JP2006108126A - Printed wiring board and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the size of a resistive element and to prevent a decline in reliability due to a difference in level, etc. <P>SOLUTION: The printed wiring board comprises a substrate 20, an insulating layer 30 formed on the substrate 20, a pair of second interconnection layers 90A and 90B selectively formed on the insulating film 30. The printed wiring board includes, inside the insulating layer 30, a pair of first interconnection layers 40A and 40B selectively formed on the substrate 20, a pair of conductive layers 50A and 50B which are formed between the first interconnection layers 40A and 40B by half-etching the first interconnection layers 40A and 40B, noble metal layers 60A and 60B so formed as to cover part of the conductive layers 50A and 50B, resistor 70 formed in close contact with the noble metal layers 60A and 60B between the conductive layers 50A and 50B, and connection layer 80 for electrically connecting the first interconnection layers 40A and 40B and the second interconnection layers 90A and 90B. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a printed wiring board in which passive elements such as LCR are embedded in advance and a method for manufacturing the same, and in particular, the size of a built-in resistance element can be reduced and a decrease in reliability due to a step or unevenness is prevented. The present invention relates to a printed wiring board to be obtained and a manufacturing method thereof.

  In recent years, with the demand for higher performance and smaller size of electronic devices, the density and functionality of circuit components have been further increased. For example, when an electronic component is mounted on a printed wiring board, a passive element such as a capacitor element (C), a resistor element (R), or an inductor element (L) is used as a substrate in order to provide a noise reduction function while increasing the mounting density. A printed wiring board with a built-in structure is used.

  Since such a printed wiring board incorporates a passive element, a passive element that is smaller than a normal passive element is desired. For example, as a resistance element having a structure suitable for being incorporated in a printed wiring board, a resistance element having a structure in which a resistance material is disposed between resistance element electrodes (conductive layers) is widely known. As a method for arranging the resistors, a method of patterning by etching or the like after plating or resistive metal foil is laminated (for example, refer to Patent Document 1), and a wiring circuit (wiring layer) and a resistance element electrode (conductive layer) are formed. There is a method of partially laminating a resin-based resistor later by screen printing or the like (for example, see Patent Document 2). Of these, the latter method has the advantage that the material can be used more efficiently and the number of steps can be reduced compared to the former method.

  However, when the resistance element is formed by the latter method, as shown in FIG. 6, the resistance element electrodes (conductive layers) 120A and 120B made of a part of the copper wiring and the resistor 130 made of carbon paste are in direct contact with each other. The influence of the contact resistance at the interface is increased. In particular, under high temperature and high humidity conditions (temperature 40 ° C., relative humidity 95%), the resistance value greatly increases due to interface corrosion or the like (see, for example, Non-Patent Document 1).

  Therefore, as shown in FIG. 7, the contact resistance at the interface is suppressed by sandwiching the silver pastes 140A and 140B having excellent electrical connectivity between the resistance element electrodes (conductive layers) 120A and 120B and the resistor 130. A resistive element having a structure has been devised. In addition, there is a resistive element in which the resistive element electrode portions (conductive layers) 120A and 120B are subjected to gold plating (see, for example, Patent Document 3).

In this way, by forming a structure in which the silver pastes 140A and 140B are disposed between the resistance element electrode portions (conductive layers) 120A and 120B and the resistor 130, a resistance element in which the influence of the contact resistance at the interface is suppressed is formed. Can do.
JP 2003-168851 A JP-A-1-295482 Japanese Patent Laid-Open No. 11-340633 Isao Shioka: "Polymer resistor used in embedded passive component technology", Journal of Japan Institute of Electronics Packaging, VOL. 6, NO. 4, pp. 294-299, 2003

  However, in the printed wiring board having the structure shown in FIG. 7, the length of the resistor 130 is the silver paste 140A and the silver paste 140B printed on the resistance element electrodes 120A and 120B and inside the resistance element electrodes 120A and 120B. Therefore, the printing accuracy of the silver pastes 140A and 140B affects the length of the resistance element. Since the silver pastes 140A and 140B are printed on the resistance element electrodes 120A and 120B and the substrate 110 having steps, the printing accuracy may be slightly reduced. Therefore, it is difficult to adjust the length of the resistance element to the design value as compared with the structure of FIG. 6 in which the distance between the resistance element electrodes 120A and 120B formed by etching is the length of the resistor 130. In order to increase the accuracy of adjustment to this design value, it is necessary to perform laser trimming of the resistor. However, correcting everything on the substrate 110 by laser trimming is cumbersome and costly. Also, an element that is too large and deviated from the standard is unrealistic due to problems such as an inability to be corrected because the electrical characteristics deteriorate. In summary, the structure shown in FIG. 7 is that the printing accuracy of the silver pastes 140A and 140B is reduced due to the step, and the length of the resistor 130 is out of the design value, and the reliability is lowered. Is in an unavoidable situation.

  Further, when the silver pastes 140A and 140B are sandwiched between the resistor 130 and the resistor element electrodes 120A and 120B, there is a problem that the size of the resistor element increases.

  In addition, in order to achieve good conductivity, silver pastes 140A and 140B highly filled with silver filler are screen-printed on the resistance element electrodes 120A and 120B and the stepped portion 150 on the resin substrate 110. There is a concern that a crack 151 may occur in the stepped portion 150, which may reduce the reliability of the resistance element.

  Further, since the silver pastes 140A and 140B or the resistor 130 are screen-printed on the resin substrate 110 on which the wiring unevenness exists, the silver paste or carbon paste is likely to bleed or scatter during printing. Therefore, it is difficult to increase the density between the resistance elements or between the resistance element wirings, and it is easy to reduce the reliability of insulation.

  The present invention has been made in view of the above circumstances, and provides a printed wiring board capable of reducing the size of a built-in resistance element and preventing deterioration in reliability due to a step or unevenness and a method for manufacturing the same. Objective.

  The invention corresponding to claim 1 includes a substrate, a pair of wiring layers selectively formed on the substrate, and a pair of conductive layers formed by partially etching each of the wiring layers. A pair of noble metal layers plated to cover each conductive layer, and selectively printing on each noble metal layer and the substrate between the conductive layers so as to electrically connect each conductive layer And a printed wiring board having a resistor formed in this manner.

  The invention corresponding to claim 2 is the printed wiring board corresponding to claim 1, wherein each of the noble metal layers is a printed wiring board made of a silver plating film.

  The invention corresponding to claim 3 is the printed wiring board corresponding to claim 1 or claim 2, wherein the surface of each conductive layer is roughened.

  The invention corresponding to claim 4 includes a step of selectively forming a pair of wiring layers on a substrate and a first opening that exposes a part of each wiring layer to cover each wiring layer. A step of selectively forming a resist layer on the substrate, a step of half-etching the wiring layers in the first opening to form a pair of conductive layers, and the half-etched conductive layers Forming a pair of noble metal layers on a part of the substrate, removing the resist layer after forming the noble metal layer, and forming a resistor on the substrate between the conductive layers and on the noble metal layers. A printed wiring board manufacturing method comprising the steps.

  The invention corresponding to claim 5 is the method of manufacturing a printed wiring board corresponding to claim 4, wherein the step of forming each noble metal layer is a step of forming a silver plating film as each noble metal layer by a silver plating process. Is a method of manufacturing a printed wiring board containing

  The invention corresponding to claim 6 is the method of manufacturing a printed wiring board corresponding to claim 4 or claim 5, wherein the half etching is performed between the half etching step and the step of forming the noble metal layer. It is the manufacturing method of the printed wiring board which further comprised the process of roughening each conductive layer.

<Action>
Therefore, in the invention corresponding to claim 1, by taking the above-mentioned means, a pair of noble metal layers plated so as to cover a part of each conductive layer, and each noble metal layer between each conductive layer Compared to the conventional structure shown in FIG. 7, the structure including the resistor formed on the upper portion does not print the noble metal layer on the substrate between the conductive layers. It is possible to eliminate the decrease in printing accuracy caused by the level difference. Furthermore, since each conductive layer is thinned by half etching in advance, it is possible to prevent a decrease in printing accuracy due to the unevenness of the wiring. Therefore, it is possible to provide a printed wiring board having a built-in resistor element that can reduce the size of the built-in resistor element and can prevent a decrease in reliability due to a step or unevenness.

  Since the invention corresponding to claim 2 is a printed wiring board made of a silver plating film as each noble metal layer, there is a tendency that the balance of the characteristics is good in spite of its low cost compared with other noble metals. Therefore, in addition to the operation corresponding to claim 1, it is possible to provide a printed wiring board that incorporates a resistor element that is inexpensive and has excellent characteristics.

  In the invention corresponding to claim 3, since the surface of each conductive layer is roughened, in addition to the action corresponding to claims 1 and 2, the adhesion of the resistor is improved and the reliability is excellent. A printed wiring board having a built-in resistance element can be provided.

  Since the invention corresponding to claim 4 includes a step of forming a resistor so that each noble metal layer is in close contact with each half-etched conductive layer, the conductive layer is thinned by half-etching, and the printing accuracy is good. A noble metal layer can be formed with high accuracy.

  In addition, since the noble metal layer is not printed on the substrate between the conductive layers, the size of the resistance element can be reduced. Therefore, it is possible to provide a printed wiring board having a built-in resistance element that can reduce the size of the resistance element and prevent a decrease in reliability due to a step or unevenness.

  In the invention corresponding to claim 5, since the silver plating film is formed as the step of forming the noble metal layer, in addition to the action corresponding to claim 4, the balance of characteristics despite the low cost compared to other noble metals. A good printed wiring board can be manufactured.

  Since the invention corresponding to claim 6 further includes a step of roughening each half-etched conductive layer, in addition to the action corresponding to claims 4 and 5, the adhesion of the resistor is improved. In addition, it is possible to provide a printed wiring board having a built-in resistance element with excellent reliability.

  As described above, according to the present invention, it is possible to provide a printed wiring board capable of reducing the size of a built-in resistance element and preventing a decrease in reliability due to a step or unevenness and a method for manufacturing the same.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a sectional view showing an example of the structure of a printed wiring board according to an embodiment of the present invention. The printed wiring board 10 includes a substrate 20, an insulating layer 30 formed on the substrate 20, and a pair of second wiring layers 90 </ b> A and 90 </ b> B selectively formed on the insulating layer 30.

  Further, the printed wiring board 10 includes the resistance element 11 in the insulating layer 30, and a pair of first wiring layers 40 </ b> A and 40 </ b> B selectively formed on the substrate 20 and the first wiring layer 40 </ b> A. A pair of conductive layers 50A and 50B formed by half-etching each of the first wiring layers 40A and 40B between the first wiring layer 40B and a part of each of the conductive layers 50A and 50B. A pair of formed noble metal layers 60A and 60B, and a resistor 70 formed so as to be in close contact with the noble metal layers 60A and 60B between the conductive layers 50A and 50B. Here, it is sufficient that at least one pair of conductive layers for the resistance elements is provided, and as many resistance layers as necessary can be provided. Furthermore, a capacitor power supply and an inductor may be formed at the same time.

  Further, in the resistance element 11, the first wiring layers 40A and 40B and the second wiring layers 90A and 90B are electrically connected by the connection layers 80A and 80B. Here, the first wiring layers 40A and 40B and the second wiring layers 90A and 90B are connected by the connection layer. However, the present invention is not limited to this. The layer may penetrate the substrate and be connected to the first wiring layers 40A and 40B from below or may be directly connected to the conductive layer.

  The resistance element 11 includes a resistor 70, conductive layers 50A and 50B, and noble metal layers 60A and 60B.

  The substrate 20 is a resin substrate on which the insulating layer 30 is formed. In addition, the resistance element 11 is provided on the substrate 20.

  The insulating layer 30 may be in the form of a prepreg, a resin-coated copper foil, an insulating resin film for a build-up board, or a varnish, but the embedding property and workability of the resistance element 11 built in the printed wiring board 10 In view of the above, it is preferable to use an insulating resin film for build-up substrates. In general, a thermosetting resin such as an epoxy resin tends to have a higher crosslinking density as the curing temperature becomes higher. For example, when the resistor 70 that has been cured once is heated at a higher temperature, the curing of the thermosetting resin proceeds. The resistance value tends to decrease. Therefore, from the viewpoint of reducing the change in the resistance value before and after the resistance element 11 is embedded in the printed wiring board 10, the maximum temperature achieved during pressing, laminating, and curing of the insulating resin is the maximum temperature achieved when the resistor 70 is cured. Is preferably lower.

  The first wiring layers 40A, 40B are conductor circuit wirings formed on the substrate 20 in the insulating layer 30, and are formed of, for example, copper. The first wiring layers 40A and 40B are electrically connected to the conductive layers 50A and 50B and function as part of an electric circuit on the printed wiring board 10 as shown in FIG. 2 (top view). .

  The conductive layers 50A and 50B are electrodes of a resistance element, and are formed of, for example, copper. The first wiring layers 40A and 40B are formed by half-etching and are electrically connected to the first wiring layers 40A and 40B. From the viewpoint of achieving both connection reliability and printing reliability, half etching is preferably performed so that the thickness of the conductive layer is in the range of 5 to 15 μm.

  The conductive layers 50A and 50B (surfaces on which the noble metal layers 60A and 60B are formed) are roughened by chemical treatment. The surface roughness Ra due to roughening is preferably in the range of 1.0 to 2.0 μm. This is because when the surface roughness Ra is less than 1.0 μm, even if the noble metal plating process is performed, the uneven shape is buried by the noble metal plating, and sufficient adhesion to the resistor 70 and the insulating layer 30 cannot be obtained. It is. On the other hand, if the surface roughness Ra exceeds 2.0 μm, the electrode shapes of the conductive layers 50A and 50B are destroyed, and it becomes difficult to adjust the resistance elements to the design values.

  The noble metal layers 60A and 60B are noble metal thin films covering portions of the conductive layers 50A and 50B, respectively, and are formed of silver or gold. Silver is often used from the viewpoint of cost reduction. When silver is used, the noble metal layers 60A and 60B are formed by substitutional electroless silver plating. By applying this substitutional electroless silver plating treatment only to the portion in contact with the resistor 70, the plating area is smaller than when silver is applied to the entire surface of the conductive layers 50A and 50B, thereby reducing the cost of silver plating. ing. In addition, even if the pitch between the conductive layer 50A and the conductive layer 50B is fine, there is an effect that there is little fear of migration. In addition, it is preferable that the plating thickness of silver plating exists in the range of 0.2 micrometer or more and 0.4 micrometer or less. This is because when the thickness of the silver plating is less than 0.2 μm, the contact resistance between the resistor 70 and the conductive layers 50A and 50B cannot be sufficiently reduced, whereas when the thickness exceeds 0.4 μm, the contact resistance cannot be reduced. . If the surface roughness of the conductive layers 50A and 50B is in the range of 1.0 to 2.0 μm and the thickness of the noble metal layer is in the range of 0.2 to 0.4 μm, the contact resistance can be sufficiently reduced, In addition, adhesion can be maintained.

  The resistor 70 is mainly composed of a thermosetting resin and a conductive filler. As the thermosetting resin, a thermosetting resin such as an epoxy resin, a phenol resin, a melamine resin, or a polyimide resin, a resin obtained by modifying the thermosetting resin, a mixture of these resins and a thermoplastic resin, or the like can be used. In particular, it is preferable to use an epoxy resin from the viewpoint of adhesion to the substrate 20, chemical resistance, and cost. It is preferable to use inexpensive carbon as the conductive filler. In addition to the conductive filler, an inorganic filler such as silica may be added. A commercially available carbon paste can be used as it is.

  The viscosity of the resistor 70 is not particularly limited, but is preferably about 500 to 1000 poise when performing screen printing with a metal mask. This is because when the viscosity is less than 500 poise, the resistance paste is applied after printing and the printed shape tends to deteriorate. On the other hand, if the viscosity is more than 1000 poise, even if leveling is performed after printing, bubbles mixed during printing are difficult to escape and cracks may occur in the resistor 70 due to the bubbles.

The connection layers 80A and 80B are formed by via-processing the insulating layer 30 with a CO ₂ laser or the like, and then performing electroless copper plating and electrolytic copper plating to electrically connect the first wiring layers 40A and 40B and the second wiring layers 90A and 90B. Connected.

  The second wiring layers 90 </ b> A and 90 </ b> B are conductor circuit wirings formed on the insulating layer 30. The resistance element 11 formed in the insulating layer 30 can be used by being electrically connected to the first wiring layers 40A and 40B.

  Next, an example of a method for manufacturing a printed wiring board configured as described above will be described with reference to the process cross-sectional views of FIGS.

  First, the copper foil on the surface of the single-sided copper-clad laminate (first metal layer) 41 on the substrate 20 is etched to form a pair of first wiring layers 40A and 40B (FIGS. 3A and 3B). )).

  Subsequently, a commercially available plating resist 100 is laminated on the substrate 20 with a roll laminator, and the formation region of the resistor 70 is exposed and developed to form the opening 101 (FIGS. 3C and 3D).

  Note that the photosensitive resin used in the plating resist 100 may be in either a dry film or liquid form, and a commercially available plating resist, a photosensitive insulating resin film for build-up multilayer printed wiring boards, or a varnish is used as it is. Also good. Here, when using the photosensitive insulating resin for build-up multilayer printed wiring boards, the insulating insulating resin is not removed, and after exposing and developing to form the opening 101, the photosensitive insulating resin is thermally cured. After the resistor 70 is printed, formed and dried in the opening 101 thus formed, the insulating layer 30 is formed again with an insulating resin film or varnish. Thereafter, multilayering is performed in the same manner as in a normal build-up multilayer printed wiring board process.

  Next, part of the first wiring layers 40A and 40B in the opening 101 is half-etched to form conductive layers 50A and 50B, and then treated with a chemical solution such as MEC-etch bond CZ-8101, for example. The surfaces of 50A and 50B are roughened within a surface roughness Ra of 1.0 to 2.0 μm (FIG. 3E). From the viewpoint of achieving both connection reliability and printing reliability, half etching is preferably performed so that the thickness of the conductive layer is in the range of 5 to 15 μm. Here, the reason why the copper foils of the conductive layers 50A and 50B are roughened in advance before the substitution-type electroless silver plating treatment is that the normal roughening chemical solution roughens the copper foil to which silver plating is attached. This is because even if the surface cannot be formed or roughened, the deposited silver plating is thin and the underlying copper is exposed. That is, by roughening the copper foil before the silver plating treatment, the silver plating can be attached along the shape of the copper foil, and the adhesion between the resistor 70 and the conductive layers 50A and 50B is sufficiently obtained. It can be secured.

  Subsequently, when the substrate 20 is subjected to substitutional electroless silver plating, a noble metal layer made of a thin silver plating film having a thickness of about 0.2 to 0.4 μm is formed along the shape of the conductive layers 50A and 50B in the opening 101. 60A and 60B are formed (FIG. 3F).

  Next, the plating resist 100 is peeled from the substrate 20 and the first wiring layers 40A and 40B (FIG. 4A).

  Subsequently, a resistor 70 made of carbon paste having a viscosity of 500 to 1000 poise is provided between the conductive layers 50A and 50B so as to partially overlap the noble metal layers 60A and 60B on the conductive layers 50A and 50B. Screen printing is performed using a metal mask made of metal and dried under predetermined conditions (FIG. 4B). After drying, the paste-like resistor 70 is cured under temperature conditions such that the maximum temperature reached 180 ° C. or higher. At this time, the thickness of the cured resistor 70 is set to about 20 μm.

  Here, the reason why the metal mask is used for the screen printing of the resistor 70 is that if the printing can be performed in a state where the surface of the substrate 20 is smooth and in close contact, there is durability and printing accuracy is excellent. Since the conductive layers 50A and 50B are half-etched, the surface of the substrate 20 is smooth enough to use a metal mask. On the other hand, normal printing with mesh-type screen plates such as Tetron or stainless steel has few restrictions on the printing surface, but by pressing the plate strongly with a squeegee with a gap of several millimeters between the screen plate and the substrate. Since the carbon paste is printed, the deformation of the opening due to the blotting or pushing of the carbon paste, the deterioration of the emulsion due to repeated printing, the distortion of the tetron or the stainless fiber, etc. are likely to occur. Therefore, a metal mask is used here.

Next, the insulating layer 30 is formed over the substrate 20 over which the resistor 70 is formed (FIG. 4C). The insulating layer 30 is obtained by laminating a commercially available insulating resin film for build-up multilayer printed wiring boards with a vacuum laminator, for example, under conditions of a temperature of 130 ° C. and a pressure of about 3 kg / cm ² , and the insulating resin is cured at 170 ° C. for about 1 hour. Form.

Subsequently, the insulating layer 30 is subjected to via processing with a CO ₂ laser to form via holes 81A and 81B (FIG. 4D). Then, electroless copper plating and electrolytic copper plating are performed to form connection layers 80A and 80B in the via holes 81A and 81B, and a second metal layer 91 is formed on the connection layers 80A and 80B and the insulating layer 30 (( 4E) At this time, the connection layers 80A and 80B are subjected to copper plating so as to electrically connect the first wiring layers 40A and 40B and the second metal layer 91 via the insulating layer 30. Yes.

  Next, the second metal layer 91 is selectively etched to form second wiring layers 90A and 90B on the insulating layer 30 (FIG. 4F). Thereby, the printed wiring board 10 incorporating the resistance element can be formed.

  As described above, according to the present embodiment, a pair of noble metal layers 60A and 60B formed so as to cover a part of each of the conductive layers 50A and 50B, and each noble metal layer 60A between the conductive layers 50A and 50B. , 60B, the noble metal layers 60A, 60B are printed on the substrate 20 between the conductive layers 50A, 50B as compared with the conventional structure shown in FIG. Therefore, it is possible to eliminate the decrease in printing accuracy due to the step while reducing the size of the resistance element. Further, since the conductive layers 50A and 50B are thinned in advance by half etching, it is possible to prevent a decrease in printing accuracy due to the unevenness of the wiring. Therefore, it is possible to provide a printed wiring board having a built-in resistor element that can reduce the size of the built-in resistor element and can prevent a decrease in reliability due to a step or unevenness.

  Further, since the noble metal layers 60A and 60B are printed wiring boards made of a silver plating film, they tend to exhibit cheap and stable characteristics as compared with other noble metals. Therefore, it is possible to provide a printed wiring board that incorporates a resistive element that is inexpensive and has excellent characteristic stability.

  Furthermore, since the surface of each conductive layer 50A, 50B is roughened, the adhesion of the resistor 70 is improved, and the contact resistance between the resistor 70 and the conductive layers 50A, 50B can be reduced.

  Further, since the plating thickness of the substitutional electroless noble metal plating is in the range of 0.2 μm or more and 0.4 μm or less, the contact resistance between the resistor 70 and the conductive layers 50A and 50B is reduced with the minimum necessary plating thickness. Processing time and cost can be reduced.

  Further, since the resistor 70 is made of a resistance material in which a conductive filler is dispersed in a thermosetting resin, it is possible to form a resistor that generally requires high-temperature firing even on an organic substrate with low heat resistance. .

  Further, since the surface roughness Ra of the resistance element electrodes (conductive layers 50A, 50B) subjected to the roughening treatment is set in the range of 1 μm or more and 2 μm or less, the roughened resistance element electrodes (conductive layers 50A, 50B). ) Even if the noble metal plating is deposited on the copper foil, the copper foil has a sufficient uneven shape, and the adhesion between the resistance element electrodes (conductive layers 50A and 50B) and the resistor 70 can be sufficiently secured.

  In addition, since the resistive element electrodes (conductive layers 50A and 50B) are half-etched in advance, when screen printing the resistor 70, the level difference can be reduced and the printing accuracy can be improved, and the conventional level difference portion can occur. It is possible to make it difficult to generate cracks that were easy.

  Further, the resistor 70 is formed by curing under a temperature condition such that the maximum temperature reaches 180 ° C. or more, and the resistor 70 is cured at a temperature higher than the curing temperature of a general multilayer printed wiring board insulating material. Therefore, the resistance value change of the resistance element 11 can be reduced before and after the insulating layer 30 is formed.

  Further, when forming the insulating layer 30 containing the resistance element 11, the maximum temperature reached in the pressing or laminating and curing process is lower than the maximum temperature achieved when the resistor 70 is cured, so the insulating layer 30 is formed. The resistance value change of the resistance element 11 can be reduced before and after.

  Further, since the resistor paste is screen-printed with a metal mask, the resistor 70 having excellent printing accuracy can be formed. In addition, the screen printing of the metal plate is more durable than the normal mesh plate, and is effective in reducing the cost.

  In the above embodiment, the case where the resist 100 is peeled off and the resistor 70 is printed after the noble metal layers 60A and 60B are formed has been described. However, the present invention is not limited thereto, and the resistor is formed after the noble metal layers 60A and 60B are formed. Even if it prints 70 and it manufactures in the order which peels the resist 100, this invention can be implemented similarly and the same effect can be acquired.

  Moreover, although the said embodiment demonstrated the case where the one buildup layer was formed on the board | substrate 20, not only this but the buildup layer was formed in both surfaces using the double-sided copper clad laminated board as the board | substrate 20. In addition, a printed wiring board having a structure in which two or more build-up layers are formed and the resistance element 11 is formed in an insulating layer that is not in direct contact with the substrate 20 is also included.

<Example>
EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited thereto.

  About the printed wiring board which incorporated the resistance element manufactured with the manufacturing method shown in an Example and a comparative example, (1) Resistance value measurement, (2) Comparison of resistance element occupation area, (3) High temperature, high humidity test, (4) Noble metal Insulation reliability test of plating or silver paste, (5) Thermal cycle test (TCT) was performed. The evaluation method is as follows.

◇ Evaluation method of example (1) <Measurement of resistance value>
The resistance value was measured with a multimeter for 100 printed wiring boards having a resistance element with a designed resistance value of 100Ω, and the average resistance value, standard deviation (σ), and 3σ values were obtained. This evaluated the reliability of the resistance element with respect to the dispersion | variation in resistance value.

(2) <Element occupation area comparison>
The occupation area of the resistance element in the printed wiring board in which the resistance element having a resistance value design value of 100Ω was incorporated was calculated. The resistance element is a portion composed of a resistor, a conductive layer, and a noble metal layer. Thereby, the size of the resistance element with respect to the manufacturing method was compared.

(3) <High temperature and high humidity test>
A printed wiring board with a built-in resistor was placed under conditions of a temperature of 40 ° C. and a humidity of 95% for 1000 hours. The resistance value before and after the test was measured to determine the change in resistance value. This evaluated the reliability of the resistance element with respect to the corrosion of the interface under high temperature and high humidity conditions.

(4) <Insulation reliability test>
Except for the process of printing and curing the resistor, 40 test boards manufactured under exactly the same conditions were prepared, and these test boards were put into a highly accelerated life test apparatus under conditions of a temperature of 121 ° C and a humidity of 85%. Then, a voltage of 20 V was applied for 168 hours, and the insulation resistance was measured over time. The test substrate was prepared by patterning 100 μm / 100 μm comb-shaped electrodes (conductive layers) on the same substrate used in the examples and the respective reference examples based on the JIS-C5012 standard. In Comparative Example 1, a comb electrode (conductive layer) of L / S = 100 μm / 100 μm was printed and formed with a silver paste. Then, the resistance value of 10 ⁶ Ω or less was judged as an insulation failure and evaluated. Thereby, the reliability of silver plating or silver paste was evaluated.

(5) <Thermal cycle test (TCT)>
For 100 printed wiring boards with a built-in resistance element whose resistance value is 100Ω, 1000 cycles TCT was performed under conditions of a low temperature bath of −40 ° C., a high temperature bath of 125 ° C. and an exposure time of 30 minutes, and the resistance value after the test An element with a current of 10 ⁶ Ω or more was evaluated as a defect due to a crack. This evaluated the reliability of the resistance element with respect to a temperature change.

◇ Production method of Example [Example 1]
First, after degreasing and washing a 0.6 mm BT resin double-sided copper-clad laminate (first metal layer) {Mitsubishi Gas Chemical Co., Ltd.} with a copper thickness of 18 μm, the etching resist is laminated, exposed and developed, and unnecessary parts The copper foil was etched to form a conductor circuit (first wiring layer) and a resistance element electrode (conductive layer). At this time, the design value of each resistive element electrode (conductive layer) in the resistor length direction was 200 μm. After plating resist RY-3225 {manufactured by Hitachi Chemical Co., Ltd.} was laminated on this substrate with a roll laminator, the resist was exposed and developed to open only the resistive element electrode portion.

  Further, this resistance element electrode was half-etched to a thickness of about 10 μm, and then subjected to a surface roughening treatment with Mec Etch Bond CZ-8101 (manufactured by Mec) under the condition that the surface roughness Ra was 1.2 μm. The surface roughness Ra was measured with a laser microscope. This substrate was treated with substitutional electroless silver plating IM-SILVER {manufactured by Nippon Kogyo Kagaku Co., Ltd.}, and the resistive element electrode (conductive layer) was coated with silver plating (noble metal layer) having a thickness of 0.3 μm.

  After the plating resist was peeled off, carbon paste TU-100-8 (resistor) {manufactured by Asahi Chemical Laboratory Co., Ltd.} was screen-printed using a 200 mesh stainless steel clean plate so as to overlap with the resistance element electrode by 200 μm. When the viscosity of the carbon paste (resistor) used for printing was measured with a Bisco Tester VT-04, it was around 700 poise. The design dimensions of the resistor sandwiched between the resistor element electrodes were 0.5 mm in width and 0.67 mm in length.

  The resistance paste (resistor) printed in this manner was dried at 90 ° C. for 30 minutes and then cured at 200 ° C. for 1 hour. When the thickness of the cured resistor was measured, the thickness was about 20 μm.

On this board | substrate, copper foil ARCC R-0870 with resin (2nd metal layer with an insulating layer) {made by Matsushita Electric Works Co., Ltd.} was laminated for 1 hour at a pressure of 30 kgf / cm ² and a temperature of 170 ° C. with a vacuum press. Further, the copper foil in the via forming portion was etched, and via processing was performed with a CO ₂ laser. Thereafter, a connection layer for electrically connecting vias is formed by electroless copper plating and electrolytic copper plating, a predetermined conductor pattern (second wiring layer) is formed by etching, and a resistance element is built in the insulating layer. A printed wiring board was manufactured.

[Comparative Example 1]
It is a comparative example with Example 1, and is an example which manufactured the printed wiring board which incorporated the resistive element with the conventional manufacturing method. That is, the conductive layer is formed of silver paste, not a thin film formed by noble metal plating.

  First, the same double-sided copper-clad laminate (first metal layer) as in Example 1 {Mitsubishi Gas Chemical Co., Ltd.} is used in the same manner as in Example 1 to conduct a conductor circuit (first wiring layer) and a resistance element electrode (conductive layer). Formed. At this time, the design value of each resistive element electrode in the resistor length direction was 200 μm. Next, a conductive silver paste LS-504J (manufactured by Asahi Chemical Laboratory Co., Ltd.) is formed on a pair of resistance element electrodes 200 μm and 400 μm on the substrate resin inside the resistance element electrodes, for a total of 600 μm, 325 mesh stainless screen Screen printed on plate. When the film thickness of the cured silver paste was measured after drying and curing, the film thickness was about 15 μm.

  Carbon paste TU-100-8 (resistor) {manufactured by Asahi Chemical Laboratory Co., Ltd.} was screen-printed with a 200-mesh stainless steel clean plate so as to overlap the innermost 200 μm portion of the cured silver paste. The viscosity of the carbon paste (resistor) was about 700 poise as measured with a Bisco Tester VT-04. Moreover, the design dimensions of the resistor sandwiched between the cured silver pastes were a width of 1.0 mm and a length of 1.34 mm. The substrate on which the resistor was printed in this way was dried at 90 ° C. for 30 minutes and then cured at 200 ° C. for 1 hour. The film thickness of the cured resistor was about 20 μm. This board | substrate was processed by the MEC etch bond CZ-8101 (made by a MEC company), and the copper foil of the resistance element electrode (conductive layer) was roughened.

After that, an insulating resin film ABF-GX {manufactured by Ajinomoto Fine Techno Co., Ltd.} for build-up multilayer printed wiring board is laminated on this substrate at a temperature of 130 ° C. and a pressure of 3 kg using a vacuum laminator, and then cured at 170 ° C. for 1 hour. An insulating layer was formed. After via processing with a CO ₂ laser, roughening treatment with alkaline permanganate, electroless copper plating, and electrolytic copper plating were performed, and a second metal layer was formed together with a connection layer for electrically connecting the via. . Thereafter, a predetermined conductor pattern (second wiring layer) was formed by etching, and a printed wiring board in which a resistance element was built in the insulating layer was manufactured.

[Reference Example 1]
It is a reference example of Example 1, and is an example in which a printed wiring board having a built-in resistance element is manufactured by changing the order of the manufacturing process. That is, the resist is not printed after the resist is peeled, but the resist is peeled after the resistor is printed.

  First, the same double-sided copper-clad laminate (first metal layer) as in Example 1 {Mitsubishi Gas Chemical Co., Ltd.} is used in the same manner as in Example 1 to conduct a conductor circuit (first wiring layer) and a resistance element electrode (conductive layer). Formed. At this time, the design value of each resistive element electrode (conductive layer) in the resistor length direction was 100 μm. After plating resist RY-3225 (manufactured by Hitachi Chemical Co., Ltd.) was laminated on this substrate with a roll laminator, the resist was exposed and developed to open the same region as the resistor forming region. Further, after half-etching a pair of resistance element electrodes (conductive layers) in the opening to a thickness of about 10 μm, the resistance element electrodes (conductive layers) are roughened with Mec Etch Bond CZ-8101 (MEC). The surface was roughened under the condition that Ra was 1.2 μm. This substrate was treated with substitutional electroless silver plating IM-SILVER {manufactured by Nippon Kogyo Kagaku Co., Ltd.}, and the resistance element electrode was coated with silver plating (noble metal layer) having a thickness of 0.3 μm.

  In this way, carbon paste TU-100-8 (resistor) {manufactured by Asahi Chemical Laboratory Co., Ltd.} and the resistance element electrode and 100 μm are formed in the opening of the plating resist having a pair of resistance element electrodes coated with silver plating. Screen printing was performed using a metal mask so as to overlap each other. When the viscosity of the carbon paste (resistor) used for printing was measured with a Bisco Tester VT-04, it was around 700 poise. The design dimensions of the resistor sandwiched between the resistive element electrodes (conductive layers) were 0.5 mm in width and 0.67 mm in length.

  After the substrate on which the resistor was printed in this manner was dried at 90 ° C. for 30 minutes, the plating resist was peeled off and the resistor paste (resistor) was cured at 200 ° C. for 1 hour. When the thickness of the cured resistor was measured, it was about 20 μm.

An insulating resin film ABF-GX {manufactured by Ajinomoto Fine-Techno Co., Ltd.} for build-up multilayer printed wiring board is laminated on this substrate with a vacuum laminator at a temperature of 130 ° C. and a pressure of 3 kg, and then cured at 170 ° C. for 1 hour to form an insulating layer Formed. After via processing with a CO ₂ laser, roughening treatment with alkaline permanganate, electroless copper plating, and electrolytic copper plating were performed, and a second metal layer was formed together with a connection layer for electrically connecting the via. . Thereafter, a predetermined conductor pattern (second wiring layer) was formed by etching, and a printed wiring board in which a resistance element was built in the insulating layer was manufactured.

[Comparative Example 2]
It is a comparative example with Example 1, and is the example which manufactured the printed wiring board which incorporated the resistive element, without carrying out half etching of the conductive layer.

  First, the same double-sided copper-clad laminate (first metal layer) as in Example 1 {Mitsubishi Gas Chemical Co., Ltd.} is used in the same manner as in Example 1 to conduct a conductor circuit (first wiring layer) and a resistance element electrode (conductive layer). Formed. At this time, the design value of each resistive element electrode (conductive layer) in the resistor length direction was 200 μm. After plating resist is laminated, exposed, and developed on this substrate, only the resistance element electrode (conductive layer) portion is opened, and then processed with Mec Etch Bond CZ-8101 (Mec Co., Ltd.) to roughen the copper foil. It was. Furthermore, this resistance element electrode (conductive layer) was subjected to electroless silver plating with IM-SILVER {manufactured by Nippon Kogyo Kagaku Co., Ltd.} to form a silver plating film (noble metal layer) having a thickness of 0.3 μm.

  After stripping the plating resist, carbon paste TU-100-8 (resistor) {manufactured by Asahi Chemical Laboratory Co., Ltd.} is overlapped with the resistive element electrode by 200 μm on the resistive element electrode (conductive layer) coated with silver plating. Were screen printed with a 200 mesh stainless steel screen plate. When the viscosity of the carbon paste (resistor) used for printing was measured with Piscotester VT-04, it was around 700 poise. The design dimensions of the resistor sandwiched between the resistive element electrodes (conductive layers) were 1.0 mm in width and 1.34 mm in length.

  Thus, after the board | substrate with which the resistor was printed was dried at 90 degreeC for 30 minutes, it was hardened at 200 degreeC for 1 hour. When the thickness of the cured resistor was measured, the thickness was about 20 μm. An insulating layer, a conductor circuit, and the like were formed on this substrate in the same manner as the manufacturing method of Example 1, and a printed wiring board in which a resistance element was built in the insulating layer was manufactured.

[Example 2]
This is an example in which a printed wiring board with a built-in resistance element was manufactured without roughening the conductive layer with respect to Example 1.

    First, the same double-sided copper-clad laminate (first metal layer) as in Example 1 {Mitsubishi Gas Chemical Co., Ltd.} is used in the same manner as in Example 1 to conduct a conductor circuit (first wiring layer) and a resistance element electrode (conductive layer). Formed. At this time, the design value of each resistive element electrode (conductive layer) in the resistor length direction was 200 μm. After plating resist was laminated, exposed and developed on this substrate to open only the resistive element electrode (conductive layer) portion, this resistive element electrode (conductive layer) was half-etched to a thickness of about 10 μm. Thereafter, an electroless silver plating treatment was performed using IM-SILVER {manufactured by Nippon Kogyo Kagaku Co., Ltd.} to form a silver plating film (noble metal layer) having a thickness of 0.3 μm.

  After the plating resist is peeled off, carbon paste TU-100-8 (resistor) {manufactured by Asahi Chemical Laboratory Co., Ltd.} is overlapped with the resistive element electrode by 200 μm on the resistive element electrode (conductive layer) coated with silver plating. Screen printed with a 200 mesh stainless screen. When the viscosity of the carbon paste (resistor) used for printing was measured with Piscotester VT-04, it was around 700 poise. The design dimensions of the resistor sandwiched between the resistive element electrodes (conductive layers) were 1.0 mm in width and 1.34 mm in length.

  Thus, after the board | substrate with which the resistor was printed was dried at 90 degreeC for 30 minutes, it was hardened at 200 degreeC for 1 hour. When the thickness of the cured resistor was measured, the thickness was about 20 μm. After this substrate was treated with Mec Etch Bond CZ-8101 (made by Mec Co., Ltd.) to roughen the copper foil, an insulating layer, a conductor circuit, and the like were formed by the same method as the production method of Example 1 to insulate. A printed wiring board with a resistive element built in the layer was manufactured.

[Example 3]
This is an example in which a printed wiring board having a built-in resistance element is manufactured when the roughening treatment of the conductive layer is made insufficient with respect to Example 1.

  First, the same double-sided copper-clad laminate (first metal layer) as in Example 1 {Mitsubishi Gas Chemical Co., Ltd.} is used in the same manner as in Example 1 to conduct a conductor circuit (first wiring layer) and a resistance element electrode (conductive layer) Formed. At this time, the design value of each resistive element electrode (conductive layer) in the resistor length direction was 200 μm. After plating resist RY-3225 {manufactured by Hitachi Chemical Co., Ltd.} was laminated on this substrate with a roll laminator, the resist was exposed and developed to open only the resistance element electrode (conductive layer) portion. Further, this resistance element electrode (conductive layer) was half-etched to a thickness of about 10 μm, and then roughened with Mec Etch Bond CZ-8101 (manufactured by Mec) under the condition of Ra = 0.5 μm. . This substrate was treated with substitution-type electroless silver plating IM-SILVER {manufactured by Nippon Kogyo Kagaku Co., Ltd.}, and the resistance element electrode (conductive layer) was coated with silver plating (noble metal layer) having a thickness of 0.3 μm. After the plating resist was peeled off, carbon paste TU-100-8 (resistor) {manufactured by Asahi Chemical Laboratory Co., Ltd.} was screen-printed using a 200 mesh stainless steel clean plate so as to overlap with the resistance element electrode by 200 μm. When the viscosity of the carbon paste (resistor) used for printing was measured with a Bisco Tester VT-04, it was around 700 poise. The design dimensions of the resistor sandwiched between the resistive element electrodes (conductive layers) were 0.5 mm in width and 0.67 mm in length.

  The resistance paste (resistor) printed in this manner was dried at 90 ° C. for 30 minutes and then cured at 200 ° C. for 1 hour. When the thickness of the cured resistor was measured, the thickness was about 20 μm. After this substrate is treated with Mec Etch Bond CZ-8101 {made by Mec Co., Ltd.} to roughen the copper foil, an insulating layer, a conductor circuit and the like are formed by the same method as the production method of Example 1, A printed wiring board having a resistance element built in the insulating layer was manufactured.

<Measurement Result of Example> As shown in FIG. 5, the measurement result of Example 1 shows extremely good measurement values as compared with Comparative Example 1.

  Specifically, the average resistance value of Example 1 at a design value of 100Ω is 97.2Ω, and Comparative Example 1 is 78Ω. In addition, the value of the standard deviation σ of Example 1 is 5.4, and Comparative Example 1 is 14.54. Moreover, the value of 3σ of Example 1 is 16.2, and Comparative Example 1 is 43.62.

  As a result, it was confirmed that Example 1 was able to print the resistor with higher accuracy than Comparative Example 1, and prevented a decrease in reliability (printing accuracy) due to steps and irregularities.

The value of the element occupation area of Example 1 is 2.436 mm ² , and Comparative Example 1 is 4.572 mm ² . As a result, it was confirmed that Example 1 can print with higher accuracy than Comparative Example 1 even if the size of the resistor is reduced.

  The change in the resistance value of Example 1 with respect to the high-temperature and high-humidity test is 2.1%, and Comparative Example 1 is 2.1%. Thereby, it was confirmed that Example 1 can prevent an increase in resistance value due to corrosion of the interface under the high temperature and high humidity condition, as in Comparative Example 1.

  In the number of samples of 40, the number of failures with respect to the insulation reliability test of Example 1 is 0, and that of Comparative Example 1 is 29. Thereby, unlike the comparative example 1, it has confirmed that Example 1 can prevent deterioration by a lifetime.

  The number of defects with respect to the TCT test of Example 1 in 100 samples is 0, and that in Comparative Example 1 is 26. Thereby, unlike Comparative Example 1, it was confirmed that Example 1 can suppress cracks due to temperature changes.

  As described above, according to the present invention, compared to a conventional printed wiring board incorporating a resistive element, the size of the resistive element can be reduced and the reliability of the printed wiring can be prevented from being deteriorated due to steps or irregularities. A board and a method for manufacturing the same could be provided.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine a component suitably in different embodiment.

It is sectional drawing which shows an example of the structure of the printed wiring board which concerns on one Embodiment of this invention. It is a top view which shows notionally an example of the structure of the printed wiring board concerning the embodiment. It is process sectional drawing which shows the manufacturing method of the printed wiring board which concerns on the same embodiment. It is process sectional drawing which shows the manufacturing method of the printed wiring board which concerns on the same embodiment. It is a figure which shows the result of the Example and comparative example of a printed wiring board which concern on the embodiment. It is sectional drawing which shows the structure of the conventional printed wiring board. It is sectional drawing which shows the structure of the conventional printed wiring board.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Printed wiring board, 11 ... Resistance element, 20 ... Board | substrate, 30 ... Insulating layer, 40A, 40B ... 1st wiring layer, 41 ... 1st metal layer, 50A, 50B ... conductive layer, 60A, 60B ... noble metal layer, 70 ... resistor, 80A, 80B ... connection layer, 81A, 81B ... via hole, 90A, 90B ... second wiring layer 91 ... 2nd metal layer, 100 ... Plating resist, 101 ... Opening part.

Claims (6)

A substrate,
A pair of wiring layers selectively formed on the substrate;
A pair of conductive layers formed by half-etching a part of each wiring layer;
A pair of noble metal layers plated to cover each conductive layer;
A printed wiring board comprising: a resistor formed by selectively printing on each noble metal layer and a substrate between the conductive layers so as to electrically connect the conductive layers. In the printed wiring board of Claim 1,
Each said noble metal layer consists of a silver plating film, The printed wiring board characterized by the above-mentioned. In the printed wiring board according to claim 1 or 2,
A printed wiring board, wherein the surface of each conductive layer is roughened. Selectively forming a pair of wiring layers on a substrate;
Selectively forming a resist layer on the substrate having a first opening exposing a part of each wiring layer and covering each wiring layer;
Half-etching each wiring layer in the first opening to form a pair of conductive layers;
Forming a pair of noble metal layers on a portion of each of the half-etched conductive layers;
Removing the resist layer after forming the noble metal layer;
And a step of forming a resistor on the substrate between the conductive layers and on the noble metal layer. In the manufacturing method of the printed wiring board of Claim 4,
The step of forming each noble metal layer includes a step of forming a silver plating film as each noble metal layer by a silver plating process. In the manufacturing method of the printed wiring board of Claim 4 or Claim 5,
A method of manufacturing a printed wiring board, further comprising a step of roughening each half-etched conductive layer between the half-etching step and the noble metal layer forming step.

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