Weller blog

Many people have the impression that if they are working with lead-free solder, the need for efficient fume extraction is decreased. But the lead in lead bearing solder alloys is not the main culprit in the creation of dangerous fumes. The fluxes used to facilitate solder reflow are the main contributors to noxious fumes and gasses in the work place.

For operators subjected to these conditions every day, it is very unpleasant to say the least. But it can be much worse, resulting in long-term health problems and the legal responsibilities that follow. Weller fume extraction systems put an end to pollution by reducing fumes either from the ambient area, or directly from the source - the soldering tip.

The Weller WSA350 smoke absorber is an entry-level ambient fume extraction system. It is a low-cost way to direct fumes away from the workspace and through a replaceable carbon-activated filter. It has an absorption capacity of 1.25 m³/min.

The Weller WFE2P fume extraction system utilizes the efficient source extraction fume removal method. A soldering pencil is fitted with a built-in source extraction tube, which is positioned directly over the solder joint during the soldering process. Specially designed soldering pencils are available to work with the WFE2P. Attachments are also available to add fume extraction capability to standard Weller pencils. The WFE2P can accommodate two fume extraction-soldering pencils simultaneously. The efficient three-stage replaceable filter system extracts 99.99% of fumes before they can be released into the environment. The filter system consists of an F7 grade fine dust filter, a main filter consisting of a wide band gas filter (50% activated carbon and 50% puratex), and a HEPA class 13 fine particle filter. The filter lift system allows fast and easy filter replacement. For this reason, source extraction remains the most efficient method of removing noxious fumes and gasses from the workspace.

The Weller FE75 soldering pencil is a powerful 80-watt pencil with the temperature recovery performance necessary for working with lead free solders. It is compatible with the Weller WD Series soldering stations.

A complete line of accessory fume extraction conversion kits is available for easy conversion of your Weller soldering pencil. With these accessories, you can convert your Weller soldering pencil into a source fume extraction pencil that is compatible with the WFE2P fume extraction system.

QUESTION: What changes are necessary in soldering tool design/performance when working with lead-free solder?

ANSWER: Soldering irons and stations will require the capacity to bring the joint to sufficient temperature rapidly and hold that temperature with minimal recovery time. More powerful tools will do the job better just like a car engine with more horsepower will pass quicker and climb hills easier.

Besides having the necessary power, the optimal soldering tool will also possess very efficient heat transfer to the work. This efficient heat transfer, plus sufficient power, will ensure that recovery rates are very fast and will not slow down operations when moving from joint to joint. In addition dwell time on the PCB will be minimized.

Efficient delivery of the heat to the joint depends on a number of factors:

• Adequate power from the heater
• Proximity of the heater to the working end of the tool
• Thermal efficiency in delivery of the heat to the joint (geometry and tip/heater materials)
• Some means of quickly sensing the need for delivery of more heat (location of sensor)
• Accurate control of the tools temperature (microprocessor control with no overshoot).

QUESTION: What changes are necessary in soldering tool maintenance when working with lead-free solder?

ANSWER: One of the biggest challenges when working with lead-free solder is proper maintenance of the solder tools.  High percentages of the tin in the lead-free alloys will have a harmful effect on the tools.  Iron tips and solder pots will degrade at a faster rate which will affect the thermal transfer capability.  Some equipment will have to be replaced and more attention given to maintaining the quality of the soldering iron tips.

Operator training in using the correct methods will pay huge dividends.  Operators should immediately develop the habit of tinning the tip after the soldering operation as well as using distilled water for solder sponges.  Tip tinners and polishing bars may be used as a regular part of iron maintenance.

I have had a chance to use the new WD2000M rework station I recently purchased. I am using the RT2 tip in the soldering pencil and RTW2 tweezer cartridge for the micro tweezers. I found out that I can set the temperature at only 660° F and still have plenty of heat to solder 0805 and 0603 surface mount components. I am using Kester part no. 24-7068-1401 solder. It is .020 inches in diameter and is rosin-activated solder. It is also RoHS lead free solder.

I have also found that I can solder 26-gauge bus wire onto a solid 1-ounce copper ground plane, with the temperature set at just700° F. The heat is at the tip almost immediately. It takes only 3 to 4 seconds to go from setback to set temperature after picking the soldering pencil up from the stand. Also, the heat doesn't seem to dissipate with the heat sinking of a large area.

I have only used the tweezers a few times but the alignment is good and I am still playing around with the temperature to get it just right for component removal. I can tell you that this system works a lot better than the competing systems I have used.

Thanks,

Clayton Bennett

Electronic Technical Specialist
Design Engineering Lab
Analog and Mixed Signal Products Group
INTERSIL CORPORATION
http://www.intersil.com/

QUESTION: Do we have to adjust our hand soldering techniques to work with lead-free?

ANSWER: When making the move to lead-free, a common mistake is to turn up the soldering tool temperature. This can be dangerous. Operators are surprised to find that most of their through-hole and surface mount components can be soldered at or below 700° F. This is especially important when using no-clean flux.

When the iron temperature is at the point of charring the flux, a defect is created and cleaning is required. Instead of starting with a higher tip temperature, the operator can try watching for wetting at a given temperature and decide if the process can be done in a reasonable dwell time. Pre-heating reduces reflow time and the risk of heat-related damage.