JP2005174952A - Method of manufacturing ceramic circuit substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a ceramic circuit substrate which can reduce burning strain smaller while preventing problems of stamping unnecessary ruggedness on a front layer conductor or a passive element, causing a foreign matter adhesion, or decreasing a plating property and solder wettability in the method of manufacturing the ceramic circuit substrate by a simultaneously burning step using a restricted sheet. <P>SOLUTION: In the method of manufacturing the ceramic circuit substrate, a resistor 7 and a front layer conductor 8 are formed on an unburned laminate 20 by a transfer method, ceramic green sheets 22, 26 integrated by simultaneous burning are laminated from above the resistor 7 and the front layer conductor 8, thereby obtaining an unburned circuit substrate 30. Thereafter, the restricted sheets 24, 24 are laminated which are not sintered at the burning temperature of the unburned circuit substrate 30, and the unburned circuit substrate 30 is restricted by the restricted sheets 24, 24. The unburned circuit substrate 30 is burned at a temperature of a range that the restricted sheets, 24, 24 are not sintered to obtain a ceramic circuit substrate 32. The ceramic coating layer 35 for covering the restricted sheets 24, 24, the resistor 7 and the front layer conductor 8 is removed to form an overcoating layer 9. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method of manufacturing a ceramic circuit board having a surface layer conductor and passive elements such as a resistor, an inductor, and a capacitor by a co-fire process, and a ceramic circuit board suitably manufactured by the method. . In particular, it is deeply related to a ceramic circuit board having a resistor (resistor) on its surface. Moreover, it is suitable when the ceramic circuit board is a connected ceramic circuit board that is divided into a plurality of ceramic circuit boards.

  A method of manufacturing a ceramic circuit board by manufacturing a green circuit board formed by laminating a ceramic green sheet and a conductor layer, and then co-fireing the ceramic body and the conductor is a simultaneous firing step. It is called (co-fire process). Compared with the process of printing a conductor paste on a fired ceramic circuit board and then baking the conductor paste onto the ceramic circuit board (post-fire process), the co-firing process is a process where the surface layer conductor such as a mounting pad is attached to the ceramic body. There is a great advantage that it can be formed in a batch. In recent years, various ceramic circuit boards in which passive elements such as resistors, inductors and capacitors are built in by simultaneous firing have been studied (Patent Documents 3 to 5 below).

  However, in the co-firing process, the firing contraction timings of the green sheet, the conductor, and the passive element are different, so that firing distortion such as warpage is likely to occur in the finished ceramic circuit board. It is well known that firing strain causes defects such as mounting defects in the mounting process. In addition, the firing strain may affect the electrical characteristics of the passive element, resulting in variations in electrical characteristics.

  Various methods have been studied in order to solve the firing strain problem. As a representative method, firing is performed in a thickness direction (Z direction) by firing an unfired circuit board while being physically constrained from above and below, thereby producing a ceramic circuit having a small firing strain. A method for manufacturing a substrate is known. Specifically, a method of firing while restraining by applying pressure from above and below the unfired circuit board (Patent Document 1 below), or firing in a state where the unfired circuit board is sandwiched between restraint sheets that do not shrink during the firing process Thereafter, there is a method of removing the restraining sheet (Patent Document 2 below).

JP-A-62-260777 JP-A-4-243978 JP 61-212091 A Japanese Patent Laid-Open No. 2-5448 JP-A-5-226840

  In the method of firing an unfired circuit board while restraining it from above and below with a restraint sheet (Patent Document 2), the restraint sheet comes into direct contact with a surface layer conductor such as a mounting pad formed on the substrate surface. Therefore, there is a possibility that unnecessary irregularities are stamped on the surface of the surface layer conductor, foreign matter adheres, and the plating property and solder wettability are deteriorated. In addition, the method of removing the constraining sheet after firing the unsintered circuit board between the constraining sheet that does not shrink during the firing process is a method for removing the constraining sheet in order to improve the adhesion strength and soldering resistance of the surface layer conductor. Is formed thickly (the thickness after firing is 15 μm or more and 50 μm or less). Specifically, there is a problem that the constraining sheet is difficult to partially adhere due to the unevenness of the thick surface layer conductor, and firing distortion is likely to occur in a portion where the constraining is insufficient.

  In addition, when a ceramic circuit board in which passive elements are formed on the substrate surface is manufactured on the premise that the characteristic value is adjusted with a laser trimming apparatus using these means, unevenness caused by particles contained in the restraint sheet is generated. There is a problem that the passive element is stamped on the passive element, or the passive element is removed together when the constraining sheet is removed. There is a method of forming a surface layer conductor or a passive element by a post-fire process, but there is a problem that the number of firings is increased, and the post-fire process is not suitable for forming a fine pattern.

  One object of the present invention is to stamp unnecessary irregularities on surface layer conductors and passive elements, to cause foreign matter adhesion, in a method of manufacturing a ceramic circuit board by a simultaneous firing process using a constraining sheet, It is an object of the present invention to provide a method capable of reducing the firing strain while preventing the occurrence of problems such as deterioration in solderability and solder wettability. Another object is to provide a ceramic circuit board that can be manufactured by the method.

Means for Solving the Problems and Effects of the Invention

In order to solve the above problems, a method for manufacturing a ceramic circuit board according to the present invention includes:
A laminate manufacturing step of manufacturing a laminate formed by laminating the first ceramic green sheet and the conductor layer, an operation of transferring the surface layer conductor formed on the first support to the laminate, and the second support A substrate manufacturing step of manufacturing a green circuit board configured to include the multilayer body, the surface conductor, and the passive element by performing an operation of transferring the passive element formed in the multilayer body to the multilayer body;
A step of coating the passive element and the surface conductor by laminating a second ceramic green sheet integrated with the unfired circuit board by simultaneous firing on the surface of the green circuit board on which the passive element and the surface conductor are formed; ,
A constraining sheet mainly containing a non-sinterable inorganic material that is not sintered at the firing temperature of the unfired circuit board is laminated on both sides of the unfired circuit board coated with the passive element and the surface layer conductor. A restraining step of restraining the fired circuit board;
A firing step of firing the unfired circuit board restrained by the restraint sheet at a temperature in a range where the restraint sheet is not sintered, and producing a ceramic circuit board restrained by the restraint sheet;
A removing step of removing the ceramic covering layer covering the surface layer conductor from the ceramic circuit board constrained by the restraining sheet and the ceramic layer based on the second ceramic green sheet, and exposing the surface layer conductor to the substrate surface; The main feature is to comprise.

  According to the present invention, since firing is performed with the unfired circuit board sandwiched between restraining sheets, firing shrinkage in the XY direction (in-plane direction) is suppressed, and firing shrinkage in the Z direction (thickness direction). As a result, the firing strain (warpage) can be reduced. Since the second ceramic green sheet is interposed between the passive element and the constraining sheet, the concavity and convexity of the constraining sheet is not stamped on the passive element. Further, at the time of firing, the second ceramic green sheet acts to absorb irregularities based on the passive element and the surface layer conductor, so that the constraining sheet is easily adhered to the entire surface, and is uniform within the surface of the unfired circuit board. The restraint force comes to work. Then, the variation in firing strain in the in-plane direction is reduced, and the overall firing strain can be further reduced. Further, the second ceramic green sheet is integrated with the laminate by simultaneous firing. After firing, the ceramic covering layer that covers the surface conductor is removed from the ceramic layer based on the second ceramic green sheet to expose the surface conductor on the substrate surface. At this time, foreign substances (such as coarse ceramic particles) adhering to the passive element and the surface layer conductor can be removed together. As described above, according to the method of the present invention, in the method of manufacturing a ceramic circuit board by the co-firing process using the constraining sheet, unnecessary irregularities are stamped on the surface layer conductor and the passive element, or foreign matter is adhered. The firing strain can be further reduced while preventing the occurrence of problems such as the occurrence of plating problems and the deterioration of solderability. As a result, the variation in the electrical characteristics of the passive elements for each product can be reduced, leading to the provision of a ceramic circuit board with stable performance.

  Further, the following advantages can be obtained by separately transferring the surface conductor and the passive element formed on the support without directly forming the surface conductor and the passive element on the main surface of the multilayer body. First, when the surface conductor and passive elements are directly formed in the laminate, it is common to employ a printing method using a screen mask. In such a printing method, fine wiring can be formed without blurring or the surface layer can be formed. It is difficult to vary the thickness of the conductor in the plane.

  On the other hand, in a method in which a surface layer conductor is separately formed on a support and transferred to a laminate, a surface layer conductor having a thin portion 80 and a thick portion 81 can be formed at a time as shown in FIG. 15 (cross-sectional view). Is possible. Then, the passive element 77 (for example, a resistor) is connected to the surface layer conductor 80 having a small thickness, so that the height position of the upper surface 77p of the passive element 77 is lower than the height position of the upper surface 81p of the surface layer conductor 81. It becomes possible. In this way, as shown in FIG. 16, when the ceramic covering layer 11L formed after firing is removed and the surface conductor 81 is exposed on the surface of the substrate, it is possible to prevent the passive element 77 from being greatly damaged. Further, the thick portion of the surface layer conductor 81 can be suitably used, for example, as a base conductor of a solder bump.

  An intaglio is preferably used for the first support and the second support described above. This is because it is suitable for transferring a fine pattern. And it is desirable that these intaglios have flexibility. The intaglio having flexibility can be deformed following the laminate and has good adhesion to the substrate surface. As a result, the surface layer conductor or passive element formed on the intaglio can be reliably transferred to the laminate. The intaglio having flexibility may be formed using a flexible material, and in particular, it may be formed using a resin material. This is because the intaglio can be easily formed by laser processing or etching. In particular, a heat-resistant and chemical-resistant engineering plastic such as polyimide and a resin having flexibility are preferable. Also, if the surface layer conductor or passive element is formed by appropriately drying the paste filled in the paste filling groove, the solvent contained in the paste will soak into the laminate excessively when it is transferred to the laminate. Is unlikely to occur. This point is also superior to the screen printing method and can be said to be convenient for forming a fine pattern. The order of transferring the surface layer conductor or passive element formed on the intaglio to the laminate is not limited. The order can be changed appropriately according to the design of the product.

  In the covering step, it is desirable to press the surface of the unfired circuit board on which the surface layer conductor is formed, and then laminate a second ceramic green sheet having a thickness of 1 μm to 50 μm. This is because, by adjusting the surface shape of the surface conductor, the adhesion of the restraining sheet can be improved and the restraining force can be made uniform in the surface. More preferably, the surface of the unfired circuit board on which the surface layer conductor is formed is flattened by a press treatment, and then a second ceramic green sheet molded to a thickness of 1 μm to 50 μm is laminated. This is because by flattening, the constraining sheet is more uniformly adhered to the substrate surface, and the constraining force can be more effectively uniformed in the surface. The thickness of the second ceramic green sheet is preferably 1 μm or more and 50 μm or less. This is because when the thickness is less than 1 μm, it is impossible to obtain a sufficient effect of uniforming the restraining force in the surface. On the other hand, if the thickness exceeds 50 μm, a thick ceramic coating layer will be formed on the surface conductor after firing, which makes it difficult to remove or significantly increases the time spent in the removal process. Because it does. As a result, productivity may be sacrificed. Note that “flattening” here does not mean that the surface is completely flat, but means that the step between the substrate surface and the surface layer conductor is corrected relative to that before pressing. To do.

  Moreover, the inorganic material which comprises the above-mentioned 2nd ceramic green sheet and the inorganic material which comprises the 1st ceramic green sheet can use the thing of substantially the same composition suitably. According to this configuration, since the firing temperatures of the first ceramic green sheet and the second ceramic green sheet, that is, the firing timing coincide with each other, both can be easily and reliably integrated. Note that “substantially the same” means that the inevitable impurities are ignored.

  Moreover, you may perform the plating process which forms a plating layer on the surface layer conductor exposed through the removal process. By forming a plating layer on the surface conductor, the surface conductor can be improved. That is, various properties such as solder wettability are improved, and a so-called surface mounting process for mounting a mounting component such as an integrated circuit chip can be satisfactorily performed.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 shows a cross-sectional structure of a ceramic circuit board 1 of the present invention. The ceramic circuit board 1 includes a multilayer circuit portion 2 having a multilayer structure in which ceramic dielectric layers 5 and conductor layers 6 are alternately laminated, and a surface layer conductor formed on the first main surface CP of the multilayer circuit portion 2. 8 and a resistor 7. On the second main surface DP of the multilayer circuit unit 2, a mounting pad 12 for electrical connection with another mounting substrate or the like is formed. 2nd main surface DP shows the main surface on the opposite side to the side in which the resistor 7 was formed. In the laminated circuit portion 2, the conductor layers 6 and 6, the conductor layer 6 and the surface layer conductor 8, and a plurality of via conductors 4 conducting the conductor layer 6 and the mounting pad 12 are provided on the ceramic dielectric layers 5 and 5, respectively. Is provided so as to penetrate through in the thickness direction. These via conductors 4 provide electrical connection between layers. The mounting pad 12 includes a base conductor 13 and a plating layer 14. Although not shown, a structure in which solder bumps and mounting pins are brazed onto the mounting pad 12 using a brazing material (including solder) can also be used.

  On the first main surface CP side of the multilayer circuit portion 2, the non-formation region of the resistor 7 and the surface layer conductor 8 is covered with the surface layer ceramic portion 11. The surface ceramic portion 11 is made of the same material as the ceramic dielectric layer 5 of the multilayer circuit portion 2 and is integrated with the ceramic dielectric layer 5 by simultaneous firing. An overcoat layer 9 is provided on the resistor 7 and the surface conductor 8 so as to extend over both. The overcoat layer 9 made of the glass composition is provided with an opening 9a so that a part of the surface conductor 8 is exposed. The surface layer conductor 8 exposed to the opening 9 a is covered with a plating layer 10. On the plated layer 10, solder bumps for flip chip connection of electronic components such as integrated circuit chips can be provided. That is, the overcoat layer 9 functions as a solder dam. Thus, the terminal pads for forming solder bumps are also included in the concept of the surface conductor 8. A similar overcoat layer 9 ′ is also provided on the second main surface DP side on which the mounting pads 12 are formed.

  FIG. 3 shows a partially enlarged view (cross-sectional view) of the ceramic circuit board 1 of FIG. As shown in FIG. 3, the upper surface 7p of the resistor 7 and the upper surface 8p of the surface conductor 8 are substantially flush with each other. The resistor 7 overlaps with both the pair of surface layer conductors 8 and 8 facing each other in the substrate plane in the vertical direction. Thereby, electrical connection between the resistor 7 and the surface layer conductors 8 and 8 and the surface layer conductors 8 and 8 is achieved. In the present specification, “vertical direction” represents the thickness direction of the ceramic circuit board 1.

  Here, when the resistor 7 is flush with the surface layer conductor 8 as in the ceramic circuit board 1 of the present invention, it is advantageous in disposing electronic components such as an integrated circuit chip at a position close to the resistor 7. It is. In order to mount an electronic component on the ceramic circuit board 1, for example, as shown in FIG. 1, an opening 9a is formed in the overcoat layer 9 to provide solder bumps. When the flatness of the overcoat layer 9 is high, the degree of freedom in arranging the electronic components is high.

  On the other hand, like the conventional ceramic circuit board shown in FIG. 5 (cross-sectional view), the surface conductors 70 and 70 constituting the circuit pattern are connected to both ends of the resistor 71 having a constant thickness. In this case, the overcoat layer 72 exhibits relatively large unevenness. It is necessary to avoid such uneven portions as the arrangement positions of the electronic components.

  In short, the present configuration shown in FIG. 3 is more suitable for high-density mounting than the conventional configuration of FIG. Of course, the formation position of the overcoat layer 9 is not limited to the position covering the resistor 7. However, for example, when the integrated circuit chip is surface-mounted, the flatness of the substrate surface is strongly required, so that the structure like the ceramic circuit substrate 1 is advantageous.

  Further, as shown in FIG. 3, the resistor 7 is formed with a laser trimming portion 7a for adjusting the resistivity so as to excavate the resistor 7. FIG. 4 shows a partially enlarged top view (front view) of the ceramic circuit board 1. From FIG. 4, the relative positional relationship of each part can be easily understood. In the present embodiment, the laser trimming portion 7a is L-shaped, but the shape can be variously adjusted. Further, the laser trimming portion 7a may be protected (covered) with a resin such as epoxy in order to prevent the resistor 7 from being oxidized. The overcoat layer 9 is provided so as to completely cover the rectangular resistor 7 and the connection portion between the resistor 7 and the pair of surface layer conductors 8 and 8.

  Returning to FIG. The plating layer 10 can be composed of, for example, a Ni / Au plating layer. Moreover, you may comprise by the plating layer by the same kind metal (for example, Cu, Ag) as the metal contained in the surface layer conductor 8, and the Ni / Au plating layer formed on this plating layer. The thickness of the plating layer 10 is adjusted to, for example, 1 μm or more and 100 μm or less. On the other hand, the surface layer conductor 8 is a base of the plating layer 10 and is made of the same kind of metal as the conductor layer 6 and the via conductor 4. On the plated layer 10, solder bumps made of solder not containing Pb such as Sn—Pb eutectic solder, Sn—Ag—Cu solder, Sn—Ag solder may be formed.

Hereinafter, the manufacturing process of the ceramic circuit board 1 will be described.
The ceramic circuit board 1 is manufactured using a ceramic green sheet. The ceramic green sheet can be produced by a known doctor blade method. First, raw ceramic powder made of dielectric ceramic (for example, in the case of glass ceramic powder, mixed powder of borosilicate glass powder and ceramic filler powder such as alumina, garnite, BaTiO _3, etc .: average particle size is 0.3 μm or more and 1 μm In the following, solvent (acetone, methyl ethyl ketone, diacetone, methyl isobutyl ketone, benzene, bromochloromethane, ethanol, butanol, propanol, toluene, xylene, etc.), binder (acrylic resin (for example, polyacrylic ester, polymethyl) Methacrylate), cellulose acetate butyrate, polyethylene, polyvinyl alcohol, polyvinyl butyral, etc.), plasticizer (butyl benzyl phthalate, dibutyl phthalate, dimethyl phthalate, phthalate ester) Polyethylene glycol derivatives, tricresol phosphate, etc., peptizers (fatty acids (glycerin triolates, etc.), surfactants (benzenesulfonic acid, etc.), wetting agents (alkyl allyl polyether alcohol, polyethylene glycol ethyl ether, nithyl phenyl glycol) , Polyoxyethylene ester, etc.) are mixed and kneaded to form a slurry, which is applied onto a back sheet such as PET using a doctor blade and dried to a suitable level. Get a sheet.

  Next, a metallized paste for forming via conductors (hereinafter referred to as via conductor paste) is prepared. The metal powder to be used is made of, for example, any one of Ag, AgPt, AgPd, Au, Ni, and Cu, and the average particle diameter is adjusted in the range of 2 μm to 20 μm. A via conductor paste can be obtained by blending and preparing an organic solvent such as butyl carbitol in the metal powder so as to obtain an appropriate viscosity.

Next, a metallized paste (hereinafter referred to as a conductor layer paste) used to form the surface layer conductor 8 and the conductor layer 6 is prepared. The metal powder to be used is preferably the same type as that used in the via conductor paste and having an average particle size adjusted to be as small as 0.1 μm to 3 μm. To this metal powder, an inorganic compound powder having an average particle size of 500 nm or less (preferably 100 nm or less, more preferably 50 nm or less) is blended in the range of 0.5% by mass or more and 30% by mass or less. A conductor layer paste can be obtained by blending and preparing a binder and an organic solvent such as butyl carbitol so as to obtain an appropriate viscosity. The inorganic compound powder may be a ceramic green sheet raw material ceramic powder, or at least one of aluminum oxide (Al ₂ O ₃ ), silicon dioxide (SiO ₂ ), and titanium oxide (TiO ₂ ). You may mix | blend and use the inorganic compound powder (average particle diameter of 100 nm or less, desirably 50 nm or less) which consists of seeds.

Next, a paste used for forming the resistor 7 (hereinafter referred to as a resistor paste) is prepared. Specifically, a resistor paste can be prepared by kneading a conductor powder such as RuO ₂ or LaB ₆ , a powder of a borosilicate glass composition, and an organic binder. For example, with respect to 100 parts by mass of RuO ₂ powder adjusted to an average particle size of 0.01 μm or more and 20 μm or less, glass powder is mixed in a range of 50 parts by mass or more and 500 parts by mass or less, and the organic binder described above is 100 parts by mass of RuO ₂ powder. It mix | blends in 5 to 20 mass parts with respect to a part.

  Using the ceramic green sheet and metallized paste produced as described above, an unfired circuit board is produced as follows. First, as shown in the upper diagram of FIG. 6, a laminated body 20 to be the laminated circuit portion 2 is manufactured.

  Specifically, the unfired via conductor 4 is formed by forming a through hole at a predetermined position of the ceramic green sheet 25 prepared in advance by a technique such as punching or laser and filling via conductor paste. After that, the unfired conductor layer 6 is formed by printing the conductor layer paste on the main surface of the ceramic green sheet 25 by a method such as screen printing. When the formation of the via conductor 4 and the conductor layer 6 is completed in this manner, another ceramic green sheet 25 is overlaid thereon, and the pattern printing / ceramic green sheet lamination process is repeated. The via conductor 4 is exposed on one main surface (first main surface CP), and the base conductor 13 of the mounting pad 12 is formed on the other main surface (second main surface DP). An unfired laminated body 20 is obtained (a laminated body production process).

  In addition, about the via conductor 4, the conductor layer 6, the resistor 7, the surface layer conductor 8, the base conductor 13, etc., it is refused for convenience that the code | symbol before baking and after baking is made the same.

  Next, the surface conductor 8 and the resistor 7 are disposed on the first main surface CP of the multilayer body 20. Specifically, a method of transferring the surface conductor 8 and the resistor 7 patterned on a support (transfer jig) different from the laminate 20 to the laminate 20 can be employed. The transfer process is shown in FIGS.

  For the above transfer step, first, as shown in FIG. 11, a first support 40 having a paste filling groove 40 a for forming the surface conductor 8 is prepared. The first support 40 is made of, for example, a resin material such as polyimide, PET, PC, or PEEK, and can be a flexible sheet. The paste filling groove 40a is patterned by laser processing, chemical etching, or a combination thereof. As shown in FIG. 11, the paste 44 for the conductor layer is filled with the squeegee 46 in the paste filling groove 40 a. As a result, the surface conductor 8 is formed on the first support 40. The surface layer conductor 8 formed on the first support 40 may be appropriately dried. In addition, after drying once, an operation of filling the paste filling groove 40a with the conductor layer paste 44 again can be performed. In this way, the volume decrease due to drying can be compensated, and the shape accuracy of the surface conductor 8 can be improved.

  Returning to FIG. As described above, the surface layer conductor 8 formed in the paste filling groove 40a of the first support 40 is transferred to the separately produced laminate 20. That is, the first support body 40 is superposed on the first main surface CP of the multilayer body 20, and pressure is appropriately applied so that the surface layer conductor 8 is in close contact with the multilayer body 20. Thereafter, as shown in FIG. 7, only the first support 40 is separated from the multilayer body 20, thereby transferring the surface conductor 8 to the multilayer body 20.

  In order to prevent the surface conductor 8 from being peeled off from the multilayer body 20 when performing the operation of separating the first support 40 from the multilayer body 20, it is effective to take the following measures. It is. One is to give an appropriate taper to the paste filling groove 40a of the first support 40 as shown in FIG. Such a taper can be easily provided by using laser light in an ultraviolet wavelength region that can be finely processed when the paste filling groove 40a is formed by laser processing. Specifically, it is preferable to perform laser processing using a short wavelength laser such as excimer laser, Nd: YAG laser 3rd harmonic (355 nm) or 4th harmonic (266 nm).

Another means capable of enhancing the ease of peeling between the first support 40 and the surface conductor 8 is that the first filling layer 40a is filled with the conductor layer paste 44 in the paste filling groove 40a as shown in FIG. 1 is to form an auxiliary peeling film 40t on the surface of the support 40 on which the paste filling groove 40a is formed. A specific example of the peeling assist film 40t is a fluorocarbon film. Such a fluorocarbon film is formed by using an O ₂ plasma asher in a solution in which a substance containing a fluorocarbon group and a chlorosilane group, for example, CF ₃ (CF ₂ ) ₇ (CH ₂ ) ₂ SiCl ₃ is dissolved in an organic solvent. It can form by immersing the 1st support body 40 which processed. As shown in FIG. 13, it is desirable that the peeling assisting film 40t be formed on the first support 40 in which the paste filling groove 40a is tapered. By taking the above measures, the surface layer conductor 8 can be smoothly peeled off from the first support 40, and the problem that the surface layer conductor 8 is not successfully transferred can be prevented.

  Returning to FIG. After the surface layer conductor 8 is formed on the multilayer body 20, the first main surface CP of the multilayer body 20 can be pressed to increase the adhesion between the surface layer conductor 8 and the stacked body 20 (surface pressing step). . According to this step, the surface conductor 8 is slightly submerged into the multilayer body 20. Then, the difference in height between the surface conductor 8 and the first main surface CP of the multilayer body 20 can be reduced, and a shape close to a flash circuit in which the surface of the conductor coincides with the surface of the dielectric can be realized.

  Next, the resistor 7 is disposed on the multilayer body 20 by a method similar to the method for forming the surface conductor 8 (transfer method). That is, the resistor 7 is formed by filling the paste filling groove 42 a of the second support 42 with a resistor paste prepared in advance. And the resistor 7 formed on the 2nd support body 42 is transcribe | transferred to the laminated body 20 by which the surface layer conductor 8 is arrange | positioned. Then, surface pressing is performed from the first main surface CP side of the multilayer body 20 so that the resistor 7 is in close contact with the surface conductor 8. By performing the above operation, an unfired circuit board 30 composed of the resistor 7, the surface conductor 8, and the laminated body 20 is obtained (substrate manufacturing process). Note that the arrangement order of the surface conductor 8 and the resistor 7 may be opposite to that of the present embodiment.

  Next, as shown in FIG. 8, the second ceramic green sheets 22 and 26 are laminated on both the main surfaces CP and DP of the unfired circuit board 30 (covering step). The thickness of the second ceramic green sheets 22 and 26 is just enough to fill the step formed by disposing the resistor 7 and the surface layer conductor 8. In this way, the restraining force of the restraining sheets 24, 24, which will be described later, acts uniformly in the plane, so that the effect of reducing the firing strain can be further expected.

  The second ceramic green sheets 22 and 26 are prepared by preparing an inorganic material having substantially the same composition as the first ceramic green sheet 25 constituting the unfired circuit board 30 and an organic material such as a solvent and a binder. What was done can be used conveniently. Specifically, the second ceramic green sheets 22 and 26 can be produced by a forming method such as a doctor blade method using the slurry for forming the green sheet used for the production of the first ceramic green sheet 25. In such cases, the lowest cost can be expected. However, the first ceramic green sheet 25 and the second ceramic green sheets 22 and 26 are produced by using different inorganic materials to be used in the same composition as long as the firing timings are within the same range. May be. Furthermore, you may produce using another material. For example, when a ceramic layer based on the second ceramic green sheets 22 and 26 is caused to function as a circuit element, it may be possible to positively adjust the dielectric constant. In place of the second ceramic green sheets 22 and 26, a ceramic paste may be applied to form a ceramic paste application layer.

Next, as shown in FIG. 8, the non-sinterable inorganic material that is not sintered at the firing temperature of the unfired circuit board 30 on both sides of the unfired circuit board 30 covered with the second ceramic green sheets 22 and 26. The constraining sheets 24 and 24 containing the material as a main body are laminated (restraining step). When the ceramic circuit board 1 is made of a low-temperature fired ceramic (glass ceramic) as in this embodiment, the restraint sheets 24, 24 are, for example, one or more selected from Al ₂ O ₃ , ZrO ₂ and BN. The ceramic green sheet mainly composed of the hardly sinterable inorganic material can be used. That is, the constraining sheets 24, 24 may be of any composition that is not sintered at the firing temperature of the unfired circuit board 30. Note that “mainly” or “including as a main body” means containing the largest amount by mass%.

  Next, as shown in FIG. 9, the unfired circuit board 30 restrained by the restraining sheets 24 and 24 is fired at a temperature in a range where the restraining sheets 24 and 24 are not sintered. This firing temperature range is a temperature in a range where the second ceramic green sheets 22 and 26 and the unfired circuit board 30 are sintered and integrated, and the restraint sheets 24 and 24 are not sintered. In this way, the ceramic circuit board 32 restrained by the restraining sheets 24, 24 can be manufactured (firing process). In addition, said baking temperature range can be 800 degreeC or more and 1000 degrees C or less (for example, 950 degreeC) common with a low-temperature baking ceramic. Moreover, you may bake in the atmosphere pressurized rather than atmospheric pressure, or you may bake, pressing the restraint sheets 24 and 24 mechanically.

  The ceramic circuit board 32 (work board) at the end of firing has a ceramic layer 34 derived from the second ceramic green sheet 26. The ceramic layer 34 includes a ceramic coating layer 35 that covers the resistor 7 and the surface conductor 8 and a surface ceramic portion 11 that has a role of filling between the adjacent surface conductors 8 and 8. The constraining sheets 24 and 24 and the ceramic coating layer 35 covering the resistor 7 are removed from the ceramic circuit board 32 by wet sand blasting or polishing to expose the resistor 7 and the surface conductor 8 on the substrate surface (removal step). ). Since the restraint sheets 24 and 24 and the ceramic covering layer 35 are different from each other in ease of removal, their removal methods may be different from each other. Specifically, a procedure of removing the restraining sheets 24, 24 by wet sand blasting and removing the ceramic coating layer 35 by mechanical polishing, chemical etching, or a combination thereof can be shown.

  Both the ceramic coating layer 35 and the surface ceramic portion 11 are obtained by firing the second ceramic green sheet 26. Although the resistor 7 and the ceramic coating layer 35, and the surface conductor 8 and the ceramic coating layer 35 are integrated, if the thickness d1 of the ceramic coating layer 35 is sufficiently small (for example, 50 μm or less), the removal is compared. Easy and almost no foreign matter remains.

  In order to ensure the ease of removal of the ceramic coating layer 35, it is desirable to use the second ceramic green sheets 22 and 26 laminated on the unfired circuit board 30 so as to have a thickness of 1 μm to 50 μm. When the thickness of the second ceramic green sheets 22 and 26 is less than 1 μm, it is not possible to obtain a sufficient effect of uniforming the restraining force in the plane. On the other hand, if the thickness exceeds 50 μm, a thick ceramic coating layer 35 is formed on the surface of the resistor 7 after firing, and it becomes difficult to remove this, or the time spent in the removal process There is a risk that productivity will be greatly sacrificed by a significant increase.

  Also on the second main surface DP side, the ceramic coating layer 37 covering the base conductor 13 is removed in the same manner as the first main surface CP side. The ceramic coating layer 37 is a part of the ceramic layer 38 derived from the second ceramic green sheet 22 laminated on the second main surface DP side, and the thickness d2 is a ceramic coating layer on the first main surface CP side. Is approximately equal to a thickness d1 of 35. A part of the ceramic layer 38 remains as a surface ceramic part 36 that covers the second main surface DP.

  Next, as shown in FIG. 10, an overcoat layer 9 is formed on the resistor 7 and the surface conductor 8 exposed on the substrate surface (overcoat layer forming step). The overcoat layer 9 is provided with an opening 9 a for an external connection terminal at a position overlapping the surface layer conductor 8. A similar overcoat layer 9 ′ is also formed on the back side where the underlying conductor 13 is exposed. The overcoat layers 9 and 9 'can be formed by applying a glass paste containing a lead silicate or lead borosilicate low melting point glass composition by a screen printing method or the like and baking it. The firing temperature range of this glass paste is set to a temperature range lower than the firing temperature range of the unfired circuit board 30.

  Next, the plating layer 10 is formed on the surface layer conductor 8 exposed from the opening 9a of the overcoat layer 9 (plating process). Similarly, on the opposite side, the mounting pad 12 is obtained by forming the plating layer 14 on the base conductor 13. This plating process can be a plating process of the same type of metal as the surface conductor 8, and the plating layer 10 can be a Cu plating layer, for example. Further, by forming a Ni / Au plating layer on these plating layers, the Ni / Au plating layer can be formed on a plating metal layer with few pits. According to this procedure, a denser Ni / Au plating layer can be formed, which contributes to improving the solder wettability of the plating layer 10. However, an electroless Ni / Au plating layer may be directly formed on the surface conductor 8. Further, the conductive bumps may be formed by plating.

  Next, the resistance is adjusted by irradiating the resistor 7 with laser light through the overcoat layer 9 (laser trimming step). It is preferable to cover and protect the laser trimming portion 7a formed by this process with a resin such as epoxy because the resistor 7 can be prevented from being oxidized. The ceramic circuit board 1 is manufactured through the steps described above.

  The ceramic circuit board 1 shown in the present embodiment is generally manufactured in the form of a multi-piece ceramic circuit board 85 as shown in FIG. Each ceramic circuit board 1 is folded along the dividing grooves 112. When the ceramic circuit board to be manufactured is a connected ceramic circuit board 85 that becomes a plurality of ceramic circuit boards 1 by division, the warp problem becomes more serious, and therefore it is particularly effective to apply the manufacturing method of the present invention. It is.

  By the way, according to the method of forming a surface layer conductor on a resin support and transferring only the surface layer conductor to the unfired laminated body 20 as in this embodiment, the thickness is within the same plane. Different surface layer conductors can be formed at a time. FIG. 14 shows a schematic cross-sectional view of the ceramic circuit board 100 in which the thickness of the surface conductor 81 for solder bump formation is adjusted to be large while the thickness of the surface conductor 80 that is in direct contact with the resistor 77 is adjusted to be small. It is. Except for the surface layer conductors 80 and 81, the resistor 77, and the laser trimming portion 77a, the configuration is substantially the same as that of the embodiment of FIG.

  By forming the surface conductors 80 and 81 having different thicknesses, the following advantages arise. First, as shown in FIG. 15, surface conductors 80 and 81 are formed on the first main surface CP of the multilayer body 20. Such surface layer conductors 80 and 81 can be realized by adjusting the depth of the paste filling grooves 48a and 48b of the support 48 for forming the surface layer conductors 80 and 81 as shown in FIG. Furthermore, the laminated body 20 is provided with the resistor 77. At this time, the resistor 77 is arranged so as to overlap only the surface layer conductor 80 whose thickness is adjusted to be small. By doing so, it becomes possible to make the height position of the upper surface 77p of the resistor 77 coincide with the height position of the upper surface 81p of the surface layer conductor 81 whose thickness is adjusted to be large or lower. The present embodiment shows a matching example.

  Then, in the state shown in the lower diagram of FIG. 15, as described above, the stacking step and the simultaneous firing step of the second ceramic green sheet 26 and the restraining sheet 24 are sequentially performed. After the firing step, the unsintered constraining sheet 24 and the ceramic coating layer 11L based on the second ceramic green sheet 26 are removed by blasting or polishing (removal step). When removing the ceramic covering layer 11L, the surface conductor 81 to be exposed on the substrate surface is formed in a bulky manner, so that the resistor 77 is not greatly ground. That is, it is easy to obtain electrical characteristics as designed. Further, as shown in FIG. 14, the surface layer conductor 81 exposed on the substrate surface is plated on a portion exposed from the opening 9a of the overcoat layer 9, and is preferably used as a terminal pad for forming solder bumps. It becomes.

  Further, even when the resistor 77 is disposed first and the surface conductors 80 and 81 are disposed so as to cover the resistor 77, the overlapping portion with the resistor 77 is configured by the thin surface conductor 80. Thus, the overlapping portion can be prevented from protruding. As a result, the difficulty of the process (removal process) of exposing the surface conductor 81 to be a terminal pad for forming solder bumps is reduced.

The cross-sectional schematic diagram of a ceramic circuit board. Schematic diagram of a multi-cavity ceramic circuit board. The partial expanded sectional view of FIG. FIG. 2 is a partially enlarged top view of the ceramic circuit board of FIG. 1. The expanded sectional view of the resistor in the conventional ceramic circuit board. FIG. 3 is an explanatory diagram of a manufacturing process of the ceramic circuit board of FIG. 1. FIG. 7 is an explanatory diagram of the manufacturing process of the ceramic circuit board following FIG. 6. FIG. 8 is an explanatory diagram of a manufacturing process of the ceramic circuit board following FIG. 7. FIG. 9 is a manufacturing process explanatory diagram of the ceramic circuit board following FIG. 8. FIG. 10 is an explanatory diagram of the manufacturing process of the ceramic circuit board following FIG. 9. Explanatory drawing of the procedure which forms a surface layer conductor on a 1st support body. The expanded sectional view of the 1st support body which gave the taper to the paste filling groove. The expanded sectional view of the 1st support body in which the peeling auxiliary | assistant film | membrane was formed. 4 is another embodiment of a ceramic circuit board. The figure explaining the principal part formation procedure of the ceramic circuit board of FIG. Similarly, the figure explaining the principal part formation procedure of the ceramic circuit board of FIG. The cross-sectional schematic diagram of the support body which can form the surface layer conductor from which thickness differs at a time.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,100 Ceramic circuit board 2 Laminated circuit part 4 Via conductor 5 Ceramic dielectric layer 6 Conductor layer 7, 77 Resistor 7a, 77a Laser trimming part 8, 80, 81 Surface layer conductor 9 Overcoat layer 10 Plating layer 11, 11K Surface layer Ceramic part 20 Laminate 22, 25, 26 Ceramic green sheet 24 Restraint sheet 30 Unfired circuit board 34 Ceramic layer 35, 11L Ceramic coating layer 40, 42 Support body 40a, 42a Paste filling groove CP First main surface

Claims (5)

A laminate production step of producing a laminate formed by laminating the first ceramic green sheet and the conductor layer;
By performing the operation of transferring the surface layer conductor formed on the first support to the laminate, and the operation of transferring the passive element formed on the second support to the laminate, the laminate and the surface conductor And a substrate manufacturing process for manufacturing an unfired circuit board configured to include passive elements,
On the surface of the green circuit board on which the passive element and the surface layer conductor are formed, a second ceramic green sheet that is integrated with the green circuit board by simultaneous baking is laminated to form the passive element and the surface layer conductor. A coating process for coating
A constraining sheet mainly comprising a hardly sinterable inorganic material that is not sintered at the firing temperature of the unfired circuit board is laminated on both sides of the unfired circuit board coated with the passive element and the surface layer conductor. A constraining step of constraining the green circuit board with a sheet;
Firing the unfired circuit board restrained by the restraining sheet at a temperature in a range where the restraining sheet is not sintered, and producing a ceramic circuit board restrained by the restraining sheet;
The ceramic covering layer covering the surface layer conductor is removed from the ceramic layer based on the restraint sheet and the second ceramic green sheet from the ceramic circuit board restrained by the restraint sheet, and the surface layer conductor is disposed on the substrate surface. Removing process to be exposed to,
A method for producing a ceramic circuit board, comprising:   The first support is an intaglio in which paste filling grooves for forming the surface conductor are patterned, and the second support is an intaglio in which paste filling grooves for forming the passive elements are patterned. The method for manufacturing a ceramic circuit board according to claim 1, wherein the intaglio has flexibility.   In the covering step, the surface of the unfired ceramic substrate on which the surface conductor layer is formed is pressed, and then the second ceramic green sheet molded to a thickness of 1 μm to 50 μm is laminated. A method for manufacturing a ceramic circuit board according to claim 1 or 2.   The inorganic material constituting the second ceramic green sheet and the inorganic material constituting the first ceramic green sheet have substantially the same composition. A method for producing a ceramic circuit board according to Item.   5. The method for manufacturing a ceramic circuit board according to claim 1, further comprising a plating step of forming a plating layer on the surface conductor exposed through the removing step. 6.

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