JPH1167509A - Method for adjusting resistance value of circuit board and circuit board with variable resistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for adjusting the resistance value of a circuit board by which the resistance value of an electrically connected variable resistor on a circuit board can be adjusted by trimming. SOLUTION: A series circuit of a variable resistor 12 and a fixed resistor 13 is connected to an element group which is the circuit configuring element of a circuit board and, at the same time, a constant-current source 21 is connected to the both ends of the variable resistor 12. A resistance value Rx of the variable resistor 12 is adjusted by trimming according to Rx=V1/(I-V2/R1), while the resistance value is monitored based on the both-terminal voltage V1 of the variable resistor 12, resistance value R1 and both-terminal voltage V2 of the fixed resistor 13, and the current I which flows to the junction between the resistors 12 and 13 from the constant-current source 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adjusting a resistance value of a circuit board using a trimming technique and a circuit board having a variable resistor to be trimmed.

[0002]

2. Description of the Related Art In recent years, as electronic circuits have become more sophisticated, there has been a demand for higher precision in the resistance value of resistors in a circuit board. A trimming technique is widely used as a technique for improving the resistance value of such a resistor and correcting the resistance value of the resistor.

In the conventional trimming technique, while monitoring the output signal of the circuit,
The resistance value of the resistor to be trimmed is adjusted so that a predetermined output voltage and a predetermined current value are obtained. (See JP-A-7-245205).

[0004]

In a circuit board having such a variable resistor whose trimming is adjusted, it is necessary for the variable resistor to properly set its own resistance value, such as a resistor for temperature correction. In such a case, it is necessary to adjust the resistance value of the variable resistor in a state where the variable resistor is separated from other circuits (see JP-A-1-187902 and JP-A-6-267707).

[0005] One method for this is to trim the variable resistor before connecting it to another circuit, that is, to trim the variable resistor alone. However, in this case, since it is necessary to individually manage the variable resistors set to various different resistance values, the management cost increases and the management becomes complicated.

As another method, as shown in FIG. 3, a variable resistor 12 and another circuit (circuit element group 11) are used.
Is connected, that is, after a desired circuit is formed on the circuit board, one end of the variable resistor is opened (opened), and the trimming is adjusted while monitoring the resistance value Rx of the variable resistor with the ohmmeter 31 or the like. There is also. However, in this case, after trimming the variable resistor 12, one end of the released resistor and another circuit must be connected again, so that the number of manufacturing steps of the circuit board increases, and the productivity associated therewith increases. The decline is inevitable.

The present invention has been made in view of the above circumstances, and has as its object to provide a circuit board capable of trimming and adjusting the resistance value of a variable resistor electrically connected to the circuit board. To provide a method for adjusting the resistance value.

Another object of the present invention is to provide a circuit board provided with a variable resistor having a wiring structure capable of adjusting such a resistance value.

[0009]

In order to achieve the above object, according to the first aspect of the present invention, a series circuit of a variable resistor whose resistance value is trimmed and adjusted and a fixed resistor whose resistance value is known is provided. A constant current source is connected to both ends of the variable resistor while being connected to circuit components of the circuit board, and a voltage across the variable resistor, a resistance value of the fixed resistor and a voltage between both ends, and the constant current source The point is to trim the resistance value of the variable resistor while monitoring the resistance value of the variable resistor based on a current flowing to a connection point between the variable resistor and the fixed resistor.

According to a second aspect of the present invention, in the method for adjusting a resistance value of a circuit board according to the first aspect, the voltage across the variable resistor is V1, the resistance value of the fixed resistor is R1, and both ends of the fixed resistor are both ends. When the voltage is V2 and the current flowing from the constant current source to the connection point between the variable resistor and the fixed resistor is I, the resistance value Rx of the variable resistor is given by Rx = V1 /
The point is to monitor at (I-V2 / R1).

According to this method, even after a desired circuit is formed on the circuit board, the resistance value of the variable resistor can be accurately monitored without being affected by the combined resistance of the circuit components. Can be adjusted. Therefore, the productivity of the circuit board can be suitably improved.

The gist of the present invention is that a series circuit of a variable resistor whose resistance value is trimmed and adjusted and an arbitrary fixed resistor is connected to a circuit component.

According to such a configuration, even after a circuit is formed on the circuit board, a predetermined measuring system circuit for monitoring a resistance value is connected to the variable resistor and the fixed resistor of the circuit, thereby providing the circuit. The resistance value of the variable resistor can be accurately monitored without being affected by the combined resistance of the components.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a schematic diagram showing a method for adjusting a resistance value of a circuit board according to the present embodiment.

As shown in FIG. 1, a circuit board 10 includes a circuit element group 11, a variable resistor 12, and a variable resistor 12 which are circuit elements constituting a desired circuit made up of various elements. Connected in series with the resistor 12
, A closed circuit having a fixed resistor 13 functioning as a part of the resistance component. The variable resistor 12 includes, for example, a thick-film resistor formed on the circuit board 10 by printing or the like, a thin-film resistor formed by a CVD method or the like, a chip resistor, and the like. A resistor whose value is adjusted. The fixed resistor 13 is a resistor having a known resistance value such as a high-precision chip resistor having an error of about ± 0.1% to ± 0.3%.

On the other hand, a measuring system circuit 2 for monitoring the resistance value
Reference numeral 0 denotes a constant current source 21, an ammeter 22, and voltmeters 23 and 24, each of which is connected to a predetermined portion of the circuit board 10 in the manner shown in FIG. That is, one end of the constant current source 21 is connected to one end ((a) in the figure) of the variable resistor 12, and the other end of the identification current source 21 is connected to the other end of the variable resistor 12 via the ammeter 22. ((B) in the figure). Both ends of the voltmeter 23 are connected to both ends ((a) and (b) in the figure) of the variable resistor 12, and both ends of the voltmeter 24 are both ends of the fixed resistor 13 ((b) in the figure). And (c)).

Next, the variable resistor 1 in the circuit board 10 will be described.
2 will be described. FIG. 2 shows an equivalent circuit of the circuit board 10 and the resistance value measuring circuit 20 connected as described above. In FIG. 2, the resistance Rx indicates the resistance of the variable resistor 12, the resistance R1 indicates the resistance of the fixed resistor 13, and the resistance R2 indicates the combined resistance of the circuit element group 11.

As shown in FIG. 2, when the circuit board 10 is viewed from the constant current source 21, the fixed resistor 13 and the circuit element group 11 are connected in series. The constituent element group 11 and the variable resistor 12 are connected in parallel. Therefore, when a current I is supplied to the circuit from the constant current source 21, the voltage value V2 across the fixed resistor 13 is measured by the voltmeter 24. The current value i1 flowing through the fixed resistor 13 from the voltage V2
Is obtained (i1 = V2 / R1). The current I is measured by the ammeter 22, and the voltage V1 across the variable resistor 12 is measured by the voltmeter 23. Therefore, the resistance value Rx of the variable resistor 12 is obtained from these measured values (Rx = V1 / I-i1). That is, the resistance value Rx of the variable resistor 12 is obtained by the following equation. Rx = V1 / (I−V2 / R1) (1) As described above, in the configuration of the circuit board 10 and the method of adjusting the resistance value of the variable resistor 12, the resistance value of the variable resistor Rx is the combined resistance R2 of the circuit element group 11
Will be monitored without any effect from Therefore, based on the monitored resistance value Rx, the resistance value can be easily and accurately adjusted by, for example, well-known laser trimming.

The effects of this embodiment described in detail above are summarized below. A circuit element group 11, a variable resistor 12, and a fixed resistor 13 on a circuit board 10;
In the state where the circuit according to the above is connected, the resistance value of the variable resistor 12 can be monitored without being affected by the combined resistance of the circuit element group 11. Therefore, the management of the variable resistor 12 is easy and the circuit board 1
0 without increasing the number of manufacturing steps.

Since the trimming adjustment of the resistance value of the variable resistor 12 can be performed after the above circuits are connected, the degree of freedom of the manufacturing process layout (the process sequence in the manufacturing line and the layout of the manufacturing equipment associated therewith) is reduced. Can be expanded.

Also, the trimming-adjusted variable resistor 1
2 can be performed after the above circuits are connected. Therefore, the inspection of the resistance value and the like can be easily performed in the final step of the manufacturing line, and the inspection of the resistance value and the like can be easily performed even during maintenance.

When the fixed resistor 13 functions as a part of the resistance of the variable resistor 12 on the circuit board 10, trimming correction of the variable resistor 12 is performed by:
It can also be performed with higher accuracy. More specifically, for example, the required resistance value of the variable resistor 12 is 150 kΩ to 20 kΩ.
When the resistance is between 0 kΩ and 50 kΩ,
And a resistor of 150 kΩ is provided as the fixed resistor 13. As a result, the combined resistance value of both is 200
kΩ. If the variable resistor 12 is trimmed in this way, the resistance can be corrected between 150 kΩ and 200 kΩ. At this time, 200 k is used as the variable resistor 12.
Compared to the case where a resistor of Ω is used, the resistor of 50 kΩ allows finer adjustment of the resistance value, so that the trimming correction can be performed with higher accuracy.

In the above embodiment, a high-precision chip resistor having an error of about ± 0.1% to ± 0.3% is used as the fixed resistor 13, but this is, for example, ± 1% to ± 5%.
A low accuracy of about% error may be used. In short, even in the case of using such a low-precision resistor, the resistance value of the variable resistor 12 to be monitored can be monitored as long as the individual resistance value is measured in advance and the value is grasped. Can be known exactly.

[0024]

According to the first or second aspect of the present invention, even after a desired circuit is formed on a circuit board, the variable resistor is not affected by the combined resistance of the circuit components. Can be trimmed and adjusted while accurately monitoring the resistance value. Therefore, the productivity of the circuit board can be suitably increased.

According to the third aspect of the present invention, even after a circuit is formed on the circuit board, a predetermined measuring system circuit for monitoring a resistance value is connected to the variable resistor and the fixed resistor of the circuit. Thus, the resistance value of the variable resistor can be accurately monitored without being affected by the combined resistance of the circuit components.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a resistance value adjusting method of the present invention.

FIG. 2 is an equivalent circuit diagram of FIG.

FIG. 3 is an equivalent circuit diagram showing an example of a conventional resistance value adjusting method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Circuit board, 11 ... Circuit component group, 12 ... Variable resistor, 13 ... Fixed resistance, 20 ... Resistance value measurement system circuit.

Claims (3)

[Claims] 1. A series circuit comprising a variable resistor whose resistance value is trimmed and adjusted and a fixed resistor having a known resistance value is connected to a circuit component of a circuit board, and a constant current source is provided at both ends of the variable resistor. And the voltage across the variable resistor, the resistance value of the fixed resistor and the voltage across the fixed resistor, and a current flowing from the constant current source to a connection point between the variable resistor and the fixed resistor, A method for adjusting a resistance value of a circuit board, wherein the resistance value of a variable resistor is trimmed and adjusted while monitoring the resistance value. 2. The method according to claim 1, wherein the voltage across the variable resistor is V1, the resistance value of the fixed resistor is R1, the voltage across the fixed resistor is V2, and the constant current is constant. When a current flowing from a source to a connection point between the variable resistor and the fixed resistor is I, a resistance value Rx of the variable resistor
Is monitored by Rx = V1 / (I−V2 / R1). 3. A circuit board comprising a variable resistor, wherein a series circuit of a variable resistor whose resistance value is trimmed and adjusted and an arbitrary fixed resistor is connected to a circuit component.