JP2931565B2 - Wiring board and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board suitable for a package for accommodating a semiconductor element, wherein a conductive wiring layer containing a metal powder is formed on at least the surface and / or inside of an insulating substrate containing an organic resin. The present invention relates to a manufacturing method, and more particularly to improvement in resistance to migration of a conductive wiring layer and migration resistance.

[0002]

2. Description of the Related Art Conventionally, as a multilayer wiring board used for a wiring board, for example, a package for housing a semiconductor element, a ceramic provided with an insulating layer such as alumina and a wiring layer made of a high melting point metal such as W and Mo. Wiring boards are often used, but such ceramic wiring boards are hard and brittle, so that in the manufacturing process or the transporting process, chipping or cracking of the ceramic is likely to occur, and also before sintering. When a metallized paste is printed on a green sheet, and the printed sheets are laminated and sintered, there is a problem that a substrate obtained by sintering is liable to be deformed such as warpage or dimensional variation, etc. However, there is a problem that it is not possible to sufficiently cope with strict requirements for flatness of a substrate such as ultra-high density and flip chips.

[0003] Therefore, recently, a copper foil is adhered to the surface of an insulating layer containing a resin and then etched to form a substrate on which a fine circuit is formed, or a paste containing a metal powder such as copper is printed on the insulating layer. After forming the wiring layer by laminating,
Alternatively, a printed wiring board has been proposed in which a hole is drilled for a via at a desired position after lamination by microdrilling or punching, a metal is attached to the inner wall of the via by a plating method, and a wiring layer is connected to form a multilayer. . Further, as an insulating layer, a substrate in which a powdery or fibrous inorganic filler is dispersed with respect to a resin in order to increase the strength has been proposed. Application to a multi-chip module (MCM) on which a semiconductor element is mounted is also being studied.

[0004] In response to the demands for multi-layer printed wiring boards, ultra-fine wiring, and precision as described above, a conductive paste containing a low-resistance metal powder such as copper on the surface of an insulating layer containing an organic resin. Attempts have been made to produce a multilayer wiring board on which circuit patterns and via-hole conductors are formed.

[0005]

However, in a conductor paste containing a low-resistance metal powder, a resin for bonding is added in order to improve the printability on the insulating layer and to bond the metal powders to each other. In addition, since this resin easily intervenes at the powder contact interface, there is a problem that the resistance value is higher than that of a circuit formed by ordinary copper foil or copper plating.

For this reason, silver powder is often used as the low-resistance metal powder in the paste. The reason why silver is used as the main conductor component is that it has the highest conductivity among metals and has higher chemical stability than a base metal such as copper. However, silver has a very high cost, and silver has a phenomenon of migration between silver wirings due to the interaction between atmospheric moisture and a DC electric field, so-called migration. There was a problem in reliability under some conditions.

[0007] On the other hand, copper has a relatively low specific resistance and can be obtained at a lower cost than silver, but the surface is easily oxidized, so it is necessary to store it by a special method. It is.

Therefore, in order to solve these problems,
A conductive material in which the surface of copper particles is coated with low-resistance silver to reduce the specific resistance and suppress the oxidation of the copper particles is disclosed in JP-A-56-101.
No. 739 and Japanese Patent Application Laid-Open No. 8-13837.

However, even when these silver-coated copper particles are used, a binding resin of 3% by weight or more per total solid content is required for binding these particles, and this resin component is At present, the contact resistance is increased due to the interposition of the contact portion between them, and the specific resistance of the conductor wiring layer has not yet been reduced.

Various improvements have also been made, such as decomposing the resin by heating or conducting electric heating. However, sufficient effects have not been obtained in these heat treatments. There is a problem such as adversely affecting the insulating layer.

An object of the present invention is to provide a wiring board having a conductor wiring layer which is inexpensive, has excellent conductivity and migration resistance, does not cause the above-mentioned disadvantages, and a method for manufacturing the same. is there.

[0012]

Means for Solving the Problems As a result of repeated studies on the above-mentioned problems, the present inventor has used a copper-silver alloy powder having a predetermined ratio as a metal powder component for forming a conductor wiring layer,
By applying a pulse current to the conductor wiring layer formed using this powder, a discharge is generated at the contact portion between the metal particles, and the resin or oxidation on the surface of the copper-silver alloy powder that has prevented electrical conduction. As a result of being able to weld the particles at the same time as removing the object, the resistance of the conductor wiring layer can be significantly reduced, and since silver does not exist alone as in silver-coated copper powder, it has been found that migration is suppressed, It has been found that this makes it possible to form a highly reliable conductor wiring layer that can meet the demands for ultra-fine and precise multilayer printed wiring boards.

That is, the wiring board of the present invention comprises an insulating substrate containing at least an organic resin, 1-50% by weight of silver and 50-99% by weight of copper on the surface and / or inside of the insulating substrate.
A conductive wiring layer containing a copper-silver alloy powder having an average particle size of 3 to 10 μm, wherein a contact portion between the alloy powders of the conductive wiring layer is welded. And

Further, according to the method for manufacturing a wiring board of the present invention, the average particle diameter of 1 to 50% by weight of silver and 50 to 99% by weight of copper is present on at least the surface and / or inside of an insulating substrate containing an organic resin. After forming a conductor wiring layer containing a copper-silver alloy powder of 3 to 10 μm, a pulse current is applied to the conductor wiring layer to weld a contact portion between the copper-silver alloy powder. In particular, the current density of the applied pulse current is 1 to 2000 A / cm ² , and the pulse width is 0.01 to
1000 msec. It is characterized by being.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A wiring board according to the present invention is basically composed of an insulating substrate and a conductor wiring layer.

In the multilayer wiring board, the wiring layer includes a through-hole conductor, and the through-hole conductor electrically connects a conductor wiring layer between different layers formed on the surface and / or inside each insulating substrate. Serves to connect to

The insulating substrate is made of an insulating material containing at least an organic resin. As the organic resin, for example, a thermosetting polyphenylene ether resin, a bismaleimide triazine resin, an epoxy resin, a polyimide resin, a fluorine resin, a phenol resin, a polyamide bis Including resins such as maleimide.

Further, it is desirable that a filler is compounded with resin in the insulating substrate in order to increase the strength of the entire insulating substrate or the wiring substrate. As the filler to be compounded with the resin, SiO ₂ , Al ₂ O ₃ , Z
rO ₂ , TiO ₂ , AlN, SiC, BaTiO ₃ , S
Known materials such as inorganic materials such as rTiO ₃ , zeolite, CaTiO ₃ , and aluminum borate, and organic materials such as aramid woven fabric and aramid nonwoven fabric can be used. Further, a sheet (prepreg) in which a glass cloth is impregnated with a resin is used. May be. The shape of the filler has an average particle diameter of 20 μm or less, particularly 10 μm or less, most preferably 7 μm or less, in a substantially spherical powder, an average aspect ratio of 2 or more, particularly 5 or more, fibrous or flat, Furthermore, non-woven fabrics and woven fabrics can also be used. In a composite material of a resin and a filler, the volume ratio of the resin to the filler is 15:85 to 5: 5.
It is appropriate that the compounds are combined in a ratio of 0:50.

The conductor wiring layer forms a conductive path for electrically connecting electronic components such as semiconductor elements mounted on a wiring board to each other or to the outside. According to the present invention, This conductor wiring layer contains a copper-silver alloy powder as a conductor material. The copper-silver alloy particles contain 1 to 50% by weight of silver, 50 to 99% by weight of copper, particularly 5 to 30% by weight of silver.
% By weight and 70-95% by weight of copper. If the silver content is less than 1% by weight, the oxidation resistance becomes poor as in the case of the conventional copper powder, and the silver content becomes 50%.
If the content is more than the weight%, migration of silver is likely to occur.

Further, the alloy powder has an average particle size of 3 to 3.
It needs to be 10 μm, especially 3 to 7 μm, optimally 3 to 5 μm. This is because when the average particle size is smaller than 3 μm or larger than 10 μm, the printability as a conductor paste is deteriorated and the resistance increases due to a decrease in the filling rate of the copper-silver alloy particles. It is. Incidentally, as the copper-silver alloy particles, those containing metal particles other than copper and silver may be used,
Specifically, Fe, Co, and Ni may be contained in a total amount of 10% by weight or less.

Further, a binder may be blended in the conductor wiring layer of the wiring board of the present invention in order to bond the copper-silver alloy particles. In this regard, glycol-based resins such as cellulose-based and polyethylene glycol are preferably used, but the above-described thermosetting resins and the like can also be used. As the amount of the binder increases, it tends to be interposed between the particles to increase the contact resistance.
It is desirably 2 parts by weight or less, especially 1 part by weight or less, based on parts by weight.

The exposed surface of the conductor wiring layer of the wiring board of the present invention has excellent corrosion resistance of nickel, gold, etc.
In addition, a metal having excellent bonding properties with electronic components such as semiconductor elements and connectivity with a wiring layer of an external electric circuit board is formed in a thickness of 1 to 20 μm by plating so that the conductive wiring layer is oxidized. Corrosion can be effectively prevented, and electrical connection of the conductor wiring layer to an electric component or an external electric circuit board can be easily and firmly made.

According to the method of manufacturing a wiring board of the present invention, first, the above-mentioned thermosetting resin or the organic resin of the thermoplastic resin and, if desired, the above-mentioned filler component are further blended. A slurry is formed by adding and mixing a curing agent and a solvent, and the slurry is formed into a sheet by a doctor blade method, a calender roll method, a rolling method, or the like, thereby producing an insulating substrate. If desired, this is heated and cured to be semi-cured or completely cured. In addition, other than the above, a prepreg or the like can be used as the insulating substrate.

Next, a conductor wiring layer containing a copper-silver alloy is formed on the insulating substrate. The conductor wiring layer may be one or both of a wiring layer formed on the surface of the insulating substrate or between the insulating substrates, a via hole conductor connecting the wiring layers, or both. When the wiring layer is formed, a conductive paste mainly composed of a copper-silver alloy powder is printed on the pattern of the conductive wiring layer by a known printing method such as a screen printing method and a gravure printing method to have a thickness of 10 to 35 μm. A conductor wiring layer is formed. Also, when forming a via-hole conductor,
Via holes and through holes are formed in the insulating substrate, and the holes are filled with a conductive paste.

The conductive paste used at this time has a mean particle size of 3 to 10 μm, particularly 3 to 7 μm, as a solid component.
m, optimally 3-5 μm copper-silver alloy powder and alloy powder 1
The resin binder is contained in an amount of 2 parts by weight or less, particularly 0.05 to 1 part by weight with respect to 00 parts by weight, and further contains a suitable solvent. In some cases, the composition may contain an appropriate curing agent. This copper-silver alloy is preferably made of an approximately spherical copper-silver alloy powder, and is preferably obtained by an atomizing method in terms of high productivity and relatively low cost.

In the case of multi-layering, a plurality of insulating substrates each having a conductor wiring layer formed by a conductor paste are laminated and pressure-bonded at a pressure of 30 kg / cm ² or less. This crimping is performed in a state where the conductor wiring layer is softened, and when the resin binder is a thermosetting resin, the insulating substrate can be adhered by laminating and crimping in a semi-cured state. An adhesive may be interposed between the substrates.

According to the present invention, the conductor wiring layer in the wiring board thus manufactured is 40 kg / cm.
² above, it is particularly desirable to apply a 60 kg / cm ² or more pressure, thereby to deform at the contact portion between a copper silver alloy powder of the conductive wiring layer, joining between particles in a form close to the surface contact Can be.

As a method of applying a pressure of 40 kg / cm ² or more to the conductor wiring layer, a wiring board on which the conductor wiring layer is formed is pressurized by a press or the like, It may be performed by a press machine.

In the wiring board manufactured as described above, a thin resin film exists on the surface of the metal powder due to the resin contained in the wiring layer, or the thin metal film is oxidized by the oxygen in the atmosphere. A film is formed.

Therefore, according to the present invention, the resistance of the wiring layer is reduced by applying a pulse current to the conductor wiring layer in the wiring board manufactured as described above. When a pulse current is applied to this wiring layer, a plasma discharge occurs between the metal particles. The plasma removes oxide films and deposits on the surface of the metal particles, resulting in a so-called welded state, whereby the metal particles can come into contact with each other without inclusions that impede the conductivity. It is possible to form a low-resistance wiring layer that has not been achieved only by itself without adversely affecting the surrounding insulating layer.

The application of the pulse current is desirably performed by pressing a plate electrode against the substrate on which the wiring layer is formed at a pressure of 10 kg / cm ² or more. Further, it can be performed simultaneously with the pressurizing treatment.

The optimum conditions for the applied pulse current are as follows:
Current density is 1 to 2000 A / cm ² , pulse width is 0.0
1 to 1000 msec. If the current density is lower than 1 A / cm ² , it is difficult to remove the oxide film or resin existing at the interface between the metal powders without welding, and if the current density exceeds 2000 A / cm ² , This is because heat may be generated and the insulating substrate may be damaged. Further, it is preferable that the energizing time of one pulse be 3 seconds or less. The pulse current is preferably applied for 5 seconds to 5 minutes, particularly for 10 seconds to 2 minutes.

It is desirable that the pulse current is a rectangular wave. Although a sine wave or the like is used, a rectangular wave is most effective. Further, it is desirable that the pulse current is a DC pulse. The reason is that a rectangular wave is more likely to cause discharge between particles than a sine wave, has a higher surface cleaning effect, and a pulse current is less likely to cause dirt or the like to adhere to a once-cleaned particle surface than to an alternating current. is there.

Further, after the application of the pulse current, the conductor layer is subjected to a heat treatment by energization, whereby the resistance of the wiring layer can be further reduced. The energization process
A direct current or an alternating current having a current density of 1 to 4000 A / cm ² may be used, and an appropriate heating temperature in energization is in a range of 100 to 350 ° C. If the temperature at this time is lower than 100 ° C., the effect of lowering the electric resistance is small, and if it is higher than 350 ° C., the resin constituting the insulating layer and the conductor wiring layer may be decomposed. The contact heating between the metal powders generates heat by the energization heating, so that the bonding force between the powders can be further increased.

Further, the energization heating can be performed simultaneously with the application of the above-described pulse current. Specifically, when a waveform obtained by combining a DC pulse current and a DC current, that is, when a current having a rectangular waveform at the top of the DC current waveform is applied, the action of energization heating and the discharge welding action of pulse current application are simultaneously performed. Can be added.

By controlling the pulse current applied to the conductor wiring layer, the specific resistance is 7 × 10 ⁻⁵ Ω · cm or less, especially 4.0 × 10 ⁻⁵ Ω · cm when the silver content is 5% by weight or less. The following resistance reduction can be realized. Furthermore, according to the present invention, the wiring board manufactured by the above-described manufacturing method can be used, for example, in a comb-tooth pattern having a line width of 0.5 mm and a gap of 0.4 mm at 5% relative humidity at 130 ° C. and 85% relative humidity.
The insulation resistance after applying a DC voltage of 100 hours for 1 hour is 1 × 10 ¹³
Ω-cm or more, especially 4.0 × at a silver content of 30% by weight or less.
It is possible to provide a highly reliable wiring board which exhibits excellent migration resistance of 10 ¹³ Ω-cm or more, and which can meet the demand for ultra-fine and fine conductor wiring layers in the wiring board. it can.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Substantially spherical silicon oxide 70 having an average particle size of about 5 μm
A slurry was prepared by using 30% by volume of imide resin and 30% by volume of imide resin, and the slurry was applied to a carrier sheet by a doctor blade method, and was applied at a temperature of 50 ° C. to 60%.
After drying for 120 minutes, an insulating substrate having a thickness of 120 μm was prepared.

Next, 99.8 parts by weight of a copper-silver alloy powder having an average particle size and a silver content shown in Table 1, 0.2 parts by weight of cellulose, and 10 parts by weight of 2-octanol as a solvent were provided on the surface of the insulating substrate. A conductive paste was prepared by mixing the above-mentioned parts and a comb-tooth pattern having a line width of 0.5 mm and a gap of 0.4 mm was printed by a screen printing method. In addition, a through-hole having a diameter of 0.1 mm was formed in a part, and the paste was filled in the through-hole.

Next, eight insulating layers on which the conductor wiring layers were formed as described above were prepared, aligned, and laminated and pressed. Then, the laminate was set in a press machine, and a pressure of 50 kg / cm ² was applied. Further 120
C. to remove the organic solvent in the paste.

A pulse current was applied to the obtained wiring board at the extremes of the conductor wiring layer at the current density and pulse width shown in Table 1 for 30 seconds. Note that the interval between the pulses was the same as the pulse width. Also, for some substrates,
Electric heating was performed under the conditions shown in Table 1.

Then, the volume resistivity of the conductor wiring layer in the wiring board after these treatments and the insulation resistance after applying a 5V DC voltage at 130 ° C. and 85% relative humidity for 100 hours were measured. 1 is shown. Further, the contact state of the copper-silver alloy powder in the conductor wiring layer was observed with a scanning electron microscope photograph to confirm the presence or absence of welding.

[0042]

[Table 1]

As is clear from the results in Table 1, according to the present invention, the samples in which the contact portions of the copper-silver alloy powder were welded by appropriate application of the pulse current were all less than 7 × 10 ⁻⁵ Ω-cm. It exhibited excellent conductivity, and exhibited a high resistance value of 1 × 10 ¹³ Ω-cm or more between wirings even when held in a high-temperature and high-humidity atmosphere for a long time, and exhibited excellent migration resistance.

In the sample in which the contact portion of the copper-silver alloy powder was welded, the sample N having a silver content of less than 1% by weight was used.
In the case of Sample No. 6, sample N had a large specific resistance and exceeded 50% by weight.
In o.25, the resistance was 1 × 10 ¹³ due to migration.
It became smaller than Ω-cm, and the reliability decreased. Regarding the migration resistance, when the silver content is 30% by weight or less, the resistance after the high-temperature and high-humidity test is 4.0 × 10 ¹³ Ω.
-Cm or better was achieved. Further, Samples Nos. 1 to 20 having an average particle diameter of the alloy powder smaller than 3 µm and Samples Nos. 20 to 22 larger than 10 µm all have a specific resistance of 7.0.
It was larger than × 10 ⁻⁵ Ω · cm.

[0045]

As described above in detail, according to the wiring board of the present invention, the conductor wiring layer is formed of a copper-silver alloy powder, and a pulse current is applied to remove the resin and oxide on the powder surface. Since the contact portion between the powders can be welded, the specific resistance of the conductor wiring layer can be significantly reduced. Further, the use of a copper-silver alloy as the conductivity results in excellent migration resistance. As a result, a highly reliable wiring board that can sufficiently cope with the miniaturization and high density of the wiring layer and can meet the demands for ultrafineness and precision can be manufactured.

Claims (3)

(57) [Claims] An average particle size of 1 to 50% by weight of silver and 50 to 99% by weight of copper on a surface and / or inside of an insulating substrate containing at least an organic resin.
What is claimed is: 1. A wiring board comprising a conductor wiring layer containing copper-silver alloy powder having a thickness of 0 μm, wherein a contact portion between the alloy powders of the conductor wiring layer is welded. 2. The method according to claim 1, wherein the surface and / or the inside of the insulating substrate containing at least an organic resin comprises 1-50% by weight of silver and 50-9% of copper.
After forming a conductive wiring layer containing copper-silver alloy powder having an average particle size of 9 to 10% by weight and having a mean particle size of 3 to 10 μm, a pulse current is applied to the conductive wiring layer to form a contact portion between the copper-silver alloy powder. A method for manufacturing a wiring board, comprising welding. 3. The current density of the applied pulse current is 1 to 20.
00 A / cm ² , pulse width of 0.01 to 1000 mse
c. 3. The method for manufacturing a wiring board according to claim 2, wherein: