JPH11340368A - Electronic component with bump electrodes and bump electrode forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic component having bump electrodes of long life where narrow pitch constitution is easily realized. SOLUTION: In an integrated circuit board 1, an integrated circuit is formed on one surface, a package 2 covering and sealing the integrated circuit is arranged, and a plurality of pads 3 are arranged on the other surface. A plurality of the pads 3 of the integrated circuit board 1 are bonded with each other and protruded in pillar shapes. A plurality of bump electrodes 4 are formed in which peripheries of sections parallel to the surfaces of the pads 3 have height previously set inside the peripheries of the surfaces of these pads 3. Since the sectional dimensions of the bump electrodes 4 become smaller than the surface dimensions of the pads 3, stress in bonding parts of the bump electrodes 4 and the pads 3 is reduced, and generation of breakdown in the parts is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic component with a bump electrode and a method for forming a bump electrode, and more particularly to an electronic component with a bump electrode and a method for forming a bump electrode mounted on a mounting substrate surface.

[0002]

2. Description of the Related Art The so-called surface-mount type electronic components such as semiconductor integrated circuits mounted on the surface of a mounting substrate are becoming increasingly more sophisticated and multi-functional, and are being miniaturized in response to demands for high-density mounting. Have been. In such an electronic component, a large number of the electrodes are replaced with a BGA (Ball Grid Array) type or a CSP.
(Chip Size Package) In many cases, the bump shape is such as a die. The first conventional electronic component with such bump electrodes is
Are shown in FIGS. 3A and 3B. In the semiconductor integrated circuit 100x of the electronic component with bump electrodes according to the first example, an integrated circuit is formed on one surface, and a large number (plural) of pads are connected to the integrated circuit on the other surface (mounting side). An integrated circuit board 1x on which 3x are formed in an array,
package 2 that covers and seals the integrated circuits on x
x and a number of pads 3 on the mounting side surface of the integrated circuit substrate 1x
x and a bump electrode 4x formed in the shape of a solder ball by being joined to each of them.

A solder ball-shaped bump electrode 4x is prepared by placing a solder ball formed and prepared in advance on each of the pads 3x to which the flux is applied, and performing a heating process (reflow process) to melt the solder ball. At the same time as joining to the pad 3x, the solder is cooled into a ball shape by the surface tension of the molten solder, or a cream solder having a predetermined thickness is applied on the pad 3x using a metal mask or the like, and the heat treatment is performed. Melt the cream solder into a ball,
It is formed by a method such as cooling. Note that the diameter of the ball-shaped portion is usually larger than the diameter of the pad 3x to increase the amount of solder so as to reduce problems such as coplanarity.

The former method requires a process of forming and preparing solder balls in advance, and a step of surely mounting the solder balls on the pads 3x one by one, so that the manufacturing cost is increased. In the latter method, the height of the solder ball (bump electrode 4x) varies (coplanarity) due to a variation in the amount of cream solder on the pad 3x due to a metal mask or the like, or a variation in the surface area of the pad 3x itself. In addition, there is a problem in that the design and manufacturing of a metal mask and the like for supplying a uniform amount of cream solder are complicated and sophisticated techniques are required.

Therefore, there is provided a bump electrode and a method of forming the bump electrode which can make the height of the bump electrode uniform without using solder balls and even if the amount of cream solder on the pad has a slight variation. It has been proposed (for example, see Japanese Patent Application No. 8-297080). FIG. 4 is a side view of such an electronic component with bump electrodes (second conventional example).
5 (a) to 5 (f) are process diagrams for explaining the bump electrode forming method.

[0006] The semiconductor integrated circuit 100y of the second example
An integrated circuit board 1y in which an integrated circuit is formed on one side and a large number (plural) of pads 3y connected to the integrated circuit are formed on the other side (mounting side); Package 2 that covers and seals the integrated circuit on 1y
y and a number of pads 3 on the mounting side surface of the integrated circuit substrate 1y
The bump electrode 4 includes a solder ball portion 90 which is formed in a ball shape by being joined to each of the components y, and a solder protrusion portion 91 protruding at the apex portion (tip side) of the solder ball portion 90.
y.

Next, a method of forming the bump electrode 4y of the semiconductor integrated circuit 100y will be described. First, a ball holding plate 70 having a predetermined depth and having a surface depression 71 that is not wetted by solder is prepared at a position corresponding to each of the many pads 3y of the integrated circuit board 1y.
(A)). Next, after each of the depressions 71 of the ball holding plate 70 is filled with the cream solder 80 (FIG. 5B), a predetermined amount (predetermined thickness and area) of the cream solder is applied thereon using a stencil mask or the like. Put 81 (Fig. 5
(C)) By heating, the cream solder 81 is melted and formed into a ball shape by the surface tension to form a solder ball portion 90 (FIG. 5D). And these solder ball portions 9
The semiconductor integrated circuit board 1y of the semiconductor integrated circuit is mounted on the substrate 0, and a large number of the pads 3y are joined to the solder ball portions 90 (FIG. 5 (e)).
The semiconductor integrated circuit 100y provided with the bump electrode 4y composed of the solder ball portion 90 and the solder projection portion 91 is extracted by the ball holding plate 70 from the solder projection portion 91 protruding from 0.
Is completed (FIG. 5F).

In this semiconductor integrated circuit 100y, the bottom surfaces of a large number of depressions 71 formed in the ball holding plate 70 are included on the same plane, and the bottom surfaces of these depressions 71 and the pads 3y of the integrated circuit substrate 1y are formed. By making the surface parallel, the height of the bump electrode 4y can be made uniform without being greatly influenced by the supply amount of the cream solder 81 and the like.

[0009]

In the above-described conventional electronic component with bump electrodes and the method of forming a bump electrode, the bump electrode 4x of the first example has a solder 3D on the pad 3x on the mounting side of the integrated circuit board 1x. Since a ball is formed and the solder ball usually has a structure having a diameter larger than the size of the pad 3x (bulging), stress is concentrated on the base of the pad 3x and the solder ball, and the solder ball is formed. In the second example, there is a problem that the pitch between the electrodes is determined by the diameter of the solder ball, and it is difficult to reduce the pitch. 4y has a structure in which the solder ball portion 90 is formed on the pad 3y, and therefore has the same problem as in the first example. In this case, the height of the bump electrode 4y can be made uniform without using solder balls and even if there is some variation in the amount of cream solder on the pad, but the number of steps for forming the bump electrode increases. And the ball holding plate 70 and the integrated circuit board 1y
If the parallelism between the bump electrode 4 and the
There is a problem that uniformity of the height y cannot be ensured.

It is an object of the present invention to firstly provide an electronic component with a bump electrode having a bump electrode which can be easily narrowed and has a long service life. It is another object of the present invention to provide a method for forming a bump electrode which can be formed with a small number of steps and easily ensuring uniformity of the height of the bump electrode.

[0011]

An electronic component with a bump electrode according to the present invention has the following features in order to achieve the above object. (B) A component board having a plurality of pads arranged and formed on one surface. (B) A plurality of pads of the component board are joined to each of the pads and protruded in a columnar shape. A plurality of bump electrodes having a predetermined height dimension within a peripheral edge of a surface

Further, each of the plurality of bump electrodes is
It is configured as a tapered shape that becomes thinner as it goes away from the joint portion of the component substrate with the pad.

The method of forming a bump electrode according to the present invention is characterized by including the following steps to achieve the above object. (B) At a position on one surface corresponding to each of the plurality of pads of the component substrate, the periphery of a cross section parallel to this surface is within the periphery of the surface of the pad and has a predetermined depth and bottom area. A jig preparing step of preparing a bump forming jig in which a plurality of bump-shaped holes are formed and which is difficult to adhere to a solder. (B) A jig heating step of heating the bump forming jig (c) Heated A step of supplying molten solder into each of the plurality of bump-shaped holes of the bump forming jig so as to overflow the molten solder; and (d) the surface of the molten solder in each of the plurality of bump-shaped holes of the bump forming jig is formed by the bump formation. A squeegee step of removing excess molten solder so as to be flush with the surface of the jig (e) Placing the component substrate on the bump forming jig from which excess molten solder has been removed A pad / solder fusion step of fusing and bonding the plurality of pads of the component substrate and the molten solder of the plurality of bump-shaped holes of the bump forming jig in correspondence with each other. An electrode extracting step of cooling and solidifying the bonded and joined molten solder together with the component substrate and the bump forming jig, and extracting the molten solder from the plurality of bump-shaped holes of the bump forming jig;

Further, as the depth of each of the plurality of bump-shaped holes of the bump forming jig from the surface of the bump forming jig is increased, the cross-sectional dimension parallel to the surface of the bump forming jig becomes larger. It is formed so as to be small.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of an electronic component with bump electrodes according to the present invention comprises a component substrate having a plurality of pads arrayed on one surface and a plurality of pads of the component substrate joined to each other. A plurality of bump electrodes projecting in a columnar shape and having a periphery of a cross section parallel to the surface of the pad within the periphery of the surface of the pad and having a predetermined height dimension. With such a configuration and structure, the stress applied to the joint of the bump electrode with the pad can be reduced, and this joint can be prevented from being destroyed and the life can be prolonged. Is determined by the size of the pad, so that the pitch can be reduced.

In one embodiment of the bump electrode forming method according to the present invention, the periphery of a cross section parallel to this surface is provided on one surface at a position corresponding to each of the plurality of pads on the component substrate. A jig preparing step of preparing a bump forming jig having a plurality of bump shaped holes formed within a peripheral edge of the surface and having a predetermined depth and bottom area, and a jig for heating the bump forming jig A solder heating step, a molten solder supplying step of pouring molten solder into each of the plurality of bump-shaped holes of the heated bump forming jig to an extent that the molten solder overflows, and a melting of each of the plurality of bump-shaped holes of the bump forming jig. A squeegee step of removing excess molten solder so that the surface of the solder is flush with the surface of the bump forming jig, and on the bump forming jig from which the excess molten solder has been removed A pad / solder fusion bonding step of mounting and bonding the plurality of pads of the component board and the molten solder of the plurality of bump-shaped holes of the bump forming jig in a corresponding manner, An electrode extracting step of cooling and solidifying the molten solder fused and bonded to the plurality of pads together with the component substrate and the bump forming jig, and extracting the molten solder from the plurality of bump-shaped holes of the bump forming jig. Is done.

With this configuration, the plurality of pads of the component substrate are directly fused to the molten solder filled in the plurality of pillar-shaped bump-shaped holes of the bump forming jig, and solidified. It can be a very simple and few steps of extracting from the forming jig, and it is only a simple work of placing the component substrate on the surface of the bump forming jig filled with molten solder in multiple bump-shaped holes Even if the parallelism is not suppressed with high accuracy, the uniformity of the height of the bump electrode corresponding to the processing accuracy of the plurality of bump-shaped holes can be secured.

[0018]

Next, an embodiment of the present invention will be described with reference to the drawings. FIGS. 1A and 1B are a side view and a plan view of a surface on a mounting side showing an embodiment of a semiconductor integrated circuit which is an electronic component with a bump electrode according to the present invention. The semiconductor integrated circuit 100 of this embodiment has an integrated circuit substrate 1 on which an integrated circuit is formed on one surface and a plurality of (many) pads 3 connected to the integrated circuit are formed on a mounting surface of the other surface. And a package 2 for covering and sealing the integrated circuits on the integrated circuit board 1 and a plurality of pads 3 on the mounting side surface of the integrated circuit board 1 and protruding in a columnar shape, and A plurality of bump electrodes 4 having a predetermined height dimension within the periphery of the surface of the pad in a cross section parallel to
And a configuration having the following.

With such a configuration and structure,
In contrast to the conventional example in which the bump electrode bulges more than the joint part with the pad, the bump electrode 4 is approximately the same as or slightly thinner than the pad 3, so that the stress at the joint part with the pad 3 is smaller than in the conventional example. It is possible to suppress the destruction of this joint portion and to extend the life. In addition, since the bump electrode 4 is approximately the same as or slightly thinner than the pad 3, the pitch between the bump electrode 4 and the pad 3 is determined by the dimensions of the pad 3, so that the pitch can be narrowed.

When each of the plurality of bump electrodes 4 has a tapered shape that becomes thinner as the distance from the joint with the pad 3 increases, the stress at the joint with the pad 3 is further reduced, leading to a longer life, and at the same time, a longer life. As described above, when the bump electrodes 4 are formed, there is an advantage that the plurality of bump electrodes 4 can be easily pulled out from the bump forming jig, and thus can be formed easily.

Next, a method of forming such a columnar bump electrode 4 will be described with reference to a process flow chart for explaining the bump electrode forming method shown in FIGS. 2 (a) to 2 (f). . The process flow shown in FIGS. 2A to 2F shows a process performed in a reflow furnace. Before entering this process flow, first, a plurality of pads are provided on one surface. In the example shown in FIG. 2, an integrated circuit board 1 having an integrated circuit formed on the other surface and covered with a package 2 and having a plurality of pads 3 connected to the integrated circuit is prepared. On the other hand, at a position corresponding to each of the plurality of pads 3 of the integrated circuit substrate 1 on one surface, the periphery of a cross section parallel to this surface is within the periphery of the surface of the pad 3 and is predetermined. A bump forming jig 20 having a plurality of bump-shaped holes 21 having a depth (corresponding to the height of a bump electrode) and a bottom area, which is difficult to be soldered, is prepared in advance.

Then, the jig 20 for forming bumps is put into a reflow furnace, and is placed on the conveyor belt 30 (FIG. 2).
(A)), the bump forming jig 20 is heated to a preset temperature (a temperature similar to the molten solder in the next step). Next, as shown in FIG. 2B, the molten solder 4 is placed on the bump forming jig 20 from the molten solder storage tank 40.
2 is supplied to such an extent that it overflows from each of the plurality of bump-shaped holes 21. Subsequently, as shown in FIG. 2C, the surface of the molten solder 41 in each of the plurality of bump-shaped holes 21 is bump-formed by a squeegee 50. Excess molten solder 41 is removed so as to be flush with the surface of jig 20.

Next, as shown in FIG. 2D, the integrated circuit board 1 prepared in advance is
The plurality of pads 3 (including the integrated circuit and the package 2 in this example) are placed on the bump forming jig 20 with the plurality of pads 3 aligned with the positions of the plurality of bump-shaped holes 21. The molten solder 41 in the shape hole 21 is fused and joined, and as shown in FIG. 2E, the molten solder 41 is cooled and solidified together with the integrated circuit board 1 and the bump forming jig 20 by blowing cold air or the like. As shown in FIG. 2 (f), the plurality of bump electrodes 4 solidified and bonded to the plurality of pads 3 are respectively extracted from the bump-shaped holes 21 of the bump forming jig 20, and the plurality of bump electrodes 4 of the electronic component 100 are removed. 4 are formed.

In this bump electrode forming method,
When molybdenum, machinable ceramic, or the like is used as the material of the bump forming jig 20, the solder is difficult to adhere. When using stainless steel, invar alloy, or the like, which has high heat resistance but is easily adhered to solder, it is preferable to coat with polytetrafluoroethylene (Teflon). Further, the transport belt 30 is formed in a mesh shape so that the molten solder 41 falls down and is easily collected when the excess molten solder 41 is removed, and the collected molten solder 41 is returned to the molten solder storage tank 40. It may be.

Further, when the integrated circuit board 1 is placed on the bump forming jig 20, if the conveyor belt 30 is stopped, the positioning between the pad 3 and the bump-shaped hole 21 becomes easy. Further, when the bump electrodes 4 are sequentially and continuously formed on the plurality of integrated circuit boards 1 using the plurality of jigs 20 for forming bumps, the transport belt 30 is intermittently driven, and What is necessary is just to process similarly.

According to such a bump electrode forming method, the bump forming jig 20 prepared in advance is heated to fill the plurality of bump-shaped holes 21 with the molten solder 41. The integrated circuit board 1 is mounted thereon, and the molten solder 41 in the bump-shaped holes 21 is directly bonded and solidified to each of the plurality of pads 3 to be solidified, and the solid solder is extracted from the jig for forming bumps. In addition, it is possible to form the bump electrode 4 which can be easily narrowed and has a long life. In addition, the integrated circuit board 1 is simply mounted on the bump forming jig 20 in which the plurality of bump-shaped holes 21 are filled with the molten solder 41 (of course, the plurality of pads 3 and the plurality of bump-shaped holes 21 are not connected). It is not necessary to maintain the parallelism between the ball holding plate 70 and the integrated circuit board 1y with high accuracy as in the second conventional example. The height of the bump electrode 4 can be made uniform to the order of the processing accuracy of the plurality of bump-shaped holes 21.

Each of the plurality of bump-shaped holes 21 of the bump forming jig 20 is formed such that as the depth from the surface of the bump forming jig 20 increases, the cross-sectional dimension parallel to the surface decreases. As a result, the bump electrode 4 which has been solidified and joined to the pad 3 is transferred to the bump forming jig 20.
It is easy to extract from.

[0028]

As described above, according to the present invention, each of a plurality of bump electrodes of an electronic component with bump electrodes is directly joined to each of a plurality of pads of the component substrate and projected in a columnar shape, and is parallel to the surface of these pads. By making the structure and shape such that the peripheral edge of the simple cross section is within the peripheral edge of the surface of these pads and has a predetermined height dimension,
Since the stress at the joint with the pad can be reduced, it is possible to reduce the occurrence of destruction of this joint and extend the life, and make the size of the bump electrode smaller than the surface dimension of the pad. Therefore, there is an effect that the pitch can be reduced.Also, a bump forming jig having a plurality of bump-shaped holes is prepared, and molten solder is provided in the plurality of bump-shaped holes of the bump forming jig. Is filled with the jig surface so that it is flush with the surface of the jig, the component board is placed on the jig surface, the molten solder in the plurality of bump-shaped holes is directly fused and bonded to the plurality of pads, and the pad is cooled and solidified. By extracting a plurality of bump electrodes bonded to the bump from the jig for bump formation and forming a plurality of bump electrodes, a bump electrode that can be easily narrowed in pitch and has a long life can be obtained simply and in a small amount. It can be easily formed in a small number of steps, and the component board can be placed on a bump forming jig filled with molten solder in multiple bump-shaped holes. There is an effect that the heights of the plurality of bump electrodes can be made uniform to the order of the processing accuracy of the plurality of bump-shaped holes, even if the height is not sufficiently suppressed.

[Brief description of the drawings]

FIG. 1 is a side view and a bottom view showing one embodiment of an electronic component with bump electrodes of the present invention.

FIG. 2 is a process flow chart for explaining one embodiment of a bump electrode forming method of the present invention.

FIG. 3 is a side view and a bottom view showing a first example of a conventional electronic component with bump electrodes.

FIG. 4 is a side view showing a second example of a conventional electronic component with bump electrodes.

5 is a process flow chart for describing a method for forming a bump electrode of the electronic component with bump electrodes shown in FIG. 4;

[Explanation of symbols]

 1, 1x, 1y Integrated circuit board 2, 2x, 2y Package 3, 3x, 3y Pad 4, 4x, 4y Bump electrode 20 Bump forming jig 21 Bump-shaped hole 30 Transport belt 40 Molten solder storage tank 41 Molten solder 50 Squeegee Reference Signs List 60 Component substrate supply unit 70 Ball holding plate 71 Indentation 80, 81 Cream solder 90 Solder ball unit 91 Solder protrusion 100, 100x, 100y Semiconductor integrated circuit

Claims (4)

[Claims] 1. An electronic component with bump electrodes, having the following configurations. (B) A component board having a plurality of pads arranged and formed on one surface. (B) A plurality of pads of the component board are joined to each of the pads and protruded in a columnar shape. A plurality of bump electrodes having a predetermined height dimension within a peripheral edge of a surface 2. The electronic component with bump electrodes according to claim 1, wherein each of the plurality of bump electrodes has a tapered shape that becomes thinner as the distance from a bonding portion with a pad of the component substrate increases. 3. A method for forming a bump electrode, comprising the following steps: (B) At a position on one surface corresponding to each of the plurality of pads of the component substrate, the periphery of a cross section parallel to this surface is within the periphery of the surface of the pad and has a predetermined depth and bottom area. A jig preparing step of preparing a bump forming jig in which a plurality of bump-shaped holes are formed and which is difficult to adhere to a solder. (B) A jig heating step of heating the bump forming jig (c) Heated A step of supplying molten solder into each of the plurality of bump-shaped holes of the bump forming jig so as to overflow the molten solder; and (d) the surface of the molten solder in each of the plurality of bump-shaped holes of the bump forming jig is formed by the bump formation. A squeegee step of removing excess molten solder so as to be flush with the surface of the jig (e) Placing the component substrate on the bump forming jig from which excess molten solder has been removed A pad / solder fusion step of fusing and bonding the plurality of pads of the component substrate and the molten solder of the plurality of bump-shaped holes of the bump forming jig in correspondence with each other. An electrode extracting step of cooling and solidifying the bonded and joined molten solder together with the component substrate and the bump forming jig, and extracting the molten solder from the plurality of bump-shaped holes of the bump forming jig; 4. The cross-sectional dimension of each of the plurality of bump-shaped holes of the bump forming jig, which is parallel to the surface of the bump forming jig, increases as the depth from the surface of the bump forming jig increases. 4. The method according to claim 3, wherein the bump electrode is formed to be small.