Soldering issue...

[polbit]

Hi everyone, another newbie here!

I haven't used a soldering iron in 20 years, but suddenly I got an urge to start playing with electronics again. I bought a Hakko 936 iron, some nice 60/40 solder, etc., plus some educational kits to play with. Well, I got a hang of a regular solder join pretty fast, however I came across a kit where the board has a mix of normal and huge traces. One of the traces takes 1/4 of the board. And I can't seem to solder anything there. I heat up the board and the leg of a given part for 3-4 seconds, then apply solder, but unless I touch the solder tip itself with the solder, it doesn't want to melt, and it's just a big mess...

So, my question is - is there a trick to doing this right? Should I use a higher temperature? I have been using 600F, and it works fine for normal traces... I'm afraid of keeping the iron on longer, or using a much higher temp...

Thanks!

 

[tunedwolf]

Generally it's not the tip temperature, although it is obviously important that the joint temperature is correct for the type of solder you are using.
I suspect that your problem lies with the tip size, if it is too small, i.e has too low mass or weight if you like, then the board will act as a heat sink for it and cool the joint to well below the optimum soldering temperature.
The tip has to have enough weight to transfer sufficient heat for the required amount of time in order to maintain the joint temperature.

hope this helps
rgds

 

[kchriste]

In addition to the above:
I assume the solder has a flux core. Try the iron at around 700-750F, no more. Make sure the tip is clean and well tinned. Place the tip at the junction of the lead and the trace at an angle that gives maximum contact area with the heavy trace. Feed a little solder between the PCB and the iron. This should aid in heat transfer when it melts. Feed more solder, at the junction of the lead and the trace, once the solder starts to flow.

 

[polbit]

Thanks for quick answers! Well, I will try it at 750F few times, see if that changes anything. I'm just afraid of destroying transistors and diodes, etc. - don't have the touch yet Higher temperature will also burn off the flux faster, therefore I know I need to keep feeding fresh solder at a higher interval, which, taken all together, is just a little more challenging.

My tip is a basic screwdriver type, perfect size for the holes (just a little smaller than your "average" trace). That will be my next thing to try I guess - get a couple of extra tips. I was going to buy some anyway.

As far as keeping the tip clean, I think I am doing a good job - the solder has a flux core, and I make sure to always clean it, then apply a bit of solder to the tip between parts. I'm using the metal shavings thing that Hakko sells, and the sponge once in a while.

 

[Speakerguy]

Most circuit boards use thermals to avoid this type of problem. The only cheap solution is a tip with very high thermal mass and a lot of contact area with the joint, something along the lines of a big chisel tip.

When working with ground planes and copper pours, professional technicians will often use board pre-heaters that sit beneath the PCB and use hot air to heat the entire PCB region to just below the solder melting point. Then the iron tip is used just for the extra amount of heat to make the solder melt at the problem joint. Board pre-heaters can be had for $250 or so new, or you might be able to find a used one much cheaper.

 

[cabala]

I would note that anything above 600F is above almost all rated electronic parts and you're amount of time allowed with heat applied to the lead is greatly reduced. Industry standard pretty much follows NASA standards. Depending on the board's thermal relief designs on vias and through-holes that may be one of your issues. Also organic based flux solder, say 63/37 (something like that) tends to have a lower melting point and flows a lot better on hobby type projects, where you don't have some tools at hand like, a heat bath mentioned above, which heats the whole board up to a stable temperature. Hope this helps, I know soldering can be a pain sometimes.

 

[3v0]

Ideas.

Is the trace clean and bright.

Liquid flux applied to the board prior to soldering can help the heat flow.

Heating the entire board prior to soldering with a blow drier (hair styling) prior to soldering. Do not get it so hot that you cook the board or components. I doubt that a blow drier has that much heat.

 

[polbit]

Looks like the consensus is that this type of a board is not for amateurs I have actually gone out to Fry's again (3rd time in 3 days, my wife started scratching her head...), and got some bigger tips. Having just tried them, and with 700F, it was a bit easier, but still nothing to write home about. I like the idea about applying some liquid flux, I'll try that next.

This brings me to a couple of questions though:

1. What IS the recommended temperature? From reading on line, and answers here, it seems that everybody uses different temps... Weller sells tips for 600, 700 and 800F, so I'm assuming those are the most popular temps. Right now I am using 600F with my Hakko because it allows me to solder just fine with normal size holes, and the flux stays nice color, but sometimes I need to keep the iron on the join for good 3 seconds for the solder to start melting. On the other hand, I noticed that at 700F and the bigger tip, the flux was turning brown very quickly. The middle of my dial is 650F, so I will do my next kit at that temp and see how it feels I guess...

2. Is there any practical difference between 60/40 and 63/37 flux core solders? I am using 60/40, should I try getting 63/37, or will it be exactly the same?

Thanks!!

 

[3v0]

Looks like the consensus is that this type of a board is not for amateurs

I would not make that observation.

Heat flows from the tip to the board when there is liquid solder to conduct the heat between them. It is not uncommon to see people trying to solder with a trip that has no or too little liquid solder on it. Make sure there is a bit of liquid solder on the tip. Touch that liquid to the PCB and wire, and solder will flow if the board is clean and there is enough tip mass.

Do not get the impression that you need a huge tip to solder to a ground plane. I use my next to smallest needed tip but it takes a bit of coaxing. Not so much that it is worth switching tips or irons.

When soldering clean the tip when you remove it from the holder and apply a bit of solder to create the liquid on the tip you need to solder. I apply a bit of solder prior to putting it back in the stand to help prevent oxidization. On stuborn joints or when soldering SMD use liquid flux.

HTH

 

[cabala]

In answer to your second question, the two solders are pretty close to the same, it's really dependant upon what's in it and how big it is. I tend to stay away from any acid-based rosin core flux, because it's messy on you're board and slowly degrades your soldering iron tip.

I can't say how much I highly recommend an organic water based rosin core flux. It's clean and seems to work really well, but as you've probably noticed it's more a matter of opinion. I believe Kester is a popular solder manufacturer and can be bought from most dealers. I tend to stay away from radio shack type solder, becauase again the thicker the solder, the more heat required. Something on the order of .015" or .02" is really nice to work with. and stay away from anything silver based. Some of that solder melting temp is like 1000F.

In regards to the recommended temperature and different tips and what not, it again will depend upon who you ask. I work for Lockheed Martin and they have very strict soldering procedures that are basically dictated by NASA and as I said most of the industry follows this. There may very well be tips that support 700F to 800F and even higher, but these are generally for more industrial style applications, where you are soldering huge terminal lugs which 10 guage wire or the like.

The MIL-SPEC or military specification for soldering temperature is right around 598F or 600F (for electronics and PCB's) if you will and the time alloted for soldering tip application is on the order of 10 seconds or something, which is actually a little high. I've seen parts (mainly delicate IC's) get damaged when a technician is trying to desolder the part.

I'm thinking that most of the equipment you have is just fine for what you're trying to accomplish, especially if you are really ramping up the heat, but ultimately it sounds like the board you're trying to solder is just competely sucking up all the heat being applied to the pin.

Just out of curiosity, if you examin your through-holes or vias if there are any, does the little copper plating have any breaks in it. Depending upon whether the board has internal planes or even top and bottom layer copper pours for GND sinking, if the board isn't using thermal relief holes (looks like a little wheel with spokes), then it could theoretically never solder well.

I know none of this actually solves you're problem, but as a test of your equipment you should think about by a simple perf-board and try soldering some random resistors to it, with the correct temp and what not and see how it goes. It could be a sign that the PCB board is the problem.

[EDIT] And just a note, you can always tell if you are exceeding the temp of your solder if upon cooling it is a dull grey color and not shiny silverish looking. In this case you have exceeded the temp and have created a cold solder joint. I also agree about the last post on putting a dab of solder on the tip, while not in use but still kept hot. This does help prevent oxidation, but that is typically cause by the acid-based flux (or rosin core) in most solder.

 

[Speakerguy]

I recommend 63/37. It is a eutectic blend, meaning at this mix ratio the two metals solidify at the exact same temperature. In 60/40, one metal solidifies just a little bit before the other. If you've noticed a 'slurry' state right before a solder connection solidifies, that's it. One metal is crystallizing while the other is still molten. In large scale electronics production I believe 60/40 has higher failure rates over the long term. Whenever you buy a new spool you should get the 63/37 blend, but don't throw away your 60/40 over it. I recommend and use Kester 44 63/37 core 66 .031" for thru hole and .015 for SMT. Techni-tool has the lowest prices on Kester that I've found.

I work with tips 700-775F (OKi MFR station with SFP series tips). I've gotten quite good, and I can get in and out as fast as necessary even when soldering fine pitch IC's with a chisel tip without lifting a pad. In fact, out of forty-eight 28 pin TSSOP's, I actually managed to solder all of them and only had one pad lift, and it was an 'NC' pad that had no copper trace to heatsink it. 600 is a perfectly fine temp for leaded solder, and 600-650 is what I used when I was learning how to solder properly. Now that I'm good I use a hotter tip because tips for my station are really cheap, I'm quite fast, and I like the "hit it and quit it" feel of a hotter iron.

For someone new, I recommend staying 700 or lower. If you are having trouble with a joint, use a larger (not hotter) tip and liquid flux.

 

[Freq Band]

Yes, what the others said.

Clean the board with solvent (isopropyl alcohol),
steel wool or scotch-brite the board/copper area,
brush on some flux,
etc..
(don't use steel wool if there's a chance of getting the metallic wool bits caught into already soldered components, it could cause a short. Only use it on new empty pc boards.)

Soldering small areas, the "rule" is hold tip on the metal to get it hot, THEN flow on the flux core solder. But with large metal areas, adding a bit of solder while the tip is heating up/touching the metal, will give your tip more surface area, helping it transfer heat, faster.
Make sure your tip is clean, and does not have 30 minute-old solder on it....refresh it with fresh solder before doing those wide traces. You could sit there heating up the metal for 3 minutes with no luck, if you have a tip with old nasty burnt flux on it.

Another tip...say you're soldering a capacitor to a wide trace....you will need to add lot's of heat to the trace, but you don't want to add lot's of heat to the capacitor....so pre-solder the trace, around the hole (but not in the hole).
A pre-soldered trace will re-melt faster than starting without any solder.
When you put the cap in the hole, add solder as normal, remove heat when a nice shiny pool is seen.

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