What causes hairline cracks around pc board solder lands?

[catman]

G'day all, I think my general soldering technique is ok but of late on and off I've had the occasional issue on new unsoldered printed circuit boards, of hairline cracks developing after new soldering.

In one case recently the haircut crack went open circuit very intermittently, causing big headaches. :yes: What causes these? Is it just poor soldering technique, and are they avoidable? Regards, Felix aka catman.

 

[Robinhawaii]

Do you like complex answers?

http://www.ipcoutlook.org/pdf/best_practices_controlling_moisture_ipc.pdf

It may be moisture?

Take care,

Rob

 

[omishra]

Felix, Greetings!
I am not as experienced as you still I feel that is due to colder PCB surface or dirt/oxidation on PCB surface. With the tip of hot soldering rod, I heat the part lead and flux laced PCB surface same time, and then after 2 sec, I touch the joint with solder metal to be melt on solder tip. It flows quickly and nicely with shiny look.

 

[dr*audio]

What kind of solder are you using? What kind of flux is in it?

 

[Rick Vestal]

If they are kit pcbs, there's a a chance that the pads have a little bit of corrosion on them, especially if they have been sitting in someone's warehouse exposed to air for some time. Before assembling, take a generic pink eraser and clean all the pads. That's assuming the hairline you're describing is at the pad. If you're just getting hairline cracks in the joint itself, perhaps too cold an iron? Little to no flux? Also component leads can develop corrosion as well.

 

[Jon_Logan]

Well, to stack the deck in your favor

it's best to stay away from lead-free solder
Have a good iron,
maybe try 37/63 Eutectic solder
and apply enough solder.

Usually, fresh solder, good iron and no vibration while the joint cools results in a shiny strong joint. Make sure there's enough flux (and heat) that the solder-able surfaces all wet and stick to the solder.

 

[catman]

G'day all, thanks for the comments and thoughts. I use general purpose 1 mm 60/40 resin (lead based) cored solder which seems quite adequate for my soldering applications. Regards, Felix aka catman.

 

[glen65]

G'day all, thanks for the comments and thoughts. I use general purpose 1 mm 60/40 rosin (lead based) cored solder which seems quite adequate for my soldering applications. Regards, Felix aka catman.

What brand is it?

 

[catman]

G'day mate, this stuff: http://www.jaycar.com.au/productView.asp?ID=NS3010 Regards, Felix aka catman.

 

[petehall347]

best way to avoid it is possibly cleaning the solder pads back to clean copper then tinning them before soldering any components to them .
i am thinking there might be something left over from the etching process .

 

[sKiZo]

Yup. A touch of liquid flux and pre-tinning the pad should oughta do ya. Real old boards can also benefit from an alcohol preclean to get off a few years worth of neglect.

And steer away from the new no-lead blends. Not sure which is worse - the cold joints or the whiskers. Your blood pressure will probably kill you a lot quicker than the fumes would have ...

Could be temp too ... a good soldering station at around 650F works nice. They also recover temp quickly too, which could be part of your problem if you're using as standard iron and not allowing adequate recovery time between joints. My Weller station goes green to go again a couple seconds after finishing a connection. You also need to clean the tip between each and every joint. A dip in the brass (a wet sponge is the next best thing to useless IMHO) and then a dip in flux works wonders.

 

[glen65]

G'day mate, this stuff: http://www.jaycar.com.au/productView.asp?ID=NS3010 Regards, Felix aka catman.

Provided youre doing everything else correctly, soldering technique and so fourth,
about the only thing left is the material itself (the solder).
I dont know whats available where you live, but I would try switching brands
to something like Kester or Multicore. Radio shack silver bearing solder has
worked out pretty good too.

 

[ConradH]

Watching this with interest as I haven't see this problem. I'd be suspicious of poor quality PCBs and/or too thin copper. Solder does dissolve copper, but it isn't usually a problem until you get to very fine wire gages. That's where the silver solder with 1-2% silver content comes into play. It prevents the copper from going into solution. This just sounds like a PCB quality problem of some sort.

 

[Robinhawaii]

Hi Felix:

I'm sorry if I miss understood. Is the PCB developing the cracks or is it just the solder itself developing hairline cracks? Thank you.

Take care,

Rob

 

[catman]

G'day mate, little circuit board cracks are developing immediately around the solder points after soldering. Regards, Felix aka catman.

 

[Robinhawaii]

G'day mate, little circuit board cracks are developing immediately around the solder points after soldering. Regards, Felix aka catman.

Hi Felix: thank you for that. I guess the other posts were making me second guess what I thought I was understanding. The paper I posted talks about moisture being wicked into the board by the exposed fibers where it is cut and drilled. Basically putting it in a toaster oven and slowly bring the oven to just above 100 C to drive off the moisture prevents it from cracking. Any trapped moisture inside the the board will turn to steam when you put a localized heat to it. It expands very fast that it cracks the board.

I suspect even a hair dryer would work to warm it enough to drive the water out of it. A gentle heating of the entire area of the PCB.

Since it is happening in factory settings, I don't see why a hobbyist would be immune to such a phenomenon.

And you did have a bit of flooding there, so humidity was high there.

Take care,

Rob

 

[moray james]

has anybody discussed Eutetic solder? https://en.wikipedia.org/wiki/Solder
Best regards Moray James.
PS there is a reason why cheap solder is cheap.

 

[dr*audio]

Hi Felix: thank you for that. I guess the other posts were making me second guess what I thought I was understanding. The paper I posted talks about moisture being wicked into the board by the exposed fibers where it is cut and drilled. Basically putting it in a toaster oven and slowly bring the oven to just above 100 C to drive off the moisture prevents it from cracking. Any trapped moisture inside the the board will turn to steam when you put a localized heat to it. It expands very fast that it cracks the board.

I suspect even a hair dryer would work to warm it enough to drive the water out of it. A gentle heating of the entire area of the PCB.

Since it is happening in factory settings, I don't see why a hobbyist would be immune to such a phenomenon.

And you did have a bit of flooding there, so humidity was high there.

Take care,

Rob

I hadn't heard of this problem. This seems plausible. I had misunderstood and thought you had cracks in the solder joints.

 

[ConradH]

The issue of humidity sounds on-target. I always run a dehumidifier in the lab so everything is quite dry. I'd think it would take a lot before a multi-layer masked board would have an issue, but a typical bare board from one of the prototype houses might be a different story, and those are what I do the most of. What kind of boards have had this problem?