|Ask the Experts|
October 3, 2017
Recovering Solder from Dross
5Does it make economic sense to develop an in-house capability for recovering pure solder from solder dross? What are the benefits, if any, for developing this capability and are there drawbacks that should keep us from doing this?
|Expert Panel Responses|
The environmental requirements and regulations which would be imposed to initiate this kind of process within your facility may be quite substantial and expensive. The collection of dross and the return of such material to the supplier should be sufficient as the suppliers are already doing this kind of work. Secondly you can get a certificate of analysis where the recycler will provide you with the elemental levels within your samples and pay you for the cost of your materials. If you're soldering many gold boards the gold is retrievable from the dross and solder samples and this relates to a cost which should be refunded to you by the recycler.
Vice President, Technical Director
You have to evaluate on a case by case basis and as well determine what type of ROI you are looking for. For instance if you generate 1,000 Lbs/year of SN100C dross the savings if your return on a piece of equipment is 100% might be $7.00/Lb X 1,000 = $7,000. If the piece of equipment your are looking at costs $10,500 your ROI is a year and a half. As you use more expensive alloys like SAC305 your ROI becomes less as the savings is greater. Some of the drawbacks are:
If you are going to create a system to recover solder, then before you start I would look at this website EVS International website. They have a system for solder recovery at the source. The benefits are clearly outlined.
Regional Sales Manager
OK International Inc.
Solder dross has gone from being a cost to be considered by large companies to a very high cost that must be tracked for all who assemble electronic devices. As much as 70% of bar solder can be wasted as solder dross and with SAC 305 now at the $25/Lb level and even leaded solder costing almost twice as much as in previous years it is a major issue. Recovering your own dross could save you money but it is not an undertaking that should be done lightly. Besides the equipment, cost and manpower necessary here are a few thoughts to consider To recycle dross some states require processing permits and the permits would need to comply with local regulations.lead treatment compliance issues are even more complex, they would apply include Blood lead testing for employees,ventilation issues, dust collectors and hoods, pollution insurance etc... The bi-product generated from sweating dross or separating good metal from oxides and flux residues is typically not desirable and could become a disposal issue for the generating company. Typically only 50% of the metal can be recovered from dross recycled by pot sweating and the single wave unit squeezing machines are not much more effective. There is more value to the company by simply selling the dross for the best price however sale of dross to a recycler is something that often makes more money for an employee selling it out the back door or a middle man than it saves for the company. Many companies do not realize the value of dross, especially lead free dross. Many company senior managers would be amazed at the hundreds of thousands of dollars of company assets (bar solder dross) that just disappears from the balance sheet. Because of the exponential increase in the cost of metals coinciding with the shift to lead free every company should be accurately tracking their solder usage and should get a handle on the cost of dross. So many do not really have a clue. New in line processes such as MS2 from P. KAY Metal have been developed to actually halt the formation of dross right in the wave solder machine and therefore save 50% to 70% of the solder. Actual reductions in solder purchases of this magnitude have been proved. This process saves a moderate sized company many hundreds of thousands of dollars a year. Because this is an in line process the using company is not a recycler and is therefore not required to do anything more on the regulatory side than they must do to solder boards. One thing for sure, the old days of just letting a low level manager handle the sale of dross to a recycler and not tracking the entire bar solder usage/purchase life cycle is rapidly coming to a close if an assembly company is to remain profitable and competitive.
President and Founder
Does it make economic sense to develop an in-house capability for recovering pure solder from solder dross? This depends on two parameters:
Recovering solder from your dross can be very profitable for your company if done correctly and at a great price. A lot more goes into recovery than one might think, due to regulations and safety concerns.William Malcolm, Electrum
The main concern is not effectively dedrossing out the contamination such as Copper, Lead, Gold, Nikel and other elements that would normally be removed in the dross. You will simply add them back into the pot and allow them to build up until you ar eover the maximums allowed. Also the antioxidants added to the Pure new Solder will be depleted out so you will actually produce more dross and reduce the flow properties of the alloy in the bath inreasing bridging and reducing the wicking effectiveness of the solder.
Additive bars can be purchased to improve this but the non removal of impurities is a concern. Other contaminants such as Resist and HASL fluxes will out last the heat of the recycling machine and be put back into the pot which is far from ideal.
Technical Sales Manager
BLT Circuit Services Ltd
While the in-house "recycling" process can certainly be viewed as a money-saving endeavor, there's a downside which this article seems to view as a footnote: creating mystery alloys.Pete Ruth, Tin Technology and Refining
When you're simply melting the dross and metal inclusions back into ingot form, you're not removing deleterious elements. You're actually concentrating them. Thus, you cannot have a truly controlled process because you don't know the alloy you're creating. Alpha did a good study on this many moons ago (https://www.smta.org/knowledge/proceedings_abstract.cfm?PROC_ID=4490) and it is beyond clear that the economic savings from supposed in-house recycling (read: remelting) is sorely lacking as it does nothing to control the alloy you're putting back in your tank.
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