Lead-free solder/paste

[tdma]

Which lead-free solder do you use and why? (I'm talking both wire and paste.)

Many supplies carry SAC305, some 99.3% Sn / 0.7% Cu . . .

I was tented to buy SAC305 because it has a lower melting point, until I read it has to be used in a nitrogen atmosphere. Is that true?

Which one do you prefer for manual soldering and hot air rework?

 

[yura717]

I use lead-tin solder because its cheaper....

 

[davenn]

At home I am still using lead/tin not just because of price but its easier to work with eg. lower melting point.
Much major manufacturing around the world is now conforming to RoHS standards and using lead free.
I am finding in equip I repair that it is causing many more dry joint problems.

cheers
Dave

 

[yura717]

**broken link removed**

 

[shawnsantana]

There are many lead-free solder alloys available, but you are correct that SAC305 tends to be the most common and most widely used. It is not true that SAC305 can only be used in a nitrogen atmosphere. you can solder SAC305 just as easily as standard tin-lead eutectic solder. Almost all lead-free solders will require a little more heat, and people who are used to tin-lead will need to adjust slightly for a longer dwell time when hand soldering. The final look of a lead-free solder is also very different from a tin-lead joint and often looks much duller.

Some solder alloys to consider:
SAC305 - Most common
SAC105
SN100C
SN995 (cobalt-doped)

 

[tpetar]

Restriction of Hazardous Substances Directive RoHS
https://en.wikipedia.org/wiki/Restriction_of_Hazardous_Substances_Directive

The Directive on the restriction of the use of certain hazardous substances in electrical and electronic equipment 2002/95/EC (commonly referred to as the Restriction of Hazardous Substances Directive or RoHS) was adopted in February 2003 by the European Union. The RoHS directive took effect on 1 July 2006, and is required to be enforced and become law in each member state. This directive restricts the use of six hazardous materials in the manufacture of various types of electronic and electrical equipment. Any RoHS compliant component is tested for the presence of Lead (Pb), Cadmium (Cd), Mercury (Hg), Hexavalent chromium (Hex-Cr), Polybrominated biphenyls (PBB), and Polybrominated diphenyl ethers (PBDE). For Cadmium and Hexavalent chromium, there must be less than 0.01% of the substance by weight at raw homogeneous materials level. For Lead, PBB, and PBDE, there must be no more than 0.1% of the material, when calculated by weight at raw homogeneous materials. Any RoHS compliant component must have 100 ppm or less of mercury and the mercury must not have been intentionally added to the component. In the EU, some military and medical equipment are exempt from RoHS compliance.

You cant import, cant manufacture and sell parts or devices with hazard materials, for exceptions are made with special aprovement such for lithium material in some chips and batteries.

They whant to "improve" environment, on one side we replacing light bulbs with economicaly CFL bulbs, old TV with new LCD,LED,Plasma,... RoHS everywhere, and we get house full of lead and other toxic materials everywhere.

 

[RetroTechie]

They whant to "improve" environment, on one side we replacing light bulbs with economicaly CFL bulbs, old TV with new LCD,LED,Plasma,... RoHS everywhere, and we get house full of lead and other toxic materials everywhere.

Care to explain what you mean? If you throw some old electronics in a landfill, some lead may leach out (okay probably very little), some mercury or cadmium from batteries (both nasty metals to have in environment). If you burn the plastic case, bromine compounds can be released.

If you do the same with a RoHS compliant device, the above nasties will be absent or at far reduced levels. Okay CFL bulbs contain mercury, but only a small amount per bulb and it lends itself well for recycling. That's apart from the big energy savings over its life.

Reducing those nasty materials in all the electronics we stuff our homes with, is a Good Thing ®. Only problem I have with RoHS is cases where it might reduce reliability of devices, so that they're thrown away faster than people already do these days. More research and hard numbers on that would be good, but so far I'm not seeing a 'pandemic' of electronics breaking down all over the place. Well to some degree - that's a long term ongoing trend, but more an issue of stuff designed to be non-repairable / cheaper, cheaper, cheaper / build quality etc. rather than lead-free solders.

 

[godfreyl]

Care to explain what you mean?

According to that article:

One criticism of RoHS is that the restriction of lead and cadmium does not address some of their most prolific applications, while being costly for the electronics industry to comply with. Specifically, the total lead used in electronics makes up only 2% of world lead consumption, while 90% of lead is used for batteries (covered by the battery directive, as mentioned above, which requires recycling and limits the use of mercury and cadmium, but does not restrict lead). Another criticism is that less than 4% of lead in landfills is due to electronic components or circuit boards, while approximately 36% is due to leaded glass in monitors and televisions, which can contain up to 2 kg per screen.