Need advice on ROHS lead free solder

[substitute]

Hey all,
I'm doing some sub contractor work for a pro audio company, I have to use lead free Rohs compliant solder.  It's killing me, this is so frustrating.  It's like everything is a cold joint.  With point to point stuff I'm not having any problems but PCBs are a nightmare.  Does any one have any advice?

I'm using a 35w iron, I have a fresh tip, temp is all the way up.  What am I doing wrong?

 

[zayance]

35w iron

Maybe a little weak, try a 65W type iron, like a Hakko 936 or so, just my 2 cent.

 

[zebra50]

It's like everything is a cold joint.

Some of the lead free solders seem to give a 'matt' rather than shiny joint, even though the joint is good.

 

[sahib]

Lead free stuff has a much higher melting point. As Zayance said you'll need to use a heavier soldering iron.

By the way I hate it too.

 

[substitute]

By the way I hate it too.

Thanks, that makes me feel better.  Should 65watts do the trick?  Since I only own a 35w iron, I don't really mind buying a higher powered iron it's something I should probably have on my work bench regardless of this project.

The Hakko 936 seems pretty reasonable, any other recommendations?

Thanks for the help guys!

 

[babyhead]

Someone please correct me, but I was told 700degF was a good temperature for PCB work.

 

[substitute]

I did some googling, and found this document.  Seems in order with what everyone's saying...

Hand soldering processes
Even for hand soldering, the processing differences between tin lead and lead free must be considered. The solder tip must be adjusted to the higher temperatures required. For lead free solders, the EMPF found that the solder tip temperature needed to be set between 343°C / 650°F and 371°C / 700°F as opposed to 315°C / 599°F for tin lead solders. Temperatures higher than 398°C / 750°F were considered unnecessary for most hand soldering applications.

Because of the higher processing temperatures, components and boards must be baked out prior to soldering. Studies show that components increase moisture sensitivity by 2 levels, based on IPC J-STD-020 guidelines. Bake out insures that moisture is driven out prior to processing. Entrapped moisture is the root cause of component and board delamination and popcorning. The EMPF determined that boards should be preheated between 100°C and 125°C in order to reduce thermal shock and prevent pad lifting.

Operators must be re-trained to support lead free solders. EMPF staff have trained operators in the nuances associated with lead free hand soldering. Lead free solders require a longer dwell time – the time the soldering iron is in contact with the hardware. The longer dwell time promotes adequate heat transfer.

Due to the higher soldering temperature, the soldering iron needs to be removed more quickly for lead free solders, otherwise icicles will form. The size and frequency of solder icicles is dependent upon the alloy used and the temperature setting of the soldering iron.

The higher soldering temperature also requires that the soldering iron must be kept clean and coated with the solder alloy. Lead free solders are more sensitive to the effects of a dirty soldering iron. The higher soldering temperatures can cause oxidation of the soldering iron tip if not cleaned and coated. In addition, the EMPF recommends that different soldering irons be reserved for lead free and tin lead soldering. If the same soldering iron must be used for both, the EMPF recommends that different soldering tips be used for each type. Separate tips will prevent lead contamination of lead free components and solders.

A completed lead free solder joint has a grainy, dull finish. The bright surface associated with tin lead solders is not a material characteristic of lead free solders. Because of this difference, operators and inspectors need to adjust their visual inspection criteria. The IPC has changed the visual inspection criteria of J-STD-001 and IPC-A-610 to take this into account.

Once these adjustments were implemented, the electronics manufacturers audited by the EMPF were determined to have the capabilities to perform lead free hand soldering.

 

[zayance]

Someone please correct me, but I was told 700degF was a good temperature for PCB work.

I use that temp. but of course the higher the temperature,the faster your tip will be dead, for that i just clean it with tip tinner/ cleaner just to preserve it a little more.

The Hakko 936 seems pretty reasonable, any other recommendations?

I have a Hakko 936, works great not too expensive i think it's a good choice, there are some more expensive ones, and some cheaper Aoyue brand etc..., i can only speak for the Hakko, have it, happy with it  

 

[geoff004]

I recently went lead-free.  I don't feel like it was a real difficult switch.
Using a Weller WES51 and AIM solder.  My main complaint is the smell of the flux.

 

[dagoose]

I'm still trying to get used to it as well, bought a pile of leadfree solder some time ago and recently started to use it. It feels as cold solder joints when you see it but it is a good joint. I slowly get used to it though i like the shiny leadholding solder joint just a bit more...

 

[substitute]

from my the guy I'm doing the work for...

The lead-free boards are very sensitive to humidity and will oxidize very quickly if they encountered relative humidity over about 45%. The solution is a thorough cleaning of the pads before soldering. Everyone has their own favorite way to do that. I simply use a soldering aid tool that has a flat end and buff the pad. Others use a small wire brush. If you have a flux pen, an application of flux can be helpful right after the pad is cleaned. If you're working in an un-air conditioned environment, I would think you have less than a minute to solder the pad before it will need cleaning again.

That seems to add up, I didn't know about cleaning the pads, and it was blazingly hot.  It wasn't that I couldn't melt the solder, it would just sort of bead up around the component lead and not flow to the pad at all. 

 

[geoff004]

It wasn't that I couldn't melt the solder, it would just sort of bead up around the component lead and not flow to the pad at all. 

Heat the pad, not the component.

 

[Andy Peters]

from my the guy I'm doing the work for...

The lead-free boards are very sensitive to humidity and will oxidize very quickly if they encountered relative humidity over about 45%. The solution is a thorough cleaning of the pads before soldering. Everyone has their own favorite way to do that. I simply use a soldering aid tool that has a flat end and buff the pad. Others use a small wire brush. If you have a flux pen, an application of flux can be helpful right after the pad is cleaned. If you're working in an un-air conditioned environment, I would think you have less than a minute to solder the pad before it will need cleaning again.

That seems to add up, I didn't know about cleaning the pads, and it was blazingly hot.  It wasn't that I couldn't melt the solder, it would just sort of bead up around the component lead and not flow to the pad at all. 

First off, I'll say that you're doing your client (and yourself!) a disservice if you're not using a proper temperature-controlled soldering tool. Be prepared to spend $300 getting there. No free lunch.

Second, we've been getting boards done with gold finish on all exposed pads. They're much easier to solder with the lead-free stuff. Consider telling your client to do the same.

Third, you still need a proper flux!

-a