JPH1174625A - Wiring board and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To prevent the occurrence of chipping or cracking, to achieve high flatness of the surface of an insulator, and to reduce the width of a wiring in order to manufacture a high-density wiring board. Provided is a high-performance and high-reliability wiring board having a large adhesion to a wiring board and a method for manufacturing the wiring board.
Is buried in a state where the upper surface is exposed.
And the upper surface width w1 of the surface wiring 3 is made larger than the lower surface width w2 so that the cross-sectional shape of the surface wiring 3 is inverted trapezoidal with a formation angle α ° of 45 ° to 80 °. I do. Further, in order to obtain such a wiring board, the metal layer 13 formed on the surface of the transfer sheet 11 is subjected to an etching treatment to form a wiring having a trapezoidal cross-sectional shape, and the surface of the wiring has an average surface roughness of 200 nm. After roughening as above,
The transfer sheet 11 is pressed against the surface of the insulator 2 to transfer the wiring to the surface of the insulator 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board used for, for example, a semiconductor device storage package and a method of manufacturing the same, and more particularly to a high-density wiring board having fine wirings arranged on an insulator surface and a method of manufacturing the same. is there.

[0002]

2. Description of the Related Art Conventionally, a wiring board, for example,
2. Description of the Related Art Multilayer ceramic wiring boards capable of relatively high-density wiring have been widely used as wiring boards used for packages containing semiconductor elements. This multilayer ceramic wiring board is composed of an insulator such as alumina and a wiring conductor made of a high melting point metal such as W or Mo formed on the surface thereof, and a concave portion is formed in a part of the insulator. The semiconductor element is housed in the recess, and the recess is hermetically sealed by the lid.

Meanwhile, wiring boards used for multi-layer wiring boards and packages for housing semiconductor elements, etc., have become more and more dense in the future as the performance of various electronic devices has been improved, and the wiring width and wiring pitch have been reduced to 50 μm or less. It is required that the via hole be an interstitial via hole (IVH), and the mounting method of the IC chip also changes from the wire bonding to the flip chip, so that the flatness of the substrate itself needs to be reduced. ing. However, a multilayer ceramic wiring board is manufactured by printing metallized ink on a green sheet before sintering, and laminating and sintering the printed sheets. Due to the shrinkage, the resulting substrate is liable to be deformed such as warpage or dimensional variation, etc., and therefore, in response to strict requirements regarding ultra-high density of circuit boards and flatness of substrates such as flip chips etc. However, there was a problem that it could not cope sufficiently.

Another problem of the multilayer ceramic wiring board is that ceramics are hard and brittle, so that chipping or cracking of the ceramics is likely to occur in a manufacturing process or a transporting process. Since the hermetic sealing of the device may be impaired, there are problems such as low yield.

On the other hand, as a wiring board other than the ceramic wiring board, a resin wiring board is used in which a surface wiring made of a metal layer such as copper is formed on the surface of an insulating substrate containing an organic resin. Such a resin wiring board does not have defects such as chipping or cracking unlike a ceramic wiring board, and has the advantage that heat treatment at a high temperature, such as firing, is not required for multilayering.

However, a resin wiring board is generally formed by attaching a metal foil such as a copper foil on an insulating substrate, and then removing unnecessary portions of the metal foil by etching or plating. Since it is formed, there are various problems.

For example, the insulating substrate is degraded by a chemical such as etching, or the conductor surface wiring formed using a metal foil is only placed on the surface of the insulating substrate. There is a problem that a gap is easily formed at the interface between the two and the insulating substrate due to poor adhesion, which leads to a wiring failure and the use of the substrate becomes impossible. In addition, in forming a multilayer, there is a problem that the sequential lamination must be performed to form the IVH, and a batch lamination cannot be performed. In addition, since the protrusions are formed on the insulating substrate by the conductor surface wiring, the flatness is low, and the flatness required for flip chip mounting has not been satisfied.

[0008] Among these problems of the wiring board made of resin,
In order to solve the problem of poor adhesion between the surface wiring and the insulating substrate, the lower surface and the surface of the conductor surface wiring are roughened by growing needle-like crystals by means such as blackening treatment, so that the insulator and the conductor layer are not roughened. There has been proposed a method for increasing the adhesiveness of a sheet.

However, the method of increasing the adhesion by roughening the lower surface and the surface of the conductor wiring is to reduce the adhesion of the wiring extremely when the wiring width is reduced in order to produce a high-density wiring board, and There is a problem in that the reliability of the device during long-term use is reduced. Further, even when a via-hole conductor is formed in a via-hole by using a conductive paste or the like to establish conduction between layers, there is a problem that the adhesion between the wiring and the via-hole conductor is reduced.

For this reason, it has been difficult at present to produce a highly reliable substrate on which fine wirings, via-hole conductors and the like necessary for forming a high-density wiring substrate are formed.

Japanese Patent Application Laid-Open No. 9-64514 discloses an invention relating to a method for manufacturing a printed wiring board for the purpose of improving the problem of peeling of a surface wiring from a transfer sheet. In this manufacturing method, a metal layer for forming surface wiring is transferred from a transfer sheet provided on the metal film to the prepreg serving as an insulator, and the metal layer is buried and formed. Was removed by soft etching. The printed wiring board formed in this way has a rectangular cross-sectional surface wiring and a smooth metal layer formed on the transfer sheet. When the wiring width is reduced, the adhesion of the wiring is not sufficient.

The wiring can be transferred to a soft insulator (prepreg), and the surface of the wiring substrate can be smoothed by embedding the wiring on the surface of the insulator. Is rectangular, as shown in FIG. 3, when the wiring 21 on the surface of the transfer sheet 20 is pressed against the insulator 22, the insulator 22 around the wiring 21 is necessarily deformed. There was a problem that sufficient adhesion with the body 23 could not be obtained.

[0013]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, the present invention is directed to a method for manufacturing a high-density wiring board, in which chipping and cracking are unlikely to occur, the insulator surface has a high flatness, and the wiring density is high. It is an object of the present invention to provide a high-performance and highly-reliable wiring board having a large adhesive strength of a wiring to an insulator even when the width is reduced, and a method for manufacturing the same.

[0014]

As a result of intensive studies on the above-mentioned problems, the present inventor has found that a surface wiring made of a metal material is buried on an insulator surface in a state where the upper surface is exposed. By making the average surface roughness 200 nm or more and forming the cross-sectional shape of the surface wiring into an inverted trapezoid having an angle of formation 45 ° to 80 ° so that the upper surface width is larger than the lower surface width, fine wiring, IVH Even if the lower surface and side surfaces of the wiring are roughened on a high-density wiring board on which a structure is formed, the adhesion is not reduced, but the adhesion is greatly improved, and a high-performance and highly reliable substrate can be obtained. I learned.

Further, as a method of manufacturing such a wiring board, a metal layer formed on the surface of a transfer sheet is subjected to an etching treatment to form a wiring having a trapezoidal cross section, and the surface of the wiring is made to have an average surface. After the surface is roughened to a roughness of 200 nm or more, the transfer sheet is pressed against the surface of the insulator, and the wiring is transferred to the surface of the insulator. It has been found that a method for manufacturing a wiring board characterized by embedding a surface wiring having an inverted trapezoidal cross-sectional shape larger than the lower surface width on the surface of the insulator is suitable.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a wiring board 1 according to an embodiment of the present invention.
As shown in the cross-sectional view of FIG. 1, the wiring board 1 is composed of a plurality of insulators 2, and a surface wiring 3 made of a metal material containing a low-resistance metal as a main component is buried in the insulator 2; The wiring 3 is connected by a connecting conductor 3b made of the above-described metal material filled in the via hole 3a.

The surface wiring 3 has a side surface 4 and a lower surface 5.
Is roughened so that anchoring can be obtained with the insulator 2 and has an inverted trapezoidal cross-sectional shape in which the formation angle α ° of the upper side 6 and the horizontal side 7 is acute, It is buried so that the upper surface width w1 is larger than the lower surface width w2.

In the cross-sectional shape of the surface wiring 3, the formation angle α ° formed by the lateral side 4 and the upper side 5 is 45 ° to 80 °.
And the lower surface 5 and the side surface 4 have a surface roughness of 200 nm.
It is preferable that it is above. Among them, the formation angle α °
Is more preferably 50 ° to 75 °. When the formation angle α ° is larger than 80 °, it is difficult to roughen the side surface of the wiring, and the adhesion strength between the insulator 2 and the surface wiring 3 is reduced.
When a circuit pattern on a transfer sheet to be described later is pressure-bonded to a prepreg, it becomes difficult to embed the circuit pattern. On the other hand, if it is smaller than 45 °, the adhesion between the insulator 2 and the surface wiring 3 may be insufficient. The surface roughness of the lower surface 5 and the side surface 4 of the wiring is 2
It is preferably at least 00 nm, more preferably at least 400 nm. If the surface roughness is smaller than 200 nm, the adhesion strength between the insulator 2 and the surface wiring 3 may be insufficient.

An insulator 2 constituting the multilayer wiring board 1
Is, for example, an inorganic filler together with an organic resin, inorganic fibers,
It is made of a composite material containing at least one kind selected from organic fibers. The inorganic filler, the inorganic fiber, and the organic fiber are preferably uniformly dispersed in the organic resin at a ratio of 20 to 80% by volume.

As the organic resin constituting such a composite material, PPE (polyphenylene ether resin), BT
It is made of a resin such as a resin (bismaleide triazine), an epoxy resin, a polyimide resin, a fluororesin, a phenol resin, and a polyaminobismaleimide, and it is particularly preferable that the raw material is a liquid thermosetting resin at room temperature.

On the other hand, as the inorganic filler, SiO 2
₂ , Al ₂ O ₃ , ZrO ₂ , TiO ₂ , AlN, Si
Known materials such as C, BaTiO ₃ , SrTiO ₃ , MgTiO ₃ , zeolite, CaTiO ₃ , and aluminum borate can be used. In addition, the shape can be any shape such as a spherical shape and a needle shape.

Further, examples of the inorganic or organic fiber include glass fiber, aramid fiber, cellulose fiber and the like, and any property such as woven fabric and non-woven fabric may be used. In any case, in order to increase the strength of the multilayer wiring board 1 and obtain a highly reliable board, it is desirable to include at least one or more layers of the insulator 2 containing fibers.

It is preferable that the low-resistance metal material forming the surface wiring includes at least one selected from copper, aluminum, gold, and silver. A high-resistance metal such as Ni-Cr may be used as necessary for the circuit.

Next, a method of manufacturing the multilayer wiring board 1 of FIG. 1 will be described below.

First, an insulator 2 is manufactured to obtain a multilayer wiring board 1. Taking the case of using an inorganic filler as an example, an insulating composition obtained by adding a liquid organic resin to the inorganic filler is sufficiently mixed by means of a kneader (kneader) or a three-roll mill. A sufficiently mixed material is formed into a sheet by a rolling method, an extrusion method, an injection method, or a doctor blade method, and then the organic resin is semi-cured. The insulating slurry is preferably prepared by adding toluene, butyl acetate, methyl ethyl ketone, methanol, methyl cellosolve acetate, isopropyl alcohol, methyl isobutyl ketone, dimethylform to a composite material of an organic resin and an inorganic filler as described above, which constitutes an insulator. It is composed of a fluid having a predetermined viscosity by adding a solvent such as acid. From this perspective,
The viscosity of the slurry is 100 to 300, depending on the forming method.
0 poise is appropriate. For semi-curing, if the organic resin is a thermoplastic resin, cool the mixture under heating, and in the case of a thermosetting resin, heat the organic resin to a temperature slightly lower than the temperature sufficient for complete solidification. I just need. In the case of using a woven or non-woven fabric, a varnish-like resin is impregnated into fibers such as a woven or non-woven fabric and dried to produce a semi-cured prepreg insulator 2.

Next, the insulator 2 manufactured as described above is used.
A desired via hole is formed by punching or laser processing with respect to the semi-cured prepreg for forming the conductive paste, and then filled with a conductive paste. The metal powder to be mixed in the conductor paste is desirably made of at least one low-resistance metal among copper, aluminum, silver, and gold, and a paste can be obtained by adding an organic solvent and a binder.

Then, a surface wiring 3 is formed on the semi-cured insulator 2. In order to form the wiring circuit, as shown in FIG. 2A, at least one or two or more selected from copper, gold, silver, aluminum and the like are provided on the surface of the transfer sheet 11 made of a resin film via an adhesive. A metal foil 12 made of an alloy of the above is laminated. At this time, copper or an alloy containing copper is most desirable.

Next, after a resist layer 16 having a desired circuit pattern is provided as shown in FIG. 2B, the resist layer 16 is formed by an etching method as shown in FIG.
A metal layer 13 for forming a surface wiring is formed on a transfer sheet 11 having a shape such that the cross-sectional shape becomes trapezoidal. At this time, the formation angle β ° of the base 14 and the side 15 of the trapezoid is 45 °.
In order to achieve the angle of ~ 80 °, the etching rate of the metal layer should be 2-5.
It is good to set it to 0 μm / min. Further, as shown in FIG. 2D, the surface roughness of the upper surface 18 and the side surface 17 of the metal
The metal layer 13 is made of formic acid or NaClO
₂ , surface treatment with a mixed solution of NaOH, Na ₃ PO _{4 and} the like. The surface roughness can be controlled by the roughening speed, and the surface can be satisfactorily roughened at a roughening speed of 1 μm / min or more.

Next, the transfer sheet 11 provided with the metal layer 13 in this manner is turned to the direction in which the metal layer 13 faces the prepreg 19, and then, as shown in FIG. Prepreg 19 with pressure 10-5
It is applied at a pressure of about 00 kg / cm 2. Then, the transfer sheet 11 is peeled off together with an adhesive layer (not shown) while the metal layer 13 is left in the prepreg 19 to transfer the metal layer 13 and bury the surface wiring 3.

Finally, the prepregs 19 on which the surface wirings 3 are formed as described above are laminated, pressed and heated, adhered and integrated, and the multilayer wiring board 1 can be manufactured.

According to the above-described manufacturing method, the cross-sectional shape of the wiring to be transferred to the surface of the prepreg is set to the predetermined trapezoidal shape, so that when the wiring is pressed against the surface of the prepreg,
As a result of suppressing the deformation of the prepreg around the wiring, the pressure is pressed against the prepreg over the horizontal and bottom sides of the inverted trapezoid of the wiring, and as a result, the wiring cross section is rectangular as compared to the case (a). It is possible to greatly improve the adhesion to the insulator.

According to the wiring board of the present invention, since fine and high-density wiring is provided on the surface of the insulator, for example, this wiring board is used as a core substrate and the surface thereof is formed by a bull-up method. A high-density wiring board can also be manufactured by sequentially laminating an insulator made of a photosensitive resin and wirings and via-hole conductors formed by a thin film forming method such as plating.

[0034]

EXAMPLE A BT resin, PPE or polyimide thermosetting resin was coated with spherical fused SiO ₂ , BaT having an average particle size of 5 μm.
iO ₃ , MgTiO ₃ , CaTiO ₃ , aspect ratio 5
Of aluminum borate whiskers of 50% by volume, butyl acetate, toluene, and MEK as solvents were added thereto, and a catalyst for accelerating the curing of the organic resin was further added. After mixing for a time, a 200-μm-thick sheet-shaped pre-leg for forming an insulator from the slurry by a doctor blade method was produced (Samples 1 to 19 in Table 1). In addition, BT resin, P
PE and polyimide are impregnated and dried at 50% by volume to a thickness of 200
Semi-cured prepregs for forming a μm insulator were prepared (Samples 20 to 22 in Table 1).

[0035]

[Table 1]

These prepregs were cut into 150 mm squares, and via holes having a diameter of 100 μm were formed using a CO ₂ laser. A copper paste containing copper-silver alloy powder as a main component was embedded in the via hole by screen printing.

On the other hand, polyethylene terephthalate (PE)
Applying an adhesive to the transfer sheet surface of T)
Was adhered. Then, a photosensitive resist is applied to the surface of the copper foil using the insulating slurry as a resist, and a pattern is formed by exposing through a glass mask, and then immersed in a ferric chloride solution to remove a non-pattern portion. It was removed by etching. After the resist was stripped, the top and side surfaces of the metal layer were treated with 10% formic acid. The wiring formed by the metal layer is a fine pattern having a bottom width of 50 μm and an interval between wirings (wiring pitch) of 50 μm or less.

Then, the above-mentioned etching treatment was carried out under the conditions shown in Table 1, a metal layer was formed in a cross-sectional shape having the above-mentioned formation angle β °, and after the metal layer was roughened at the roughening rate shown in Table 1, the transfer sheet and the prepreg were formed. 30k by vacuum laminating machine
After pressurizing with a pressure of g / cm ² for 30 seconds, only the transfer film and the adhesive layer were peeled off, and the metal layer was transferred to bury the surface wiring. Finally, add this prepreg to 30
Six sheets were laminated at a pressure of kg / cm ² and heat-treated at 200 ° C. for 5 hours to obtain a multilayer wiring board.

The angle of the wiring formed on the resin film was measured by observing the cross section of the wiring with an SEM. The surface roughness of the lower surface and the side surface of the wiring was measured by AFM.

For these samples, the adhesion strength between the insulator and the surface wiring was determined by vertically pulling a 2 mm square pad and measuring the load. Table 1 shows the results.

As is clear from Table 1, the formation angle α °
(= Β °) is 45 ° to 80 °, and the maximum surface roughness Rmax of the lower surface and the side surface of the surface wiring (surface roughness of the upper surface and the side surface of the metal layer) is 200 nm or more.
A highly reliable multilayer substrate of kg / mm ² or more was obtained.

[0042]

As described above, according to the present invention, since the surface wiring is buried in the surface of the insulator, chipping and cracking are less likely to occur, and the flatness of the surface of the insulator is reduced. By making the cross-sectional shape of the surface wiring into an inverted trapezoid in the wiring board having a higher height, even if the lower surface and the side surface of the wiring are roughened in a high-density wiring board on which fine wiring, IVH, etc. are formed, the adhesion does not decrease. Rather, an excellent effect is obtained in that the adhesion is greatly improved and a high-performance and highly reliable wiring board can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a wiring board according to the present invention.

FIGS. 2A to 2E are process diagrams for schematically explaining a method of manufacturing the wiring board of FIG. 1;

FIGS. 3A and 3B are schematic cross-sectional views for explaining a state when a wiring is pressed against a prepreg, wherein FIG. 3A is a diagram of a conventional method and FIG. 3B is a diagram of a method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Multilayer wiring board 2 Insulator 3 Surface wiring 3a Via hole 3b Connecting conductor 4, 17 Side surface 5 Lower surface 6 Upper side 7, 15 Horizontal side 11 Transfer sheet 12 Metal foil 13 Metal layer 14 Bottom 16 Resist layer 18 Upper surface 19 Prepreg w1 Upper surface width w2 Bottom width α ° Forming angle

Claims (2)

[Claims] 1. A surface wiring made of a metal material is buried on an insulator surface in a state where an upper surface thereof is exposed. The surface wiring has an average surface roughness of 200 nm or more, and an upper surface width of the surface wiring is a lower surface width. A wiring substrate having a larger cross-sectional shape of the surface wiring and an inverted trapezoid having a formation angle α ° of 45 ° to 80 °. 2. A metal layer formed on the surface of a transfer sheet is etched to form a wiring having a trapezoidal cross section, and the surface of the wiring is roughened to an average surface roughness of 200 nm or more. By pressing the transfer sheet against the surface of the insulator and transferring the wiring to the surface of the insulator, the cross-sectional shape of the inverted trapezoid having an angle of formation α of 45 ° to 80 ° and an upper surface width larger than the lower surface width is obtained. A method of manufacturing a wiring board, comprising: burying a surface wiring having the exposed upper surface on the surface of the insulator.