JP4908253B2 - Bias adjustment method - Google Patents

Description

  The present invention relates to a bias adjustment method for a bias circuit using an adjustable impedance element having an impedance adjustment unit capable of adjusting impedance by laser irradiation, for example, a trimmable resistor.

  For adjustable semiconductor devices such as bipolar transistors and field-effect transistors (hereinafter referred to as FETs) using a trimmable resistor having an impedance adjusting unit capable of adjusting impedance by conventional laser irradiation, such as a trimming resistor Since the bias adjustment method of the bias circuit is an irreversible reaction in which the resistance value of the trimmable resistor is changed by laser irradiation, the bias can only be adjusted to increase or decrease when one trimmable resistor is used. . Therefore, in order to be able to adjust the bias in both the increasing and decreasing directions, it is necessary to use two trimmable resistors per one bias circuit (see, for example, Patent Document 1).

JP 11-261132 A (paragraph number 0020 and FIG. 1)

  In such a bias adjustment method, characteristics such as current and gain are non-linear with respect to a bias voltage in a semiconductor element, particularly an FET, and the characteristics vary widely among the elements, and various characteristics with respect to the amount of change in the bias voltage. The amount of change in characteristics is difficult to predict. For this reason, it is difficult to adjust various characteristics within a desired range only by changing the bias voltage in one direction. In order to return the characteristics, the bias voltage can be changed in the reverse direction. It was necessary to have two trimmable resistors per bias circuit. In this case, since two expensive trimmable resistors are used, the cost of the product cannot be avoided.

  In addition, when it is necessary to adjust the bias voltage in the direction opposite to the conventional direction, it is necessary to irradiate the other trimmable resistor with a laser. Therefore, in a device using one general laser light source, Recognition and movement for changing the irradiation position is necessary. In particular, in a circuit unit including a bias circuit using a plurality of trimmable resistors, when the characteristics are determined by the correlation of each semiconductor element to which the bias voltage is applied, the bias voltage once determined needs to be adjusted again In this case, it is necessary to return to the original irradiation position and irradiate, and the control of the device becomes complicated due to the recognition of the irradiation position and the increase in the number of movements. There was a problem such as becoming higher.

  The present invention has been made in order to solve the above-described problems, and is an electrical circuit for an electronic circuit including a bias circuit using an adjustable impedance element having an impedance adjustment unit capable of adjusting impedance by laser irradiation. It is an object of the present invention to provide a bias adjustment method capable of easily adjusting a characteristic to a desired characteristic.

In the bias adjustment method according to the present invention, the impedance adjustment unit is irradiated with laser with the electrical characteristics of an electric circuit including a bias circuit that has an adjustable impedance element provided with an impedance adjustment unit and applies a bias value to a biased target. A bias adjustment method for adjusting to a desired characteristic by:
The adjustable impedance element is a trimmable resistor having a trimmable part, and the bias circuit is a series circuit of a trimmable resistor and a fixed resistor, and a voltage between terminals of the fixed resistor is given as a bias value.
Connect the external circuit for adjustment to the electrical circuit in advance, connect the external power supply of the external circuit for adjustment to the bias circuit, and change the characteristics of the external circuit for adjustment, thereby changing the bias value to obtain the desired electrical The bias value when the characteristic is obtained is stored as a bias target value,
After removal of the external power source of the adjustment for the external circuit, have rows of laser irradiation to the impedance adjuster as bias value becomes the bias target value, trims the trimmable portion of the trimmable resistor, then adjusting the external circuit from the electrical circuit Is to be removed .

In the bias adjustment method according to the present invention, the impedance adjustment unit is irradiated with laser with the electrical characteristics of an electric circuit including a bias circuit that has an adjustable impedance element provided with an impedance adjustment unit and applies a bias value to a biased target. A bias adjustment method for adjusting to a desired characteristic by:
The adjustable impedance element is a trimmable resistor having a trimmable part, and the bias circuit is a series circuit of a trimmable resistor and a fixed resistor, and a voltage between terminals of the fixed resistor is given as a bias value.
Connect the external circuit for adjustment to the electrical circuit in advance, connect the external power supply of the external circuit for adjustment to the bias circuit, and change the characteristics of the external circuit for adjustment, thereby changing the bias value to obtain the desired electrical The bias value when the characteristic is obtained is stored as a bias target value,
After removal of the external power source of the adjustment for the external circuit, have rows of laser irradiation to the impedance adjuster as bias value becomes the bias target value, trims the trimmable portion of the trimmable resistor, then adjusting the external circuit from the electrical circuit Because it is something to remove
When adjusting the impedance by laser irradiation, laser irradiation may be performed so that the bias value becomes the bias target value. Therefore, it is easy to adjust the impedance, and there is no risk that the impedance will be adjusted excessively, resulting in a defective product.

Embodiment 1 FIG.
1 to 6 show a first embodiment for carrying out the present invention. FIG. 1 is a block diagram of a trimming apparatus, and FIG. 2 is a block diagram of a circuit unit of FIG. FIG. 3 is a connection diagram between the external power supply and the circuit unit of FIG. 1, and FIG. FIG. 5 is an equivalent circuit diagram of the external power supply and circuit unit of FIG. 3, and FIG. 6 is a characteristic diagram showing the relationship between the voltage and bias voltage of the external variable voltage source of FIG. First, the configuration of the target bias circuit will be described with reference to FIG. In FIG. 2, the bias circuit 20 is constituted by a series circuit in which a trimmable resistor 21 is connected in series with a fixed resistor 22 via a connection point 23, and the trimmable resistor 21 side of the bias circuit 20 is connected to a power source (not shown). The fixed resistor 22 side is grounded, and a connection point (bias point) 23 is connected to the FET 24 to give a bias voltage. The trimmable resistor 21, the fixed resistor 22, and the FET 24 are mounted on the circuit board 13a and constitute a circuit unit 13 as an electric circuit. The trimmable resistor 21 has a trimming portion such as a thick film resistor, a thin film resistor, or a metal that is trimmed by laser irradiation (not shown). Further, the trimmable resistor 21 is an adjustable impedance element and a trimmable element having an impedance adjustment unit capable of adjusting impedance by laser irradiation in the present invention.

  Next, the configuration of the trimming apparatus will be described with reference to FIG. In FIG. 1, a laser irradiation apparatus 11 having a laser irradiation head 11 a is provided in the trimming apparatus, and a circuit unit 13 is placed on a stage 12. One or both of the laser irradiation head 11a and the stage 12 can be moved so that the laser irradiation position can be moved. In addition, an external power source 14 as an external circuit for adjustment, a voltage measuring device 15, a circuit characteristic measuring device 16, and a storage device 17 are prepared. The external power supply 14 has a variable output voltage, is connected to a connection point 23 (FIG. 2) of the bias circuit 20, and changes a bias voltage that is a voltage between both terminals of the fixed resistor 22. The voltage measuring instrument 15 measures the bias voltage. The circuit characteristic measuring instrument 16 measures the characteristic of the circuit unit 13 when the bias voltage is changed by controlling the external power supply 14. The storage device 17 stores the bias voltage measured by the voltage measuring instrument 15 when the characteristic of the circuit unit 13 becomes a desired characteristic.

  As shown in FIG. 3, the external power source 14 has a variable voltage source 31, a series resistor 32, and a probe 33, and when applying a bias to the connection point 23, the probe 33 is brought into contact with the connection point 23. The voltage is applied through the series resistor 32.

Next, the procedure of bias adjustment will be described based on the flowchart of FIG.
Step S11. The circuit unit 13 is placed on the stage 12.
Step S12. The stage 12 is moved, and the position of the trimming part (not shown) of the trimmable resistor 21 of the circuit unit 13 and the laser irradiation head 11a are aligned.
Step S13. The probe 33 of the external power supply 14 is brought into contact with the connection point 23 of the bias circuit 20.
Step S14. While the bias voltage is changed by changing the voltage supplied from the external power supply 14 and the characteristics of the circuit unit 13 are measured by the circuit characteristic measuring device 16, the bias voltage is changed until a desired characteristic is obtained.
Step S15. The bias voltage Vg0 when a desired characteristic is obtained is measured by the voltage measuring device 15, and stored as a bias target value in the storage device 17.
Step S16. The probe 33 of the external power supply 14 is disconnected from the connection point 23 of the bias circuit 20.
Step S17. An internal power supply (not shown) is connected to the circuit unit 13.
Step S18. While the voltage measuring device 15 measures the voltage (bias voltage) at the connection point 23 of the bias circuit 20, the trimming portion of the trimmable resistor 21 is irradiated with laser, and the trimming portion is trimmed until the bias voltage becomes Vg0.

Here, when a bias voltage is applied to the bias circuit 20 using the external power supply 14 as shown in FIG. 3, the bias voltage is as follows. FIG. 5 is an equivalent circuit of the external power supply 14 and the bias circuit 20, and the resistance value of the trimmable resistor 21 of the bias circuit 20 is R 2, the resistance value of the fixed resistor 22 is R 1, and the series resistance connected in series to the variable voltage source 31. When the resistance value of 32 is R3, the voltage Vg at the connection point 23 with respect to the voltage Vx of the variable voltage source 31 is as follows.
Vg = {1 / (1 / R1 + 1 / R2 + 1 / R3)} (Vx / R3 + V / R1)

  FIG. 6 is a graph showing the characteristics of the voltage Vx of the variable voltage source 31 and the bias voltage Vg (at the connection point 23), and the characteristics are linear. That is, the change amount of the voltage Vg at the connection point 23 with respect to the change amount of the voltage Vx is constant over the entire range of the voltage Vx output from the variable voltage source 31. Therefore, in the voltage Va and the voltage Vb of the variable voltage source 31, the amounts of change ΔV1 and ΔV2 of the respective biases when the voltage is changed by ΔVx are equal. This is because, when a variable voltage source whose minimum voltage change amount (voltage resolution) can be automatically controlled to be constant in all voltage ranges, for example, a power source using a D / A converter, what value is the voltage Vx? However, the adjustment resolution of the bias voltage Vg does not deteriorate.

As described above, according to this embodiment, even when it is difficult to predict a bias value to be adjusted in order to obtain a desired characteristic due to nonlinear characteristics and characteristic variations of a semiconductor element such as the FET 24 to which the bias circuit 20 is connected. The bias voltage Vg0 having the desired characteristics is determined in advance by the circuit unit 13 and stored as a bias target value. During trimming by laser irradiation, the bias value becomes the bias target value Vg0 while measuring the bias voltage Vg. Further, trimming can be performed by controlling the laser irradiation device 11. Therefore, trimming is easy, and there is no possibility that trimming of the trimmable resistor 21 will be excessively performed, resulting in a defective product.
Further, the change of the bias voltage is linear with respect to the voltage supplied from the variable external power supply 14 which is an external circuit, and a predetermined adjustment accuracy can be obtained regardless of the value of the bias voltage.

Embodiment 2. FIG.
FIG. 7 is a flowchart showing a procedure of bias adjustment according to the second embodiment. This embodiment shows a bias adjustment method in the case where a circuit unit includes a plurality of bias circuits having one trimmable resistor. When the circuit unit 13 includes first and second bias circuits each having a trimmable resistor, a part of the bias adjustment procedure in the first embodiment is changed as follows.
Step S21. An external power supply having a probe capable of independently outputting the first and second voltages is prepared, and the probe is connected to the first and second bias circuits.
Step S22. The first and second bias voltages of the first and second bias circuits are set to predetermined minimum values, respectively.
Step S23. The characteristic of the circuit unit is measured with a circuit characteristic measuring device by changing the first bias voltage applied to the connection point of the first bias circuit.
Step S24. It is determined whether a desired characteristic is obtained in the circuit unit. If the desired characteristics are not obtained, the process proceeds to step S25. When the desired characteristics are obtained, the process proceeds to step S26.
Step S25. The second bias voltage of the second bias circuit is increased by a predetermined value, the process returns to step S23, steps S23 and S24 are repeated, and if a desired characteristic is obtained in the circuit unit in step S25, the process proceeds to step S26.
Step S26. The first bias voltage Vg10 and the second bias voltage Vg20 when desired characteristics are obtained in the circuit unit are stored as respective bias target values.

If the first and second trimmable resistors are adjusted based on the first and second bias voltages Vg10 and Vg20 thus obtained, desired circuit characteristics can be easily obtained in the circuit unit. The same can be done when there are three or more bias circuits.
Prior to step S22, a circuit unit is placed on the stage. Further, the alignment of the trimming portion of the first trimmable resistor of the circuit unit and the laser irradiation head may be performed either before step S21 or after step S26. Then, the first trimmable resistor is irradiated with a laser to perform trimming until the first bias voltage becomes Vg10, and then the second trimmable resistor is irradiated with a laser until the second bias voltage becomes Vg20. Perform trimming.

  As described above, when the circuit unit includes the first and second bias circuits, when the desired electrical characteristics are determined from the correlation of the electrical characteristics of the semiconductor element (FET), the direct laser is used as in the related art. If the bias voltage needs to be changed again for the FET whose bias voltage has already been determined, it is necessary to re-recognize and move the laser irradiation position. . On the other hand, in this embodiment, the first and second bias voltages Vg10 and Vg20 at which desired characteristics are obtained in the circuit unit by changing the first and second bias voltages by the external power source are determined and biased. Since the trimmable resistor is trimmed so that the laser irradiation becomes the first and second bias voltages Vg10 and Vg20 stored, the bias voltage is again applied to the FET once the bias voltage has been determined. There is no need to change. Therefore, the laser irradiation process is facilitated. Furthermore, since the bias voltage can be adjusted by a change in only one direction by setting the initial value of the trimmable resistor to an appropriate value that allows for variations in semiconductor elements, the adjustment process (steps S23 to S25 above) is facilitated. Since only one expensive trimmable resistor per bias circuit need be used, the circuit unit can be reduced in cost.

Embodiment 3 FIG.
FIG. 8 is a configuration diagram of a bias setting apparatus according to the third embodiment. In FIG. 8, the bias setting device 50 includes a series resistor 53, a D / A converter 54, an A / D converter 55, a storage device 57, and a control device 59. A D / A converter 54 as an external circuit is used in place of the external power supply 14 in FIG. 1, and an A / D converter 55 is used in place of the voltage measuring device 15. Obtained from a circuit characteristic measuring instrument (not shown) (see circuit characteristic measuring instrument 16 in FIG. 1) for supplying a bias voltage to the FET 24 from the D / A converter 54 via the series resistor 53 and measuring the characteristics of the circuit unit 13 (FET 24). The characteristic value and the adjustment target value are compared by the control device 59, and the output voltage of the D / A converter 54 is determined and output. By repeating this, when the characteristics of the circuit unit 13 satisfy the adjustment target value, the A / D converter 55 acquires the bias voltage at that time and stores it in the storage device 57. When there are a plurality of bias circuits, when the characteristics of all the bias circuits satisfy the adjustment target value, each bias voltage is sent to the laser irradiation device 11 and set to the target bias voltage by laser irradiation.

  According to this embodiment, the change in the bias voltage is linear with respect to the voltage supplied from the D / A converter 54 which is an external circuit, and a predetermined adjustment accuracy can be obtained regardless of the value of the bias voltage. In addition, the bias voltage can be easily adjusted because the control device 59 automatically obtains the bias voltage that satisfies the characteristics required by the circuit unit 13.

Embodiment 4 FIG.
9 to 11 show the fourth embodiment. FIG. 9 is a connection diagram of an external circuit and a circuit unit. FIG. 10 is an equivalent circuit diagram of the external circuit and the circuit unit of FIG. FIG. 9 is a characteristic diagram illustrating a relationship between a resistance value of a variable resistor 9 and a bias voltage. In FIG. 9, a variable resistor 61 as an external circuit is connected in parallel with the fixed resistor 22 of the bias circuit 20.

The equivalent circuit of FIG. 9 is as shown in FIG. In FIG. 10, when the resistance value of the variable resistor 61 is Rx, the voltage at the connection point 23 is Vg, the bias voltage of the circuit unit 13 is V, the resistance value of the fixed resistor 22 is R1, and the resistance value of the trimmable resistor 21 is R2. Is an equivalent circuit. Then, when one terminal of the variable resistor 61 is connected to the connection point 23 as shown in FIG. 9 and the resistance value of the variable resistor 61 is changed, the voltage Vg at the connection point 23 with respect to the resistance value Rx of the variable resistor 61 is It is expressed by the following formula.
Vg = [R2 / {(R1 / R2 / Rx) + R1 + R2}] V
That is, the characteristic of the voltage Vg at the connection point 23 with respect to the resistance value Rx of the variable resistor 61 is a graph as shown in FIG. 11, and the amount of change in the voltage Vg at the connection point 23 varies depending on the resistance value Rx of the resistor 61.

  That is, in FIG. 11, when the resistance value Rx is changed by ΔRx with the resistance value Ra as the center, the change amount Δv1 of the voltage Vg is increased by the same ΔRx with the resistance value Rb as the center. Is larger than the change amount Δv2 of the voltage Vg. When ΔRx is the minimum change amount that can be adjusted, the resistance value Rb changes Vg more greatly than the resistance value Ra, and the adjustment resolution deteriorates. However, even if the adjustment resolution is lowered, it is sufficient to prepare the variable resistor 61 as an external circuit, so that it can be used as a simple external circuit.

  In each of the embodiments described above, the case of a trimmable resistor has been described as an example of an adjustable impedance element having an impedance adjustment unit capable of adjusting the impedance by laser irradiation. The same effect can be obtained even with a capacitor whose capacitance is changed by irradiation or the like. In addition, the electric circuit is not limited to the circuit unit described above, and the same effect can be obtained even if it is a hybrid IC or the like. The bias may be a current.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram of the trimming apparatus which is Embodiment 1 of this invention. It is a block diagram of the circuit unit of FIG. FIG. 2 is a connection diagram between an external power source and a circuit unit in FIG. 1. 2 is a flowchart showing a procedure for bias adjustment in the bias value setting device of FIG. 1. FIG. 4 is an equivalent circuit diagram of the external power supply and circuit unit of FIG. 3. FIG. 6 is a characteristic diagram showing the relationship between the voltage of the variable voltage source of FIG. 5 and the bias voltage. It is a flowchart which shows the procedure of the bias adjustment which is Embodiment 2 of this invention. It is a block diagram of the bias value setting apparatus which is Embodiment 3 of this invention. It is a connection diagram of the external circuit and circuit unit which are Embodiment 4 of this invention. FIG. 10 is an equivalent circuit diagram of the external circuit and circuit unit of FIG. 9. FIG. 10 is a characteristic diagram showing the relationship between the resistance value of the variable resistor of FIG.

Explanation of symbols

11 laser irradiation device, 11a laser irradiation head, 12 stage,
13 circuit unit, 13a circuit board, 14 external circuit, 15 voltage measuring instrument,
16 circuit characteristic measuring device, 17 storage device, 21 trimmable resistor, 22 fixed resistor,
23 connection points, 24 FETs, 31 variable voltage sources, 32 resistors, 33 probes,
50 bias setting device, 53 series resistance, 54 D / A converter,
55 A / D converter, 57 storage device, 59 control device, 61 variable resistance.

Claims (3)

A bias that has an adjustable impedance element provided with an impedance adjustment unit and adjusts the electrical characteristics of an electric circuit including a bias circuit that applies a bias value to a biased target to a desired characteristic by irradiating the impedance adjustment unit with laser. An adjustment method,
The adjustable impedance element is a trimmable resistor having a trimmable part, and the bias circuit is a series circuit of the trimmable resistor and a fixed resistor, and a voltage between terminals of the fixed resistor is given as the bias value,
Previously, connect the external circuit adjusted to the electric circuit, by connecting the external power supply of the adjustment external circuit to the bias circuit, by changing the characteristics of the trimmer external circuit, varying the bias value And storing the bias value when the desired electrical characteristics are obtained as a bias target value,
After removing the external power source of the trimmer external circuit, the bias value have lines the laser irradiating the impedance adjuster to be the bias target value, trims the trimmable portion of the trimmable resistor, And a bias adjusting method for removing the adjusting external circuit from the electric circuit . The bias adjustment method according to claim 1, wherein the bias circuit includes one adjustable impedance element, and the electric circuit includes a plurality of the bias circuits. The bias value of the bias circuit is a voltage, and the external power supply of the external circuit for adjustment is connected to the bias circuit via a series resistor, and the bias value is changed by changing the voltage supplied to the bias circuit. The bias adjustment method according to claim 1 , wherein the bias adjustment method is performed.

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