JP2003101169A - Ceramic wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that a plating liquid and the like enters a thick- film circuit on the lower surface of a ceramic wiring board through a division groove to cause corrosion, peeling, etc., at the thick-film circuit, when a metal plate layer is coated on a metalized wiring conductor on the upper surface. SOLUTION: Related to a ceramic wiring board 7, division grooves 3 are formed in all directions at least on the lower surface of a ceramic mother board 1. A metalized wiring conductor 2 on which a metal plate layer is coated is formed on the upper surface of a square region 1a partitioned with the division groove 3, while a thick-film circuit 5 coated with a resin layer 6 comprising organic resin is formed on the lower surface. The division groove 3 positioned outside the square region of the ceramic mother board 1 is coated with a coating material 4 which is obtained by sintering a ceramics paste. Thus, entering of plating liquid or the like into the thick-film circuit 5 from the division groove 3 is effectively prevented to discourage corrosion, peeling, etc., for reliability of the ceramic wiring board 7.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic wiring board having a thick film circuit and a metallized wiring conductor, and on which electronic components such as semiconductor elements are mounted. More specifically, the present invention relates to a ceramic wiring substrate in which a metallized wiring conductor is formed on the upper surface of a rectangular region defined by dividing a ceramic mother substrate by dividing grooves, and a thick film circuit is formed on the lower surface. 2. Description of the Related Art Conventionally, as a ceramic wiring board for mounting electronic components such as a semiconductor device such as a semiconductor integrated circuit device and a capacitor, an insulating material such as an aluminum oxide sintered body is used. A metallized wiring conductor made of a refractory metal material such as tungsten or molybdenum on the upper surface of the substrate, and a thick film circuit such as a thick film wiring or a thick film resistor made of a copper, lanthanum-boron alloy or tin oxide alloy on the lower surface. Are known. The metallized wiring conductor and the thick film circuit are usually
They are electrically connected via an internal wiring layer or the like of the insulating base. An electronic circuit is formed by mounting the electronic component on the upper surface of the insulating base and connecting the electrode to a metallized wiring conductor via solder or a bonding wire, thereby forming the electronic circuit with the metalized wiring conductor and the thick film circuit. An electronic device as a product is completed by sealing the electronic component with a resin or a lid as needed. The metallized wiring conductor functions as a main conductive path for connecting an electrode of an electronic component to a thick-film circuit or leading it to the outside, and the thick-film circuit has a resistance or a low electric resistance in the above electric circuit. Functions as circuit elements such as circuits and capacitors. In this case, the metallized wiring conductor is covered with a plated metal layer of nickel, copper, gold or the like in order to prevent the oxidative corrosion of the metalized wiring conductor and to make the connection of solder and bonding wires reliable and easy. [0006] Further, the thick film circuit is formed by oxidizing copper or tin oxide.
Since it is made of a material that is easily corroded, it is necessary to apply a coating layer to prevent oxidation, as with metallized wiring conductors. Is deviated from a predetermined value, and is usually covered with a resin layer made of an organic resin. As this organic resin, an epoxy resin of an ultraviolet curing type, a thermosetting type or the like is generally used. [0007] Such a ceramic wiring board is
In general, in order to facilitate the handling, dummy ears are provided at a portion surrounding the outside of the rectangular region to be a product, and the dummy ears and the region at the center of the product are divided by dividing grooves. Manufactured in the form of a ceramic motherboard, the dummy ears are removed by dividing the ceramic motherboard along the dividing grooves after a predetermined process such as mounting of electronic components. [0008] Such a ceramic wiring board is manufactured, for example, as follows. First, a ceramic green sheet to be a ceramic mother substrate is prepared, and at least a lower surface of the ceramic green sheet is formed with a notch serving as a dividing groove for partitioning the central portion of the ceramic green sheet into a wiring board region in a square shape. A metal paste such as tungsten or molybdenum is printed and applied on the upper surface of the rectangular region, and then fired at a high temperature to obtain a ceramic mother substrate having a metallized wiring conductor formed on the upper surface. Next, a metal paste such as copper, lanthanum-boron, or the like is printed and applied to the lower surface of the square region of the ceramic mother substrate, and heat-treated at a temperature lower than the above-mentioned firing temperature to form a lower surface of the insulating base. To form a thick film circuit. Next, the thick-film circuit is coated with an organic resin such as an epoxy resin, and finally, a plating metal layer is applied only to the metallized wiring conductor, whereby a ceramic wiring board is manufactured. When the plating metal layer is applied to the metallized wiring conductor on the upper surface of the ceramic mother substrate, the thick film circuit on the lower surface of the ceramic mother substrate and the organic resin covering the thick film circuit are covered with a masking tape. . This is to prevent the plating metal layer from adhering to the thick film circuit, and because the coating organic resin is easily corroded by the acid / alkaline solution, the acid / alkaline plating solution or plating solution is used. This is for protecting the organic resin from the liquid. However, in this conventional ceramic wiring board, since a dividing groove is formed on at least the lower surface, a plating metal layer is applied to the metallized wiring conductor of the ceramic wiring board. When applying a masking tape to the lower surface of the ceramic mother substrate to cover the thick film circuit and the organic resin covering the thick film circuit, the masking tape and the ceramic mother substrate adhere to each other at the portion where the dividing groove is formed. Without doing so, a gap is created. For this reason, when the ceramic wiring board is immersed in the plating solution or plating solution in this state, these chemicals travel along the dividing groove from the above-mentioned gap and the masking tape, the ceramic mother board, and the thick film formed on the ceramic mother board. There is a problem that it penetrates into the circuit and causes corrosion and peeling of the thick film circuit. The present invention has been made in view of the above-mentioned problems in the prior art, and has as its object to apply a plating metal layer to a metallized wiring conductor on the upper surface of a ceramic wiring substrate in a ceramic mother substrate. Another object of the present invention is to provide a ceramic wiring board which does not cause corrosion, peeling, and the like in a thick film circuit on a lower surface. In the ceramic wiring board of the present invention, a dividing groove is formed vertically and horizontally on at least a lower surface of a ceramic mother substrate, and plating is performed on an upper surface of a quadrangular region defined by the dividing groove. A ceramic wiring board comprising a metallized wiring conductor on which a metal layer is adhered, and a thick film circuit formed by coating a lower surface with a resin layer made of an organic resin. Wherein the dividing groove located outside of the substrate is covered with a covering material formed by sintering a ceramic paste. According to the ceramic wiring board of the present invention, since the dividing grooves located outside the quadrangular region of the ceramic mother substrate are covered with the coating material obtained by sintering the ceramic paste, The masking tape can be sufficiently adhered to the ceramic mother substrate through the covering material formed by sintering the ceramic paste even at the portion where the dividing groove is formed outside the square shape of the substrate, and the outer peripheral portion of the ceramic mother substrate The plating solution and plating solution can be effectively prevented from entering the thick film circuit from the area where the dividing groove is formed, making it possible to extremely effectively prevent corrosion and peeling from occurring in the thick film circuit. Can be prevented. Next, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1A is a sectional view showing an example of an embodiment of a ceramic wiring board according to the present invention, and FIG. 1B is a plan view thereof. In the figure, 1 is a ceramic mother substrate (insulating base), 2 is a metallized wiring conductor formed on the upper surface of the ceramic mother substrate 1, 3 is a dividing groove formed on the lower surface of the ceramic mother substrate 1, Is a coating material formed by sintering a ceramic paste, 5 is a thick film circuit formed on the lower surface of the ceramic mother substrate 1, and 6 is a resin layer made of an organic resin for coating the lower surface of the ceramic mother substrate 1. The ceramic mother board 1, the metallized wiring conductor 2, the dividing groove 3, the covering material 4,
The thick film circuit 5 and the resin layer 6 constitute a ceramic wiring board 7. The ceramic mother substrate 1 is made of aluminum oxide sintered body, aluminum nitride sintered body, mullite crystal sintered body, silicon carbide sintered body, silicon nitride sintered body, glass ceramics sintered body. It is made of an electrically insulating material such as a body. For example, in the case of an aluminum oxide-based sintered body, a ceramic slurry obtained by adding an appropriate organic binder and a solvent to a ceramic raw material powder such as aluminum oxide, silicon oxide, magnesium oxide, and calcium oxide is mixed with a conventionally known ceramic slurry. The sheet is formed into a sheet shape by a doctor blade method, and the sheet is subjected to an appropriate punching process to obtain a ceramic green sheet for the ceramic mother substrate 1. Then, these ceramic green sheets are laminated one above the other and have an appropriate shape and size. Then, a green ceramic molded body for the ceramic mother substrate 1 is formed, and thereafter, the molded body is manufactured by firing at a temperature of about 1600 ° C. in a reducing atmosphere. The ceramic mother substrate 1 has a dividing groove 3 formed at least on the lower surface thereof. The dividing groove divides a square region (a wiring substrate region serving as a product) 1a in the center, and the square region 1a. The outer peripheral portion 1b, which is an area outside of the dividing groove 3 that defines the area, serves as a dummy ear. Such a dividing groove 3 can be formed by pressing a cutter blade or the like into the lower surface of the ceramic green sheet serving as the ceramic mother substrate 1 and providing a cut in a groove shape. Further, a metallized wiring conductor 2 is formed on the upper surface of the rectangular region 1a of the ceramic mother substrate 1. The metallized wiring conductor 2 is connected to an electrode of an electronic component (not shown) mounted on the ceramic wiring board 7, leads the electrode to the outside, or connects to the thick film circuit 5. Function as a conductive path. The metallized wiring conductor 2 is made of a metal powder such as tungsten, molybdenum, copper, silver or the like. A metal paste obtained by adding a suitable organic binder and solvent to the metal powder such as tungsten is mixed with the ceramic mother substrate 1. The ceramic green sheet is formed by printing and applying a predetermined pattern on the ceramic green sheet by a conventionally known screen printing method or the like, and firing the ceramic green sheet together with the ceramic green sheet. The metallized wiring conductor 2 is provided on the exposed surface thereof with, for example, a soldering material for connecting an electrode of an electronic component through a low melting point brazing material or a bonding wire in order to improve the bonding property and bonding property of the brazing material. It is preferable that a plating metal film composed of a nickel plating film having a thickness of about 10 μm and a gold plating film having a thickness of about 0.1 to 3 μm is applied. The plating metal film composed of the nickel plating layer and the gold plating layer is made of, for example, an electroless nickel plating bath (acidic) containing nickel sulfate and a phosphorus-based or boron-based reducing agent as a main component, and a gold cyanide plating bath. An electroless gold plating bath (alkaline) containing a lithium and boron-based reducing agent as a main component is prepared, and the metallized wiring conductor 2 is exposed by sequentially immersing the ceramic wiring substrate 7 in each plating bath for a predetermined time. A predetermined thickness is formed on the surface. A rectangular region 1a of the ceramic mother substrate 1
A thick film circuit 5 is formed so as to be electrically connected to the metallized wiring conductor 2. The thick film circuit 5 is made of a resistor powder such as a lanthanum-boron (LaB ₆ ) alloy or tin oxide (SnO ₂ ). In the case of tin oxide, a resistor paste obtained by adding and mixing an appropriate organic binder and solvent to tin oxide powder is applied to the lower surface of the rectangular region 1a of the ceramic mother substrate 1, for example, the ceramic mother substrate 1 Is printed and applied in a predetermined pattern so as to be connected to the metallized wiring conductor 2 via an internal wiring (not shown) provided in advance inside the substrate and heat-treated at a temperature of about 900 ° C. to be baked. It is formed on the lower surface of the substrate 1. The metallized wiring conductor 2 and the thick film circuit 5
Is formed by providing a through hole in a ceramic green sheet to be a ceramic mother substrate 1 and printing and filling the same metal paste as the metallized wiring conductor 2 on the surface of the ceramic green sheet and in the through hole. Can be formed. In general, a protective glass (not shown) is applied on the surface of the thick film circuit 5. This protective glass prevents oxidation of the thick-film circuit 5 and, for example, when the thick-film circuit 5 is a thick-film resistor, when the laser-trimming is performed on the thick-film resistor as described later, a portion other than a portion to be trimmed is used. And prevents the exposed back surface of the portion from being damaged. Such a protective glass is made of, for example, a glass such as a boron oxide glass, and a glass paste obtained by adding and mixing an appropriate organic binder and a liquid agent to the powder of the boron oxide glass is used as a thick film resistor. It is printed and coated so as to cover the entire surface, processed at about 600 to 650 ° C., and baked to be formed. Further, a thick film circuit 5 covered with a protective glass
Because the electric resistance value is adjusted to a predetermined value by laser trimming, the trimmed portion is exposed from the protective glass, and in order to prevent this exposed portion from being oxidized, an organic resin such as an ultraviolet curing type is used. And a resin layer 6 made of The resin layer 6 made of an organic resin is formed of, for example, an ultraviolet-curable epoxy resin, and an uncured epoxy resin precursor is mixed with a suitable additive such as a photopolymerization initiator to form a thick film circuit 5. Is printed and applied so as to cover a predetermined place on the lower surface of the ceramic mother substrate 1 on which is formed
By irradiating ultraviolet rays of about 300 mJ / cm ² and photo-curing, it is formed on the lower surface of the ceramic mother substrate 1 so as to cover the thick film circuit 5 and the protective glass. The thick-film circuit 5 formed on the lower surface of the ceramic mother substrate 1 is made of nickel-based ceramic wiring substrate 7 in order to apply a plating metal layer to the metallized wiring conductor 2 on the upper surface of the ceramic mother substrate 1 as described above. When immersed in a plating solution such as gold or various plating solutions of acid or alkali, it is covered with a masking tape (not shown) so as not to come into contact with the plating solution or the like. The masking tape is applied so as to cover almost the entire lower surface of the ceramic mother substrate 1 in order to cover the entire surface of the thick film circuit 5 and the resin layer 6. As described above, the resin layer 6 is adhered to the lower surface of the ceramic mother substrate 1 and a masking tape is attached.
When applying a plating metal layer to the metallized wiring conductor 2,
In the present invention, it is important that at least the divided groove 3 located outside the rectangular region of the ceramic mother substrate 1 be covered with a covering material 4 formed by sintering a ceramic paste. Since the covering material 4 covers the dividing grooves 3 located outside the rectangular region of the ceramic mother substrate 1, the portions where the dividing grooves 3 located outside the rectangular region are formed Also, the gap between the ceramic mother substrate 1 and the masking tape can be eliminated, and when the ceramic mother substrate 1 is immersed in a plating solution such as gold or a plating solution such as hydrochloric acid / alkali degreasing solution, It is possible to effectively prevent the plating solution or the like from entering the thick film circuit 5 from the division groove located outside the rectangular region. As a result, it is possible to effectively prevent the plating solution or the like from entering the thick film circuit 5, thereby effectively preventing the thick film circuit 5 from being corroded or peeled off, and to improve the reliability of the ceramic wiring board 6. Can be excellent. Such a ceramic paste includes aluminum oxide, aluminum nitride, mullite, silicon carbide,
A mixture obtained by adding an organic solvent and a binder to a ceramic powder such as silicon nitride or borosilicate glass and kneading it can be used. Here, the coating material 4 formed by sintering the ceramic paste applied to the divided grooves 3 located outside the rectangular region of the ceramic mother substrate 1 may be made of the same material as the ceramic mother substrate 1. preferable. This is because the ceramic paste can be fired simultaneously with the ceramic mother substrate 1 and the coating material 4 can be firmly applied to the ceramic mother substrate 1. The covering material 4 is formed on the resin layer 4 on the thick film circuit 5 formed on the lower surface of the ceramic mother substrate 1 at the outer edge.
It is preferable that the thickness be smaller than the thickness. This is because when a stress such as thermal stress is generated between the ceramic mother substrate 1 and the coating material 4, the stress is prevented from increasing at the outer edge of the coating material 4 and the coating layer 4 is prevented from peeling off from the outer edge. This is because the material 4 can be more firmly adhered to the ceramic mother substrate 1. It is preferable that the coating material 4 is formed so that the upper surface thereof forms a plane parallel to the surface of the ceramic mother substrate 1. The coating effect on the plating solution can be obtained almost uniformly, and the intrusion of the plating solution can be more reliably prevented. Such a coating material 4 can be formed, for example, by printing a ceramic paste to be the coating material 4 on a ceramic green sheet to be the ceramic mother substrate 1 and then pressing the ceramic paste on a flat pressing surface. . The ceramic wiring board of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. For example, in the above-described example, the dividing groove 3 is formed only on the lower surface of the ceramic mother substrate 1. However, the dividing groove 3 is formed so as to face the dividing groove 3 on the lower surface or to divide the lower surface. A division groove may be formed on the upper surface of the ceramic mother substrate 1 at a position different from the groove 3. In the above example, only one rectangular region 1a defined by the dividing groove 3 is formed at the center of the ceramic mother substrate 1, but this rectangular region 1a is A so-called multi-cavity ceramic wiring board may be formed in a plurality of square-shaped wiring board areas arranged in a row. In this case, the thick film circuits respectively formed on the lower surfaces of the many wiring board areas 5 may be covered with a resin layer 6 and the dividing groove 3 located outside the wiring board region of the ceramic mother substrate 1 may be covered with a covering material 4 formed by sintering a ceramic paste. According to the ceramic wiring board of the present invention,
A metallized wiring conductor in which division grooves are formed vertically and horizontally on at least the lower surface, and a plating metal layer is adhered on the upper surface of a rectangular area defined by the division grooves, is coated on the lower surface with a coating layer made of an organic resin. This is a ceramic wiring board formed by forming a thick film circuit, and the division grooves located outside the rectangular area of the ceramic mother board are covered with a coating material formed by sintering a ceramic paste. After forming a thick film circuit on the lower surface of the ceramic mother board, the masking is performed when the lower surface having the thick film circuit covered with the coating layer is masked in order to apply a plating metal layer to the metallized wiring conductor on the upper surface. It is possible to effectively prevent the plating solution and the like from entering the thick film circuit from the portion where the groove is formed, so that corrosion and peeling of the thick film circuit can be extremely effectively prevented. That. As described above, according to the present invention, when a plating metal layer is applied to a metallized wiring conductor on the upper surface of a ceramic wiring substrate on a ceramic mother substrate, corrosion, peeling or the like is generated in the thick film circuit on the lower surface. It was possible to provide a ceramic wiring board without any.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is a cross-sectional view and FIG. 1B is a plan view showing an embodiment of a ceramic wiring board according to the present invention. DESCRIPTION OF SYMBOLS 1 ・ ・ ・ Ceramic mother substrate (insulating substrate) 1a ・ ・ ・ Rectangular area (wiring board area to be product) 1b ・ ・ ・ Ear part (outer peripheral part) 2 ・ ・ ・ Metalized wiring conductor 3 ... Division groove 4 ... Coating material 5 ... Thick film circuit 6 ... Resin layer 7 ... Ceramic wiring board

Claims (1)

Claims: 1. A metallized wiring in which a dividing groove is formed vertically and horizontally on at least a lower surface of a ceramic mother substrate, and a plating metal layer is applied to an upper surface of a quadrangular region defined by the dividing groove. A ceramic wiring board formed by forming a thick film circuit in which a conductor is covered with a resin layer made of an organic resin on a lower surface, wherein the dividing groove located outside the rectangular region of the ceramic mother board is formed. A ceramic wiring board, which is covered with a coating material formed by sintering a ceramic paste.