JP3495203B2 - Circuit board manufacturing method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides an overcoat glass layer on the surface of a surface wiring conductor with high precision, and can suppress the phenomenon of peeling between laminated dielectric layers. The present invention relates to a method for manufacturing a circuit board having a small laminated structure. 2. Description of the Related Art In a circuit board having a laminated structure, an internal wiring conductor including a via-hole conductor is provided in a laminate formed by laminating a plurality of dielectric layers, and a surface wiring conductor is formed on the surface of the laminate. Further, an overcoat glass layer is formed except for a predetermined position of the surface wiring conductor, for example, a portion on which various electronic components are mounted and a terminal electrode portion for making an electrical connection to the outside. A method of manufacturing a circuit board having such a structure is as follows.
A green sheet multilayer method serving as a dielectric layer is mainly used, and a large green sheet having a plurality of circuit board regions is used in consideration of productivity. [0004] For example, a through-hole serving as a via-hole conductor is formed in each circuit board region of a first green sheet serving as a dielectric layer located on the surface of the laminate, and the through-hole is printed and filled with a conductive paste. On this green sheet,
A conductor film to be a surface wiring conductor is formed by printing. Further, a through hole serving as a via hole conductor is formed in each circuit board region of a second green sheet serving as a dielectric layer other than the surface dielectric layer of the laminate, and a conductive paste is printed and filled in the through hole. At the same time, a conductor film serving as an internal wiring conductor is printed on the green sheet. Thereafter, the first and second green sheets are sequentially laminated. Thereby, a large-sized laminate in an unfired state is achieved. Next, division grooves for partitioning the unsintered large-sized laminate for each circuit board region are formed by press molding or the like. Next, the large-sized circuit laminate in the unfired state is subjected to a baking treatment to form a large-sized laminate in which each circuit board region is partitioned by the dividing grooves. Next, for each circuit board region of the large laminate,
An overcoat glass layer covering a predetermined position of the surface wiring conductor is formed by printing and baking a glass paste to form a large circuit board. Finally, a dividing process is performed along the dividing groove,
Multiple individual circuit boards were extracted from a large circuit board. However, recently, by using a glass-ceramic material which can be fired at a relatively low temperature of 800 to 1050 ° C. as a material constituting the dielectric layer, the internal wiring conductor and the surface wiring conductor can be formed. Au, A for material
g, Cu and other materials can be used, and even the overcoat glass layer that protects the surface wiring conductors,
It can be fired integrally. Thus, the overcoat glass layer is not formed on the surface of the fired large-sized laminate in a sintering-shrinked state, but is formed on a large-sized unfired large-sized laminate in which the positional relationship with the surface wiring conductor can be easily defined. In the state of the laminate, the overcoat glass layer is formed, and can be simultaneously fired together with the large laminate and the surface wiring conductor. However, as in the above-described manufacturing method, an overcoat glass layer is formed on the surface of an unfired large circuit board before the size of the laminate is changed due to shrinkage during firing. Even if it can be formed, the peeling phenomenon between the dielectric layers constituting the laminated body will occur in reverse. That is, since the overcoat glass layer is formed only at a predetermined position of the surface wiring in each circuit board region of the large unfired large-sized laminate, it is generally not formed at the portion where the dividing groove is formed. It is. For this reason, by the pressure treatment at the time of the lamination processing,
In the unsintered large-sized laminated circuit board, the adhesive strength between the green sheets of the laminate differs between the portion where the layer to be the overcoat glass layer is formed and the portion where the layer is not formed, resulting in overcoating. A peeling phenomenon occurs between the dielectric layers of the portion of the laminate where the layer serving as the glass layer is not formed. Further, regarding the relationship between the end of the overcoat glass layer and the end of the surface wiring conductor, it is necessary to form the overcoat glass layer at a certain interval from the end of the surface wiring conductor. In addition, since a predetermined interval is provided between the overcoat glass layer and the dividing groove, there is a problem that the circuit board becomes larger than the actual pattern of the surface wiring conductor. The present invention has been devised in view of the above-mentioned problems, and has as its object to form an overcoat glass layer on a surface wiring conductor with high precision, and to further improve the dielectric properties of the laminated body. An object of the present invention is to provide a method for manufacturing a small circuit board, which can prevent a peeling phenomenon between body layers. A method of manufacturing a circuit board according to the present invention comprises the steps of: forming one first green sheet having a plurality of circuit board areas and at least one second green sheet; Forming a conductive film to be a surface wiring conductor on each circuit board area on the surface of the first green sheet, and excluding a predetermined portion exposing the surface wiring conductor, A step of continuously forming a film to be an overcoat glass layer that covers a part of the conductor film over substantially the entire circuit board region over substantially the entire surface; Forming a conductor film serving as an internal wiring conductor, and laminating a first green sheet on the second green sheet to form a large laminated body. Thereafter, each circuit board is formed on the large laminated body. Forming a dividing groove for partitioning a region, and baking the large-sized laminate to form a large-sized circuit board including a plurality of circuit boards having an internal wiring conductor, a surface wiring conductor, and an overcoat glass layer; Dividing the large circuit board along the dividing groove and separating the circuit board into individual circuit boards. According to the manufacturing method of the present invention, the film to be the overcoat glass layer is formed following the formation with the surface wiring conductor on the first green sheet before the laminating step of forming the large-sized laminate. You. That is, since the film to be the overcoat glass layer is formed without being affected by the fluctuation of the surface dimensions due to the laminating pressure treatment or the fluctuation of the surface dimensions due to the shrinkage behavior generated during firing, the film for the surface wiring conductor is formed. On the other hand, a highly accurate overcoat glass layer can be formed. Further, in the state where the division groove is not formed, the first green sheet is continuously formed on substantially the entire surface of the large-sized laminated body except for a predetermined portion exposing the surface wiring conductor. That is, even if a pressure step such as lamination pressure is performed,
Since a substantially uniform lamination density is obtained over substantially the entire surface of the large-sized laminated body, a peeling phenomenon between dielectric layers due to a difference in lamination densities in the firing step can be suppressed. At the same time, since the overcoat glass layer can be formed ignoring the distance between the overcoat glass layer and the dividing groove, the outer peripheral portion of the circuit board can be formed only by the forming position of the dividing groove and the end of the surface wiring conductor. Is determined, the circuit board can be reduced in size. Hereinafter, a method of manufacturing a circuit board according to the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a circuit board according to the present invention. In FIG. 1, reference numeral 10 denotes a circuit board. The circuit board 10 exposes a laminate 1 serving as a base, a surface wiring conductor 2 formed on the surface of the laminate, and predetermined positions of the surface wiring conductor 2. Overcoat glass layer 5 formed on
It is composed of The laminated body 1 has an internal wiring conductor 3 and a via-hole conductor 4 therein. The via-hole conductor 4 is included in the inner wiring conductor 3 in a broad sense. Reference numeral 6 denotes an electronic component 6 connected to the surface wiring conductor 2. The laminated body 1 includes dielectric layers 1a to 1e made of a glass-ceramic material and internal wirings for achieving a predetermined circuit network and generating a capacitance component between the dielectric layers 1a to 1e. The conductor 3 is arranged. In the dielectric layers 1a to 1e, via-hole conductors 4 penetrating the thickness direction of the layers are formed. The dielectric layers 1a to 1e are, for example, 850 to 1
It is made of a glass-ceramic material that can be fired at a relatively low temperature of around 050 ° C. Specific examples of the ceramic material include cristobalite, quartz, corundum (α-alumina), mullite, and cordierite. Further, by firing a glass frit containing a plurality of metal oxides as a glass material, cordierite,
It precipitates at least one kind of crystal of mullite, anorthite, serdian, spinel, garnite, willemite, dolomite, petalite or a substituted derivative thereof. The thickness of the dielectric layers 1a to 1e is, for example, 100
About 300 μm. The internal wiring conductor film 3 and the via hole conductor 4
It is made of a conductor film (conductor) such as Ag-based (Ag alone, Ag alloy such as Ag-Pd), and the thickness of the internal wiring conductor film 3 is 8 to
The diameter of the via hole conductor 4 can be set to an arbitrary value. For example, the diameter is 80 to 250 μm.
m. The surface wiring conductor film 2 is formed on the surface of the laminate 1. The surface wiring conductor film 2 is made of an Ag-based material (Ag alone, an Ag alloy such as Ag-Pd) or an Au-based material (A
u, an Au alloy such as Au-Pd and Au-Pt). The surface wiring conductor film 2 mainly constitutes a circuit wiring on the surface, serves as a connection pad for the electronic component 6 to be joined via solder, and serves as a thick film resistance film and a thick film capacitor element. It becomes a terminal electrode. In particular, it is connected to the via-hole conductor 4 exposed from the dielectric layer 1a. An overcoat glass layer 5 is formed on the entire surface of the laminate 1 so as to expose the above-mentioned connection pads and terminal electrodes of the surface wiring conductor 3. The overcoat glass layer 5 is made of a low-melting glass material co-fired at about 800 to 1050 ° C., preferably, the dielectric layers 1 a to 1
It is made of a glass material whose main component is the glass material used for e. Such a circuit board is formed by a green sheet multilayer method using large green sheets of a glass-ceramic material in consideration of productivity. First, in the method of manufacturing the circuit board 1,
A large first green sheet that becomes the dielectric layer 1a of the laminate 1 and a large second green sheet that becomes the dielectric layers 1b to 1e of the laminate 1, which are (a) to (d) in the process diagram of FIG. For example, an Ag-based conductive paste for forming the internal wiring conductor 3 and the via-hole conductor 4, an Au-based, Ag-based conductive paste for forming the surface wiring conductor 2, and an overcoat glass layer 5 are formed. Prepare a glass paste to perform. The first and second green sheets have a plurality of circuit board regions so that a plurality of circuit boards can be extracted, and are made of a glass-ceramic material. For example, ceramic powder, frit of low melting glass component,
A slurry obtained by uniformly kneading an organic binder and an organic solvent is tape-formed to a predetermined thickness by a doctor blade method, and cut into a predetermined size to form a sheet. The ceramic powder includes insulating ceramic materials such as cristobalite, quartz, corundum (α-alumina), mullite, cordierite, BaTiO ₃ , Pb ₄ F
e ₂ Nb ₂ O _12, the dielectric ceramic material, such as TiO _2, Ni-Zn ferrite, (referred to ceramic in a broad sense) Mn-Zn ferrite Do to as magnetic ceramic material can be mentioned, its average particle size 1 0.0-6.0μ
m, preferably 1.5 to 4.0 μm. Incidentally, two or more ceramic materials may be used in combination. In particular, the use of corundum is advantageous in terms of cost. The frit of the low-melting glass component precipitates a crystal phase of cordierite, mullite, anorthite, serdian, spinel, garnite, willemite, dolomite, petalite or a substituted derivative thereof or a crystal phase having a spinel structure by firing. Any material may be used, for example, glass frit containing B ₂ O ₃ , SiO ₂ , Al ₂ O ₃ , ZnO, and alkaline earth oxide. The composition ratio of the above-mentioned ceramic material and glass material is such that the ceramic material is 10 to 60 wt%, preferably 30 to 50 wt% in order to fire at a relatively low temperature of 850 to 1050 ° C. 90-40w
t%, preferably 70 to 50 wt%. It is necessary to give importance to the wettability of the organic binder with a solid content (ceramic powder, frit of a low-melting glass component), and the organic binder is thermally decomposable so that it can be burned off in a relatively low-temperature and short-time firing step. Excellent ones are preferable, and ethylenically unsaturated compounds having a carboxyl group and an alcoholic hydroxyl group such as acrylic acid or methacrylic acid-based polymers are preferable. As the solvent, an organic solvent or an aqueous solvent can be used. For example, in the case of an organic solvent, 2.
For example, 2.4-trimethyl-1.3-pentadiol monoisoventilate is used. In the case of an aqueous solvent, it must be water-soluble, and the monomer and the binder include a hydrophilic functional group such as carboxyl. A group has been added. The amount of addition is 2 to 300, preferably 5 to 100 in terms of acid value. If the added amount is small, the solubility in water and the dispersibility of the powder of the fixed component become poor,
If the amount is large, the thermal decomposability deteriorates. Therefore, the addition amount is appropriately added in the above range in consideration of solubility in water, dispersibility, and thermal decomposability. Next, as shown in FIG. 2E, a through hole serving as a via hole conductor 4 is punched in each circuit board region of the first and second green sheets serving as the dielectric layers 1a to 1e by punching. Form. At the same time, as shown in steps (f) and (g) in FIG. 2, a conductor to be a via-hole conductor 4 is formed in the through-hole by printing and filling with an Ag-based conductive paste. As described above, on the second green sheet to be the dielectric layers 1b to 1e, a conductor film to be the internal wiring conductor 3 is formed by printing and drying an Ag-based conductive paste. Further, as in the step (f), a conductive film to be the surface wiring conductor 2 is formed on the first green sheet to be the dielectric layer 1a by printing and drying an Ag-based conductive paste. On the first green sheet, as in the step (h),
A film to be the overcoat glass layer 5 is formed by printing and drying a glass paste. FIG. 3 shows the first green sheet after the completion of this step. In FIG. 3, 10a is a first green sheet, 21 is a conductor film to be the surface wiring conductor 2, 41 is a conductor to be the via hole conductor 4, and 51 is a film to be the overcoat glass layer 5. The film to be the overcoat glass layer 5 is formed on substantially the entire surface of the first green sheet except for a predetermined position of the conductor film to be the surface wiring conductor 2, for example, a portion to be a pad for mounting the electronic component 6 and an output terminal. Formed across. Here, the Ag-based conductive paste of the via-hole conductor 4 and the internal wiring conductor film 3 is made of an Ag-based paste (Ag alone, A
Ag alloys such as g-Pd) powder, borosilicate low melting point glass frit, organic binders such as ethyl cellulose,
What mixed the solvent homogeneously is used. The Ag-based conductive paste of the surface wiring conductor 2 is a homogeneous mixture of Ag-based (Ag alone, Ag alloy such as Ag-Pd) powder, Pt powder, low melting glass frit, organic binder, and solvent. Is used. In order to approximate the sintering behavior of the green sheet, the glass paste of the overcoat glass layer 5 is mainly composed of the frit of the low melting point glass component used for the material of the green sheet, for example, B ₂ O ₃ , SiO ₂ ,
A homogeneous mixture of Al ₂ O ₃ , ZnO, glass frit of alkaline earth oxide, organic binder, and solvent is used. Next, as in the step (i) in FIG.
Dielectric layers 1b to 1e each having a conductor serving as via-hole conductor 4 and a conductor film serving as internal wiring conductor 3 formed in each circuit board region.
A second green sheet, a conductor film serving as the surface wiring conductor 2, and a first green sheet serving as the dielectric layer 1a on which the film serving as the overcoat glass layer 5 is formed. A large-sized laminate is formed by pressure bonding at a pressure of ³ cm ³ . FIG. 4 shows a state in which this step has been completed. In FIG. 4, reference numerals 10b to 10e denote second green sheets formed of dielectric layers 1b to 1e, and first green sheets 10a.
And a large laminated body 100 in an unfired state as a whole.
To form Reference numeral 31 denotes a conductor film to be the internal wiring conductor 3. In FIG. 3, dotted lines indicated by X indicate boundaries between circuit board regions, and division grooves will be formed in the next step. Next, as shown in step (j) of FIG.
Specifically, a film to be the overcoat glass layer 5 and a part of the laminated green sheet are formed on the large-sized laminate in an unfired state so as to partition each circuit board region. Next, as shown in step (k) in FIG.
The unsintered large-sized laminate, the conductor film serving as the surface wiring conductor 2, and the film serving as the overcoat glass layer 5 are simultaneously fired in an oxidizing atmosphere or an air atmosphere. This firing step includes a binder removal step and a sintering step. The binder removal process includes the following steps: a green sheet serving as the dielectric layers 1a to 1e, a conductor film serving as the internal wiring conductor 3, a conductor serving as the via hole conductor 4, a conductor film serving as the surface wiring conductor 2, and an overcoat glass layer 5. To burn off organic components contained in the film, for example, 500 to 6
It is performed in a temperature range of 00 ° C. In the sintering process, the glass component of the glass-ceramic green sheet is crystallized and simultaneously dispersed uniformly at the grain boundaries of the ceramic powder to give a certain strength to the laminated body, thereby forming the internal wiring conductor 3. The conductive film, the conductor to be the via hole conductor 4, and the metal powder and the Ag powder of the conductive material of the conductive film to be the surface wiring conductor 2 are grain-grown to lower the resistance, and the film to be the overcoat glass layer 5 is crystallized. In this case, they are integrated with the dielectric layers 1a to 1e. This is done until a peak temperature of 850-1050 <0> C is reached. At this point, at a temperature (for example, 550 ° C.) lower than the temperature (about 600 ° C.) at which the glass-ceramic material starts a sintering reaction (sintering shrinkage), the metal powder of the conductive material (sintering shrinkage) Will start. As a result, a large circuit board is obtained in which the internal wiring conductors 3 and the via hole conductors 4 are formed inside each circuit board area, and the surface wiring conductor film 2 and the overcoat glass layer 5 are formed on the surface. Will be. Next, the thick film resistance element connected to the surface wiring conductor 2 and various electronic components 6 are joined and mounted with solder or the like. Finally, as shown in FIG. 2 (l), a dividing process is performed along the dividing grooves for dividing each circuit board. Thereby, a plurality of circuit boards 10 shown in FIG. 1 are extracted from the large circuit board. As described above, in the manufacturing method of the present invention, the film 51 to be the overcoat glass layer 5 is formed before the first green sheet 10a and the second green sheets 10b to 10e are laminated. Therefore, laminating pressure during laminating (step (i))
Therefore, even if the planar shape of the green sheet 10a and the planar shape of the large laminate 100 are slightly deformed, the deformation has no relation to the print formation of the overcoat glass layer 5, so that the predetermined shape on the surface wiring conductor 2 is not affected. The overcoat glass layer 5 can be formed accurately at the position. Further, since the film 51 to be the overcoat glass layer 5 is formed over substantially the entire surface of the first green sheet 10a over the area of each circuit board, the above-described surface pressing and laminating are performed. Also at the time of the pressurizing process, the conductor film 21 which becomes the surface wiring conductor 2, the conductor film 31 which becomes the internal wiring conductor film 3,
Since the lamination density of the portion where the film 51 to be the overcoat glass layer 5 is formed and the portion where only the film to be the overcoat glass layer 5 is formed can be approximated, the baking treatment is performed. The sintering behavior at the time is similar between the two portions, and the delamination phenomenon of the dielectric layer at the portion where the overcoat glass layer 5 has not been formed can be effectively suppressed as in the related art. Further, since the overcoat glass layer 5 can be formed ignoring the formation positions of the division grooves, the relationship between the surface wiring conductor 2 and the overcoat glass layer 5, the overcoat glass layer 5 and the The relationship with the position where the dividing groove is formed can be ignored. Thereby, the surface wiring conductor 2
Only the relationship between the circuit board and the dividing groove needs to be considered.
Can be reduced in size. EXPERIMENTAL EXAMPLE The inventor of the present invention formed the overcoat glass layer 5 over the region where the dividing groove was formed,
The occurrence rate of the delamination phenomenon between the conventional product in which the overcoat glass layer 5 was not formed in the region where the dividing groove was formed was examined. The thickness of the film to be the overcoat glass layer 5 was about 30 μm, and the distance between the end of the overcoat glass layer 5 and the dividing groove was 0.3 mm in the conventional product. As a result, no delamination occurred at the end of the circuit board 1 in the product of the present invention with respect to the number of samples and 100 samples. There has occurred. As described above, according to the present invention, in a large circuit board from which a plurality of circuit boards can be extracted, a conductor film to be a surface wiring conductor, an overcoat, Because a film to be a glass layer was formed,
Even if the green sheet is deformed by the subsequent pressing step, the accuracy of the positional relationship with the surface wiring conductor is maintained. That is, the overcoat glass layer can be formed accurately and easily. Further, since an overcoat glass layer was formed also at a portion where a dividing groove for extracting a plurality of circuit boards from a large circuit board was formed, delamination around the dividing groove due to a difference in sintering behavior in the firing process. The phenomenon can be effectively suppressed. Further, since there is no space between the conventional overcoat glass layer and the dividing groove, the size of the circuit board can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a circuit board according to the present invention. FIG. 2 is a process chart for explaining a circuit board manufacturing method of the present invention. FIG. 3 is a partial cross-sectional view of a first green sheet for describing a method of manufacturing a circuit board according to the present invention. FIG. 4 is a partial cross-sectional view of a large-sized laminated body for describing a method of manufacturing a circuit board according to the present invention. [Description of Signs] 10 ··· Circuit board 1 ···· Laminated bodies 1a to 1e ··· Glass-ceramic layer 2 ····· Surface wiring conductor 3 ··· ..Inner wiring conductor 4... Via-hole conductor 101a... First green sheet 100...

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H05K 3/46 H05K 3/00 H05K 3/28

Claims (1)

(57) Claims: a step of forming one first green sheet having a plurality of circuit board regions and at least one second green sheet; each circuit board section on the surface, to form a conductive film serving as a surface wiring conductor, said surface
Except for a predetermined portion exposing the wiring conductor, the first grid
Continuously forming a film that becomes an overcoat glass layer over a portion of the conductor film over substantially the entire surface of the green sheet, covering each circuit board region, and forming each circuit on the surface on the second green sheet. In the substrate area,
Forming a conductor film to be an internal wiring conductor; laminating the first green sheet on the second green sheet to form a large laminated body; and thereafter, forming each circuit board region in the large laminated body. Forming a dividing groove for partitioning; baking the large laminate to form a large circuit board including a plurality of circuit boards having an internal wiring conductor, a surface wiring conductor, and an overcoat glass layer; and Dividing the substrate along the dividing groove and separating the circuit board into individual circuit boards.