Student Question and CIE Instructor Answer:
Q. I went to repair a cordless phone recently and found that many of the components seemed to be tack-soldered to the circuit board. I thought that tack-soldering was not an acceptable method for permanently attaching a component to a board.
A. These are called surface-mounted components. Instead of having the regular wire leads and IC pins that fit through holes in the circuit board, surface-mounted components have short contacts that are meant to be soldered to pads on the top of the circuit board.
Many of the components, such as resistors and capacitors are allso smaller than regular ones. This allows the circuit to be more compact, resulting in smaller circuit boards and less stray coupling between components.
Repairing these boards requires special techniques and equipment. CIE bookstore carries a set of lessons, along with a kit that teach these techniques.