Ultrasonic bonding device and method for temperature sensor

Abstract

To provide an ultrasonic bonding device and an ultrasonic bonding method for a temperature sensor which prevent damage to an insulating film.SOLUTION: A device 1 for ultrasonic bonding a pair of pattern wires 4 and a pair of lead frames 6 to a temperature sensor body 5 including an insulating film 2, a heat sensitive element 3 provided on the upper surface of the insulating film 2, and the pair of pattern wires 4 that are formed on the upper surface of the insulating film 2 and are connected to the heat sensitive element 3 includes: an anvil 7 where the temperature sensor body 5 is mounted on the upper surface with the insulating film 2 arranged below; and an ultrasonic horn 8 for applying a load to the pair of lead frames 6 mounted on the pair of pattern wires 4, and applying ultrasonic vibration to the lead frames 6 and bonding the pattern wires 4 and the lead frames 6, in which a surface that is the upper surface of the anvil 7 and directly under at least the ultrasonic horn 8 is a flat surface.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an ultrasonic bonding apparatus and method for bonding a lead frame to a temperature sensor body using an insulating film. [Background technology]

[0002] Conventionally, a temperature sensor using an insulating film such as polyimide resin as a substrate has been known as a temperature sensor for measuring the temperature of a heating roller or the like used in a copying machine or a printer. For example, Patent Document 1 describes a temperature sensor for measuring the temperature of a heating roller or the like used in a copying machine or a printer, the temperature sensor including an insulating film, a thermal element provided on the insulating film, a pair of pattern wirings connected to the thermal element on the insulating film, and a pair of lead frames connected to the pair of pattern wirings. In this temperature sensor, the lead frame is bonded to the pattern wiring mainly by soldering. As a method for joining lead frames, other joining methods such as ultrasonic joining using an ultrasonic joining device (see, for example, Patent Document 2) are also being considered. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-145655 A [Patent Document 2] JP 2019-188405 A Summary of the Invention [Problem to be solved by the invention]

[0004] The above conventional techniques still have the following problems. That is, when the lead frame and the pattern wiring are connected by soldering, there is a risk of solder cracks (deterioration) due to heat cycles, and there are also problems such as heat being applied by solder reflow (thermal history) and difficulty in controlling the solder shape. For this reason, as described above, other joining methods, particularly ultrasonic joining, for joining the lead frame and the pattern wiring are being considered. However, in the conventional ultrasonic joining, as shown in FIG. 5, the work fixing surface of the anvil 107 is provided with projections and recesses so that it bites into the resin film 2 of the work and fixes it, which causes damage such as holes in the insulating film 2.

[0005] The present invention has been made in consideration of the above-mentioned problems, and has an object to provide an ultrasonic bonding apparatus and an ultrasonic bonding method for a temperature sensor that are less likely to damage an insulating film. [Means for solving the problem]

[0006] The present invention employs the following configuration to solve the above problems. That is, an ultrasonic bonding device for a temperature sensor according to a first invention is a device for ultrasonically bonding a pair of pattern wirings and a pair of lead frames to a temperature sensor main body having an insulating film, a heat-sensitive element provided on the upper surface of the insulating film, and a pair of pattern wirings formed on the upper surface of the insulating film and connected to the heat-sensitive element, the device comprising an anvil on which the temperature sensor main body is placed with the insulating film facing down, and an ultrasonic horn that applies a load to the pair of lead frames placed on the pair of pattern wirings and applies ultrasonic vibrations to bond them, and the upper surface of the anvil, at least directly below the ultrasonic horn, is flat.

[0007] In this ultrasonic bonding device for temperature sensors, the top surface of the anvil, at least directly below the ultrasonic horn, is flat. Since the fixing surface of the anvil for the insulating film is flat, the insulating film is less likely to be damaged, and a good bonding condition can be obtained.

[0008] The ultrasonic bonding device for a temperature sensor according to the second invention is characterized in that, in the first invention, it is provided with a pressing portion that presses down the insulating film from above at a position avoiding the heat-sensitive element and the pattern wiring. In other words, this ultrasonic bonding device for temperature sensors is equipped with a pressing section that presses down on the insulating film from above at a position that avoids the heat-sensitive element and pattern wiring, so that the insulating film can be stably fixed without damaging the heat-sensitive element and pattern wiring, and positional deviation during ultrasonic bonding can be suppressed.

[0009] The ultrasonic bonding device for a temperature sensor according to the third invention is characterized in that, in the second invention, the pressing portion is formed in a U-shape surrounding the heat-sensitive element of the temperature sensor body placed on the upper surface of the anvil and pressing down the outer edge portion of the insulating film. That is, in this ultrasonic bonding device for temperature sensors, the pressing portion is formed in a U-shape surrounding the heat-sensitive element and presses the outer edge of the insulating film, so that the outer edge of the insulating film can be more stably fixed around the heat-sensitive element, making it possible to further suppress misalignment.

[0010] The ultrasonic bonding device for a temperature sensor according to the fourth invention is characterized in that, in any of the first to third inventions, a plurality of suction ports are formed on the upper surface of the anvil and can suck in the insulating film placed on the upper surface of the anvil, and the plurality of suction ports are arranged to avoid the bonding portions between the pair of pattern wirings and the pair of lead frames. That is, in this ultrasonic bonding device for temperature sensors, multiple suction ports are positioned to avoid the joints between a pair of pattern wirings and a pair of lead frames, so that the insulating film can be sucked in from below by the suction ports and fixed in place without affecting the joints.

[0011] The ultrasonic bonding device for a temperature sensor according to the fifth invention is characterized in that, in the fourth invention, at least one of the multiple suction ports is arranged directly below the heat-sensitive element of the temperature sensor body placed on the upper surface of the anvil. That is, in this ultrasonic bonding device for temperature sensors, at least one of the multiple suction ports is positioned directly below the heat-sensitive element of the temperature sensor body which is placed on the upper surface of the anvil. Therefore, by sucking directly below the heat-sensitive element which cannot be pressed down from above, the portion of the insulating film directly below the heat-sensitive element can also be stably fixed.

[0012] The ultrasonic bonding method for a temperature sensor according to the sixth invention is an ultrasonic bonding method for a temperature sensor that bonds the pair of pattern wirings of the temperature sensor body and the pair of lead frames by using an ultrasonic bonding apparatus for a temperature sensor of any of the first to fifth inventions, and includes a placing step of placing the temperature sensor body on an upper surface of the anvil, and an ultrasonic bonding step of applying a load with the ultrasonic horn to the pair of lead frames placed on the pair of pattern wirings and applying ultrasonic vibrations to bond them, and is characterized in that the upper surface of the anvil directly below the ultrasonic horn is a flat surface. That is, in this ultrasonic bonding method for a temperature sensor, the upper surface of the anvil directly below the ultrasonic horn is flat, so that the insulating film is less likely to be damaged and a good bond can be obtained.

[0013] The ultrasonic bonding method for a temperature sensor according to the seventh invention is characterized in that, in the sixth invention, it includes a film roughening step of roughening the lower surface of the insulating film by blasting before the placement step. In other words, this ultrasonic bonding method for a temperature sensor includes a film roughening process in which the underside of the insulating film is roughened by blasting beforehand prior to the placement process, thereby increasing the frictional resistance of the underside of the insulating film and making it less likely to slip during bonding. Effect of the Invention

[0014] According to the present invention, the following effects are obtained. In other words, according to the ultrasonic bonding device and ultrasonic bonding method of the present invention, the upper surface of the anvil, at least directly below the ultrasonic horn, is flat, and since the fixing surface of the anvil for the insulating film is flat, the insulating film is less likely to be damaged, and a good bonding condition can be obtained. Therefore, the ultrasonic bonding device and ultrasonic bonding method of the present invention can reduce the number of components and improve reliability by eliminating the need for solder, while also significantly reducing damage to the insulating film and achieving fast response and high reliability of the temperature sensor due to excellent adhesion. [Brief description of the drawings]

[0015] [Figure 1] 1 is a schematic configuration diagram showing an ultrasonic bonding device according to an embodiment of the ultrasonic bonding device and ultrasonic bonding method of the present invention; [Diagram 2] 5A is a plan view showing the position of a pressing portion when a lead frame is joined to a temperature sensor body in the present embodiment, and FIG. 5B is a cross-sectional view taken along line AA. [Diagram 3] 1 is a perspective view showing a temperature sensor to which a lead frame is connected in the present embodiment; [Figure 4] 4A and 4B are backside images showing the bonded portion between the pattern wiring on the insulating film and the lead frame, which are bonded by the conventional example (a) and the embodiment (b) of the ultrasonic bonding device and the ultrasonic bonding method according to the present invention. [Diagram 5] FIG. 1 is a schematic configuration diagram showing an ultrasonic bonding device in a conventional example of the ultrasonic bonding device and ultrasonic bonding method according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an ultrasonic bonding apparatus and an ultrasonic bonding method according to the present invention will be described with reference to Fig. 1 to Fig. 3. Note that in some of the drawings used in the following description, the scale is appropriately changed as necessary to make each part recognizable or easily recognizable.

[0017] As shown in Figures 1 and 2, the ultrasonic bonding device 1 of this embodiment is a device that ultrasonically bonds a pair of pattern wirings 4 and a pair of lead frames 6 to a temperature sensor body 5 that includes an insulating film 2, a heat-sensitive element 3 provided on the upper surface of the insulating film 2, and a pair of pattern wirings 4 formed on the upper surface of the insulating film 2 and connected to the heat-sensitive element 3.

[0018] The ultrasonic bonding apparatus 1 of this embodiment includes an anvil 7 on which the temperature sensor body 5 is placed with the insulating film 2 facing down, and an ultrasonic horn 8 that applies a load to a pair of lead frames 6 placed on a pair of pattern wirings 4 and applies ultrasonic vibrations to bond them. The upper surface of the anvil 7, at least directly below the ultrasonic horn 8, is made flat.

[0019] The ultrasonic bonding device 1 also includes a pressing portion 9 that presses the insulating film 2 from above at a position avoiding the heat-sensitive element 3 and the pattern wiring 4. As shown in FIG. 2, the pressing portion 9 is formed in a U-shape surrounding the thermal element 3 of the temperature sensor main body 5 placed on the upper surface of the anvil 7, and is configured to press down the outer edge of the insulating film 2. In Fig. 2(a), the region 9a where the pressing portion 9 presses down the insulating film 2 is hatched. Also, the joint portion 4b between the lead frame 6 and the pattern wiring 4 is hatched. Furthermore, in Fig. 2(a), the position of the suction port 10a when placed on the anvil 7 is also shown by a dashed line.

[0020] A plurality of suction ports 10a capable of sucking the insulating film 2 placed on the upper surface of the anvil 7 are formed in the upper surface of the anvil 7 and open thereon. The plurality of suction ports 10 a are arranged so as to avoid the joint portions 4 b between the pair of pattern wirings 4 and the pair of lead frames 6 . At least one of the plurality of suction ports 10a is disposed directly below the heat sensitive element 3 of the temperature sensor main body 5 placed on the upper surface of the anvil . A suction source 10 such as a vacuum pump is connected to the plurality of suction ports 10a.

[0021] The insulating film 2 is formed in a strip shape from a polyimide resin sheet having a thickness of, for example, 7.5 to 125 μm. The insulating film 2 can also be made from other materials such as PET (polyethylene terephthalate) and PEN (polyethylene naphthalate), but for measuring the temperature of a heating roller, a polyimide film is preferable because the maximum operating temperature is as high as 230° C.

[0022] The thermal element 3 is, for example, a chip thermistor made of a thermistor material and having terminal electrodes formed on both ends. This thermistor can be of NTC type, PTC type, CTR type, etc., but in this embodiment, for example, an NTC type thermistor is used as the thermal element 3. This thermistor is made of a thermistor material such as Mn-Co-Cu material or Mn-Co-Fe material.

[0023] The pattern wiring 4 is formed by patterning using copper foil. One end of the pair of pattern wirings 4 is connected to a corresponding terminal electrode of the heat-sensitive element 3. In addition, a pad portion 4a for connection to a lead frame 6 is provided at the other end of the pattern wiring 4.

[0024] The ultrasonic horn (resonator) 8 has a plurality of protrusions formed on its lower surface, and the contact surface is rectangular in shape corresponding to the shape of the joint portion 4b. The ultrasonic bonding device 1 of this embodiment includes an ultrasonic vibrator (not shown) that is connected to the ultrasonic horn 8 and applies ultrasonic vibrations to the ultrasonic horn 8, and a pressure mechanism (not shown) that presses the ultrasonic horn 8 from above against the work (the temperature sensor body 5 and the lead frame 6) on the anvil 7 to apply pressure.

[0025] The anvil 7 is placed on an XY stage (not shown) and is movable on a horizontal plane. The ultrasonic bonding device 1 also includes a pressing mechanism (not shown) that presses the pressing portion 9 against the insulating film 2 on the anvil 7 with a constant load.

[0026] Next, the ultrasonic bonding method of this embodiment is an ultrasonic bonding method for a temperature sensor in which a pair of pattern wirings 4 of a temperature sensor main body 5 and a pair of lead frames 6 are bonded by the above-mentioned ultrasonic bonding apparatus 1, and includes a placing process of placing the temperature sensor main body 5 on the upper surface of anvil 7, and an ultrasonic bonding process of applying a load to the pair of lead frames 6 placed on the pair of pattern wirings 4 with an ultrasonic horn 8 and applying ultrasonic vibrations to bond them.

[0027] Furthermore, the ultrasonic bonding method of this embodiment includes a film roughening step of roughening the lower surface of the insulating film 2 by blasting beforehand, prior to the placing step. In the above placing step, the pressing portion 9 presses down the outer edge of the insulating film 2 from above at a position avoiding the thermal element 3 and the pattern wiring 4 . In this state, a pressure is applied to the pair of lead frames 6 placed on the pair of pattern wirings 4 by the ultrasonic horn 8 while ultrasonic vibration is applied thereto, thereby bonding the pair of lead frames 6 and the pattern wirings 4 together. As a result, as shown in FIG. 3, the pair of lead frames 6 are connected to the temperature sensor body 5, thereby completing the manufacture of the temperature sensor.

[0028] In this manner, in the ultrasonic bonding apparatus 1 and ultrasonic bonding method of the present embodiment, the upper surface of the anvil 7, at least directly below the ultrasonic horn 8, is flat. Since the fixing surface of the anvil 7 for the insulating film 2 is flat, the insulating film 2 is less likely to be damaged, and a good bonding condition can be obtained.

[0029] In addition, since it is provided with a pressing portion 9 that presses down the insulating film 2 from above at a position that avoids the thermal element 3 and the pattern wiring 4, it is possible to stably fix the insulating film 2 without damaging the thermal element 3 and the pattern wiring 4, and to suppress misalignment during ultrasonic bonding. In particular, since the pressing portion 9 is formed in a U-shape surrounding the thermal element 3 and pressing down the outer edge of the insulating film 2, the outer edge of the insulating film 2 can be more stably fixed around the thermal element 3, making it possible to further suppress misalignment.

[0030] In addition, since the multiple suction ports 10a are arranged to avoid the joint portions 4b between the pair of pattern wirings 4 and the pair of lead frames 6, the insulating film 2 can be sucked and fixed from below by the suction ports 10a without affecting the joint portions 4b. Furthermore, at least one of the multiple suction ports 10a is located directly below the heat-sensitive element 3 of the temperature sensor main body 5 placed on the upper surface of the anvil 7, so that by sucking directly below the heat-sensitive element 3, which cannot be pressed down from above, the portion of the insulating film 2 directly below the heat-sensitive element 3 can also be stably fixed.

[0031] Furthermore, in the ultrasonic bonding method for a temperature sensor of this embodiment, a film roughening process is performed in advance of the placement process, in which the underside of the insulating film 2 is roughened by blasting. This increases the frictional resistance of the underside of the insulating film 2, making it less likely to slip during bonding. EXAMPLES

[0032] Fig. 4(b) shows an image taken from the back side when ultrasonic bonding between the pattern wiring on the insulating film and the lead frame was actually performed using the ultrasonic bonding device for the temperature sensor of this embodiment. For comparison, Fig. 4(a) shows an image when ultrasonic bonding between the pattern wiring on the insulating film and the lead frame was performed using a conventional ultrasonic bonding device. As can be seen from these images, when ultrasonic bonding is performed with conventional ultrasonic bonding devices, the unevenness on the anvil causes multiple holes to be formed in the insulating film during bonding. In contrast, with the ultrasonic bonding device of this embodiment, the anvil has a flat work mounting surface, so no holes are formed in the insulating film during bonding, and the entire bonding area is bonded well.

[0033] The technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the above embodiment, a chip thermistor is used as the heat-sensitive element, but a thin film thermistor or a pyroelectric element may also be used. [Explanation of symbols]

[0034] Reference Signs List 1: ultrasonic bonding device, 2: insulating film, 3: heat-sensitive element, 4: pattern wiring, 4b: bonding portion between pattern wiring and lead frame, 5: temperature sensor body, 6: lead frame, 7: anvil, 8: ultrasonic horn, 9: pressing portion, 10a: suction port

Claims

1. An apparatus for ultrasonically bonding a pair of pattern wirings and a pair of lead frames to a temperature sensor body including an insulating film, a thermal element provided on an upper surface of the insulating film, and a pair of pattern wirings formed on the upper surface of the insulating film and connected to the thermal element, the apparatus comprising: an anvil on which the temperature sensor body is placed with the insulating film facing down; an ultrasonic horn that applies a load to the pair of lead frames placed on the pair of pattern wirings and also applies ultrasonic vibrations to the pair of lead frames to bond them together; The upper surface of the anvil, at least directly below the ultrasonic horn, is a flat surface; a pressing portion that presses the insulating film from above at a position that avoids the thermal element and the pattern wiring; An ultrasonic bonding device for a temperature sensor, characterized in that the pressing portion is formed in a U-shape surrounding the thermal element of the temperature sensor main body placed on the upper surface of the anvil and pressing down the outer edge of the insulating film.

2. An apparatus for ultrasonically bonding a pair of pattern wirings and a pair of lead frames to a temperature sensor body including an insulating film, a heat-sensitive element provided on an upper surface of the insulating film, and a pair of pattern wirings formed on the upper surface of the insulating film and connected to the heat-sensitive element, comprising: an anvil on which the temperature sensor body is placed with the insulating film facing down; an ultrasonic horn that applies a load to the pair of lead frames placed on the pair of pattern wirings and also applies ultrasonic vibrations to the pair of lead frames to bond them together; The upper surface of the anvil, at least directly below the ultrasonic horn, is a flat surface; a plurality of suction ports are formed on the upper surface of the anvil and capable of sucking the insulating film placed on the upper surface of the anvil; 4. An ultrasonic bonding apparatus for a temperature sensor, comprising: a first suction port and a second suction port arranged to avoid bonding portions between the pair of pattern wirings and the pair of lead frames.

3. 3. The ultrasonic bonding apparatus for a temperature sensor according to claim 2, 4. An ultrasonic bonding device for a temperature sensor, comprising: at least one of the plurality of suction ports disposed directly below the heat-sensitive element of the temperature sensor body placed on the upper surface of the anvil.

4. 4. An ultrasonic bonding method for a temperature sensor, which bonds the pair of pattern wirings of the temperature sensor body and the pair of lead frames by using the ultrasonic bonding apparatus for a temperature sensor according to claim 1, comprising: a placing step of placing the temperature sensor main body on an upper surface of the anvil; and an ultrasonic bonding process for bonding the pair of lead frames placed on the pair of pattern wirings by applying a load to the pair of lead frames by the ultrasonic horn and applying ultrasonic vibrations to the pair of lead frames, The upper surface of the anvil directly below the ultrasonic horn is a flat surface; The ultrasonic bonding method for a temperature sensor further comprises a film roughening step of roughening the lower surface of the insulating film by blasting before the placing step.

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