JP4212887B2 - Multilayer circuit board manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a multilayer circuit board formed with an ink-jet circuit pattern.ofIt relates to a manufacturing method.
[0002]
[Prior art]
A multilayer circuit board formed by laminating a plurality of resin films on which a circuit pattern is formed and a method for manufacturing the same are disclosed in, for example, Japanese Unexamined Patent Publication No. 2000-38464 (Patent Document 1).
[0003]
According to the method for manufacturing a multilayer circuit board disclosed in Patent Document 1, after laminating a plurality of resin films made of a thermoplastic resin on which a circuit pattern made of copper foil is formed, a predetermined temperature is obtained. And pressurizing while heating at pressure. As a result, the adjacent resin films are fused and integrated, and the conductive paste filled in the holes in the resin film is sintered to electrically connect the circuit patterns of the respective layers.
[0004]
On the other hand, an electronic device using ink jet and a method for manufacturing the same are disclosed in Japanese Patent Laid-Open No. 11-274681 (Patent Document 2).
[0005]
According to the electronic device disclosed in Patent Document 2 and the method for manufacturing the same, an ink in which an adsorption layer made of a porous body of an inorganic oxide is formed on a substrate and materials for forming electrodes and insulating films are dispersed in a solvent. Is discharged onto the adsorption layer. Thereby, the solvent of the ink diffuses into the adsorption layer, and an element pattern is uniformly formed at a target position on the substrate.
[0006]
[Patent Document 1]
JP 2000-38464 A
[0007]
[Patent Document 2]
JP-A-11-274681
[0008]
[Problems to be solved by the invention]
According to the method for manufacturing a multilayer circuit board disclosed in Patent Document 1, a plurality of laminated resin films are bonded together by heating and pressing, and at the same time, a conductive paste is sintered to form a wiring circuit. Therefore, the multi-layering process can be short. On the other hand, in the multilayer circuit board of Patent Document 1, a very large number of processes are required in which a thick copper foil is attached to a film, and then a resist is applied to the entire surface, exposed, and etched.
[0009]
In order to solve this problem, the inventors have not formed a circuit pattern from a thick copper foil, but a method of manufacturing a multilayer circuit board using the formation of a circuit pattern by inkjet, and the multilayer circuit board manufactured thereby Was invented. According to this, the circuit pattern forming process in the manufacturing process of the multilayer circuit board is simplified, and the miniaturization of the circuit pattern can be promoted. A patent application has already been filed for this invention (application number 2002-31650).
[0010]
Circuit pattern formation by inkjet is a method of forming a circuit pattern by ejecting ink in the form of droplets and landing on the substrate surface. In order to improve the accuracy of the circuit pattern of the multilayer circuit board by using this ink jet and further promote the miniaturization, the spread due to the impact when the ink droplets land and the spread due to the bleeding due to the surface state of the substrate Need to prevent. Further, the dimensional accuracy of the circuit pattern also deteriorates when adjacent ink droplets are combined to form a large droplet.
[0011]
On the other hand, according to the electronic device and the manufacturing method thereof disclosed in Patent Document 2, the ink layer is diffused into the adsorption layer by the adsorption layer formed on the substrate, and the electrons are uniformly distributed at the target position of the substrate. A device is formed. However, since the invention of Patent Document 2 is not intended for a multilayer circuit board, generally, if a substrate on which an adsorption layer is formed is multilayered as it is, peeling may occur in the adsorption layer. Concerned.
[0012]
  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a multilayer circuit board in which ink droplets are prevented from spreading and bonding when forming a circuit pattern by inkjet, a fine and highly accurate circuit pattern is formed, and the occurrence of peeling is suppressed.ofIt is to provide a manufacturing method.
[0013]
[Means for Solving the Problems]
  The invention according to claim 1 is a multilayer circuit board formed by laminating a plurality of resin films made of a thermoplastic resin on which an ink-jet circuit pattern is formed.In the manufacturing method, an absorption layer forming step of partially forming an absorption layer that absorbs an ink solvent on a resin film, including a position where a circuit pattern is formed, and a resin in which the absorption layer is formed Through the film, a through-hole forming step for forming a through-hole, a conductive paste filling step for filling the through-hole with a conductive paste, and an ink containing a pigment made of a circuit material having a particle size of the order of nanometers by an inkjet device An ink pattern forming step of forming a circuit pattern with the ink on the surface of the absorption layer including the position where the through hole is formed, and discharging the ink onto the absorption layer; and filling the through hole with the conductive paste; A laminating step of laminating a plurality of resin films formed on the absorbent layer, and heating and pressurizing the laminated resin films with a hot press plate Bonded together to the resin film to each other, heating and pressurizing step of sintering the conductive paste and the ink patternIt is characterized by having.
[0014]
  Using this method for manufacturing a multilayer circuit board, a multilayer circuit board in which a fine and highly accurate circuit pattern shown below is formed and the occurrence of peeling can be suppressed can be manufactured. Further, in this method of manufacturing a multilayer circuit board, resin films are bonded together by heating and pressing, and at the same time, the conductive paste and the ink pattern are sintered to form a wiring circuit. The manufacturing cost of the multilayer circuit board can be reduced.
That is, the multilayer circuit board manufactured by the manufacturing method of the multilayer circuit board isSince the absorption layer laminated on the resin film absorbs the ink solvent quickly, it is possible to prevent the ink droplet from spreading due to the surface state of the resin film. In addition, after the ink droplets have landed, the ink solvent is immediately absorbed by the absorption layer, so that even if the ink droplets land adjacently, the ink droplets are combined to deteriorate the dimensional accuracy of the circuit pattern. There is nothing. In this wayManufactured by the above-mentioned multilayer circuit board manufacturing methodThe multilayer circuit board can be a multilayer circuit board on which a fine and highly accurate circuit pattern is formed by preventing ink droplets from spreading and bonding when forming a circuit pattern by inkjet.
[0015]
  Also,In the manufacturing method of the multilayer circuit board,Since the absorption layer is partially formed on the resin film, there is a region where the absorption layer is not formed on the surface of the resin film.Therefore, according to the manufacturing method of the multilayer circuit boardIn a multilayer circuit board in which such resin films are laminated, there is a region where resin films made of a thermoplastic resin are directly bonded to each other without interposing an absorption layer therebetween. by this,The multilayer circuit board manufactured by the manufacturing method of the multilayer circuit board,The bonding strength between the resin films is increased, and a multilayer circuit board in which the occurrence of peeling is suppressed can be obtained.
[0016]
  The invention described in claim 2In the method for manufacturing the multilayer circuit board,The pigment is a metal particle having a particle size of 50 nm or less.
[0017]
  Metal particles having a particle size of 50 nm or less can be sintered at a low temperature. For this reason,In the manufacturing method,Sintering of the pattern which consists of the metal particle formed by the inkjet can be performed simultaneously with bonding of resin films and sintering of a conductive paste. Therefore, the manufacturing process is simplified and an inexpensive multilayer circuit board can be obtained.
[0018]
  The invention according to claim 3In the method for manufacturing the multilayer circuit board,The pigmentBut,The particle size is 5 nm or more, the absorption layer is a fine particle layer in which fine particles made of either aluminum oxide or silicon oxide are dispersed, and the voids of the fine particle layer are 5 nm or less.
[0019]
  Aluminum oxide or silicon oxide can be made into fine particles having a particle size on the order of nanometers, and the voids can be made 5 nm or less in the fine particle layer in which the fine particles of nanometer order are dispersed. By using such a fine particle layer as an absorption layer and setting the particle size of the ink pigment to 5 nm or more, the pigment contained in the ink droplets that have landed on the absorption layer can penetrate into the absorption layer together with the solvent. Disappears. In other words, only the ink solvent is absorbed by the absorption layer, and the pigment remains on the surface of the absorption layer. ThisIn the manufacturing method,It is possible to prevent the pigment from penetrating into the absorption layer to cause a circuit pattern defect or a short circuit failure.
The invention according to claim 4 is characterized in that the absorption layer is formed by discharging an ink containing a pigment composed of the fine particles onto a resin film by an ink jet apparatus.
Thereby, an absorption layer can be partially formed on a resin film using the same inkjet apparatus as the formation of an ink pattern. Therefore, the manufacturing cost can be reduced by using the same apparatus.
[0020]
  Claim5The invention described inIn the method for manufacturing the multilayer circuit board,The absorption layer is a swelling layer made of either urethane resin or acrylic resin having swelling property.
[0021]
  Urethane resins or acrylic resins have resistance and swelling to general ink solvents and also have heat resistance to heat treatment. If an absorbing layer is formed using this urethane resin or acrylic resin, the swelling layer absorbs only the solvent contained in the ink droplets that have landed on the absorbing layer due to the swelling property of the ink with respect to the solvent, and the ink pigment is the absorbing layer. It can be left on the surface. ThisIn the manufacturing method,It is possible to prevent the pigment from penetrating into the absorption layer to cause a circuit pattern defect or a short circuit failure.
The invention according to claim 6 is characterized in that the absorption layer is formed by ejecting an ink containing a dye made of a resin of the swelling layer onto a resin film by an ink jet apparatus.
Thereby, an absorption layer can be partially formed on a resin film using the same inkjet apparatus as formation of a circuit pattern. Therefore, the manufacturing cost can be reduced by using the same apparatus.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a multilayer circuit board and a manufacturing method thereof according to the present invention will be described with reference to the drawings.
[0032]
FIG. 1 is a cross-sectional view of a multilayer circuit board 100 of the present invention.
[0033]
In the multilayer circuit board 100 of FIG. 1, reference numeral 1 denotes an insulating base material in which four resin films made of a liquid crystal polymer (LCP) which is a thermoplastic resin are bonded to each other. The material of the resin film may be a thermoplastic resin such as polyether ether ketone, polyether ether ketone / polyether imide mixture, polyphenylene sulfide, etc. in addition to LCP. In addition, the thickness of one sheet of the resin film bonded together is 1-1000 micrometers.
[0034]
In the multilayer circuit board 100 of FIG. 1, reference numeral 2 is a circuit pattern formed by inkjet and sintered with an ink pigment made of a circuit material having a particle size on the order of nanometers. A circuit pattern 2 shown in FIG. 1 is a wiring pattern in which metal particles having a particle size of nanometer order are sintered. As the nanometer-order metal particles, for example, silver (Ag) is used. In the method of manufacturing the multilayer circuit board 100 described later, the particle size is preferably 50 nm or less in order to reduce sintering by heating and pressing as much as possible.
[0035]
In the multilayer circuit board 100 of FIG. 1, reference numeral 3 denotes an absorption layer that is laminated on each resin film before bonding, and each resin film absorbs an ink solvent when forming a circuit pattern by inkjet. Is a layer. As the absorption layer 3, a fine particle layer in which fine particles made of aluminum oxide or silicon oxide, which are inorganic materials, are dispersed can be used. In the absorption layer 3 composed of the fine particle layer, in order to prevent the ink pigment from entering the inside of the absorption layer, for example, when the particle size of the ink pigment is 5 nm or more, the voids in the fine particle layer The minimum particle size needs to be 5 nm or less. Aluminum oxide and silicon oxide can be made into fine particles having a particle size on the order of nanometers. By using fine particles having a particle size of 10 to 20 nm, the voids of the fine particle layer can be reduced to 5 nm or less.
[0036]
As the absorption layer 3, a swelling layer made of either urethane resin or acrylic resin having swelling properties can be used. In the absorption layer 3 made of these polymer materials, the solvent of the ink is absorbed by utilizing the swellability instead of absorbing the solvent by using the voids unlike the fine particle layer. The polymer material having swelling property is generally inferior in resistance to solvents and heat resistance as compared with the fine particle layer made of the inorganic material. Among these general swellable polymer materials, urethane resins and acrylic resins are materials excellent in resistance to solvents used in inks and heat resistance.
[0037]
In the multilayer circuit board 100 of FIG. 1, the absorption layer 3 is formed only around the circuit pattern 2. As described above, a fine particle layer using fine particles of an inorganic material or a swollen layer of a polymer material is used for the absorption layer 3. Generally, these layers are a resin film 1 of an insulating base material made of a thermoplastic resin. Less strength. Therefore, when the absorbent layer 3 is formed on the entire surface of the resin film 1, peeling easily occurs. In particular, when a fine particle layer is used for the absorbent layer 3, the occurrence of peeling becomes remarkable.
[0038]
Therefore, by forming the absorption layer 3 only around the circuit pattern 2 as in the multilayer circuit board 100 shown in FIG. 1, there is a region where the absorption layer is not formed on the surface of each laminated resin film 1. To do. Therefore, in the multilayer circuit board 100 in which such resin films 1 are laminated, there is a region where the resin films 1 made of thermoplastic resin are directly bonded to each other without the absorption layer 3 interposed therebetween. Thereby, the bonding strength between the resin films 1 is increased, and the occurrence of peeling is suppressed.
[0039]
The thickness of the absorption layer 3 is 1 to 100 μm, and an optimum thickness is set according to the amount of solvent of the ink and the absorption performance of the absorption layer 3.
[0040]
In the multilayer circuit board 100 of FIG. 1, reference numeral 7 denotes a connection conductor that connects the circuit patterns 2 to each other, and is obtained by sintering a conductive paste filled in a through hole that penetrates a resin film and an absorption layer. The conductive paste before sintering is a paste obtained by adding a binder resin or an organic solvent to silver (Ag) and tin (Sn) metal particles and kneading them. The conductive paste may be a paste containing metal particles of gold (Au) and tin (Sn), or copper (Cu) and tin (Sn). Since Sn is mixed in these conductive pastes, these conductive pastes can be sintered at a relatively low temperature.
[0041]
Next, a method for manufacturing the multilayer circuit board 100 of FIG. 1 will be described.
[0042]
2 (a) to 2 (e) are cross-sectional views showing process steps for preparing a resin film in the method for manufacturing a multilayer circuit board according to the present invention.
[0043]
First, as shown in FIG. 2A, a resin film 1 made of a thermoplastic resin such as a liquid crystal polymer (LCP) having a protective film 1c attached on one side is prepared.
[0044]
Next, the absorption layer 3 is partially formed on the surface of the resin film 1 opposite to the protective film 1c. The absorbing layer 3 is a layer that exhibits an effect when the ink pattern 2i is formed in the step of FIG. 2E. For this reason, the absorbing layer 3 is partially formed on the resin film 1 including the position where the ink pattern 2i is formed.
[0045]
As described above, the absorbing layer 3 may be made of inorganic fine particles such as aluminum oxide or silicon oxide, or may be made of a polymer material such as urethane resin or acrylic resin. When inorganic material fine particles are used, a slurry containing these fine particles is formed, and when a polymer material is used, a swelling liquid is formed and partially applied onto the resin film 1. After the application, a drying treatment is performed to disperse the solvent of the slurry or the swelling liquid, and the absorption layer 3 having a thickness of about 1 μm is typically formed on the surface of the resin film 1.
[0046]
In order to partially form the absorbent layer 3 on the resin film 1, for example, after forming the absorbent layer 3 on the entire surface of the resin film 1 by a coater, dip, cast coat, etc., the absorbent layer 3 is patterned into a predetermined shape. May be. This patterning may be performed after the ink pattern 2i shown in FIG. Alternatively, the material of the absorption layer 3 may be made into a paste and partially formed on the resin film 1 by screen printing or transfer.
[0047]
Next, as shown in FIG.2 (b), the through-hole 6 is opened by the laser in the resin film 1 which the protective film 1c was affixed on one surface, and the absorption layer 3 was formed in the other surface.
[0048]
Next, as shown in FIG. 2 (c), the protective film 3 c is attached on the absorbent layer 3 to the protective film 1 c, the resin film 1, and the absorbent layer 3 in which the through holes 6 are formed. 6 is covered. Thereafter, using a paste filling device, the conductive paste 7p is pushed and filled into the covered through-hole 6 with a squeegee.
[0049]
Next, as shown in FIG.2 (d), the protective films 1c and 3c stuck on both sides are peeled off. Thereby, the resin film 1 in which the absorption layer 3 is formed on the surface and the through-hole 6 is filled with the conductive paste 7p is obtained.
[0050]
Next, an ink pattern 2i is formed as shown in FIG. The formation of the ink pattern 2i will be described in detail with reference to FIGS. 3 (a) and 3 (b).
[0051]
FIG. 3A is a schematic diagram of the ink used for forming the ink pattern 2i of FIG. The ink 20 in FIG. 3A is obtained by independently dispersing an ink pigment 21 made of a circuit material having a particle size on the order of nanometers in a solvent 24. The surface of the nanometer-order pigment 21 is coated with a dispersant 22 by a wet process, whereby aggregation of the pigment 21 is prevented. Further, in the solvent 24, a scavenger 23 that traps the dispersant 22 during the sintering of the pigment 21 in the subsequent step is mixed.
[0052]
As the nanometer-order pigment 21, for example, silver (Ag) is used, and the particle size is preferably 50 nm or less in order to reduce the temperature of sintering by heating and pressurization as much as possible.
[0053]
Further, as the dispersant 22, a material having a group having a lone electron pair of nitrogen, oxygen or sulfur atom and having a coordinate bond with the pigment 21 can be used. For example, as a group having a lone pair of nitrogen atoms, there is a C8 to C18 alkylamine having an amino group. Groups having a lone pair of sulfur atoms include C8-C18 alkanethiols having a sulfanyl group (—SH—). Examples of the group having a lone pair of oxygen atoms include alkanediols such as ethylene glycol, diethylene glycol, and polyethylene glycol having a hydroxy group.
[0054]
Next, as the scavenger 23, a material capable of reacting with a group containing nitrogen, oxygen, or sulfur atoms of the dispersant 22 when heated to remove the coating layer of the dispersant 22 is used. Specifically, an organic acid anhydride or a derivative thereof, or an organic acid can be used. For example, an acid anhydride or a derivative thereof reacts with an amine compound or a thiol compound that is the dispersant 22 with heating. To form esters and thioesters. As a result, the dispersant 22 covering the pigment 21 is removed from the surface of the pigment 21.
[0055]
FIG. 3B is a schematic diagram illustrating how the ink pattern 2 i is formed by the inkjet device 30. In addition, in the resin film 1 in which the absorption layer 3 of FIG.3 (b) was formed, illustration of the through-hole 6 and the electrically conductive paste 7p shown in FIG.2 (e) is abbreviate | omitted.
[0056]
The ink jet device 30 uses a piezo element 33 that is deformed when a voltage is applied, and deflects the wall 32 of the pressure chamber 31 in which the ink 20 is stored as indicated by the arrows in the figure, thereby ejecting the ink 20 as fine droplets. It is a device to do. The droplet volume of the ejected ink 20 is several pl (picoliter) per droplet, and the viscosity of the ink 20 is adjusted to several mPa · s in order for the ink droplet to fly stably. The ink jet device 30 shown in FIG. 3B ejects ink 20 while driving the pressure chamber 31 side or the resin film 1 side in an XY manner, and ink corresponding to a circuit is formed on the absorption layer 3 of the resin film 1. Pattern 2i is drawn directly.
[0057]
In addition to the method shown in FIG. 3B, the ink jet method for ejecting liquid droplets using a piezo element includes the method shown in FIGS. 4A and 4B.
[0058]
In the method of the ink jet device 30r in FIG. 4A, the pressure chamber wall itself is formed by a piezo element 33r, and the piezo element 33r is deformed in a “sliding” mode as shown in the figure to form droplets (not shown). This is a method of discharging in a direction perpendicular to the paper surface. FIG. 4A shows a state where the inks 20a to 20e are divided into five pressure chambers and the inks 20b and 20d are ejected. The ink jet device 30 s shown in FIG. 4B is a method for ejecting the ink 20 by using a laminated piezo element 33 s as shown in the arrow in the figure.
[0059]
In addition to the above-described method using a piezo element, a bubble jet (registered trademark) method or a thermal jet using a “film boiling phenomenon” generated by forming a heater in a pressure chamber and passing a current through the heater. There are also methods. In order to form the ink pattern 2i shown in FIG. 3B, it is possible to apply an ink jet apparatus of any ejection method that utilizes mechanical deformation or boiling phenomenon, including other ejection methods.
[0060]
In FIG. 3B, when the ejected ink droplet of several picoliters reaches the surface of the absorption layer 3, it becomes a dot of about 30 μm. The absorption layer 3 laminated on the resin film 1 quickly absorbs the ink solvent 24 immediately after the ink droplets have landed. Thereby, spreading due to bleeding of ink droplets due to the surface state of the resin film 1 is prevented. In addition, since the solvent 24 is quickly absorbed after landing, even if ink droplets land adjacently, the ink droplets do not combine with each other and the dimensional accuracy of the ink pattern 2i does not deteriorate.
[0061]
In addition, as described above, the absorption layer 3 may be made of fine particles of an inorganic material such as aluminum oxide or silicon oxide, or may be made of a polymer material such as urethane resin or acrylic resin. Aluminum oxide and silicon oxide can be made into fine particles having a particle size on the order of nanometers, and in the fine particle layer in which the fine particles of nanometer order are dispersed, the voids can be made 5 nm or less. By making such a fine particle layer as the absorption layer 3 and the particle diameter of the ink pigment 21 to be 5 nm or more, the pigment 21 contained in the ink droplets that have landed on the absorption layer 3 together with the solvent 24 has It will not penetrate inside. In other words, only the solvent 24 penetrates into the absorption layer 3, and the pigment 21 remains on the surface of the absorption layer 3. Further, when a urethane resin or an acrylic resin is used as the absorption layer 3, the solvent 24 contained in the landed ink droplets permeates the absorption layer 3 due to the swelling property with respect to the solvent 24, so that the pigment 21 is formed on the absorption layer 3. It remains on the surface as it is. Accordingly, in both cases, the ink pattern 2i is prevented from being lost or short-circuited due to the penetration of the pigment 21 into the absorption layer.
[0062]
In this way, the drawn ink pattern 2i can be a fine and highly accurate ink pattern 2i that is prevented from spreading and combining ink droplets and that is free from defects and short-circuit defects.
[0063]
In FIG. 2A, printing or transfer is taken as an example of a method for partially applying the absorbent layer 3 on the resin film 1, but the absorbent layer 3 is either an inorganic material fine particle layer or a polymer material swelling layer. In this case, the same ink jet method as described above can be used. When the absorbing layer 3 is a fine particle layer, it is ejected and formed on the resin film 1 by an ink jet apparatus 30 similar to that shown in FIG. 3B, using an ink containing aluminum oxide or silicon oxide fine particles as a pigment. Similarly, when the absorbing layer 3 is a swollen layer, the ink jetting apparatus 30 discharges and forms it on the resin film 1 using ink containing urethane resin or acrylic resin as a dye. Thus, the manufacturing cost can be reduced by using the same inkjet device 30 as that for forming the circuit pattern.
[0064]
As described above, the resin film 11 in which the through-hole 6 shown in FIG. 2E is filled with the conductive paste 7p and the ink pattern 2i is formed on the absorption layer 3 is completed. The resin film 11 on which the ink pattern 2 i is formed is dried to volatilize the solvent 24 that has permeated the absorption layer 3. Further, when the resin film 11 is heated at, for example, 150 ° C. for 30 minutes to presinter the ink pattern 2 i and the conductive paste 7 p, handling in the following post-process becomes easy.
[0065]
Next, a multilayer circuit board is manufactured by laminating a plurality of resin films having the conductive paste and ink pattern prepared as described above and bonding them by heating and pressing.
[0066]
5 (a) and 5 (b) are cross-sectional views by process showing the state of bonding of resin films in the method for producing a multilayer circuit board of the present invention.
[0067]
First, as shown in FIG. 5A, the resin films 12 to 15 prepared in the steps of FIGS. 2A to 2E are laminated, and the adhesion preventing film 51, the buffer material 52, and the metal plate 53 are laminated. The heater 55 is inserted between the pair of hot press plates 54 embedded therein. The anti-adhesion film 51 prevents the resin film 1 during heating / pressurization from adhering to surrounding members, and the resin film 1 on which the absorption layer 3 is formed and the ink pattern 2i from being damaged. For example, a polyimide film or the like is used. The buffer material 52 is used to pressurize the resin films 12 to 13 uniformly. For example, a material obtained by cutting a metal such as stainless steel into a fiber and molding the fiber metal into a plate having a thickness of about 1 mm is used. It is done. The metal plate 53 is for preventing the hot press plate 54 from being damaged. For example, a plate made of stainless steel (SUS) or titanium (Ti) with a thickness of about 2 mm is used.
[0068]
Next, as shown in FIG. 5B, the heater 55 is first heated, and the whole is heated at 150 ° C. or lower for 5 minutes without applying pressure. Next, 20 kg / cm is applied to the laminate through a hot press plate 54 by a press machine (not shown).²Apply a pressure of. Next, the whole temperature is set to 200 to 250 ° C., and heated and pressurized for 10 to 30 minutes. Heating and pressurization may be performed in the air, but preferably performed in a vacuum in order to suppress oxidation of metal particles contained in the ink pattern 2i and the conductive paste 7p.
[0069]
The thermoplastic resin 1 of the resin films 12 to 15 adheres to each other by the above heating and pressurization. As shown in FIG. 5A, the absorption layer 3 is partially formed on each resin film 12-15 including the position where the ink pattern 2i is formed. There is a region where the absorption layer 3 is not formed on the surface. Therefore, in such a region, the resin films 1 made of thermoplastic resin are directly bonded to each other without interposing the absorption layer 3 therebetween. Thereby, the bonding strength between the resin films 1 increases, and the occurrence of peeling of the multilayer circuit board 100 shown in FIG. 5B and FIG. 1 is suppressed.
[0070]
Simultaneously with the adhesion of the resin films 12 to 15 by heating and pressing, the nanometer-order pigment contained in the ink pattern 2i and the metal particles contained in the conductive paste 7p are sintered. The sintering process of the metal particles contained in the ink pattern 2i will be described in detail with reference to FIGS. 6 (a) and 6 (b).
[0071]
FIG. 6A is a schematic diagram of ink pigments included in the ink pattern 2i before the start of sintering. In this sintering process, as shown in FIG. 6 (a), the dispersant 22 is captured by the scavenger 23 by heating, and the dispersant 22 is removed from the surface of the pigment 21, so that the active surface of the pigment 21 is exposed. To do.
[0072]
FIG. 6B is a schematic diagram of ink pigments included in the ink pattern 2i after the start of sintering. When the dispersing agent 22 is removed and the active surface of the nanometer-order pigment 21 is exposed, the surfaces of the pigments 21 come into contact with each other as shown in FIG. As a result, a film 21f formed by sintering an ink pigment made of a circuit material is formed. For example, when Ag particles having a particle size of 50 nm or less are used as the pigment 21, the Ag particles are sintered at about 200 ° C., and an Ag film 21 f is formed, resulting in the circuit pattern 2 shown in FIG.
[0073]
Thus, metal particles having a particle size of 50 nm or less can be sintered at a low temperature. For this reason, sintering of the ink pattern 2i made of metal particles formed by inkjet can be performed simultaneously with the bonding of the resin films 1 and the sintering of the conductive paste 7p. Accordingly, this simplifies the manufacturing process and reduces the manufacturing cost.
[0074]
As described above, as shown in FIG. 5B, the thermoplastic resins 1 of the resin films 12 to 15 in FIG. 5A are bonded and integrated to form the insulating material 1, and FIG. Each of the ink patterns 2i is sintered to form the circuit pattern 2, and the conductive paste 7p is sintered to form the connection conductor 7.
[0075]
In this manner, the multilayer circuit board 100 in which the fine and highly accurate circuit pattern 2 shown in FIG. 1 is formed and the occurrence of peeling is suppressed is manufactured. In the manufacturing method of the multilayer circuit board 100 described above, the resin films 12 to 15 are bonded together by heating and pressing, and at the same time, the conductive paste 7p and the ink pattern 2i are sintered to form a wiring circuit. Since the manufacturing process is simplified by such simultaneous formation, the manufacturing cost of the multilayer circuit board 100 can be reduced.
[0076]
(Other embodiments)
FIG. 3A shows an example in which silver (Ag) is used as the nanometer-order pigment 21. According to this, in the multilayer circuit board 100 shown in FIG. 1, the circuit pattern 2 made of Ag is formed. The nanometer-order pigment 21 contained in the ink 20 is not limited to Ag, and for example, metal particles of gold (Au), platinum (Pt), and tin (Sn) can be used.
[0077]
Further, the pigment 21 contained in the ink 20 is not limited to metal particles having a single composition. If the composition of the pigment 21 contained in the ink 20 is changed to use, for example, a mixed composition of Ag particles of 50 nm or less and palladium (Pd) particles of 50 nm or less, the Ag and S Pd can be alloyed to form a resistance film. Therefore, for example, if an ink pattern is formed with ink containing Ag particles and Pd particles by connecting to an ink pattern formed with ink containing only Ag particles, the resistance element pattern is included using the same manufacturing method as described above. A multilayer circuit board having a circuit pattern can be manufactured. In addition, the circuit pattern formed on the multilayer circuit board may be a capacitive element using pigments of dielectric material particles of the nanometer order.
[0078]
As described above, various circuit patterns such as a wiring pattern, a resistance element, and a capacitance element can be formed by inkjet using fine particles having a particle size of nanometer order made of a metal or dielectric circuit material as a pigment.
[0079]
5 (a) and 5 (b), the resin films 12 to 15 having the ink pattern 2i formed on the absorption layer 3 are laminated to prepare a multilayer circuit. The example which forms the board | substrate 100 was shown. The resin film to be laminated may not be a resin film in which the ink pattern 2 i is formed on the absorption layer 3, all by the steps of FIGS. For example, a resin film in which an ink pattern 2i is formed on the absorption layer 3 prepared in the steps of FIGS. 2 (a) to 2 (e) is laminated on a resin film in which a circuit pattern is formed using a conventional copper foil. A multilayer circuit board may be formed.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a multilayer circuit board according to the present invention.
FIGS. 2A to 2E are cross-sectional views showing process steps for preparing a resin film in the method for producing a multilayer circuit board according to the present invention. FIGS.
FIG. 3A is a schematic diagram of ink used for forming an ink pattern, and FIG. 3B is a schematic diagram illustrating how an ink pattern is formed by an inkjet apparatus.
FIGS. 4A and 4B are diagrams illustrating an ink jet apparatus of another ejection method using a piezo element. FIGS.
FIGS. 5A and 5B are cross-sectional views showing a state of bonding of resin films in the method for manufacturing a multilayer circuit board according to the present invention.
6A is a schematic diagram of ink pigments included in an ink pattern before the start of sintering, and FIG. 6B is a schematic diagram of ink pigments included in the ink pattern after the start of sintering. is there.
[Explanation of symbols]
100 multilayer circuit board
1 Insulation base material (resin film)
2 Circuit pattern
2i ink pattern
3 Absorption layer
6 Through hole
7 Connecting conductor
7p conductive paste
11-15 Resin film having an ink pattern formed on the absorbent layer
20, 20a-20e ink
21 Ink pigment of nanometer order
22 Dispersant
23 Scavenger
24 Solvent
30, 30r, 30s inkjet device

Claims (6)

In a method for manufacturing a multilayer circuit board in which a plurality of resin films made of a thermoplastic resin having a circuit pattern formed by inkjet are laminated ,
An absorption layer forming step of partially forming an absorption layer that absorbs the solvent of the ink on the resin film, including the position where the circuit pattern is formed;
A through hole forming step of forming a through hole in the resin film on which the absorption layer is formed;
A conductive paste filling step of filling the through hole with a conductive paste;
An ink containing a pigment made of a circuit material having a particle size of the order of nanometers is ejected onto the absorption layer by an inkjet device, and a circuit pattern is formed on the surface of the absorption layer including the formation position of the through hole An ink pattern forming step;
A laminating step of laminating a plurality of resin films in which the conductive paste is filled in through holes and the ink pattern is formed on an absorption layer;
The multilayer resin film has a heating and pressing step of heating and pressing the laminated resin film with a hot press plate to bond the resin films to each other and sintering the conductive paste and the ink pattern. A method of manufacturing a circuit board. The method for producing a multilayer circuit board according to claim 1, wherein the pigment is a metal particle having a particle size of 50 nm or less. The pigment has a particle size of 5 nm or more, the absorption layer is a fine particle layer in which fine particles made of either aluminum oxide or silicon oxide are dispersed, and the voids of the fine particle layer are 5 nm or less. A method for manufacturing a multilayer circuit board according to claim 1 or 2. 4. The method for manufacturing a multilayer circuit board according to claim 3 , wherein the absorption layer is formed by ejecting an ink containing a pigment composed of the fine particles onto a resin film by an inkjet apparatus . The method for producing a multilayer circuit board according to claim 1 , wherein the absorption layer is a swelling layer made of either urethane resin or acrylic resin having swelling properties . 6. The method for manufacturing a multilayer circuit board according to claim 5, wherein the absorbing layer is formed by ejecting an ink containing a dye made of the resin of the swelling layer onto a resin film by an inkjet device .

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