JPS631723B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a proposal for a digital variable resistor with high precision and excellent durability.

As is well known, a type of digital variable resistor has been proposed in which a thick film resistor and a sliding part electrode are arranged on a ceramic substrate. When the slider slides on the sliding part electrodes, it also slides on the ceramic between the electrodes, which has the disadvantage that the contact portions of the slider are severely worn and the life of the slider is shortened. Furthermore, fine powder from the electrodes and slider contacts generated by sliding accumulates on the trajectory of the slider contacts, lowering the insulation resistance between the electrodes and causing deterioration of electrical performance. are doing.

The present invention has been proposed in view of the above-mentioned points, and is characterized by having a simple structure with improved mechanical and electrical performance.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view of a printed circuit board of a digital variable resistor according to the present invention, in which 1 is a ceramic substrate, and 2 is a resin-based substrate made of a base material such as paper phenol or glass epoxy. The ceramic substrate 1 is provided with ten resistors R ₁ to _{R 10} having the same resistance value, which are formed into thick films with high precision by laser trimming, etc., and each resistor is connected by a conductor. A series circuit is formed, and 11 resistor electrodes Pr ₀ to Pr ₁₀ are led out from both ends a ₀ and a ₁₀ of the series circuit and connection points a ₁ to a ₉ of each resistor. In addition, on the surface side of the resin substrate 2, which is made of a softer base material than ceramic, there is a ring-shaped common electrode Pc and this common electrode.
Ten position electrodes P 0 to _{P 9} arranged on a concentric circle around the Pc and printed and wired in a mutually insulated manner from the " ₀ " position to the "9" position are formed as sliding part electrodes. The position electrode
Connecting electrodes Pc ₀ to _{Pc 9} are derived from P ₀ to _{P 9} respectively, and when the ceramic substrate 1 and the resin substrate 2 are stacked, the connection electrodes Pc 0 to Pc 9 are connected to the positions corresponding to the resistor electrodes Pr ₀ to Pr ₉ , i.e. On the back surface of the resin substrate 2, the connection electrode Pc ₀ is arranged in a position opposite to the resistor electrode Pr ₀ , and the connection electrode Pc ₁ is arranged in a position opposite to the resistor electrode Pr ₁ , so that they are formed in pairs. are doing. Further, only the resistor electrode Pr ₁₀ has a connecting electrode Pc ₁₀ formed separately as a pair of electrodes at a position opposite to the back surface of the resin substrate 2. In order to closely attach the two printed circuit boards having such a configuration, the resistor electrodes Pr ₀ to Pr ₁₀ and the connecting electrodes
Each electrode from Pc ₀ to Pc ₁₀ is soldered,
The resistor electrodes Pr ₀ to Pr ₁₀ and the connection electrodes Pc ₀ to _{Pc 10} are soldered and connected by heat treatment, and the ceramic substrate 1 is
and resin substrate 2, and lead out both ends a0, _a10 and connection points a1 to _a9 of the series circuit of resistors _R1 to _R10 and connection points _a1 to _a9 to position electrodes _P0 to _P9 and output terminal _T10. and is connected. Note that the output terminal _T10 is the output terminal
The output terminal T ₀ is connected to the resistor electrode Pr ₀ through the position electrode P ₀ and the connection electrode _{Pc 0} , and the output terminal Tc is connected to the common electrode Pc 0. It is connected to PC by a conductor and forms a terminal for outputting the resistance value.

FIG. 2 shows a wiring circuit diagram showing an outline of the circuit printed and wired on the above-mentioned printed circuit board. In the figure, the slider S is located at the position electrode _P2 ,
In other words, the contact is in contact with the electrode in the "2" position, and the other contact of the slider S is the common electrode.
Since the position electrode _P2 and the common electrode Pc are in contact with Pc, conduction is established between the position electrode P2 and the common electrode Pc.If the resistance value of each resistor _{R1 to R10} is rOhm, then 2r(r
+r) ohm is output. This slider S has a dial (not shown) with numbers "0" to "9" printed on its outer periphery corresponding to the position electrodes P ₀ to P ₉ .
The electrode (position electrode) is attached to the resin substrate 2 and is formed on the resin substrate 2 by rotating the dial.
_P0 to _P9 and the common electrode Pc) to switch the electrodes and select the set resistance value.

FIG. 3 is an external view, partially cut away, showing the state in which the printed circuit board shown in FIG. 1 is mounted on a digital variable resistor.

As explained above, in this invention, the printed circuit board on which the electrode on which the resistance value switching slider slides is arranged is separate from the printed circuit board (ceramic board) on which the high-precision thick film resistor is arranged. By using a printed circuit board (resin-based board) that is softer than ceramic, the two printed circuit boards are bonded together through heat treatment, and the electrical connection is made without reducing the accuracy of the resistance value. Since contact wear of the slider can be suppressed, mechanical performance and electrical performance can be improved, and the structure can also be made compact and easy to assemble.

It goes without saying that various other configurations are possible without departing from the gist of the invention.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a printed circuit board constituting a digital variable resistor according to an embodiment of the present invention, Fig. 2 is a wiring circuit diagram of the above embodiment, and Fig. 3 is a cross section of a part of the above embodiment. This is an external view. 1...Ceramic substrate, 2...Resin-based substrate,
R ₁ ~ R ₁₀ ... Resistor, Pr ₀ ~ _{Pr 10} ... Resistor electrode,
Pc……Common electrode, _P0 to _P9 ……Position electrode,
Pc ₀ to _{Pc 9} ... Connection electrodes.

Claims (1)

[Claims] 1. A ceramic substrate comprising a resistor series circuit in which a plurality of thick film resistors are connected, and resistor electrodes led out from each connection part and both ends of the resistor series circuit, and a slider on one surface. and a resin-based substrate on which a sliding part electrode is disposed in sliding contact with the resin-based substrate, and a connecting electrode led out from the sliding part electrode is arranged on the other surface, and the ceramic substrate and the resin-based substrate are bonded. A digital variable resistor, characterized in that opposing electrode pairs of the resistor electrode and the connection electrode, which are disposed at opposing portions of both substrates, are electrically connected.