JP3199637B2 - Method for manufacturing multilayer wiring 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 for manufacturing a multilayer wiring board suitable for, for example, a multilayer wiring board and a package for accommodating a semiconductor element.

[0002]

2. Description of the Related Art Conventionally, a multilayer ceramic wiring board capable of relatively high-density wiring has been frequently used as a wiring board, for example, a multilayer wiring board used for a package for housing a semiconductor element. This multilayer ceramic wiring board
It is composed of an insulating substrate such as alumina and a wiring conductor made of a high melting point metal such as W or Mo formed on the surface thereof. A cavity is formed in a part of the insulating substrate,
The semiconductor element is accommodated in the cavity, and the cavity is hermetically sealed by the lid.

However, the ceramics constituting such a ceramic multilayer wiring board are hard and brittle, so that chipping or cracking of the ceramics is liable to occur in a manufacturing process or a transporting process. There is a problem that yield is low because stopping performance may be impaired. In addition, the metallized ink is printed on the green sheet before sintering, and the printed sheet is laminated and sintered.In the manufacturing process, firing at a high temperature causes firing shrinkage. There is a problem that deformation such as warpage and dimensional variation are likely to occur in the obtained substrate, and it sufficiently responds to strict requirements for ultra-high density circuit boards and flatness of substrates such as flip chips etc. There was a problem that it was not possible.

Therefore, recently, a copper foil is adhered to the surface of an insulating substrate containing an organic resin, and is then etched to form a fine conductor circuit. Multilayer printed wiring boards have been proposed. In addition, in order to increase the strength of such a multilayer wiring printed board, a board in which a spherical or fibrous inorganic filler is dispersed in an organic resin has been proposed. Application to a multi-chip module (MCM) in which a large number of semiconductor elements are mounted on a substrate is also being studied.

According to the method for manufacturing a multilayer printed wiring board, a conductor circuit having a thickness corresponding to the thickness of a copper foil is formed on the surface of an insulating substrate containing an organic resin. When a multilayer printed circuit board is formed by laminating a plurality of printed circuit boards, the multilayer printed circuit board has different thicknesses between the conductor circuit forming portion and the non-forming portion, and the surface thereof is uneven. Therefore, when the insulating substrate containing the organic resin itself is given some plasticity, and when a plurality of insulating substrates are laminated and pressed to form a multilayer printed wiring board, a portion of the insulating substrate that comes into contact with a conductor circuit is formed. The conductor circuit is buried in the insulating substrate by plastically deforming according to the thickness of the conductor circuit, so that no irregularities are formed on the surface of the multilayer printed wiring board.

[0006]

Recently, there has been a demand for a multilayer wiring board having a finer conductive circuit than in the prior art. When manufactured by the conventional method, as shown in FIG. 2, the concave portion existing between the circuits of the conductor circuit 12 having a predetermined thickness formed on the surface of the insulating substrate 11 has a slightly plastic insulating layer laminated thereon. The plastic substrate 11 cannot be completely filled only by plastic deformation at the time of lamination and pressure bonding, and a void 13 is formed around the conductor circuit 12 in the finally obtained multilayer printed wiring board, and moisture and the like enter the void 13. Then, the insulation between the conductor circuits 22 deteriorates, and a short circuit occurs in the circuit, or the conductor circuit 12 is corroded. Moreover, if the insulating substrate cannot be sufficiently plastically deformed in accordance with the thickness of the conductor circuit during lamination and compression, the circuit formed in the upper layer is also deformed. In the case of crossing, the deformation of the upper-layer conductor circuit becomes large, and the circuit may be disconnected.

For this reason, when manufacturing a multilayer printed wiring board, the thickness of each insulating substrate is made sufficiently large so that the influence of the lower conductive circuit does not affect the upper conductive circuit, or Although measures have been taken to avoid crossover, the wiring density of the conductor circuit has been reduced, and problems have arisen, such as an increase in the volume of the entire multilayer printed wiring board.

Further, the plasticity of each insulating substrate is made extremely large, whereby each insulating substrate can be sufficiently plastically deformed with respect to the thickness of the conductor circuit when each insulating substrate is laminated under pressure. It is possible to prevent the formation of voids between the insulating substrates and to prevent the surface of the multilayer printed wiring board from becoming uneven, but in this case,
When the plasticity is large, the bonding between the organic resins forming the insulating substrate becomes extremely weak, and when the copper foil adhered to the insulating substrate is etched to form a conductor circuit, the insulating property is increased by an etchant. The substrate is greatly eroded, causing a disadvantage that a predetermined multilayer printed wiring board cannot be obtained.

As the method of mounting a silicon chip on a wiring substrate changes from the wire bonding method to the flip chip method, the required value of the flatness of the substrate surface is becoming stricter. In this case, unevenness due to the conductor circuit sometimes becomes a fatal defect, and even mounting of a silicon chip may not be possible. It is considered that the ultra-fineness of such a circuit will be further advanced, and there is a need for the completion of a technology for manufacturing an ultra-fine multilayer wiring board that can meet those requirements.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in response to the above-mentioned demand for ultra-fine circuits, and eliminates unevenness caused by conductor circuits formed on each substrate of a multilayer wiring board. It is another object of the present invention to provide a method for manufacturing a multilayer wiring board in which no gap is generated between the substrates.

[0011]

According to a method of manufacturing a wiring board of the present invention, a transfer sheet having a conductive circuit made of metal on a surface thereof, at least a thermosetting organic resin, a hemispherical tip and a diameter of 300 μm are provided. A step of preparing a semi-cured insulating layer having a needle penetration depth of 30 μm or more at room temperature when the needle is penetrated by a force of 100 gf, and a step of preparing a semi-cured state with the conductor circuit formed on the transfer sheet. 30-1 with insulating layer
A step of press-contacting the conductor circuit into the insulating layer at a temperature of 30 ° C. at a pressure of 10 kgf / cm ² or more, and removing the transfer sheet from the insulating layer in which the conductor circuit is transferred and embedded; A step of obtaining a circuit board in which a conductor circuit is embedded, and a step of laminating a plurality of the circuit boards, and then heating and completely curing the circuit board. Since the conductive circuit is formed on the surface of the insulating layer by pressing the formed conductive circuit against the semi-cured insulating layer, it is not necessary to form the conductive circuit by etching on the semi-cured insulating layer, In addition, the semi-cured insulating layer is made to have extremely high plasticity, so that the conductor circuit can be easily and sufficiently embedded in the insulating layer.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to FIG. FIG. 1 is a cross-sectional view for explaining a method of manufacturing a multilayer wiring board according to the present invention.

According to the method for manufacturing a multilayer wiring board of the present invention, first, as shown in FIG.
Is prepared, and a semi-cured insulating layer 3 containing at least an organic resin is prepared.

The conductor circuit 2 formed on the surface of the transfer sheet 1 is preferably made of at least one or two or more alloys selected from the group consisting of copper, aluminum, gold and silver. Or an alloy containing copper is most desirable. In some cases, Ni may be used to adjust the resistance of the circuit.
A high resistance metal such as a Cr alloy may be mixed or alloyed.

The conductive circuit 2 can be formed by etching or laser processing a desired metal foil, or by plating. For example, in the etching method, after a metal foil made of the above-described conductor circuit forming metal is adhered to the entire surface of the transfer sheet 1, a photoresist is formed on the metal foil by a method such as screen printing to form a resist in a conductor circuit shape. Then, unnecessary conductor portions 2 are obtained by removing unnecessary portions by etching.

At this time, the resist generally requires a step of removing unnecessary portions of the metal foil by etching and then removing the resist with a resist removing solution or the like, and washing the resist. The resist is made of the same material as the insulating layer 3 described later. If an insulating material containing an organic resin, for example, an organic resin and an inorganic filler is used, there is no need to remove the resist, which is advantageous in that the process can be simplified.

On the other hand, the insulating layer 3 is made of an insulating material containing at least an organic resin and is in a semi-cured state. Examples of the organic resin include PPE (polyphenylene ether) and BT resin (bismaleimide triazine). , An epoxy resin, a polyimide resin, a fluororesin, a phenolic resin, and the like are desirable, and a thermosetting resin that is liquid at room temperature as a raw material is particularly desirable.

In the insulating layer 3, it is desirable to compound an inorganic filler with an organic resin in order to increase the strength of the insulating layer 3 or the entire wiring board.
As the inorganic filler compounded with the organic resin, Si
O ₂ , Al ₂ O ₃ , ZrO ₂ , TiO ₂ , AlN, Si
C, BaTiO ₃ , SrTiO ₃ , zeolite, CaT
Known materials such as iO ₃ and aluminum borate can be used. The filler has an average particle size of 20 μm or less, particularly 1 μm.
In addition to substantially spherical powder having a particle size of 0 μm or less, optimally 7 μm or less, a fibrous material having an average aspect ratio of 2 or more, particularly 5 or more, or a woven fabric can be used.

In the composite material of an organic resin and an inorganic filler, it is appropriate that the organic resin and the inorganic filler are compounded in a volume ratio of 15:85 to 50:50.

Next, as shown in FIG. 1 (b), the transfer sheet 1 having the conductor circuit 2 formed on the upper surface and the insulating layer 3 are overlapped, and these are pressed from above and below using a conventionally known press device. Then, the conductor circuit 2 is transferred and embedded in the insulating layer 3.

At this time, the insulation layer 3 has a needle penetration depth of 10 μm or more, preferably 30 μm or more when a needle having a hemispherical tip and a diameter of 300 μm is penetrated by a force of 100 gf.
Optimally, it has a softness of 50 μm or more, and if the needle penetration depth is less than 10 μm, the conductor circuit 2
In the insulating layer 3 becomes difficult.

The insulating layer 3 has a needle penetration depth of 10
In order to achieve the softness of not less than μm, a method of including an appropriate amount of a solvent or a plasticizer in the insulating layer 3 or a method of heating and softening the insulating layer 3 can be adopted.

The pressing pressure at this time is 10 kgf / c
m ² or more. When the pressing pressure is 10
In the case of less than kgf / cm ² , the circuit conductor 2 is
It is difficult to bury them sufficiently. The temperature at the time of pressure contact is preferably 30 to 130 ° C. This temperature is 30 ° C
If it is lower, the hardness of the insulating layer 3 is high and the conductor circuit 2 may not be sufficiently embedded.
Of the conductive circuit 2 may be covered with a resin, and the reliability of connection with the conductive ink filled in via holes provided in a circuit board, which will be described later, may be reduced.

As described above, the conductor circuit 2 is provided in the insulating layer 3.
After embedding, the transfer sheet 1 is peeled from the insulating layer 3 so that the surface of the conductor circuit 2 and the surface of the insulating layer 3 are excellent in smoothness as shown in FIG. Thus, a single-layer circuit board 4 can be manufactured.

Then, a plurality of circuit boards are manufactured as shown in FIGS. 1A to 1C, and via holes are formed by a punching method or a method using a laser if desired, and a conductive resin or a metal filler is added. The via holes are filled with conductive ink or the like. Then, the obtained circuit board 4 is shown in FIG.
As shown in (d), a desired number of sheets can be laminated at a predetermined position, closely adhered by pressing or heating, and integrated to produce a multilayer wiring board.

In such an embodiment, the surface of the conductor circuit 2 formed on the surface of the transfer sheet 1 serves as an interface with the insulating layer 3, and is a factor that determines the adhesion of the conductor circuit 2 to the insulating layer 3. is there. From this point of view, the insulating layer 3 of the conductor circuit 2
The metal foil formed on the surface of the transfer sheet 1, in other words, the surface roughness of the conductive circuit 2 is
The thickness is preferably 0.1 μm or more, particularly 0.3 μm to 3 μm, and most preferably 0.3 to 1.5 μm.

As described above, according to the method for manufacturing a multilayer wiring board of the present invention, the surface of the conductive circuit and the surface of the insulating layer are present on the same plane in each circuit board of each layer, or the conductive circuit is insulated. Since it is completely buried without any voids in the flexible substrate, there is no unevenness due to the conductive circuit as in the past, and the accuracy due to the disconnection and deformation of the circuit due to the voids that occurred in the past when laminating circuit boards Degradation can be prevented. As a result, a high-density multilayer wiring board having high-precision surface flatness suitable for flip-chip mounting, which is considered to be the main mounting format of semiconductors in the future, can be obtained.

[0028]

EXAMPLE An adhesive was applied to the surface of a transfer sheet made of polyethylene terephthalate (PET) resin to impart tackiness, and a copper foil having a thickness of 12 μm and a surface roughness of 0.8 μm was adhered to one surface. Thereafter, a resist made of a slurry having the same composition as the insulating layer described later is formed on the upper surface of the conductor foil in a pattern corresponding to the conductor circuit, and this is immersed in a ferric chloride solution to remove the non-pattern portion of the conductor foil. After the removal by etching, a transfer sheet having conductor wiring was obtained. The manufactured circuit is a fine pattern in which the line width of the conductor circuit is 100 μm and the distance between the wirings is 100 μm or less.

On the other hand, 35% by volume of a polyimide resin as an insulating slurry and 65% by volume of spherical silica as an inorganic filler are mixed, a solvent composed of methyl ethyl ketone is added to this mixture, and the mixture is sufficiently mixed by a mixer to obtain a viscosity. A 2000 poise slurry was prepared.

Then, the slurry is poured into a carrier sheet at a thickness of 125 μm by a doctor blade method, and then subjected to a heat treatment at 110 ° C. for 10 minutes to partially remove the solvent in the slurry and semi-cured. This was peeled from the carrier sheet to obtain a semi-cured insulating layer. At this time, the insulating layer has a needle penetration depth of 50 μm when a needle having a hemispherical tip and a diameter of 300 μm is penetrated by a force of 100 gf.
μm, and the amount of solvent contained therein is 1.8 μm.
% By weight.

Next, the semi-cured insulating layer is superimposed on the transfer sheet on which the conductor circuit is formed, and the conductor circuit on the transfer sheet is pressed by a vacuum laminator at a pressure of 30 kgf / cm ² and a temperature of 50 ° C. The transfer sheet was transferred and embedded in the semi-cured insulating layer, and then the transfer sheet was peeled off from the insulating layer to obtain an insulating substrate having a conductor circuit on the surface. At this time, the conductor circuit was almost completely buried in the insulating layer, and the surface of the conductor circuit and the surface of the insulating layer were substantially coplanar.

Similarly, after eight wiring boards having a thickness of 125 μm were formed, via holes were formed by laser, and the holes were filled with a copper paste containing a Cu—Ag alloy powder, and these were aligned. 50kg
/ Cm ^{2 at} a pressure of 50 ℃
Heat treatment was carried out for -5 hours to completely cure, thereby producing a multilayer wiring board.

As a result of observing the vicinity of the formation of the wiring circuit in the cross section of the obtained multilayer wiring board, no void was recognized, and as a result of conducting a continuity test of each wiring, no disconnection of the wiring was recognized. Did not.

[0034]

As described above in detail, according to the method for manufacturing a multilayer wiring board of the present invention, since there is no unevenness due to the conductor circuit in one layer of the circuit board, the gap which has conventionally been generated when the circuit boards are laminated is obtained. This can prevent the accuracy from deteriorating due to disconnection or deformation of the circuit due to the above. As a result, a high-density multilayer wiring board having high-precision surface flatness suitable for flip-chip mounting, which is considered to be the main mounting format of semiconductors in the future, can be obtained.

[Brief description of the drawings]

FIG. 1 is a view for explaining steps of a first embodiment of the manufacturing method of the present invention.

FIG. 2 is a diagram for explaining a structure of a multilayer wiring board according to a conventional method.

[Explanation of symbols]

 1. Transfer sheet 2. Conductor circuit 3. Insulating layer 4. Circuit board

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-27094 (JP, A) JP-A-5-90763 (JP, A) JP-A-7-297522 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H05K 3/46 H05K 3/20

Claims (3)

(57) [Claims] 1. A transfer sheet having a conductive circuit made of metal formed on a surface thereof, and a needle penetrating when a needle having a hemispherical tip and a diameter of 300 μm and having a diameter of 300 μm is penetrated by a force of 100 gf and containing at least a thermosetting organic resin. Preparing a semi-cured insulating layer having a depth of not less than 30 μm at room temperature, and contacting the conductive circuit formed on the transfer sheet with the semi-cured insulating layer by 30 minutes.
A step of pressing and embedding a conductor circuit in an insulating layer at a temperature of about 130 ° C. at a pressure of 10 kgf / cm ² or more; and removing a transfer sheet from the insulating layer in which the conductor circuit is transferred and embedded to form an insulating layer. A method for manufacturing a multilayer wiring board, comprising: a step of obtaining a circuit board having a conductor circuit embedded in a surface thereof; and a step of heating and completely curing the circuit board after laminating a plurality of the circuit boards. 2. The method according to claim 1, wherein the insulating layer contains an inorganic filler. 3. The conductive circuit according to claim 1, wherein said conductive circuit is made of copper, aluminum, gold,
2. The method for manufacturing a multilayer wiring board according to claim 1, comprising at least one kind selected from silver.