JP2003347695A - Method of manufacturing printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a printed wiring board, with which reliability of interlayer connection is enhanced in obtaining the wiring board by conducting a forming process on a prepreg formed using a glass base, after forming holes for interlayer connection and filling the holes for interlayer connection with an electrically conductive paste. <P>SOLUTION: In this method of manufacturing a printed wiring board, after holes for interlayer connection are formed in a prepreg, and the holes are filled with an electrically conductive paste, a metal foil or a core material on which a circuit has been formed is arranged on a surface or on both surfaces of the prepreg, and a heating-and-compressing process is conducted to form a laminated wiring board. For the prepreg, a woven glass fabric is used, into which a thermosetting resin composite is impregnated, wherein resin flowability is 0.1-10%. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a printed wiring board in which a prepreg is subjected to a hole forming process for interlayer connection prior to lamination molding, and then filled with a conductive paste, and the interlayer is connected through a molding process. It is about.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for higher density printed wiring boards for reasons such as miniaturization, light weight, and multifunctionality of personal computers, cellular phones, digital cameras, and the like.

[0003] As a method of manufacturing a printed wiring board capable of connecting an inner via hole between arbitrary layers, for example, a thermosetting resin is impregnated into a porous aramid nonwoven fabric having high shrinkage (compressibility) when pressed. A release film is laminated on the semi-cured prepreg, holes are formed for interlayer connection, a conductive paste is filled into the holes, and the release film is peeled off to form an adhesive sheet. A method is known in which a metal foil is overlaid on both front and back sides, compression molded, and a circuit is formed by a photographic method. A method is also known in which the printed wiring board obtained in this manner is used as a core material, and an adhesive sheet similar to the above is stacked on the core material and molded to form a multilayer.

[0004] The conductive paste used in this method comprises metal particles and a thermosetting resin, and the thermosetting resin in the conductive paste escapes into the prepreg during molding, so that the metal particles are densified and the connection between the layers is established. It is possible.

At this time, if the resin of the prepreg flows into the conductive paste or into the interface between the metal foil on the front and back and the conductive paste, there occurs a problem that a sufficient connection cannot be established in the via hole. When used, the resin in the prepreg is retained in the voids of the aramid nonwoven fabric during molding, and as a result, the resin is less likely to flow into the conductive paste or into the interface between the metal foil and the conductive paste, thereby suppressing the occurrence of poor conduction. Is done. In addition, since the aramid nonwoven fabric has high compressibility, the conductive paste is compressed and compacted at the time of molding, and the connectivity between layers is further improved.

[0006]

However, in the above prior art, by using an aramid nonwoven fabric as a base material of the prepreg, the adhesion between the insulating layer formed from the prepreg and the metal foil is weakened. There is a problem that delamination is likely to occur, and there is also a problem that the rigidity of the substrate is weakened and the mounting reliability is lowered. Further, the aramid base material is more expensive than a glass base material generally used for a prepreg for a printed circuit board, and there is a problem that the manufacturing cost is increased.

Therefore, the use of a glass substrate without using an aramid nonwoven fabric has been considered. However, the glass substrate has a lower shrinkage (compressibility) when pressed than an aramid nonwoven fabric, and the The amount of compression of the conductive paste at the time of molding is smaller than the case where a resin is used, and the holding power of the resin of the glass base material at the time of molding becomes smaller than that of the aramid fiber. When it is easy to flow into the interface between the metal foil on the front and back and the conductive paste, and if the prepreg is previously subjected to hole processing for interlayer connection and filling with the conductive paste,
It has been difficult to ensure conduction reliability during molding.

[0008] The present invention has been made in view of the above points, and a hole is formed in a prepreg formed using a glass substrate for interlayer connection, and a conductive paste is formed in the hole for interlayer connection. It is an object of the present invention to provide a method for manufacturing a printed wiring board, which can improve the interlayer connection reliability in obtaining a wiring board by performing a forming process after the filling of the printed wiring board.

[0009]

According to a first aspect of the present invention, there is provided a method of manufacturing a printed wiring board, comprising: forming a hole for interlayer connection in a prepreg; filling the hole with a conductive paste; Alternatively, in a method of manufacturing a wiring board in which either a metal foil or a core material having a circuit formed on both surfaces is arranged and laminated and integrated by heating and pressing, a thermosetting resin composition is formed on a glass woven fabric as a prepreg. And a resin having a flowability of 0.1 to 10%.

According to a second aspect of the present invention, as the thermosetting resin composition used for preparing the prepreg, a thermosetting resin composition containing no filler and having a melt viscosity at 130 ° C. of 10,000 to 50,000 ps is used. It is characterized by the following.

According to a third aspect of the present invention, as the thermosetting resin composition used for preparing the prepreg, one containing a filler and having a melt viscosity at 130 ° C. of 1,000 to 20,000 ps is used. It is characterized by the following.

The invention according to claim 4 provides a glass woven fabric used for producing a prepreg, having an air permeability of 25 cm ³ / cm ^2.
/ S or less and a thickness of 0.1 mm or less.

[0013]

Embodiments of the present invention will be described below.

The prepreg is obtained by impregnating the glass woven fabric with the thermosetting resin composition and heating and drying the same to semi-cure the thermosetting resin composition (B-stage state).

As the glass woven fabric, an appropriate one used for producing a prepreg for a wiring board can be employed.
In particular, the thickness is 0.1 mm or less, and the air permeability is 25 cm ³ / c.
It is preferable to use a glass woven fabric of m ² / s or less. The measurement of the air permeability can be performed using a Frazier-type tester based on JIS R3420.

When such a glass woven fabric is used,
In-plane composition variation during laser processing of legs
Suppressed, uniform hole drilling is possible and high reliability
Connection can be obtained. To elaborate, glass
Since the woven fabric is a state where fibers are woven vertically and horizontally,
In a plan view, a portion where the warp and the weft intersect,
A part where the warp or weft does not intersect and the warp
And voids are formed without both wefts
And therefore in the plane of the prepreg
The ratio between the fiber and the resin varies, and each part
In addition, the optimal irradiation conditions during laser processing will differ.
In some cases, uniform laser processing is difficult. In contrast
The glass woven cloth is 0.1 mm or less in thickness and the air permeability is 25 c.
m³/ Cm ²/ S or less, warp and weft
Is small and the proportion of voids is small.
And almost no longer exist, in the plane of the prepreg
The variation in the ratio between fiber and resin is reduced,
Variations in laser processing conditions can be reduced,
This allows for more stable drilling.

Here, the lower limit of the thickness of the glass woven fabric is not particularly limited, and the laser workability improves as the glass woven fabric becomes thinner. However, if the thickness is too thin, the amount of the conductive paste that can be filled in the prepreg decreases, and the interlayer becomes thinner. In some cases, it is difficult to sufficiently obtain the electrical connectivity of the above, so that the thickness is preferably 60 μm or more. In addition, the lower limit of the air permeability is not particularly limited, and the laser workability is improved as the air permeability is reduced. However, if the air permeability is too small, the impregnation when the resin is impregnated into the glass nonwoven fabric may be deteriorated.
It is preferably at least cm ³ / cm ² / s.

The matrix resin in the thermosetting resin composition is not particularly limited, and those generally used for forming prepregs for wiring boards can be used. Examples thereof include epoxy resins and phenol resins. Polyimide, unsaturated polyester resin, polyphenylene oxide resin, fluororesin, or the like, or a modified version of these resins can be used. The thermosetting resin composition is prepared by adding additives such as a curing agent and a curing accelerator, a filler, and the like to the matrix resin as needed. When the filler is compounded, it is not particularly limited, for example, glass fiber, carbon fiber, aromatic polyamide fiber, liquid crystal polymer fiber, potassium titanate, alumina, calcium carbide, talc, kaolin, clay, glass powder, glass balloon And the like. The compounding amount of these fillers is appropriately set, and the range of the particle diameter of these fillers, the presence or absence of surface treatment, and the like are also appropriately set, and are not particularly limited.

In preparing the prepreg, a varnish is prepared by dispersing and dissolving the thermosetting resin composition in an organic solvent, impregnating the varnish with a glass woven fabric, heating and drying to remove the solvent, The resin is in a semi-cured state, that is, B-staged.

In order to obtain a prepreg in this manner, the prepreg is formed such that the resin flowability is 0.1 to 10%. The resin flowability of prepreg is MI
It is measured in accordance with LP-13949H.

The resin flowability of the prepreg is adjusted, for example, by adjusting the amount of heat given in a drying step when preparing the prepreg. Also, by adjusting the resin content in the prepreg, or by adjusting the blending amount of the filler, it is also possible to adjust the resin flowability, and to have a desired resin flowability by appropriately changing these conditions. Prepreg can be obtained.

Prior to lamination molding, the prepreg manufactured as described above is subjected to perforation processing for interlayer connection and filling of the holes with a conductive paste. To explain an example of this step, first, a release film is pressure-bonded to both surfaces of the prepreg. This release film serves as a masking material when filling the conductive paste by the screen printing method. Next, the prepreg is punched together with the release film by irradiating a laser beam. As laser light,
An appropriate laser such as a carbon dioxide laser, an excimer laser, a YAG laser or the like can be used, and an optimum laser may be selected according to the thickness of the prepreg to be processed and the diameter of the hole to be formed. Next, after filling the conductive paste into the perforated prepreg from the surface on which the release film is adhered by screen printing, the film is peeled off to obtain a prepreg filled with the conductive paste. Can be. At this time, the conductive paste protrudes from the hole by the thickness of the release film on both surfaces of the prepreg.

As the conductive paste used here, an appropriate paste composed of metal particles and a thermosetting resin can be used. For example, Au, Ag, Cu, Sn,
Pb can be used alone or as a mixture, and as the thermosetting resin, an epoxy resin or the like can be used.

Using the prepreg filled with the conductive paste as a member for forming an insulating layer, a wiring board is manufactured.

For example, a metal foil such as a copper foil is placed on both sides of the prepreg, and the laminate is integrated by applying heat and pressure to obtain a double-sided metal foil-clad laminate. At this time, the prepreg is formed as an insulating layer by heat curing. In addition, the conductive paste is pushed into the hole with the protruding part,
In the hole filled with the conductive paste, the resin component in the conductive paste flows into the prepreg, the metal particles are densified in the hole, and a via hole for interlayer connection is formed.
A circuit is formed on the metal foils on both sides of the laminate by photolithography or the like as necessary, so that a conductor circuit is formed on both sides, and the conductor circuit is connected to the wiring board by a via hole (printed wiring). Board) is obtained.

Further, a multilayer board can be manufactured by using a prepreg filled with a conductive paste with the wiring board formed as described above as a core material. For example, the core material formed as described above on one surface of the prepreg filled with conductive paste is arranged such that a predetermined position of a circuit on the core material and an opening of a hole filled with conductive paste overlap. A core material is laminated on the other surface of the prepreg in the same manner, or a metal foil such as a copper foil is arranged and subjected to heat and pressure molding. At this time, as in the case described above, the prepreg is formed as an insulating layer by heat curing. In addition, the projecting portion of the conductive paste is pushed into the hole, and in the hole filled with the conductive paste, the resin component in the conductive paste flows into the prepreg, and the metal particles are densified in the hole and the interlayer connection is made. Via holes are formed. Further, when a metal foil on which no circuit is formed is disposed on the outer layer, the circuit is formed by a photographic method or the like as necessary.

Similarly, on one or both surfaces of a prepreg filled with a conductive paste, a core material having a single-layer or multilayer insulating layer on which a circuit is formed and a metal foil are disposed. Then, heat and pressure molding, lamination and integration, and further, if necessary, by forming a circuit on the outermost layer,
A wiring board (printed wiring board) can be obtained.

Further, a plurality of core materials having a single-layer or multi-layer insulating layer and a plurality of prepregs filled with a conductive paste are alternately arranged, and these core materials and prepregs are alternately arranged. By laminating and integrating, a multilayer wiring board can be obtained.

The above heating and pressing conditions are appropriately set according to the composition of the resin or conductive paste in the prepreg to be used, the dimensions of the members to be laminated, and the like.
Heat and pressure molding can be performed at 3.9 MPa (40 kg / cm ² ) for 2 hours.

When the wiring board is manufactured in this manner, the resin flowability of the prepreg when connecting layers between layers by the conventional method is usually 11% to 60% in order to fill the circuit pattern of the core material with the resin. However, in the present invention, since the resin flowability of the prepreg is in the range of 0.1 to 10%, during hot press molding,
The conductive paste forming via holes is suppressed by preventing the resin in the prepreg from entering the holes filled with the conductive paste and between the conductive paste and conductive layers such as metal foil and conductive circuits. It is possible to prevent a situation in which the resin in the prepreg intrudes into the metal particles or between the metal particles and the conductor layer and hardens, and the via hole improves the reliability of conduction between layers. it can.

At this time, the resin flowability of the prepreg is 0.1.
If it is less than 1%, it becomes difficult to fill the space between the circuit patterns with the resin constituting the prepreg, particularly at the time of lamination molding with the core material on which the circuit is formed. Due to the influence of the thinness, the connection between the conductive paste and the conductive layer is not sufficiently adhered to each other, resulting in a problem that a connection resistance value increases and a void remains. Also, the resin flowability of the prepreg is 10
%, The flowing resin flows into the metal particles of the conductive paste or into the interface between the conductive layer on the front and back sides and the conductive paste, and the connection resistance value increases, so that sufficient reliable connection cannot be obtained.

In particular, when a filler is not blended in the thermosetting resin composition constituting the prepreg, when preparing the prepreg, 130% of the resin in the prepreg is used.
Melt viscosity at ℃ is 10,000-50,000ps
It is preferable to form so as to fall within the range of (P). This melt viscosity can be measured, for example, by rubbing out the resin component from the prepreg, processing it into a pellet, and using a height type flow tester (“CFT-100” manufactured by Shimadzu Corporation). In this way, at the time of heat and pressure molding, the resin in the prepreg may intrude into the hole filled with the conductive paste or between the conductive paste and the conductive layer such as a metal foil or a conductive circuit. Is further suppressed.

When a filler is blended into the thermosetting resin composition constituting the prepreg, the melt viscosity at 130 ° C. of the resin in the prepreg is 1000 to 20.
Preferably, it is formed to have a range of 000 ps (P). In this way, at the time of heat and pressure molding, the resin in the prepreg may intrude into the hole filled with the conductive paste or between the conductive paste and the conductive layer such as a metal foil or a conductive circuit. Is further suppressed. At this time, the reason why the range of the melt viscosity is lower than in the case where the filler is not blended is that the flow of the resin in the prepreg is suppressed by the blending of the filler.

[0034]

The present invention will be described below in detail with reference to examples.

(Examples 1 to 11, Comparative Examples 1 to 3) A prepreg was obtained by impregnating a base material with an epoxy resin varnish and drying it at 170 ° C with a drier. Substrate used, varnish composition, resin flowability of obtained prepreg and 1
The melt viscosity at 30 ° C. is as shown in Tables 1 and 2.

A release film (polyethylene terephthalate film, 20 μm thick) was formed on both sides of the prepreg.
m) at 110 ° C., 1.96 MPa (20 kg / c
After press-bonding by heating and pressing under the conditions of m ² ) for 1 minute, carbon dioxide laser was irradiated to form holes for interlayer connection.

Laser processing conditions using a carbon dioxide laser are as follows:
In Examples 1 to 10 and Comparative Examples 1 and 2 using a glass woven fabric having a thickness of 0.1 mm as the base material, the mask diameter was 2.1 m.
m, processing energy 6 mJ / P, pulse width 15 μs, number of shots 5
Hole processing of 0 μm was performed. Also, as a substrate, a thickness of 0.1
In Example 11 using 5 mm glass woven fabric, the mask diameter was 2.1 mm, the processing energy was 6 mJ / P, and the pulse width was 15 mm.
Irradiation under the conditions of μs and 8 shots,
A hole having a diameter of 100 μm was formed. In Comparative Example 3 using an aramid nonwoven fabric having a thickness of 0.1 mm as the base material,
Mask diameter 2.1mm, processing energy 24.2mJ /
Irradiation was performed under the conditions of P, a pulse width of 15 μs, and the number of shots was 1 shot, and a hole having a diameter of 100 μm was formed.

Next, a conductive paste composed of Cu powder and an epoxy resin is filled into the holes for interlayer connection from the release film side by a screen printing method, and then the release film is peeled off. A filled prepreg was obtained. At this time, the conductive paste has an average particle size of 2 μm.
85% by weight of spherical copper particles, 12% by weight of bisphenol A type epoxy resin ("Epicoat 828", manufactured by Japan Epoxy Resin Co., Ltd.), and an amine adduct curing agent ("MY-24", manufactured by Ajinomoto Co., Ltd.) 3% by weight and kneaded with three rolls were used.

A copper foil having a thickness of 18 μm is laminated above and below the prepreg filled with the conductive paste.
Under pressure of 3.9 MPa (40 kg / cm ² ), heat and pressure molding is performed for 2 hours, and the outermost copper foil on the front and back surfaces is partially etched by a photographic method to form a circuit, thereby forming a via hole. Thus, a core material having a connection between layers was obtained (sample 1).

The two core members thus formed,
The three prepregs filled with the conductive paste formed in the same manner as described above are alternately stacked on a sheet-by-sheet basis, and a copper foil having a thickness of 18 μm is further laminated on the outermost layers on the front and back sides.
After heating and pressing for 2 hours under the conditions of 9 MPa (40 kg / cm ² ), the copper foil on the front and back is partially etched by a photographic method to form circuits, thereby forming all the insulating layers. A six-layer printed wiring board having inner via holes was obtained (Sample 2).

(Evaluation Test) For each example and comparative example,
Using Sample 1, the connection resistance between layers was measured. The measurement was performed by using a milliohm meter (manufactured by Yokogawa Hewlett-Packard, model number "4328A") and measuring the resistance value between the upper and lower sides of the via hole. Those exceeding 2 mΩ and 3 mΩ or less were judged as “Δ” and those exceeding 3 mΩ as “X”.

Further, laser workability was evaluated. The evaluation was performed by measuring the surface roughness of the inner wall of the hole of the sample 1. The sample having a height difference of 10 μm or less was evaluated as “「 ”, the sample having a height difference of 10 to 30 μm was evaluated as“ △ ”, Those having a size of 30 μm or more were judged as “×”.

Further, the conductor circuits on the front and back of Sample 2 were all removed by an etching method, and the moldability was evaluated. The evaluation was carried out by visual inspection, and “カ ス” indicates that no blur and void were confirmed, and “△” indicates that voids of 0.5 mm ² or less were confirmed and voids of 0.5 mm ² or less exceeded 0.5 mm ² . Those in which voids were confirmed or in which blurring was confirmed were determined to be "x".

Using Sample 2, the copper foil peel strength and the flexural modulus were measured in accordance with JIS-C6481.

The above results are also shown in Tables 1 and 2.

[0046]

[Table 1]

[0047]

[Table 2]

As is apparent from these results, when the glass woven fabric was used, in Comparative Example 1 in which the resin flowability of the prepreg was 0, the connection resistance value was poor and the moldability was poor. In Comparative Example 2 in which the resin flowability of the prepreg was large, the connection resistance value was deteriorated. In Comparative Example 3 using the aramid nonwoven fabric, although the connection resistance value, the laser workability, and the moldability were excellent, the copper foil peel strength and the flexural modulus were low.

On the other hand, in Examples 1 to 11, the connection resistance value, the laser workability and the formability reached a sufficient level, and the copper foil peel strength and the flexural modulus were high.

Further, Example 10 in which the thickness of the glass woven fabric exceeds 0.1 mm and the air permeability of the glass nonwoven fabric of 25 cm ³
In Examples 1 to 9, the laser workability was particularly excellent as compared with Example 11 exceeding / cm ² / s.

Further, as compared with Examples 3 and 5 in which the melt viscosity of the resin in the prepreg at 130 ° C. was lower than the preferred range, the connection resistance was particularly excellent in the other examples, and In comparison with Examples 1 and 4 in which the melt viscosity of the resin at 130 ° C. was higher than the preferred range, the moldability was particularly excellent in other Examples.

[0052]

As described above, in the method of manufacturing a printed wiring board according to the first aspect of the present invention, a hole is formed in a prepreg for interlayer connection, and the hole is filled with a conductive paste.
Either a metal foil or a core material having a circuit formed on one or both sides of the prepreg is arranged, and the laminate is integrated by heating and pressing. Since a resin having a flowability of 0.1 to 10%, which is produced by impregnating the resin composition, is used, the resin in the prepreg penetrates into the holes filled with the conductive paste during the heat and pressure molding. Intrusion between the conductive paste and the conductive layer such as a metal foil or a conductive circuit is suppressed, so that the conductive paste is formed in the metal particles of the conductive paste forming the via hole or between the cured product and the conductive layer. It is possible to prevent a situation in which the resin in the prepreg enters and hardens, and to improve the conduction reliability between the layers by using the via holes even though the glass fabric having low compressibility is used. With Peel strength and flexural modulus are those which can provide a high printed circuit board.

According to a second aspect of the present invention, as the thermosetting resin composition used for preparing the prepreg, a thermosetting resin composition containing no filler and having a melt viscosity at 130 ° C. of 10,000 to 50,000 ps is used. Therefore, at the time of heating and pressing, the resin in the prepreg is further suppressed from entering the hole filled with the conductive paste and from entering between the conductive paste and the conductor layer such as a metal foil or a conductor circuit. The via hole can further improve the reliability of conduction between the layers.

According to a third aspect of the present invention, there is provided a thermosetting resin composition containing a filler and having a melt viscosity at 130 ° C. of 1,000 to 20,000 ps as a thermosetting resin composition used for preparing a prepreg. Further, at the time of heating and pressing, the resin in the prepreg is further suppressed from entering the holes filled with the conductive paste and from entering between the conductive paste and the conductive layer such as a metal foil or a conductive circuit. The reliability of conduction between layers can be further improved by the via holes.

Further, according to the invention of claim 4, the glass woven fabric used for producing the prepreg has an air permeability of 25 cm ³ / cm ^2.
/ S or less and a thickness of 0.1 mm or less are used,
When the hole processing for interlayer connection to the prepreg is performed by laser processing, in-plane composition variation is suppressed, so that uniform hole processing is possible, and a highly reliable connection can be obtained.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Kiyoaki Ihara             1048 Kadoma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works, Ltd.             In the formula company F-term (reference) 5E317 AA24 BB02 BB12 CC22 CC25                       CD27 CD32 GG09 GG11                 5E346 AA02 AA12 AA43 CC04 CC09                       CC10 CC12 CC13 CC14 CC32                       DD12 DD32 EE09 FF07 FF09                       FF18 GG15 HH11

Claims (4)

[Claims] A prepreg is subjected to a hole processing for interlayer connection, and after filling the hole with a conductive paste, one of the prepregs is provided with a metal foil or a core material provided with a circuit on one or both surfaces thereof, In a method of manufacturing a wiring board to be laminated and integrated by heat and pressure molding, a resin prepreg prepared by impregnating a glass woven fabric with a thermosetting resin composition and having a resin flowability of 0.1 to 10% A method for manufacturing a printed wiring board, comprising using: 2. A thermosetting resin composition used for preparing a prepreg which does not contain a filler and has a melt viscosity at 130 ° C. of 10,000 to 50 ° C.
2. The method for manufacturing a printed wiring board according to claim 1, wherein the method uses 000 ps. 3. A thermosetting resin composition used for preparing a prepreg, which contains a filler, and has a melt viscosity at 130 ° C. of 1,000 to 20,000.
2. The method for manufacturing a printed wiring board according to claim 1, wherein the printed wiring board has a ps. 4. A glass woven fabric used for producing a prepreg, having an air permeability of 25 cm ³ / cm ² / s or less and a thickness of 0.5 cm ³ / cm ² / s.
The method for manufacturing a printed wiring board according to any one of claims 1 to 3, wherein one having a thickness of 1 mm or less is used.