JP4224050B2 - Heater chip thermocouple mounting structure and thermocouple mounting method - Google Patents

Description

In the present invention, when joining electrodes of an electronic component, a soldering material containing solder or an anisotropic conductive film is interposed between the electrodes and heated while sandwiching the electrodes, or both electrodes are directly contacted without inclusions. The present invention relates to a heater chip used for pressurizing and heating, and more particularly, to a thermocouple mounting structure and a mounting method for fixing the vicinity of the tip of the heater chip for temperature control. is there.

Conventionally, a thermocompression bonding method has been widely employed for joining electrodes of electronic components.
First, a typical example will be described with reference to FIG. In FIG. 5, reference numeral 51 denotes a thermocompression bonding device,
52 is a power supply. The thermocompression bonding apparatus 51 includes a work stage 53 that also serves as a pedestal, and a support 54.
The insulating head 56 is driven in the vertical direction along the insulating block 56 and below the bonding head 55.
A heater chip 57 is provided.

On the work stage 53, a substrate 58, which is an object to be bonded, and an electronic component 59, which is the other object to be bonded, are placed, and the lead 59A of the electronic component 59 is positioned on an electrode on the substrate 58 (not shown). Has been. The heater chip 57 has a substantially V shape with the lower end as a tip, and a pair of power supply cables 60 and 61 are connected to the upper part of the fork. The other ends of the power supply cables 60 and 61 are connected to output terminals 62 and 63 of the power source 52.

Further, a thermocouple 64 is fixed in the vicinity of the tip of the heater chip 57, and a pair of wires 65 and 66 connected thereto are insulated by covering and connected to input terminals 67 and 68 of the power source 52. This power source 52 is a pulse heat power source that can be energized while instantaneously controlling the output energy, and has a function of controlling the output current by feeding back the output value of the thermocouple input to the input terminals 67 and 68. It has an output time timer function and a temperature profile setting function.

Thermocompression bonding is performed with such a configuration. First, the bonding head 55 is lowered, the tip of the heater chip 57 is brought into contact with the lead 59A of the electronic component 59 from above, and is pressed with a predetermined pressure. Next, when current flows from the power source 52 to the heater chip 57, resistance heating (joule heat) is generated in the heater chip 57, and the temperature of the entire heater chip 57 rises. At this time, the temperature of the entire heater chip 57 rises, but the temperature directly affects the bonding only at the tip. Therefore, it is ideal that the target of the feedback value is the temperature of the tip portion, so that the thermocouple is usually fixed as close to the tip portion as possible.

The lead 59A of the electronic component 59 to which the pressing force and heat are applied in this way and the electrode of the substrate 58 are caused by the action of a bonding material (for example, solder or anisotropic conductive film) interposed between them.
Join electrically and mechanically. Alternatively, both electrodes are directly brought into contact with no bonding material, and thermocompression bonding is performed by pressurization and heating. In this case, the bonding is performed by a solid phase diffusion bonding action between the electrodes or a brazing action by a plating material on the electrode surface.

Here, in general, when the bonding material has a high melting point or when direct thermocompression bonding is performed without interposing a bonding material, the temperature at the tip of the heater chip 57 needs to be considerably high, and heating to 500 ° C. or higher is required. Not rare. In such a case, electronic components in the vicinity of the electrode to be joined are easily damaged by heat, and for this reason, the heater chip is instantaneously heated by energizing the pulse heat power supply, and heating is immediately stopped. A method of cooling or cooling is effective.

Thus, since the temperature change of the heater chip 57 needs to be abrupt, a sudden temperature change, that is, a temperature shock acts on the mounting portion of the thermocouple 64 fixed in the vicinity of the tip. Therefore, the stress caused by the difference in thermal expansion coefficient repeatedly acts on the joint between the surface of the heater chip 57 and the thermocouple 64, and due to this rapid temperature gradient and the number of repetitions, a joint failure occurs in a short period of time. It has been regarded as a problem to peel off. In addition, this poor bonding is directly linked to the fact that the value fed back is lower than it should be, and this causes the runaway temperature of the heater chip itself, leading to serious damage depending on the workpiece.

In order to avoid such a problem, Patent Document 1 discloses a technique in which unevenness or a through hole is provided in a thermocouple attachment portion of a heater chip and welding is performed directly via arc welding or a joining auxiliary material. Thereby, it is possible to hold the wire connected to the joined body at the tip of the thermocouple, and it is difficult to cause disconnection at the base of the joined body. In addition, direct arc welding is performed without using a joining auxiliary material such as nickel, so that no splinters are generated in the joint portion, which makes it difficult to peel off.

JP 2001-284781 A

However, since the heater chip is generally made of a tungsten alloy or a molybdenum alloy, it is extremely difficult to directly arc weld without using a joining auxiliary material such as nickel. This is because the weldability of both materials is poor, and if the arc welding is performed to the extent that it is reliably welded, the tip ends of a pair of wires that should form a thermocouple assembly are likely to be burned out. This is because the difficulty level itself becomes extremely high.

In addition, the material of the heater chip mentioned above is very poor in workability, and usually the outer shape is cut out from a plate-shaped base material using a wire cutter, but it is also manufactured by adding another process to this and forming a through hole. Cost increases. Furthermore, forming recesses and protrusions requires a special processing method,
Manufacturing costs increase significantly.

The present invention has been conceived by repeating trial and error for such a problem, and has succeeded in dramatically extending the life of the thermocouple mounting state while minimizing an increase in manufacturing cost.

As a first aspect of the present invention, when the tip of the working portion is heated by resistance heat generation by energization and the tip is pressed against the object to be joined and the joined object is joined, the temperature in the vicinity of the tip is measured by a thermocouple. A heater chip thermocouple mounting structure for measuring and feedback controlling the temperature in the vicinity of the tip based on the measured value, and in the shape of the side surface of the main body of the heater chip, there is a slit whose one end communicates with the outer shape in the vicinity of the tip. The slit is formed in a direction substantially perpendicular to the current flow direction for generating heat from the heater chip, and at least the slit width in the vicinity of the other end of the slit is a pair of wires constituting the thermocouple. of being narrower than the sum of the diameter, at least a portion of the conjugate formed heat Dentai tip the pair of wires are fused together, Serial enters a molten state into the slit, to provide a thermocouple mounting structure of the heater chip, characterized in that it is subsequently solidified.

Further, according to a second aspect of the present invention, the pair of wires is inserted from one body side surface near the other end of the slit having one end communicating with the outer shape to the other body side surface. The heater chip thermocouple mounting structure according to the first aspect is provided, wherein the joined body is infiltrated in a molten state from the slit middle portion on the side surface.

In addition, as a third aspect of the present invention, a heater chip body provided with a slit whose one end communicates with the outer shape in the vicinity of the tip that is the working portion is prepared, and a pair of wires for forming a thermocouple made of different metals is provided. Inserting the first joining auxiliary member made of nickel into the slit middle part on the other body side surface from the one body side surface side of the body to the other body side surface side, and the other side surface of the pair of wires A second joining auxiliary member made of nickel is disposed on the distal ends of the pair of wire rods that are bent so as to cover the tip of the first joining auxiliary member. By arc welding from above the joining auxiliary member, the first and second joining auxiliary members and the tip ends of the pair of wires are melted at the same time. It has to entering the middle portion of the serial slits providing a thermocouple mounting method of the heater chip, wherein.

Furthermore, the present invention provides the heater chip main body forming method according to the fourth aspect, wherein the slit is formed by cutting the outer shape of the main body side surface from the plate-shaped base material with a wire cutter simultaneously with the outer shape cutting process. According to a third aspect of the present invention, there is provided a heater chip thermocouple mounting method according to the third aspect.

According to the first aspect of the present invention, the joined body at the tip of the melted thermocouple penetrates into the slit. Therefore, the joined body is joined to a wide area on both surfaces of the opposing slit inner wall, and the rapid temperature change due to the use of the heater chip is repeated. On the other hand, a good bonding state can be maintained for a long time. In addition, when a pair of thermocouple-forming wires passes the thermocouple from one body side surface side to the other body side surface side of the slit, it is substantially perpendicular to the direction of current flow for heating the heater chip. It is inserted side by side. Therefore, it is possible to reduce the influence (noise component) of the potential difference caused by a pulsed or alternating current for causing the heater chip to generate heat.

Moreover, according to the 2nd aspect of this invention, it becomes easy to hold | maintain a pair of thermocouple formation wire material before joining in a fixed position. In addition, since the melted thermocouple assembly that has entered the slit middle part by arc welding is welded to a pair of wires that are inserted into the other end of the slit, the stress due to the movement of the wire after joining is joined to the joined body. The heater tool can be used more safely without directly joining the base of the heater.

Further, according to the third aspect of the present invention, it is possible to prevent the tip of the thermocouple-forming wire rod from being burned out during arc welding by the second joining auxiliary member, and it is possible to realize a thermocouple mounting operation with a stable and high yield. . In addition, a melting force is obtained over a wide area using the inner wall of the slit by melting the first and second joining auxiliary members, and a clear interface is formed between the joining auxiliary member and the thermocouple tip joint by alloying. Since it does not exist, it is possible to perform bonding with higher reliability.

Furthermore, according to the fourth aspect of the present invention, since one end of the slit communicates with the outer shape of the heater chip body, when the heater chip body is cut out from the base material, the slit is simultaneously cut with the wire cutter. Can be processed. Therefore, even when a tungsten alloy or a molybdenum alloy, which has high workability due to poor workability, is used as a raw material, the cost increase can be suppressed to a low level.

Next, a heater chip thermocouple mounting structure and a thermocouple mounting method according to embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a perspective view showing an embodiment of a heater chip thermocouple mounting structure according to the present invention. In this figure, reference numeral 1 is a heater chip, 2 is a heater chip body, and 3 and 4 are a pair of wires forming a thermocouple. Reference numeral 5 denotes a slit, and a portion indicated by a lead-out line 5 is one end of the slit 5 formed in the vertical direction as seen in the figure. That is, one end of the slit communicates with the outer shape of the heater chip.

Further, reference numeral 6 denotes the other end of the slit 5, which is a portion through which the pair of wires 3 and 4 are inserted from the far side toward the near side as viewed in the figure of the heater chip body 2. Reference numeral 7 denotes a thermocouple junction formed at the tip of the pair of wires 3 and 4, and a part of the junction is exposed on the surface of the heater chip body 2 as shown in the figure, but the remaining part. Since it is hidden behind the joint 7, it is in a state of entering the intermediate portion of the slit 5 (not shown).

Next, a side view and a sectional view of the heater chip body 2 shown in FIG. 1 are shown in FIG. FIG. 2A is a side view of the heater chip main body 2, and the lower surface of the heater chip body 2 is an action portion 8 that presses the object to be bonded downward as seen from the figure, and its lower surface is in contact with the object to be bonded. The upper part is a pair of electrodes, and the through holes 9, 1
The heater chip body 2 is energized by a potential difference applied to the pair of power supply electrodes by fixing them to a pair of insulated power supply electrodes through bolts at 0. And by this energization, resistance heat_generation | fever arises and the temperature of the action part 8 rises and a to-be-joined object can be heated with the said press. And the attachment position of the thermocouple for controlling the temperature is provided above the action part 8. FIG.

In the heater chip body 2, a plane parallel to the paper surface as viewed in FIG.
A shape drawn with a solid line is referred to as an outer shape 11. Therefore, in the case of the present embodiment cut out from a plate-like member, the cut shape at the time of cutting is the outer shape 11. That is, in this specification, the main body side surfaces on the front and back sides are not included in the outer shape 11.

Here, a slit 5 is formed above the action portion 8, and one end 12 of the slit 5 communicates with the outer shape 11. Reference numeral 6 denotes the other end of the slit 5. In this example, the vicinity of the other end 6 is formed with a slit width equal to the width of the slit intermediate portion 13. In addition, the above-described through holes 9 and 10 may be through holes in order to have a function for fixing to the power supply electrode with a bolt, but in the case of the present embodiment, strictly speaking, they are not through holes, and other slits 14 and 15. Is communicated with the outer shape 11. The reason will be described later.

FIG. 2B is a cross-sectional view taken along the line XX shown in FIG.
In FIG. 2B, only the hatched portion is a cross section. In this cross-sectional view,
One end 12 of the slit 5 communicating with the outer shape 11, the slit intermediate portion 13, and the other end 6 of the slit are drawn, and all of them are directed from one main body side surface 16 toward the other main body side surface 17 in the thickness direction. It shows that it is formed in the same shape.

Next, a procedure for attaching a thermocouple to the heater chip body 2 will be described with reference to FIG. FIG.
FIG. 3 is an enlarged view showing only the vicinity of an action portion 8 in the cross-sectional view shown in FIG. 3A shows the state before arc welding, and FIG. 3B shows the state after arc welding. First of all, FIG.
In (a), wire rods 3 and 4 made of a pair of dissimilar metals constituting a thermocouple are inserted in the vicinity of the other end 6 of the slit from the side surface 16 of one main body. The pair of wires 3 and 4 are covered with an insulating coating, but the coating is peeled off from the positions 3A and 4A on the tip side.

The ends of the pair of separated wires 3 and 4 are inserted through the vicinity of the other end 6 of the slit 5 and protrude toward the other side face 17 of the main body. A first joining auxiliary member 21 obtained by cutting the nickel ribbon material is temporarily fixed to the slit intermediate portion 13 on the other side surface 17 by resistance welding. Then, the tips of the pair of wires 3 and 4 are bent so as to fall on the first joining auxiliary member 21, and the second joining auxiliary member 22 made of a nickel ribbon material is further formed thereon (on the right side in the drawing). Is placed.

In this state, while argon gas is purged, arc welding is performed by discharging from above the second joining auxiliary member 22 (on the right side in the figure). In the case of this embodiment, TIG welding was performed, but as a result of welding, the tip portions of the pair of wires 3 and 4 and the first and second joining auxiliary members 21 and 22 were melted at a time and integrated to at least a part. Alloy. This is shown in FIG.

In FIG. 3B, the hatched portion of the mesh is a portion melted and spread by TIG welding, that is, a thermocouple joint 23. As shown in this figure, the joined body 23 is melted and liquefied.
Enters the narrow slit middle portion 13 (0.3 mm in the case of the present embodiment) from the other side face 17 side and reaches a pair of wires 3 and 4 in the vicinity of the other end 6 of the slit. In order to make the joined body 23 in a molten state easily spread as shown in the figure, the slit intermediate portion 13 is used.
The fact that the width of the joint must be narrow to some extent is apparent from the fact that the volume of the molten joined body 23 is limited. Moreover, even if an external force is applied to the pair of wires 3 and 4 on the side of one main body side face 16 by the molten joined body 23 reaching the pair of wires 3 and 4 as shown in the figure, the root 24 of the joined body 23 is obtained. Can maintain stable conduction without stress.

When the thermocouple is attached to the heater chip main body 2 in this way, bonding is made on both sides (inner walls) in the slit 5 in a wide range. The bonding interface should have good bonding properties due to the influence of the first and second bonding auxiliary members 21 and 22 made of nickel. First and second joining auxiliary members 2
Since 1, 2 and the pair of wires 3 and 4 are melted at a time, at least a part thereof is alloyed and there is no clear interface between them. All of these work to obtain a strong bond.

From this, the heater chip body 2 can be formed in a large area with the molten bonded body 23 having a limited volume.
It can be seen that it is optimal to join to a narrow slit rather than a wide opening or recess. Further, as can be seen from FIG. 2A, since one end of the slit 5 communicates with the outer shape 11, workability is good when the heater chip body 2 is cut out from the plate-shaped base material, and the manufacturing is performed. Cost can be reduced. This is also why the through holes 9 and 10 communicate with the outer shape 11 through the slits 14 and 15.

Next, the shape of the slit 5 will be further described. FIG. 4 is a side view of the heater chip, in which only the vicinity of the action portion 8 is enlarged. FIG. 4 shows a state before welding in which the pair of wires 3 and 4 are inserted into the slit 5 from the back side of the drawing, but the first joining auxiliary member is not temporarily fixed.

In FIG. 4A, an arrow A indicates the direction of current flow for causing the heater chip to generate heat. Since it is often a pulse heat power supply that is connected to the heater chip, a pulsed current or an inverter high-frequency current flows in this direction with a large current. If a pair of wires 3 and 4 are attached in a line along the direction of the arrow A in such a situation, the wires 3 and 4
Due to the difference in position, a potential difference occurs, which may be mixed as noise in the thermocouple output. Therefore, if the wires 3 and 4 are arranged in a direction substantially perpendicular to the direction of the arrow A, the noise can be reduced.

Therefore, as shown in FIG. 4A, the slit 5 is formed in advance so that the direction of the slit 5 is substantially perpendicular to the direction of the arrow A, and a pair of wires inserted into the slit 5 is directed in the direction of the slit 5. Just line up. In the case of this example, the diameters of the core wires of the pair of wires 3 and 4 are each 0.
Since it is 2 mm, the slit width is set to 0.3 mm. That is, in order to prevent the pair of wires from being arranged along the direction of the arrow A, the slit width may be narrower than the sum of the diameters of the pair of wires. More preferably, the slit width should be narrow within a range in which one of the thicker wires can be easily inserted.

FIG. 4B shows another example. In the case of this example, the diameters of the core wires of the pair of wires 3 and 4 are each 0.5 mm. Therefore, the slit width near the other end 6 of the slit 5 is 0.6 mm.
It is. However, if the joined state is better when the slit width of the slit intermediate portion 13 into which the joined body in the molten state enters is 0.3 mm, the slit 5 is formed as shown in FIG.
In this way, only the vicinity of the other end 6 is formed to have a slit width of 0.6 mm, and the slit width of the one end 12 and the intermediate portion 13 may be set to 0.3 mm.

Since the heater chip of the embodiment described above was manufactured and the lifetime of the thermocouple mounting structure was evaluated, the contents will be described next. For the evaluation, a heater chip body cut out from a 2 mm-thick tungsten alloy plate material and a thermocouple attached with the same structure as in this embodiment was used. Then, this heater chip is mounted on a thermocompression bonding apparatus, and the heating temperature is 520 ° C. and the heating time is 0.7.
Second energization was repeated. Energization was carried out at 10 second intervals, and during that time cooling air was continuously blown onto the heater chip, so the temperature of the heater chip was approximately 150 between the energization and energization.
It dropped to ℃.

In this way, the number of times of heating until an abnormality occurred in the thermocouple attachment state was counted, but no abnormality occurred even after exceeding 1 million times. It can be seen that the durability of the heater chip with the thermocouple attached in the conventional structure is dramatically improved in comparison with the case where an abnormality occurs at about 50,000 times under the same conditions.

The perspective view which shows embodiment of this invention Side view and sectional view showing an embodiment of the present invention Sectional drawing of the principal part which shows embodiment of this invention The principal part side view which shows embodiment of this invention Perspective view showing conventional technology

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heater chip 2 Heater chip main body 3, 4 Wire 5 Slit 6 Other end 7 Joined body 8 Action part 9, 10 Through-hole 11 External shape 12 One end 13 Middle part

Claims (4)

When the tip of the working part is heated by resistance heating due to energization and the tip is pressed against the object to be joined and the joined object is joined, the temperature in the vicinity of the tip is measured by a thermocouple, and based on this measured value. A heater chip thermocouple mounting structure that feedback-controls the temperature in the vicinity of the tip, and has a slit whose one end communicates with the outer shape in the vicinity of the tip in the side surface shape of the main body of the heater chip. The slit width at least in the vicinity of the other end of the slit is narrower than the sum of the diameters of the pair of wires constituting the thermocouple. is formed, at least a portion of the conjugate formed heat Dentai tip the pair of wires is melted to each other, in a molten state into the slit Input, and thermocouple mounting structure of the heater chip, characterized in that it is subsequently solidified. The pair of wire rods are inserted from one side surface side of the slit near one end to the other side surface side of the slit whose one end communicates with the outer shape, and the bonding is performed from the slit middle portion on the other main body side surface. 2. The thermocouple mounting structure for a heater chip according to claim 1, wherein the body is infiltrated in a molten state. Prepare a heater chip body provided with a slit with one end communicating with the outer shape in the vicinity of the tip, which is the action part, and connect a pair of wires for forming a thermocouple made of a dissimilar metal from the side surface of one body to the other. The first joining auxiliary member made of nickel is disposed in the slit middle portion on the other side surface of the main body, and the front end portion protruding on the other side surface of the pair of wire rods is inserted into the first side surface side. A second joining auxiliary member made of nickel is disposed on the tip end portions of the pair of wire rods folded so as to cover the joining auxiliary member, and arc welding is performed from above the second joining auxiliary member. Thus, the first and second joining auxiliary members and the tip portions of the pair of wires are melted at the same time, and the melted liquid that is liquefied by this melting and at least partially alloyed enters the intermediate portion of the slit. Thermocouple method of mounting a heater chip, wherein was Unishi. In the method of forming the heater chip body, the slit is formed by a wire cutter simultaneously with an outer shape cutting process when an outer shape that is a side surface shape of the main body is cut out from a plate-shaped base material by a wire cutter. 4. A thermocouple mounting method of the heater chip according to 3.

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