JP5426246B2 - Wiring board and manufacturing method thereof - Google Patents

Description

  The present invention relates to a wiring board and a manufacturing method thereof, and more particularly to an improvement of a wiring board for forming a wiring pattern by an ink jet method.

  In recent years, a technique for forming a wiring pattern of a wiring board used in an electronic device or the like by an ink jet method has attracted attention. In this method, ink (paste) in which nano-sized fine conductor particles are dispersed in a predetermined dispersion medium is ejected so as to draw a wiring pattern by an inkjet head, thereby forming a wiring pattern.

  In such an ink-jet wiring pattern forming method, in order to make the wiring pattern formed on the substrate thinner, the advancement of the technology related to the improvement of the control accuracy of the droplet discharge amount and the improvement of the lower ground of the substrate And is important. The improvement of the lower ground is generally performed by plasma processing on the surface of the substrate.

  However, even if the surface of the substrate is improved by plasma treatment, the surface state is only temporarily modified, and the state changes over time. For this reason, when the process of forming the wiring pattern cannot be performed immediately after the surface treatment, the desired thinning may not be achieved, and there is a problem in process reproducibility. .

  Accordingly, it has been proposed to form a porous or microporous coating (hereinafter referred to as a porous coating) on the surface of the substrate (see, for example, Patent Document 1). According to this method, it is possible to prevent the width of the wiring from spreading by causing the paste containing fine particles of the conductor discharged from the ink jet head to penetrate into the pores of the porous coating.

JP 2005-159324 A

  However, in the above prior art, when the pore size of the porous coating is several nanometers or less, the paste containing the conductive particles is fine even when nano-sized particles are used as the conductive particles. The ink cannot enter the hole, and it becomes difficult to sufficiently suppress the spread of the ink. On the other hand, when the pore size increases from sub-micron to micron units, when nano-sized particles are used as the conductor particles, not only the dispersion medium but also the conductor particles penetrate into the pores. become. As a result, the number of particles remaining on the porous coating is reduced and the electrical resistance is increased.

  Furthermore, when sub-micron to micron particles are used as the conductor particles, the number of particles staying on the porous film increases, but the conductor particles exist only on the surface of the porous film. As a result, the bonding strength of the wiring pattern to the substrate decreases. In addition, when the conductor particles are sintered to form a wiring pattern, it is necessary to heat to a higher temperature, which makes manufacturing difficult.

  The present invention has been made in view of the above-described conventional problems, and provides a wiring board having a wiring pattern that is further thinned, suppresses an increase in electrical resistance, and has excellent coupling strength, and a method for manufacturing the same. For the purpose.

In order to achieve the above object, the present invention comprises a base material made of an insulator material,
A porous membrane formed on the surface of the substrate;
A wiring pattern formed on the porous membrane part,
The wiring pattern is composed of first conductor particles having an average particle diameter larger than the average pore diameter of the porous film part and second conductor particles having an average particle diameter smaller than the average pore diameter of the porous film part ,
The first conductor particles are located on the surface of the porous membrane part,
The second conductor particles are located in the gap between the first conductor particles and the inside of the porous membrane part, and bind the first conductor particles to the porous membrane part. A wiring board is provided.

In a preferred embodiment of the wiring board of the present invention, the average particle diameter of the second conductor particles is 30 nm or less, and the volume ratio of the first conductor particles to the second conductor particles is 0.7 to 1.3, and the average pore diameter of the porous membrane portion is 0.01 μm or more and 5 μm or less.

  In another preferred embodiment of the wiring board of the present invention, the first conductor particles and the second conductor particles are gold, silver, copper, platinum, palladium, tungsten, nickel, tantalum, bismuth, lead, indium, tin. And at least one selected from zinc, titanium, aluminum, and iron, and alloys thereof.

  In another preferred embodiment of the wiring board of the present invention, the material of the first conductor particles is different from the material of the second conductor particles.

Further, the present invention includes a step A of forming a porous film portion on the surface of the substrate made of an insulating material,
A paste containing, in the porous film part, first conductor particles having an average particle diameter larger than the average pore diameter of the porous film part and second conductor particles having an average particle diameter smaller than the average pore diameter of the porous film part. Supplying process b ;
The pre-Symbol second conductive particles sintered to provide a method for manufacturing a wiring board, wherein said the step c for forming a wiring pattern on the porous membrane section, the sequential execution.

  A preferred embodiment of the method for manufacturing a wiring board of the present invention includes a step d of supplying a predetermined solvent to the porous film part to reduce the thickness of the porous film part.

  In another preferred embodiment of the method for producing a wiring board according to the present invention, the porous film portion contains a polyetherimide resin or an amideimide resin as a main component, and the predetermined solvent is N-methyl-2-pyrrolidone. is there.

  In another preferred embodiment of the method for producing a wiring board of the present invention, a paste containing the first conductor particles and the second conductor particles is supplied to the porous film portion by an ink jet method.

  In another preferred embodiment of the method for manufacturing a wiring board of the present invention, the wiring pattern is formed by spraying the paste on the scheduled spraying points on the porous film portion in the order of arrangement by an inkjet method.

  According to the present invention, the porous film portion is formed on the surface of the base material made of the insulating material, and the first conductor particles having an average particle diameter larger than the average pore diameter of the porous film portion on the porous film portion; Then, a wiring pattern including, as a material, second conductor particles whose average particle diameter is smaller than the average pore diameter of the porous film portion is formed. Since the wiring pattern is formed on the porous film portion, bleeding of the material is suppressed, and thinning becomes easy.

  Also, the first conductor particles having an average particle size larger than the average pore size of the porous membrane part remain above the surface of the porous membrane part to form a wiring pattern, while the average particle size is the average pore size of the porous membrane part. The smaller second conductor particles enter the gaps between the first conductor particles and the inside of the porous film portion to form a wiring pattern. Therefore, the wiring pattern can be formed so as to have a good conductive portion above the surface of the porous membrane portion and a locking portion for fastening the good conductive portion to the porous membrane portion. Therefore, it is possible to provide a wiring board having a wiring pattern that is thinned, suppresses an increase in electrical resistance, and has excellent coupling strength.

It is sectional drawing which shows schematic structure of the wiring board which concerns on Embodiment 1 of this invention. It is sectional drawing which shows schematic structure of the precursor of a wiring board same as the above. It is sectional drawing which shows the procedure at the time of forming a wiring pattern in a wiring board same as the above, (a) is the state immediately after supplying a paste to a porous film part, (b) is a part of paste inside a porous film part. Shows the state of penetration. It is a schematic diagram which shows the structure of a paste same as the above. It is sectional drawing which shows the structure of a wiring pattern typically. It is a schematic diagram of the paste supply part for demonstrating the procedure which supplies a paste to the porous film part of a wiring board same as the above by an inkjet system. It is sectional drawing which shows schematic structure of the wiring board which concerns on Embodiment 2 of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Embodiment 1)
FIG. 1 is a sectional view showing a schematic configuration of a wiring board according to Embodiment 1 of the present invention. The wiring board 10 of the example of illustration is equipped with the base material 12 comprised from the insulator material.
A porous film portion 14 is provided on the surface of the base material 12. A wiring pattern 16 is formed on the porous film portion 14. As will be described in detail later, the wiring pattern 16 is formed by supplying a paste containing conductive particles on the porous film portion 14 by an ink jet method.

  The base material 12 can be comprised from a synthetic resin film, for example, a polyimide film. In addition, the base material 12 can also be comprised from synthetic resin films, such as polyamide and a polyethylene terephthalate. Although the thickness of the base material 12 can be 25 micrometers, for example, it is not specifically limited. The substrate 12 is not limited to a flexible material such as the above-described synthetic resin film, but may be composed of a rigid insulator material such as a thermosetting resin or ceramic.

  The porous membrane part 14 can be comprised from a porous membrane soluble in a specific solvent. As an example of such a porous film, a porous film composed of an amideimide resin that is a thermosetting resin or a polyetherimide resin that is a thermoplastic resin can be given. A porous film made of these resins is soluble in N-methyl-2-pyrrolidone, for example. Further, the porous membrane portion 14 includes a large number of minute holes having communication properties.

  In FIG. 2, the precursor of the wiring board 10 which consists only of the base material 12 and the porous membrane part 14 is shown. This precursor is configured by attaching a soluble porous film constituting the porous film portion 14 to the surface of the base material 12 at least in a portion where the wiring pattern 16 is to be formed.

  FIG. 3 shows a procedure for forming the wiring pattern 16 in the porous film portion 14. First, as shown in FIG. 2A, a paste 24 containing conductive particles is sprayed from the ink jet nozzle 22 toward the porous film portion 14.

  Here, as shown in FIG. 4, the paste 24 is a liquid material having fluidity at room temperature, the first conductor particles 18 having a diameter larger than the average pore diameter of the porous film part 14, and the diameter of the porous film part. The second conductor particles 20 smaller than the average pore diameter of 14 and the dispersion medium 26 that is liquid at room temperature are included. Such a paste 24 can be prepared by mixing a dispersion in which the first conductor particles 18 are dispersed in the dispersion medium 26 and a dispersion in which the second conductor particles 20 are dispersed in the dispersion medium. it can. The first conductor particles 18 can be made of copper, for example. The second conductor particles can be composed of, for example, silver. As the dispersion medium 26, tetradecane, toluene, water, ethanol, or the like can be used.

  As shown in FIG. 3B, a part of the paste 24 attached to the surface of the porous film part 14 penetrates into the porous film part 14 and the remaining part remains on the porous film part 14.

FIG. 5 is a cross-sectional view schematically showing a part of FIG. As shown in the figure, the first conductor particles 18 contained in the paste 24 have a diameter larger than the average pore diameter of the porous film part 14, and therefore remain above the surface of the porous film part 14. On the other hand, since the diameter of the second conductor particles 20 is smaller than the average pore diameter of the porous membrane portion 14, the second conductor particles 20 penetrate into the porous membrane portion 14. Further, a part of the second conductor particles 20 remains above the surface of the porous film portion 14 and fills the gaps between the first conductor particles 18. At this time, for example, the average particle diameter of the second conductor particles 20 can be 30 nm or less, the average particle diameter of the first conductor particles 18 can be 3 μm or more, and the average pore diameter of the porous membrane portion 14 can be 1 μm.
In addition, the porous membrane part 14 actually has innumerable pores that allow the second conductor particles 20 to enter, but in view of visibility, FIG. 5 is a schematic diagram. Such holes are not shown.

  As described above, after the paste 24 is attached to the porous film part 14 and infiltrated into the porous film part 14, the porous film part 14 including the paste 24 is heated at a predetermined temperature (for example, 220 ° C.). Thereby, the dispersion medium of the paste 24 is volatilized, and at least the second conductor particles 20 that are nanoparticles are sintered. As a result, the first conductor particles 18 are fixed on the surface of the porous film part 14, and the wiring pattern 16 is formed on the porous film part 14.

  Here, the thickness of the porous membrane part 14 is preferably 10 μm or more. This is because if the thickness of the porous film part 14 is less than 10 μm, the porous film part 14 cannot absorb the paste 24 supplied to the surface of the porous film part 14 and the bleeding cannot be suppressed. .

  The average pore diameter of the porous membrane part 14 is preferably 0.01 to 5 μm. This is because if the average pore diameter is less than 0.01 μm, the paste 24 will not easily penetrate into the porous membrane portion 14. On the other hand, when the average pore diameter exceeds 5 μm, the particle diameter of the first conductor particles 18 needs to be larger than 5 μm. A paste containing particles of such a size is difficult to eject by an ink jet method.

In order to suppress the spread of the paste 24 in the width direction of the wiring pattern 16, it is preferable to reduce the connectivity of the pores of the porous film portion 14 in that direction.
Thus, by adjusting the material and thickness of the porous film portion 14 and the direction of connection of the holes, the penetration behavior of the paste 24 can be controlled, and the width and thickness of the wiring pattern 16 are controlled. It becomes possible.

  The volume ratio between the first conductor particles 18 and the second conductor particles 20 included in the paste 24 is the thickness of the portion of the wiring pattern 16 formed using the first conductor particles 18 as a material. The thickness of the portion formed using the second conductor particles 20 as a material is preferably adjusted to be substantially equal. Thereby, the electrical conductivity of the wiring pattern 16 and the bonding strength to the base material 12 can be ensured with a good balance. Therefore, the volume ratio between the first conductor particles 18 and the second conductor particles 20 is preferably a value close to 1, and is preferably adjusted within a range of 0.7 to 1.3, for example.

  The porous membrane as the material of the porous membrane portion 14 is a belt made of stainless steel having a smooth surface obtained by dissolving a solution obtained by dissolving a polyetherimide resin or an amideimide resin in N-methyl-2-pyrrolidone (NMP). It can be produced by pouring onto a substrate for film production such as the above, causing it to adhere, solidifying, and then peeling off from the substrate. At this time, in order to obtain a uniform sponge-like porous structure, a water-soluble polymer (for example, polyvinylpyrrolidone) is added. And by supplying water to the film peeled from the substrate, the water-soluble polymer is extracted to form pores. At this time, the average pore diameter and porosity of the porous membrane part can be adjusted to desired values by changing the type and amount of the water-soluble polymer.

  In general, when the paste 24 is supplied to the porous film portion 14 by the ink jet method, as shown in FIG. 6, the paste 24 is sprayed on the continuous points P <b> 1 to P <b> 10 to form the wiring pattern 16. However, if the paste 24 is sprayed on the points P <b> 1 to P <b> 10 in the order of arrangement, the paste 24 bleeds in the width direction of the wiring pattern 16. Therefore, normally, the paste 24 is sprayed on every other point (for example, points P1, P4, P7 and P10), and then each point shifted one by one (for example, points P2, P5 and P8). ) Is then sprayed, and then the paste is sprayed to each point (for example, points P3, P6 and P9) whose positions are shifted one by one, thereby forming the wiring pattern 16. In other words, the inkjet head is normally reciprocated so that the paste 24 is sprayed several times.

  On the other hand, in the formation of the wiring board 10 of the present embodiment, the wiring pattern 16 is formed by spraying the paste 24 onto the porous film portion 14. For this reason, the spread of the paste 24 in the width direction of the wiring pattern 16 can be remarkably suppressed. As a result, the wiring pattern 16 having a smaller line width can be formed even if the paste 24 is sprayed and formed on the points P1 to P10 in the order in which they are arranged without using the normal method described above. it can. Therefore, by adopting a method in which the paste 24 is sprayed on the points P1 to P10 in the order of arrangement, the reciprocating operation of the inkjet head can be omitted, and the wiring pattern 16 having a smaller line width can be efficiently used. Can be well formed. As a result, productivity can be improved.

  As described above, in the wiring board 10 according to the first embodiment, the porous film portion 14 is formed on the surface of the substrate 12. On the porous membrane part 14, the first conductor particles 18 having a diameter larger than the average pore diameter of the porous membrane part 14 and the second conductor that is a nanoparticle having a diameter smaller than the average pore diameter of the porous membrane part 14. A paste 24 containing the particles 20 is supplied by an inkjet method. The paste 24 penetrates into the porous film part 14. At this time, the first conductor particles 18 having a diameter larger than the average pore diameter of the porous membrane portion 14 remain above the surface of the porous membrane portion 14, and the first conductor particles 18 are mainly wiring having a small electrical resistance. It functions as the pattern 16.

  On the other hand, the second conductor particles 20 that are nanoparticles, the diameter of which is smaller than the average pore diameter of the porous membrane portion 14, partially penetrate into the porous membrane portion 14, and the remaining part of each second conductive particle 20. It remains above the surface of the pore film portion 14 so as to fill the gaps between the body particles 18. By being sintered in that state, the second conductor particles 20 function as a binder having a small electric resistance. As a result, it is possible to form the wiring pattern 16 having high bonding strength to the base material 12 and good conductivity. Moreover, since the porous film portion 14 suppresses the spread of the paste 24 in the wiring width direction, the wiring pattern 16 having a small electric resistance and a small line width can be obtained. Therefore, the wiring pattern 16 can be easily thinned.

  In addition, the porous film which is a raw material of the porous film part 14 is not limited to the polyetherimide resin and the amideimide resin, and various porous films can be used. Such a porous film preferably has a pore structure in which the paste 24 can easily permeate in the thickness direction rather than in the width direction (plane direction). Thereby, the spread of the paste 24 in the width direction of the wiring pattern 16 can be suppressed, and thinning is facilitated. Further, the bonding strength of the wiring pattern 16 to the substrate 12 can be increased.

  Moreover, it is preferable that the material of such a porous film has both a hydrophilic property and an organic solvent property of a predetermined degree or more. More specifically, if the hydrophilicity is too high, the organophilic solvent property is lowered. On the other hand, if the hydrophilic property is too high, the hydrophilicity becomes low. Therefore, by selecting a material having both a hydrophilic property and an oleophilic solvent property of a predetermined degree or more, it is possible to suppress the wetting and spreading of the paste 24 when water or an organic solvent is used as the dispersion medium of the paste 24. Is possible. More specifically, the contact angle of water and an organic solvent (for example, tetradecane) of the material constituting the porous film (when 1 μL of water or an organic solvent (for example, tetradecane) is dropped on the surface of the material that does not form pores) Are preferably 30 ° or more.

  The first conductor particles 18 and the second conductor particles 20 include gold, silver, copper, platinum, palladium, tungsten, nickel, tantalum, bismuth, lead, indium, tin, zinc, titanium, aluminum, and iron. Etc., and at least one selected from their alloys can be used. Moreover, the organic compound which has electroconductivity can also be used as the 1st conductor particle 18 and the 2nd conductor particle 20. FIG.

Next, an example of the first embodiment will be described. The present invention is not limited to the following examples.
Example 1
A porous film (made by Daicel Chemical Industries, Ltd.) made of a polyetherimide resin is pasted on the surface of a base material 12 (Kapton made by Toray DuPont Co., Ltd.) made of polyimide having a thickness of 25 μm. A film part 14 was formed. The film thickness was 25 μm, the average pore diameter was 2 μm, and the porosity was 75%.

  Next, a dispersion liquid in which silver particles having a particle diameter of 3 to 7 nm (average particle diameter of 5 nm) are dispersed in a dispersion medium composed of tetradecane and copper particles having a particle diameter of 3 to 7 μm (average particle diameter of 5 μm) are obtained from tetradecane. A paste 24 was prepared by mixing with a dispersion liquid dispersed in a dispersion medium. At this time, the total content of silver particles and copper particles in the paste 24 was 59.5% by weight. The weight ratio of silver particles to copper particles was 1: 1. The paste 24 was supplied to the porous film part 14 by an ink jet printing apparatus, and then sintered at a temperature of 220 ° C. to form the wiring pattern 16.

  By the above process, the wiring pattern 16 having a thickness of 15 μm and a line width of 90 μm and a high bonding strength to the substrate 12 was formed in the porous film portion 14.

(Example 2)
As the material for the porous membrane part 14, the same as in Example 1 except that an amide-imide resin porous membrane having an average pore diameter of 0.5 μm, a porosity of 80%, and a film thickness of 25 μm was used. Thus, the wiring board 10 was produced.

  As a result, a wiring pattern 16 having the same thickness and line width as in Example 1 and high bonding strength to the base material 12 was formed.

(Embodiment 2)
Next, a second embodiment of the present invention will be described. FIG. 7 is a cross-sectional view showing a schematic configuration of the wiring board according to the second embodiment.
The second embodiment is a modification of the first embodiment, and its basic configuration is the same as that of the first embodiment. Therefore, the following description will mainly focus on the differences from the first embodiment.

  As shown in FIG. 7, in the wiring board 10A of the second embodiment, the porous film part 14A is treated with a predetermined solvent (organic solvent) to reduce the thickness.

  Here, NMP (N-methyl-2-pyrrolidone) can be used for the treatment of the porous membrane portion 14A. When a porous film portion 14A made of a polyetherimide resin or an amideimide resin is impregnated with a predetermined solvent such as NMP, at least a part of the structure of the film dissolves, the pores are crushed, and the thickness and width are reduced. Get smaller. As a result, the wiring pattern 16A protrudes higher from the porous film portion 14A.

Thus, by making the wiring pattern 16A protrude higher from the porous film portion 14A, the contact resistance between the wiring pattern 16A and other members can be reduced. In addition, since the cross-sectional area of the portion located above the porous film portion 14A of the wiring pattern 16A and contributing to conduction is increased, the conduction resistance is also reduced.
Therefore, better electrical conductivity of the wiring pattern 16A can be achieved.

  According to the wiring board and the manufacturing method of the wiring board of the present invention, a wiring pattern having a smaller line width is formed by suppressing the spread in the width direction of the paste containing conductive particles supplied by the ink jet method. be able to. In addition, a wiring pattern with better conductivity can be obtained. Furthermore, a wiring pattern having a high bonding strength to the substrate can be obtained. Therefore, it is useful as a wiring board used for a semiconductor element having a higher integration density.

DESCRIPTION OF SYMBOLS 10 Wiring board 12 Base material 14 Porous film part 16 Wiring pattern 18 1st conductor particle 20 2nd conductor particle 22 Inkjet head 24 Paste

Claims (8)

A base material made of an insulator material;
A porous membrane formed on the surface of the substrate;
A wiring pattern formed on the porous membrane part,
The wiring pattern includes a plurality of first conductor particles having an average particle diameter larger than the average pore diameter of the porous film portion, and a plurality of second conductor particles having an average particle diameter smaller than the average pore diameter of the porous film portion. Consists of
The plurality of first conductor particles are arranged in one layer on the surface of the porous membrane part,
The plurality of second conductor particles are disposed on the surface of the porous membrane portion so as to surround a lower surface and a side surface of each of the first conductor particles so that the plurality of first conductor particles do not contact each other. and inside are arranged, the plurality of first conductive particles are bonded to the porous membrane portion, a wiring board, characterized in that.   The wiring board according to claim 1, wherein the average particle diameter of the second conductor particles is 30 nm or less.   The wiring board according to claim 1, wherein a volume ratio of the first conductor particles to the second conductor particles is 0.7 to 1.3.   The wiring board according to claim 1, wherein an average pore diameter of the porous film part is 0.01 μm or more and 5 μm or less.   The first conductor particles and the second conductor particles are gold, silver, copper, platinum, palladium, tungsten, nickel, tantalum, bismuth, lead, indium, tin, zinc, titanium, aluminum, and iron, and their The wiring board according to claim 1, comprising at least one selected from alloys.   The wiring board according to any one of claims 1, 3, and 5, wherein a material of the first conductor particles is different from a material of the second conductor particles. 7. The wiring board according to claim 1, wherein the connectivity of the holes included in the porous film portion in the width direction of the wiring pattern is smaller than the connectivity in the other directions. Forming a porous film portion on the surface of a base material made of an insulator material; and
In the porous membrane portion, a plurality of first conductor particles having an average particle size larger than the average pore size of the porous membrane portion, and a plurality of second conductor particles having an average particle size smaller than the average pore size of the porous membrane portion, A step of supplying a paste containing , wherein the plurality of first conductor particles are arranged in a single layer on the surface of the porous membrane portion, and the plurality of second conductor particles are the plurality of first conductor particles. Arranged on and in the surface of the porous membrane part so as to surround the lower surface and the side surface of each of the first conductive particles so that the conductive particles do not contact each other ;
The step c of sintering the second conductor particles , bonding the plurality of first conductor particles to the porous film portion, and forming a wiring pattern on the porous film portion is sequentially performed. A method for manufacturing a wiring board.

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