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Steven Latimer & Martin Muir
Pca Engineering
Compaq Computer Manufacturing

A Study on the effectiveness and benefits of the Solder Reclamation System

Background Information

Compaq Erskine Pca Waste Solder Process

Why Recover Solder?
As part of Compaq's continuing Commitment to the environment, waste elements removed from the board shop for processing outside the factory are to be processed in-house. As stated this function since the day the Board-shop opened was performed by an outside source, any solder reclaimed is returned at a reduced cost or concessions made for the purchase of new solder While this method was an acceptable solution at the time more and more emphasis is now being placed on companies to provide solutions for their own waste, to this end a way for Compaq to process the waste in-house had to be found.

Are There Any Processes Available To Us Which Can Recover Solder From Dross?
Initial investigations returned a manufacturer that supplied a machine that would meet these requirements, the supplier of the EVS also agreed to allow a period of approval to assess the machines capabilities and suitability for our needs.

The main purpose for this machine is to reclaim as much of the usable solder from the dross collected as possible, the manufacturer of the machine claimed rates of up to 75% reclamation which if achievable would more than meet the requirements. During trials and subsequent production the EVS averaged a 61% recovery rate.

Machine Operation And Maintenance.
Another requirement for this system is its ergonomics. Since it would be line operators that would be operate this system then the operation and maintenance should be both simple and efficient.

The basic operation of the system involves initially switching the machine on and allowing it to come to operating temperature, The operator would then place the waste dross into the cylinder for processing, a single machine can be de-drossed and the process takes approx. 7 minutes per cycle (total de-dross time was consistently measured at 60 minutes).

This cylinder has a piston at one end which when activated squeezes the solder dross until all the recoverable solder has been removed. This solder is then returned in the form of ingots and can be returned to the solder pot. (A sample of the reclaimed solder was analysed by our solder supplier and found indistinguishable from virgin solder of the same grade).

The operator can carry out maintenance for this system and due to its construction there are very few parts that require regular maintenance, the main requirement is for the piston and the chamber itself to be regularly cleaned of dust build up and for the stand-alone filter to be properly maintained.

The only facility which would be required for installing the Solder Recovery System would be a pneumatic supply and two 13Amp, 3pin sockets.

The EVS is supplied on it's own trolley which can be freely wheeled between separate wave solder machines.

Evaluating the effectiveness of the EVS. Below are the figures for solder usage and dross reclamation for 1995 (pre-EVS).

• Total solder costs Total Weight x Cost per KG   £90,901.44
• Total dross credit 8,634kgs at £0.80/kg £6,907.20
• Net solder supply cost for 1995 £84,000

If we were to use the EVS for this period:

• Total solder costs        Total Weight x Cost per KG .£63,576.90
• Total dross produced before SRS (41.1% dross rate)* 5,215.6kgs
•  Dross recovered through SRS (61% recovery rate)# 3,181.5kg

*41.1% dross rate (based on 1995 figures for CAR 9642234).
#based on 61% average solder recovery rate.

We would still receive credit for the 2,034.1kg of dross produced after the EVS process. At £0.80 this would give £1,627.28 credit.

After installation of the EVS in April 1997 measurements taken showed the EVS to be outperforming expectations. The machine was returning a 34% saving on solder costs.

Machine Reliability
When properly maintained this machine is extremely reliable. Any problems that have been encountered have been remedied by the manufacturer and suggested improvements have been included in the design of subsequent machines. Service and spares have also been of an acceptable standard during the time we have owned the machine.

From trials and subsequent production we can achieve an average 61% recovery rate, with a rate as high as 80% on occasions. The variation in rates can be attributed to the differences in how operators perform this operation. Some operators "squeeze" the solder before placing dross in the EVS. This therefore means a lower recovery rate.

The machine also contributes to Compaq's ISO14001 targets.

Prepared By -
Steven Latimer And Martin Muir - Pca Engineering

Approved By -
Tony Howard Snr Process Engineer - Pca Operations Compaq Computer Manufacturing