JP2943788B2 - Wiring board for mounting electronic components - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board for mounting electronic components, and more particularly to a wiring board for mounting electronic components having electrode pads for forming bumps.

[0002]

2. Description of the Related Art A conventional technique will be described with reference to FIG.
The conventional wiring board 31 for mounting the electronic parts of the prior art is formed by reflow soldering an electronic component 40 such as a semiconductor circuit component, a resistor, a capacitor or a module component on the upper surface of the conventional wiring board 31 to have a surface. Implement or
Alternatively, the electronic component 40 is connected to the bonding lands of the upper outer layer conductor 33 on the electronic component mounting surface by bonding wires 41 and mounted by wire bonding. The upper surface outer layer conductor 33 on the electronic component mounting surface and the lower surface outer layer conductor 35 on the bump formation side are electrically connected by the through-hole plating layer 34 of the through-hole 32. A large number of planar electrode pads 36 are set and arranged at predetermined two-dimensional grid intersections of the lower surface outer layer conductor 35. A protruding contact (hereinafter, referred to as a bump) is formed on the surface of the planar electrode pad 36 which is a terminal for connecting to the outside of the conventional wiring board 31 on which the electronic component 40 is mounted. As a typical bump 45, a spherical solder ball 45A is generally used, but in addition, a bump 45 having an egg shape, a hemispherical shape, an elliptical spherical shape, or the like is also used. When the bump 45 is attached to the planar electrode pad 36, positioning is very difficult because the tip surface of the bump 45 in contact with the electrode pad 36 has a spherical shape.

Conventionally, connection terminals to the outside of a conventional wiring board 31 on which a so-called electronic component 40 is mounted, such as a high-density electronic component such as an IC flat package and a module wiring board on which the electronic component is mounted, and a parent wiring board ( Reflow soldering using a conductive paste, for example, cream solder 28, has been used to connect the mother board 22 to the connection lands 26. In recent years, however, the density and size of IC flat packages and the like have been reduced. As a result, the number of connection terminals increases, so-called terminal pitch interval between the connection terminals becomes narrower, the lead terminal diameter of the electronic component 40 becomes thinner and easily deformed, and the limit of the conventional soldering technology is faced. Was higher.

[0004] As a connection technology that has attracted attention,
A plurality of planar electrode pads 36 as terminals for external connection to the lower surface of the conventional wiring board 31 on which the electronic component 40 is mounted, spherical bumps formed by solder or the like,
For example, the solder balls 45A are two-dimensionally arranged, and the bumps of the solder balls 45A and the parent wiring board 22 are arranged.
In many cases, a flat surface mounting is performed by reflow soldering after abutting a connection terminal group coated with a cream solder 28 on the connection land 26.
The method of arranging spherical bumps in two dimensions is BGA (ball
It is called a “grid / array” package system, and it is expected that the quality of electronic components will be improved by increasing the density and miniaturizing them, and by reducing the defective soldering rate.

[0005] Usually, when mounting a high-density and miniaturized electronic component 40 such as an IC flat package on a conventional wiring board 31, a flux or solder for soldering is applied through-hole plating. In order to prevent the mold resin from flowing to the mounting surface of the electronic component 40 through the hole 32 and to prevent the molded resin from flowing to the bump formation side when the mounted electronic component 40 and the bonding wires 41 are covered with the mold resin and protected. Filling material 3 in through hole 32
9 must be filled. After that, it is common to apply a solder resist 17 to portions other than necessary connection lands and electrode pads 36 on the outer conductor surface.

[0006]

However, the conventional B
In the case of mounting a spherical bump 45 on an electrode pad 36 which is set two-dimensionally at an intersection on a two-dimensional grid in the integrated electronic component mounting wiring board of the GA package system, the tip of the bump 45 in contact with the electrode pad 36 Positioning is very difficult because the surface is spherical. Further, the spherical bumps 45 are formed on the planar electrode pads 36 two-dimensionally arranged at predetermined positions on the conventional wiring board 31.
In addition to the need for accurate positioning and fixing, the reflow soldering to the connection lands 26 of the parent wiring board 22 depends on the height of the bumps 45 and the amount of solder forming the bumps. When attaching, adjacent bump 45
Alternatively, the connection land 26 may be short-circuited or the bump 45 formed on the conventional wiring board 31 may be connected to the connection land 2.
In connection technology with the solder paste 28 of No. 6 or the connection technology by planar surface connection using the spherical bump 45, securing the connection reliability is an issue. When the electronic component 40 is mounted on the conventional wiring board 31, the flux and solder for soldering flow out to the mounting surface of the electronic component 40 through the through hole 32, and the mounted electronic component 40 and the bonding wire 41 are removed. In order to prevent the mold resin from flowing out to the side where the bumps 45 are formed when covering and protecting with the mold resin, it is necessary to fill the through hole 32 with the filling material 39, which reduces the production efficiency.

[0007]

According to the present invention, there is provided a wiring board for mounting electronic parts, wherein the wiring board has bumps formed on terminals to be connected to the outside.
An upper surface outer layer conductor that closes one end surface of a hole penetrating the insulating base material, a lower surface outer layer conductor provided in contact with a part or the entire circumference of the other open hole end surface; In a wiring board having a non-through conductive hole provided with a closed outer layer and a conductive layer in a closed non-through hole for electrically connecting outer surface conductors on both surfaces of the lower surface outer layer conductor and the lower surface outer layer conductor, An electronic component is connected to the outer surface conductor by wire bonding, and a concave electrode pad for external connection for mounting a spherical bump in the non-through conductive hole is used as an electronic component mounting wiring board.

[0008] The electronic component is connected to a closed upper surface outer layer conductor on a non-through conductive hole for electrically connecting the outer surface conductors on both surfaces of the upper surface outer layer conductor and the lower surface outer layer conductor of the insulating substrate. A wiring board for mounting electronic components, which forms a bonding land for bonding connection.

In both the double-sided wiring board and the multilayer wiring board, a conductor layer is formed in a closed non-through hole by a plating method or a vapor deposition method, and the upper surface outer layer conductor on the electronic component mounting surface and the bump forming side are formed. And the lower surface outer layer conductor is electrically conductive with the conductor layer in the non-through hole to form a non-through conductive hole,
The inside of the non-through conduction hole is used as an electrode pad for forming a bump. That is, by forming the center of the surface of the wiring substrate from the lower surface to the inside of the insulating base material in a concave shape, and fitting the spherical bump into the concave electrode pad, the correct electrode pad position is obtained. Can be easily positioned. In addition, since the concave electrode pad portion has one end face closed with an outer layer conductor on the upper surface of the electronic component mounting surface, it is possible to omit the filling of the conventional through-hole hole with the filling material. Become.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. First, in the cross-sectional view of the wiring board in the electronic component mounted state of the present invention in FIG.
A bump is formed at a predetermined position on an insulating substrate 1 such as a phenolic substrate, a synthetic resin substrate, a Teflon-containing substrate, a polyimide resin substrate, a BT resin (bismaleimide-triazine resin) substrate, a modified BT resin substrate, or a ceramic. Laser processing is performed from the side to be formed, and a hole 7 penetrating the insulating base material 1 reaching the upper surface outer layer conductor 3 on the electronic component mounting surface is provided. Next, plating is applied to the conductor layer 4 in the non-through hole, the upper surface outer layer conductor 3 on a predetermined electronic component mounting surface at a predetermined location on both surfaces of the insulating substrate 1, and the lower surface on the bump formation side. The outer layer conductor 5 is formed by a printing method or a photographic method, and the outer layer conductors on both sides of the upper surface outer layer conductor 3 on the electronic component mounting surface and the lower surface outer layer conductor 5 on the bump forming side are conventionally formed by the conductor layer 4 in the non-through hole. A non-through conductive hole for electrically connecting the outer layer conductors on both sides is formed in the same manner as the through through hole. The non-through conduction hole formed as described above is a non-through conduction hole in which the center of the surface is dented from the substrate surface 5A on the bump formation side under the wiring substrate 10 to the inside of the insulating base material 1. A concave electrode pad 6 serving as a hole is formed by being depressed to form a concave electrode pad for external connection to which a three-dimensional (three-dimensional) spherical bump 45 is attached.

Next, a soldering flux or a conductive paste 8 is applied or filled into the concave electrode pads 6 formed on the wiring board 10, and spherical bumps 45 are fitted therein. And temporarily fix it. Examples of the conductive paste 8 include a silver paste, a copper paste, a solder paste, a carbon paste, a silver-copper mixed paste, a Sn-Ag-Cu-based paste, and a Sn-Ag-Bi-based paste. Solder is used. In addition, as a material of the bump 45, gold, copper, brass, soft copper, solder, a steel ball plated with metal, a resin plated with metal, or the like is used.

Further, a hole formed in the lower surface of the wiring board as a concave electrode pad 6 formed on the lower surface outer layer conductor 5 on the bump forming side which is a terminal for connection to the outside of the wiring board 10. A surface outer layer conductor is provided in contact with a part or the entire circumference of the end face. However, when a high-density pattern is designed, the lower surface outer layer conductor 5 on the bump formation side is not provided with a land for bump formation, and the conductor in the non-through hole is provided only on the inner wall of the concave non-through hole. A so-called landless shape in which the layer 4 is formed can also be used.

On the upper surface of the wiring board 10, an electronic component 40 such as a resistor, a capacitor, a semiconductor circuit component, an IC flat package or a module component is bonded to a bonding land at a predetermined position on the upper surface outer layer conductor 3 on the electronic component mounting surface. -Wire bonding connection is performed via the wire 41. In particular, the upper surface outer layer conductor 3 closed on the non-through conduction hole for electrically connecting the outer surface conductors 3 on both surfaces of the upper surface outer layer conductor 3 and the lower surface outer layer conductor 5 of the insulating base material 1 to the electronic component. By using the bonding lands for wire bonding connection, the density of the wiring board for mounting electronic components can be further increased. The connection between the electrode terminals of the electronic component 40 and the bonding lands, which are connection lands formed at predetermined locations on the wiring board 10, is not limited to wire bonding, but can be achieved by cream solder, which is a conductive paste 8. Mounting with a surface or welding mounting may be used.

In a wiring board 10 for forming a bump on a terminal connected to the outside of a wiring board for mounting an electronic component, an insulating base 1, a hole 7 penetrating the insulating base, and an insulating base A concave electrode pad 6 which is a non-through conductive hole composed of the upper surface outer layer conductor 3 of the electronic component mounting surface that closes one end face of the through hole 7 and the conductor layer 4 in the closed non-through hole. And a wiring board for mounting electronic components. In addition, when the electronic component 40 is mounted on the wiring board 10, when the electronic component 40 is mounted on the wiring substrate 10, flux or solder flows out to the mounting surface of the electronic component 40 through the through hole. Also, when the mounted electronic components 40 and the bonding wires 41 are covered with the mold resin and protected, the mold resin is prevented from flowing out to the bump 45 forming side.

In the electrode pad for forming the bump 45 according to the present invention, the central portion of the surface is depressed in a concave shape, so that the spherical bump 45 (solder ball 45A) can be easily fitted into the inside thereof. In addition, since the concave electrode pad 6 is set at the correct electrode pad position at the two-dimensional grid intersection, it can be easily positioned. further,
The inner diameter of the non-through hole of the concave electrode pad 6 is slightly larger than the outer diameter D of the spherical bump 45 to be inserted (0.05 to 0.20).
mm), the gap between the inner diameter of the concave electrode pad 6 and the outer diameter D of the bump 45 can be reduced, and the planar positioning accuracy can be increased.

Next, a state in which the spherical bump 45 according to the present invention is recessed will be described with reference to FIG. The conductive paste 8 is provided inside the concave electrode pads 6 of the wiring board 10.
After applying, for example, a spherical solder ball 45A is fitted as the spherical bump 45 and temporarily fixed, and then the ball is placed on a flat jig 47 whose surface is formed of a non-metallic coating such as Teflon, ceramic, or glass. Shaped solder ball 4
The height of the protruding tip surfaces of a large number of two-dimensionally arranged solder balls 45A two-dimensionally arranged by heat treatment such as reflow soldering is set so that the tip surfaces of 5A are set to a uniform level. Become. Also, a pedestal 48 is provided on the jig 47 to make the height H from the substrate surface 5A on the bump formation side of the wiring substrate 10 to the tip end surface of the bump uniform, and a predetermined portion of the wiring substrate 10 is held and heat treatment is performed. Do.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As an embodiment of the present invention, a wiring board 10 will be described.
Is a BT resin base material with a plate thickness of 0.2 mm, and a concave electrode pad 6 that can be arranged in a two-dimensional matrix at a BGA terminal pitch of 1.0 mm is perforated with a short pulse carbon dioxide laser and copper-plated. It was a non-through conduction hole. Bump 4
5, the outer diameter φ0.5 of the spherical solder ball 45A
The inner diameter of the concave electrode pad 6 is 0.5 mm.
5 to 0.65 mm. When a soldering flux is used as an adhesive for temporarily fixing the solder ball 45A inside the concave electrode pad 6, the inner diameter of the electrode pad 6 is preferably 0.55 to 0.60 mm. 0.60 to 0.65 mm when using cream solder
Was good.

[0018]

As described above, the electrode pads formed on the outer conductor on the lower surface of the conventional wiring board on which the conventional electronic components are mounted can accurately position a large number of spherical bumps in a plane. Furthermore, it is very difficult to fix the spherical bumps from the surface of the substrate on the bump forming side to the height of the front end surface, but in the present invention, the conventional flat electrode pads are electrically insulated from the surface of the wiring substrate. Depressed inside the base material side to form a non-through conduction hole to form a concave electrode pad, it is possible to easily fit a spherical bump inside the concave electrode pad, and easily to the correct electrode pad position Positioning can be done.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a wiring board in a state where electronic components are mounted, illustrating the invention.

FIG. 2 is a sectional view showing a state where a spherical bump according to the present invention is recessed.

FIG. 3 is a cross-sectional view of a conventional wiring board for mounting electronic components.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Insulating base material 3 ... Upper surface outer layer conductor 4 ... Conductor layer in a non-through hole 5 ... Lower surface outer layer conductor 5A ... Bump forming side substrate surface 6 ... Recessed electrode pad 7 ... Penetrate insulating base material Hole 8: Conductive paste 10: Wiring board 17: Solder resist 22: Parent wiring board (mother board) 26: Connection land 28: Cream solder 31: Conventional wiring board 32: Through hole 33: Upper surface outer layer conductor 34: Through hole Plating layer 35 Lower surface outer conductor 36 Electrode pad 39 Filler 40 Electronic component 41 Bonding wire 45 Bump 45A Solder ball 47 Jig 48
…pedestal.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 23/12

Claims (1)

(57) [Claims] 1. A hole penetrating an insulating base material, an upper surface outer layer conductor closing one end surface of the hole penetrating the insulating base material, and a lower surface contacting the other open hole end surface. An outer layer conductor, and a conductor layer in a non-through hole that electrically connects the outer layer conductors on both surfaces,
A wiring board for mounting electronic components, characterized in that an upper surface outer layer conductor of the non-through conductive hole is used as a bonding land, and the inside of the non-through conductive hole is used as an electrode pad for mounting a bump for external connection.