JPH1174641A - Multilayer wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance adhesion between an insulation film or a wiring circuit film formed by build-up method and a wiring board forming a core by admixing the insulation layer of the wiring board forming a core with a resin having a significant difference in the molecular weight and/or the curing point. SOLUTION: A wiring board comprising an insulation layer 2 composed of at least two kinds of resin having a significant difference in the molecular weight and/or the curing point, and a wiring circuit layer 3 forms a core 4 onto which an insulation film 5 and a wiring circuit film 6 are formed sequentially by build-up method thus producing a multilayer wiring board 1. The resin having a significant difference in the molecular weight and/or the curing point includes thermosetting resins, e.g. polyphenylene ether or bismaleimide triazine, epoxy resin, polyimide resin, fluororesin or phenol resin, and thermoplastic resins and imide based resins excellent in heat resistance moisture absorbance and electric characteristics in high frequency region is most suitable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer wiring board suitable for various multilayer wiring boards and packages for housing semiconductor elements, and more particularly to a multilayer wiring board formed by a build-up method.

[0002]

2. Description of the Related Art In recent years, there has been a remarkable increase in the performance and miniaturization of electronic devices. Due to the development of portable information terminals and the spread of so-called mobile computing in which computers are carried and operated, such electronic devices have become increasingly popular. The multilayer wiring board used is required to be further reduced in size, thickness, and definition.

On the other hand, in electronic equipment such as communication equipment which requires high-speed operation, a multilayer wiring satisfying a requirement that accurate switching can be performed for a high frequency signal with the spread of the electronic equipment. There is a need for a substrate.

In order to meet such demands, it is necessary to increase the wiring density of the multilayer wiring board.
The conventional copper-clad laminates are drilled using a drill to form via-hole conductors and wiring patterns, and then laminated to form a multilayer printed wiring board. However, there is a limit to the reliability of a through hole having a high aspect ratio due to the increase in the manufacturing cost, and an increase in manufacturing cost due to the formation of a thin insulating layer.

Therefore, as one means for solving the above-mentioned drawbacks and increasing the wiring density and reducing the manufacturing cost, a process of alternately forming a wiring circuit film and an insulating film on an insulating substrate is repeated to form a multilayer. A build-up method for manufacturing a wiring board is known.

In such a build-up method, for example, a double-sided copper-clad glass epoxy substrate having a wiring circuit layer formed by etching a copper foil is used as a core, and a photosensitive epoxy resin is applied to the surface of the double-sided copper-clad glass epoxy substrate. Then, after exposing and developing and exposing the photosensitive epoxy resin in a portion for forming a via hole, a copper coating layer is formed on the obtained insulating film by an electroless plating method or an electrolytic plating method, and the coating layer is formed. Is etched to form via-hole conductors and wiring circuit films.

Next, the formation of the insulating film by the photosensitive epoxy resin and the formation of the via-hole conductor and the wiring circuit film by the copper coating layer are repeated to form a multilayer, and further, a through hole for a through hole is provided by a drill or the like. A multi-layer wiring board is formed by forming a plating layer in the through hole and electrically connecting the wiring circuit films between the layers (Japanese Patent Application Laid-Open No. Hei 9 (1994)).
-64514).

[0008]

However, with the spread of the build-up method, the following problems have become apparent.

In other words, the multilayer wiring board formed by the build-up method has poor adhesion between the insulating layer forming the double-sided copper-clad glass epoxy substrate or the like of the core and the insulating film or wiring circuit film formed by the build-up method. There is a problem, particularly in the case where the core is an insulating substrate formed by impregnating a resin into an aramid nonwoven fabric, since the thermal expansion coefficient of the insulating substrate is low, the difference in thermal expansion from the resin forming the insulating film formed on the surface thereof is low. There is a problem that the insulating film and the wiring circuit film formed by the build-up method are easily peeled off.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to improve the adhesion between an insulating film or a wiring circuit film formed by a build-up method and a wiring substrate forming a core. It is an object of the present invention to provide a multilayer wiring board which realizes a high-density wiring, which is optimal as a wiring board for information and communication fields, particularly for mobile computing related devices.

[0011]

Means for Solving the Problems The present inventor has made intensive studies in view of the above problems, and as a result, has found that a resin having a large difference in molecular weight and / or curing temperature is mixed and used in an insulating layer of a wiring substrate forming a core. When hardening, the surface produces minute projections, and it is found that if an insulating film or a wiring circuit film is formed on this insulating layer surface by a build-up method, the adhesion is improved,
The present invention has been reached.

That is, the multilayer wiring board of the present invention is a wiring board comprising an insulating layer made of at least two kinds of resins having different molecular weights and / or curing temperatures and having a surface roughness of 0.1 μm or more, and a wiring circuit layer. , And an insulating film and a wiring circuit film are sequentially formed on the surface of the core by a build-up method. In particular, more preferably, the resin has a molecular weight of 5 times or more and / or Or the curing temperature is 1
0 ° C. or more, the insulating layer constituting the core contains 10 to 50% by volume of ceramic powder having an average particle size of 0.2 to 10 μm, and the wiring substrate of the core has at least The wiring conductor layer formed on the surface is obtained by transferring the wiring conductor layer formed on a resin film.

[0013]

According to the multilayer wiring board of the present invention, the molecular weight and / or
Alternatively, since the insulating layer is formed of at least two kinds of resins having different curing temperatures, in the uncured state of the resin, a so-called sea-island in which a high-molecular component and a low-molecular component are distributed in a sea-like and island-like shape depending on the content thereof. When the resin is maintained at the first curing temperature, curing of some components starts, the resin becomes a mixture of a partially cured resin and an uncured resin, and this mixture is further divided into a first composition and a second composition. When the resin is kept at the second curing temperature, the curing of the uncured resin starts, and at this time, the first cured resin rises to the surface by being pressed by the resin component to be cured, and irregularities are formed on the surface become.

Such an effect becomes more remarkable when a ceramic powder is mixed with the resin, and as a result, an insulating film made of a photosensitive resin in which irregularities on the resin surface are formed by a build-up method, or a conductive layer formed by plating. It is effective for improving the adhesive strength, particularly for improving the adhesive strength of fine wiring of 50 μm or less.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the multilayer wiring board of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the multilayer wiring board of the present invention. In the drawing, reference numeral 1 denotes a wiring board composed of an insulating layer 2 made of at least two kinds of resins and a wiring circuit layer 3 as a core 4, and an insulating film 5 and a wiring circuit formed on a surface of the wiring board forming the core 4 by a build-up method. This is a multilayer wiring board formed by sequentially laminating films 6.

In the present invention, the resins having different molecular weights and / or curing temperatures include, for example, polyphenylene ether (PPE), bismaleimide triazine (BT resin), epoxy resin, polyimide resin, fluororesin,
A thermosetting resin such as a phenol resin or a thermoplastic resin can be used. In particular, an imide-based resin is optimal in terms of excellent heat resistance, low hygroscopicity, and excellent electric characteristics in a high frequency range.

If the difference in the molecular weight of the above resins is less than five times if only the molecular weight is discussed, the deformation of each resin at the time of curing proceeds with substantially the same amount. In some cases, it is difficult to form the projections as described above. If the surface roughness does not exceed 0.1 μm,
The curing temperature may be varied, or ceramic powder such as SiO ₂ powder may be appropriately added.

In the present invention, if the surface roughness of the insulating layer of the core is less than 0.1 μm, the build-up layer such as an insulating film and a wiring circuit film formed on the surface is easily peeled off by repeated heating and cooling. The higher the surface roughness is, the higher the adhesion of the build-up layer is. However, if the surface is too rough, air bubbles easily enter between the build-up layer and the resin for the insulating film, thereby affecting the adhesion. Therefore, the surface roughness is more preferably about 0.5 to 3 μm in Ra.

It is also effective to use a mixture of resins having different molecular weights in order to increase the surface roughness. This is because the mixed resins move and cure while moving. is there.

However, if the difference in molecular weight exceeds 500 times, uniform mixing of the resins becomes difficult, and long-term mechanical mixing is required.

Therefore, the difference in the molecular weight of the resin in the present invention is preferably about 5 to 500 times, particularly preferably 10 to 500 times, and more preferably 50 to 100 times in order to stably obtain the required surface roughness. It will be optimal.

Next, when the difference between the curing temperatures of the resins is less than 10 ° C., the curing of each resin proceeds almost simultaneously. Therefore, if the molecular weight is not changed or the ceramic powder is not mixed, the above-mentioned surface is hardened. Are not formed, and the surface roughness does not exceed 0.1 μm.

Conversely, if the difference between the curing temperatures exceeds 100 ° C., the difference between the curing temperatures becomes too large, and the resin having a low curing temperature may crack or decompose during the curing of the resin having a high curing temperature. There is.

Therefore, the difference in the curing temperature of the resin in the present invention is desirably 10 to 100 ° C., and particularly, from the viewpoint of preventing deformation of the insulating substrate made of such a resin and segregation of the resin.
-100 ° C is desirable, and more preferably 30-60 ° C.

It is preferable that the resin is cured at each curing temperature for at least 5 minutes so that the respective resins are cured efficiently.

Further, the mixing of resins having different molecular weights and the mixing of resins having different curing temperatures are effective even when used alone, but may cause difficulties in the production process such as inferior handleability of the resin alone. It is more effective to provide a difference between the molecular weight and the curing temperature.

As a result, by mixing at least two kinds of resins having a large difference in molecular weight and / or curing temperature, fine projections are formed on the surface during curing, and the photosensitive resin is formed on the surface having the projections. When copper foil with resin is adhered, the resin adheres firmly to the surface by the anchor effect, and the connection between the core wiring board and the insulating film or wiring circuit film formed by the build-up method is strengthened, improving reliability. be able to.

In the present invention, the insulating layer constituting the core wiring board has a molecular weight of 5 times or more and / or a curing temperature of 10 ° C.
It is important that the surface roughness is 0.1 μm or more by using a mixture of at least two different resins.

On the other hand, in the insulating layer of the core of the present invention, an inorganic filler may be compounded with the organic resin, and the inorganic filler may be silica (SiO ₂ ),
Alumina (Al ₂ O ₃ ), aluminum nitride (Al
N), silicon carbide (SiC) and the like can be used. The ceramic powder has an average particle size of 0. 0 to prevent disconnection of the wiring circuit film due to coarse particles. The thickness is more preferably 2 to 10 μm, and the content thereof is more preferably in the range of 10 to 50% by volume.

Further, as a material to be combined with the organic resin, a glass cloth or a sheet (prepreg) in which an aramid nonwoven fabric is impregnated with a resin may be used, and the aramid nonwoven fabric is impregnated with a resin such as a thermosetting resin. A wiring circuit is formed by filling a conductive paste into a via hole in an uncured state or a semi-cured state (B stage) of an impregnated resin and transferring the via hole conductor from a transfer sheet in which a wiring circuit layer made of a metal foil is formed. A layer can also be formed. When the aramid nonwoven fabric is contained in the insulating substrate, the strength of the insulating layer or the entire wiring substrate can be increased.

Further, when the wiring circuit layer on the surface of the core wiring board is formed by a transfer method, the wiring circuit layer is embedded in the wiring board surface, so that there is no protrusion corresponding to the thickness of the copper foil, and the build-up layer is formed. A good multilayer wiring board can be obtained without bubbles or the like during formation.

Next, a method for manufacturing the multilayer wiring board of the present invention will be described.

First, through holes are formed at predetermined positions in an insulating layer containing at least two kinds of organic resins. The through holes are formed by punching, laser or the like on the uncured (B-stage) insulating layer. Formed by
The diameter of the through hole is appropriately selected depending on the wiring circuit.
It is formed with a diameter of 00 to 200 μm.

Next, a metal paste is filled in the through-hole and dried to form a through-hole conductor.

The metal paste is composed of a metal powder, an organic resin and a solvent, and the metal powder is at least one selected from copper (Cu), aluminum (Al), gold (Au), silver (Ag) or a mixture thereof. It is desirable to constitute with the alloy of.

On the other hand, as the organic resin in the metal paste, a resin such as cellulose can be used in addition to the above-described thermosetting resin, and any solvent can be used as long as the organic resin used can be dissolved. For example, isopropyl alcohol, terpineol, 2-octanol, butyl carbitol acetate (BCA) and the like can be mentioned.

Next, a wiring circuit layer made of metal foil is formed on at least one exposed end of the insulating layer of the through-hole conductor.

The wiring circuit layer made of the metal foil can be formed by a known method. For example, after a metal foil such as copper is adhered to the surface of the insulating layer, a resist is applied to the wiring pattern to form a non-resist formation. After the portions are removed by etching, a method of removing the remaining resist, a method of forming a wiring pattern on the transfer sheet to which the copper foil is adhered in the same manner as described above, and transferring the wiring pattern to the insulating layer, and the like are employed. obtain.

Then, a pressure is applied between the wiring circuit layers formed at both ends of the through-hole conductor to embed the wiring circuit layer in the insulating layer and, at the same time, pressurize and compress the through-hole conductor. The pressure to be applied is preferably from 1 to 200 kg / cm ² , more preferably from 20 to 70 kg / cm ² , from the viewpoint of adhesion and removing bubbles at the interface.

When the wiring circuit layer is formed by transferring the wiring circuit layer to the insulating layer, a pressure is applied to transfer only the wiring circuit layer to the insulating layer, and then the laminating pressure is reduced by using a device such as a vacuum press. It is set to 20-60 kg / cm ² and laminated and crimped.
In the lamination and pressure bonding, the resin may be heated in a range not higher than the curing temperature of the resin.

After lamination and pressure bonding, the resin is taken out of the vacuum press and cured to form the insulating layer. The maximum holding temperature during curing is generally 150 to 170 ° C. when the resin is an epoxy resin. 170-200 ° C for bismaleimide triazine resin, 200-350 for imide resin
° C, and is maintained for about 30 minutes to 3 hours at each temperature depending on the curing temperature of the contained resin.

Through the above steps, the wiring substrate constituting the core of the present invention is completed.

Incidentally, the wiring substrate may be provided with irregularities on the surface conductor, if desired. For this purpose, an etching solution containing at least sulfuric acid or hydrochloric acid and, if desired, hydrogen peroxide is applied to the wiring substrate. It is sufficient to spray and selectively etch the grain boundaries of the conductive metal.

This makes it possible to roughen the surface of the wiring circuit layer by etching to a surface roughness of 0.1 μm or more and to make the surface of the wiring circuit layer depressed by 0.1 μm or more from the resin surface forming the insulating layer of the wiring board. Accordingly, it is possible to eliminate the peeling of the core and the wiring substrate from the insulating film or the wiring circuit film formed by the build-up method.

Thereafter, an insulating film and a wiring circuit film are formed on the wiring substrate surface of the core by a build-up method. A known method can be used for the formation. For example, when a photosensitive epoxy resin is used, After the insulating film is formed, the photosensitive epoxy resin at the portion where the via hole is to be formed is exposed, developed and removed, and a copper coating layer is formed on the insulating film by electroless plating or electrolytic plating to form the via hole. The wiring circuit film may be formed by providing a conductor and etching the formed copper coating layer.

In addition, both the subtractive method and the additive method can be applied to the formation of the wiring circuit film.
In the case of forming by laminating copper foil with resin, after bonding the copper foil with resin to the wiring board of the core with a vacuum laminating machine,
The wiring circuit is exposed and developed with a photoresist, and a via hole is formed with a laser, and then the via hole is conducted by plating.

Here, when laminating the copper foil with resin, the depression of the wiring circuit layer of the wiring board of the core is 3 μm so that no air remains between the copper foil with resin and the wiring board of the core. It is better to do the following.

Thus, the multilayer wiring board of the present invention can be obtained.

[0050]

EXAMPLES The multilayer wiring board of the present invention was evaluated as follows.

First, as an insulating layer constituting the core, Table 1
The main component is a low-molecular-weight imide resin having a molecular weight and a curing temperature as shown in (1), a high-molecular-weight polymer component as an auxiliary component, and a ceramic powder having an average particle size of 2 if desired.
A predetermined amount of μm silica (SiO ₂ ) powder was blended, an organic solvent was added and mixed, and a green sheet was formed by a doctor blade method.

[0052]

[Table 1]

Next, a via hole having a diameter of 0.1 mm was formed in the obtained green sheet by a carbon dioxide laser, and the via hole was filled with a copper paste made of copper powder plated with silver having a particle size of about 5 μm. .

On the other hand, polyethylene terephthalate (PE)
T) An adhesive was applied to the surface of a transfer sheet made of a resin to impart tackiness, a copper foil having a thickness of 18 μm was adhered to one surface, and then a photoresist (dry film) was applied and exposed and developed. Thereafter, this was immersed in a ferric chloride solution to remove the non-pattern portion by etching, thereby forming a wiring circuit having a line width of 40 μm and an interval between the wirings of 40 μm.

Then, the transfer sheet having the wiring circuit formed thereon was positioned and brought into close contact with the green sheet, and only the transfer sheet was peeled off to transfer the wiring circuit to the surface of the green sheet.

Also, in the same manner as described above, each layer necessary for fabricating the core wiring board is formed,
After press-bonding at a pressure of g / cm ² , heating was performed at a temperature of 140 ° C. for 1 hour to partially cure, and subsequently, heating was performed at a temperature of 200 ° C. for 1 hour to completely cure to produce a core wiring substrate.

The surface roughness of the insulating layer on the surface of the wiring board thus obtained was measured.

Subsequently, a photosensitive epoxy resin is applied to the surface of the wiring substrate by a spin coating method, and then heated at a predetermined temperature to form an insulating film, and a portion of the photosensitive epoxy resin where a via hole is to be formed is exposed. , Developed and removed.

Thereafter, a copper coating layer was formed on the surface of the insulating film and the inside of the via hole by an electroless plating method or an electrolytic plating method, and the wiring circuit film and the via hole conductor were formed by etching the copper coating layer. .

After the same steps are repeated to form an insulating film of a predetermined photosensitive resin and a build-up layer composed of a wiring circuit film and a via-hole conductor, a solder made of epoxy resin for protecting the wiring circuit film is formed. A multilayer wiring board for evaluation was prepared by providing a resist.

With respect to the multilayer wiring board for evaluation thus obtained, a metal fitting is attached to the copper wiring of the build-up layer, the force required for peeling off the copper wiring is measured, and the adhesion strength of the wiring is determined. The sex was evaluated.

On the other hand, the multilayer wiring board for evaluation was -60
A heat cycle test was performed 200 times at a temperature of 150 ° C. and a temperature of + 150 ° C., and the presence or absence of defects such as peeling or cracking of the build-up layer after the test was confirmed.

The multilayer wiring board for evaluation was cut, and
Observation of the vicinity of the formation of the wiring circuit film and the via-hole conductor in the cross section revealed that neither deformation of the wiring substrate of the core, connection failure of the wiring circuit film, the via-hole conductor, or disconnection of the wiring was found. .

Further, the multilayer wiring board for evaluation was subjected to a humidity of 8
After being left for 100 hours in a high-temperature and high-humidity atmosphere of 5% and a temperature of 85 ° C., the multilayer wiring board of the present invention did not show any change that could be visually discriminated. Peeling was observed, but it was confirmed that there was no effect on operation.

[0065]

[Table 2]

As is clear from the table, the surface roughness of Sample Nos. 1, 5, and 14, which are out of the claims of the present invention, is 0.07.
μm or less, the adhesive strength of the build-up layer is weak, and all of them are peeled off or cracked in the heat cycle test, whereas in the present invention, the adhesive strength is improved in any of the heat cycle tests. However, it was confirmed that no defect occurred.

[0067]

As described above in detail, in the present invention, the insulating layer of the wiring board which forms the core of the multilayer wiring board manufactured by the build-up method is made of at least two kinds of resins having different molecular weights and / or curing temperatures. As a result, the adhesion between the insulating film and wiring circuit film formed by the build-up method and the insulating layer of the wiring substrate that forms the core is improved, making it ideal for use in the information and communication field, especially as a wiring substrate for mobile computing-related equipment. In addition, it is possible to obtain a multilayer wiring board that realizes higher density wiring and lower cost.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a multilayer wiring board of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Multilayer wiring board 2 Insulating layer 3 Wiring circuit layer 4 Core 5 Insulating film 6 Wiring circuit film

Claims (4)

[Claims] 1. A wiring substrate comprising an insulating layer made of at least two kinds of resins having different molecular weights and / or curing temperatures, and a wiring circuit layer, wherein the insulating layer has a surface roughness of 0.1 μm or more. A multilayer wiring board comprising an insulating film and a wiring circuit film sequentially laminated on the surface of the wiring board. 2. The multilayer wiring board according to claim 1, wherein the molecular weight of the resin is at least 5 times and / or the curing temperature is different by at least 10 ° C. 3. The core according to claim 2, wherein the insulating layer comprises 0.2 to 10%.
3. The multilayer wiring board according to claim 1, comprising 10 to 50% by volume of a ceramic powder having an average particle size of [mu] m. 4. The multilayer wiring board according to claim 1, wherein the wiring circuit layer on at least the surface of the wiring board is formed by transferring a wiring conductor layer formed on a resin film.