JP2005072369A - Manufacturing method of semiconductor device - Google Patents

Abstract

A warpage correction method improved so that warpage generated in a copper base due to solder bonding with an insulating substrate having a small coefficient of linear expansion can be corrected in a short time with less energy consumption.
Heat is applied to an assembly of a semiconductor device in which an insulating substrate 3 on which seven semiconductor chips are mounted is placed on a copper base 1 and solder-bonded, from the insulating substrate side while the copper base is kept at a low temperature. After raising the temperature of the solder layer 9 to a temperature close to the melting point at which creep deformation is likely to occur, the heating is stopped and the temperature is returned to room temperature. In this process, the warp of the copper base generated during the solder bonding between the copper base and the insulating substrate is In the correction process, the heating block 15 preheated to a high temperature by the heater 15 is transferred onto the insulating substrate 3 and the solder layer 9 is moved from the substrate side. After the temperature is raised to a temperature close to the melting point by heat transfer, the heating block is removed and the temperature is returned to room temperature. During this time, the precooled cooling block 16 is applied to the back side of the copper base to keep it at a low temperature.
[Selection] Figure 1

Description

  The present invention relates to a method for correcting warpage generated in a copper base when an insulating substrate having a different linear expansion coefficient and a copper base are solder-bonded in a manufacturing process of a power semiconductor module.

First, an assembly structure of a power semiconductor module that is an object of the present invention is shown in FIG. In the figure, 1 is a copper base of a package, 2 is an enclosing case for a resin molded product, 3 is a copper circuit pattern 5 and a back solid copper foil 6 directly on both upper and lower surfaces of a ceramic plate 4 made of Al2 O3, AlN, etc. Bonded Direct Bonding Copper substrate, 7 is a semiconductor chip solder-mounted on the copper circuit pattern 5 of the insulating substrate 3, and 8 is an external lead-out terminal (lead frame) that is solder-bonded to the copper circuit pattern 5 and drawn to the outside. The insulating substrate 3 is solder-bonded with the back solid copper foil 6 superimposed on the upper surface of the copper base 1. Reference numerals 9, 10, and 11 represent bonding solder layers between the copper base / insulating substrate, between the insulating substrate / semiconductor chip, and between the insulating substrate / external lead terminals, respectively.
When using the power semiconductor module having the above-described configuration, the bolt 13 is passed through the mounting holes 1a that are perforated at both ends of the copper base 1 by superimposing the copper base 1 on the end face of the radiating fin (heat sink) 12 as shown in the figure. The heat generated by the semiconductor chip 7 is transferred to the insulating substrate 3 and the copper base 1 and radiated from the heat radiating fins 12 to the atmosphere side by fastening and fixing to the heat radiating fins.

Here, in order to solder-bond the insulating substrate 3 to the copper base 1 in the assembling process of the semiconductor module, a solder foil is sandwiched between the copper base 1 and the insulating substrate 3 or a solder cream is applied. It is carried into a heating furnace in an assembled state, and is soldered by heating to a temperature equal to or higher than the melting point of the solder.
By the way, after soldering the insulating substrate 3 to the copper base 1 by the above method, when the assembly is taken out from the heating furnace and returned to room temperature (room temperature), the copper base 1 is warped as shown in FIG. The part is concave. This warpage is caused by a so-called bimetal action resulting from a difference in linear expansion coefficient between the copper base 1 and the insulating substrate 3. That is, the equivalent linear expansion coefficient of the insulating substrate 3 is a value approximating the linear expansion coefficient of the ceramic alone (4.6E-6 / K to 7.1E-6 / K), and the linear expansion coefficient of the copper base 1 (16.5E-6 Very small compared to / K). For this reason, when the temporary assembly is heated to the melting point of the solder or higher and soldered between the copper base 1 and the insulating substrate 3 as described above and then cooled to room temperature, the heat shrinkage of the copper base 1 is reduced to the insulating substrate 3. Therefore, the warp such that the central portion of the bottom surface is concave is generated. Moreover, if the semiconductor module is attached to the heat radiating fin 12 with the copper base 1 warped, the bottom surface of the copper base 1 and the heat radiating fin 12 do not adhere to each other as shown in FIG. However, the problem arises that the heat transfer between the module and the heat radiating fins is extremely lowered and the required heat radiating performance cannot be exhibited.

On the other hand, in order to avoid the copper-based warp as described above, the following measures are conventionally known.
(1) Predicting the amount of warpage of the copper base 1, the copper base is processed into a convex shape in advance, and the warp generated when soldering the insulation base 3 is compensated to return to room temperature. The bottom surface of the copper base 1 is made substantially flat.
(2) With the bottom surface of the copper base 1 warped in a concave shape by soldering to the insulating substrate 3, this assembly is placed on a dish-shaped press mold whose surface is concave in the direction opposite to the warp of the copper base. The solder is heated up to a temperature at which the solder can be plastically deformed by a heater provided in the press die, and the copper base 1 is pressed against the surface shape of the press die in this temperature rising state. Warp is corrected (for example, refer to Patent Document 1).
Japanese Patent Publication No.7-110491

By the way, the conventional correction method described above has the following problems.
That is, in the method of the above item (1), when the length dimension of the copper base 1 which is a joining member is increased, the warpage amount increases in proportion to the square of the length, so that the processing amount of the copper base is increased. For this reason, when the flat insulating substrate 3 is placed on the copper base 1 in the assembly process of the semiconductor device, a gap is generated between the copper base 1 and the insulating substrate 3, or solder bonding is not possible. A defect in which the joint remains is generated.
In the method of (2) above, the solder / bonded board / copper base assembly is placed on a press die and heated to a temperature at which the solder including the copper base can be plastically deformed (creep deformation). In addition, the copper base thermally shrinks during the cooling process to return to room temperature after heating. Therefore, when pressing the copper base in accordance with the dish-shaped press mold, it is necessary to allow for the amount of warpage generated in the cooling process and to give more reverse warping deformation. There is a possibility that the solder bonding between the insulating substrates may be peeled off. Furthermore, the heating time required to raise the solder to a temperature at which plastic deformation can be performed with the copper base placed on the press die is long, and after heating, the copper base is gradually cooled to room temperature with pressure applied. Therefore, there is a problem that the throughput time of the warp correction process becomes long and the heat energy consumed increases. Furthermore, Sn-Pb solder has been the mainstream in power semiconductor modules in the past. However, recently, solder containing no Pb, for example, Sn-Ag solder tends to be used due to environmental problems. In addition, the Sn-Ag solder has a higher melting temperature than the Sn-Pb solder, and for this reason, the conventional warp correction method takes a long time to work and lowers the throughput.

  The present invention has been made in view of the above points, and has been improved so that warpage generated in a copper base due to solder bonding with an insulating substrate having a small linear expansion coefficient can be effectively corrected in a short time and with less energy consumption. An object of the present invention is to provide a copper-based warpage correction method for a semiconductor device.

The above object can be achieved by the correction method described below according to the present invention.
That is, heat is applied from the insulating substrate side to the assembly of the semiconductor device in which the insulating substrate on which the semiconductor chip is mounted is placed on the copper base and solder-bonded, and the solder base is kept at a low temperature. After the temperature of the layer is raised to a temperature close to the melting point at which creep deformation is likely to occur, heating to the insulating substrate is stopped and returned to room temperature to correct the warp of the copper base (Claim 1). This can be realized by adopting the means described in the following sections.
(1) As a means of heating the insulating substrate in the warp correction process, a heating block preheated to a high temperature is applied to the surface of the insulating substrate to raise the temperature of the solder layer to a high temperature state. Before the temperature of the copper base becomes high due to heat conduction, the heating block is removed from the insulating substrate so as to return to normal temperature.

(2) For the heating block used in the preceding item (1), a metal block body having a high thermal conductivity and a heat capacity necessary for raising the temperature of the solder layer to near the melting point is used.
(3) The heating block used in (2) above has a concave surface on the insulating substrate, and the surface has a concave so as to avoid unnecessary interference with the semiconductor chip mounted on the insulating substrate. It is formed (claim 4).
(4) The heating block used in the preceding item (2) is composed of an assembly of movable blocks that can be individually displaced according to the shape of the surface of the insulating substrate and the shape of the semiconductor chip mounted on the substrate. 5).
(5) Instead of using the heating block as a means for heating the insulating substrate, the solder layer is heated to a high temperature state by blowing a high-temperature gas heated to a temperature close to the melting point of the solder onto the surface of the insulating substrate. And before the copper base is heated to a high temperature state due to heat conduction from the high temperature gas, the blowing of the high temperature gas is stopped to return to the normal temperature (Claim 6).

(6) In the correction method of each of the above items, as a means for holding the copper base at a low temperature while being heated from the insulating substrate side, a cooling block that has been pre-cooled to a low temperature is applied to the bottom side of the copper base. (Claim 7).
(7) As means for keeping the copper base in a low temperature state, low temperature cooling air is blown to the bottom surface side of the copper base instead of the cooling block used in the preceding item (6).
(8) Further, in the correction method of each of the above items, a pressure is applied to the copper base in a direction to correct the warp in parallel with the heating from the insulating substrate side (claim 9).
As described above, the most significant feature of the warp correction method according to the present invention is that the solder portion is heated to a temperature close to the melting point by rapidly applying heat from the insulating substrate side while the copper base is kept at a low temperature. According to this method, as described in the following operation, it is possible to correct the warping of the copper base caused by the copper base / insulating substrate solder joint in a short time.

That is, if the linear expansion coefficient of the insulating substrate is αz, the temperature change of the insulating substrate after solder bonding is Tz, the linear expansion coefficient of the copper base is αc, and the temperature change of the copper base after bonding is Tc, the warp The quantity δ is expressed by the following equation (1).
δ = K (αz * Tz−αc * Tc) (1)
Here, in the method of bringing the substrate assembly into the heating furnace and soldering the copper base and the insulating substrate as described above, the temperature change is Tz = Tc, but αz << αc. In the cooling process to return to room temperature after soldering, the copper base is warped in the center of the bottom as described in FIG.
In this case, in order to correct the warp generated in the copper base in as short a time as possible, the temperature at which only the solder layer is likely to undergo creep deformation while the copper base and the insulating substrate are kept at room temperature (lower than the melting point of the solder) It is conceivable to increase the temperature to a temperature close to the melting point as much as possible. In such a state, the solder layer joining the copper base and the insulating substrate creeps and the residual stress of the copper base and the insulating substrate (stress generated by the bimetal action during solder joining) Since it is released, the copper base is restored to its original shape without warping. However, it is practically impossible to raise only a solder layer sandwiched between the insulating substrate and the copper base to a high temperature state by heating from the outside.

Therefore, in the warp correction method of the present invention, heat is applied from the insulating substrate side having a small linear expansion coefficient, and the solder layer is easily creep-deformed by the heat transferred from the insulating substrate while the copper base on the opposite side is kept at a low temperature. The temperature is raised to a temperature to correct the copper-based warpage in a short time.
That is, the coefficient of linear expansion of an insulating substrate mainly composed of a ceramic plate is αz = 5E-6 / K, and the coefficient of linear expansion of a copper base is a value near αc = 16.5E-6 / K. Heat is applied from the insulating substrate side so that the temperature change Tz of the insulating substrate is 200K (220 ° C if the room temperature is 20 ° C), and the heat conduction causes the temperature of the solder layer to reach the melting point (about 183 ° C for Sn-Pb system) It is assumed that the temperature has been raised to a temperature that is slightly lower than At this time, if the temperature change Tc of the copper base is controlled so as to maintain a low temperature of 60K (80 ° C if the room temperature is 20 ° C) at most, the copper base will thermally shrink in the process of returning to normal temperature after stopping the heating. In addition, the warp amount of the copper base can be corrected to almost zero. In this case, if the temperature change of the copper base can be controlled in the range of Tc <60K, the bottom surface of the copper base can be slightly warped.

In this case, since the insulating substrate and the copper base are thermally coupled to each other with the solder layer interposed therebetween, if heat is slowly applied over a long period of time when heat is applied from the insulating substrate side, the copper base of the copper substrate is thermally conductive. Since the temperature rises to a high temperature so as to balance the heat, the above temperature difference cannot be made. Therefore, the heating from the insulating substrate side should be carried out rapidly in as short a time as possible, and the heating condition in that case is that the temperature of the solder layer is lower than the melting point but close to the melting point as much as possible. desirable.
In this regard, when the heating block according to the present invention is used as the heating means for the insulating substrate, the heat flow Q from the heating block to the insulating substrate is given by the following equation (2).
Q = λ (t1-t0) / (l / A) (2)
Therefore, the heating temperature (t1) of the block which uses a material having a high thermal conductivity (λ) is increased for the heating block. Furthermore, if the contact area (A) with the insulating substrate is increased and the heat transfer distance (l) is shortened to improve the heat transfer contact state, the solder layer can be brought into a high temperature state where it can be easily creep-deformed in a short time. It becomes possible.

Moreover, even if the method of spraying high-temperature air on the insulating substrate side instead of the heating block (Claim 6) is adopted, the same function can be achieved. It is also an effective method to cool the copper base in parallel with the heating from the insulating substrate side (claims 7 and 8).
In addition, with the solder layer heated to a high temperature, pressure is applied to the copper base in the direction opposite to the direction of warpage (Claim 9), thereby accelerating the removal of residual stress from the copper base and assisting in warping correction. it can.

  According to the present invention, as compared with the assembly of the semiconductor device in which the insulating substrate on which the semiconductor chip is mounted is placed on the copper base and soldered as described above, the insulating substrate is maintained with the copper base side kept at a low temperature. Solder bonding to the insulating substrate by applying heat rapidly from the side to raise the temperature of the solder layer to near the melting point where creep deformation is likely to occur, and then stopping heating to the insulating substrate and returning it to room temperature. This effectively corrects the warp generated in the copper base in a short time and with a small amount of heat energy.

  The present invention maintains a copper base having a large linear expansion coefficient at a low temperature as a method for correcting the warp generated in the copper base in a short time when the insulating substrate is soldered to the copper base in the assembly process of the semiconductor device. As it is, heat is rapidly applied from the side of the insulating substrate with a low coefficient of linear expansion to raise the solder layer to a temperature close to the melting point, and the warp of the copper base is corrected using the creep deformation of the solder. The means for applying heat from the substrate side and the means for maintaining the copper base at a low temperature can be realized by adopting specific means described in the following embodiments.

FIG. 1 is a diagram showing a warp correction process according to a basic embodiment of the present invention. The assembly of the semiconductor device shown in FIG. In the warp correction process of the copper base 1 against the warp having a concave side), a heating block 14 and a heater 15 for preheating the heating block to a high temperature state are provided.
Here, the heating block 14 is a metal block body made of a material having a high thermal conductivity and a large heat capacity, and its outer size corresponds to the insulating substrate 3 and the copper base 1 of the semiconductor device. Further, the heater 15 is heated to a built-in heater to heat the heating block 14 to a temperature close to the melting point of solder (solder that connects the copper base 1 and the insulating substrate 3) (for example, Sn-Pb solder is about 183 ° C.). Keep it preheated.
Then, when a substrate assembly in which the insulating substrate 3 is solder-bonded to the copper base 1 in the semiconductor device assembly process (warping of the copper base) arrives at the warp correction process, it is placed on the heater 15 and preheated to a high temperature state. The previously heated block 14 is moved from the heater 15 and placed on the insulating substrate 3 as shown. As a result, the heat held by the heating block 15 is transferred to the solder layer 9 bonded to the copper base 1 via the insulating substrate 3, and the solder is heated to a temperature close to the melting point at which creep deformation easily occurs. . In this case, the temperature of the copper base 1 bonded to the opposite side of the insulating substrate 3 with the solder layer 9 interposed therebetween is from room temperature (room temperature) to several tens of degrees Celsius due to heat transfer from the heating block 14, and at most about 100 degrees Celsius. When the temperature rises, the heating block 14 is removed from the insulating substrate 3 and returned to the heater 15 so that the copper base 1 does not reach a higher temperature, and gradually cooled from this state to room temperature.

In this heating and slow cooling process, the solder layer 9 is once heated to a temperature at which creep deformation is possible. As a result, the warp residual stress generated in the solder joint with the insulating substrate 3 disappears from the copper base 1, and the warp is corrected by restoring the original flat shape. Returning to the original solid phase, the copper base 1 is integrated with the insulating substrate 3 with the warp corrected.
In addition, the warp correction process of this embodiment includes a cooling block 16 and a cooler 17 that are metal blocks similar to the heating block 14 as shown in the drawing, in addition to the heating block 14 and the heater 15. The cooling block 16 is precooled by a cooler 17.
Then, in the process of moving the heating block 14 onto the insulating substrate 3 and correcting the warp of the copper base 1 as described above, the cooling block 16 that has been pre-cooled in advance is applied to the back surface of the copper base 1 to form copper. The base is kept at a low temperature. By using this cooling block 16 together, it is possible to suppress the temperature of the copper base 1 from rising due to heat transfer from the heating block 14, thereby suppressing the copper base 1 from being thermally contracted during the cooling process. Warping correction can be performed stably.

  Further, as a means for holding the copper base 1 in a low temperature state in the warp correction step, instead of using the cooling block 16, low temperature cooling air can be blown on the back surface of the copper base 1.

Next, an embodiment corresponding to claim 4 of the present invention will be described with reference to FIG. In this embodiment, when the heating block 14 described in the first embodiment is placed on the insulating substrate 3 and heat is applied, the heating block 14 is heated so that the heat retained in the heating block 14 is efficiently transferred to the insulating substrate 3. This is an improved block shape.
Therefore, the shape of the lower surface of the heating block 14 (opposite surface to the insulating substrate 3) has a concave surface corresponding to the standard amount of warpage of the insulating substrate 3 caused by the bimetal action by the solder joint with the copper base 1. In addition, a recess 14 a is formed on the surface so as to avoid unnecessary interference with the semiconductor chip 7 mounted on the insulating substrate 3. Thus, in a state where the heating block 14 is placed on the insulating substrate 3, the surface of the heating block directly overlaps the surface of the insulating substrate 3 over a wide range as shown in the drawing and is in heat transfer contact. Thereby, the heat held in the heating block 14 can be efficiently transferred to the insulating substrate 3 and the solder layer 9 can be rapidly heated to a temperature close to the melting point.

Next, with respect to the heating block 14 described in the second embodiment, an embodiment corresponding to claim 5 of the present invention, which has been improved so as to enhance versatility, is shown in FIGS. 3 (a) and 3 (b).
That is, the heating block 14 shown in FIG. 2 forms the recess 14a in accordance with the size of the insulating substrate 3 and the number and arrangement of the semiconductor chips 7 mounted on the substrate. It cannot be applied to other types of semiconductor devices having different arrangements.
Therefore, in this embodiment, the heating block 14 is composed of an assembly of columnar movable blocks 14b divided into a large number of pieces, and each movable block 14b is individually connected to the support frame 14c via a connecting pin (through pin) 14d. Supports slidable up and down. A long hole 14b-1 is perforated in the movable block 14b, and the long hole 14b-1 is suspended and supported through a connecting pin 14d.

By using the heating block 14 configured as described above, when the movable block 14b is placed on the insulating substrate 3 as shown in the drawing, the individual movable blocks 14b are adapted to the shape and arrangement of the insulating substrate 3 and the semiconductor chip 7 in the vertical direction. As a result of the displacement, a heat transfer contact state similar to that described with reference to FIG.
In addition to using the movable block 14b in a free state, it is also possible to position each movable block 14b in accordance with the model of the semiconductor device that corrects the warp, and then bind it to this position for use. It is.

Next, an application example corresponding to claim 6 of the present invention is shown in FIG. In this embodiment, instead of the heating block shown in each of the previous embodiments, the insulating substrate and the joining solder are heated using heated air.
That is, the warp correction process of the copper base 1 is provided with the air heater 18 and the wind shielding wall 19, and the substrate assembly of the semiconductor device carried into the correction process is set as illustrated. In this state, air heated to a high temperature (a temperature close to the melting point of the solder layer 9) by the heater 18a of the air heater 18 is blown toward the upper surface of the insulating substrate 3 through the air guide 18 by the blower fan 18b. The wind shield wall 19 serves to prevent the hot air 20 blown from the air heater 18 from directly hitting the copper base 1.
Thereby, the heat of the hot air 20 blown out from the air heater 18 strikes the insulating substrate 3 and is transferred to the solder layer 9 to raise the solder to a temperature close to the melting point. Here, when the solder layer 9 joining the copper base 1 and the insulating substrate 3 is heated to a temperature close to the melting point at which creep deformation easily occurs, the copper base 1 is brought into a high temperature state by heat conduction from the solder layer 9. Before becoming, after the operation of the air heater 18 is stopped, it is gradually cooled to room temperature. As a result, the warp generated in the copper base 1 is corrected as in the case of using the heat block of the previous embodiment.

Also in the above-described Examples 2 to 4, in order to keep the copper base 1 at a low temperature during the warp correction process, the cooling block 16 (see FIG. 1) is provided on the back side of the copper base 1 in the same manner as described in Example 1. Of course, it can be carried out in combination with cooling means such as applying a reference) or blowing cooling air.
Further, as an application example of the present invention, in the warp correction process of the copper base 1 described in each of the foregoing examples, the copper base 1 is generated in the base in parallel with the heating operation from the insulating substrate 3 side. There is a method in which a mechanical pressure is applied using a jig (not shown) from the opposite direction to warping to assist warpage correction. In this way, by applying pressure to the copper base 1 in the opposite direction to the warp while the solder layer 9 is in a high temperature state, it is possible to correct the warp in a short time by accelerating the removal of the plate residual stress remaining on the copper base. it can.

Explanatory drawing showing the copper base curvature correction process which concerns on Example 1 of this invention. Explanatory drawing showing the copper base curvature correction process which concerns on Example 2 of this invention. Explanatory drawing showing the copper base curvature correction process which concerns on Example 3 of this invention. Explanatory drawing showing the copper base curvature correction process which concerns on Example 4 of this invention. Assembly structure diagram of power semiconductor module which is an object of the present invention FIG. 5 is a diagram showing a warpage occurrence state of a board assembly generated by solder bonding between a copper base and an insulating board in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Copper base 3 Insulation board | substrate 4 Ceramic board 5 Copper circuit pattern 6 Back solid copper foil 7 Semiconductor chip 9 Solder layer which joined between copper base / insulation board 12 Radiation fin 14 Heating block 15 Heater 16 Cooling block 17 Cooler 18 Air Heater

Claims (9)

The temperature of the solder layer is obtained by applying heat from the insulating substrate side while keeping the copper base side at a low temperature for the assembly of the semiconductor device in which the insulating substrate on which the semiconductor chip is mounted is placed on the copper base and soldered. After heating up to a temperature close to the melting point where creep deformation is likely to occur, heating to the insulating substrate is stopped and the temperature is returned to room temperature to correct the warping of the copper base that occurs during the solder bonding process with the insulating substrate. A method for manufacturing a semiconductor device. 2. The manufacturing method according to claim 1, wherein a heating block preheated to a high temperature is applied to the surface of the insulating substrate as a heating means for the insulating substrate to heat the solder layer to a high temperature state, and the heating block A method of manufacturing a semiconductor device, wherein the heating block is removed from the insulating substrate and returned to room temperature before the copper base is heated to a high temperature state due to heat conduction. 3. The method of manufacturing a semiconductor device according to claim 2, wherein the heating block is a metal block body having high thermal conductivity and a heat capacity necessary for raising the temperature of the solder layer to near the melting point. . 3. The manufacturing method according to claim 2, wherein the heating block applied to the insulating substrate has a concave surface, and a concave portion is formed on the surface to avoid interference with a semiconductor chip mounted on the insulating substrate. A method of manufacturing a semiconductor device. 3. The manufacturing method according to claim 2, wherein an assembly of movable blocks that can be individually displaced according to the surface shape of the insulating substrate and the shape of the semiconductor chip mounted on the substrate is used as the heating block. A method for manufacturing a semiconductor device. 2. The manufacturing method according to claim 1, wherein as a means for heating the insulating substrate, a high-temperature gas heated to a temperature close to the melting point of the solder is blown onto the surface of the insulating substrate to raise the temperature of the solder layer to a high temperature state. A method for manufacturing a semiconductor device, characterized in that before the copper base is heated to a high temperature state by heat conduction from the high temperature gas, the blowing of the high temperature gas is stopped to return to the normal temperature. 2. The semiconductor device according to claim 1, wherein a cooling block precooled to a low temperature in advance is applied to the bottom surface side of the copper base as means for holding the copper base at a normal temperature. Device manufacturing method. 2. The method of manufacturing a semiconductor device according to claim 1, wherein cold air cooled to a low temperature is blown to a bottom surface side of the copper base as means for holding the copper base at a normal temperature. 2. The method of manufacturing a semiconductor device according to claim 1, wherein a pressure is applied to the copper base in a direction to correct warpage in parallel with the heating operation from the insulating substrate side.

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