JPH0590761A - Production of wiring board - Google Patents

Abstract

PURPOSE:To provide an easy method for producing multilayered wiring board and bonding the wiring boards. CONSTITUTION:A metallic metalize 11 with a high solder wettability is fitted inside a through-hole formed in an insulation layer 9 of wiring substrate, and is brought into contact with melted solder so as to fill solder 12 in the through- hole. Then the second wiring is formed thereon, resulting in enabling a through- hole with no difference of surface level to be formed easily. On the other hand, when the films having wiring 23 and through-holes are piled up to form a multilayered board, the solder 12 is melted, thereby the connection of wiring can be secured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of connecting electronic circuit elements such as an LSI and a multilayer wiring board and a method of making the same, and more particularly to a method of connecting fine wiring.

[0002]

2. Description of the Related Art In a multi-layer wiring board or a multi-layer wiring of an LSI, for example, as shown in FIG. It is performed by depositing a metal using plating or the like. However, in this method, since the recesses 8 in the through holes are left, there is a problem in that as the number of wiring layers increases, the surface irregularities become more severe, making it difficult to form the upper insulating layer and wiring.

A method for solving this point is, for example, a method of selectively depositing metal in the through holes by tungsten CVD or electroless plating to fill the through holes, or a method of filling the through holes with a metal paste. Invented.

On the other hand, in the connection between the LSI and the chip carrier (lead frame, TAB, PGA, etc.), due to the increase in the number of connection points accompanying the high integration of the LSI, C4 (Controlled Collapuse C) is changed from the conventional wire bonding or solder connection.
hip Conection) is used.

Also, in connection between the chip carrier and the substrate, the C4 connection is used in addition to the conventional pin connection, lead wire solder connection, and connector use.

[0006]

In the method of connecting through holes according to the prior art, for example, in the CVD method, the only metal that can be used is high-resistance tungsten, and since a high temperature is required at the time of deposition, an organic material is used. It cannot be applied to the substrate used for the insulating layer. Further, in the plating method or the method of filling the metal paste, if the through hole becomes fine and deep, abnormal deposition of plating or insufficient filling of the paste occurs, which causes disconnection and increase in through hole resistance.

On the other hand, in the C4 connection method, it is necessary to supply columnar solder to the terminals to be connected. As a method therefor, there are a method of placing a fine solder ball in a recess provided in a terminal and a method of forming a solder column by vapor deposition or plating. In the former case, it becomes difficult to supply solder balls as the terminals are made finer and the pitch is made narrower. In the latter case, it is necessary to perform steps such as lift-off and photoetching in order to form the solder pillars only on the terminal portions. Further, it is generally difficult to perform vapor deposition or plating by controlling the solder, which is an alloy, so as to have a predetermined composition.

Further, in C4, since the bonding between the substrates is performed only by the solder, there is a problem that the solder is cut due to thermal stress or the like, and it is very difficult to connect the C4 particularly in a large area.

[0009]

The connection of the through holes, which is the first problem described above, can be easily solved by filling the through holes formed in the insulating layer with molten metal.

The second problem can be solved by using a film having through holes filled with solder and having adhesiveness by thermocompression bonding.

[0011]

FIG. 2 shows an embodiment of through hole connection according to the present invention. In FIG. 2, the first wiring 4 is formed on the substrate 1 by sputtering or plating. An insulating layer 9 made of a heat resistant material such as polyimide is formed thereon, and a through hole reaching the first wiring 4 is opened by etching or laser processing. Next, the side walls of the through holes are selectively activated with palladium, titanium, carbon black or the like. Here, for example, nickel is deposited by nickel-phosphorus electroless plating to form the side wall metallized layer 11. In addition to nickel, a metal having good wettability with solder such as gold or copper can be used. Further, gold or the like can be continuously plated in order to prevent surface oxidation of the metallized layer 11.

Next, when this substrate is passed through a molten solder bath, the metallized layer 11 fills the solder 12 only into the through holes having good wettability with respect to the solder, and the solder on the surface of the insulating layer 9 having poor wettability. Does not remain. Alternatively, solder may be supplied onto the heated substrate to search for a squeegee to remove excess solder. If the distance between the squeegee and the surface of the insulating layer 9 is sufficiently small, the excess solder can be removed together with the search for the squeegee due to the surface tension of the solder. The temperature of the solder at this time needs to be equal to or lower than the heat resistant temperature of the insulating layer. For example, 400 ° C when using polyimide
Hereafter, it is preferably 300 ° C. or lower. Further, the diameter of the through hole is preferably 1 mm or less so that the solder in the through hole is retained by the surface tension. Further, it is desirable that the ratio of the depth to the diameter of the through hole is 0.5 or more.

Further, gold or the like can be formed as an antioxidation layer on the surface of the through hole thus formed.

Then, the second wiring 5 is formed again by sputtering or plating. Then, in order to ensure the connection with the second wiring 5, heating may be performed again up to the melting point of the solder.

By repeating the above steps, a multilayer wiring board can be formed.

At this time, in the case of a metal that easily reacts with the solder used for the wirings 4 and 5, such as aluminum or copper, it is necessary to form a reaction preventive layer 10 such as chromium or titanium on the surface of the wiring in contact with the solder. is there. Further, when the reaction prevention layer, the wiring, and the metallized layer form a natural oxide film and the wettability with respect to solder is lowered or the connection resistance is increased,
An anti-oxidation layer made of gold or the like can be provided on these surfaces.

If the side wall of the through hole cannot be selectively activated, a protective layer such as photoresist is formed on the insulating layer 9, and then the through hole is opened and activated. Finally, a method of peeling the protective layer can be used.

When the through holes are fine and the solder wettability alone cannot sufficiently fill the through holes, solder reflow is performed in a vacuum, or the substrate surface is wetted with solder flux. You can

When the substrate 1 and the insulating layer 9 are made of a material having high heat resistance such as ceramics, other than solder, metal braze or a metal having a relatively low melting point (such as zinc, tin, Gold, silver, copper) can also be used.

Further, solder may be vapor-deposited instead of the molten solder. In this case, the solder is formed on the entire surface of the substrate. The thickness of this solder is equal to or greater than the depth of the through hole. Next, when the substrate is heated to a temperature above the melting point of the solder, the solder melts and fills the inside of the through hole. Excess solder on the substrate can be easily removed by flowing down from the substrate by holding the substrate vertically or diagonally. Further, it may be removed by a squeegee during melting. This method is effective when the through holes are fine and the molten solder cannot be easily filled in the through holes.

According to the present invention, it is possible to form the wiring simultaneously with the through hole. An example thereof is shown in FIG. Similar to the above-mentioned embodiment, the first wiring 4 is formed on the substrate 1 and, if necessary, the reaction prevention layer and / or the oxidation prevention layer 10 is formed. Next, the lower insulating layer 9 is formed, and the etching stopper layer 13 is formed thereon. This is processed into a wiring shape by photoetching. At this time, it is set slightly larger than the actual wiring in consideration of the alignment error. At the same time, the portions that will become through holes are also etched. Next, the upper insulating layer 9 and the etching mask 14 are formed, and the etching mask of the wiring portion is removed by photoetching. Then, the insulating layer is etched by the above-described method until the first wiring 4 is exposed in the through hole portion and the etching stopper layer 13 is exposed in the wiring portion. The unnecessary etching mask 14 and the etching stopper layer 13 are removed, and then the through holes and the sidewalls and bottoms of the wiring portions are metalized 11 and the solder is filled 12 by the above-described method to form the through holes and the wirings. Complete.

It is necessary to select appropriate materials for the etching stopper layer 13 and the etching mask 14 depending on the method of etching the insulating layer 9. For example, when polyimide is used as the insulating layer and this is etched by reactive ion etching with oxygen, aluminum can be used. The etching mask 14 may not be used when etching the insulating layer by using a method such as laser processing that can specify the etching location. Further, when the depth direction can be controlled, the etching stopper layer 13 can be omitted. On the contrary, the etching stopper layer 13 can be left as a metallization layer under the wiring.

Next, FIG. 4 shows an embodiment for connecting the substrates according to the present invention.

In FIG. 4, the through hole 7 is opened in the heat resistant film 16 such as polyimide attached to the holding frame 18 by etching or laser processing.

The film 16 has adhesive layers 17 on both sides. The adhesive layer 17 is formed of a material that can withstand the melting temperature of the solder used for connection and that is melted or softened by heating during bonding and exhibits adhesiveness. For example, epoxy resin, polyether imide, low melting point polyimide and the like. When the film 16 itself is made of such a material, the adhesive layer 17 may not be provided,
The softening temperature of the film is preferably higher than the melting point of the solder so that the film is not deformed when the solder is filled.

The adhesive layer 17 may be provided not on the film 16 but on the substrate side to be joined. It is also possible to provide an adhesive layer on both the film and the substrate.

Instead of attaching the film 16 to the holding frame, it may be held by a temporary substrate which can be easily removed after the processing. It is also possible to adhere one side of the substrate to be connected from the beginning. In the case of a roll-shaped film or tape, it can be held by applying an appropriate tension. However, in this case, it is necessary to adjust the temperature and tension of the solder bath within a range in which thermal deformation of the film does not occur.

If a self-supporting substrate such as ceramic is used instead of the film 16, such holding means may be omitted.

Next, the activation and metallization of the side wall of the through hole is performed by the method described above. At this time, a protective layer may be previously provided on the adhesive layer 17 in order to prevent activation of the surface.

Next, the film is passed through a molten solder bath to fill the through holes with solder.

If necessary, suction or pressurization can be performed to assist in filling the solder into the through holes.

Thereafter, if necessary, an antioxidation layer such as gold is formed on the solder surface. It is necessary to pay attention to the composition and thickness of the antioxidant layer so that the antioxidant layer diffuses and disappears in the solder due to heating during the subsequent substrate bonding.

The substrate or LSI 20 or 21 to be connected and the above-mentioned film from which the holding frame is removed are connected to the terminals 19 of the substrate.
And the through holes 12 of the film are aligned and overlapped. Pressure is applied from the upper and lower sides to bring them into close contact, and the film is heated to either the melting point of the solder of the film or the bonding temperature of the adhesive layer, whichever is higher, to bond the terminals and the boards. At this time, the terminals 19 on the board side should be sufficiently wet with solder.
It is good to cover with gold or solder.

At this time, a part or the whole surface of the terminal may be formed in a convex shape so that the terminals can be joined securely.

By using the above method, a multilayer wiring board can be manufactured by collective lamination. An example thereof is shown in FIG.

The reaction preventive layer 10 with the solder and the wiring 23 are formed on the temporary substrate 22, and this is processed into a wiring shape by photoetching. In addition to this, the polyimide insulating layer 9 and the adhesive layer 17
To form a film. The through holes 12 filled with solder are formed by the method described above. Further, if necessary, an antioxidant layer is formed on the solder surface. Finally, the temporary substrate 1 is removed to obtain a polyimide film having wiring and through holes.

The required number of the films are aligned and superposed. Bonding and heating are performed to join the solder through holes to the wiring and to join the films. Through the above steps, a multilayer wiring board having an arbitrary number of wiring layers can be formed.

Here, the joining of the polyimide films does not have to be performed at once, and the joining of one layer or several layers may be repeated. In such a case, the removal of the temporary substrate may be performed after the films are joined.

In this embodiment, the case where polyimide is mainly used as the insulating material has been described, but any material having heat resistance at the melting point of the metal material used for filling the through holes may be used, and resins or ceramics other than polyimide may be used. Can be used. Alternatively, a composite material of an organic resin and an insulating material such as glass fiber or a ceramic filler may be used. Further, various solders, brazing materials, alloys and pure metals can be used as materials for filling the through holes.

[0040]

According to the present invention, a multilayer wiring board can be easily manufactured. In addition, the LSI, the chip carrier, the substrates, and the substrates can be easily joined. In particular, fine and large-area connection, which is impossible with the conventional joining method, becomes possible.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a multilayer wiring board according to the related art,

FIG. 2 is a sectional view of an example of a multilayer wiring board in which a through hole is formed according to the present invention,

FIG. 3 is a sectional view of a process of simultaneously forming a through hole and a wiring, which is an embodiment of the present invention,

FIG. 4 is a cross-sectional view of a process for joining substrates, which is an embodiment of the present invention;

FIG. 5 is a cross-sectional view of a process for manufacturing a multilayer wiring board by batch lamination, which is an embodiment of the present invention.

[Explanation of symbols]

9 ... Polyimide insulating layer, 10 ... Reaction prevention layer, 11 ... Metallization layer, 12 ... Solder filling through hole, 17 ... Adhesive layer, 22 ... Temporary substrate, 23 ... Wiring, 24 ... Thermocompression bonding jig.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location H05K 3/46 Q 6921-4E

Claims (9)

[Claims] 1. A through hole and / or a wiring is formed by forming fine holes in a substrate material having insulation and heat resistance and filling the inside of the hole with a metal that melts at a temperature lower than the heat resistant temperature of the substrate material. A method of manufacturing a wiring board, comprising: 2. The method for manufacturing a wiring board according to claim 1, wherein the through hole and / or the wiring is formed by bringing molten metal into contact with the surface of the board. 3. A method of manufacturing a wiring board according to claim 1, wherein a through-hole and / or wiring is formed by depositing a metal on the surface of the substrate and then heating and melting the metal. 4. The wettability with respect to the molten metal according to claim 1, wherein the wettability with respect to the molten metal is selectively improved by forming a metal thin film on the side wall and / or bottom surface of the fine hole and on a necessary portion of the substrate surface. According to the method, the molten metal selectively fills only a necessary portion such as the inside of the hole and does not adhere to other portions, and a method of forming a through hole and / or wiring. 5. The method for manufacturing a wiring board according to claim 1, 2, 3 or 4, wherein the formed through hole or wiring is heated and melted to form an electrical connection with the wiring or the through hole in contact therewith. .. 6. The method according to claim 1, 2, 3 or 4, wherein a metal filled in a through hole or wiring exposed on the surface of the substrate or penetrating the substrate is melted or softened again by heating the metal. Is a method of connecting wiring by crimping a terminal with an LSI or another wiring board to form an electrical connection between the LSI and the board and between the boards. 7. The adhesion of substrates according to claim 6, wherein both or one or both surfaces of the substrates to be connected are made of a material that softens and melts below a heat resistant temperature of the substrates to exhibit adhesiveness. A method of connecting substrates, in which wiring and wiring are connected sequentially or simultaneously. 8. The method for manufacturing a wiring board according to claim 6, wherein the connection is performed at least once. 9. A wiring board, an LSI, and other electronic parts manufactured according to claim 1, 2, 3, 4, 5, 6, 7 or 8, and an electronic circuit and device using the same.