JP2010267769A - Soldering method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a soldering method and apparatus capable of performing the soldering without scattering foreign matters in a cooler when pressure-reducing with (air pressure-varied) an atmosphere chamber during the soldering of an element relative to a substrate of a cooler equipped with an insulating substrate. <P>SOLUTION: When a semiconductor element 11 is soldered relative to a substrate 12 of a cooler 10 equipped with an insulating substrate by this soldering apparatus 30, the inside of a chamber 31 is pressure-reduced by a vacuum pump 33 through an intra-chamber exhaustion piping 32 in a state in which couplers 36a, 36b attached to an intra-cooler exhaustion piping 34 connected to the vacuum pump 33 are fitted to the inlet and outlet of the cooler 16. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a soldering method and apparatus for mounting an element on a substrate in an atmosphere chamber in a vacuum state or an atmospheric gas state.

  Conventionally, power modules have adopted a laminated structure of element-solder-insulating substrate-solder heat sink-grease-cooler. However, the power module for high withstand voltage and large current mounted in a hybrid vehicle or electric vehicle has a large amount of self-heating during the operation of the semiconductor element, so it is necessary to have a cooling structure with high heat dissipation. There is a tendency to employ a laminated structure of a cooler with an element, a solder, and an insulating substrate.

  Here, as a technique for soldering the element to the substrate, for example, there is one described in Patent Document 1. In the technique described here, soldering is performed in an atmosphere gas state or a vacuum state in a small atmosphere chamber. This prevents dust, moisture, and oxygen from being involved during soldering and ensures soldering reliability. In recent years, lead-free solder has been used from the viewpoint of environmental problems. However, since lead-free solder has poor wettability, the air pressure in the atmosphere chamber is forcibly changed during the process, and Improvements have been made to improve attachment.

Japanese Patent Application Laid-Open No. 06-029659

  However, in order to improve the cooling performance of the cooler with an insulating substrate, the internal flow path structure has a complicated shape, so that a large number of foreign matters (such as processing waste) are generated during the production. Remains attached to the product. Therefore, the inside of the cooler is cleaned during manufacturing and after completion of the product to remove foreign matter. However, since the flow path structure has a very complicated shape, the normal cleaning must completely remove foreign matter. The fact is that it is not possible.

  When an element is soldered to a substrate provided in such a cooler with an insulating substrate, foreign matter remaining in the cooler is removed from the atmosphere due to reduced pressure (atmospheric pressure fluctuation) in the atmosphere chamber when soldering. It will be scattered indoors. Then, foreign matter scattered in the atmosphere chamber adheres to the element, and when the temperature of the element rises during soldering, the foreign matter adheres to the element, and even if the atmosphere chamber is exhausted, etc. There was a problem if the foreign matter stuck on the top could not be removed. As described above, when the foreign matter is attached to the element, the element performance is deteriorated, so that the power module becomes a defective product.

  Here, in order to prevent the scattering of foreign matter in the cooler, it may be possible to perform soldering by attaching a cap or the like to the inlet / outlet of the cooler, but when reducing the pressure in the atmosphere chamber (pressure fluctuation) The cap or the like may be removed or damaged due to a difference in atmospheric pressure generated between the generated atmosphere chamber and the cooler. For this reason, it is not possible to prevent scattering of foreign matter in the cooler into the atmosphere chamber. In addition, the atmosphere chamber may be damaged by broken cap pieces or the like.

  Therefore, the present invention has been made to solve the above-described problems, and when soldering an element to a substrate of a cooler with an insulating substrate, cooling is performed when the atmosphere chamber is depressurized (atmospheric pressure fluctuation). It is an object of the present invention to provide a soldering method and apparatus capable of performing soldering without scattering foreign matter in the vessel.

  The present invention has been made to solve the above-mentioned problems. In the method of soldering an element to a substrate of a cooler with an insulating substrate in a chamber, an exhaust path different from that of the chamber when the pressure in the chamber is reduced. The inside of the cooler is depressurized using a soldering to perform soldering.

  In this soldering method, when the element is soldered to the substrate of the cooler with an insulating substrate, the chamber is depressurized (atmospheric pressure) in order to remove oxygen in the chamber and prevent voids from being generated in the solder. fluctuate. At this time, the inside of the cooler is also decompressed using an exhaust path different from the chamber.

  Specifically, for reducing the pressure in the cooler, a coupler with a pipe is attached to the inlet / outlet of the cooler, and the other end of the pipe is connected to an exhaust vacuum pump in the chamber. Just do it.

  As a result, the cooler is exhausted almost simultaneously with the exhaust in the chamber, so even if the pressure is reduced (atmospheric pressure fluctuation) in the chamber, there is almost no pressure difference between the chamber and the cooler. Further, since the volume of the cooler is smaller than the volume of the chamber, the pressure in the cooler is reduced more quickly than in the chamber. For these reasons, it is possible to reliably prevent the coupler attached to the inlet / outlet of the cooler from being detached or damaged when the pressure in the chamber is reduced (atmospheric pressure fluctuation). Therefore, foreign matter in the cooler can be reliably prevented from scattering into the chamber, so that the element can be soldered well to the substrate of the cooler with an insulating substrate.

  In the soldering apparatus for performing the above-described soldering method, a chamber constituting a sealed space for housing the cooler with an insulating substrate and the element, a chamber exhaust system for decompressing the inside of the chamber, and the cooling A cooler exhaust system for decompressing the interior of the chamber, and when the interior of the chamber is decompressed by the chamber exhaust system, the interior of the cooler may be decompressed by the cooler exhaust system.

  With such a soldering apparatus, the above-described soldering method can be reliably performed, and soldering can be performed without scattering foreign matter in the cooler.

  According to the soldering method and apparatus of the present invention, as described above, when the element is soldered to the substrate of the cooler with an insulating substrate, when the atmosphere chamber is depressurized (atmospheric pressure fluctuation), Soldering can be performed without scattering foreign matter.

It is sectional drawing which shows schematic structure of the cooler with an insulated substrate which solders a semiconductor element. It is a figure which shows schematic structure of a soldering apparatus. It is a figure which shows the state which has arrange | positioned the cooler with an insulated substrate in a chamber. It is a figure which shows the state which has arrange | positioned the semiconductor element through the solder to the cooler with an insulated substrate. It is a figure which shows the state which is soldering.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the soldering method of the present invention will be described below in detail with reference to the drawings. First, a cooler with an insulating substrate for soldering (mounting) a semiconductor element by the soldering method according to the present embodiment will be described with reference to FIG. FIG. 1 is a sectional view showing a schematic configuration of a cooler with an insulating substrate for soldering a semiconductor element.

  As shown in FIG. 1, the cooler 10 with an insulating substrate includes a substrate 12 on which a semiconductor element 11 (see FIG. 4) is mounted, a cooler 16 having a refrigerant flow path, a substrate 12 and the cooler 16. And a stress relaxation member 17 that is interposed between the stress relaxation members 17 to relieve stress strain caused by a difference in linear expansion coefficient between the two.

  The substrate 12 includes a ceramic insulating substrate 13 and high-purity aluminum 14 and 15 provided on the upper and lower surfaces thereof. The ceramic insulating substrate 13 may be made of any ceramic as long as the required insulating properties, thermal conductivity, and mechanical strength are satisfied. For example, aluminum oxide or aluminum nitride is applicable, and here, aluminum nitride (AlN) is used as the ceramic insulating substrate 13. The high-purity aluminum 14 and 15 may have a purity of 99.99% or higher.

  In the cooler 16, a fin member 19 is accommodated in a two-divided case 18 provided with a refrigerant inlet / outlet, and the fin member 19 forms a flow path through which the refrigerant flows. Each component constituting the cooler 16 is formed of an aluminum member having high thermal conductivity and light weight, and each component is brazed. As the brazing material, an aluminum brazing material such as an Al—Si based alloy or an Al—Si—Mg based alloy is used.

  Here, the cooler 16 has a complicated flow path configuration using fin members 19 having a complicated shape in order to improve the cooling performance. In order to enable such a flow path configuration, the fin member 19 has a fine shape, and the foreign matter generated during the manufacturing process remains in the cooler 16 without being completely removed. . This foreign matter cannot be completely removed by normal cleaning performed during manufacture and after the product is completed.

  The stress relaxation member 17 is made of a material having high thermal conductivity, and is provided with several stress absorption spaces. As the stress relaxation member 17, for example, an aluminum plate having a purity of 99.99% or more and having a plurality of through holes arranged in a staggered manner (so-called punching aluminum) can be used. The linear expansion coefficient of the stress relaxation member 17 made of high-purity aluminum is 23.5 ppm / ° C., which is equal to the intrinsic value of aluminum. High-purity aluminum is a relatively soft material with a Young's modulus of 70.3 GPa, and has a large deformation with respect to stress. Therefore, the stress strain due to the difference in linear expansion coefficient between the aluminum cooler 16 and the ceramic insulating substrate 13 can be alleviated.

  Then, in order for the substrate 12 and the stress relaxation member 17 to efficiently transfer the heat generated from the semiconductor element 11 mounted (soldered) to the substrate 12 to the cooler 16, it is directly brazed onto the cooler 16 by brazing. The cooler 10 with the insulating substrate is formed by bonding. As the brazing material, an aluminum brazing material such as the Al—Si based alloy and the Al—Si—Mg based alloy described above is used.

Next, a soldering apparatus for performing the soldering method of the present invention will be briefly described with reference to FIG. FIG. 2 is a diagram showing a schematic configuration of the soldering apparatus.
As shown in FIG. 2, the soldering apparatus 30 includes a chamber 31, a chamber exhaust pipe 32, a vacuum pump 33, a cooler exhaust pipe 34, and a heater 35.

  The chamber 31 is a sealed space in which the cooler with an insulating substrate 10 and the semiconductor element 11 that are objects to be soldered can be accommodated. An in-chamber exhaust pipe 32 is connected to the chamber 31. The other end of the in-chamber exhaust pipe 32 is connected to the vacuum pump 33. Thereby, the inside of the chamber 31 can be decompressed by operating the vacuum pump 33. In the present embodiment, the “chamber exhaust system” of the present invention is configured by the in-chamber exhaust pipe 32 and the vacuum pump 33.

  The vacuum pump 33 is connected to an in-cooler exhaust pipe 34. The cooler exhaust pipe 34 is bifurcated, and detachable couplers 36 a and 36 b are attached to the inlets and outlets of the cooler 16 at the respective ends. By installing these couplers 36a and 36b at the inlet / outlet of the cooler 16 and operating the vacuum pump 33, the inside of the cooler 16 can be decompressed. In the present embodiment, the “cooler exhaust system” of the present invention is configured by the cooler exhaust pipe 34 and the vacuum pump 33.

  The heater 35 is provided at the bottom of the chamber 31, and when soldering is performed, the cooler 10 with an insulating substrate disposed on the upper surface of the heater is heated, and the solder 40 disposed on the substrate (see FIG. 4).

  Next, the procedure for carrying out the soldering method of the present invention using the above-described soldering apparatus 30 will be described with reference to FIGS. FIG. 3 is a view showing a state in which a cooler with an insulating substrate is arranged in the chamber. FIG. 4 is a diagram showing a state in which a semiconductor element is arranged via a solder in a cooler with an insulating substrate. FIG. 5 is a diagram illustrating a state in which soldering is performed.

  First, the cooler 10 with an insulating substrate is disposed in the chamber 31. Specifically, as shown in FIG. 3, the cooler 10 with an insulating substrate is disposed on the upper surface of the heater 35 so that the cooler 16 is in contact with the heater 35. Thereafter, the couplers 36 a and 36 b of the in-cooler exhaust pipe 34 are attached to the inlet / outlet of the cooler 16.

Subsequently, as shown in FIG. 4, the semiconductor element 11 is placed on the upper surface of the substrate 12 (more precisely, the upper surface of the high-purity aluminum 14) of the cooler 10 with an insulating substrate disposed in the chamber 31. Deploy.
Note that the couplers 36 a and 36 b can be mounted at the inlet / outlet of the cooler 16 after the semiconductor element 11 is arranged first. In this case, however, the arrangement position of the semiconductor element 11 may be shifted when the coupler is mounted. For this reason, it is better to attach the couplers 36a and 36b first than the arrangement of the semiconductor element 11.

  Thereafter, the heater 35 is operated while the vacuum pump 33 is operated to change the atmospheric pressure in the chamber 31, and the cooler 10 with the insulating substrate is heated. When the cooler 10 with the insulating substrate is heated, the solder 40 disposed on the substrate 12 is melted, and the substrate 12 and the semiconductor element 11 are soldered.

  Here, when the inside of the chamber 31 is depressurized, if the vacuum pump 33 is activated, the cooler exhaust pipe 34 is connected to the vacuum pump 33, so that the inside of the cooler 16 is depressurized almost simultaneously. For this reason, when the inside of the chamber 31 is depressurized, there is almost no pressure difference between the inside of the chamber 31 and the inside of the cooler 16. Further, since the volume of the cooler 16 is smaller than the volume of the chamber 31, the pressure in the cooler 16 is reduced more quickly than in the chamber 31. For these reasons, it is possible to reliably prevent the couplers 36a and 36b attached to the inlet / outlet of the cooler 16 from being detached or damaged when the atmospheric pressure in the chamber 31 is changed. As a result, since foreign matters remaining in the cooler 16 are not scattered in the chamber 31 during soldering, the semiconductor element 11 can be satisfactorily soldered to the substrate 12.

  As described above, according to the soldering method according to the present embodiment, the couplers 36a and 36b attached to the cooler exhaust pipe 34 connected to the vacuum pump 33 with respect to the inlet / outlet of the cooler 16. In a state where is mounted, the inside of the chamber 31 is depressurized by the vacuum pump 33 via the in-chamber exhaust pipe 32. For this reason, since the cooler 16 is exhausted almost simultaneously with the exhaust in the chamber 31, even if the pressure in the chamber 31 is reduced, there is almost no difference in atmospheric pressure between the chamber 31 and the cooler 16. Further, since the volume of the cooler 16 is smaller than the volume of the chamber 31, the pressure in the cooler 16 is reduced more quickly than in the chamber 31. Accordingly, it is possible to reliably prevent the couplers 36a and 36b attached to the inlet / outlet of the cooler 16 from being detached or damaged. Accordingly, it is possible to reliably prevent foreign matter in the cooler 16 from being scattered in the chamber 31, and thus the semiconductor element 11 can be satisfactorily soldered to the substrate 12 of the cooler 10 with an insulating substrate. .

  It should be noted that the above-described embodiment is merely an example and does not limit the present invention in any way, and various improvements and modifications can be made without departing from the scope of the invention. For example, in the above-described embodiment, the inside of the chamber 31 is only depressurized to be in a vacuum state, but the chamber 31 may be filled with an atmospheric gas such as hydrogen.

  In the above-described embodiment, the exhaust in the cooler 16 is performed using the vacuum pump 31 that exhausts in the chamber 31. Of course, a vacuum pump for exhausting the cooler 16 is used. It can also be provided separately. In this case, the vacuum pump for exhausting the cooler is operated simultaneously with the vacuum pump for exhausting the chamber, or the vacuum pump for exhausting the cooler is operated slightly earlier than the vacuum pump for exhausting the chamber. What should I do?

DESCRIPTION OF SYMBOLS 10 Cooler with insulating substrate 11 Semiconductor element 12 Substrate 13 Ceramic insulating substrate 14 High-purity aluminum 15 High-purity aluminum 16 Cooler 17 Stress relaxation member 18 Two-divided case 19 Fin member 30 Soldering device 31 Chamber 32 Chamber exhaust piping 33 Vacuum Pump 34 Exhaust pipe in cooler 35 Heater 40 Solder

Claims (3)

In a method of soldering an element to a substrate of a cooler with an insulating substrate in a chamber,
When depressurizing the inside of the chamber, the soldering method is performed by depressurizing the inside of the cooler using an exhaust path different from that of the chamber. In the soldering method of Claim 1,
Pressure reduction in the cooler is performed using the vacuum pump by attaching a coupler with a pipe to the inlet / outlet of the cooler and connecting the other end of the pipe to a vacuum pump for exhausting in the chamber. A characteristic soldering method. In an apparatus for soldering an element to a substrate of a cooler with an insulating substrate,
A chamber constituting a sealed space for accommodating the cooler with an insulating substrate and the element;
A chamber exhaust system for reducing the pressure in the chamber;
A cooler exhaust system for depressurizing the inside of the cooler,
A soldering apparatus, wherein when the inside of the chamber is decompressed by the chamber exhaust system, the inside of the cooler is decompressed by a cooler exhaust system.

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