Equipment Reports from Electronics Now Magazine
EQUIPMENT REPORTS from Electronics Now Magazine
(Jan. 1994) on the
It would be surprising to find a reader of this magazine who was not well versed in the fine art of soldering. But desoldering is another matter entirely. It seems as if every technician has his own favorite method. The DEN-ON SC-7000 desoldering tool seems to provide the right mix of features for everything from removing through-hole components from 12-layer boards to removing surface-mounted devices. It is available from, among other distributors, Howard Electronic Instruments (974 SE Pioneer Rd., El Dorado, KS 67042; phone 1-800-394-1984).
Technicians who need to desolder components only occasionally often find that the fastest and easiest way to go is a simple hand-operated spring-loaded vacuum tool. Desoldering braid is another favorite for low-volume desoldering. Higher-volume applications--where many circuit boards need to be reworked in an efficient, cost-effective manner--often require a full service/rework center with multiple soldering irons and desoldering tools.
The SC-7000 desoldering tool is unique in that it plugs directory into an AC outlet and is self-contained. No bench-top vacuum pump and connection hoses are required because the diaphragm pump is integrated into the handheld unit. The direct in-line connection between the pump and the tip provides such efficiency that 8-layer boards can be worked. That increases to 12 layers if the bottom side is preheated. The rated vacuum is 600 mm Hg, and the rated air flaw rate is 15 liters per minute with an open tip. The maximum vacuum can be reached in 0.2 seconds.
The SC-7000 is a gun-shaped device, measuring at its widest dimensions about 7 x 7 1/2 x 1 3/4 inches. It weighs less than one pound. The black plastic housing contains carbon, which helps to prevent damage to sensitive components form electrostatic discharge or ESD.
A rotary temperature control is located on the rear end of the gun. It can be adjusted from 300 degrees Celsius to 400 degrees Celsius (525 degrees Fahrenheit to 842 degrees Fahrenheit). Above the temperature control is an indicator lamp that remains steady as the tool comes up to operating temperature, and that blinks when the desired operating temperature is reached. If the temperature setting is reduced, the indicator remains unlit until the tip reduces to the new, reduced temperature. The tool heats up quickly, reaching its midpoint temperature (375 degrees Celsius) in about 2 minutes, and it also has a quick recovery time.
A power switch for the unit is located at the butt end of the gun, and a trigger for the vacuum pump is at the customary trigger location for a gun.
There are two other sets of controls on the SC-7000. First is a mechanical toggle that switches the desoldering tool between its section and its hot-air blow function. Another set of mechanical controls are used to change the two-piece filter cartridge which mounts behind the tip, above the trigger.
The filter cartridge design is effective in maximizing the life of the filter. Most of the solder and flux removed accumulates on a hard plastic base that is in front of the fibrous filter. When the cartridge is full, it is simply thrown away. Replacement filter cartridges cost about $5 each.
To remove surface-mounted components, a hot-air tip and hot-air filter cartridge are required. Tips can be changed easily with the small open-ended wrench supplied with the desoldering tool. An SMD accessory kit is recommended. It includes not only the hot-air blower nozzle and filter, but also stainless-steel wire and blades, and holders for the wire and blades, all of which make SMD removal possible
Surface-mounted devices can be removed in several ways with the hot-air blower. One method is to slip some stainless-steel wire under the legs of an IC, forming a loop. The wire is thin used to lift the legs as the blower melts the solder that holds them to the circuit board.
Another method is to insert a short length of stainless steel wire into the wire holder. As each lead is heated, the wire can be slipped under the lead, lifting it from the board. With a little practice, it is possible to desolder individual leads of a flat pack or small-outline package.
The stainless steel blade can be used in a similar manner to remove PLCCs (plastic leaded chip carriers) and chip resistors and capacitors from circuit boards.
The SC-7000 is available from Howard Electronic Instruments, Inc. for $395.00, which includes a convenient stand for bench-top use, and a cleaning pin set. An SMD removal kit, which includes a hot-air blower tip and other required materials, is available for $42.00.
Any technician who needs quality desoldering capability but who can't justify the purchase of a bench-top desoldering service center will be well served by the DIC SC-7000 desoldering tool.