JP5136569B2 - Gel injector and method of manufacturing power module using the same - Google Patents

Description

  The present invention relates to a gel injector for injecting a gel used for sealing a power semiconductor element and a method for manufacturing a power module using the gel injector.

  There is a power module configured to include a terminal and a power semiconductor element in a case. In order to obtain a desired electrical connection, when terminals and power semiconductor elements are connected with solder or wires, gel is injected into the case. The gel is injected for the purpose of enhancing the insulating properties in the case and preventing the entry of foreign matter into the case. From the viewpoint of enhancing the insulating properties, it is desirable that the gel seals the power semiconductor element and the like in the absence of impurities such as moisture and bubbles.

  For example, Patent Document 1 describes a semiconductor device that can efficiently remove bubbles mixed in a gel. Patent Document 1 discloses that a through-hole is provided in a vibration damping member that is arranged so as to cover a gel-like resin. And this through-hole is substantially frustoconical, and the cross-sectional area is large toward the lower part. As a result, the gel-like resin bubbles are gathered and enlarged in the process of passing through the through holes. Such air bubbles of the gel-like resin are extracted by the vacuum device via the aforementioned through holes. Therefore, according to the technique disclosed in the cited document 1, an effect of reducing bubbles in the gel-like resin can be obtained. Patent Documents 2 to 4 also describe a technique for improving the quality of the gel.

JP 2003-152136 A Japanese Patent Laid-Open No. 11-040703 JP-A-10-270609 Japanese Patent Laid-Open No. 08-046093

  In the technique disclosed in Patent Document 1, there are cases where removal of bubbles and moisture in a portion to be sealed with gel is insufficient. As a result, there is a problem that air bubbles and moisture remain in the portion to be sealed with the gel, resulting in variations in product quality.

  In particular, in the case of the power module, a power semiconductor element, electrode terminals, and an insulating substrate having a circuit (conductor) pattern formed on the surface are arranged, and these are connected to each other using solder. Grooves and holes of about several tens of microns called “shrinkage cavities” are formed on the surface of the solder, and thus there are many irregularities, which is remarkable when lead-free solder is used. Such unevenness has a problem that moisture and bubbles are easily trapped, and variations in quality such as insulation characteristics tend to occur.

  The present invention has been made to solve the above-described problems, and is a gel injector capable of removing moisture and bubbles in a portion to be sealed with a gel, and a method of manufacturing a power module using the same. The purpose is to provide.

  A gel injector according to the present invention includes a chamber, an injection nozzle that is attached to the chamber and injects a gel into the chamber, a vacuum pump that is connected to the chamber and depressurizes the chamber, and is connected to the chamber And an ultrasonic generator for applying ultrasonic vibration to the chamber.

  A method of manufacturing a power module using a gel injector according to the present invention includes a step of installing a power module having a power semiconductor element therein in a chamber, a pressure reduction in the chamber, and an ultrasonic vibration in the chamber. A step of injecting a gel into the power module so as to seal the power semiconductor element by continuing the application of the reduced pressure and the ultrasonic vibration, and a predetermined amount after injecting the gel A step of continuing the pressure reduction and application of the ultrasonic vibration for a period of time.

  According to the present invention, it is possible to remove moisture and bubbles trapped inside the power module.

It is a figure explaining the gel injector of embodiment. It is a flowchart explaining the manufacturing method of the power module using the gel injector of embodiment. It is a figure explaining the method of sealing the power semiconductor element etc. of a power module with a gel in a chamber. It is a figure explaining the power module by which the power semiconductor element etc. were sealed with the gel.

Embodiments Embodiments will be described with reference to FIGS. 1 to 4. In addition, the same and corresponding components may be denoted by the same reference numerals, and a plurality of descriptions may be omitted.

  FIG. 1 is a schematic view of a gel injector 10 of the embodiment. The gel injector 10 includes a chamber 12. The chamber interior 18 is a space in which gel is injected into the power module. An injection nozzle 16 connected to the gel supply device 15 is attached to the chamber 12 so that the gel can be injected into the chamber interior 18. Further, a vacuum pump (vacuum device) 14 for reducing the pressure inside the chamber 18 is attached to the chamber 12.

  A vibration transmission member 22 is connected to the bottom 20 of the chamber 12. The vibration transmission member 22 is made of, for example, a metal material. The vibration transmitting member 22 is connected to the ultrasonic generator 24. Therefore, when the ultrasonic generator 24 generates ultrasonic vibrations, the chamber 12 (bottom portion 20) vibrates ultrasonically via the vibration transmission member 22.

  FIG. 2 is a flowchart illustrating a method for manufacturing a power module using the gel injector 10 of the embodiment. Hereinafter, the method for manufacturing the power module of the embodiment will be described with reference to FIG. First, in step 50, the power module is installed on the bottom 20 of the chamber interior 18. FIG. 3 shows a state where a power module having a power semiconductor element 66 and the like is installed under the injection nozzle 16 inside the chamber 18.

  Here, the main configuration of the power module in the embodiment is as follows. An insulating substrate 64 is fixed on the metal base plate 60. A metal conductor pattern is provided on the front and back of the insulating substrate 64, and a power semiconductor element 66 such as an IGBT or a diode and a metal electrode terminal 70 are fixed on the conductor pattern on the surface. For these fixings, reflow soldering or the like is often used. Further, in order to electrically connect the power semiconductor element 66 and the conductor pattern on the surface of the insulating substrate 64, wire bonding using a wire 68 such as aluminum is appropriately performed. A resin case 62 surrounding the insulating substrate 64 on which the power semiconductor elements 66 and the like are mounted is fixed to the base plate 60 using an adhesive or the like, and the gel 72 is filled in the case 62. (See FIG. 4).

  When the process in step 50 is completed, the process proceeds to step 52. In step 52, the pressure inside the chamber 18 is reduced, and ultrasonic vibration is applied to the chamber 12. The pressure inside the chamber 18 is reduced by operating the vacuum pump 14. The pressure reduction is performed so that the inside 18 of the chamber is 25 ° C. and about 13 Pa (0.1 Torr) or less, but is not particularly limited thereto. However, as this condition, it is preferable to reduce the pressure to an environment where water (liquid) becomes water vapor (gas) in order to remove moisture. For example, in the case of 25 ° C., it is necessary to set the pressure to 2500 Pa or less. On the other hand, application of ultrasonic vibration to the chamber 12 (bottom portion 20) is performed by the ultrasonic generator 24 via the vibration transmission member 22 as described above. Then, ultrasonic vibration is also applied to the power module installed in the chamber 12 (bottom 20). The vibration direction of the ultrasonic vibration is a horizontal vibration as shown by an arrow in FIG. 3, but is not particularly limited to this.

  When the process in step 52 is completed, the process proceeds to step 54. In step 54, gel is injected into the case 62 of the power module so as to seal the power semiconductor element and the like while maintaining the above-described pressure reduction and maintaining the application of ultrasonic vibration. In the present embodiment, gel injection is performed when the pressure reduction by the vacuum pump 14 progresses and the target value is reached. The injection of the gel is controlled by the gel supply device 15 and is performed from the injection nozzle 16. Examples of the gel include, but are not particularly limited to, a high molecular compound such as a silicone resin having excellent insulation resistance, heat resistance, and cold resistance.

  When the process in step 54 is finished, the process proceeds to step 56. In step 56, the above-described decompression and application of ultrasonic vibration are continued for a certain time (for example, about 5 minutes) after gel injection. When the above steps are completed, a power module in which the gel 72 is filled in the case 62 as shown in FIG. 4 is formed. In the meantime, until the assembly of the power module is completed, after the heat treatment for curing the gel 72 is performed, it is usually necessary to fill and cure the epoxy resin covering the upper portion of the gel 72 and to attach a lid. The

  According to the gel injector of this embodiment and the manufacturing method of a power module using the same, the water | moisture content and air bubble trapped by the unevenness | corrugation etc. inside a power module can be reduced. That is, moisture and bubbles trapped in the irregularities inside the power module vibrate due to ultrasonic vibration from the ultrasonic generator 24. This vibration promotes the removal of moisture and bubbles accompanying the pressure reducing action by the vacuum pump 14. Therefore, since moisture and air bubbles trapped in the unevenness can be reduced, quality variations of the power module can be avoided.

  In the embodiment, the ultrasonic wave is applied to the power module before gel injection (step 52) in order to remove moisture trapped in the irregularities of the power module. That is, even before gel injection, moisture removal by the vacuum device is promoted by ultrasonic vibration.

  In the embodiment, the ultrasonic wave is applied to the power module after the gel injection (step 56) in order to remove dew condensation caused by bringing the gel into contact with the power module. In general, since the power module is thermally dried before the treatment by the gel injector, the temperature is slightly higher than that of the gel at room temperature at the start of gel injection (for example, about 30 to 40 ° C. at a room temperature of 25 ° C.). Degree) the power module is in the state. Therefore, since there is a temperature difference between the gel and the power module, minute condensation occurs due to the temperature difference and moisture contained in the air remaining under reduced pressure, and this condensation may be absorbed into the gel. is there. However, according to the present embodiment, the decompression and the application of ultrasonic vibration are continued even after the gel is injected into the power module. Therefore, moisture absorbed in the gel due to the above-mentioned minute condensation can also be removed.

  Thus, in addition to decompressing the inside of the chamber, it is a feature of the present invention that ultrasonic vibration is applied to the power module to promote the removal of moisture and bubbles. Therefore, the present invention can be widely applied to the case where an element is sealed with a gel.

  In the present embodiment, the gel injection is performed when the pressure reduction by the vacuum pump 14 proceeds and reaches the target value. However, the start of gel injection may be extended for a certain time after the pressure in the chamber 12 reaches the target value. Thereby, reliable moisture removal before gel injection can be performed.

  DESCRIPTION OF SYMBOLS 10 Gel injector, 12 chamber, 14 Vacuum pump, 15 Gel supply apparatus, 16 Injection nozzle, 18 Inside of chamber, 22 Vibration transmission member, 24 Ultrasonic generator

Claims (2)

A chamber;
An injection nozzle attached to the chamber and injecting a gel into the chamber;
A vacuum pump connected to the chamber and depressurizing the chamber;
A gel injector comprising an ultrasonic generator connected to the chamber and applying ultrasonic vibration to the chamber. Installing a power module having a power semiconductor element inside the chamber;
Reducing the pressure in the chamber and applying ultrasonic vibration to the chamber;
Injecting gel into the power module so as to seal the power semiconductor element by continuing the application of the reduced pressure and the ultrasonic vibration;
A method of manufacturing a power module, comprising: a step of continuing the pressure reduction and application of the ultrasonic vibration for a predetermined time after the gel is injected.

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