JP2009141172A - Electronic device and method of manufacturing substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic device in which heat dissipation of electronic components is enhanced by improving heat conductivity of an intervening agent, and to provide a method of manufacturing a substrate. <P>SOLUTION: In the electronic device 100 having a substrate 12 stuck on a metal plate 14 through the intervening agent 13 such as an adhesive and grease, the substrate 12 has: a pad portion 15b of an inner layer electrode 15 exposed to the side of the electronic component 11; and a pad portion 15a exposed to the side of the metal plate 14, the pad portion 15a being a thickness-regulating member for regulating the thickness of the intervening agent 13. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electronic device or the like in which a substrate is bonded to a metal plate, and more particularly, to an electronic device and a method for manufacturing the substrate that define the thickness of an intervening agent that interposes the substrate and the metal plate.

  Electronic components, particularly power semiconductors such as power MOSs and IGBTs (Insulated Gate Bipolar Transistors), generate a large amount of heat and often have a structure in which heat is radiated through a substrate 102 on which the electronic components are fixed. FIG. 6 shows an example of a conventional heat dissipation structure for an electronic component. The heat generated by the electronic component 101 fixed to the substrate 102 is transferred to the metal plate 104 via an adhesive or grease (hereinafter referred to as an intervening agent) 103, thereby efficiently radiating heat from the metal plate having high thermal conductivity. I am trying to do that. However, it is known that the thermal conductivity of the intercalating agent 103 is smaller than that of the metal plate 104 and the heat dissipation is reduced. For example, the thermal conductivity of the intercalating agent 103 is several W / mk, whereas the thermal conductivity of the metal plate 104 is 100 to 200 W / mk (about 200 W / mk in the case of aluminum). For this reason, in order to efficiently dissipate heat, it is required to make the intercalating agent 103 as thin as possible. However, the thickness d of the conventional intervening agent 103 is 120 μm ± 40 μm, which is a relatively large thickness.

By the way, when assembling an electronic device, in the step of mounting the substrate 102 on the metal plate 104, for example, the substrate 102 is placed on the adhesive applied in a film shape on the metal plate 104 and the adhesive is cured, thereby the substrate. A fixing method for fixing 102 on a metal plate 104 is known (for example, see Patent Documents 1 and 2). In Patent Document 1, a spacer is sandwiched between the electronic component 101 (corresponding to the substrate 102) and the substrate 102 (corresponding to the metal plate 104), and the thickness of the adhesive under the electronic component is determined by the thickness of the spacer. The specified fixing method is described. In Patent Document 2, a bump electrode is provided on the substrate 102 (corresponding to the metal plate 104) side of the electronic component 101 (corresponding to the substrate 102), and the electronic component 101 and the substrate 102 are in a state where the bump electrode and the substrate are electrically connected. A fixing method is described in which the adhesive is cured.
JP 2006-23250 A JP-A-2005-252135

  However, when the thickness of the mediator 103 is defined by narrowing the spacer as in the fixing method of Patent Document 1, it is difficult to prepare a sufficiently thin spacer, and the thickness is controlled with high accuracy. If a prepared spacer is prepared, the cost may increase. Further, if the spacer thickness is not uniform, the thickness of the intercalating agent 103 will also be non-uniform. Further, when electrode bumps are provided as in the fixing method of Patent Document 2, it is difficult to form extremely low electrode bumps or make the height between the electrode bumps uniform, and the thickness of the intercalation agent 103 It is difficult to make the thickness as thin as possible.

  An object of this invention is to provide the manufacturing method of an electronic device and a board | substrate which improved the heat conductivity of the intervention agent and was excellent in the heat dissipation of an electronic component in view of the said subject.

  In view of the above problems, the present invention provides an electronic device in which a substrate is bonded to a metal plate via an intervening agent, and the substrate has a thickness defining member that defines the thickness of the intercalating agent on the metal plate side. It is characterized by that.

  According to the present invention, since the thickness of the intervention agent can be regulated by the thickness regulating member, the heat transfer property of the intervention agent can be improved.

  In one embodiment of the present invention, the thickness defining member is a film formed by a plating process.

  According to the present invention, since the thickness defining member is formed by plating, the thickness defining member can be formed thin and with high accuracy.

  In one embodiment of the present invention, the thickness defining member is electrically connected to a conductive material penetrating the substrate from the surface on the metal plate side to the opposite surface and exposed on the opposite surface. .

  According to the present invention, since the thickness defining member is electrically connected to the conductive material penetrating the substrate, the interposition agent is checked by checking the conductivity between the conductive material exposed on the opposite surface of the substrate and the metal plate. It can be inspected whether or not the substrate can be fixed to the metal plate so that the thickness of the substrate becomes the thickness of the thickness defining member.

  It is possible to provide a method for manufacturing an electronic device and a substrate that improve the heat conductivity of the intercalating agent and have excellent heat dissipation of the electronic component.

The best mode for carrying out the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic cross-sectional view of an electronic device 100 including the heat dissipation structure of this embodiment. In the electronic device 100, a metal plate 14 for heat dissipation and a substrate 12 on which the electronic component 11 is mounted are fixed via an intercalating agent 13. The thickness d of the intercalating agent 13 is defined by the pad thickness d ′ of the pad portion 15 a of the inner layer electrode 15. Since the pad portion 15a is formed by plating, the pad portion 15a can be formed by controlling the pad thickness d 'to a minimum of several microns.

  Therefore, since the thickness of the intercalating agent 13 having a low thermal conductivity can be reduced to 1/10 or less compared with the case where it is simply applied in the form of a film or the like, the heat generated by the electronic component 11 can be reduced to a metal plate. The heat can be easily radiated from 14.

  Further, the pad portion 15b exposed to the electronic component 11 side of the inner layer electrode 15 (hereinafter, the electronic component 11 side is referred to as the front surface and the opposite side is referred to as the rear surface) and the pad portion 15a are electrically connected by the inner layer through hole 15c. By checking the conduction between the metal plate 14 and the pad portion 15b, it is possible to inspect whether or not the substrate 12 can be fixed to the metal plate 14 with the pad thickness d ′ of the pad portion 15a.

  FIG. 2 shows an example of a manufacturing process of the electronic device 100. First, the inner layer electrode 15 is formed on the substrate 12. The substrate 12 in FIG. 2A is formed of a general material used for a printed circuit board or the like, for example, glass epoxy resin, ceramic (alumina), paper phenol, glass composite, Teflon (registered trademark), or the like. In consideration of thermal conductivity, for example, ceramic (18 W / mk) is preferable to glass epoxy (0.1 W / mk).

  The inner layer electrode 15 is formed by passing a conductive material through a through-hole penetrating from the front surface to the back surface of the substrate 12 and depositing a metal with a controlled pad thickness d ′ on at least the back surface of the substrate 12 (FIG. 2B). ). A plating process is applied to form the pad portion 15a, which will be described later in detail.

  Next, the electronic component 11 is mounted at a predetermined position on the substrate 12 (FIG. 2C). The electronic component 11 is, for example, a power semiconductor such as a power MOS or IGBT that generates a large amount of heat, a microprocessor, a light emitting element, or the like, but any electronic component 11 may be mounted. The electronic component 11 is mounted on the substrate 12 by curing, for example, solder, conductive paste, or underfill.

  Next, an adhesive or grease or the like is applied to a predetermined portion of the metal plate 14 in a film shape so that the adhesive or grease does not contact the contact surface where the pad portion 15a and the metal plate 14 abut, and the substrate 12 is Pressure is applied in the direction of the metal plate 14. Due to the pressurization of the substrate 12, the interstitial agent 13 (adhesive or grease, etc.) flows until the thickness d of the interstitial agent 13 reaches the pad thickness d ′. Therefore, the thickness d of the intercalating agent 13 is defined by the pad thickness d 'of the pad portion 15a, and good heat transfer is realized by the thinness. The intervening agent 13 is, for example, an adhesive that is cured by the action of heat, time, light, or silicon grease having excellent heat dissipation, and the intervening agent 13 flows to a sufficiently thin thickness d. In view of the above, it is preferable that the material has a low viscosity.

  The metal plate 14 is formed by forming a metal material such as aluminum or copper having a high thermal conductivity into a plate shape, and has a function as a heat sink that dissipates heat generated by the electronic component 11 to the outside. Yes. Note that a flow path such as cooling water may be formed in the metal plate 14, or a plurality of metal plates may be laminated.

  The formation process of the inner layer electrode 15 is demonstrated based on FIG. First, the through hole 21 is formed in the substrate 12 (FIG. 3A). The through hole 21 can be formed by, for example, a laser or a drill. The diameter of the through hole 21 is, for example, several tens to several hundreds μm, or about several hundreds μm to several meters, but the size of the diameter can be designed as appropriate. As the laser, for example, a carbon dioxide laser (CO2), excimer laser, or YAG laser is used, and as the drill, for example, a drill having a diamond tip attached to the tip is used.

  Next, the formed through hole 21 is filled with a conductive paste 22 by screen printing or the like. The conductive paste 22 is cured by, for example, heating or light irradiation, and then polished so as to eliminate the protruding portions of the conductive paste 22 on the front surface and the back surface of the substrate 12 to flatten the surface of the substrate 12 (FIG. 3B). .

  Next, the substrate 12 is subjected to electroless plating. A compound that dissolves in a solvent containing metal (for example, water) and a reducing agent are dissolved in a plating solution, and the substrate 12 is infiltrated into the plating solution to deposit a metal on the surface of the substrate 12 (FIG. 3C). If necessary, the substrate 12 is subjected to a pretreatment (a treatment that activates after cleaning the surface of the substrate 12 so that metal is easily deposited). The metal to be dissolved is, for example, copper or nickel. In addition, after electroless plating, the thickness may be increased by electrolytic plating.

  In this plating process, the pad thickness d 'is controlled. The plating thickness formed by electroless plating is controlled by the time during which the substrate 12 is infiltrated into the plating solution if the temperature of the plating solution, the metal concentration, the stirring speed of the solution, etc. are constant. The plating thickness can be controlled with an accuracy of about ± 10%, and can be formed with a plating thickness of about several to 10 μm, for example.

  The pad thickness d ′ of this embodiment is set according to the processing accuracy of the substrate 12 and the metal plate 14. That is, the setting is made so that the substrate 12 and the metal plate 14 are not in direct contact and the contact surface of the pad portion 15 a is not separated from the metal plate 14. The pad thickness d ′ is, for example, preferably about 10 μm to 100 μm, more preferably about 10 μm to 50 μm, and further preferably 10 μm to 30 μm.

  Since the pad portion 15b on the surface of the substrate 12 is only used for continuity check, the thickness may not be controlled as long as it is exposed on the surface of the substrate 12.

Next, a photoresist 24 is patterned on the surface of the metal film 23 (FIG. 3D).
Photoresist 24 is applied to metal film 23, exposure is performed through a photomask having a light-shielding pattern, and development and hardening are performed. The pattern shape of the photomask is, for example, a shape in which a circle slightly larger than the through hole 21 is opened at the same position as the through hole 21. Note that the photoresist 24 is a water-soluble one in which, for example, casein or polyvinyl alcohol and ammonium dichromate are mixed.

  Next, etching is performed using the photoresist 24 as an etching mask (FIG. 3E). When the metal film 23 is made of copper, the etching solution is iron chloride or a mixed solution of copper chloride and water.

  Finally, the photoresist 24 on the through hole 21 is removed to expose the metal film 23 (FIG. 3F). For example, the photoresist 24 is removed by dipping in an acidic aqueous solution or an alkaline aqueous solution (sodium hydroxide / potassium hydroxide).

  With the above processing, the inner layer electrode 15 can be formed on the substrate 12. Since the pad thickness d 'of the pad portion 15a can be controlled by the plating process, the thickness d of the intercalating agent 13 can be made smaller than when the thickness d of the intervening agent 13 is controlled by a separate spacer or the like. Accordingly, the heat generated by the electronic component 11 can be easily radiated from the metal plate 14. Further, since the inner layer electrode 15 makes the metal plate 14 and the pad portion 15b conductive, it is checked whether or not the metal plate 14 and the pad portion 15b are conductive, thereby making the substrate 12 to the metal plate 14 with the pad thickness d ′. It can be inspected whether or not it has been fixed.

  Note that, from the state of FIG. 2B, a metal film may be formed by sputtering or vapor deposition, for example. In this case, the inner layer electrode 15 equivalent to that shown in FIG. 5F can be formed by masking portions other than the through holes 21 before film formation and removing the mask after film formation.

  Another example of the formation process of the inner layer electrode 15 will be described with reference to FIG. Details of the same steps as those in FIG. 3 are omitted.

  First, the through hole 21 is formed in the substrate 12 (FIG. 4A). Next, electroless plating is applied to the substrate 12 (FIG. 4B). Thereby, a metal film 23 covering the substrate 12 is formed. Although the plating solution enters the through hole 21, the metal film 23 thinner than the surface of the substrate 12 is formed because the inside of the through hole 21 has little contact with the plating solution. To avoid disconnection, the diameter of the through hole 21 may be increased. More preferably, the metal film 23 may block the through hole 21.

  Next, a photoresist 24 is patterned on the surface of the metal film 23 (FIG. 4C). The pattern shape of the photoresist 24 is, for example, a concentric circle slightly larger than the through hole 21. Thereby, the metal film 23 can be masked by the photoresist 24 from the electronic component 11 side to the through hole 21 and the metal plate 14 side. The through hole 21 may be filled before patterning the photoresist 24.

  Next, etching is performed using the photoresist 24 as an etching mask (FIG. 4D), and finally the photoresist 24 is removed to expose the metal film 23 (FIG. 4E). That is, since it is sufficient that the front surface and the back surface of the substrate 12 can be conducted, the through hole 21 may not be blocked by the conducting material.

  With the above processing, the inner layer electrode 15 can be formed on the substrate 12. In the process as shown in FIG. 4, it is not necessary to fill the conductive paste 22, so an increase in cost can be suppressed.

  FIG. 5 is a diagram illustrating an arrangement example of the inner layer electrode 15. FIG. 5A is an example of a plan view of the substrate 12 and the inner layer electrode 15. In FIG. 5A, four inner layer electrodes 15 are formed on the substrate 12, and are arranged in line symmetry with respect to the center line of the substrate 12 or point symmetry with respect to the center. By arranging the inner layer electrodes 15 in line symmetry or point symmetry, the possibility of the substrate 12 tilting when pressing the metal plate 14 to fix the substrate 12 can be reduced. Four or more inner layer electrodes 15 may be arranged randomly (randomly). The number of inner layer electrodes 15 may be five or more, and the number is preferably increased or decreased according to the ratio of the area of the substrate 12 to the area of the pad portion 15a, the rigidity (easiness of deflection) of the substrate 12, and the like. .

  FIG. 5B shows another example of a plan view of the substrate 12 and the inner layer electrode 15. In FIG. 5B, the inner layer electrode 15 is formed in a rectangular shape. Since the contact area with the metal plate 14 can be increased by using a rectangular shape, the substrate 12 and the inner layer electrode 15 can be stably brought into contact with each other when the metal plate 14 is pressed and fixed. Three or more rectangular inner layer electrodes 15 may be formed, or may be arranged such that the longitudinal directions form a predetermined angle (for example, 90 degrees) instead of being arranged so that the longitudinal directions are parallel to each other. In FIG. 5B, the inner layer electrode 15 is formed so that the longitudinal direction of the inner layer electrode 15 is parallel to the side of the substrate 12, but an angle may be provided between the side of the substrate 12 and the longitudinal direction of the inner layer electrode 15. Good. Further, the inner layer electrode 15 shown in FIGS. 5A and 5B may be mixed in one substrate 12.

  In the substrate structure of this embodiment, the pad portion 15a can be formed by controlling the pad thickness d 'below a predetermined value and with high precision in the plating step, so that the adhesive or grease intercalating agent 13 is made thin. Thus, the heat dissipation of the electronic component 11 can be improved. Even if the intercalating agent 13 is made thin, the continuity check can be performed by the pad portion 15b of the inner layer electrode 15 and the metal plate 14, so that it can be easily inspected that it is fixed with the pad thickness d '.

  Moreover, in this embodiment, although the process which fixes the board | substrate 12 to the metal plate 14 was made into an example, you may apply when fixing the electronic component 11 to the board | substrate 12. FIG.

It is a schematic sectional drawing of an electronic device. It is a figure which shows an example of the manufacturing process of an electronic device. It is a figure which shows an example of the formation process of an inner layer electrode. It is a figure which shows an example of the formation process of an inner layer electrode. It is a figure which shows the example of arrangement | positioning of an inner layer electrode. It is a figure which shows an example of the heat dissipation structure of the conventional electronic component.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Electronic component 12 Board | substrate 13 Interposition agent 14 Metal plate 15 Inner layer electrode 15a, 15b Pad part 21 Through hole 23 Metal film 100 Electronic device

Claims (4)

In an electronic device in which a substrate is bonded to a metal plate via an intervening agent,
The substrate has a thickness defining member that defines the thickness of the interposition agent on the metal plate side.
An electronic device characterized by that.   The electronic device according to claim 1, wherein the thickness defining member is a metal film formed by plating. The thickness defining member is electrically connected to a conductive material penetrating the substrate from the surface on the metal plate side to the surface on the opposite side and exposed on the surface on the opposite side,
The electronic device according to claim 2. In the method of manufacturing a substrate that is bonded to a metal plate via a heat transfer material,
Filling a conductive material into a through hole penetrating from the surface on the metal plate side to the surface on the opposite side;
Forming a thickness defining member defining the thickness of the heat transfer material on the conductive material exposed on the surface of the metal plate;
A method for manufacturing a substrate, comprising:

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