My invention pertains to fail-safe type connections for a printed circuit board. More specifically, this invention pertains to the use of a Kelvin type connection between critical circuit elements on a printed circuit board to eliminate any high contact resistance from affecting the vital operation of the same or subsequent circuit network.
Vital circuit design has previously considered the probable results of an improper or fault-induced increase in the value of circuit resistance by utilizing highly reliable molded carbon resistors. In circuits where gain is fixed by the ratio of two such carbon resistors, the probability of circuit malfunction due to an increase in resistance is greatly lessened. Other circuits, such as filters, also require guarantee against resistance increase. However, a poor solder joint connecting the various circuit elements may increase the total circuit resistance and also shift the ratio in an unsafe direction. This fault condition is particularly critical in printed circuit board wiring and a fail-safe arrangement for eliminating dangerous results of such faults has been needed.
Accordingly, an object of my invention is a fail-safe printed circuit board connection.
Another object of the invention is a method of making printed circuit board connections that shifts any added resistance due to a high resistance connection to the fail-safe side of such circuit connections.
A further object of my invention is an improved method of making circuit connections on a printed circuit board by which the external lead wire of a circuit element is connected by solder joints at spaced points along its length to two connector pads on the board, with an associated circuit element of the same network connected to the more distant pad and the network output taken from the near pad, to shift any high contact or solder joint resistance in the output connection to the safe side of the common connections.
Still another object of the invention is an improved, fail-safe connection for printed circuit boards which includes a first soldered connection at a first point on a circuit element connection lead and a second soldered connection at a more distant point on that lead, and the connection to an output circuit at the first solder connection to include any contact resistance in the output circuit.
Other objects, features, and advantages of the invention will become apparent from the following specification and appended claims taken in connection with the accompanying drawings.