JP2002299835A - Multilayered circuit board precursor and method of manufacturing multilayered circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayered circuit board precursor that can be applied to reduce the thickness of an insulating film and can suppress the cutting and exposure of internal wiring at dicing time caused by the positional deviation, etc., of the wiring and the reliability drop of the wiring caused by the cutting and exposure. SOLUTION: A multilayered circuit board is manufactured by forming a laminate A on a resin film 11 by repetitively forming insulating films 13 which are formed by applying and drying slurry containing a ceramic material and an organic binder, via-hole conductors 14, and wiring patterns 15 which are formed by applying conductive paste to the surfaces of the films 13 and drying the paste. Then the laminate A is removed from the resin film 11 and baked. The maximum coefficient of thermal shrinkage of the resin film 11 in the thermal history of the film 11 from the formation of the insulating film 13 on the film 11 to the removal of the laminate A from the film 11 is controlled to <=0.3%, by sticking the film 11 to a supporting substrate 12 which is low in thermal shrinkage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a precursor used for manufacturing a multilayer circuit board applied to electronic circuit formation, and a method for manufacturing a multilayer circuit board.

[0002]

2. Description of the Related Art Conventionally, ceramics have been widely used as materials for multilayer circuit boards because of their excellent electrical properties. Especially, in recent years, with the practical use of glass ceramics, various types of high dielectric constant or low dielectric constant which have not been obtained with circuit boards until now are manufactured, and circuit elements such as capacitors, inductors, and filters are built in a multilayer circuit board. Those having a complicated structure are also being put to practical use. The schematic structure of these multilayer circuit boards is such that a plurality of wiring layers are formed inside the ceramics, and the ceramics are electrically connected to the internal wiring layers outside the ceramics, and are used for component mounting on the surface layer or secondary mounting on the motherboard. A connection terminal conductor layer and the like are also provided.

As a general method for manufacturing such a multilayer circuit board, first, a slurry is prepared by mixing a ceramic material as a board material, an organic binder and a solvent, and the slurry is applied on a carrier film such as PET. After drying, the carrier film is peeled off to obtain one insulating film.

[0004] Then, via-hole conductors and wiring patterns are formed on the insulating film peeled off from the carrier film, and they are laminated in an arbitrary number of layers to form an external conductor layer, and then appropriately divided into individual pieces. Later, it is obtained by firing.

[0005] Such a multilayer circuit board has a reduced size and height,
In response to demands such as an increase in the number of built-in elements,
Multilayering is required, and the thickness of the insulating film per layer is required to be reduced from the conventional thickness of about 150 μm to 100 μm or less, more preferably 50 μm or less.

When such a thinned insulating film is used in the above-mentioned conventional process, the strength of the insulating film alone is very low, so that the insulating film is easily broken, and the insulating film is detached from the carrier film at an early stage. There is a problem that can not be. Therefore, the carrier film is not detached from such a thinned insulating film until immediately before lamination,
It is necessary to release the film after lamination.

[0007]

However, a PET film is generally used as the carrier film due to requirements for chemical stability and low cost.
T has the property of thermally contracting when exposed to high temperatures. Therefore, even if a positioning reference is provided for the carrier film, the dimensions of the carrier film fluctuate due to the influence of hot-air drying and the like, so that the lamination accuracy cannot be obtained, and the snap line or the break line for dividing into individual pieces is shifted. Occurs.

Specifically, in the case of a normal PET film, shrinkage of 1% or more occurs at 150 ° C. In many cases, when a PET film is used as a carrier film, it is used with a work size of 10 cm square or more. P
If the insulating film follows the 1% ET shrinkage,
mm shrinkage will occur. As a result, when forming a snap line for dividing the pieces before firing, the dimensions do not match mechanically.
If image recognition is performed for each book and it is divided, it takes time and is not practical.

Specifically, when components are mounted on the surface layer of a multilayer circuit board and then divided into individual pieces along a snap line, a part of the internal wiring pattern may be cut due to a shift of the snap line. As a result, there is a problem that disconnection occurs or moisture is adsorbed on the cut and exposed internal wiring, causing chemical migration and causing a short circuit. In addition, when the metal casing is provided, there is also a problem that the metal case and the exposed internal wiring come into contact with each other to cause a short circuit.

[0010] In addition, due to the occurrence of the dimensional deviation, the connection between the via-hole conductor in the multilayer circuit board and the wiring pattern becomes insufficient, the electrode position shifts when mounting an IC or the like on the surface of the multilayer circuit board, When the circuit board is mounted secondarily, there is a problem that the reliability of the circuit and each mounting is reduced due to the occurrence of the displacement of the electrode position and the like.

Therefore, the present invention can be applied to the thinning of the insulating film, and can be applied to the production of a multilayer circuit board in which the cut and exposure of the internal wiring at the time of dividing into individual pieces and the accompanying reduction in reliability are suppressed. It is an object of the present invention to provide a multilayer circuit board precursor and a method for manufacturing a multilayer circuit board using the same.

[0012]

According to the present invention, a ceramic insulating film containing a ceramic material and an organic binder is formed on a surface of a resin film, and an internal wiring pattern is formed on the surface of the ceramic insulating film. In the multilayer circuit board precursor having a via-hole conductor penetrating the ceramic insulating film, the maximum thermal shrinkage in the thermal history from the time of forming the insulating film of the resin film to the time of separating the insulating film from the resin film is 0. 0.3% or less.

Further, according to the present invention, a step of forming an insulating film containing a ceramic material and an organic binder on a resin film, forming a through hole in the insulating film, and applying a conductive paste to the through hole. Filling a via-hole conductor, applying a conductive paste to the surface of the insulating film to form a wiring pattern, and forming an insulating film having a via-hole conductor and a wiring pattern on the surface of the insulating film on which the wiring pattern is formed. A step of forming a laminate by laminating films, and a method of manufacturing a multilayer circuit board by separating the laminate from the resin film and firing the laminate, comprising: The maximum heat shrinkage of the resin film in the heat history until the laminate is released from the resin film is controlled to 0.3% or less.

In the above method for producing a multilayer circuit board precursor and a multilayer circuit board, the resin film preferably has a maximum thermal shrinkage of 0.5% or less from room temperature to 150 ° C. In addition, the resin film is bonded to a low heat shrinkable support substrate to restrain the resin film, thereby suppressing shrinkage.

The precursor of the present invention is most suitable when the thickness of the insulating film per layer is 100 μm or less. More preferably, it is 50 μm or less. In the case where there is a step of dividing into individual pieces by dicing, it is preferable to perform the step before separating the insulating film and the resin film.

According to the present invention, the shrinkage ratio of the resin film in the heat history from the time of forming the insulating film of the resin film to the time of separating the insulating film from the resin film is controlled to 0.3% or less. As a result, the dimensional accuracy of the insulating film formed on
It is possible to eliminate the problem that a part of the internal wiring pattern is cut during dicing in the multilayer circuit board and the internal wiring is exposed.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The multilayer circuit board precursor of the present invention comprises:
As a basic structure, as shown in FIG. 1, a ceramic insulating film 2 containing a ceramic material and an organic binder is formed on a resin film 1, and a surface of the insulating film 2 is formed on a surface of a multilayer circuit board. Alternatively, the internal wiring pattern 3 is formed by adhesion. The insulating film 2 is formed by forming a penetrating via-hole conductor 5.

According to the present invention, the maximum thermal shrinkage in the heat history from the time when the insulating film is formed on the surface of the resin film 1 to the time when the insulating film is separated from the resin film in the precursor is 0.3%. It is important to control: That is, if the maximum heat shrinkage ratio is larger than 0.3%, the wiring and via-hole conductors in the multilayer circuit board pieces in the work follow and shrink, resulting in a shift, and the dicing of the internal wiring pattern during dicing. Some of the cuts cause problems such as exposure of internal wiring and poor connection between via-hole conductors.

The maximum heat shrinkage means the maximum shrinkage in the plane of the resin film because the shrinkage in the XY directions of the resin film may be different.

The methods for suppressing the thermal shrinkage of the resin film 1 to 0.3% or less include: 1) forming a film with a resin having a small shrinkage with respect to the thermal history; and 2) reducing the shrinkage of the resin film. And 3) restraining the shrinkage of the resin film so as not to cause heat shrinkage.

FIG. 2 shows the heat shrinkage behavior of commercially available PET films A and B in the method 1). According to this,
Since the thermal shrinkage of PET film A rapidly increases from 80 ° C. or higher, and shrinks by 1% or more at 150 ° C., the shrinkage of this film is suppressed to 0.3% or less unless the applied temperature is lowered. It is very difficult. On the other hand, low heat shrinkage type PET film B
Although the shrinkage rate was reduced to 0.5% in the case of the above, if the maximum temperature in the heat history was set to 150 ° C., it was inevitably 0.1%.
Generates 5% shrinkage. So either improve the heat history or
Or it needs to be combined with other methods.

Therefore, the room temperature of the resin film itself to 150
When the maximum heat shrinkage at 0.5 ° C. is 0.5% or less, heat shrinkage as a precursor can be easily controlled.

In the method 2), the thermal history applied to the resin film is as follows: A) In forming an insulating film, a slurry composed of a ceramic material, an organic binder and a solvent is applied on the resin film, and then dried. Process,
B) A step of drying after printing a wiring layer using a conductive paste on the surface of the insulating film and filling the through-hole with the conductive paste.

Therefore, when a commercially available resin film is used, the shrinkage can be reduced to 0.3% or less by treating the drying steps A) and B) at a temperature of 80 ° C. or less. In order to dry at a temperature of 80 ° C. or lower, the solvent to be mixed in the slurry for forming the insulating film may be a low boiling point solvent, for example, toluene. Then, an organic binder that matches the solvent may be selected. In forming the conductor layer, the organic solvent contained in the paste can be made to have a low volatile point, for example, terpineol.

However, although all of the methods are effective in reducing the content to 0.3% or less, the solvent may not be changed depending on the type of the ceramic material. In some cases, it is necessary to reduce the shrinkage rate. In such a case, the method 3) is effective.

More specifically, as shown in FIG. 1, a resin film 1 is bonded to a support substrate 4 having low heat shrinkage with an adhesive so that the heat shrinkage of the resin film 1 is restrained by the support substrate 4. It is.

As the supporting substrate 4 to be used, it is desirable that the maximum thermal shrinkage in the thermal history from the time of forming the insulating film of the resin film 1 to the time of separating the insulating film from the resin film is 0.05% or less. For example, at least one selected from the group consisting of a glass substrate, a ceramic substrate such as alumina, and a metal plate can be used.

According to the present invention, it can be applied in any case by incorporating one or a combination of two or more of the above 1), 2) and 3), especially at least the method of 3).

A method of manufacturing a multilayer circuit board according to the present invention will be described with reference to FIG. First, a resin film 11 is prepared. As shown in FIG. 3A, the resin film 11 is formed by appropriately selecting the material of the resin film 11 in accordance with the heat history given to the resin film 11 or according to the method 3). It is attached to a predetermined support substrate 12.

Next, a slurry prepared by mixing a ceramic material, an organic binder and a solvent is applied to the surface of the resin film with a predetermined thickness by a doctor blade method or the like, and dried to form an insulating film 13 (b). In particular, in order to reduce the size and height of the multilayer circuit board and make it thinner, the insulating film per layer is applied so that the thickness after drying is 50 μm or less, and the applied film has a maximum thermal shrinkage of the resin film of 0. The insulating film 13 is formed by drying at a temperature not exceeding 3%. The drying temperature is controlled depending on the type of the solvent in the slurry. For example, according to the method 2), toluene is used as the solvent, an acrylic resin is used as the organic binder, and the resin film 11 is dried at 80 ° C. or less. Insulation film 1
3 can be formed.

Next, a through hole serving as a via hole is formed in the insulating film 13, and a conductive paste is filled in the through hole to form a via hole conductor 14 (c). The through holes may be formed using, for example, a YAG laser. In general, the volume of the via-hole conductor 14 is smaller than that of the insulating film 13, so that the via-hole conductor 14 is sufficiently dried even when left naturally.
The drying may be performed when the volume of is increased or when it is desired to reduce the process time. However, it is necessary to consider the drying temperature at this time in the same manner as described above.

Next, the wiring pattern 1 is formed on the surface of the insulating film 13.
5 is printed and applied using a conductive paste by a screen printing method or the like, and dried again (d). The drying temperature at this time is also controlled by the type of the solvent in the paste. For example, if terpineol is used as the solvent according to the method 2), the drying can be performed at 80 ° C. or less. Thereby, a precursor of one layer of the insulating film having the via-hole conductor 14 and the wiring pattern 15 is obtained.

The multilayer circuit board has a structure in which the insulating film 13 having the via hole conductor 14 and the wiring pattern 15 is laminated. In order to manufacture such a structure, the resin film 11 must be formed. By laminating an insulating film having a via-hole conductor and a wiring pattern on the first insulating film 13 formed on the surface in the same manner as above, a laminated body A as shown in FIG. 3E is formed. be able to.

As another laminating method, an insulating film is formed, a via-hole conductor is formed, and a wiring pattern is formed on another resin film surface.
An insulating film 13 having a wiring pattern 15 is formed, and the insulating film 13 is separated from the resin film 11 and laminated and integrated on the already-formed insulating film 11 with an adhesive or the like.
There is also a method in which the resin film 11 is separated after laminating via an adhesive without separating the resin film. In these cases, heating may be performed in order to improve the adhesion, but the temperature may be controlled in accordance with the type of the solvent in the adhesive.

In the formation of the laminate, by providing a positioning reference to the resin film, the reference at the time of lamination can be made the same, so that the lamination accuracy can be improved.

Further, since it is very inefficient to manufacture individual multilayer circuit board pieces on a resin film, a plurality of multilayer circuit board pieces are integrally arranged on the laminate A. Thus, by dividing the laminate A, a multilayer circuit board piece can be manufactured.

As a method of division, for example, division is performed before firing. Specifically, a groove 16 is formed in the laminate A on the resin film 11 to divide the substrate into individual pieces (f).
Since the standard is set by the support substrate 12 and the heat shrinkage of the resin film 11 is small, it is possible to divide the resin film 11 at a time by dicing. If the dicing blade is inserted halfway through the resin film 11 so as not to damage the support substrate 12, the support substrate 12 can be reused and effective.

Next, the laminate A is detached from the resin film 11 (g). If a thermal foaming material is applied to the surface of the resin film 11 in advance in order to release the laminate A from the resin film 11, the laminate A can be easily released by performing a heating treatment at a foaming temperature. Is obtained. Note that even if heat shrinkage occurs due to this heat treatment, the wiring pattern 15 and the via-hole conductor 1 in the laminate A
In No. 4, since the position is fixed, there is almost no occurrence of a position shift or the like.

Thereafter, the substrate piece a is fired at a predetermined temperature, and external electrodes for secondary mounting and the like are formed on the back surface of each circuit board, whereby a multilayer circuit board can be manufactured.

In the above-described division processing, the division processing was performed before firing, but if the division action was performed before firing, a barrel for forming an end face electrode for secondary mounting of the multilayer circuit board was formed. There is an advantage that processing and the like can be easily performed.
Since the chamfering of the multilayer circuit board can be performed by the barrel processing, the bonding strength at the time of secondary mounting can be improved.

In the dividing process, the laminate A may be separated from the resin film 11, fired, and divided after the components are mounted. In this case, there is an advantage that the component mounting efficiency is high because the large substrate can be handled as it is.

[0042]

EXAMPLE A slurry was prepared by mixing a ceramic material obtained by mixing 45 parts by weight of calcium borosilicate glass with 55 parts by weight of alumina as a ceramic material, polymethacrylate as an organic binder, and toluene as a solvent.

On the other hand, the maximum thermal shrinkage from room temperature to 150 ° C. in FIG.
m PET films A and B (both 300 x 3
00 mm) was prepared, and this film was bonded to a glass support substrate having a thickness of 2 mm with an epoxy resin as needed. In Table 1, the room temperature of the resin film itself is shown.
The maximum heat shrinkage up to the insulating film drying temperature is described. In addition,
The maximum thermal shrinkage of this support substrate from room temperature to 150 ° C. is 0%. Further, a thermal foaming material that foams at 140 ° C. was applied to the surface of each resin film.

Then, the slurry was applied on the PET film so as to have an insulating film thickness of 50 μm after drying, and a peak temperature of 65 ° C. and a peak time of 10 minutes shown in Table 1 were used.
Drying was performed at a peak temperature of 130 ° C. for 5 minutes to obtain a ceramic insulating film.

Then, a through hole having a diameter of 150 μm was formed in the insulating film by laser light, and the through hole was filled with a silver paste. In addition, a wiring pattern was printed and applied to the surface of the insulating film with a silver paste by a screen printing method. The silver paste was obtained by adding borosilicate glass frit to silver powder. Terpineol or butyl carbitol acetate was used as a solvent, and ethyl cellulose was used as an organic binder. The printed film thickness of the wiring is 1 after drying.
It was adjusted to be 00 μm. In addition, the positioning of the wiring pattern by the screen printing method was based on the outer side of the support substrate. The drying of the wiring pattern after screen printing is performed at a peak temperature of 65 ° C. in the case of using terpineol, and a peak temperature of 130 ° C. in the case of butyl carbitol acetate.
All were performed with a peak time of 20 minutes.

Thereafter, the application and drying of the insulating film, the formation of via-hole conductors, the application of a wiring pattern and the drying were repeated to obtain a laminate of 16 insulating films.

Next, a dicing blade was inserted halfway through the resin film by dicing to divide the laminate into individual substrate pieces. The dimensions of the resin film at this point were measured, and the maximum shrinkage relative to the initial dimensions of the resin film is shown in Table 1. Further, the divided laminate was subjected to a heat treatment at a peak temperature of 160 ° C. and a peak time of 10 minutes to release the resin film to obtain individual multilayer circuit board pieces.

Thereafter, each substrate piece was heated to a peak temperature of 900 ° C.
And a silver paste was applied as an external electrode, and baked at a peak temperature of 850 ° C. to obtain a multilayer circuit board.

For the manufactured multilayer circuit board, 121
The temperature was maintained at 2 ° C. and 2 atm for 24 hours, and a defective circuit was determined as a defective due to a circuit failure due to a positional displacement of the wiring or via-hole conductor and a short circuit caused by migration due to the exposure of the wiring.

[0050]

[Table 1]

As is clear from the results shown in Table 1, a multilayer circuit board having a high yield rate can be manufactured by setting the heat shrinkage in the heat history of the resin film to 0.3% or less.

[0052]

As described in detail above, the multilayer circuit board precursor of the present invention forms an insulating film on the surface of the resin film until the insulating film is separated from the resin film,
By setting the maximum thermal shrinkage of the resin film in the heat history until the laminated body formed with the wiring is released from the insulating film to 0.3% or less, the dimensional accuracy and positional accuracy of the internal wiring pattern and the via hole conductor can be improved. It is possible to obtain a high-yield multilayer circuit board in which the problems such as the circuit failure, the cut and the exposure of the wiring at the time of dicing, and the resulting reduction in reliability are solved.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view for explaining a basic structure of a multilayer circuit board precursor according to the present invention.

FIG. 2 is a graph showing the maximum heat shrinkage of a PET film.

FIG. 3 is a process diagram illustrating a method for manufacturing a multilayer circuit board according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 resin film 2 ceramic insulating film 3 wiring pattern 4 support substrate 5 via hole conductor 11 resin film 12 support substrate 13 insulating film 14 via hole conductor 15 wiring pattern 16 dicing groove A laminated body a substrate piece

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G055 AA08 AC09 BA83 BB01 5E346 AA12 AA15 AA32 AA43 CC02 CC17 CC39 DD03 DD13 DD34 EE23 EE24 EE29 FF01 FF05 GG03 GG04 GG06 GG07 GG08 GG09 GG15 GG19 HH33

Claims (8)

[Claims] 1. A ceramic insulating film containing a ceramic material and an organic binder on a surface of a resin film, and an internal wiring pattern formed on the surface of the ceramic insulating film, and a via hole penetrating the ceramic insulating film. In the multilayer circuit board precursor having a conductor, the maximum heat shrinkage in the heat history from the time of the formation of the insulating film of the resin film to the time the insulating film is separated from the resin film is 0.3% or less. Characteristic multilayer circuit board precursor. 2. The multilayer circuit board precursor according to claim 1, wherein the resin film has a maximum heat shrinkage of 0.5% or less from room temperature to 150 ° C. 3. The multilayer circuit board precursor according to claim 1, wherein the resin film is adhered to a low heat shrinkable support substrate. 4. The multilayer circuit board precursor according to claim 1, wherein the thickness of the insulating film per layer is 100 μm or less. 5. A step of forming an insulating film containing a ceramic material and an organic binder on a resin film, forming a through hole in the insulating film, filling the through hole with a conductive paste to form a via hole conductor. Forming, applying and forming a conductive paste on a wiring pattern on the surface of the insulating film, and laminating and laminating an insulating film having a via-hole conductor and a wiring pattern on the surface of the insulating film on which the wiring pattern is formed. Forming a body, and removing the laminate from the resin film, and baking the laminate to produce a multilayer circuit board, wherein the step of forming an insulating film on the resin film includes removing the laminate from the resin film. Wherein the maximum thermal shrinkage of the resin film in the heat history until the resin film is separated from the substrate is controlled to 0.3% or less. 6. The method for manufacturing a multilayer circuit board according to claim 5, wherein the maximum thermal shrinkage of said resin film from room temperature to 150 ° C. is 0.5% or less. 7. The method according to claim 5, wherein the thickness of the insulating film per layer is 100 μm or less. 8. The method according to claim 5, further comprising a step of dividing the laminate together with the resin film into individual multilayer circuit boards by dicing before separating the laminate from the resin film. 8. The method for manufacturing a multilayer circuit board according to any one of items 7.