JP3590231B2 - Contact heating heater - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a heater configured to contact and heat an object to be heated, such as a bonding heater head used for directly bonding a semiconductor bare chip onto a substrate.
[0002]
[Prior art]
As a method of directly bonding a semiconductor bare chip onto a substrate, an ACF connection method using a resin-based adhesive such as an anisotropic conductive film (ACF), or Au-Si, Au-Sn, or the like used for a multi-chip module is used. A flip chip connection method using a low melting point brazing such as Pb-Sn has been performed.
[0003]
For example, in the flip-chip connection method, as shown in FIG. 6, a semiconductor chip 21 is placed on a substrate 20 of a multilayer package, and the semiconductor chip 21 is pressed while being heated by the head 11 of the bonding heater 10 from the upper surface. Is going. At this time, bonding and wiring can be performed by the solder bumps 22 provided on both.
[0004]
As such a bonding heater 10, a heater using an aluminum nitride ceramic having high thermal conductivity has been used. In this method, the bonding heater 10 shown in FIG. 6 is formed in a rectangular body made of aluminum nitride ceramics, and the front end of the bonding heater 10 is used as the head 11 to be in contact with the semiconductor chip 21, and the rear end of the holder 13 is connected to another member. A heating element (not shown) such as Ag-Pd or Pt-Pd is printed or baked on the side surface or inside by a thick-film printing technique, and then covered with a cover glass paste or the like (thick-film ceramic head). ). As a characteristic required of such a bonding heater 10, first, it is necessary to efficiently transmit heat for softening or melting the adhesive to be used to the adhesive via the semiconductor chip 21.
[0005]
From the viewpoint of production efficiency, it is also important that the time required to raise the temperature to the required temperature is short and that the time required for the adhesive to solidify after bonding is short. Further, when joining the semiconductor chips 21, pressure is applied simultaneously with heat, so that the head 11 of the bonding heater 10 is required to have mechanical strength, wear resistance, or toughness. However, in the case of the above-mentioned thick film type ceramic head, since aluminum nitride ceramics having good thermal conductivity is used, heat of the heating element easily escapes to the holder 13 side, and the heating efficiency of the head 11 side is poor. there were. Furthermore, because of the thick film type, the adhesion between the heating element and the ceramics is poor, and there is a difference in thermal expansion, so that the heating element peels off from the ceramics during repeated thermal cycles of heating and cooling, and frequently breaks. And the like. Further, there is also a problem that the aluminum nitride ceramics constituting the head 11 is easily chipped due to low toughness.
[0006]
Therefore, in recent years, as shown in FIG. 7, the head 1 is formed by forming the holder 3 from a low heat conductive ceramic and joining a heat transfer portion 1a made of a high heat conductive ceramic to a heat generating portion 2 having a heat generating element 2a provided therein. A bonding heater 10 was developed in which the head 1 was fixed to the holder 3 so that the recess 3b was formed. When the bonding heater 10 is used, in a state where the heating element 2a is energized and heated, the head 1 is pressed against the semiconductor chip while the heat transfer section 1a is being heated, and is joined to the substrate by solder bumps. In this heater 10, the heat generating portion 2 and the holder 3 are made of ceramic, and are intended to improve the heating efficiency.
[0007]
[Problems to be solved by the invention]
By the way, the above-mentioned prior art was very effective, but there were difficulties in production efficiency, and there were the following problems when trying to further shorten the heating time to the required temperature. Was.
[0008]
That is, although it is devised that heat is not easily dissipated by heat transfer, it takes a long time to start up because the contact area between the head and the holder is large. Therefore, when a large amount of heat is applied to the head in an attempt to forcibly speed up the operation, a large amount of heat is transmitted to the holder and transmitted to the apparatus main body via the holder. Therefore, the main body of the device is deformed due to thermal expansion, and the parallelism of the head with respect to the chip is deviated, which may affect the final product.
[0009]
[Means for Solving the Problems]
Therefore, the present invention provides a ceramic head for transmitting the heat of the heating element to and from the holder so that the upper surface of the head comes into contact with the holder when pressing and heating the object to be heated. And a contact heating heater having a head mounted on a holder.
[0010]
[Action]
According to the present invention as described above, the head made of ceramics can be moved in and out of the holder, so that when the head is heated, the head is put out so that the top surface of the head is not in contact with the holder. As a result, the head comes into contact with the holder only in a narrow area of the edge of the side surface and the lower surface, and thus the heat radiation to the holder is minimized, so that the heating time is greatly reduced.
[0011]
Also, while the semiconductor chip is pressed and heated by contact, the upper surface of the head comes into contact with the holder, and the holder firmly holds the head from above, so that the parallelism of the head can be accurately maintained, and furthermore, the cooling in the pressed state In this case, since the upper surface of the head is in contact with the holder, that is, in contact with a wide area, the heat of the head is transmitted to the holder in an appropriate amount, and the time required for cooling is short due to its action. Since the amount of heat during cooling is relatively smaller than that during heating, even if the upper surface of the head is in contact with the holder, the amount of heat transmitted to the holder is not so great as to adversely affect the apparatus.
[0012]
As described above, it is possible to prevent a large amount of heat from the heater from being transmitted to the apparatus main body, thereby improving the heating efficiency, thereby greatly improving the production efficiency.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings by taking a bonding heater as an example.
[0014]
FIG. 1 shows an end view of a bonding heater (hereinafter abbreviated as a heater) 10 of the present invention. In the heater 10, a concave portion 3b is formed in a holder 3 made of low thermal conductive ceramics, and a heating element 2a is embedded. A head 1 in which a heat transfer portion 1a made of a high thermal conductive ceramic is joined to a heat generating portion 2 made of ceramic and fitted and held in a concave portion 3b of the holder 3. The head 1 is movable in and out of the holder 3 (in FIG. 1, it can be said that the head 1 can be moved up and down), and the head upper surface 2b and the upper surface 2b on the holder 3 side move with the movement of the head 1. A gap s is generated between the contact surface 3c and the contact surface 3c.
[0015]
By the way, to explain how to use the heater 10, when the head upper surface 2b and the contact surface 3c of the holder 3 are sufficiently separated as shown in FIG. Then, as shown in FIG. 2, the contact surface 1 a at the tip of the head 1 is pressed against the semiconductor chip 21, heated by contact, and joined to the substrate 20 by the solder bump 22. At this time, the head 1 moves backward until the upper surface 2b of the head 1 and the contact surface 3c of the holder 3 of the apparatus main body come into contact with each other, and the holder 3 firmly presses the head 1 from above. You will not lose. In this state, the power generation and heat generation are stopped, the head 1 is cooled, and then the heater 10 is returned to the position shown in FIG. 1 to complete one cycle of the operation.
[0016]
In other words, according to the heater 10, the head 1 contacts the holder 3 only at an extremely narrow area of the sliding surface 4 (side surface) and the edge of the lower surface when power is supplied (at the start of energization and heat generation). Is made of low thermal conductive ceramics, so that heat is not easily transmitted to the holder 3. In addition, since the head 1 is made of high thermal conductive ceramics, the temperature can be rapidly raised, and the heat from the heat generating portion 2a can be satisfactorily transmitted from the tip of the head 1 to the contact object. Since the head 1 and the holder 3 are made of ceramics, they have excellent wear resistance and can be used for a long time without being worn or deformed. Furthermore, while the semiconductor chip is pressed, the upper surface 2b of the head 1 comes into contact with the holder 3, and the holder 3 firmly holds down the head 1 from above, so that the parallelism of the head 1 can be accurately maintained. When cooling in the pressed state, the head upper surface 2b is in contact with the holder 3, that is, in contact with a wide area, so that an appropriate amount of heat of the head 1 is transmitted to the holder 3, and the time required for cooling is reduced by the action. short. Since the amount of heat during cooling is relatively smaller than that during heating, even if the head upper surface 2b is in contact with the holder 3, the amount of heat transmitted to the holder 3 is not large enough to adversely affect the apparatus.
[0017]
FIG. 3 shows another embodiment of the present invention. As shown in FIG. 3, the heater 10 has a bearing 5 interposed between the sliding surface 4 of the head 1 and the holder 3, so that an undesired misalignment occurs. It has the effect of preventing and insulating.
[0018]
In addition, by forming an uneven surface on the sliding surface 4 of the head 1, a heat insulating effect can be obtained. In addition, by applying a sliding powder such as boron nitride to the sliding portion, the sliding property can be improved. it can.
[0019]
Examples of the high heat conductive ceramic include ceramics such as high heat conductive silicon nitride, aluminum nitride, and silicon carbide. The high thermal conductive silicon nitride-based ceramic has silicon nitride (Si ₃ N ₄ ) as a main component, a 3a group element (RE) in the periodic table in an oxide (RE ₂ O ₃ ) conversion of 3 to 5 mol%, and aluminum. It has a composition of not more than 0.2% by weight in terms of oxide, and has an average particle size of silicon nitride crystal as large as 5 μm or more, and a crystal phase containing a Group 3a element of the periodic table, silicon, and oxygen at a grain boundary. For example, there is one having a thermal conductivity of 50 W / m · K or more by being formed.
[0020]
The aluminum nitride-based ceramic has aluminum nitride (AlN) as a main component and a rare earth element oxide or the like as a sintering aid. Further, the silicon carbide ceramic contains silicon carbide (SiC) as a main component and contains sintering aids such as B, C or Al ₂ O ₃ or Y ₂ O ₃ .
On the other hand, as the low thermal conductive ceramic, low thermal conductive silicon nitride, alumina, zirconia and the like can be used, and various other ceramics can be used.
[0021]
The low thermal conductive silicon nitride ceramics have silicon nitride (Si ₃ N ₄ ) as a main component and Al ₂ O ₃ , Y ₂ O _{3 and the} like as a sintering aid. Alumina ceramics have Al ₂ O ₃ as a main component and SiO ₂ , MgO, CaO, etc. as a sintering aid. Further, some zirconia ceramics contain ZrO ₂ as a main component and contain Y ₂ O ₃ , MgO, CaO, CeO ₂ or the like as a stabilizer.
[0022]
The height h1 of the gap s between the head upper surface 2b and the contact surface 3c of the holder 3 with the upper surface 2b is preferably in the range of 2 to 6 mm. If the height h1 is smaller than 2 mm, a large amount of radiant heat from the upper surface 2b of the head 1 may be transmitted to the holder 3. On the other hand, if the height h1 is larger than 6 mm, the strength of the lower end of the holder 3 becomes insufficient. There is fear.
[0023]
Further, the height h2 of the sliding surface 4 of the head 1 is preferably in the range of 2 to 6 mm. If the height h2 is 2 mm or less, the head 1 may be caught in the concave portion of the tilt holder 3, while if it is larger than 6 mm, the volume of the head 1 is large and the heating efficiency tends to be deteriorated. .
[0024]
Example The heater 10 shown in FIG. 1 was manufactured by setting the height h1 of the gap s and the height h2 of the sliding surface 4 of the head 1 to 5 mm.
[0025]
The ceramic material of the heater 10 was made of a silicon nitride material manufactured by Kyocera Corporation. The heat transfer member 1a was made of SN281 material, the heating member was made of SN362 material, and the holder 3 was made of SN220 material. Among them, the SN281 and SN362 grades correspond to the high thermal conductive ceramics, and the remaining SN220 grades correspond to the low thermal conductive ceramics.
[0026]
The heater 10 was mounted on the main body of the apparatus, and electric power (1000 W, 1500 W, 2000 W) was applied while the head 1 was lowered as shown in FIG. . The result is shown in FIG.
[0027]
Further, the rising time and the temperature at the central portion of the tip of the head 1 were similarly measured in a state where the head 1 was raised as shown in FIG. The result is shown in FIG.
[0028]
As is clear from FIGS. 4 and 5, the heating efficiency when the head 1 is lowered as shown in FIG. 1 is remarkably better than that when the head 1 is raised as shown in FIG. This means that the heat transmission from the head 1 to the holder 3 was small in the state of FIG. 1, and the heater 10 of the present invention was powered on in this state, thus confirming the effectiveness of the present invention. You can do it.
[0029]
【The invention's effect】
As described above, according to the present invention, a ceramic head for contact heating of an object to be heated is made freely movable in and out of a holder of the apparatus main body, and when the head is heated, the head upper surface and the holder are connected. A heater is configured so that the upper surface of the head comes into contact with the holder when contacting and heating the object to be heated by pressing the object to be heated, so that the head is heated only in a narrow area when heating the head. Heating time is greatly shortened by contacting with the holder and thereby minimizing heat radiation to the holder. Since the head is firmly held down, the parallelism of the head can be maintained accurately, and when cooling in a pressed state, the top surface of the head is in contact with the holder, that is, in a wide area In the head of the heat is propagated in an appropriate amount holder, the time required for cooling due to its action short.
[0030]
Therefore, the heating time and the cooling time are shortened and the parallelism of the head is maintained well, so that the production efficiency can be greatly improved.
[Brief description of the drawings]
FIG. 1 is an end view of a heater according to the present invention.
FIG. 2 is an end view of the heater of FIG. 1, showing a state in which a head is in contact with an object to be heated.
FIG. 3 is a partially enlarged view showing a heater according to another embodiment of the present invention.
4 is a graph showing a rise time and a temperature at a central portion of a tip end of a head when power is supplied in the state of FIG. 1 in the embodiment using the heater of FIG. 1;
5 is a graph showing a rise time and a temperature at a central portion of a head tip when power is supplied in the state of FIG. 2 in the embodiment using the heater of FIG. 1;
FIG. 6 is an explanatory view schematically illustrating how to use a heater in a flip chip connection method.
FIG. 7 is an end view of a conventional heater.
[Explanation of symbols]
s Gap h1, h2 Height 1 Head 1a Heat transfer section 2 Heating section 2a Heating element 2b Head upper surface 3 Holder 3b Recess 3c Contact surface 4 Sliding surface 5 Bearing 10 Heater

Claims (1)

A ceramic head is provided at the tip of the holder to contactly heat the object to be heated, and the head is freely movable in and out of the holder, and when the object to be heated is pressed by contact heating, the head is heated. A heater for contact heating, wherein the upper surface and the holder are configured to contact each other.

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