JPH10326961A - Formation of bump on wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a bump while facilitating correct positioning at an electrode pad by making a through hole in a wiring board, plating the through hole to form a through hole plating layer, press fitting a rod-like bump member therein and connecting the bump member with the through hole by soldering, or the like. SOLUTION: An outer layer conductor 5 is formed on the surface of a wiring board 1 for mounting an electronic device 40, e.g. a semiconductor device, and a plurality of through holes are made and subjected to electroless plating thus forming a through hole plating layer 4 on the inner circumferential surface of the through hole. A conductive paste 8 is then applied to the inside of an electrode pad 6 in the through hole and a rod-like bump, member 45B is fitted and soldered to form a bump. Fitting state can be stabilized by press fitting a prismatic bump member in the through hole of the electrode pad 6 in place of the rod-like bump member 45B. Since a rod-like bump member 45B is fitted fixedly in the through hole of the electrode pad, trouble can be prevented during work or transportation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a bump (protruding contact) on an electrode pad of a wiring board.

[0002]

2. Description of the Related Art A conventional technique will be described with reference to FIG. Conventionally, among the electronic components 40, a large number of electrode pads are used as connection terminals to the outside of the wiring board 31 on which high-density electronic components such as semiconductor elements and IC flat packages are mounted, that is, external terminals are provided on the lower surface of the wiring board. 36 to 2
A method of forming a spherical bump (protruding contact) member 45 made of solder or the like, for example, a solder ball on the electrode pad 36 by heat compression bonding or reflow soldering is provided on the electrode pad 36 by a BGA (ball grid grid). An array) package method, which can improve the quality of electronic components by increasing their density and miniaturization, and by reducing the rate of defective soldering.

First, in a conventional wiring board 31 for mounting electronic components, an upper outer conductor 33 and a lower outer conductor 35 of the wiring board 31 are electrically connected by through-hole plating. A large number of electrode pads 36 are planarly formed and set at predetermined positions at intersections of the lower surface outer conductor 35 on the two-dimensional lattice. Next, except for the connection lands and electrode pads 36 necessary for the outer layer conductors 33 and 35, the wiring board 31 is removed.
It is common to apply a solder resist 7 to both sides of the substrate. Next, cream solder is applied on the surface of the electrode pad 36, and a spherical bump member 4 is formed thereon.
5, for example, a solder ball is placed and a spherical bump is formed by reflow soldering. Alternatively, there is a method in which a spherical bump member 45 made of solder or the like is directly heated and pressed to the electrode pad 36.

[0004]

However, in the conventional planar surface mounting technology, when bumps having a spherical shape, a hemispherical shape, a mountain shape, or the like are attached to the electrode pads 36 at predetermined positions, the planar shape of the electrode pads 36 is reduced. Since the spherical surface and the spherical surface where the tip surface of the spherical bump member 45 has a spherical shape are in contact with each other, positioning has been extremely difficult. In addition, the spherical bump member 45 is accurately positioned on a large number of electrode pads 36 provided on the wiring board 31, and the spherical bump member 45 is misaligned during reflow soldering, thermocompression work, or transportation. Or detachment failure may occur.

Further, a difference R in the height of the tip surface of the spherical bump occurs due to variations in the size of the spherical bump member 45, warpage or twist of the wiring board 31, application amount of cream solder, and the like. When the wiring board 31 on which the bumps are formed is reflow-soldered to the connection lands of the parent wiring board, poor connection occurs between the spherical bumps of the wiring board 31 and the connection lands of the parent wiring board, resulting in unstable connection quality. As a result, securing connection reliability has been an issue.

[0006]

According to the present invention, there is provided a planar electrode formed on a lower surface outer layer conductor on a bump connection side of a wiring board on which an electronic component is mounted. One or more through holes are formed in the base material of the wiring board 1 as shown in FIG.
Plating is applied to the inner peripheral surface of the through-hole to form a through-hole plating layer. A rod-shaped bump member 45B is press-fitted into the through-hole of this through-hole, and each of the bump members and each of the through-holes are connected by solder or a conductive paste, thereby easily positioning the correct electrode pad position. A bump can be formed.

Further, the inner diameter of the electrode pad 6 in the through hole is made slightly larger than the outer diameter d _{1 of} the rod-shaped bump member 45B to be inserted, and the gap at the time of insertion is reduced to achieve a two-dimensional (planar). Increase positioning accuracy. The length L of the rod-shaped bump member 45B is slightly longer than the thickness of the wiring board 1 so that the height H from the surface 5A on the bump connection side to the tip of the rod-shaped bump member 45B is equal to 0. 20-0.60
The length of the rod-shaped bump member 45B is selected so as to protrude mm. Thus, in the electrode pad 6 of the through hole,
Since the bar-shaped bump 45B is fitted and the bump is formed by soldering, reflow soldering, or the like, the connection quality is stabilized. The height H from the surface 5A on the bump connection side to the tip of the rod-shaped bump member 45B protruding from the surface 5A.
Is a rod-shaped bump member 4 with a positioning jig in the height direction.
The height level of the protruding front end surface of 5B can be flattened, the distance between the front end portion of the bump member 45B and the connection land of the parent wiring board becomes constant, and the electronic component mounting wiring board 1 and the parent wiring board are Mounting with a large number of bump connections
It can be easily and reliably performed by a simple configuration.

The diameter of the through hole, which is the through hole, is
Rod-shaped case of press-fitting the bumps member 45D of the prism shape, which is one of the bumps member 45B is slightly smaller than the circumscribed diameter d ₂ which is in contact with the corners of the polygon, the prismatic bumps member 45D is press-fitted within the through hole , To be fixed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an embodiment will be described with reference to FIG. The surface outer layer conductor 3 on the electronic component mounting surface of the wiring board 1 on which the electronic component 40 such as a semiconductor element or an IC flat package is mounted, and the surface outer layer conductor 5 on the bump connection side are fixed at predetermined positions by printing or photography. Form a conductor,
Next, one or more through holes are formed by NC drilling, and electroless plating and electrolytic plating are performed to form a through hole plating layer 4 on the inner peripheral surface of the through hole. In this way, one or more through-hole electrode pads 6 used as connection terminals to the outside of the wiring board 1 are formed three-dimensionally (three-dimensionally) at predetermined positions of intersections on a two-dimensional lattice. ,
Set and arrange. Next, the surface outer layer conductor 3 on the electronic component mounting surface
Then, solder resists 7 are applied to both surfaces of the wiring board 1 except for necessary connection lands of the outer surface layer body 5 on the bump connection side and the electrode pads 6 of through holes.

Next, a conductive paste 8 is applied or filled into the electrode pads 6 of the through holes formed on the bump connection side of the wiring board 1, and a rod-shaped bump member 45B is fitted therein, and reflow is performed. Soldering is performed, or a flux for soldering is applied to the electrode pad 6 having the through hole, and a bar-shaped bump member 45B is fitted to form a bump by ordinary soldering. Examples of the conductive paste 8 include a silver paste, a copper paste, a solder paste, a cream solder, a silver-copper alloy paste, a silver palladium alloy paste, and a carbon paste. When the electronic component 40 is mounted on the surface of the electrode pad 6 in the through hole, an insulating film, an insulating sheet, and an insulating coating are provided between the wiring board 1 and the electronic component 40.

Further, as a rod-shaped bump member 45B used in the present invention, as shown in FIG. 2, a columnar bump member 45C, a prismatic bump member 45D, a rod-shaped bump member with projections which is a modified rod-shaped bump, etc. there are types 2 in cylindrical bumps member 45C having a simple shape is one of the rod-shaped bumps member 45B (a), the electrode pads 6 of the through hole than the outer diameter d ₁ of the bump
Has a slightly larger inner diameter so that an unnecessary gap does not occur during insertion.

Further, in order to improve the efficiency of fitting the rod-shaped bump member 45B into the electrode pad 6 of the through hole and to stabilize the fitting state, a prismatic bump member which is one of the rod-shaped bump members 45B is used. 45D is a through-hole electrode pad 6
Can be press-fitted into the through hole. The bumps member 45D of this prismatic, front view of FIG. 2 (b), as is shown in plan view, than the circumscribed diameter d ₂ which is in contact with the corners of the polygonal prismatic bumps member 45D, the wiring board 1 The fitting state can be stabilized by making the inner diameter of the through hole of the electrode pad 6 of the formed through hole slightly smaller and press-fitting and fixing the prismatic bump member 45D into the non-through hole. . Polygonal pillar-shaped bumps that are line-symmetric such as a square pillar, a hexagonal pillar, and an octagonal pillar are stably and well fitted to the prismatic bump member 45D.

As the rod-shaped bump member 45B, the height H from the surface 5A on the bump connection side of the wiring board 1 to the tip of the bump is set to 0.30 mm.
If the thickness is less than 20 mm, poor connection is likely to occur due to the bending of the thin rod-shaped bump member 45B or the insufficient amount of cream solder applied to the connection land of the parent wiring substrate to be solder-bonded to the rod-shaped bump member 45B. Also, 0.6
If it exceeds 0 mm, the distance between the connection land of the parent wiring board and the connection land becomes too large, so that the solder joint is incomplete. If the pitch of the high-definition electrode pads or the connection terminals is narrow, short-circuit failure is likely to occur. That is, the height H from the surface 5A on the pump connection side to the tip of the bump is 0.20 to 0.60.
It is good that it protrudes by mm.

The height H from the surface 5A of the bump connection side to the tip of the rod-shaped bump member 45B is determined by the height-direction positioning jig. The height of the surface can be flattened, and the distance between the tip of the rod-shaped bump member 45B and the connection land of the parent wiring substrate becomes constant, so that the bump between the electronic component mounting wiring substrate and the parent wiring substrate becomes bumpy. Mounting by connection can be reliably performed with a simple configuration.

In the present invention, the wiring board 1 for mounting electronic components is made of a glass epoxy base, a phenol base, a CEM material called a synthetic resin base, a Teflon-containing base, a polyimide resin base, a BT resin (bismaleimide-based). Triazine resin) An optimum material is selected from substrates such as a substrate, a modified BT resin substrate or a ceramic substrate and used. Further, the structure of the wiring board 1 may be any of a single-sided wiring board, a double-sided wiring board, and a multilayer wiring board, and the formation of the conductor pattern is not limited to the subtractive method or the active method.

[0016]

As described above, the conventional electronic component 4
The electrode pads 36 formed on the lower surface outer layer conductor 35 of the wiring board 31 on which the 0 is mounted accurately position a large number of spherical bump members 45 (for example, solder balls) in a planar manner, and furthermore, the tip of the spherical bump. Although it is very difficult to fix without eliminating the height difference between the surfaces, in the present invention, the rod-shaped bump member 45B is fitted into the electrode pad 6 of the through hole formed at a predetermined position, so that the correct electrode pad position can be obtained. Can be easily positioned.

Further, in the prior art, the spherical bump members 45 are displaced or detached during the work or transportation after a large number of spherical bump members 45 are temporarily fixed to the planar electrode pads 36. Although a defect occurred, the rod-shaped bump member 45B was fitted and fixed in the through hole of the electrode pad 6 of the three-dimensionally formed through hole of the present invention.
Defects during work and transportation no longer occur. As described above, the bump-shaped bump member 45B having a convex shape is fitted into the through-hole electrode pad 6, and the bump is formed by reflow soldering or the like, so that the connection quality is stabilized.

[Brief description of the drawings]

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

FIG. 2 is a front view and a plan view showing an example of a rod-shaped bump used in the present invention.

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

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Wiring board 3 ... Outer surface conductor on electronic component mounting surface 4 ... Through-hole plating layer 5 ... Outer surface conductor on bump connection side 5A ... Surface on bump connection side 6 ... Electrode pad of through hole
7: Solder resist 8: Conductive paste R: Difference in height of tip of spherical bump 31: Wiring board 33: Upper outer layer conductor 35: Lower outer layer conductor 36: Electrode pad 40: Electronic component 45: Spherical bump member 45B: rod-shaped bump member 45C: cylindrical bump member 45D: prismatic bump member H: height from the surface on the bump connection side to the level of the tip end surface of the bump

Claims (2)

[Claims] In a method of forming a bump on an electrode pad of a wiring board on which an electronic component is mounted, one or more through holes are formed in a base material, and the through holes are formed by plating the through holes. A first step of pressing a rod-shaped bump member into the through-hole, and a third step of connecting each bump member and each through-hole with solder or conductive paste. A method for forming a bump on a wiring board, comprising: 2. A prismatic bump member (45D) is used for the rod-shaped bump (45B), and the hole diameter of the through hole is set to the circumscribed diameter (d ₂ ) of the prismatic bump member (45D).
2. The bump forming method according to claim 1, wherein the bump is made slightly smaller.