JP3720830B2 - Manufacturing method of multilayer wiring board whose insulating layer contains organic resin - Google Patents

Description

The present invention relates to a method for manufacturing a multilayer wiring board whose insulating layer contains an organic resin .

Conventionally, after bonding a copper foil to the surface of an insulating substrate impregnated with resin in paper, this is etched to form a fine circuit, and then this substrate is laminated to form a multilayer printed wiring board. Proposed. In addition, in such a printed wiring board, in order to increase its strength, a substrate in which a spherical or fibrous inorganic filler is dispersed in an organic resin has been proposed, and an insulating substrate made of these composite materials Application to a multichip module (MCM) or the like on which a large number of semiconductor elements are mounted is also being studied.

Recently, the frequency used in communication-related applications is shifting to a high frequency, and a wiring board disposed in a communication device is required to have excellent characteristics such as a low dielectric constant and a low dielectric loss. Also, a large current is required for the wiring board. In addition, such a tendency tends to increase more and more in order to reduce the size and weight of electronic devices.
JP 58-121698 A JP 05-283865 A JP-A-61-210691 JP-A 63-274199

  However, in such a wiring board, there is a problem that a gap is generated between the conductor circuit and the conductor in the insulating layer or via hole. In particular, the conductor circuit is embedded in the insulating layer without any gap. It is difficult. In addition, when a plurality of wiring layers are stacked, there is a problem of deterioration in accuracy due to circuit disconnection or deformation due to air gaps. In addition, there are problems such as unevenness in the wiring board due to the conductor circuit. Therefore, the thickness of the conductor circuit cannot be increased, and it cannot be applied as a circuit that allows a large current to flow.

  In addition, it is impossible to obtain a multilayer wiring board with high-precision surface flatness suitable for flip chip mounting, and the multilayer wiring board cannot be integrated, so that the wiring is miniaturized and the dimensional accuracy of the board is improved. I can't let you.

Therefore, the present invention provides a method for producing a multilayer wiring board in which an insulating layer containing an organic resin is capable of producing a multilayer wiring board excellent in smoothness, in which generation of voids and circuit disconnection are suppressed.

The method for producing a multilayer wiring board in which the insulating layer of the present invention contains an organic resin includes a step of forming a conductor circuit made of a metal foil on the surface of a transfer sheet, and a via hole in a soft insulating layer containing at least an organic resin. Forming a conductor in the via hole, and laminating and pressing the conductor circuit formed on the transfer sheet to the insulating layer having the conductor, thereby connecting the conductor and the conductor circuit. A step of transferring and embedding the conductor circuit in the insulating layer, and peeling off the transfer sheet from the insulating layer in which the conductor circuit is imprinted and producing a wiring layer in which the conductor circuit is embedded in the surface of the insulating layer you wherein comprising the steps of, a.

Moreover, it is preferable that the method for manufacturing a multilayer wiring board in which the insulating layer of the present invention contains an organic resin includes a step of producing a plurality of the wiring layers and stacking and integrating them.

In the method for manufacturing a multilayer wiring board in which the insulating layer of the present invention contains an organic resin , the via hole is preferably formed by laser processing.

In the method for manufacturing a multilayer wiring board in which the insulating layer of the present invention contains an organic resin , the conductor is preferably formed by filling the via hole with a conductor paste.

Moreover, as for the manufacturing method of the multilayer wiring board in which the insulating layer of this invention contains organic resin, it is desirable that the said conductor paste is a copper paste containing Cu-Ag alloy powder.

Moreover, as for the manufacturing method of the multilayer wiring board in which the insulating layer of this invention contains organic resin, it is desirable for the said organic resin to consist of either 1 type of a polyimide resin or a polyester resin.

As described in detail above, according to the method for manufacturing a multilayer wiring board in which the insulating layer of the present invention contains an organic resin, there is no unevenness due to the conductor circuit in one wiring layer, and the conductor circuit due to the gap generated at the time of bonding It is possible to prevent deterioration in accuracy due to disconnection or deformation with an insulating layer or a conductor in a via hole. As a result, it is possible to obtain a high-density multilayer wiring board having high-precision surface flatness that is suitable for use at high frequencies and suitable for flip-chip mounting, which is considered to be a major semiconductor mounting format in the future.

  The present invention will be described below with reference to the drawings. As shown in FIG. 1, first, a conductor circuit is formed on the surface of the transfer sheet 1. The conductor circuit is preferably made of at least one selected from the group consisting of copper, aluminum, gold, and silver, or two or more alloys, and most preferably copper or an alloy containing copper. In some cases, a high resistance metal such as a Ni—Cr alloy may be mixed or alloyed for adjusting the resistance of the circuit.

  This conductor circuit can be formed by etching or laser processing a desired metal foil, or by plating. For example, in the etching method, as shown in FIG. 1A, after the metal foil 2 made of the above-mentioned conductor circuit forming metal is bonded to the surface of the transfer sheet 1, the metal is formed as shown in FIG. After a resist 3 is formed in a conductor circuit shape on the foil by a method such as photoresist or screen printing, unnecessary portions are etched away to obtain a desired conductor circuit 4 as shown in FIG.

  At this time, the resist 3 generally requires a step of removing an unnecessary portion of the metal foil by etching and then removing it with a resist removing solution and washing. However, the resist 3 is made of a material for forming an insulating layer to be described later. If it is contained or made of a similar material, it is not necessary to remove the resist, which is advantageous in that the process can be simplified.

  According to FIG. 2, first, as shown in FIG. 2A, a transfer sheet 21 on which a conductor circuit 22 is formed and a soft insulating layer 23 are prepared. The conductor circuit 22 is formed by etching or laser processing a desired metal foil, or by plating. FIG. 2A shows an etching method. In this case, after forming a metal foil on the entire surface of the transfer sheet 21, a resist is applied to the conductor circuit pattern, and then an etching process is performed, and then the resist is removed and washed. Thus, the conductor circuit 22 is formed. In this figure, the resist is removed. However, if the resist is made of the same material as the insulating layer described later, the resist need not be removed and washed, but may be left.

  On the other hand, since the insulating layer 23 finally constitutes the insulating layer of the multilayer wiring board, it is desired to be made of a material suitable as the insulating layer. Specifically, it is made of an insulating material containing at least an organic resin. As the organic resin, for example, polyimide resin, polyester resin, PTFE (fluorine resin), PPE (polyphenylene ether), BT resin (bis resin) Maleimide triazine), epoxy resin, polyimide resin, fluororesin, phenol resin and the like are desirable. In addition, when a thermosetting resin is included, it is good that it is a semi-hardened state. The insulating layer 23 is filled with a conductor by forming a via hole 24 in advance by a well-known method.

Next, as shown in FIG. 2B, a transfer sheet 21 on which the conductor circuit 22 is formed and an insulating layer 23 in a soft state are laminated, and these are pressed together, preferably a pressure of 10 kg / cm ² or more. By applying, the conductor circuit 22 is embedded in the insulating layer 23.

  The insulating layer 23 at this time desirably has a needle penetration depth of 10 μm or more, particularly 30 μm, more preferably 50 μm or more when a needle having a hemispherical tip and a diameter of 300 μm is entered with a weight of 100 g. This softness can be arbitrarily controlled by the amount of solvent or plasticizer added.

  Next, as shown in FIG. 2C, the surface of the conductor circuit 22 and the surface of the insulating layer 23 are flush with each other by peeling off the transfer sheet 21 from the laminate produced in the step (b). A single-layer wiring layer 25 having excellent properties can be manufactured.

  In such an embodiment, when the resist is removed, in order to increase the adhesion strength between the conductor circuit 22 and the insulating layer 23, is a copper foil having a surface roughness of the conductor circuit 22 at the conductor circuit formation portion of 0.1 μm or more used? Alternatively, surface roughening such as etching may be performed. The surface roughness is particularly preferably 0.3 μm to 3 μm, optimally 0.3 to 1.5 μm.

  In some cases, a multilayer wiring board 26 as shown in FIG. 2 (d) can be produced by laminating a plurality of layers to the wiring layer 25 formed in FIG. 2 (c).

Thus, according to the method for manufacturing a multilayer wiring board in which the insulating layer of the present invention contains an organic resin, the surface of the conductor circuit and the surface of the insulating layer are present in the same plane in each wiring layer, or Since the conductor circuit is completely embedded in the insulating layer without any gaps, there are no irregularities due to the conductor circuit as in the past. It is possible to prevent the deterioration of accuracy due to. As a result, the thickness of the conductor circuit can be increased even in a multilayer wiring board, and the circuit can be applied as a circuit in which a large current flows.

  Therefore, it can be used even when the operating frequency of semiconductors in the future increases, and it has high-precision surface flatness suitable for flip-chip mounting, which is considered to be the main mounting format. A high-density multilayer wiring board is obtained. This is suitable when a multilayer wiring board is further integrated and a thin insulating layer, fine wiring, or dimensional accuracy of the board is required.

Adhesive is applied to the surface of a transfer sheet made of polyethylene terephthalate (PET) resin to make it sticky. Glued to one side. Then, after forming a resist made of a photosensitive resin on the conductor circuit, exposure and development were performed, and this was immersed in a ferric chloride solution to remove the non-patterned portion by etching, and then the remaining resist was removed. Note that the fabricated circuit is a fine pattern in which the line width of the conductor circuit is 75 μm and the distance between the wirings is 75 μm or less.

  On the other hand, a slurry having a viscosity of 500 poise was prepared by adding a solvent composed of toluene and methyl ethyl ketone to the polyimide resin as an insulating slurry and thoroughly mixing with a mixer. Then, this slurry was molded to a thickness of 100 μm by the doctor blade method, and then treated at 40 ° C. for 30 minutes to semi-dry the slurry to form a soft insulating layer having a needle penetration degree of 70 μm.

A via hole was formed in the insulating layer with a CO ₂ laser, and a copper paste containing Cu—Ag alloy powder was filled in the hole to form a single insulating layer.

After that, this soft insulating layer is laminated with the transfer sheet on which the previous conductor circuit is formed, and is heated and pressure-bonded by applying a pressure of 50 kg / cm ² while heating at 80 ° C. in a vacuum, and then the transfer sheet. Was peeled off. As a result, it was possible to obtain a wiring layer in which a conductor circuit made of copper was embedded in an insulating layer.

In the same manner as described above, eight wiring layers were prepared, aligned, and laminated, and then an insulating layer was laminated on the outermost surface and pressure-bonded at a pressure of about 50 kg / cm ² for 5 hours at 200 ° C. A multilayer wiring board was produced by heat treatment and complete curing.

  As a result of observing the vicinity of the conductor circuit formation in the cross section of the obtained multilayer wiring board, no voids were observed. As a result of conducting a continuity test of each wiring, no disconnection of the wiring was recognized.

Comparative example

A copper foil having a thickness of 70 μm and a surface roughness of 3.0 μm was bonded to the surface of the polyimide resin with an adhesive. Then, after forming the resist which consists of photocuring resin in a conductor circuit, this was immersed in the ferric chloride solution, and the non-pattern part was etched away. Further, the residual resist was removed with a resist stripper and washed to form a circuit. The produced conductor circuit has a pattern with a line width of 150 μm and a distance between the lines of 150 μm.

Similarly, after preparing six wiring layers each having a thickness of 200 μm, each was coated with an adhesive, aligned, laminated, pressure-bonded at a pressure of 50 kg / cm ² and heat-treated at 200 ° C. to be completely cured. Thus, a multilayer wiring board was produced.

  As a result of observing the vicinity of the conductor circuit formation in the cross section of the obtained multilayer wiring board, a gap of 5 μm in size was observed on both sides of the conductor circuit, and as a result of investigating the transmission characteristics of the wiring, It was confirmed that the transmission characteristics were inferior.

It is a figure for demonstrating the process of forming a conductor circuit in a transfer sheet. It is a figure for demonstrating the process of the manufacturing method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 21 Transfer sheet 2 Metal foil 3 Resist 4, 22 Conductor circuit 23 Insulating layer 24 Via hole 25 Wiring layer 26 Multilayer wiring board

Claims (6)

A step of forming a conductor circuit made of a metal foil on the surface of the transfer sheet, a step of forming a via hole in a soft insulating layer containing at least an organic resin, and forming a conductor in the via hole; A step of laminating and pressing the conductor circuit formed on the transfer sheet to the insulating layer and transferring and embedding the conductor circuit in the insulating layer so that the conductor and the conductor circuit are connected; A step of peeling the transfer sheet from the insulating layer in which the conductor circuit is transferred and embedded to produce a wiring layer in which the conductor circuit is embedded on the surface of the insulating layer, and the insulating layer is made of an organic resin. A method for manufacturing a multilayer wiring board. The manufacturing method of the multilayer wiring board in which the insulating layer of Claim 1 which comprises producing | generating multiple said wiring layers and laminating | stacking and integrating them comprises an organic resin . 3. The method of manufacturing a multilayer wiring board according to claim 1 or 2, wherein the via hole is formed by laser processing. 4. The method for manufacturing a multilayer wiring board according to claim 1, wherein the conductor is formed by filling the via hole with a conductor paste. 5. The method for producing a multilayer wiring board according to claim 1, wherein the conductive paste is a copper paste containing Cu-Ag alloy powder. 6. The method for manufacturing a multilayer wiring board according to claim 1, wherein the organic resin is made of any one of a polyimide resin and a polyester resin.

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