CASEBOOK 2

Dispensable Paste Solder Helps Refine a Sticky Procedure

Increases throughput and eliminates operator error

When a medical equipment refurbisher wanted to improve its procedures and increase productivity, the company decided to first examine its soldering process. Soldering is integral to the work being done at Servicetrends Inc., located in Marietta, GA. The company specializes in refurbishing the electrodes used in lithotriptors, machines that pulverize kidney stones with sound waves.

The electrode's conical upper tip serves as the hub of a "cage" of six insulated copper wires. After the tip has been removed and reground, the ends of the wires must be resoldered into six holes (1.35 mm wide X 12.7 mm deep) in the brass outer conductor.

Soldering the fine wires was a time-consuming operation entrusted to only a few highly skilled workers. Irons were used to force wire solder down inside the small blind holes. The process involved much reworking since excess solder had to be removed and melted, or discolored insulation had to be trimmed away. Electrode department manager Earnest Pringle was certain that if he could find a way to put an identical amount of solder in each hole, the process could be made faster and less operator-dependent, thereby improving productivity.

Pringle contacted EFD Inc. (East Providence, RI) and described his objectives. EFD's product specialists recommended SolderPlus, a paste solder developed as an alternative to flux-core wire. Prepackaged in 10- and 30-cm³ barrels, the material is specially formulated for use with automatic dispensing equipment. Unlike wire solder, SolderPlus can be placed at the bottom of small holes and other areas that are difficult to reach. In addition, using the dispenser's precisely timed air pulse to determine the amount of material applied ensures consistent deposits and makes it easy to cross train any operator on the soldering operation.

Replacing flux-core wire with SolderPlus enabled Servicetrends to make a time-consuming soldering operation faster and less operator-dependent. With the company's previous method, wires had to be soldered one at a time. Now, a dispenser is used to place an identical amount of SolderPlus into each of the holes in advance. A microtorch is used to reflow all six deposits at once. Throughput has increased, and the rework required due to overapplication or scorched insulation has been eliminated.

"Our new method is both quicker and more reliable," Pringle says. "The more consistent deposit size results in a better-looking assembly. We also have greater peace of mind knowing that we now have several cross-trained employees who can perform what used to be an operator-dependent procedure."

For more information contact EFD Inc. at 401/434-1680.

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