JPS58182205A - Method of regulating resistance - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a resistance adjustment method, and more particularly to a method of cutting a part of a resistor of a chip resistor mounted on a wiring board to adjust its resistance value to a predetermined value.

2. Description of the Related Art Conventionally, in various electronic devices, a resistance device whose resistance value can be changed mechanically, such as a variable resistor or a semi-fixed resistor, has been used to adjust the voltage setting using a resistor. 1st
The figure shows an error amplification section of a DC-DC converter as an example. The DC output of the DC-DC converter is applied between the input terminals 2.4.
A resistor 6.8 and a variable resistor 10 are connected in series between them. The divided voltage formed by the resistor 6, the variable resistor 10, and the resistor 8 is applied to the non-inverting terminal (+) of the error amplifier 12, and the reference voltage as a comparison voltage is applied to the inverting terminal (-) of the error amplifier 12. is set by the power supply 14. That is, the DC voltage applied to the non-inverting terminal (+) of the error amplifier 12 is set to a desired value by adjusting and subtracting the variable resistor 10, and the variable resistor 10 is only used for one-time adjustment setting. , after setting, it is theoretically possible to change to a fixed resistance. Note that the output of the error amplifier 12 is input to another circuit not shown.

In such a circuit, the variable resistor 10 has mechanically movable parts, so its shape is larger than that of a fixed resistor such as a chip resistor, which causes the overall size of the device to increase, and its resistance value is It has drawbacks such as low stability due to changes over time. In particular, when using a small device to downsize the device, the resolution for determining the accuracy of setting the resistance value is lower than that of a large device, so the change over time is greater and the resistance value becomes unstable. The degree of change will increase, etc.
This causes deterioration in the functionality of the circuit. For this reason, devices with a relatively large shape are generally used in devices that require high resistance value accuracy.

An object of the present invention is to provide a resistance adjustment method in which a resistor of a chip resistor, which is originally used as a fixed resistor, is cut to change its resistance value and a predetermined voltage value etc. are set with high precision.

The present invention is characterized in that the resistor of a chip resistor connected to a wiring pattern on a wiring board is cut to adjust its resistance value to an optimum value.

Embodiments of the invention will be described in detail with reference to the drawings. FIG. 2 shows an error amplification section of a DC-DC converter embodying the present invention, and the same parts as in FIG. 1 are given the same reference numerals. A resistor 20.22 is connected between the input terminals 2.4, and at least one of the resistors 20.22 functions as a variable resistor to adjust its resistance value, so a conventional variable resistor is not used. Not yet. This resistance 20.2
The divided voltage formed at the connection point of 2 is applied to the non-inverting terminal (+) of the error amplifier 12, and the resistance value of each resistor 20, 22 is selected to be close to the optimum value.

The resistors 20 and 22 are chip resistors 2 of the form shown in FIG.
4 is used. This chip resistor 24 has a resistor 28 deposited on the upper surface of a ceramic substrate 26, and electrically connected to the ends of the resistor 28, and has a resistor 28 on both ends, upper and lower surfaces, and both end surfaces of the ceramic substrate 26. A terminal portion 30 made of a metal that can be soldered is formed. The resistor 28 on the upper surface of the ceramic substrate 26 can be partially or completely cut by sandblasting, laser processing, or the like.

FIG. 4 shows the connection of resistors 20 and 22 in the circuit of FIG. Wiring patterns 34, 36, and 38 are formed on the upper surface of the wiring board 32, and the resistor 20 made of the chip resistor 24 is formed on the upper surface of the wiring board 32 between the wiring pattern 34 and the wiring pattern 36 or 38.
．． 22 is fixed with adhesive and electrically connected to each wiring pattern 34, 36, 38 with solder 40.

Note that terminals 46 of an electrolytic capacitor 44 that penetrates the wiring board 32 are fixed with solder 40 and electrically connected between the wiring patterns 34 and 42.

The resistance adjustment method will be explained based on such a mounting state. That is, changing the resistance ratio of resistors 20.22 is the same as that of resistors 20.22.
22, or in some cases both resistors 28, are partially cut into a semicircular shape, for example, by a cutting means such as sandblasting or laser machining. 48 indicates the cut portion.

When the resistor 28 of the resistor 20 is cut in this way, the fifth
Resistor 28 in the width direction like the chip resistor 24 shown in the figure
The area through which current flows becomes smaller than before cutting, and the resistance value increases, so a desired voltage value can be set in the same way as when a conventional variable resistor is used.

In the case of the above circuit, the voltage set by the resistor 20.22 is relatively determined by the values of both resistors 20.22, so if the value of one resistor 20 is made too large, the voltage set by the other resistor 20.
A desired voltage value can be set by cutting the second resistor 28 in a similar manner as shown by the broken line 50 and adjusting the degree of cutting.

According to such a resistance adjustment method, the resistor 28 of the chip resistor 24, which is originally used as a fixed resistor, is connected to the wiring board 3.
Since the resistance value can be adjusted while the circuit is mounted on the circuit board 2 and while measuring the electrical characteristics of the circuit, the resistance value can be set with high accuracy and the circuit function can be adjusted to the highest level. Moreover, as a result of adjusting the resistance value of such a fixed resistor, unlike conventional variable resistors or semi-fixed resistors, the resistance value accuracy becomes higher, the size can be reduced, and there are no mechanical contact parts. Since there is no problem, it is possible to prevent inconveniences such as failures and characteristic deterioration. In particular, since sandblasting, laser processing, and other methods are used to cut the resistor 28, processing accuracy can be improved and any resistance value can be set without affecting adjacent elements. . In the case of the above embodiment, the case where the cut portion of the resistor 28 is made into a semicircular shape has been described, but when using laser processing, the same effect can be expected even if the continuous portion of the resistor 28 is cut. The cutting form is determined according to the size and shape of the resistor 28.

Further, in the above embodiment, the resistor 20.22 was configured as a trimming resistor, but the resistance ratio of the resistor 20.22 was set lower than the required output voltage, and only one resistor 20 was used.
A similar effect can be expected by trimming.

Further, as shown in FIG. 6, a trimming resistor 20.
By connecting fixing resistors 52 and 54 in parallel to 22, trimming can be facilitated and the accuracy of voltage setting can be improved. In other words, even if resistor 2B with a resistance of 20.22 is cut too much, by doing this, the resistance will be reduced to 5.
2.54 makes it possible to reduce changes in resistance value between terminals.

As explained above, according to the present invention, the resistor of a chip resistor originally used as a fixed resistor is cut to increase its resistance value, and a desired voltage value etc. can be set with high precision.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing the error amplification section of a DC-DC converter, Fig. 2 is a circuit diagram showing an embodiment of the present invention, Fig. 3 is an explanatory diagram of a chip resistor used to implement the invention, and Fig. 5 6 is an explanatory diagram showing an embodiment of the invention, and FIG. 6 is a circuit diagram showing an application example of the invention. 20.22...Resistor, 24...Chip resistor, 26
...Ceramic substrate, 28...Resistor, 32...
wiring board.

Claims (1)

[Claims] (11) A resistance adjustment method characterized by cutting a resistor of a chip resistor connected to a wiring pattern on a wiring board and adjusting its resistance value to a predetermined value. T2) The above-mentioned 2. The resistance adjustment method according to claim 1, wherein the resistance value of the chip resistor is adjusted by cutting a part of the resistor formed in layers on a ceramic substrate using a cutting means. (3) The resistance adjustment method according to claim 2, wherein the cutting means is performed by sandblasting or laser processing.