JPH06314881A - Manufacture of bumped circuit board - Google Patents

Abstract

PURPOSE:To provide a manufacturing method of a bumped circuit board which is capable of preventing irregularities about the shape and thickness of bumps, and what is more, excelling in soldering properties. CONSTITUTION:A ceramic board formation green sheet 21 is formed on a resin film 1, thereby obtaining a filmed green sheet 26. Then, a hole 10 is bored where the hole 10 is filled up with a conductor. Then, the filmed green sheet 26 is arranged so that its green sheet side 21 may face the other ceramic board formation green sheets 22, 23 and 24 where they are laminated and heat and contact-bonded. Then, a resin film 1 is removed from this laminated body 28 and backed. This construction makes it possible to provide a bumped circuit board.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a circuit board with bumps, which has bumps for connecting to electronic parts and the like.

[0002]

2. Description of the Related Art Conventionally, a wire bonding method or a QFP surface mounting method has been mainly used for mounting an integrated circuit on a circuit board. However, due to recent demands for miniaturization and high density, the flip-chip mounting method has attracted attention. In order to support flip chip mounting, it is necessary to form highly accurate electrodes (bumps) on the circuit board.

On the other hand, in order to mount the circuit board on another board (motherboard), conventionally, the DIP method or the PGA method has been adopted. However, due to the demand for smaller size, higher density, and lighter weight, there is a strong demand for a shift to the bump method that enables surface mounting. Here again, it is necessary to form highly accurate bumps on the circuit board. High-precision bumps mean bumps with small variations in diameter, thickness, and pitch.

The bump method is, as shown in FIGS. 11 and 12, that a bump 57 having a convex shape is formed on the surface of the circuit board 9, and the bump 57 and the pad 77 of the electronic component 7 (FIG. 11).
Alternatively, the bumps 57 and the pads 67 on the motherboard 6 (see FIG.
2) and are connected and fixed with solder 4. As a result, electrical connection between the circuit board 9 and the electronic component 7, or between the circuit board 9 and the motherboard 6 is achieved.

As the circuit board 9 based on the bump method, for example, as shown in FIG. 13D, ceramic substrates 93, 92, 91 and the ceramic substrates 91, 92 are shown.
Through hole 90 formed in the
Some of which have bumps 57 formed on top of them. The conductor 5 is filled in the through hole 90.
A wiring pattern 59 is formed on the ceramic substrates 92, 93.

Next, a method of manufacturing the circuit board with bumps will be described. First, as shown in FIG.
Green sheets 910, 920, 930 for forming the ceramic substrates 91, 92, 93 are prepared, and through holes 915, 925 are formed in the green sheets 910, 920. Next, the conductor 5 is filled in the through hole. Next, the wiring pattern 59 is formed on the green sheets 920 and 930.

Next, as shown in FIG. 13B, the green sheets 930, 920, and 910 are laminated in order from the bottom, and the positions of these green sheets are aligned and thermocompression bonded to obtain a laminated plate. Next, as shown in FIG. 13C, the bumps 57 are formed by the conductor 5 on the green sheet 910.
Next, the laminated plate is heated at the sintering temperature. By this,
The green sheets 930, 920, 910 are sintered to form the ceramic substrates 93, 92, 91, and the circuit board 9 with bumps as shown in FIG. 13D is obtained.

As a method of forming the bumps, there is a printing method of printing the conductor 5 on the green sheet 910.
Further, when the conductor 5 is filled in the silicone resin having the recessed portion is placed on the green sheet 910, and the conductor 5 is heated when the laminated plate is heated thereafter.
There is a transfer method for transferring to the 10 side.

[0009]

[Problems to be Solved] However, in forming bumps, in any of the above forming methods,
There are various problems described below. That is, in the above-mentioned printing method, since the printing thickness varies, the bump thickness becomes uneven as shown in the lower part of FIG. 14, and thin bumps 571 and thick bumps 572 and 573 are formed.

Therefore, the bumps 571, 572, 5
The circuit board 9 having 73 and the pads 6 of the mother board 6
When attempting to mount on 71, 672, 673, the gap 8 is generated between the thin bump 571 and the pad 671, so that they cannot be connected. Further, when the electronic component 7 is mounted (FIG. 11), there are the same problems as described above.

Therefore, it is necessary to make the bumps uniform in thickness. As a method for this, it is conceivable to polish the thick bumps with a surface grinder to make the thickness of the thin bumps uniform. However, carrying out this polishing work increases the number of manufacturing steps, and thus wastes both time and labor. In view of such conventional problems, the present invention aims to provide a method for manufacturing a circuit board with bumps, which can prevent variations in the shape and thickness of the bumps.

[0012]

The present invention relates to a method for manufacturing a circuit board with bumps having a ceramic substrate and bumps protruding from the surface of the ceramic substrate, wherein a green sheet for forming the ceramic substrate is placed on a resin film. Forming a green sheet with a film, a conductor filling step of forming a hole in the green sheet with a film, and filling the hole with a conductor for forming a bump, and the green sheet with a film. Laminating step in which the green sheet side faces another green sheet for forming a ceramics substrate, is laminated on it, and is thermocompression bonded to obtain a laminated body, and the resin film is removed from the laminated body to form a bump. A circuit board with bumps is obtained by performing a peeling step for forming a laminate and baking the above-mentioned bumped laminate. It is more a firing step in the production method of the bumps circuit board according to claim.

What is most noticeable in the present invention is that a hole for a film-formed green sheet is filled with a bump-forming conductor, and the film-formed green sheet is attached to the green sheet side for forming another ceramic substrate. Laminating the sheets so that they face each other, thermocompression bonding, then removing only the resin film, and then firing.

The resin film does not adhere to the green sheet. The resin film is preferably a resin film of polyester, polyphenylene sulfide, polyetherimide, polyethersulfone, polyetherketone, polyimide, methylpentene copolymer, or the like. The resin film has a thickness of 50 to 2
00 μm is preferable. If the thickness is less than 50 μm, the variation in the thickness of the green sheet may increase. On the other hand, if it exceeds 200 μm, it becomes difficult to form holes.

When the conductor is filled in the hole of the green sheet with a film, it is preferable to place the resin film side down on a flat plate and fill the conductor in the hole from the green sheet side. As a result, the filled conductor does not protrude from the upper end of the hole of the resin film. Therefore, in the subsequent peeling process, only the resin film can be easily peeled from the green sheet.

Further, even if the filled conductor projects from above the hole, the resin film can be easily removed without being disturbed by the projecting conductor. In addition, the green sheet used for the film-attached green sheet has a thickness of 100 to completely fill the conductor.
It is preferably ˜400 μm. Although the size of the hole is not particularly limited, it is preferable that the hole has a diameter of 0.1 to 0.8 mm. The conductor does not adhere to the resin film during thermocompression bonding. As the conductor, a material prepared by mixing tungsten, silver, silver palladium, copper, etc. with a binder to form a paste is used.

The green sheets for forming the ceramic substrate used in the preparation step and the laminating step are for forming the ceramic substrate, and one or a plurality of sheets can be laminated and used. Further, a wiring pattern can be formed by forming a wiring pattern on the surface of the green sheet using a conductor. If necessary, a through hole is provided in the green sheet and the through hole is filled with a through hole conductor, so that the wiring pattern of each ceramic substrate can be electrically connected. The through hole conductor may be the same material as the bump forming conductor or may be a different material.

[0018]

In the present invention, the green sheet with a film, in which the conductor is filled in the hole, is laminated with the resin film side facing the other green sheet for forming the ceramic substrate, and thermocompression-bonded. Only the film is removed. As a result, the conductor in the hole of the green sheet with film is displaced from the hole of the resin film and remains in the hole of the green sheet. Then, the conductor forms a convex bump on the surface of the green sheet.

Further, a conductor is filled in the hole of the resin film to form a bump. Therefore, the height and shape of the bump can be made uniform. Also, the bump is
It is formed at a certain position right above the hole of the green sheet. In addition, the shape of the bump can be freely set by selecting the shape of the hole.

The resin film does not adhere to the green sheet during the preparation process and the laminating process. Therefore, the work of removing the resin film from the green sheet with film is easy. Therefore, according to the present invention, it is possible to provide a method for manufacturing a circuit board with bumps, which can prevent variations in the shape and thickness of the bumps and has excellent soldering connectivity.

[0021]

【Example】

Example 1 An example according to the present invention will be described with reference to FIGS. In the circuit board with bumps manufactured according to this example, as shown in FIG. 10, convex bumps 51 are formed on the holes 10 of the ceramic substrate 31. The circuit board 3 with bumps is a ceramic substrate 31, 3
It is a multi-layer board in which 2, 33, and 34 are laminated, and wiring patterns 52 and 53 are formed inside and outside thereof. Holes 20 are formed in the ceramic substrates 32, 33, 34.

The bumps 51 are formed by using the conductor 5 made of tungsten paste. The holes 10 and 20 are also filled with the through hole conductor 50 made of the same material as the bump 51. The bumps 51 and the wiring patterns 53 are covered with Ni plating 61 and Au plating 62. The ceramic substrates 31 to 34
Is obtained by sintering green sheets 21 to 24 made of alumina.

Next, a method of manufacturing the circuit board with bumps will be described. First, in a preparatory step, as shown in FIG. 1, a green sheet 21 for forming a ceramics substrate is formed on a resin film 1 made of a polyester film having a thickness of 100 μm to obtain a green sheet 26 with a film. The green sheet 21 is prepared by kneading alumina with a solvent, a binder, a plasticizer and the like to prepare a slurry, and molding the alumina slurry to a thickness of 200 μm by a doctor blade method. Then, the green sheet with a film is cut into a desired shape.

Next, in the conductor filling step, as shown in FIG. 2, a hole 1 having a diameter of 0.5 mm was formed on the film-attached green sheet 26 using an NC punching machine.
Drill 0. Next, as shown in FIG. 3, the green sheet 26 with the film is placed on the flat plate 8 with the resin film 1 side facing down.

Then, the conductor 5 is filled into the hole 10 from the green sheet 21 side by the screen printing method. At this time, as shown in FIG.
May be at the same height as the upper end of the hole 10. In addition, FIG.
As shown in, the hole 10 may be slightly projected from the upper end. This is because the protruding conductor 5 is hidden inside the laminated body with bumps in a later step and adheres to the ceramic substrate by firing, so that there is no problem.

Next, in the laminating step, as shown in FIG. 5, the green sheet with film 26 is turned upside down. On the other hand, as shown in FIG. 6, other green sheets 22, 23, 24 for forming a ceramic substrate are prepared. Next, a hole 20 is formed in each green sheet 22, 23, 24, and the through hole conductor 50 is filled in the hole 20 by a screen printing method. Further, the wiring pattern 52 is formed on the surfaces of the green sheets 23 and 24.

Next, the green sheets 24, 23,
22 is laminated in order from the bottom to form a multilayer plate 27. Then,
As shown in FIG. 7, the green sheet with film 2
6, the green sheet 21 side is made to face the green sheet 22 of the multilayer board 27, laminated on it, and thermocompression bonded to obtain a laminated body 28.

Next, in a peeling step, as shown in FIG. 8, the resin film 1 is peeled from the green sheet 21 of the laminate 28. As a result, the conductor 5 is extracted from the hole 10 of the resin film 1, and as shown in FIG. 9, the bumped laminated body 29 in which the bumps 51 are formed on the surface of the green sheet 21 is obtained.

Next, in the firing step, the laminated body with bumps 29 is fired at 1550 ° C. As a result, the green sheets 21 to 24 are sintered to form the multilayer board of the ceramic substrates 31 to 34 shown in FIG. Next, a wiring pattern 53 is formed on the outside of the multilayer board, and then Ni plating 61,
Au plating 62 is applied. In this way, the circuit board 3 with bumps is obtained.

Example 2 In the manufacturing method of this example, first, in the preparation step,
A green sheet for forming a ceramics substrate was formed on a resin film made of a polyester film having a thickness of 125 μm to obtain a green sheet with a film. The above green _{sheets, CaO-Al 2 O 3 -SiO} 2 -
It is composed of 60 wt% of B ₂ O ₃ based glass and 40 wt% of alumina. Next, in the conductor filling step, holes were formed in the green sheet with the film, and the conductors made of the Ag / Pd paste were filled in the holes.

Then, a laminating step and a peeling step were performed in the same manner as in Example 1, and then, in a firing step, the bumped laminate was fired at 900 ° C. As a result, a circuit board with bumps was obtained. The surface of the circuit board with bumps is N
No i-plating or Au-plating was formed. Others,
This is the same as in the first embodiment.

Example 3 With respect to the circuit boards with bumps (Examples 1 and 2), the thickness of the bumps and the connection reliability when the bumps were connected to the pads of the mounted body via solder were evaluated. still,
For comparison, in forming the bumps of Examples 1 and 2, those formed by a method of printing a conductor on a green sheet were used as Comparative Example C1 and Comparative Example C, respectively.
It was set to 2. In forming the bumps of Example 2,
What used the transfer method was made into the comparative example C3. The transfer method is a method in which a conductor filled with a silicone resin having recesses is placed on a green sheet, and the conductor is transferred to the green sheet side when the laminated plate is heated thereafter. .

The evaluation results are shown in Table 1. In the table, the variation in bump height means the absolute value of the difference between the maximum and minimum values of bump height. Bad soldering means poor solder connection between bumps and pads. As is known from Table 1, in Examples 1 and 2, the bump height variation was 12
It was less than μm. Also, no soldering failure occurred. It should be noted that Comparative Examples C1 to C3 were significantly different from those of Examples 1 and 2 and defective soldering occurred.

[0034]

[Table 1]

[Brief description of drawings]

FIG. 1 is a sectional view of a green sheet with a film in Example 1.

FIG. 2 is a cross-sectional view of a green sheet with a film having holes formed therein in Example 1.

FIG. 3 is an explanatory diagram showing a method of filling a conductor in a hole according to the first embodiment.

FIG. 4 is an explanatory diagram showing a state in which the conductor in Example 1 projects from the upper end of the hole.

FIG. 5 is a cross-sectional view of the film-attached green sheet in which the conductor is filled in the holes according to the first embodiment.

FIG. 6 is a cross-sectional view of another green sheet according to the first embodiment.

FIG. 7 is a cross-sectional view of a laminated body in Example 1.

FIG. 8 is an explanatory view showing a state where the resin film is removed from the laminate in Example 1.

FIG. 9 is a sectional view of the laminated body with bumps in the first embodiment.

FIG. 10 is a sectional view of the circuit board with bumps according to the first embodiment.

FIG. 11 is an explanatory diagram showing a state where electronic components are mounted on a circuit board with bumps.

FIG. 12 is an explanatory diagram showing a state in which a circuit board with bumps is mounted on a motherboard.

FIG. 13 is a manufacturing process explanatory view showing a manufacturing method of a conventional example.

FIG. 14 is an explanatory view showing a defective state in which a circuit board with bumps on which bumps are formed by a printing method according to a conventional example is mounted on a motherboard.

[Explanation of symbols]

 1. ． ． Resin film, 10, 20. ． ． Hall, 21, 22, 23, 24. ． ． Green sheet, 26. ． ． Green sheet with film, 28. ． ． Laminate, 29. ． ． Laminated body with bumps, 3. ． ． Circuit board with bumps, 31, 32, 33, 34. ． ． Ceramics substrate, 5. ． ． Conductor, 50. ． ． Through-hole conductor, 51. ． ． Bump, 52, 53. ． ． Wiring pattern,

Claims (2)

[Claims] 1. A method for manufacturing a circuit board with bumps, comprising a ceramic substrate and bumps protruding from the surface of the ceramic substrate, wherein a green sheet for forming the ceramic substrate is formed on a resin film. A step of preparing a green sheet with a film, a step of filling a hole in the green sheet with a film, and filling the hole with a conductor for forming a bump, the green sheet with a film, and the other side of the green sheet with the film. Laminating step of facing the green sheet for forming a ceramics substrate, laminating on it, and thermocompressing to obtain a laminated body, and removing the resin film from the laminated body to obtain a bumped laminated body. And a firing step for obtaining the circuit board with bumps by firing the laminated body with bumps. A method of manufacturing a circuit board with bumps, comprising: 2. The bumped circuit board according to claim 1, wherein the resin film is made of polyester, polyphenylene sulfide, polyetherimide, polyethersulfone, polyetherketone, polyimide or methylpentene copolymer. Production method.