JP2805432B2 - Method for manufacturing bumped circuit board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a circuit board with bumps, and more particularly, to a method of manufacturing a circuit board with bumps having fine bumps for connecting to electronic components and the like.

[0002]

2. Description of the Related Art Conventionally, as a method of mounting an integrated circuit on a circuit board, a method such as a wire bonding method in which an integrated circuit such as an LSI is fixed on the circuit board and the integrated circuit and the circuit board are connected by a thin metal wire. A QFP surface mounting method in which an integrated circuit is once packaged in a QFP (quad flat package) and then mounted on a circuit board again has been the mainstream.

[0003] However, the flip-chip method has attracted attention due to recent demands for miniaturization and higher density of semiconductor devices. Hereinafter, a method of mounting an integrated circuit on a circuit board by a flip chip method will be briefly described.

FIG. 2 is a cross-sectional view schematically showing a state in which an integrated circuit is adhered to a circuit board by a flip-chip method. In the drawing, reference numeral 31 denotes a ceramic circuit board.

The bumps 32 formed on the surface of the ceramic circuit board 31 and the bumps 34 formed on the surface of the integrated circuit 33 are electrically connected via solder 35 and fixed.

As a method for connecting the bumps 34 formed on the integrated circuit 33 and the bumps 32 formed on the ceramic circuit board 31 as described above, a solder 35 is usually bonded on the bumps 34 formed on the integrated circuit 33. In addition, a method is adopted in which the solder 35 on the integrated circuit 33 is brought into contact with the bump 32 on the corresponding ceramic circuit board 31 and is connected and fixed by heating.

As described above, the method of forming the bumps 32 and 34 on both the ceramic circuit board 31 and the integrated circuit 33 and connecting them via the solder 35 is adopted, whereby the ceramic circuit board 31 and the integrated circuit 33 are connected. Since a space is secured between them, the contaminants such as flux and solder scum generated during soldering can be reliably removed by washing, and the reliability can be improved.

On the other hand, as a method of mounting the ceramic circuit board 31 on another board (motherboard), a DIP (dual in-line package) system or a PGA (pin grid array) system has been conventionally adopted. Was.

However, even in this case, there is an urgent need for a shift to a flip-chip method in which the ceramic circuit board 31 can be directly surface-mounted on a motherboard due to demands for miniaturization, high density, and light weight.

FIG. 3 is a cross-sectional view schematically showing a state in which the ceramic circuit board 31 is adhered and fixed to the motherboard by the flip chip method.

The bumps 32 formed on the surface of the ceramic circuit board 31 and the bumps 42 formed on the surface of the motherboard 41 are electrically connected via solder 35 and fixed. As a method of connecting and fixing both, the same method as in the above case can be adopted.

FIG. 4 is a cross-sectional view schematically showing one example of a ceramic circuit board 31 used for connecting an integrated circuit or the like by the flip-chip method.

In order to achieve high-density mounting, internal wirings 37 are formed in a plurality of layers inside the ceramic circuit board 31, and through holes are formed to connect the internal wirings 37 to each other. I have. Then, in order to connect the internal wiring 37 formed inside the ceramic circuit board 31 and the mounted body by the flip chip method, bumps 32 are formed at the ends of the through holes exposed on the surface,
The connection with the internal wiring 37 is achieved. Ceramic circuit board 31 for high-density mounting as shown in FIG.
Then, the formed bump 32 becomes smaller and its density becomes considerably higher.

As described above, when the integrated circuit 33 is mounted on the ceramic circuit board 31 by the flip chip method, or when the ceramic circuit board 31 is mounted on the motherboard 41.
Is mounted on the ceramic circuit board 31 with high precision and high density. Here, the high-precision bump 32 refers to a pad with small variations in diameter, thickness (height), pitch, and the like, and the high-density bump 32 refers to a pad with small diameter and pitch.

A bump 32 is formed on a ceramic circuit board 31.
As a conventional method for forming a compound, W, Mo—Mn, A
ceramic circuit board 3 by a screen printing method using a conductive paste containing a conductive material such as u, Ag-Pd, Cu, etc.
One surface is coated and baked to bake the metal onto a substrate, and then, if necessary, plating with Ni and Au or C
There is a method of evaporating r-Cu or the like.

[0016]

However, when the bumps 32 are formed on the ceramic circuit board 31 by the above-described screen printing method, the following various problems occur.

FIG. 5 is a sectional view showing a state in which the bumps 32 formed on the ceramic circuit board 31 and the bumps 42 formed on the motherboard 41 are connected and fixed via the solder 35 by the screen printing method. It is.

As shown in FIG. 5, in the screen printing method, since the discharge amount of the paste is different between the opening portion and the non-opening portion of the mesh usually made of a wire mesh, the printing thickness varies. The heights of the bumps 32 formed on the surface of the ceramic circuit board 31 become uneven, and the bumps 32a having a low height and the bumps 32b, 32b having a high height are formed.
c are respectively formed. Therefore, when the ceramic circuit board 31 is mounted on the motherboard 42, a gap 36 is formed between the low bump 32 a on the ceramic circuit board 31 and the solder 35 bonded to the bump 42 on the motherboard 41. However, there is a problem that connection failure occurs.

Further, when the conductive paste is printed on the ceramic circuit board 31, the solvent in the conductive paste easily spreads on the surface of the ceramic circuit board 31, and "smearing" or "drip" is generated. If the distance between the bumps becomes 100 μm or less, there is a problem that the formed bumps 32 are short-circuited.

Further, in this screen printing method, the squeegee moves while pressing the screen, and the movement of the squeegee discharges the conductive paste from the screen toward the ceramic circuit board 31 to print the conductive paste on the surface of the ceramic circuit board 31. Since the screen bends when the squeegee presses the screen, the printed pattern is likely to be shifted from the set position, and the position accuracy of the printed pattern is low.

In order to prevent the above-mentioned problem from occurring, there is a method of forming the bumps 32 on the ceramic circuit board 31 by a vapor deposition method.

This vapor deposition method can apply a photolithography technique, so that a high-precision and fine pattern can be formed. However, there is a problem that the cost is higher than that of the screen printing method. there were.

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and it is possible to form a high-density and high-precision bump with a small variation in height. It is an object of the present invention to provide a method of manufacturing a circuit board with bumps, which can be manufactured at low cost without connection failure.

[0024]

In order to achieve the above object, a method of manufacturing a circuit board with bumps according to the present invention comprises a method of manufacturing a circuit board with bumps, wherein bumps are projected from a surface of a ceramic circuit board. A photoresist layer forming step of forming a positive photoresist layer on a ceramic circuit board using a photoresist, and performing an exposure process on the positive photoresist layer through a photomask having a predetermined bump formation pattern, and thereafter A concave portion forming step of forming a concave portion in a bump formation pattern on the positive type photoresist layer by performing a developing process; and a full surface exposing process of performing a full surface exposing process on the positive type photoresist layer having the concave portion formed thereon Filling the recess with a conductive paste for forming bumps; and filling the recess with the conductive paste filling step. An adhesive step of drying the obtained conductor paste and adhering a solid component in the conductor paste to the ceramic circuit board; and a photoresist layer for subjecting the positive type photoresist layer to a development treatment so that the photoresist layer disappears. And a baking step of baking the solid component in the conductor paste onto the ceramic circuit board by baking.

Hereinafter, a method for manufacturing a circuit board with bumps according to the present invention will be described with reference to FIGS.

First, as a photoresist layer forming step, a positive photoresist layer 12 is formed on a ceramic circuit board 11 using a liquid positive photoresist (FIG. 1A).

Ceramic circuit board 1 used in the present invention
1 is not particularly limited and may be, for example, a mullite ceramic substrate, a glass ceramic substrate,
An aluminum nitride ceramic substrate or the like may be used, and a substrate in which wiring and the like are formed may be used.

The positive photoresist layer 12 is formed by using a liquid positive photoresist, and the liquid photoresist is formed on the ceramic circuit board 11 by using, for example, a roll coater method, a bar coater method, a spin coater method, or a dip method. After applying the photoresist, 30 ~ 4 at 87 ~ 90 ° C
A heat treatment is performed in an oven or the like for about 0 minutes, followed by drying to form a solid positive photoresist layer 12. Examples of the liquid photoresist include AZ4903 and AZ4620A manufactured by Hoechst Japan, OP resist manufactured by Tokyo Ohka Kogyo, Accutrace manufactured by Tokyo Electron, and Provimer manufactured by Ciba Geigy Japan.

The thickness of the positive photoresist layer 12 to be formed is preferably 10 to 50 μm. If the thickness of the positive photoresist layer 12 is less than 10 μm, it will be difficult to fill the recess 10 formed in the positive photoresist layer 12 with the conductive paste 16 in a later step, while the thickness of the positive photoresist layer 12 will be reduced. Exceeds 50 μm, when development processing is performed in a later step, the concave portion 15 in the bump formation pattern shape is formed.
Is difficult to form completely.

As described above, in the present invention, since the positive type photoresist layer 12 is formed using the liquid photoresist,
Even when the surface of the ceramic circuit board 11 has irregularities on the order of a single micron, the surface of the formed positive photoresist layer 12 is horizontal.

Next, as a recess forming step, the positive photoresist layer 12 is exposed to ultraviolet light 14 or the like through a photomask 13 having a predetermined bump forming pattern (FIG. 1B), and then developed. By applying
Concave portions 15 are formed in the positive photoresist layer 12 in a bump formation pattern (FIG. 1C).

The conditions for the exposure treatment with the ultraviolet light 14 and the like are not particularly limited, and the exposure treatment can be performed under the conditions of the exposure treatment applied to the positive photoresist layer when forming a semiconductor substrate or the like. The conditions of the development treatment are not particularly limited, and the development can be performed by a commonly used method such as a spray method or an immersion rocking method.

According to the above method, the positive photoresist layer 1
2. The diameter is about 50-100 μm and the distance between each other is 5
The concave portion 15 approaching to about 0 μm can be formed. Next, as an entire surface exposure process, the entire surface of the positive photoresist layer 12 in which the concave portions 15 are formed is irradiated with ultraviolet rays 14 or the like to perform an entire surface exposure process (FIG. 1D).

The purpose of subjecting the entire surface of the positive photoresist layer 12 to an exposure process is to perform a development process in a later step.
This is for dissolving and eliminating the positive photoresist layer 12. The conditions of the exposure processing are not particularly limited, and may be the conditions usually performed.

The entire surface exposure process may be performed after a conductive paste filling process or a bonding process described later.

Next, as a conductor paste filling step, the recess 15 formed in the positive photoresist layer 12 is filled with a conductor paste 16 for forming bumps (FIG. 1E).

As the conductor for forming the bump, a known conductor material usually used for wiring such as a substrate can be used. Specific examples thereof include W, Mo-Mn, and A.
u, Ag-Pd, Cu and the like.

It is necessary to use a solvent which does not dissolve the positive photoresist layer 12 as the solvent of the conductive paste 16. This is because, when the conductive paste 16 is prepared using a solvent that dissolves the positive photoresist layer 12, when the conductive paste 16 is filled in the recess 15 of the positive photoresist layer 12, the photoresist layer 12 is dissolved in the solvent. However, this is because the shape of the recess 15 collapses. Examples of the solvent that does not dissolve the positive photoresist layer 12 include hydrocarbon solvents having a low dielectric constant, such as toluene, xylene, camphor oil, turpentine oil, and pine oil.

The resin (binder) used for the conductive paste 16 needs to be one that does not dissolve in a developer used in a later step. This is because the conductive paste 16 is filled in the recesses 15 formed in the positive photoresist layer 12 and then dissolved and eliminated by contacting the positive photoresist layer 12 with a developing solution. This is so as not to dissolve in the liquid.
Since the developer is usually an aqueous solution, the resin used for the conductor paste 16 needs to be a water-insoluble resin. Specific examples of the resin include ethyl cellulose, acrylic resin, and methacrylic resin.

For the above reasons, as the conductor paste 16 used in the present invention, for example, the conductor powder is 80 to 92%.
It is preferable that the composition is such that the resin such as acrylic resin is 2 to 6 wt% and the solvent such as toluene is 2 to 18 wt%.

In order to improve the adhesion between the conductor and the ceramic substrate after firing, an inorganic binding powder such as glass, SiO ₂ , TiO _2, etc. is added to the conductor powder in an amount of 2.5 to 1%.
0 wt% may be added.

As shown in FIG. 1E, the conductive paste 16 having the above composition is filled in the recesses 15 of the photoresist layer 12 by directly rubbing the conductive paste 16 into the recesses 15 using a Teflon spatula 17. I just need to put it. The positive photoresist layer 1 other than the recess 15
In the case where the conductive paste 16 remains on the surface of No. 2, it can be almost removed by scraping off using a Teflon spatula 17 to which the conductive paste 16 does not adhere. Furthermore, when there is an extremely thin layer of the conductive paste 16 that cannot be removed by the above operation, the conductive paste 16 can be dried and then removed by polishing using a wrapping film.

Next, as a bonding step, the conductive paste 16 filled in the recess 15 is dried, and the solid component in the conductive paste 16 is bonded to the ceramic circuit board 11.

In this step, the solid component in the conductive paste 16 is adhered to the surface of the ceramic circuit board 11 via the resin by evaporating the solvent component in the conductive paste 16 and performing heat treatment at the same time.

Thereafter, as a photoresist layer disappearing step,
The positive photoresist layer 12 is subjected to a development process to make the positive photoresist layer 12 disappear (FIG. 1).
(F)).

As described above, since the positive type photoresist layer 12 has been subjected to the exposure processing, it is dissolved and disappears by performing the development processing using the developing solution. No special conditions are required as conditions for the development processing. In addition, since a water-insoluble resin is used as the solvent of the conductive paste 16, the shape of the conductive material including the resin formed in a bump pattern does not collapse.

In this case, if the method of removing the positive photoresist layer 12 by burning it in an oxidizing atmosphere is employed, a large amount of resin must be burned.
Severe conditions are required and thermal damage and oxidative damage to the ceramic circuit board 11 and conductors are large, which is not preferable.

Finally, as a baking step, baking is performed to decompose and eliminate organic components in the conductor paste 16 including the conductor adhered to the ceramic circuit board 11.
The conductor component in the conductor paste 16 is baked on the ceramic circuit board 11 to form the bump 18 (FIG. 1).
(G)).

The firing conditions in this case differ depending on the type of the ceramic circuit board 11 and the type of the conductor material, but it is necessary that the resin and the like be sufficiently decomposed and disappear, and that the conductor be firmly adhered to the ceramic circuit board 11. Becomes

Through the above steps, a pattern of the bumps 18 made of a conductive material is formed on the ceramic circuit board 11.

The bumps 18 may be appropriately plated with Ni or
u plating may be performed, or Cr, Cu, or the like may be deposited.

[0052]

According to the method of manufacturing a circuit board with bumps according to the present invention, in a method of manufacturing a circuit board with bumps in which bumps are protruded from the surface of a ceramic circuit board, a positive electrode is formed on the ceramic circuit board by using a liquid photoresist. Forming a photoresist layer, forming a photoresist layer,
Forming a recess in the positive photoresist layer in a bump formation pattern by subjecting the positive photoresist layer to an exposure process through a photomask having a predetermined bump formation pattern and then performing a development process; A step of performing an overall exposure process of performing an overall exposure process on the positive photoresist layer having the recess formed therein, a process of filling a conductive paste for forming a bump in the recess, and a process of filling the recess with the conductive paste. Drying the conductive paste and bonding a solid component in the conductive paste to the ceramic circuit board; and developing the positive photoresist layer to remove the photoresist layer by removing the photoresist layer. And baking the solid component in the conductor paste on the ceramic circuit board by firing. Baking step, a horizontal positive-type photoresist layer is formed on the ceramic circuit board in the photoresist layer forming step, and the concave part formed for patterning by photolithography is formed in the concave part forming step. The position accuracy is also very high, and a precise bump-shaped pattern-shaped recess is formed,
The conductor paste layers filled in the recesses in the conductor paste filling step have the same height, and the pattern does not bleed or drop as in the case of screen printing. Through the subsequent bonding step, photoresist layer erasing step, and baking step, a circuit board with bumps having a uniform height, a precise shape, and a bump with extremely high positional accuracy can be manufactured at a relatively low cost. Manufactured. Further, fine bumps are formed as compared with the conventional screen printing method.

Since the removal of the positive photoresist layer after the formation of the conductor pattern is performed by a wet process, the ceramic circuit board and the conductor material may be thermally damaged or oxidized as in the case of removal by burning. No damage is taken.

Therefore, even when an integrated circuit is mounted on the circuit board with bumps, or when the circuit board with bumps is mounted on a motherboard, no short circuit or poor connection occurs.

[0055]

Examples and Comparative Examples Examples of the method for manufacturing a circuit board with bumps according to the present invention will be described below with reference to the drawings.

FIGS. 1A to 1G are cross-sectional views schematically showing steps in a method for manufacturing a ceramic circuit board with bumps according to an embodiment.

[Example 1] First, a liquid positive type photoresist (A Hoechst Japan Co., Ltd.) was formed on a ceramic circuit board 11 (surface roughness ± 3 μm) made of alumina.
Using Z4903), a positive photoresist-containing layer having a thickness of about 25 μm was formed by a bar coater method.
Since the formed positive photoresist-containing layer contains a liquid component such as a solvent, it is dried by placing it in an oven maintained at 90 ° C. for 30 minutes, thereby drying the solid positive photoresist layer. 12 (FIG. 1)
(A)).

Thereafter, a photomask 14 having a predetermined bump formation pattern (bump diameter: 50 μm, pitch between bumps: 100 μm) is formed on the positive photoresist layer 12.
UV light was applied under the condition that the exposure amount was 3000 mJ / cm ² (FIG. 1B).

Next, a developing solution (manufactured by Hoechst Japan Co., Ltd.)
AZ400K), the ceramic circuit board 11 having the positive photoresist layer 12 was immersed, rocked and developed to form a concave portion 15 in the positive photoresist layer 12 in a bump formation pattern (FIG. 1 ( c)).

Next, the ceramic circuit board 11 was placed on a hot plate maintained at 120 ° C., heated for 30 seconds, and then the entire surface of the photoresist layer 12 was irradiated with ultraviolet rays 14 under the condition that the exposure amount was 3000 mJ / cm ² . (Figure 1
(D)).

Next, Mo and Mn (both having an average particle size of 3 μm) were used as conductor materials, and SiO ₂ and T were used as inorganic bonding materials.
A conductor paste 16 containing 85 wt% of a powder in which iO ₂ is mixed at a ratio of 75: 15: 5: 5 (weight ratio), 6 wt% of an acrylic resin and 9 wt% of turpentine oil, A small amount of this conductive paste 16 is placed on the positive photoresist layer 12 in which the concave portions 15 are formed, and the Teflon spatula 17 is placed on the positive photoresist layer 1.
The conductive paste 16 was rubbed into the concave portion 15 of the positive photoresist layer 12 while being moved horizontally while being in contact with the surface of the second photoresist layer 12 (FIG. 1 (e)). The conductive paste 1 is applied to the surface of the positive photoresist layer 12 except for the recesses 15.
When 6 remained, it was scraped off with a Theron spatula 17 to which the conductive paste 16 did not adhere.

Next, the conductor paste 16 filled in the recess 15 is dried by heating to 90 ° C., and the acrylic resin in the conductor paste 16 is removed from the ceramic circuit board 11.
Was adhered to. If a very thin conductor paste layer of about one particle layer, which could not be removed even by scraping off the excess conductor paste 16 with the Teflon spatula 17, is applied to the surface of the photoresist layer 12 other than the recesses 15, a wrapping film (Sumitomo) 3M alumina grain (particle size 1μ)
m) was removed by polishing for about 10 seconds by bonding.

Next, the ceramic circuit board 11 having undergone the above-described steps is applied to a developing solution (AZ400 manufactured by Hoechst Japan).
K) is immersed in the substrate and subjected to a development process by swinging to dissolve and eliminate the positive type photoresist layer 12 and to remove only the dried body of the conductor paste 16 into the ceramic circuit board 1.
1 (FIG. 1 (f)).

Then, by baking at 1500 ° C. in a nitrogen-hydrogen mixed gas atmosphere containing trace water vapor, the resin in the conductor paste 16 is decomposed and disappeared, and the conductor is baked on the ceramic circuit board 11 to form the bumps 18. Was formed (FIG. 1 (g)).

Thereafter, the surfaces of the bumps 18 were plated with Ni and Au.

Example 2 An alumina-cordierite-based ceramic circuit board having an Ag wiring inside was used as the ceramic circuit board 11, and a positive electrode was formed on the ceramic circuit board 11 in the same manner as in the first embodiment. A mold photoresist layer 12 was formed, and a recess 15 was formed in the positive photoresist layer 12.

Next, the conductor material was changed to Cu powder (particle size: 2 μm).
A conductor paste 16 having the same composition as in Example 1 was used, except that powder mixed with Pb and lead borosilicate glass at a weight ratio of 95: 5 was used. The conductive paste 16 was filled in and bonded to the concave portion 15 of the positive photoresist layer 12, and the positive photoresist layer 12 was dissolved and disappeared by a developing process. After this, 9
The powder was fired at 00 ° C. to sinter the Cu powder and adhered to the ceramic circuit board 11 to form a bump 18 on the ceramic circuit board 11 and plating was performed.

By measuring the variation in height and short-circuit rate of the bumps 18 of the circuit boards with bumps according to the first and second embodiments thus obtained, the bumps 18 can be used as the bumps of the mounted body. The circuit board with bumps was evaluated by measuring the percentage of defective soldering when connected via solder. Table 1 shows the results.

The variation in the bump height shown in Table 1 is based on the height of the bump 18 formed on each of the 200 samples manufactured according to the above-described embodiment (Surf manufactured by Tokyo Seimitsu Co., Ltd.).
com112B), and describes the difference between the maximum and minimum values of the obtained bump height.

Next, the short-circuit rate of the bumps shown in Table 1 is a result of observing the shape of the formed bumps 18 with an optical microscope and examining the proportion of the bumps 18 in contact with each other.

The soldering failure rate shown in Table 1 is determined by soldering the formed bumps 18 and the bumps of the mounted body and determining whether there is a connection failure between the bumps to be connected to each other. Inspection of each bump shows the proportion of bumps in which connection failure was found to have occurred. In this case, 200 samples were manufactured under exactly the same conditions as in Examples 1 and 2, and the above evaluation was performed.

[Comparative Examples 1-2] On the other hand, in order to specifically compare with the case where bumps were formed by a conventional method, as a comparative example, bumps were directly formed on a ceramic circuit board by using a screen printing method. Formed.

That is, in Comparative Example 1, Example 1 was placed on the ceramic circuit board 11 made of alumina used in Example 1.
A conductive paste pattern was formed by a screen printing method using the Mo-Mn-based conductive paste used in the above, and after sintering, Ni plating and Au plating were performed as in Example 1. In Comparative Example 2, a pattern of a conductor paste was formed on the substrate used in Example 2 by the screen printing method using the Cu conductor paste used in Example 2, baked, and similarly plated.

The circuit boards with bumps according to Comparative Examples 1 and 2 were evaluated in the same manner as in the example. The number of samples of the comparative example is the same as that of the example.

[0075]

[Table 1]

As is evident from Table 1, in the circuit boards with bumps according to Examples 1 and 2, the height variation of the bumps 18 was uniformed to 1 μm, and the short-circuit rate of the bumps 18 was as accurate as zero. It can be seen that the bumps 18 of the pattern are formed. On the other hand, in the bumped circuit board according to the comparative example, since the bumps are formed by the conventional screen printing method, the variation in bump height is 5%.
μm, and an accurate pattern is not formed due to bleeding during printing.
It is a very high value of 0%.

In the case where the circuit board with bumps according to the embodiment is used and the mounted body is connected and fixed via solder, there is no soldering failure, and each bump is connected well. In the comparative example, the defective soldering rate is extremely high due to the uneven height of the formed bumps.

[0078]

As described above in detail, in the method of manufacturing a circuit board with bumps according to the present invention, there is provided a method of manufacturing a circuit board with bumps in which bumps are projected from the surface of a ceramic circuit board. A photoresist layer forming step of forming a positive photoresist layer on a ceramic circuit board by using a photomask, and performing an exposure process on the positive photoresist layer via a photomask having a predetermined bump formation pattern, followed by a development process By performing the above, a concave portion forming step of forming a concave portion in a bump formation pattern in the positive photoresist layer, and a whole surface exposure process step of performing a whole surface exposure process on the positive photoresist layer in which the concave portion is formed, A step of filling the recess with a conductive paste for forming bumps; and a step of filling the recess filled with the conductive paste. Drying the paste, a bonding step of bonding the solid component in the conductor paste to the ceramic circuit board, a photoresist layer disappearing step of developing the positive photoresist layer and removing the photoresist layer, A baking step of baking the solid component in the conductor paste onto the ceramic circuit board by baking, so that the bumps have bumps having uniform height, accurate shape, fineness and extremely high positional accuracy. Circuit boards can be manufactured relatively inexpensively.

Further, since the removal of the positive photoresist layer after the formation of the conductor pattern is performed by a wet process, it is possible to prevent the ceramic circuit board and the conductor material from being thermally damaged or oxidized.

Therefore, when an integrated circuit is mounted on the circuit board with bumps according to the present invention or when the circuit board with bumps is mounted on a motherboard, it is possible to prevent a short circuit or a connection failure from occurring.

[Brief description of the drawings]

FIGS. 1A to 1G are cross-sectional views schematically showing steps in a method for manufacturing a ceramic circuit board with bumps according to an embodiment.

FIG. 2 is a cross-sectional view schematically showing a state in which an integrated circuit is bonded to a circuit board by a flip chip method.

FIG. 3 is a cross-sectional view schematically showing a state in which a ceramic circuit board is bonded and fixed to a mother board by a flip chip method.

FIG. 4 is a cross-sectional view schematically showing an example of a ceramic circuit board used for connecting an integrated circuit or the like by a flip chip method.

FIG. 5 is a cross-sectional view showing a state in which bumps formed on a ceramic circuit board by screen printing and bumps formed on a motherboard are connected and fixed via solder.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Ceramic circuit board 12 Positive photoresist layer 13 Photomask 15 Concave part 16 Conductive paste 18 Bump

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Koichi Uno 2701-1, Iwakura, Omine-cho, Omine-cho, Mine-shi, Yamaguchi Prefecture (72) Inventor Yoshikazu Nakata 4-5 Kitahama, Chuo-ku, Osaka-shi, Osaka No. 33 Sumitomo Metal Industries Co., Ltd. (56) References JP-A-6-112212 (JP, A) JP-A-1-309342 (JP, A) JP-A-3-504064 (JP, A) (58) Surveyed field (Int.Cl. ⁶ , DB name) H01L 21/60 311 H01L 21/92 604

Claims (1)

(57) [Claims] 1. A method for manufacturing a circuit board with bumps, wherein a bump is projected from a surface of a ceramic circuit board, comprising: a step of forming a positive photoresist layer on the ceramic circuit board using a liquid photoresist; A concave portion for forming a concave portion in the positive photoresist layer in a bump formation pattern by performing an exposure process on the positive photoresist layer through a photomask having a predetermined bump formation pattern, and thereafter performing a development process; A forming step, an overall exposure processing step of performing an overall exposure processing on the positive photoresist layer in which the recess is formed, a conductor paste filling step of filling the recess with a conductive paste for bump formation, and a filling of the recess. The obtained conductor paste is dried, and the solid component in the conductor paste is separated from the ceramic paste by the ceramics. An adhesion step of adhering to a circuit board; a photoresist layer disappearing step of developing the positive photoresist layer to eliminate the photoresist layer; and firing the solid component in the conductor paste to the ceramic circuit board. A method of manufacturing a circuit board with bumps, comprising a baking step of baking.