JP3092836B2 - Conductive composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive composition for forming an electromagnetic wave shielding layer on a printed circuit board, for example.

[0002]

2. Description of the Related Art Conventionally, as a method for preventing unnecessary radiation of electromagnetic waves on a printed circuit board, it is known to form a shield layer using a conductive paste. A printed circuit board on which this shield layer is formed (hereinafter, abbreviated as a shield board) is formed by forming a circuit pattern on a conventional paper phenol resin substrate or a glass epoxy resin substrate, and then forming an insulating layer, a shield layer, and an overcoat layer. Are sequentially formed. At this time, an insulating layer is formed in a portion of the circuit pattern made of the copper foil except for a part of the ground circuit, and the shield layer is directly electrically connected to the ground circuit portion from which the insulating layer has been removed. The reliability of the connection between the ground portion and the shield layer is an important point of the shield substrate.

On the other hand, a material for forming the shield layer has a high conductivity for exhibiting excellent electromagnetic wave shielding properties, and a property that migration does not easily occur for ensuring electrical insulation with a circuit pattern. ,
Further, in order to ensure the reliability of the electrical connection with the ground circuit, it is necessary to use a material having high adhesion to the copper foil.

As a conductive composition for forming a shield layer used for the shield substrate, a copper paste is widely used.
JP-A-2-34673 and JP-A-2-34673
No. 163150 is known. These are mainly composed of copper powder and resole type phenol resin, and use additives such as organic fatty acids or their metal salts and aliphatic amines, organic zirconate compounds, carbon powder, etc. In order to enhance the adhesion, a bisoxaline compound or the like is added.

[0005]

By the way, the copper paste used for the shield layer of the above-mentioned shield substrate has a relationship in which the conductivity and the adhesion are opposite, and the specific resistance is 10 ^−4.
When the conductivity of Ω · cm or less was to be ensured, the adhesion on the copper foil was reduced, and when the adhesion was improved, the specific resistance tended to increase.

Therefore, in the conventional formation of the shield layer, the base copper foil is blown with hot air of, for example, about 150 ° C. for 30 minutes before the formation of the copper paste layer in order to prevent a decrease in adhesion due to securing conductivity. Blackening is performed by spraying to the extent of oxidation.

However, since the base copper foil is heated and oxidized, there are problems such as damage to the base and deformation of the substrate. Further, before the normal printing process, polishing and acid cleaning are required for removing foreign substances, and the addition of the oxidation process has a problem that productivity is reduced due to an increase in man-hours.

The present invention has been made in view of the above problems, and has as its object to provide a conductive composition which can easily form a shield layer having high adhesion and excellent conductivity. is there.

[0009]

The conductive composition according to the present invention comprises a mixed resin composition comprising three components of a resole type alkylphenol resin, a butyl etherified melamine resin and a bisphenol A type epoxy resin, and copper powder. It is a thing.

[0010] The conductive composition according to the second aspect is the first aspect.
In the above described conductive composition, the mixed resin composition has a weight ratio of the resole type alkylphenol resin to the bisphenol A type epoxy resin of 5: 5 to 9: 1.

The conductive composition according to the third aspect is the first aspect.
In the above-described conductive composition, the mixed resin composition has a weight ratio of the resole type alkylphenol resin to the butyl etherified melamine resin of 5: 5 to 9: 1.

The conductive composition according to the fourth aspect is the first aspect.
In the above conductive composition, the mixed resin composition has a weight ratio of the butyl etherified melamine resin to the bisphenol A type epoxy resin of 5: 5 to 9: 1.

The conductive composition according to the fifth aspect is the first aspect.
In the conductive composition described above, the mixed resin composition has a weight ratio of the resole type alkylphenol resin, the butyl etherified melamine resin, and the bisphenol A type epoxy resin of 50 to 90: 5 to 45: 1 to 25. It is.

The conductive composition according to the sixth aspect is the first aspect.
6. The conductive composition according to any one of Items 5 to 5, wherein the copper powder has a dendritic shape and an average particle size of 1 to 50 μm.

[0015]

The conductive composition according to the first aspect of the present invention comprises a mixed resin composition comprising three components of a resole type alkylphenol resin, a butyl etherified melamine resin and a bisphenol A type epoxy resin, and copper powder, so that the conductive composition can be used on a printed circuit board. The adhesion of the shield layer formed on the substrate is improved.

The conductive composition according to the second aspect is the first aspect.
In the conductive composition described above, the resole type alkylphenol resin and the bisphenol A type epoxy resin are mixed at a weight ratio of 5: 5 to 9: 1, so that the adhesion of the shield layer formed on the printed circuit board is improved. .

The conductive composition according to the third aspect is the first aspect.
In the conductive composition described above, the resole type alkylphenol resin and the butyl etherified melamine resin are mixed at a weight ratio of 5: 5 to 9: 1, so that the adhesion of the shield layer formed on the printed circuit board is improved.

The conductive composition according to the fourth aspect is the first aspect.
In the conductive composition described above, the butyl etherified melamine resin and the bisphenol A type epoxy resin are mixed at a weight ratio of 5: 5 to 9: 1, so that the shield layer having excellent conductivity has a high adhesion and a printed circuit. It is formed on a substrate.

The conductive composition according to the fifth aspect is the first aspect.
In the conductive composition described above, a resole type alkylphenol resin, a butyl etherified melamine resin, and a bisphenol A type epoxy resin are mixed in a weight ratio of 50 to 9;
Since the mixing is performed at 0: 5 to 45: 1 to 25, the shield layer having excellent conductivity is formed on the printed circuit board with high adhesion.

The conductive composition according to the sixth aspect is the first aspect.
5. In the conductive composition according to any one of the above items 5, since a copper powder having a dendritic shape and an average particle diameter of 1 to 50 μm is mixed, the shield layer having excellent conductivity and stable properties has high adhesion. Formed easily on printed circuit boards by force.

[0021]

EXAMPLES Hereinafter, one example of the conductive composition of the present invention will be described in the process of manufacturing a printed circuit board.

First, on a circuit previously formed by etching a metal layer made of copper on a paper phenolic resin substrate, for example, a UV-curable solder resist USR-2G is used.
(Manufactured by Tamura Kaken Co., Ltd.) is screen-printed with a 250-mesh screen, and cured by exposing to light in an ultraviolet curing furnace.

Further, on this upper surface, for example, a UV curable interlayer insulating material USR-11G (manufactured by Tamura Kaken Co., Ltd.) is screen-printed on a two-layer 200-mesh screen, and each is exposed and cured in an ultraviolet curing furnace to form an insulating layer. To form

Next, a pattern is formed by screen-printing the conductive composition on, for example, a 180-mesh screen.
It is cured at 160 ° C. for 30 minutes by a hot air circulation type drier to form a shield layer.

Further, USR-11G, for example, is screen-printed on the pattern with a 200-mesh screen as an overcoat, and is cured by exposure in an ultraviolet curing furnace.
An overcoat layer is formed, and a printed circuit board is formed.

On the other hand, as the conductive composition, as a copper powder, 80 parts by weight of a dendritic copper powder having an average particle diameter of 10 μm, and as a resole-type alkylphenol resin in the mixed resin composition, a titanol 4010 (manufactured by Hitachi Chemical Co., Ltd.) ) To 12
Parts by weight, as a butyl etherified melamine resin, 4.8 parts by weight of melan 27 (manufactured by Hitachi Chemical Co., Ltd.) which is an iso (iso) -butyl etherified melamine resin, and as a bisphenol A type epoxy resin, an epicoat 1001 having a molecular weight of 900 (oil) Shell Epoxy Co., Ltd.) in an amount of 3.2 parts by weight.

Further, aminophenol was used as an additive, and the total weight of the mixed resin composition and copper powder was 100%.
Mix 2 parts by weight with respect to parts by weight. In addition, ethyl carbitol as a solvent is added to these components and pre-kneaded, and then dispersed by a dispersing machine such as a three-roll mill to prepare a conductive composition.

The resole-type alkylphenol resin has a reducing atmosphere in the copper powder dispersion system and has a function of preventing oxidation of the copper powder surface. Furthermore, since the resole type alkylphenol resin is a resole type,
Since the condensation state at the time of curing is network-like and the reactivity is good, and it has an alkyl group, rapid curing is suppressed, it has stable properties with little change over time, and greatly contributes to the improvement of adhesion.

The resole type alkylphenol resin includes ortho (o) -cresol, para (p) -cresol, meta (m) -cresol, p-isopropylphenol, p-tert (tert) butylphenol,
An alkylphenol such as p-tert-amylphenol or p-tert-octylphenol is subjected to addition condensation of formalin in an alkaline atmosphere.

The butyl etherified melamine resin is
Because it is butyl etherified, the compatibility with other resins and the solubility in solvents are good, and the high crosslinking density of the melamine resin promotes the curing of the conductive composition, and furthermore, the It also has the function of improving adhesion.

The butyl etherified melamine resin is a linear (n) -butyl etherified melamine resin, is
Any of o-butyl etherified melamine resins may be used.
In addition, these melamine resins are obtained by condensing formalin with melamine and etherifying the obtained methylol melamine with n-butanol or iso-butanol. Is desirable.

On the other hand, since the bisphenol A type epoxy resin has a linear structure, it has a function of mainly improving the toughness of the cured coating film of the conductive composition and a function of improving the adhesion to the copper foil. In addition to having a benzene ring, it has a function of improving heat resistance. As the bisphenol A type epoxy resin, those having a molecular weight of 900 to 4000 are more preferable. When the molecular weight is less than 900, the toughness of the cured coating film cannot be obtained, and when the molecular weight exceeds 4,000, the compatibility with other resins deteriorates.

The weight ratio of the resole type alkylphenol resin to the other two components, butyl etherified melamine resin and bisphenol A type epoxy resin, is as follows:
It is desirable to use 5: 5 to 9: 1. If the weight ratio of the resole type alkylphenol resin is less than 5: 5, the conductivity tends to decrease, and if it exceeds 9: 1, the adhesion to the copper foil decreases.

Further, it is desirable to use the butyl etherified melamine resin and the bisphenol A type epoxy resin in a weight ratio of 5: 5 to 9: 1. Similarly, when the weight ratio of the butyl etherified melamine resin is less than 5: 5, the conductivity becomes low. This is because the tendency of the property to decrease becomes stronger, and if it exceeds 9: 1, the adhesion to the copper foil decreases.

The weight ratio of the mixed resin composition containing three components to the copper powder is desirably 1: 9 to 3: 7. When the weight ratio of the mixed resin composition is less than 1: 9, the function of mixing the copper powder and the antioxidant function are reduced, and 3:
If it exceeds 7, the specific resistance of the conductive composition increases, and there is a problem that the electrical characteristics are impaired.

On the other hand, the copper powder has an average particle size of 1 to 50 μm.
And a dendritic one is desirable. High conductivity can be obtained from the particle size and shape. Those having an average particle size of less than 1 μm have a strong tendency to be oxidized, while those having an average particle size of more than 50 μm cause clogging or the like during screen printing.

Further, when the shape of the copper powder is spherical or flake-like, the cost for processing to maintain the shape is high, and the conductivity is also inferior to that of dendrites. Furthermore, in consideration of dispersibility and stability, this dendritic copper powder is used for dispersants such as higher fatty acids such as stearic acid, silane coupling agents, titanate coupling agents, aluminum coupling agents, and benzotriazoles. It may be one treated with an antioxidant or the like.

Various additives having functions as a dispersing aid, a reducing agent, an antioxidant and the like may be added to the conductive composition. Further, these additives include, for example, a saturated fatty acid, an unsaturated fatty acid, an aliphatic oxyacid, an aromatic oxyacid or a metal salt thereof, such as an aliphatic amine,
Alkanolamines, aminophenols and the like are used. Furthermore, these additives reduce the adhesion to the copper foil when the amount added is too large, so that in consideration of conductivity and adhesion, the total weight of the mixed resin composition and copper powder is 100 parts by weight. Preferably, the amount is 0.5 to 3 parts by weight.

It is preferable that an organic solvent is appropriately added to the conductive composition in consideration of workability and the like. As such an organic solvent, a carbitol type or a cellosolve type having a high boiling point is desirable in consideration of an increase in the viscosity of the paste due to evaporation of the solvent during printing.

Next, the operation of the above embodiment will be described.

A printed circuit board, which is a test piece, is prepared by blending a predetermined amount of various materials by a manufacturing method described later, and various experiments are performed by measuring various physical properties of the test piece.

The test piece was prepared by first using 80 parts by weight of a dendritic copper powder having an average particle diameter of 10 μm as copper powder, and using Hitachil 4010 (Hitachi Chemical Co., Ltd.) as a resole-type alkylphenol resin in the mixed resin composition. Butyl etherified melamine resin, iso-
Melan 27 (manufactured by Hitachi Chemical Co., Ltd.), which is a butyl etherified melamine resin, and Epicoat 1001 (manufactured by Yuka Shell Epoxy Co., Ltd.) having a molecular weight of 900 as a bisphenol A type epoxy resin were added in predetermined amounts as shown in Table 1. Mix.

Further, aminophenol was used as an additive, and 2 parts by weight was added to 100 parts by weight of the total weight of the mixed resin composition and the copper powder. In addition, ethyl carbitol was added as a solvent to these components and preliminarily kneaded, and then dispersed using a three-roll mill to prepare a conductive composition.

Then, a UV curable solder resist USR-2G (manufactured by Tamura Kaken Co., Ltd.) is screened with a 250 mesh screen on a circuit formed by etching a metal layer made of copper on a paper phenol resin substrate in advance. Printed, 120W /
Cures at 6 cm / min.

Further, two layers of a UV-curable interlayer insulating material USR-11G (manufactured by Tamura Kaken Co., Ltd.)
Screen printing is performed using a mesh screen, and each is cured at 120 W / cm and 6 m / min in a three-lamp type ultraviolet curing furnace to form an insulating layer.

Next, the conductive composition prepared above was mixed with 180
Screen printing with mesh screen, 1mm width x 5
A pattern for measuring physical properties of four wires having a length of 0 mm is formed and cured at 160 ° C. for 30 minutes by a hot air circulation type dryer to form a shield layer.

Further, USR-11G was screen-printed as an overcoat on the four-line pattern using a 200-mesh screen, and 120 U in a three-lamp type ultraviolet curing furnace.
Experiment 1 was conducted by curing at W / cm and 6 m / min to form an overcoat layer, forming a printed circuit board as a test piece, and measuring each physical property. Table 1 shows the results.

As comparative examples, Table 1 shows phenolite 5010 (manufactured by Dainippon Ink Co., Ltd.), butyl etherified melamine resin and bisphenol A type epoxy resin as resole type phenol resins instead of the mixed resin composition. A test piece was prepared using the conductive composition prepared in a predetermined amount in the same manner as in each experiment, and various physical properties were measured.

[0049]

[Table 1] The resistance value, which is a physical property, is obtained by measuring the resistance value of each of the four lines of each test piece using a digital multimeter and calculating the average value.

As for the adhesion, the printed circuit board as each test piece was placed on the copper foil surface of the paper phenolic resin substrate so that only the 40 mm × 50 mm rectangular pattern portion on the copper foil surface was removed from the insulating layer. It is manufactured by forming an insulating layer.

Next, two types of test pieces were prepared, one washed with dilute sulfuric acid and one oxidized at 160 ° C. for 30 minutes in a hot air circulating drier. Further, a shield layer is formed on each test piece, and an overcoat layer is further formed thereon to obtain a test piece. The shield layer formed on the copper foil surface of this test piece is directly grounded.
On a rectangular pattern for evaluation of adhesion of 0 mm x 50 mm,
100 squares of 1 mm x 1 mm are made with a jig such as a blade, an adhesive tape is attached, and the adhesive tape is vigorously peeled off. At this time, the adhesion was evaluated by the number of squares remaining in the coating film.

Further, regarding the solder heat resistance, after measuring the resistance value of each test piece, immersing it in the solder layer at 260 ° C. for 10 seconds and measuring the resistance value again, the resistance value before and after the solder immersion was measured. The rate of change was determined and used as a guide.

From the results shown in Table 1, the weight ratio of the resole type alkylphenol resin to the other two components, the butyl etherified melamine resin and the bisphenol A type epoxy resin, was calculated as follows.
5: 5 to 9: 1, the weight ratio of the butyl etherified melamine resin and the bisphenol A type epoxy resin is mixed at 5: 5 to 9: 1, and the mixed resin composition containing three components and copper powder. From 1: 9 to 3:
7 to form a printed circuit board by forming a shield layer using this conductive composition, so that a shield layer having excellent conductivity and heat resistance can be attached to the substrate with high adhesion. It can be seen that it can be formed.

Further, it can be seen that high adhesion can be obtained without oxidizing the copper foil before forming the shield layer,
The step of oxidizing the copper pad before forming the shield layer can be omitted, and the manufacturing process can be simplified to improve the manufacturability, and the manufacturing apparatus can be downsized and the manufacturing cost can be reduced.

In the above embodiment, the shield layer is formed by screen printing, but the same effect can be obtained by any forming method.

[0056]

According to the first aspect of the present invention, the conductive composition comprises a mixed resin composition comprising three components of a resole type alkylphenol resin, a butyl etherified melamine resin and a bisphenol A type epoxy resin, and copper powder, so that a printed circuit is provided. The adhesion of the shield layer formed on the substrate can be improved.

The conductive composition according to the second aspect is the first aspect.
In the conductive composition described above, the resole-type alkylphenol resin and the bisphenol-A-type epoxy resin are mixed at a weight ratio of 5: 5 to 9: 1, so that the adhesion of the shield layer formed on the printed circuit board can be improved. .

The conductive composition according to the third aspect is the first aspect.
In the conductive composition described above, the resole type alkylphenol resin and the butyl etherified melamine resin are mixed at a weight ratio of 5: 5 to 9: 1, so that the adhesion of the shield layer formed on the printed circuit board can be improved.

The conductive composition according to the fourth aspect is the first aspect.
In the conductive composition described above, the butyl etherified melamine resin and the bisphenol A type epoxy resin are mixed at a weight ratio of 5: 5 to 9: 1, so that the shield layer having excellent conductivity has a high adhesion and a printed circuit. It can be formed on a substrate.

The conductive composition according to the fifth aspect is the first aspect.
In the conductive composition described above, a resole type alkylphenol resin, a butyl etherified melamine resin, and a bisphenol A type epoxy resin are mixed in a weight ratio of 50 to 9;
Since the mixing ratio is 0: 5 to 45: 1 to 25, a shield layer having excellent conductivity can be formed on the printed circuit board with high adhesion.

The conductive composition according to the sixth aspect is the first aspect.
5. In the conductive composition according to any one of the above items 5, since a copper powder having a dendritic shape and an average particle diameter of 1 to 50 μm is mixed, the shield layer having excellent conductivity and stable properties has high adhesion. Can be easily formed on a printed circuit board by force.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI H01B1 / 22 H01B1 / 22 A (56) References JP-A-3-77202 (JP, A) JP-A-1-265403 ( JP, A) JP-A-51-61545 (JP, A) JP-A-4-12595 (JP, A) JP-A-62-160603 (JP, A) JP-A-5-325635 (JP, A) JP JP-A-5-20923 (JP, A) JP-A-7-41706 (JP, A) JP-A-61-211378 (JP, A) JP-A-2-34673 (JP, A) JP-A-62-147701 (JP) (A) JP-A-61-234501 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 63/02 C08L 61/28 C08K 3/08 C08G 59/62 C09D 5/24 H01B 1/22

Claims (6)

(57) [Claims] 1. A conductive composition comprising a mixed resin composition comprising three components of a resole type alkylphenol resin, a butyl etherified melamine resin and a bisphenol A type epoxy resin, and copper powder. 2. The conductive composition according to claim 1, wherein the mixed resin composition has a weight ratio of the resole type alkylphenol resin to the bisphenol A type epoxy resin of 5: 5 to 9: 1. 3. The conductive composition according to claim 1, wherein the weight ratio of the resole-type alkylphenol resin to the butyletherified melamine resin is 5: 5 to 9: 1. 4. The conductive composition according to claim 1, wherein the weight ratio of the butyl etherified melamine resin to the bisphenol A type epoxy resin is 5: 5 to 9: 1. 5. A mixed resin composition comprising: a resole type alkylphenol resin; a butyl etherified melamine resin;
The weight ratio with the bisphenol A type epoxy resin is 50 to 9
The conductive composition according to claim 1, wherein the ratio is 0: 5 to 45: 1 to 25. 6. The copper powder has a dendritic shape and an average particle size of 1
The conductive composition according to any one of claims 1 to 5, wherein the thickness is from 50 to 50 m.