JP2007150358A - Process for producing wiring board with solder bump and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board with solder bumps in which a void is not formed easily in the solder bump, and the electrode of an electronic component can be bonded firmly to a solder bonding pad through the solder bump. <P>SOLUTION: In the wiring board with solder bumps comprising an insulating substrate 1 where solder bonding pads 3 are formed on the surface, a solder-resistant resin layer 4 deposited on the surface of the insulating substrate 1 while having openings 4a for exposing the central portion of the solder bonding pads 3 and covering the outer circumferential part of the solder bonding pads 3, and solder bumps 5 bonded onto the solder bonding pads 3 exposed in the openings 4a, the solder bonding pad 3 has a protrusion formed integrally such that the surface to which the solder bump 5 is bonded becomes convex, a via conductor having an area in plan view smaller than that of the convex surface is formed integrally on the surface on the opposite side to the convex surface, and the outer circumferential part of the solder bonding pad 3 is extending to the outside of the protrusion and the via conductor in the plan view. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wiring board with solder bumps for mounting electronic components such as semiconductor elements and resistors, and an electronic device using the wiring board.

  In recent years, a wiring board used for mounting electronic components such as semiconductor elements and resistors is laminated with a plurality of wiring conductor layers made of a glass substrate and a thermosetting resin and copper foil and the like alternately. A printed circuit board formed in this manner, and a build-up board in which a plurality of insulating layers made of a thermosetting resin and filler and a wiring conductor layer made of a copper plating layer are laminated on an insulating plate have been used.

  And on the upper surface of the wiring board such as a printed board or a build-up board, a solder bonding pad for connecting an electrode of an electronic component such as a semiconductor element and a solder-resistant resin that exposes a central portion of the solder bonding pad A layer is deposited, and solder bumps are formed on the solder joint pads exposed from the solder-resistant resin layer for joining the electronic component and the solder joint pads.

  In such a wiring board with solder bumps, the electronic component is placed on the upper surface of the wiring board so that each electrode abuts the corresponding solder bump, and these are heated by, for example, an electric furnace or the like. The electronic component is mounted on the wiring board by heating the device to melt the solder bump and bonding the solder bump and the electrode of the electronic component.

Such a wiring board with solder bumps includes a plurality of substantially circular solder bonding pads connected to the wiring conductors on the surface of the insulating substrate having a plurality of wiring conductors inside and / or on the surface, and the solder bonding pads. A solder-resistant resin layer having an opening that exposes the central portion of the solder is applied, and then a solder paste composed of flux and solder powder is printed and applied onto the solder bonding pad using a conventionally known screen printing method. Is heated to evaporate and remove the flux in the solder paste and melt the solder powder in the solder paste to form solder bumps on the solder joint pads.
JP 2000-125991 A

  However, according to the conventional wiring board with solder bumps, the flux in the solder paste printed and applied on the solder bonding pad is vaporized and removed, and the solder powder in the solder paste is melted to form the solder bump on the solder bonding pad. When soldering, some of the flux contained in the solder paste is left behind in the melted solder and easily generates large voids in the solder bumps, and a large amount of such large voids are generated in the solder bumps. Then, when the electrode of the electronic component and the solder bonding pad are bonded via the solder bump, the bonding between the electrode of the electronic component and the solder bonding pad is obstructed by the void, or the strength of the solder bump becomes weak. There is a problem that it becomes impossible to firmly bond the electrode of the electronic component and the solder bonding pad via the solder bump. Which was.

  The present invention has been devised in view of such conventional problems, and an object of the present invention is to prevent formation of large voids in the solder bumps formed on the solder bonding pads, and the electrodes of the electronic components and the solder bonding pads. It is an object of the present invention to provide a wiring board with solder bumps that can be firmly joined to each other via solder bumps.

  The wiring board with solder bumps of the present invention has an insulating substrate having a solder bonding pad formed on the surface thereof, and is attached to the surface of the insulating substrate, and has an opening that exposes the central portion of the solder bonding pad. A wiring board with solder bumps, comprising: a solder-resistant resin layer covering an outer periphery of the solder bonding pad; and a solder bump bonded onto the solder bonding pad exposed in the opening. The bonding pad is integrally formed with a protruding portion so that the surface to which the solder bump is bonded becomes a convex surface, and has a planar view area smaller than the planar view area of the convex surface on the surface opposite to the convex surface. The solder conductor pad is integrally formed, and the outer periphery of the solder joint pad extends outward from the protrusion and the via conductor in plan view.

  In the wiring board with solder bumps of the present invention, preferably, the height of the convex surface is 1 to 10 μm.

  In the wiring board with solder bumps of the present invention, preferably, the solder joint pad is formed by plating.

  In the wiring board with solder bumps of the present invention, preferably, the insulating substrate contains a resin.

  In the wiring board with solder bumps of the present invention, preferably, the solder bumps are connected to electrodes of electronic components.

  The wiring board with solder bumps of the present invention is preferably characterized in that an angle formed between the convex surface and the outer peripheral surface of the solder joint pad continuous thereto is an obtuse angle.

  The electronic device according to the present invention includes an insulating substrate having a solder bonding pad formed on a surface thereof, an opening that is attached to the surface of the insulating substrate, and exposes a central portion of the solder bonding pad, and the solder bonding. An electronic device comprising a solder-resistant resin layer covering an outer periphery of a pad and an electronic component connected on the solder bump, wherein the solder joint pad has a surface to which the electronic component is connected. The protrusion is integrally formed to be a convex surface, and a via conductor having a planar view area smaller than the planar view area of the convex surface is integrally formed on the surface opposite to the convex surface, Furthermore, the outer peripheral portion of the solder bonding pad extends outward from the protruding portion and the via conductor in plan view.

  According to the present invention, when the solder paste is applied to the solder bonding pad and heated to form a solder bump on the solder bonding pad, the vaporized flux in the solder paste is easily separated from the surface of the solder bonding pad. As a result, it is difficult to form a large void in the solder bump.

  Next, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing an example of an embodiment of a wiring board with solder bumps of the present invention. FIG. 2 is an enlarged sectional view of a main part of the wiring board with solder bumps of the present invention.

  In FIG. 1, 1 is an insulating substrate, 2 is a wiring conductor, 3 is a solder joint pad, 4 is a solder-resistant resin layer, 5 is a solder bump, and 6 is an external lead pin. A substrate is configured. In this example, the external lead pin 6 is shown. However, the external lead pin 6 is not always necessary, and an external connection terminal made of, for example, solder may be provided instead of the external lead pin 6.

  The insulating substrate 1 is made of, for example, epoxy resin or bismaleimide triazine on the upper and lower surfaces of a plate-like core 1a formed by impregnating a glass fabric in which glass fibers are woven vertically and horizontally with a thermosetting resin such as epoxy resin or bismaleimide triazine resin. A plurality of insulating layers 1b made of a thermosetting resin such as a resin are laminated, and a plurality of wiring conductors made of a conductor layer such as a copper foil or a copper plating film are formed on the surface of the core 1a or each insulating layer 1b. 2 is formed.

  The core 1a constituting the insulating substrate 1 has a thickness of about 0.3 to 1.5 mm and has a plurality of through holes 7 having a diameter of about 0.1 to 1.0 mm from the upper surface to the lower surface. . A part of the wiring conductor 2 is attached to the inner wall of each through hole 7, and the wiring conductors 2 formed on the upper and lower surfaces of the core body 1 a are electrically connected to each other through the wiring conductor 2 in the through hole 7. Connected.

  Such a core body 1a is manufactured by thermally curing a sheet in which a glass fabric is impregnated with an uncured thermosetting resin, and then drilling the through hole 7 from the upper surface to the lower surface. . The wiring conductors 2 on the upper and lower surfaces of the core body 1a have copper foil having a thickness of about 3 to 50 μm adhered to the entire upper and lower surfaces of the sheet for the core body 1a, and the copper foil is etched after the sheet is cured. By processing, a predetermined pattern is formed on the upper and lower surfaces of the core body 1a. Further, the wiring conductor 2 in the through hole 7 is a copper plating film having a thickness of about 3 to 50 μm formed on the inner wall of the through hole 7 by electroless plating and electrolytic plating after the through hole 7 is provided in the core 1a. Is deposited on the inner wall of the through hole 7.

  Furthermore, the core body 1a is filled with a resin column 8 made of a thermosetting resin such as an epoxy resin or a bismaleimide triazine resin in the through hole 7 thereof. The resin pillar 8 is for making it possible to form the insulating layer 1b directly above and below the through hole 7 by closing the through hole 7. An uncured paste-like thermosetting resin is placed in the through hole 7. After filling with a screen printing method and thermosetting it, the upper and lower surfaces thereof are polished to be substantially flat. And the insulating layer 1b is laminated | stacked on the upper and lower surfaces of the core 1a containing this resin pillar 8. As shown in FIG.

  The insulating layer 1b laminated on the upper and lower surfaces of the core body 1a has a plurality of through holes 9 each having a thickness of about 20 to 60 μm and a diameter of about 30 to 100 μm from the upper surface to the lower surface of each layer. A part of the wiring conductor 2 is deposited in these through holes 9. These insulating layers 1b are for providing an insulating interval for wiring the wiring conductors 2 with high density. The upper wiring conductor 2 and the lower wiring conductor 2 are electrically connected via the wiring conductor 2 in the through hole 9 so that a high-density wiring can be formed three-dimensionally.

  Such an insulating layer 1b is obtained by sticking an uncured thermosetting resin film having a thickness of about 20 to 60 μm to the upper and lower surfaces of the core body 1a, thermosetting it, and drilling through holes 9 by laser processing. Further, it is formed by sequentially stacking the next insulating layer 1b in the same manner. The wiring conductor 2 deposited on the surface of each insulating layer 1b and in the through hole 9 has a thickness of about 5 to 50 μm on the surface of each insulating layer 1b and in the through hole 9 every time each insulating layer 1b is formed. It is formed by depositing a copper plating film in a predetermined pattern by a pattern forming method such as a known semi-additive method or subtractive method.

  Further, a solder-resistant resin layer 4 is deposited on the outermost insulating layer 1b. The solder-resistant resin layer 4 is made of an insulating material in which an inorganic powder filler such as silica or talc is dispersed in an acrylic-modified epoxy resin, for example, in an amount of 30 to 70% by mass, and improves the electrical insulation reliability between the wiring conductors 2 on the surface layer. At the same time, the bonding strength of the solder bonding pad 3 and the pin bonding pad 10 described later to the insulating substrate 1 is increased.

  Such a solder-resistant resin layer 4 has a thickness of about 10 to 50 μm, and an uncured resin paste for the solder-resistant resin layer 4 having photosensitivity is applied to the outermost layer by employing a roll coater method or a screen printing method. After coating on the insulating layer 1b and drying it, exposure and development processes are performed to form openings 4a and 4b that expose the central portions of the solder bonding pads 3 and the pin bonding pads 10, and then this is heated. It is formed by curing. Alternatively, after an uncured resin film for the solder-resistant resin layer 4 is stuck on the uppermost insulating layer 1b, it is thermally cured, and then the position corresponding to the solder bonding pad 3 or the pin bonding pad 10 Are formed so as to have openings 4a and 4b exposing the solder bonding pad 3 and the pin bonding pad 10 by partially removing the cured resin film.

  The wiring conductor 2 formed from the upper surface to the lower surface of the insulating substrate 1 functions as a conductive path for connecting each electrode of the electronic component to the external electric circuit substrate, and is provided in a mounting region on the upper surface of the insulating substrate 1. A part of the exposed part of the solder bonding pad 3 is bonded to each electrode of the electronic component via a solder bump 5 made of, for example, a lead-tin alloy, and a part of the part exposed on the lower surface of the insulating substrate 1 is an external electric circuit. A pin bonding pad 10 for bonding external lead pins 6 connected to the substrate is formed.

  Such solder joint pads 3 and pin joint pads 10 are formed by covering the outer periphery of a substantially circular pattern made of a conductor layer connected to the wiring conductor 2 with a solder-resistant resin layer 4 with a width of about 15 to 35 μm. By defining the outer periphery, the diameter of the solder bonding pad 3 is about 70 to 200 μm, and the pin bonding pad 10 is about 0.5 to 2.5 mm.

  In addition, by covering the outer periphery of the solder bonding pad 3 and the pin bonding pad 10 with the solder-resistant resin layer 4 in this way, an electrical short circuit between the solder bonding pads 3 and the pin bonding pads 10 is effectively prevented. In addition, the bonding strength of the solder bonding pad 3 and the pin bonding pad 10 to the insulating substrate 1 is high.

  Normally, the exposed surfaces of the solder bonding pad 3 and the pin bonding pad 10 are excellent in preventing the oxidative corrosion of the solder bonding pad 3 and the pin bonding pad 10 and connecting the solder bumps 5 and the external lead pins 6 to each other. Therefore, it is preferable to deposit a metal having good conductivity and corrosion resistance, such as nickel and gold, to a thickness of 1 to 20 μm by plating.

  Solder bumps 5 are bonded to the solder bonding pads 3. The solder bump 5 is made of a solder material such as a lead-tin alloy and functions as a terminal for electrically and mechanically connecting the solder bonding pad 3 and the electronic component, and each electrode of the electronic component corresponds to a corresponding solder. The electronic components are placed so as to be in contact with the bumps 5 and are heated by a heating device such as an electric furnace to melt the solder bumps 5 so that the solder bumps 5 and the electrodes of the electronic components are connected. .

  In order to join the solder bumps 5 to the solder joint pads 3, after applying and applying a solder paste onto the solder joint pads 3 by using a conventionally known screen printing method, the solder paste is heated to be contained in the solder paste. A method of vaporizing and removing the flux and melting the solder in the solder paste is employed.

  In the wiring board with solder bumps of the present invention, as shown in the enlarged sectional view of the main part in FIG. 2, the surface of the solder bonding pad 3 to which the solder bumps 5 are bonded is a convex surface. is important. Thus, since the surface where the solder bump 5 of the solder bonding pad 3 is bonded is a convex surface, the solder paste is printed on the solder bonding pad 3 and the solder paste is heated to solder bump 5. When the solder is bonded, the vaporized flux in the solder paste is easily separated from the surface of the solder bonding pad 3, and as a result, it is effectively prevented that a large amount of large voids are generated in the solder bump 5.

  In order to make the surface to which the solder bumps 5 of the solder bonding pad 3 are bonded convex, for example, when forming the solder bonding pad 3, a plating solution in which a large amount of the plating solution hits the central portion of the solder bonding pad 3 is used. The thickness of the copper plating film at the center portion of the solder bonding pad 3 may be increased by performing the above-described flow for plating.

  When the height of the convex surface to which the solder bump 5 of the solder bonding pad 3 is bonded is less than 1 μm, the solder paste 5 is printed and applied to the solder bonding pad 3 and the solder paste 5 is heated to form the solder bump 5. In addition, the vaporized flux in the solder paste is less likely to be separated from the solder bonding pad 3, and as a result, a large void tends to be generated in the solder bump 3. On the other hand, if the solder paste exceeds 10 μm, the solder-resistant resin 4 Resin residue of the solder-resistant resin layer 4 is likely to be generated on the outer peripheral portion of the solder bonding pad 3 exposed in the opening 4a, and when such a residue is generated, the solder bump 5 is firmly attached on the solder bonding pad 3. It becomes difficult to join. Therefore, the height of the convex surface to which the solder bump 5 of the solder bonding pad 3 is bonded is preferably in the range of 1 to 10 μm.

  In addition, external lead pins 6 made of a metal such as copper or iron-nickel-cobalt alloy are bonded to the pin bonding pads 10 via solder having a melting point higher than that of the solder bumps 5. The external lead pin 6 functions as a terminal member for electrically connecting an electronic component mounted on the wiring board to the external electric circuit board. The external lead pin 6 is connected to the wiring conductor of the external electric circuit board via solder or a socket. By connecting, the electronic component is electrically connected to the external electric circuit.

  Thus, according to the wiring substrate with solder bumps of the present invention, the electronic component is placed on the upper surface of the wiring substrate 1 so that the electrode contacts the solder bump 5, and the solder bump 5 is melted to form the electrode of the electronic component. By bonding the solder bonding pad 3 to the solder bonding pad 3, the electronic device of the present invention as a product is obtained.

  In addition, this invention is not limited to an example of the above-mentioned embodiment, It cannot be overemphasized that a various change is possible if it is a range which does not deviate from the summary of this invention.

It is sectional drawing which shows an example of embodiment of the wiring board with a solder bump of this invention. It is a principal part expanded sectional view of the wiring board with a solder bump shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Insulation board | substrate 2 ... Wiring conductor 3 ... Solder joint pad 4 ... Solder-resistant resin layer 4a ... Opening part 5 of solder-resistant resin layer ... ..Solder bumps

Claims (7)

An insulating substrate having a solder bonding pad formed on the surface, and an insulating substrate that is attached to the surface of the insulating substrate, has an opening that exposes the central portion of the solder bonding pad, and covers the outer periphery of the solder bonding pad A wiring board with solder bumps comprising a solder-resistant resin layer and solder bumps bonded onto the solder bonding pads exposed in the openings, wherein the solder bonding pads are bonded to the solder bumps. And a via conductor having a planar view area smaller than the planar view area of the convex surface is integrally formed on the surface opposite to the convex surface. And a solder bump-equipped wiring board, wherein an outer peripheral portion of the solder bonding pad extends outwardly from the protruding portion and the via conductor in plan view. The wiring board with solder bumps according to claim 1, wherein the height of the convex surface is 1 to 10 μm. 3. The wiring board with solder bumps according to claim 1, wherein the solder bonding pads are formed by plating. The wiring board with solder bumps according to any one of claims 1 to 3, wherein the insulating substrate contains a resin. The wiring board with solder bumps according to any one of claims 1 to 4, wherein an electrode of an electronic component is connected to the solder bumps. 6. The wiring board with solder bumps according to claim 1, wherein an angle formed between the convex surface and the outer peripheral surface of the solder joint pad continuous thereto is an obtuse angle. An insulating substrate having a solder bonding pad formed on the surface, and an insulating substrate that is attached to the surface of the insulating substrate, has an opening that exposes the central portion of the solder bonding pad, and covers the outer periphery of the solder bonding pad An electronic device comprising a solder-resistant resin layer and an electronic component connected on the solder bump, wherein the solder joint pad has a protruding portion so that a surface to which the electronic component is connected is a convex surface Are formed integrally, and a via conductor having a planar view area smaller than the planar view area of the convex surface is integrally formed on the surface opposite to the convex surface, and the outer periphery of the solder joint pad An electronic device characterized in that a portion extends outside the projecting portion and the via conductor in plan view.

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