JPH11150366A - Production of sequential multilayer wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve accuracy of the thickness of a wiring board by specifying the range of the lowest molten viscosity of thermosetting resin being employed in a metal foil with resin or a resin sheet at the time of laminating a sequential multilayer wiring board thereby sustaining a correct resin flow at the time of molding. SOLUTION: A metal foil having a film of thermosetting resin, e.g. thermosetting polyphenylene ether resin, having lowest molten viscosity of 500-100000 poise is superposed on the surface of an inner layer material or a thermosetting resin is superposed on the surface of an inner layer material, a metal foil is placed thereon and then they are hot pressed to produce a bonded metal foil pattern. Furthermore, a metal foil is hot pressed on the circuit pattern through a thermosetting resin and the operation is repeated one time or more thus completing a sequential multilayer wiring board.

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 in which a plurality of metal foils are sequentially laminated via a thermosetting resin and formed into a multilayer while bonding. More specifically, by defining the minimum melt viscosity of the resin with the metal foil or resin sheet at the time of molding in a predetermined range, a sequential multilayer wiring board having excellent thickness accuracy and circuit embedding property can be obtained. And a method for producing the same.

[0002]

2. Description of the Related Art In recent years, there has been a remarkable trend toward miniaturization and high-density mounting methods in the field of electronic devices for communication, consumer use, industrial use, etc. However, there is an urgent need to establish a laminated build-up method capable of forming high-density wiring. Therefore, as a material to be used for the lamination build-up method, a base material with a resin or a resin sheet having more excellent heat resistance and electric characteristics in a high frequency region is being developed.

[0003] A base material with a resin has a thermosetting resin film on one side of a metal foil. For example, a copper foil with an epoxy resin is conventionally used. The epoxy resin used for the resin-attached substrate is for producing a copper-clad laminate, and generally has a low melt viscosity and a very large resin flow. Also, in the case of a thermosetting resin used for a resin sheet that is integrally heated and pressed against one surface of a metal foil during lamination, it is difficult to control production conditions and the like.

[0004]

When a thermosetting resin such as an epoxy resin having a low melt viscosity and a very large flow is used for the production of a multilayer wiring board, a plurality of thermosetting resins, particularly via the thermosetting resin, are used. In a so-called high-order lamination build-up method, in which a plurality of metal foils are repeatedly bonded and laminated in multiple layers while being repeatedly bonded, the thickness of a thermosetting resin functioning as an electrical insulator is determined within the wiring board. There has been a problem that it is difficult to keep the characteristic impedance of the wiring within a certain range while keeping it constant everywhere.

Accordingly, the present invention has been made in view of such problems of the prior art, and an object of the present invention is to improve the moldability of a thermosetting resin to be used to improve the thickness accuracy and the thickness. An object of the present invention is to provide a method for manufacturing a reliable sequential multilayer wiring board having excellent circuit embedding properties.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, when sequentially laminating and forming a multilayer wiring board, they are used for a metal foil with a resin or a resin sheet. By defining the minimum melt viscosity of the thermosetting resin in a certain range, it was found that a multilayer wiring board in accordance with the object of the present invention could be obtained sequentially, and the present invention was completed.

That is, according to the method for manufacturing a sequential multilayer wiring board according to the first aspect of the present invention, a laminate comprising an inner layer material and a metal foil with a thermosetting resin or a thermosetting resin sheet and a metal foil between press hot plates is provided. When the body is laminated and molded, the minimum melt viscosity of the thermosetting resin is set to 500 poise or more and 10,000 or more.
It is characterized by being within a range of 0 poise or less.

According to a second aspect of the present invention, there is provided a method for manufacturing a sequential multilayer wiring board according to the first aspect of the present invention, wherein the metal foil with thermosetting resin or the thermosetting resin is used. The resin of the conductive resin sheet is a thermosetting polyphenylene ether-based resin composition.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. The basis of the method for manufacturing a multilayer wiring board of the present invention is as follows.
A metal foil having a thermosetting resin film on one side of the metal foil is laminated on the surface of the inner layer material (a circuit may be formed on the surface), or a thermosetting resin sheet is laminated on the surface of the inner layer material. Further, a metal foil is placed thereon, placed between press hot plates and bonded by heating and pressing, and the bonded metal foil is processed as necessary to form a circuit pattern, and then heat-cured thereon. The operation of heating and pressurizing the metal foil via the conductive resin to bond the metal foil is repeated one or more times to sequentially form a multilayer laminate.

The inner layer material in the present invention refers to a metal-clad laminate. Normally, a metal foil and a prepreg obtained by impregnating a thermosetting resin into a woven or nonwoven fabric substrate obtained from a synthetic fiber such as a glass cloth or an aromatic polyamide fiber are used. Manufactured by pressing. If necessary, a circuit can be formed on the surface.

The material of the metal foil used in the present invention is not particularly limited as long as it is a conductive metal foil, but copper foil and aluminum foil are preferable because they are easily available and can be easily etched. Among them, copper foil is most preferable.

The thickness of the metal foil is not particularly limited, but is preferably 500 μm or less from the viewpoint of easy handling.
0 μm or less is more preferable, and 105 μm or less is most preferable. In the metal foil, the surface on which the thermosetting resin film is formed or the surface in contact with the thermosetting resin sheet has been subjected to roughening and / or coupling treatment in order to enhance the adhesion to the resin. You may. The roughened electrolytic copper foil manufactured and sold for manufacturing a wiring board can be used as it is in the manufacture of the resin-coated base material of the present invention.

[0013] The resin of the metal foil with a thermosetting resin used in the present invention or the thermosetting resin used for the resin sheet has a minimum melt viscosity of 500 to 100,000 poise under lamination molding conditions. Is required. By regulating in this way, it is possible to obtain a desired effect of the present invention, that is, a multilayer wiring board having excellent thickness accuracy and good embedding.

If the viscosity is less than 500 poise, the resin flows too much, and the thickness of the insulating layer cannot be kept constant in the wiring board, so that the characteristic impedance of the wiring cannot be kept constant. On the other hand, when the poise exceeds 100,000 poise, defective embedding of the inner layer circuit occurs, and it is difficult to form a multilayer wiring board. Preferred minimum melt viscosity is 1000 poise or more from the viewpoint of plate thickness accuracy, and 60,000 poise or less from the viewpoint of circuit embedding, more preferably 20 poise.
More than 00 poise and not more than 40000 poise.

The melt viscosity of the resin in the present invention is measured, for example, by using a dynamic analyzer RAD (manufactured by Rheometrics) using a φ25 mm parallel plate and molding the resin into a φ25 mm disk. The temperature can be swept under the same conditions as described above. The minimum melt viscosity is the minimum value of the melt viscosity under molding conditions, and the temperature at that time is defined as the temperature at which the minimum melt viscosity is exhibited.

Examples of the thermosetting resin used in the present invention include thermosetting resins such as thermosetting polyphenylene ether resin, phenol resin, and epoxy resin having a low dielectric constant. Such a thermosetting resin may be a resin obtained by modifying the resin itself, or may be a resin alone and / or a mixture of a resin and a polyfunctional compound. Among the above thermosetting resins, a thermosetting polyphenylene ether resin is particularly preferable from the viewpoint of control of melt viscosity and electric characteristics. Examples of such a thermosetting polyphenylene ether resin include, for example, JP-A-7-165846.
JP-A-7-16649, a composition described in JP-B-7-37567, a composition described in JP-B-7-26013, and the like.

In the present invention, the thermosetting resin may be mixed with fillers and additives in an amount not to impair the original properties, for the purpose of imparting a desired performance according to its use. The filler may be fibrous or powdery, and may be silica, alumina, talc, mica, glass beads,
Glass hollow spheres and the like can be given. In addition, as additives, flame retardants, antioxidants, heat stabilizers, antistatic agents,
Pigments, dyes, coloring agents, and the like are included. For the purpose of adjusting the melt viscosity during molding, a plasticizer, a thickener and the like may be added.

In the present invention, a thermoplastic resin such as a polystyrene-based polymer or a diene-based resin can be blended for the purpose of imparting a film-forming property to the thermosetting resin.

The thickness of the resin film of the resin-attached metal foil or the resin film of the resin sheet is preferably 10 μm or more, more preferably 20 μm or more, and most preferably 30 μm or more from the viewpoint of easy handling. When the film thickness is extremely small, it becomes difficult to perform the lamination build-up method.

As a method for forming a thermosetting resin film,
Although any method may be used, a preferable method is, for example, a method of applying and drying a varnish in which the resin is dissolved or dispersed in a solvent. A suitable solvent is selected according to the selection of the resin. Further, as another preferable method, a method of forming a melt film without using a solvent can also be mentioned.

The circuit may be formed on the inner layer material, the resin-attached metal foil or the resin sheet by any means, but is usually performed by etching or plating of the metal foil. A circuit can be formed on the resin surface by printing using a conductive paste or the like.

The minimum melt viscosity of the resin in the present invention is 50
0 poise to 100000 poise, preferably 10 poise
There is no particular limitation on the method of adjusting the pressure from 00 poise to 60000 poise, more preferably from 2000 poise to 40000 poise. For example, a method by adjusting the chemical structure, molecular weight, or composition of the resin may be used. Adjusting the melt viscosity by partially curing a thermosetting resin having an extremely low melt viscosity by a method suitable for each resin such as heat treatment or photochemical treatment is also an effective means. For example, a resin having a low melt viscosity such as an epoxy resin can be in a B-stage state and the minimum melt viscosity can be adjusted within a specified range.

Further, the minimum melt viscosity can be changed depending on molding conditions. The minimum melt viscosity changes depending on the heating rate. When the holding temperature is provided during the temperature rise, the minimum melt viscosity can be changed depending on the holding temperature and the holding time. The molding conditions may be considered depending on the composition of the resin.

When the resin of the resin-attached metal foil or the resin sheet is a thermosetting polyphenylene ether-based resin composition, it is desirable to perform molding under the following conditions. That is, the molding temperature is preferably from 150 to 250 ° C. More preferably 160 to 230 ° C, still more preferably 170 to 2
20 ° C. If the temperature is lower than 150 ° C., it takes time until the resin is sufficiently cured, which is not preferable. On the other hand, if the temperature exceeds 250 ° C., the copper foil may be oxidized and deteriorated, which is not preferable because it affects reliability.

The molding pressure is preferably 5 to 60 kg / cm ² . If it is less than 5 kg / cm ² , poor filling may occur,
The thickness accuracy may be impaired. On the other hand, 60kg / c
If it exceeds m ² , the resin may flow too much, or molding distortion may occur, thereby impairing reliability.

The heating rate is preferably 1 to 10 ° C./min. More preferably, it is 3 to 7 ° C./min. If it is less than 1 ° C./min, the melt viscosity may not be sufficiently low, resulting in poor embedding. If it is more than 10 ° C./min, the minimum melt viscosity may be too low and the plate thickness accuracy may be impaired.

When the melt viscosity is adjusted by providing a holding temperature during the heating, the resin temperature must be not less than (the temperature at which the lowest melt viscosity is −50 ° C.) or more (the temperature at which the lowest melt viscosity is + 30 ° C.) or less. After maintaining the temperature at a constant temperature for 10 minutes or more at a temperature in the temperature range, it is preferable to raise the temperature to the curing temperature. By maintaining the temperature at a constant temperature before reaching the minimum melt viscosity, the curing reaction can be advanced before the melt viscosity decreases, and the minimum melt viscosity can be increased. In addition, by maintaining the viscosity around the minimum melt viscosity, rapid hardening can be suppressed, and sufficient filling properties can be obtained with an appropriate melt viscosity. The holding temperature and time may be considered according to the composition and purpose of the resin.

The molding pressure is from 5 to 20 kg / c until the resin temperature reaches a temperature in a temperature range from (the temperature at which the lowest melt viscosity is −80 ° C.) to the temperature at which the lowest melt viscosity is attained.
m ² , 20-60 kg / cm at temperatures above this temperature
Pressing at ² can also be used for molding. By applying a low pressure when the resin is not sufficiently melted and applying a pressure when the melt viscosity becomes sufficiently low, it is possible to obtain a multilayer wiring board having excellent thickness accuracy and embedding property.

In general, a vacuum press is often used for lamination molding to prevent the occurrence of voids in the insulating layer and to obtain a highly reliable substrate. In this case, the degree of vacuum is preferably set to 50 torr or less.

In the case where the resin of the metal foil with resin or the resin of the resin sheet is formed and the inner through hole is filled with the resin at the same time, when the resin reaches the minimum melt viscosity, the through hole is sufficiently filled with the resin. It is performed so that an appropriate pressure is applied. From the viewpoint of thickness accuracy and the like, a holding temperature may be provided during the temperature rise.

[Embodiments] Hereinafter, embodiments of the present invention will be described in comparison with comparative examples to clarify the effects of the present invention.

The method for measuring the melt viscosity of the resin and the method for evaluating the substrate in this comparative test are described below. (1) Melt viscosity of resin Dynamic analyzer RAD manufactured by Rheometrics
, Using a parallel plate of φ25 mm. (2) Plate Thickness Accuracy The thickness of each of ten substrates of 510 mm * 340 mm was measured at 10 locations using a micrometer.

Thickness variation R: difference between maximum thickness and minimum thickness After embedding and polishing the substrate with epoxy resin, the cross section was observed and the thickness of the insulating layer (the resin-coated copper foil resin portion) was measured.

Thickness variation r: difference between maximum thickness and minimum thickness (3) Embedding property After embedding and polishing a substrate with an epoxy resin, a cross section was observed. (4) Solder heat resistance test The substrate was cut out into a 50 mm square, and one side of the copper foil was removed, and one side was removed of half the copper foil. This was boiled in boiling distilled water for 1 hour, cooled, and immersed in a solder bath at 290 ° C. for 2 minutes.

Example 1 A thermosetting polyphenylene ether-based resin was used as the thermosetting resin, and a 12 μm thick electrolytic copper foil for a printed circuit board was used as a metal foil. Created. Resin thickness is 60μ
m. On the other hand, as an inner layer material, a 0.7 mm thick double-sided copper-clad laminate (using a prepreg obtained by impregnating a glass cloth with a thermosetting polyphenylene ether-based resin) having 18 μm copper foil stretched on both sides was prepared. Circuits having a residual copper ratio of 50% were formed on both surfaces of the inner layer material.

The resin-coated copper foil was laminated on both surfaces of the inner layer material and pressed. The press was heated at a rate of 3 ° C / min.
The temperature was raised to 0 ° C., and curing was performed for 60 minutes. The molding pressure was 30 kg / cm ² . At this time, the minimum melt viscosity of the resin was 31,000 poise.

(Example 2) As a thermosetting resin, a thermosetting polyphenylene ether resin having a composition different from that of Example 1 was used, and a 12 µm-thick electrolytic copper foil for a printed board was used as a metal foil. A copper foil with a resin for a wiring board was prepared. The thickness of the resin was 60 μm. The copper foil with resin was laminated on both surfaces of the double-sided copper-clad laminate (inner plate) on which a circuit having a residual copper ratio of 50% obtained in Example 1 was formed, and pressed. The press was carried out at a heating rate of 3 ° C./min, by heating to 200 ° C. and curing for 60 minutes. Molding pressure is 30kg / c
It was m ^2. The minimum melt viscosity of the resin at this time was 1400
It was 0 poise.

Example 3 A thermosetting polyphenylene ether resin having a composition different from that of Examples 1 and 2 was used as the thermosetting resin, and a 12 μm-thick electrolytic copper foil for a printed board was used as a metal foil. This was used to prepare a copper foil with resin for a multilayer wiring board. The thickness of the resin was 60 μm. The copper foil with resin was laminated on both sides of the double-sided copper-clad laminate on which a circuit having a residual copper ratio of 50% obtained in Example 1 was formed, and pressed. The press was heated at a rate of 3 ° C./min to 165 ° C., held for 20 minutes, then again heated to 200 ° C. at 3 ° C./min and cured for 60 minutes. The molding pressure was 10 kg / cm ² until the resin temperature reached 110 ° C., and then increased to 30 kg / cm ² . At this time, the minimum melt viscosity of the resin was 7000 poise, and the minimum melt viscosity point temperature was 16
3 ° C.

Comparative Example 1 An epoxy resin for a copper-clad laminate was used as a thermosetting resin, and a 12 μm thick metal foil was used.
m, a resin-coated copper foil for a multilayer wiring board was prepared using the m. The thickness of the resin was 60 μm.
The copper foil with resin was laminated on both sides of the double-sided copper-clad laminate on which a circuit having a residual copper ratio of 50% obtained in Example 1 was formed, and pressed. The press was carried out at a heating rate of 1.5 ° C./min, by heating to 170 ° C. and curing for 120 minutes. Molding pressure is 2
0 kg / cm ² . At this time, the minimum melt viscosity of the resin was 200 poise.

(Comparative Example 2) A multilayer wiring using a thermosetting polyphenylene ether-based resin having a composition different from that of the embodiment as the thermosetting resin and an electrolytic copper foil for a printed board having a thickness of 12 μm as a metal foil. A copper foil with board resin was prepared. The thickness of the resin was 60 μm. The press was carried out at a heating rate of 0.5 ° C./min, by heating to 200 ° C. and curing for 60 minutes. The molding pressure was 30 kg / cm ² . At this time, the minimum melt viscosity of the resin was 120,000 poise.

With respect to these examples and comparative examples,
Table 1 shows the results of the evaluation of the items (1) to (4). Examples 1 to 3 are not only excellent in both thickness accuracy and circuit embedding property, but also have soldering heat resistance enough to withstand practical use as a sequential multilayer wiring board.

[0042]

[Table 1]

[0043]

As described above, according to the first aspect of the present invention,
According to the method for manufacturing a sequential multilayer wiring board according to the above, when forming a multilayer while laminating the laminate on the inner layer material and bonding with a thermosetting resin, the minimum melt viscosity of the thermosetting resin is 500 poise to 100,000 poise Because we restricted to the following range,
The flow of the resin at the time of molding can be appropriately maintained, and the effect of obtaining a highly reliable multilayer wiring board having excellent thickness accuracy and good embedding property can be obtained.

According to the second aspect of the present invention, the above effects can be more reliably obtained by using a thermosetting polyphenylene ether-based resin composition as the thermosetting resin.

Accordingly, the sequential multilayer wiring board manufactured according to the present invention is suitable for high-speed digital circuits and high-frequency analog circuits.

Claims (2)

[Claims] When the inner layer material and a metal foil with a thermosetting resin or a laminate made of a thermosetting resin sheet and a metal foil are stacked and molded between press hot plates, a minimum melting of the thermosetting resin is performed. A method for manufacturing a sequential multilayer wiring board, wherein the viscosity is in the range of 500 poise to 100,000 poise. 2. The method according to claim 1, wherein the resin of the metal foil with thermosetting resin or the thermosetting resin sheet is a thermosetting polyphenylene ether-based resin composition.