JP2003033888A - Pulsed laser welding method of protective tube for temperature sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pulsed laser welding method enabling proper welding without such poor welding on a welded area as hole-making or inner-diameter- narrowing. SOLUTION: In the welding method, a protective tube 6 comprises a thin- walled small diameter pipe 6A and a thin-walled large diameter pipe 6B monolithically-containing a boss section 30. An open end of the small diameter pipe 6A is fitted in the boss section 30 by insertion, and a pulsed laser beam is radiated on a welding area A to provide laser welding between the small diameter pipe 6A and the boss section 30. For the welding, the welding area of the boss section 30 is melted by heating from pulsed laser beam radiation. After each welding completion by 1 shot, the welding area is always cooled for a definite period of time to be solidified as well as the protective tube 6 is rotated to the required angle so as to circumferentially lap a part of next welding area over the former welding area. By repeatedly providing such a pulsed laser welding, the boss section 30 is circumferentially-welded with the small diameter pipe 6A.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser pulse welding method for a protection tube for a temperature sensor that houses a chip-shaped temperature detection element.

[0002]

2. Description of the Related Art In semiconductor devices, extremely fine temperature control has been demanded along with miniaturization of patterns and enlargement of wafers. A temperature sensor generally used at present is a Pt resistance temperature sensor having a resistance value of about 100Ω. Therefore, in order to measure the temperature with high accuracy, it is necessary to flow a measurement current of 1 to 2 mA to the Pt line due to the limit of circuit technology (limit of high-speed sampling, AD resolution, miniaturization, etc.). In that case, since the temperature sensor has a small size in order to improve high-speed response, a temperature rise larger than the control temperature range occurs. That is, the temperature control range of semiconductors and the like is ± 0.01 ° C, but depending on the shape, the temperature rise of the Pt resistance temperature sensor (heat generation by the measurement current) is as high as 0.1 ° C, which is more than 10 times the control temperature range. In some cases, In such a case, if the flow of the gas to be controlled is constant, the temperature rises at a constant level, so there is no problem in controllability, but the flow of gas is constantly fluctuating from a microscopic perspective. Therefore, the temperature rise of the Pt resistance temperature sensor is constantly changing (since the heat dissipation changes depending on the flow rate), the true target temperature cannot be measured. For example, if the gas flow changes by 10% without changing any other conditions, the detected temperature changes by 10% (about 0.01 ° C) of the temperature rise of 0.1 ° C, and the temperature is changed to true. It will be controlled as temperature. Therefore, there is a demand for a temperature sensor that cannot perform highly accurate control, has a large resistance value in a semiconductor manufacturing apparatus, has a small temperature rise, and can measure temperature with higher accuracy.

The higher the resistance of the temperature sensor, the smaller the measuring current required to detect the same temperature. The temperature rise due to the measured current of the temperature sensor is small because it is proportional to the square of the current. That is, when the resistance value becomes 1 kΩ, the measured current becomes 1/10 of that of Pt100Ω, that is, 0.1 to 0.2 mA, and the temperature rise becomes 1/10. Become. In this case, even if the flow fluctuates, the fluctuation is within the control temperature, and high-precision control is possible.

The current Pt resistance temperature sensor is a very thin Pt.
Since a wire is wound around a glass tube to manufacture a Pt resistance temperature sensor element, it is not possible to manufacture a small element having a high resistance value. For example, to make a resistance value of 1 kΩ, 1
Since the Pt wire having a length of 0 times is wound, the element itself becomes large.

[0005]

As described above, the conventional Pt resistance temperature sensor is of the winding type and has a low resistance value, so that it has the following problems.

Since the resistance value of the Pt wire is as low as about 100Ω, it is necessary to supply a large measuring current when measuring a minute temperature change. However, in this case, the thermal effect of self-heating is inevitably large, so that highly accurate measurement cannot be performed.

For example, when a resistor having a resistance value of 100Ω is used, the resistance value is about 0.4Ω when the temperature changes by 1 ° C.
If the current changes and the current at that time is 1 mA, the signal voltage becomes 0.4 mV. Therefore, the power consumption at this time is 10 ⁻⁴ W (W = RI ² = 100 × 10 ⁻³ × 10 ⁻³ ),
If it is a protective tube with a diameter of 1.5 to 2 mm, it will be about 0.1
The temperature rises by 0.2 m ° C. Therefore, if such a temperature sensor is used in a semiconductor manufacturing apparatus to perform temperature control at 10 m ° C., the amount of heat generated by the sensor itself (power consumption) is large and the control is disturbed. Therefore, when a pattern having a pattern width of about 0.1 μm is formed on the large-diameter wafer by photoetching, the temperature of the temperature sensor may be deviated by the heat generated by the sensor itself or the temperature control may be hindered. Can not be.

Since the insulating tube is used to insulate the Pt wire from the protective tube that houses the Pt wire, the outer diameter of the protective tube is further increased and the sensitivity (response) to temperature change is low.

[0009] Therefore, the present inventors have
As a result of making various sensors and conducting experiments, the use of a metal foil resistor such as Ni in place of the Pt wire makes it possible to miniaturize the resistance pattern by the semiconductor lithography technique. It was possible to reduce the power consumption with a high resistance and completely solve the above problems.

If a metal foil resistor is provided on a substrate and the substrate is inserted into a protective tube, a glass tube and an insulating tube are not required. Therefore, the protective tube has a wall thickness of about 0.05 mm and a diameter of 1.4 mm or less. A temperature sensor having a small diameter and a fast response to temperature changes was obtained, and the above problems could be solved. In this case, the protective tube has a small diameter (about 1 mm) on the tip side that houses the temperature detecting element,
The base end side into which the lead wire is inserted becomes a large-diameter thin-walled different-diameter tube.

As a method for producing a thin-walled different-diameter pipe, (1) a method for producing a different-diameter pipe by drawing (2) two kinds of pipes having different outer diameters and equal wall thicknesses are made by drawing, and these pipes are manufactured. Two methods are conceivable: a method of joining by brazing or continuous laser welding to form a protective tube having a different diameter.

However, the method (1) of producing protective tubes of different diameters at once by drawing is not applicable because the wall thickness becomes non-uniform and the response to temperature change varies. For example, with a diameter of about 1.4 mm,
It is very difficult to manufacture thin and long thin tubes by drawing.

According to the manufacturing method (2), it is possible to obtain a different diameter protective tube having a uniform wall thickness. However, when a small-diameter pipe and a large-diameter pipe are joined by brazing, the thin protective tube does not melt because the joining temperature is low, but when used for temperature measurement of semiconductor manufacturing equipment using high-purity water. However, it cannot be used because impurities contained in the brazing material start to melt and adversely affect semiconductor manufacturing.

In the case of continuous laser welding, if the laser beam is continuously irradiated and welded, the heating temperature becomes too high and welding defects such as holes are formed, which is not preferable. That is, in continuous laser welding, it is necessary that the joined portion of the two superposed members be melted and fused together. When laser light is continuously applied to the welded part of the protection tube, the temperature of the protection tube is low at the beginning of welding, so a certain amount of energy is required, but since the temperature of the protection tube rises gradually, the initial laser energy is large. Too much, the welded part melts too much and holes are made. In particular, when the protective tube is a thin tube and has a small wall thickness, heat is not sufficiently dissipated and heat is easily accumulated, and the temperature rises rapidly and melts. Further, when the welded portion is heated and melted, it hangs down and solidifies, so that the inner diameter of the welded portion is significantly smaller than the inner diameter before welding, and there is a possibility that a component to be inserted into the inside cannot be inserted. In addition, the way it melts and hardens during welding is different,
The protection tube was sometimes bent.

Therefore, the pulse laser welding method is adopted,
When a welding spot is irradiated with a pulsed laser beam to be heated and melted, and when one shot of welding is completed, the welding spot is sufficiently cooled and solidified, and then the next welding spot is irradiated with laser.
Since the welding conditions for each shot were substantially constant, the protective tube was not melted too much and holes were not punctured, and good welding was possible. In order to reduce the diameter of the welded part, insert the pin in advance inside the protective tube, and if pulse laser welding is performed in this state, the pin will prevent the melted portion from hanging down. The bending of the protective tube could be prevented well.

The present invention has been made on the basis of the above-mentioned conventional problems, examination results and experimental results. The purpose of the present invention is to prevent welding defects such as holes at the welding spots and small inner diameters. First, it is another object of the present invention to provide a pulse laser welding method for a protection tube for a temperature sensor, which enables good welding.

[0017]

In order to achieve the above object, a first invention is a pulse laser welding method for a protection tube for a temperature sensor containing a temperature detection element, wherein the protection tube is a thin-walled small-diameter pipe. And a large-diameter thin-walled pipe having the boss portion integrally fitted with the small-diameter pipe and pulse laser welded at one end, and the welded portion of the boss portion is heated and melted by irradiation of pulse laser light, and each shot is shot. When the welding is completed, the welding spot is cooled and solidified for a certain period of time, and the pulse tube is welded by rotating the protection tube by a required angle so that a part of the next welding spot overlaps the welding spot in the circumferential direction. By repeating the process, the boss portion is welded to the small diameter pipe over the entire circumference. In the first invention, when the pulse laser welding is completed,
The weld is sufficiently cooled and solidified. Then, the next pulse laser welding is performed. That is, the welded portion is cooled and solidified for each shot. Therefore, the temperature rise can be suppressed, and even a thin protection tube will not melt too much to form a hole.

The second invention is the same as the first invention,
A pin made of a material having good thermal conductivity and having an outer diameter substantially equal to the inner diameter of the small-diameter pipe is inserted into the small-diameter pipe and positioned at the welded portion of the small-diameter pipe and the large-diameter pipe, and in this state pulse laser welding Is to do. In the second invention, the pin radiates the heat of the welded portion and suppresses the temperature rise. Further, it prevents the welded portion from melting and bulging toward the inside of the protective tube, and prevents the protective tube from bending.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail based on the embodiments shown in the drawings. 1 is a sectional view showing an embodiment of a temperature sensor provided with a protective tube welded by a pulse laser welding method according to the present invention, FIG. 2 is a sectional view of the protective tube, and FIG. 3 is a plan view of a temperature detecting element. FIG. 4 is a micrograph of the welded portion of the protective tube, FIG. 5 is a plan view for facilitating understanding of the welded portion, FIG. 6 is a micrograph of the welded portion in cross section, and FIG. 7 is an understanding of the welded portion. FIG. 6 is a cross-sectional view for facilitating the operation. First, an outline of the configuration of the temperature sensor 1 will be described. The temperature sensor 1 is composed of an element unit 2 and a metal pipe 3 for accommodating the element unit 2, and constitutes a 4-wire type temperature sensor. There is.

The element unit 2 includes a temperature detecting element 4 attached to the tip of a flexible printed circuit board 5,
The temperature detecting element 4 is connected to the flexible printed board 5
The flexible printed circuit board 5 is electrically connected to the external lead wire 7 via a hermetic component 8.

The temperature detecting element 4 comprises a ceramic substrate 10 made of alumina or the like and a Ni foil resistor 11 bonded to the surface of the ceramic substrate 10 with an adhesive. The width of the ceramic substrate 10 is 0.7 to 1 mm,
It is formed in a thin and long sheet shape having a length of 8 to 10 mm and a thickness of about 0.4 mm.

The Ni foil resistor 11 is formed such that the resistance pattern meanders in the longitudinal direction of the ceramic substrate 10 as shown in FIG. The pattern 11A and the return path pattern 11B are formed so as to be shifted by a half pitch so as to mesh with each other in a non-contact state, and each end has two pad portions 13 (13a to 13d), two in total. The Ni foil resistor 11 has a thickness of about 3 μm,
The width is about 10 μm, the resistance value is about 1,000 Ω, and the entire surface is covered with an insulating film. Reference numeral 14 is a resistance pattern for trimming, and several types of resistance patterns having different resistance values such as 1Ω, 2Ω, and 3Ω are formed. The resistance pattern 14 is entirely electrically connected to the Ni foil resistor 11 when the Ni foil resistor 11 is formed into a predetermined pattern by etching, and is appropriately disconnected when the resistance value is adjusted. That is, the resistance value of the Ni foil resistor 11 is, for example, 9
When the resistance value is 95Ω, the resistance value is smaller than the desired resistance value of 1,000Ω by 5Ω, so that one resistance pattern of 1Ω and two resistance patterns of 2Ω are separated to form the Ni foil resistor 11 of 1,000Ω. The actual trimming is adjusted with finer values.

The flexible printed circuit board 5 is formed of polyimide or the like into an elongated strip shape.
It has the same width as the ceramic substrate 10 and has a width of 4
The circuit patterns 16 of the book are formed in parallel, one end side thereof is connected to each of the external lead wires 7 through the hermetic component 8, and each pad portion 13 of the Ni resistor 11 is bump-bonded to the other end side thereof. There is. Of the four circuit patterns 16, for example, two on both sides are the Ni foil resistor 11
Is used as a current line that supplies current to the
It is used as a signal detection line for detecting the voltage when the i-foil resistor 11 is energized. Such a flexible printed circuit board 5 is provided with a protective tube 6 together with the hermetic component 8.
The temperature detecting element 4 is pressed against the inner wall surface of the tip of the protective tube 6.

The external lead wires 7 are composed of four wires (only two wires are shown in FIG. 1), two of which are for current wires and the other two are for signal detection wires, and one end of which is the hermetic component 8. The terminals (lead wires) 20 are respectively connected by solder 21, and the other ends are similarly connected by solder to the circuit pattern 16, respectively. Reference numeral 22 is a stainless braided wire that protects the external lead wire 7.

The hermetic component 8 has four terminals 20, a cylindrical metal ring 23 made of Kovar or the like with both ends open, and the terminal 20 sealed in the metal ring 23. The glass 24 for sealing is used to hermetically seal the opening of the protective tube 6. Each terminal 20
Solder connection portions of the lead wire 7 and the circuit pattern 16 are sealed with synthetic resin 25. A synthetic resin 26 is potted on each terminal 20.

The protection tube 6 is made of SUS304, SUS3.
It is made by welding two different diameter pipes consisting of 16 or the like, that is, a small diameter pipe 6A and a large diameter pipe 6B with their axes aligned with each other and welding, and an inert gas such as argon, nitrogen, dry air or the like. The oil is sealed.

The tip end side of the small diameter pipe 6A is closed,
It consists of a straight pipe with the base end open, with an outer diameter of 1.0 to 1.4 mm, a wall thickness of 0.05 mm, and a length of 20.
The temperature detecting element 4 and the flexible printed circuit board 5 are incorporated inside the device with a length of about 30 mm. Such a small diameter pipe 6A can be easily manufactured by drawing a pipe material.

The large-diameter pipe 6B is a pipe whose both ends are open, and is inserted into the metal pipe 3 and has an outer diameter of 3.0 mm and a length of 7 to 8 mm. A tubular boss portion 30 forming a connection portion with the small diameter pipe 6A is integrally provided so as to project. The boss portion 30 has an outer diameter of 1.2 to 1.8 mm and a wall thickness of about 0.1 to 0.2 mm, and has the same wall thickness as the large diameter pipe 6B. Such a large-diameter pipe 6B can be easily manufactured by drawing a pipe material, like the small-diameter pipe 6A.

The metal pipe 3 is made of SUS316 or the like and is open at both ends, and has an outer diameter of 4.0 mm, an inner diameter of 3.0 mm, and a length of 30 to 50 mm.
The large-diameter pipe 6B and the stainless braided wire 22 of the external lead wire 7 are fitted and inserted in the openings at both ends, and a synthetic resin (thermosetting resin) 31 is filled inside.

Next, a method of welding the protective pipe 6 according to the present invention will be described. The base end portion of the small diameter pipe 6A is fitted into the boss portion 30 of the large diameter pipe 6B from the front, and pulse laser welded by a laser welding machine. In FIG. 5, 41
Is a welded spot for each shot (particularly, it is referred to as a nugget portion when indicating a melted and solidified mark). The welded portion A of the protective tube 6 is the tip portion of the boss portion 30 and the outer peripheral portion of the small diameter pipe 6A corresponding to this tip portion. In welding, the laser light source irradiates the tip portion of the boss portion 30 with the pulsed laser light PL to heat and melt the welded portion 41 and the small diameter pipe 6A for welding. At the time of laser light irradiation, an inert gas such as argon is blown to prevent oxidation (immediately before, during, and immediately after welding).

When the outer diameter of the small diameter pipe 6A is 1.0 mm and the outer diameter of the boss portion 30 is 1.4 mm, the pulse laser beam PL has a pulse width of 6 ms, an energy of 1.8 J, and a spot diameter of 0.3 to 0. It is about 5 mm. When the outer diameter of the small diameter pipe 6A is 1.0 mm and the outer diameter of the boss portion 30 is 1.25 mm, the pulse width is 6 ms, the energy is 1.0 J, and the spot diameter is about 0.3 to 0.5 mm. When the welding for one shot is completed, the welding spot 41 is kept for a certain time (T = 2 to 3).
(S) When cooled and completely solidified, the protection tube 6 is rotated about 10 to 20 degrees around the axis and the pulsed laser light PL is irradiated to the next welding portion. By repeating such pulse laser welding, the tip of the boss portion 30 is welded to the small diameter pipe 6A over the entire circumference.

The confirmation that the welding spot 41 has cooled and solidified is controlled by the intermittent time (T) of the pulse laser beam PL.
The cooling of the welding point 41 may be either natural cooling or forced cooling. The wrap ratio of the adjacent nugget portions 41 varies depending on the rotation angle of the protection tube 6, but is 30 to 70.
%, And preferably about 50%.

By pulse laser welding the bosses 30 of the small diameter pipe 6A and the large diameter pipe 6B under the above welding conditions,
It is possible to satisfactorily weld the small diameter pipe 6A having a small wall thickness without forming a hole. However, since the welded portion of the small diameter pipe 6A is also heated and melted to the inner peripheral surface, the nugget portion 41 bulges toward the inside of the small diameter pipe 6A and solidifies. Therefore, the inner diameter of the small diameter pipe 6A becomes small at the welded portion A as shown in FIG. For example, a small diameter pipe 5A having an outer diameter of 1.0 mm and an inner diameter of 0.9 mm
In the case of pulse laser welding, the inner diameter was reduced to 0.76 mm. However, even if the inner diameter is reduced, the inner diameter of the small diameter portion is inserted into the small diameter pipe 6A.
If it is larger than the width of the flexible printed circuit board 5, there is no problem and it can be used as the protective tube 6 of the temperature sensor 1.

FIG. 8 is a diagram showing another pulse laser welding method of the present invention. FIG. 9 is a photomicrograph of a welded portion subjected to pulse laser welding, and FIG. 10 is a sectional view for facilitating understanding of the welded portion. In this pulse laser welding method, a pin 50 having an outer diameter substantially equal to the inner diameter of the small-diameter pipe 6A is inserted into the small-diameter pipe 6A and positioned at the weld A of the small-diameter pipe 6A and the boss portion 30. The tip of the boss portion 30 and the small-diameter pipe 6A are heated and melted by welding with the laser beam PL to weld them.

The irradiation condition of the pulsed laser beam PL, the interruption time T, and the rotation angle of the protective tube 6 are exactly the same as those of the above pulsed laser welding method. That is, when the welding for one shot is completed and the welded portion is cooled and completely solidified for a certain period of time, the protection tube 6 is rotated about 10 to 20 degrees around the axis line and the pulse laser beam PL is applied to the next welded portion 41. Irradiate. By repeating such pulse laser welding, the tip of the boss portion 30 is welded to the small diameter pipe 6A over the entire circumference. When welding is completed, the pin 50 is pulled out from the small diameter pipe 6A. Pin 50
Is formed to be hollow or solid by a material having a large thermal conductivity such as copper or a copper alloy in order to dissipate the heat of the welded portion A.

As is apparent from FIG. 10, when the pulse laser welding is performed using the pin 50, the pin 5 prevents the heat-melted metal from swelling and solidifying inside the small diameter pipe 6A.
Since 0 is blocked, the welded portion of the small diameter pipe 6A is not reduced in diameter, and good welding can be performed. Also,
The pin 50 has a function of preventing the bulging of the nugget portion 41,
It also has a function as a heat sink that dissipates the heat of the welded portion A, and can reduce the cooling and solidifying time of the nugget portion 41. Furthermore, it is possible to prevent the small-diameter pipe 6A from bending due to the difference in how the welded portion 41 melts or solidifies.

[0037]

As described above, the pulse laser welding method for the temperature sensor protective tube according to the present invention has a wall thickness of 0.0.
Even an extremely thin tube of about 5 mm will not melt too much and will not have holes, and good welding can be achieved. Therefore, it is possible to provide a temperature sensor suitable for use in temperature measurement of a semiconductor manufacturing apparatus or the like which requires particularly accurate temperature control. Further, when performing the pulse laser welding by inserting the pin into the small diameter pipe, it is possible to prevent the molten metal from hanging down and swelling in the pipe, and solidifying, so that the inner diameter of the welded portion does not decrease, A good welding quality can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a temperature sensor having a protection tube welded by a pulse laser welding method according to the present invention.

FIG. 2 is a sectional view of a protection tube.

FIG. 3 is a plan view of a temperature detecting element.

FIG. 4 is a micrograph of a welded portion of a protective tube.

FIG. 5 is a plan view for facilitating understanding of the welded portion.

FIG. 6 is a micrograph showing a cross section of the welded portion.

FIG. 7 is a sectional view for facilitating understanding of the welded portion.

FIG. 8 is a sectional view showing another pulse laser welding method of the present invention.

FIG. 9 is a micrograph showing a cross section of a welded portion.

FIG. 10 is a sectional view for facilitating understanding of the welded portion.

[Explanation of Codes] 1 ... Ni foil resistor temperature sensor, 2 ... Element unit, 3 ...
Metal pipe, 4 ... Temperature detecting element, 5 ... Flexible printed circuit board, 6 ... Protective tube, 6A ... Small diameter pipe, 6B ... Large diameter pipe, 7 ... External lead wire, 10 ... Ceramic substrate,
11 ... Ni foil resistor, 30 ... Boss part, 41 ... Welding part,
50 ... Pin, A ... Welded part.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Matsuo Zama             238, Itaizawa, Nakatashiro, Ouchi Town, Yuri District, Akita Prefecture             1 Alpha Electronics Stock             In the company (72) Inventor Toru Okamoto             238, Itaizawa, Nakatashiro, Ouchi Town, Yuri District, Akita Prefecture             1 Alpha Electronics Stock             In the company F-term (reference) 4E068 BG02 CA03 CA14 CB06 CE04                       DA00

Claims (2)

[Claims] 1. A method for pulse laser welding a temperature sensor protective tube containing a temperature detecting element, wherein the protective tube integrally comprises a thin small-diameter pipe and a boss portion into which the small-diameter pipe is fitted. It is composed of a thin large-diameter pipe, the welding portion of the boss portion is heated and melted by irradiation of a pulsed laser beam, and when welding is completed for each shot, the welding portion is cooled and solidified for a certain period of time. The boss portion is welded to the small diameter pipe over the entire circumference by rotating the protective tube by a required angle so that a part of the welded portion overlaps the welded portion in the circumferential direction and repeating the pulse laser welding. Pulse laser welding method for protective tube for temperature sensor. 2. The pulse laser welding method for a protection tube for a temperature sensor according to claim 1, wherein a pin made of a material having good thermal conductivity and having an outer diameter substantially equal to the inner diameter of the small diameter pipe is inserted into the small diameter pipe. A pulse laser welding method for a protective tube for a temperature sensor, characterized in that the laser is positioned at a welded portion of the small diameter pipe and the large diameter pipe, and pulse laser welding is performed in this state.