JP4589785B2 - Conductive paste composition and printed wiring board - Google Patents

Description

  The present invention relates to a novel conductive paste composition and a printed wiring board. Preferably, the present invention relates to a conductive paste composition particularly suitable for forming an electrode bump used for interlayer connection of a multilayer printed wiring board and a printed wiring board using the same.

  Conventionally, conductive paste compositions have been used in many applications such as for IC circuits, conductive adhesives, and electromagnetic wave shields in the electronics field. Particularly recently, a first substrate provided with a conical conductive bump made of a conductive paste at a predetermined position on at least one surface, and a second substrate provided with a wiring pattern on at least one surface, The surface provided with the conductive bump and the surface provided with the wiring pattern are opposed to each other, and an insulating layer is disposed between the first substrate and the second substrate to form a laminate. In addition, a method of manufacturing a printed wiring board is proposed in which a conductive wiring portion is formed by penetrating the bumps in the thickness direction of the insulating layer by laminating and pressing the laminated body (Japanese Patent Laid-Open No. 6-350258). ).

  Also, a printed wiring having a through-type conductive wiring section that has good prepreg penetrability, does not generate cracks when penetrating and pressing, and can create a bump having a high adhesion between the bump and the wiring pattern after penetrating. In the production of plates, a conductive paste comprising a melamine resin, a phenol resin, an epoxy resin, a conductive powder and a solvent is provided as a conductive paste having a high yield and good connection reliability. A conductive paste composition for printed wiring board interlayer connection has been proposed in which the softening point of the resin is 80 ° C. or higher and 130 ° C. or lower (Japanese Patent Laid-Open No. 2002-270033).

  Also, at least one of melamine resin, phenol resin, and epoxy resin is required to provide an adhesive paste composition for interlayer connection of printed wiring boards that can form bumps without high hardness, cracks, and poor connection with the wiring pattern. Proposal to use a conductive paste composition for printed wiring board interlayer connection comprising a resin selected from one and a conductive powder and a dihydric alcohol and / or a trihydric alcohol having a boiling point of 180 ° C. or higher (Japanese Patent Laid-Open No. 2003-77337).

  In addition, according to Japanese Patent No. 3588400, as an example of providing a thermosetting conductive resin composition capable of washing an apparatus, a jig and a container with water after screen printing, a water-soluble thermosetting resin, conductive particles, A conductive resin composition containing a dihydric alcohol is known.

  According to Japanese Patent Laid-Open No. 9-286924, as in Patent No. 3588400, as a conductive resin composition capable of washing a screen plate after printing with water, a water-soluble thermoplastic resin, an average particle size of 0.05 to 50 μm Conductive particles containing dihydric alcohol are known.

  JP-A-2001-11388 discloses a multilayer capacitor electrode paste composition containing a water-soluble resin and glycols that can wash a plate used for printing with water.

According to Japanese Patent Application Laid-Open Nos. 2003-331648 and 2004-265826, a metal paste that can be fired at a low temperature is a metal containing an organometallic compound and an alcohol compound of a Group 3 to 15 metal of the periodic table, preferably a glycol. Pastes are known.
JP-A-6-350258 JP 2002-270033 A JP 2003-77337 A Japanese Patent No. 3588400 JP-A-9-286924 JP 2001-11388 A JP 2003-331648 A JP 2004-265826 A

  When forming electrode bumps by the method described in JP-A-6-350258, a conductive paste composition as disclosed in JP-A-2002-270033 and JP-A-2003-77337. When a conductive paste composition is applied once, the bump height sufficient to penetrate the insulating layer cannot be obtained by a single application operation of the conductive paste composition, so it is necessary to perform overprinting by applying the conductive paste composition multiple times. was there. In particular, the paste is used to prevent the bump shape from being excessively sharpened in order to prevent bending and chipping of the bumps when penetrating through the insulating layer and during pressing. Tended to increase.

  The techniques described in Japanese Patent No. 3588400, Japanese Patent Application Laid-Open No. 9-286924 and Japanese Patent Application Laid-Open No. 2001-11388 use a water-soluble resin, and Japanese Patent Application Laid-Open Nos. 2003-331648 and 2004-265826. The technique described in the publication uses a fired-type metal paste, which is a water-insoluble, non-fired conductive paste composition as in the present invention, and can be applied in a single coating operation. As far as the present inventors know, a paste composition with which thickness can be obtained has not been obtained conventionally.

  The present invention intends to provide a solution to the above problem by forming a conductive paste composition with predetermined components.

  Therefore, the conductive paste composition according to the present invention is characterized by comprising a phenol resin, a melamine resin, a conductive powder, a solvent and water.

  Such a conductive paste composition according to the present invention includes, as a preferred embodiment, one further containing a pigment, preferably an extender pigment.

  Such a printed wiring board according to the present invention is characterized by using the conductive paste composition.

  According to the conductive paste composition of the present invention, a coating film having a sufficient thickness can be formed by a single coating operation.

  Therefore, a bump having a sufficient height can be formed with a smaller number of coatings than in the past.

  Therefore, the number of overprints of the conductive paste composition can be reduced, and productivity can be improved. Moreover, since the electrically conductive paste composition by this invention is a non-baking type thing, it is not necessary to perform a baking operation.

<Conductive paste composition>
The conductive paste composition according to the present invention is a conductive paste composition comprising a phenol resin, a melamine resin, a conductive powder, a solvent, and water. Here, “consisting of” does not exclude a conductive paste composition in which other components other than the above essential components (ie, phenol resin, melamine resin, conductive powder, solvent and water) coexist. That is, the conductive paste composition according to the present invention includes both a conductive paste composition composed of only the above essential components, and a conductive paste composition comprising the above essential components and other components other than these essential components. Is included. In the above description, “conductive” means that the volume resistance value is at least 1 × 10 ⁻³ cm · Ω or less.

  The conductive paste composition according to the present invention preferably has a viscosity of 150 to 500 Pa · s, particularly 200 to 400 Pa · s. This viscosity is measured by a spiral viscometer manufactured by Malcolm at 10 rpm / min and 25 ° C.

  The conductive paste composition according to the present invention preferably has a thixo index of 0.75 to 1.0, particularly 0.80 to 0.95. The thixo index was calculated from the viscosity of the conductive paste measured at 10 rpm / min, 5 rpm / min, and 25 ° C. using a spiral viscometer manufactured by Malcolm Co., Ltd. (the viscosity value at 5 rpm / viscosity at 10 rpm). Value) / log [10 (rpm) / 5 (rpm)]. The thixo index is an index representing the property that the apparent viscosity increases when left standing, and the apparent viscosity decreases when mixed vigorously, thereby facilitating coating.

(1) Phenol resin As the phenol resin used in the present invention, any of novolak type and resol type can be used, and in particular, phenol, cresol, xylenol, polyparavinylphenol, p-alkylphenol, chlorophenol. Examples thereof include resins obtained by adding and condensing aldehydes such as formalin and furfural to those having a phenolic hydroxyl group such as bisphenol A, phenolsulfonic acid, and resorcin. Of these, polyparavinylphenol is particularly preferred.

(2) Melamine resin Examples of the melamine resin used in the present invention include methylol melamine and alkylated melamine.

(3) Conductive powder Examples of the conductive powder used in the present invention include various conductive fine powders such as silver powder, gold powder, copper powder, nickel powder, platinum powder, palladium powder, solder powder, and alloy powders of the above metals. A metal powder such as can be used. Two or more kinds of these conductive powders can be used in combination. Moreover, electroconductive powder other than a metal, for example, carbon powder, can also be used. The conductive powder may be surface-treated.

  The form and size of the conductive powder are arbitrary as long as the object of the present invention is not violated. In the present invention, for example, dendritic, flaky, spherical, and flaky forms, particularly preferably a mixture of flaky and spherical forms can be used. The average particle diameter is preferably 0.5 to 10 μm, particularly 1.0 to 5.0 μm.

(4) Solvent As a solvent used by this invention, the various organic solvent which can form a paste composition with the said phenol resin, melamine resin, and electroconductive powder can be used, for example. Preferred examples of such organic solvents include, for example, butyl carbitol acetate, ethyl acetate, butyl acetate, ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, isopropanol, butanol, terpineol, thixanol, butyl cellosolve acetate, isophorone. A single solvent or a mixed solvent thereof may be mentioned.

(5) Water Any water can be used as long as the object of the present invention can be achieved. For example, tap water or purified water can be used in addition to pure water.

(6) Components other than the above (arbitrary components)
The electrically conductive paste composition by this invention can contain various components as needed. Specific examples of components that can be included as necessary include the following pigments, thixotropy-imparting agents, antifoaming agents, dispersants, rust preventives, reducing agents, and the phenol resins and (Or) Other resin components miscible with the melamine resin (for example, epoxy resin, acrylic resin) and the like can be mentioned.

Pigment The conductive paste composition according to the present invention can contain various organic or inorganic pigments as required, and such pigments reinforce the coating, add functions, and improve workability of the conductive paste composition. It is possible to achieve coloring and increasing the amount.

  In the present invention, extender pigments such as micro silica, calcium carbonate, barium sulfate, magnesium carbonate, alumina and the like alone or a mixture thereof can be used.

(7) Blending ratio The blending ratio of each component in the conductive paste composition according to the present invention is as follows (in the following, the total of resin components means the total amount of phenol resin and melamine resin). However, when a resin other than phenol resin or melamine resin is present, it means the total amount of these resin components).

  The amount of the solvent is preferably 10 to 100 parts by mass, more preferably 20 to 80 parts by mass, and still more preferably 35 to 65 parts by mass with respect to 100 parts by mass of the total resin components.

  The amount of the conductive powder is preferably 300 to 1100 parts by mass, more preferably 500 to 900 parts by mass with respect to 100 parts by mass of the resin component.

  The amount of the pigment is preferably 1 to 30 parts by mass, more preferably 5 to 25 parts by mass with respect to 100 parts by mass of the resin component.

  The ratio of the phenol resin to the melamine resin in the resin component is expressed as a mass ratio, and (phenol resin) / (melamine resin) is preferably 10/90 to 90/10, more preferably 30/70 to 70 /. The range is 30, more preferably 60/40 to 40/60.

  The amount of water is preferably 0.1 to 20 parts by mass, more preferably 3 to 12 parts by mass with respect to 100 parts by mass of the resin component.

(8) Use of conductive paste composition The conductive paste composition according to the present invention has good conductivity, and is printed on a substrate by a known printing method such as a screen printing method or a metal mask printing method. It is possible. Accordingly, the conductive paste composition according to the present invention can be used in a wide range of fields as in the past.

  And since the electrically conductive paste composition by this invention is a thing with a thick coating film thickness per printing operation, it can form a conductive layer of sufficient thickness efficiently.

  Therefore, the conductive paste composition according to the present invention can form bumps with a sufficiently high number of coatings with a smaller number of coatings than in the past, for example, with only one coating cycle, so that productivity can be improved. it can.

<Printed wiring board>
The printed wiring board according to the present invention is characterized by using the conductive paste composition described above.

  Such a printed wiring board according to the present invention includes, as a preferred embodiment, a printed wiring board in which electrical connection between layers is made by bumps formed from the conductive paste composition.

<Example 1 and Comparative Example 1>
The following phenol resin, melamine resin, silver powder, extender pigment, solvent and water were mixed at a mass ratio shown in Table 1 and sufficiently kneaded with three rolls to produce a conductive paste composition according to the present invention. The viscosity and thixo index of this conductive paste composition are as shown in Table 1.

  Screen (stencil) printing was performed using this conductive paste. Specifically, an aluminum metal mask plate with a hole of φ220 μm is used, a urethane resin squeegee with a hardness of 80 ° is used, and the environment is controlled to a temperature of 20 ° C. and a humidity of 50%. Then, printing was performed to form bumps.

The height and shape of the formed bump were evaluated. The results are as described in Table 1.

<Evaluation>
As apparent from Table 1 above, in Example 1, a bump height of 73 μm (bump diameter: 220 μm) can be formed, compared to Comparative Example 1 (bump height: 58 μm, bump diameter: 220 μm). It can be seen that the bump height is dramatically increased to 26%. Also, the bump shape was a conical shape and was good.

Claims (3)

A water -insoluble conductive paste composition comprising a phenol resin, a melamine resin, a conductive powder, a solvent, and water (where the blending ratio of the phenol resin and the melamine resin is expressed in terms of mass ratio) , (Phenol resin) / (melamine resin) is in the range of 10/90 to 90/10. The compounding amount of the conductive powder is 300 to 1100 parts by mass with respect to 100 parts by mass of the total amount of the phenol resin and the melamine resin, and the compounding amount of the solvent is 100 parts by mass with respect to the total amount of the phenol resin and the melamine resin. It is 10-100 mass parts, and the compounding quantity of water is 0.1-20 mass parts with respect to 100 mass parts of total amounts of a phenol resin and a melamine resin . The water-insoluble conductive paste composition according to claim 1, further comprising a pigment, preferably an extender pigment. A printed wiring board, wherein the water-insoluble conductive paste composition according to claim 1 or 2 is used.