JP2008135426A - Laser trimming method for resistor, and laser trimming apparatus used for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve precision in laser trimming, by determining the presence or the absence of microcracks generated in a laser pulse application section, in a laser trimming method of resistors. <P>SOLUTION: In the laser trimming method for adjusting the electrical resistance value of a resistor 10 by intermittently irradiating laser pulses 3, while measuring the electrical resistance value of the resistor 10, the electrical resistance value of the resistor 10, after applying the laser pulsees 3, is measured with DC and is compared with the target resistance value; the electrical resistance value is measured with AC at a prescribed frequency band; and frequency characteristics measured with AC are compared with those of the electrical resistance values that are registered in advance, to determine the irradiation of next laser pulses 3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a laser trimming method of a micro resistance chip having a size of 0603 or 0402 and a laser trimming apparatus used therefor.

  In the conventional laser trimming method, a laser pulse is intermittently irradiated to the resistor as the rest time T, and the irradiation position of the laser pulse is scanned on the resistor at a constant speed by a beam scanner. Therefore, the irradiation position (so-called byte size) of the continuous laser pulse determined by the processing speed and the pause time T is constant, and when the measured value such as the electrical resistance value exceeds the preset final target value Rf Then, the laser pulse irradiation was stopped and the laser trimming was finished.

As prior art document information relating to the invention of this application, for example, Patent Document 1 is known.
JP 2001-326112 A

  In the above conventional example, if the amount of change in the measured electrical resistance value that changes due to one laser pulse irradiation is ΔRt, the byte size is constant, and thus the electrical resistance value after the end of laser trimming varies in the range of Rf to Rf + ΔRt. So the accuracy was low.

  In view of this, a method has been developed in which the byte size is changed by changing the pause time T when the electric resistance value during trimming approaches the final target value, and the accuracy of laser trimming is increased. That is, the accuracy of laser trimming is improved by determining the rest time T by associating the difference ΔRfm between the final target value of electrical resistance and the measured value immediately after laser trimming with ΔRt.

  However, in the above method, since only the laser pulse irradiation pause time T is shortened, the laser pulse irradiation part is easily heated, and microcracks are easily generated. Therefore, since the amount of change in the electrical resistance value after laser pulse irradiation is large, the accuracy of laser trimming is low particularly in the case of a chip resistor having a small resistor area of 0603 size or 0402 size.

  Accordingly, an object of the present invention is to improve the accuracy of laser trimming of a micro resistance of 0603 size or 0402 size.

  In order to achieve the above object, the present invention provides a laser trimming method for adjusting an electrical resistance value of a resistor by intermittently irradiating a laser pulse while measuring the electrical resistance value of the resistor. The electrical resistance value of the resistor after irradiation is measured with a direct current and collated with a target resistance value, the electrical resistance value is measured with an alternating current in a predetermined frequency band, and the frequency characteristic measured with the alternating current Because it is a laser trimming method of a resistor that determines the irradiation of the next laser pulse by collating with the frequency characteristic of the registered electrical resistance value, by comparing the frequency characteristic by AC measurement with the target frequency characteristic, It is possible to determine whether a large microcrack has occurred in the laser trimming part and to determine the next laser pulse irradiation. It is possible to enhance the accuracy.

  In the laser trimming method of the present invention, the electrical resistance value of the resistor in the middle of laser trimming is measured with a direct current, measured with an alternating current in a predetermined frequency band, and the frequency characteristic is compared with a pre-registered target frequency characteristic. Thus, since it is determined whether or not a large microcrack is generated in the laser pulse irradiation portion and the next laser pulse irradiation is determined, the area of the resistor such as the 0603 size or 0402 size is small. There is an effect of increasing the precision of laser trimming of the chip resistance that is likely to occur.

  The laser trimming method of the present invention and the laser trimming apparatus used therefor will be described below with reference to the drawings.

  FIG. 1 is a configuration diagram of a laser trimming apparatus according to an embodiment of the present invention. The laser trimming apparatus is provided with a laser light source 1 that oscillates a laser pulse, and its output is controlled by a laser oscillation control circuit 2. On the output side of the laser light source 1, a galvanometer type laser beam scanner 4 that controls the optical path of the laser pulse 3 oscillated from the laser light source 1 is provided.

  Inside the galvanometer type laser beam scanner 4, the laser pulse 3 oscillated from the laser light source 1 is expanded by a beam expander 5 and then reflected in a predetermined direction by a scanner mirror 7 whose angle is controlled by a galvanometer 6. . The laser pulse 3 reflected by the scanner mirror 7 is converged by the f-θ lens 8 and reflected by the mirror 9 to irradiate a predetermined position of the resistor 10 for laser trimming.

  A plurality of probes 12 for measuring the resistance value of the resistor 10 are provided at the tip of the vertical drive mechanism 11, and the height of the resistor 10 is adjusted by the vertical drive mechanism 11, so that the resistor 10 can be contacted and separated. Do. The probe 12 is electrically connected to the DC resistance measuring device 13 and the AC resistance measuring device 14, and the probe 12 is brought into contact with the resistor 10 for the DC component and the AC component of the electrical resistance value of the resistor 10 during laser trimming. Can be measured.

  The electrical resistance value of the resistor 10 measured by the DC resistance measuring device 13 and the AC resistance measuring device 14 is output after being converted into an electrical signal and input to the calculator 15. The electrical signal output from the calculator 15 is input to the operation control device 16 and a control signal is output to the beam scanner control circuit 17. Based on the calculation result of the calculator 15, the beam scanner control circuit 17 controls the irradiation condition of the laser pulse 3 to the resistor 10 to control the trimming amount.

  Next, the laser trimming method of the present invention will be described with reference to FIG.

  In this embodiment, a laser trimming method of a so-called thick film resistor, in which a trace amount of bismuth or the like is added to ruthenium oxide and a glass material is added as a binder and fired, will be described.

  FIG. 2 shows a processing flow of the laser trimming method of the present invention. First, laser trimming is started (20), and the resistor 10 is carried into a predetermined position by an XY stage (21). Next, the irradiation position of the laser pulse 3 is determined at a predetermined position of the resistor 10 (22), and the measurement probe 12 is lowered by the vertical drive mechanism 11 and brought into contact with the external electrode of the resistor 10 (23). Then, the laser pulse 3 is irradiated to the resistor 10 (24), and the DC resistance measuring device 13 and the AC resistance measuring device 14 through the measurement probe 12 are used to measure the electrical resistance value of the resistor 10 at the direct current and the electrical current at the alternating current. The resistance value is measured (25), (26).

The measured electric resistance value at alternating current is calculated by the calculator 15 and output as the frequency characteristic ΔRF _n (27).

  Next, a difference between the direct current electric resistance value Rm of the resistor 10 measured by the direct current resistance measuring device 13 and the final adjustment target resistance value Rz is obtained (28). Here, when the difference Rz−Rm exceeds the predetermined resistance value R1, the laser pulse 3 is irradiated again. Before that, the target frequency characteristics registered in advance and the output by (27) are performed. The frequency characteristics of the resistor 10 thus compared are compared and verified. Then, based on the collation result, it is determined whether to irradiate the laser pulse 3 again (29). If the difference Rz−Rm is equal to or less than the predetermined resistance value R1, the irradiation of the laser pulse 3 is stopped and the laser trimming is finished (30).

Next, verification of frequency characteristics will be described. Each time the laser pulse 3 is irradiated, the electrical resistance value at DC is measured and the electrical resistance value is measured at AC (26), and the computing unit 15 calculates and obtains the frequency characteristic ΔRf _n shown in FIG. . ΔRf _n is a frequency characteristic after irradiation with n laser pulses.

Here, the measurement frequency is from several hertz to a maximum of several thousand kHz, and may be specifically defined by fluctuations in electrical resistance in the measured frequency band, or may be defined as a differential value dR / df of the frequency component. Good. In the example of FIG. 3, it is an example of the high-frequency characteristics ΔRf ₁ and ΔRf ₂ of the two resistors 10 and has an electric resistance value PV in the measurement frequency band.

The frequency characteristic to be verified is registered in advance in the calculator 15 as the target specification ΔRf. In the computing unit 15, the target specification ΔRf and the frequency characteristic ΔRf _n of the resistor 15 are compared to determine whether they are within a predetermined range (29). If it is within the predetermined range, it is determined that the generation of microcracks due to the laser pulse 3 is small, and the laser pulse 3 is irradiated again so that the adjustment target resistance value Rz is reached, and trimming is continued. On the other hand, if the frequency characteristic ΔRf _n of the resistor 10 exceeds the predetermined range with respect to the target specification ΔRf, it is determined that a microcrack has occurred, and the subsequent laser trimming is stopped.

Even when the frequency characteristic ΔRf _n of the resistor 10 exceeds a predetermined range with respect to the target specification ΔRf, the frequency characteristic ΔRf _n of the resistor 10 after the nth laser pulse irradiation and the (n + 1) th time If the frequency characteristic ΔRf _n−1 of the resistor 10 after the laser pulse irradiation is compared and there is a certain relationship, the trimming may be continued by correcting the adjustment target resistance value Rz.

As described above, since it is possible to determine the presence / absence of microcracks generated in the resistor 10 due to the irradiation of the laser pulse 3 from the frequency characteristic ΔRf _n obtained by measuring the electrical resistance value at the direct current as well as the electrical resistance value at the direct current. Since resistance drift after the end of laser trimming due to microcracks can be prevented, the accuracy of laser trimming can be improved as a result.

  The above example is an example in which the target frequency characteristic ΔRf is registered in advance, but the frequency characteristic ΔRf is measured before laser trimming of the resistor 10, and the target frequency characteristic ΔRf for each resistor 10 is measured. You may register. By setting individual target values as described above, it is possible to eliminate variations when the lot of the resistor 10 is changed.

  As described above, the presence or absence of microcracks in the resistor 10 can be determined from the frequency characteristics of the electrical resistance value after laser pulse irradiation. The amount of change in the electrical resistance value after laser pulse irradiation affects the internal structure of the resistor 10. Because it receives. FIG. 4 shows a schematic diagram of the resistor 10 after laser pulse irradiation. 4A is a schematic diagram of a laser pulse irradiation part of the resistor 10, and FIGS. 4B and 4C are schematic views of a cross section of the resistor 10 immediately below the laser pulse irradiation part.

  By irradiating the laser pulse, the laser pulse irradiating unit 31 is intermittently irradiated on the resistor 10 during the laser pulse irradiation time and the pause time T between them, and is scanned by the scanner mirror 7. Appears as shown in. A heat affected zone 32 and a microcrack 33 are generated around the laser pulse irradiation unit 31. The cross-sectional structure shown in FIG. 4B or FIG. 4C has a schematic structure immediately below the laser pulse irradiation unit 31 depending on the irradiation condition of the laser pulse 3.

  FIG. 4C shows an example in which the internal structure of the resistor 10 is greatly changed by the irradiation of the laser pulse 3. That is, segregation 37 such as bismuth, which is glass or a trace additive, is increased on ruthenium oxide 36, which is the main material, and microcracks 38 are generated from the surface. Accordingly, the path of the current I flowing through the resistor 10 is disturbed when energized, and as a result, the resistance change amount after the laser pulse 3 irradiation is increased.

  On the other hand, FIG. 4B shows an example in which the internal structure of the resistor 10 is hardly changed by the irradiation of the laser pulse 3. A binder 35 such as bismuth or glass as a trace additive is segregated by being dispersed in ruthenium oxide 34 which is a main material, and the path of current I is not disturbed when energized. Therefore, the resistance change after the laser pulse 3 irradiation is small and stable.

  As described above, since the influence on the resistor 10 due to the laser pulse 3 irradiation can be estimated from the frequency characteristics of the resistor 10 after the laser pulse 3 irradiation, the accuracy of laser trimming can be improved.

  In the laser trimming method according to the present invention, the electrical resistance value of the resistor in the middle of laser trimming is measured with a direct current and measured with an alternating current in a predetermined frequency band, and the frequency characteristic is compared with a target frequency characteristic registered in advance. Thus, it is determined whether or not a large microcrack is generated in the laser pulse irradiation portion, and the next laser pulse irradiation is determined. Therefore, the area of the resistor is small, and the 0603 size in which microcracks are easily generated This is useful for a trimming method of chip resistance such as 0402 size.

1 is a configuration diagram of a laser trimming apparatus according to an embodiment of the present invention. Processing flow diagram showing a laser trimming method according to an embodiment of the present invention The figure which shows an example of the frequency characteristic of the resistor by the said processing flow figure Schematic diagram showing the exterior and interior of the laser pulse irradiation part, (a) Schematic diagram of the laser pulse irradiation part, (b) Schematic diagram of the cross section of the resistor directly under the laser pulse irradiation part, (c) Directly under the laser pulse irradiation part Schematic diagram of cross section of resistor

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser light source 2 Laser oscillation control circuit 3 Laser pulse 9 Mirror 10 Resistor 11 Vertical drive mechanism 12 Measurement probe 13 DC resistance measuring instrument 14 AC resistance measuring instrument 15 Calculator

Claims (2)

A laser trimming method for adjusting an electric resistance value of a resistor by intermittently irradiating a laser pulse while measuring an electric resistance value of the resistor, wherein the electric resistance value of the resistor after the laser pulse irradiation is adjusted. In addition to measuring with DC and collating with the target resistance value, the electrical resistance value is measured with alternating current of a predetermined frequency band, the frequency characteristic measured with the alternating current, and the frequency characteristic of the electrical resistance value registered in advance A laser trimming method of a resistor that determines irradiation of the next laser pulse by comparing with A laser trimming device for adjusting an electrical resistance value of a resistor by intermittently irradiating a laser pulse while measuring an electrical resistance value of the resistor, laser oscillation means for intermittently oscillating the laser pulse; Optical system control means for controlling the path of the laser pulse, transport means for mounting a resistor and controlling its position, measurement means for measuring the electrical resistance value of the resistor, and trimming from the measurement data of the measurement means An arithmetic unit that calculates processing conditions, and the laser oscillation unit, the optical system control unit, the transport unit, the measurement unit, and the arithmetic unit are connected to the arithmetic unit to perform arbitrary trimming processing. Operation control means for adjusting the electrical resistance value, wherein the measuring means is a DC resistance measuring instrument, and an AC resistance measuring instrument that measures frequency characteristics in a predetermined frequency band, And checking the resistance value by the DC resistance measuring device and the target resistance value by the computing unit, and checking the frequency characteristic by the AC resistance measuring device and the target frequency characteristic registered in advance. A laser trimming device for a resistor that determines the irradiation of the next laser pulse.

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