things all the way thru, perhaps?) that makes you come to the conclusion you hold so strongly with so little supporting evidence.

I hope this is not overly offensive. People tend to get irritated and defensive when you question their beliefs. But this is soldering we're talking about. Not politics, race, religion. This is pretty close to science.

[KL27x]

As I have stated, I have once upon a time held similar vague belief as you. But at some point I gave it some thought. And I came to a more comprehensive understanding with fewer inconsistencies.

So when someone like you comes along, I have to wonder. Is this me ten years ago? Or am I still missing important pieces of the puzzle?  If I find my understanding is in error, I will be glad to learn something. Hence, I question.

[sasa]

I'm also relatively new to using surface mount. My most useful tool for soldering is a cocktail stick to hold the component onto the board whilst heating with the soldering iron.

Living true! 

I use similar to hold 0805 parts in order to prevent turn over vertically when touch with chisel tip, then drag soldering iron to join and solder to bubble at dedicated end, then it is trivial to solder opposite side...

My favorite way to solder TQFP100 is to use chisel tip as well, scotch tape to fix chip, quite a bit of liquid flux, then make  small blob on top of tip and in one press solder 4 or 5 pins at once. No shorts, no desoldering wick, no overheating...

Thanks to John Gammell, this was (and still is) my favorite video for "Professional SMD soldering":

[KL27x]

Re John Gammel vid, yes this vid changed everything for me, too.

After seeing this vid, I noticed he uses C3 or CF4 CF3 more than any other tip in his drag soldering. He also states in this vid:

"T15-CF3 an amazing multipin drag soldering tip." So when he says this, and he doesn't say this about any other tip, I of course listen and buy it. Then buy all the other CF tips. And they change everything.

*edited for typo.

[mrpackethead]

The right tips are everything. I'm about to put a second iron on my desk so i can have one of each ready to go.

[Old Don]

After soldering multiple SMD diodes to a board you discover that all will be reversed from the desired direction. 

[xani]

After soldering multiple SMD diodes to a board you discover that all will be reversed from the desired direction. 

And after checking one with smd probe tweezers just to be sure you will discover that leads were backward

But hey, at least SMD components dont hurt as much compared to DIPs if you stomp barefooted on them

[tautech]

After soldering multiple SMD diodes to a board you discover that all will be reversed from the desired direction. 

ALWAYS have an orientation maker on the PCB for all polarised parts.
In the overlay or as copper...K, +, dot (pin1) etc. as needed.

[KL27x]

I discovered SOT23 dual diodes. They are about as cheap as they come, even if you only need one of the pair. You will never solder them on backwards. You have a new problem to tackle, though. Whenever you drop a SOT, it lands upside down. but if you use SOT23 transistors, you already have this problem.

[Old Don]

After soldering multiple SMD diodes to a board you discover that all will be reversed from the desired direction. 

ALWAYS have an orientation maker on the PCB for all polarised parts.
In the overlay or as copper...K, +, dot (pin1) etc. as needed.

Do you really look at those things?   

[xani]

Solder one leg then beep it with multimeter.

Solder another and do it again just to avoid any quantum SMD tunnelling (also called "I swear I've already checked that one")

[Southerner]

My favorite way to solder TQFP100 is to use chisel tip as well, scotch tape to fix chip, quite a bit of liquid flux, then make  small blob on top of tip and in one press solder 4 or 5 pins at once. No shorts, no desoldering wick, no overheating...

Thanks to John Gammell, this was (and still is) my favorite video for "Professional SMD soldering":

The video says to use the T15-CF3 tip
https://www.hakkousa.com/products/soldering-iron-tips/t15-series/t15-cf3.html
for drag soldering but the list of irons it fits is pretty small:
Hakko FM-206 3-Port Soldering Station (FM2027 Handpiece)
Hakko FM-204 Soldering Station
Hakko FM-203 Soldering Station
Hakko FX-951 Soldering Station
Hakko FM-202 Soldering System
Hakko FP-102 Soldering Station
Hakko FP-101 Soldering Station

I was hoping it would fit my Chinese 936 clone and the Chinese Aoyou 701A+ rework clone but am not willing to spend $37 usd in the hopes it might fit.  Has anyone used that tip on any of the Chinese clones?

Thank you.

[HobGoblyn]

Hehe I take it the person KL27X is debating with, has had their posts removed   very weird trying to follow thread, but is three years old.

OP has it perfect.  I replaced a camera in friends iphone in December, tiny screw in my tweezers, next second it pings about a foot off the table, onto laminate flooring, never to be found.

First smd repair a couple of weeks ago, 4 port SATA pci xpress card in my PC, port 3 wouldn't work. Looked fine under naked eye, under microscope a capacitor was clearly misusing. I replaced it with an 0805 which was about twice the physical size, took me about 30 mins to solder it in place, had it half over the pads and dragged solder to each side.

Worked perfectly, but trying to place under a microscope, then get iron in place etc, takes some getting used to.

[Southerner]

No idea where you got the idea that removing solder bridges from SMT parts is hard;

I got it from personal experience. Your mileage may vary.