JP5857956B2 - Device mounting substrate and manufacturing method thereof - Google Patents

Description

  The present invention relates to an element mounting substrate and a manufacturing method thereof, and more particularly to an element mounting substrate having excellent resistance to sulfidation and a manufacturing method for manufacturing the element mounting substrate.

  In recent years, low-temperature fired ceramic substrates (LTCC substrates) having an excellent feature of low dielectric constant and low wiring resistance are used as device mounting substrates with high-density mounting of electronic devices and high processing speed. . In addition, use of an LTCC substrate capable of satisfying various characteristics such as weather resistance, light extraction efficiency, and heat dissipation as a substrate for mounting a light emitting element such as a light emitting diode (LED) has been studied.

  The LTCC substrate is fired at a temperature of about 800 to 1000 ° C. which is lower than the firing temperature of normal ceramics, and a predetermined number of green sheets made of glass and ceramic filler (for example, alumina filler or zirconia filler) are stacked. These are manufactured by firing after being integrated by thermocompression bonding.

  On the surface of such an LTCC substrate, a thick film conductor layer formed by firing a paste mainly composed of a conductor metal such as silver or copper is formed as a connection terminal (electrode). On the surface of the thick film conductor layer, for example, a plating layer (nickel / gold plating layer) in which a nickel plating film and a gold plating film are laminated is formed in order to improve wire bonding properties, adhesion strength, weather resistance, and the like. . By forming such a plating layer, it is possible to particularly improve the resistance to sulfidation, and to suppress discoloration of the thick film conductor layer due to a reaction with sulfur in the air or the like (for example, see Patent Documents 1 and 2). .

  By the way, the thick film conductor layer usually has a thickness of about 5 to 15 μm, and the thickness of the plating layer formed thereon, particularly the nickel plating film, is about 5 to 15 μm. However, it is difficult to accurately control the thickness of the nickel plating film, and it may be formed unexpectedly thick. When the thickness of the nickel plating film becomes thicker than usual, for example, close to 20 μm, an excessive tensile stress is applied to the thick film conductor layer, and the end of the thick film conductor layer may be peeled off from the LTCC substrate. When such peeling occurs, moisture enters the gap between the LTCC substrate and the thick film conductor layer, so that the silver in the thick film conductor layer is transmitted to the end portion, and the surface of the plating layer, particularly the outermost gold plating film Spreads up.

  When placed in a sulfide environment in such a state, the silver diffused on the gold plating film on the outermost surface is sulfided, and there is a possibility that the wire bonding property and the like are deteriorated. Further, since the surface of the gold plating film is blackened, the reflectance is lowered, which is not preferable as a mounting substrate for a light emitting element or the like.

  An unfired low-temperature fired ceramic substrate having a printed layer of an Ag-based conductor paste (unfired thick film conductor layer) as the outermost layer in order to improve dimensional accuracy during firing without impairing wire bonding properties An alumina green sheet (green sheet for restraint firing) that is not sintered at a firing temperature (800 to 1000 ° C.) is pressure-bonded to both sides of the substrate, and the substrate and the thick film conductor layer are simultaneously fired in this state, and then the alumina green sheet remains. An LTCC wiring board has been proposed in which a plating film is formed on the rough surface of the thick-film conductor layer thus formed (see, for example, Patent Documents 3 and 4).

  However, in the LTCC wiring board described in Patent Documents 3 and 4, since both sides are pressed with an alumina green sheet for restraint firing, the unfired thick film conductor layer is not fired over the entire thickness. It is difficult to push into a low-temperature fired ceramic substrate. Therefore, in the LTCC wiring boards of Patent Documents 3 and 4, the thick film conductor layer is not completely embedded in the low-temperature fired ceramic substrate, and the end of the thick film conductor layer is sufficiently peeled off due to the stress of the plating film. The sulfidation resistance was insufficient. Moreover, since the surface of the thick film conductor layer is in a rough state due to the removal of the restraint firing green sheet residue, there is a problem that the wire bonding property after the plating process is inferior.

Japanese Utility Model Publication No. 2-36278 JP 2002-314230 A Japanese Patent No. 4123278 See Japanese Patent Application Laid-Open No. 2008-235911

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide an element mounting substrate which is prevented from peeling off at the end of a thick film conductor layer and has excellent sulfidation resistance. Another object of the present invention is to provide a manufacturing method for obtaining such an element mounting substrate having excellent resistance to sulfidation.

The element mounting substrate of the present invention is a low-temperature fired ceramic substrate and a thick-film conductor layer mainly made of silver and formed on at least one main surface of the low-temperature fired ceramic substrate, and has a smooth surface. And a thick-film conductor layer embedded so that the surface is substantially the same height as the main surface of the low-temperature fired ceramic substrate, and a conductive metal plating layer formed on the thick-film conductor layer possess the door, the thick film conductor layer, characterized in that a 0.3μm less surface roughness (Ra).

  In the element mounting substrate of the present invention, the difference in height between the surface of the thick film conductor layer and the main surface of the low-temperature fired ceramic substrate is preferably 2 μm or less. The plating layer is preferably a nickel-gold plating layer.

The method for manufacturing an element mounting substrate of the present invention is a method for manufacturing the element mounting substrate of the present invention described above, and is at least one of an unsintered substrate made of a glass ceramic composition containing glass powder and a ceramic filler. A step of forming an unfired thick film conductor layer made of a metal paste mainly composed of silver, and a pressure plate having a smooth pressing surface on the unfired thick film conductor layer. The unfired thick film conductor layer is pressed in the thickness direction through a pressure plate, and the unfired until the surface of the unfired thick film conductor layer becomes substantially the same height as the main surface of the unfired substrate. A step of pushing into the substrate, a step of heating and firing the unfired substrate with the unfired thick film conductor layer together with the unfired thick film conductor layer, and a conductive surface on the surface of the fired thick film conductor layer. A plating layer made of conductive metal And having a degree.

  According to the present invention, the thick film conductor layer formed on at least one main surface of the low-temperature fired ceramic substrate is embedded so that the surface of the layer is substantially the same height as the main surface of the low-temperature fired ceramic substrate. By forming, the peeling of the thick film conductor layer from the low-temperature fired ceramic substrate can be prevented, and an element mounting substrate having excellent sulfidation resistance can be obtained.

It is a top view which shows an example of the element mounting substrate of this invention. It is XX sectional drawing of the element mounting board | substrate shown in FIG. It is an expanded sectional view which expands and shows a part of FIG. It is sectional drawing for demonstrating the manufacturing method of the element mounting substrate of this invention.

  The present invention will be described below with reference to the drawings.

  FIG. 1 is a plan view showing an example of the element mounting substrate 1 of the present invention. 2 is a sectional view taken along line XX of the element mounting substrate 1 shown in FIG. 1, and FIG. 3 is an enlarged sectional view showing a part of FIG.

  The element mounting substrate 1 of the present invention has a low-temperature fired ceramic substrate (LTCC substrate) 2 made of a sintered body of a glass ceramic composition containing glass powder and a ceramic filler. One main surface of the LTCC substrate 2 is a mounting surface 2a on which a semiconductor element, for example, a light emitting element such as an LED element is mounted. The shape, thickness, size, etc. of the LTCC substrate 2 are not necessarily limited. Further, on the mounting surface 2a side of the LTCC substrate 2, there may be provided a side wall (not shown) that surrounds the central portion and has an inner shape, for example, a circular shape.

  On the mounting surface 2a, a thick film conductor layer 3 made of a metal mainly composed of silver and serving as a connection terminal (electrode) with a semiconductor element is formed. The thick film conductor layer 3 is embedded in the LTCC substrate 2 so as to have a smooth (flat) surface with no irregularities and to have a surface that is substantially the same height as the mounting surface 2 a of the LTCC substrate 2. In the present specification, “substantially the same height” means that the difference in height is preferably 10 μm or less, more preferably 5 μm or less. The surface of the thick film conductor layer 3 may be either higher than the mounting surface 2a of the LTCC substrate 2, but it is preferable that both of them are the same height, that is, flush with each other. In particular, if the surface of the thick film conductor layer 3 is above the mounting surface 2a of the LTCC substrate 2 and the height difference (step) (h) is preferably 2 μm or less, more preferably 1 μm or less, the thickness The effect of preventing the film conductor layer 3 from peeling off can be sufficiently mentioned. If the difference in height exceeds 2 μm, a tensile stress is applied to the plating film 4, so that the thick film conductor layer 3 is easily peeled off. Further, if the surface of the thick film conductor layer 3 is below the mounting surface 2a of the LTCC substrate 2, a step is generated on the surface of the plating film 4, which may cause a wire bonding failure.

  As will be described later, the thick-film conductor layer 3 is formed by printing a metal paste by screen printing or the like, pressurizing it and firing it into the substrate. The surface roughness (arithmetic mean roughness) Ra of the thick film conductor layer 3 is preferably 0.3 μm or less, and more preferably 0.2 μm or less. Ra is calculated | required by JISB0601: 1982. When Ra exceeds 0.3 μm, a thin film portion is partially generated after the plating process is performed, the film effect by plating is reduced, and the thick film conductor layer 3 may be deteriorated in the weather resistance test. There is.

  Thus, the plating layer 4 made of a conductive metal is formed on the surface of the thick film conductor layer 3 embedded in the LTCC substrate 2. Although not shown, the plating layer 4 is composed of, for example, a nickel plating film that covers the surface of the thick film conductor layer 3 and a gold plating film that covers the surface of the nickel plating film, and the LTCC substrate 2 of the thick film conductor layer 3. The exposed surface is covered with no gaps.

  On the other hand, on the non-mounting surface 2b opposite to the mounting surface 2a of the LTCC substrate 2, a thick film conductor layer 3 serving as a connection terminal (electrode) for external connection is formed. This thick film conductor layer 3 also has a smooth surface, and the surface thereof is substantially the same height as the non-mounting surface 2b of the LTCC substrate 2, as is the case with the thick film conductor layer 3 on the mounting surface 2a side. As shown in FIG. A plating layer 4 made of a conductive metal is also formed on the surface of the thick film conductor layer 3 exposed from the LTCC substrate 2. The thick film conductor layer 3 and the plating layer 4 on the non-mounting surface 2b side can be made of the same material as the thick film conductor layer 3 and the plating layer 4 on the mounting surface 2a side, respectively.

  Further, a through conductor 5 is provided inside the LTCC substrate 2 to electrically connect a connection terminal for element connection on the mounting surface 2a and a connection terminal for external connection on the non-mounting surface 2b. The through conductor 5 can be made of the same material as the thick film conductor layer 3 formed on the mounting surface 2a and the non-mounting surface 2b.

  According to such an element mounting substrate 1, since the thick film conductor layer 3 is embedded in the LTCC substrate 2, the plating layer 4, particularly the nickel plating film, is formed unexpectedly thick, and as a result, the thick film conductor layer 3. Even when excessive tensile stress is applied to the thick film conductor layer 3, it is possible to prevent the end portion of the thick film conductor layer 3 from peeling off from the LTCC substrate 2. Thereby, it can suppress that the silver which comprises the thick film conductor layer 3 diffuses in the state of silver ion to the plating layer 4 surface, and can prevent sulfidation in a sulfide environment. Therefore, it is possible to obtain an element mounting substrate 1 that has good wire bonding properties and the like and that has a good reflectance required when mounting a light emitting element.

  The element mounting substrate 1 of the present invention is characterized in that a thick film conductor layer 3 formed on at least the mounting surface 2 a of the LTCC substrate 2 is embedded in the LTCC substrate 2. The thick film conductor layer 3 on the non-mounting surface 2b side does not necessarily need to be embedded in the LTCC substrate 2 and may be formed on the non-mounting surface 2b. By adopting a structure in which the conductor layer 3 is embedded in the LTCC substrate 2, the sulfidation resistance can be further improved.

  Next, the manufacturing method of the element mounting substrate 1 of the present invention will be described. 4 (a) and 4 (b) are cross-sectional views of the element mounting substrate 1 for explaining the pressurizing / firing process in the production of the present invention. In FIG. 4 and the following description, members used for manufacturing the element mounting substrate 1 will be described with the same reference numerals as the members of the element mounting substrate 1 that is finally formed by this member.

  The manufacturing method of the element mounting substrate 1 of the present invention is to manufacture an unfired substrate 2 made of a glass ceramic composition containing glass powder and a ceramic filler, and the mounting surface 2a and the non-mounting surface 2b are mainly composed of silver. Smooth (flat) on the both sides of the unfired thick film conductor layer 3 formed with the step of forming the unfired thick film conductor layer 3 made of a metal paste (unfired substrate manufacturing process) ) A pair of pressure plates 6 having pressing surfaces are arranged so that each pressing surface comes into contact with the surface of the corresponding unfired thick film conductor layer 3, and the unfired thick film is interposed through these pressure plates 6. The conductor layer 3 is pressed in the thickness direction and pressed into the unfired substrate 2, and heated and fired in that state (pressure and firing step), and the exposed surface of the thick film conductor layer 3 embedded in the substrate is electrically conductive. For forming the plating layer 4 made of conductive metal Having a plating process) and.

  In the green substrate manufacturing process, first, a green sheet to be the green substrate 2 is formed. The green sheet is prepared by adding a binder, and optionally a plasticizer, a solvent, etc. to a glass ceramic composition containing glass powder and a ceramic filler, and forming this into a sheet by the doctor blade method or the like. It can be manufactured by drying.

  The glass powder is not necessarily limited, but preferably has a glass transition point (Tg) of 550 to 700 ° C, more preferably 600 to 680 ° C. When the glass transition point (Tg) is lower than 550 ° C., degreasing described later may be difficult. When the glass transition point (Tg) is higher than 700 ° C., the shrinkage start temperature is increased, and the dimensional accuracy may be decreased.

As the glass powder, for example, SiO ₂ is selected from 57 to 65 mol%, B ₂ O ₃ is 13 to 18 mol%, CaO is 9 to 23 mol%, Al ₂ O ₃ is ₃ to 8 mol%, K ₂ O and Na ₂ O are selected. Glass powder containing a total of at least one of 0.5 to 6 mol% is used. The glass powder has a 50% particle size (D ₅₀ ) of preferably 0.5 to 2 μm, and more preferably 1.0 to 1.8 μm. If D ₅₀ of the glass powder is less than 0.5 [mu] m, the glass powder is likely to agglomerate, handle not only difficult, it is difficult to uniformly disperse. On the other hand, when D ₅₀ exceeds 2 μm, the glass softening temperature may increase or the sintering may be insufficient. In addition, the particle size described in this case is measured by a laser diffraction / scattering method.

As the ceramic filler, those conventionally used for the production of LTCC substrates can be used. For example, alumina powder, zirconia powder, mixed powder of alumina powder and zirconia powder, and the like can be suitably used. The D ₅₀ of the ceramic filler is preferably 0.5 to 4 μm.

  Such glass powder and ceramic filler, for example, glass powder is 30 to 50% by mass, more preferably 35 to 40% by mass, and ceramic filler is 50 to 70% by mass, more preferably 60 to 65% by mass. A glass ceramic composition can be obtained by blending and mixing. Moreover, a slurry can be obtained by adding a binder and, if necessary, a plasticizer, a solvent, and the like to the glass ceramic composition.

  As the binder, for example, polyvinyl butyral, acrylic resin and the like can be suitably used. As the plasticizer, for example, dibutyl phthalate, dioctyl phthalate, butyl benzyl phthalate and the like can be used. As the solvent, aromatic or alcoholic organic solvents such as toluene, xylene and butanol can be used. Furthermore, a dispersing agent and a leveling agent can be used together.

  The green sheet thus manufactured is cut into a predetermined dimensional angle using a punching die or a punching machine, and via holes for interlayer connection are formed by punching to form an unfired substrate 2. An unfired thick film conductor layer 3 is formed by printing a metal paste mainly composed of silver on both surfaces (mounting surface 2a and non-mounting surface 2b) of the unfired substrate 2 by a method such as screen printing. Further, the unfired through conductor 5 is formed by filling a metal paste mainly composed of silver in the via hole for interlayer connection.

  As a metal paste, a metal powder mainly composed of silver, specifically, a metal powder containing 50% by mass or more of silver, and a vehicle such as ethyl cellulose, and a solvent or the like as necessary are added into a paste. Can be used. As the metal powder, silver powder, mixed powder of silver and palladium, mixed powder of silver and platinum, and the like are preferably used. In the case of a mixed powder of silver and palladium, the silver content is preferably 90% by mass or more and the palladium content is 10% by mass or less. In the case of a mixed powder of silver and platinum, preferably silver is contained in an amount of 97% by mass or more and platinum is contained in an amount of 3% by mass or less. In the present invention, the glass component contained in the LTCC substrate 2 can ensure sufficient adhesion between the metal and the substrate, and the metal paste does not increase the electrical resistance value of the metal. It is preferable not to mix glass frit.

  In the pressurizing / firing step, first, as shown in FIG. 4A, smooth pressing is performed on both surfaces (the mounting surface 2a and the non-mounting surface 2b) of the unfired substrate 2 on which the unfired thick film conductor layer 3 is formed. A pair of metal plates 6 having a surface are arranged such that each pressing surface comes into contact with the surface of the corresponding unfired thick film conductor layer 3. In addition, the metal plate 6 arrange | positioned at the non-mounting surface 2b side can be used as the base or base | substrate which has a smooth press surface.

  Then, the unfired thick film conductor layers 3 on the mounting surface 2 a side and the non-mounting surface 2 b side are pressed in the thickness direction through these metal plates 6 and pressed into the unfired substrate 2. At this time, the unfired thick film conductor layer 3 is pushed into the unfired substrate 2 until the pressing surface of the metal plate 6 contacts the corresponding mounting surface 2a or non-mounting surface 2b of the unfired substrate 2. By heating in such a state, the unfired thick film conductor layer 3 and the unfired substrate 2 are fired simultaneously.

  The metal plate 6 has sufficient rigidity so that the unsintered thick film conductor layer 3 can be applied to the unsintered substrate 2, for example, 5 to 30 MPa, and is pressed. It is preferable to use a stainless steel plate having a smooth surface formed by mirror finishing or the like.

  In the firing step, the unfired substrate 2 having the unfired thick film conductor layer 3 thus pressed is heated to a temperature of, for example, 500 to 600 ° C., more preferably 530 to 570 ° C., and a binder such as a resin is decomposed. Then, after degreasing to be removed, the unfired substrate 2 made of the glass ceramic composition is fired by heating to 800 to 1000 ° C., more preferably 840 to 930 ° C. The unfired thick film conductor layer 3 and the unfired through conductor 5 made of paste are fired to form the thick film conductor layer 3 and the through conductor 5. In this way, as shown in FIG. 4B, a fired substrate is obtained in which the surface of the thick film conductor layer 3 is embedded so as to be approximately the same height as the mounting surface 2a and the non-mounting surface 2b of the LTCC substrate 2.

  In the plating step, the plating layer 4 is formed on the exposed surface of the thick film conductor layer 3 embedded in the LTCC substrate 2 in this way. The plating layer 4 can be formed by performing gold plating after nickel plating, for example. The nickel plating is formed to a thickness of 5 to 40 μm, more preferably 5 to 20 μm, for example, by electrolytic plating using a nickel sulfamate bath. The gold plating is formed to a thickness of 0.1 to 1.0 μm, more preferably 0.2 to 0.6 μm, for example, by electrolytic plating using a potassium gold cyanide bath.

  Thus, the thick film conductor layer 3 is embedded in the LTCC substrate 2, and the surface exposed from the LTCC substrate 2 of the thick film conductor layer 3 is covered with the plating layer 4, and the element mounting substrate 1 having excellent sulfidation resistance. Can be manufactured.

  Examples of the present invention will be described below.

(Example)
As the element mounting substrate 1, the substrate shown in FIGS. 1 and 2 was manufactured through the pressurization / firing process shown in FIG. 4. First, a green sheet for a substrate to be the LTCC substrate 2 was produced. The substrate green sheet is 60.4 mol% SiO ₂ , 15.6 mol% B ₂ O ₃ , 6 mol% Al ₂ O ₃ , 15 mol% CaO, 1 mol% K ₂ O, ₂ mol% Na ₂ O. The raw materials were blended and mixed so as to become, and the raw material mixture was put in a platinum crucible and melted at 1600 ° C. for 60 minutes, and then the molten glass was poured out and cooled. This glass was pulverized with an alumina ball mill for 40 hours to produce a glass powder (D ₅₀ = 1.8 μm). In addition, ethyl alcohol was used as a solvent for pulverization.

  35% by mass of this glass powder, 40% by mass of alumina filler (manufactured by Showa Denko KK, trade name: AL-45H), and zirconia filler (manufactured by Daiichi Rare Element Chemical Industries, trade name: HSY-3F-J) A glass ceramic composition was produced by blending and mixing so as to be 25% by mass. 50 g of this glass ceramic composition, 15 g of an organic solvent (toluene, xylene, 2-propanol, 2-butanol mixed at a mass ratio of 4: 2: 2: 1), plasticizer (di-2-ethylhexyl phthalate) 2.5 g of polyvinyl butyral (trade name: PVK # 3000K, manufactured by Denka Co., Ltd.) as a binder, 5 g, and 0.5 g of a dispersant (trade name: BYK180, manufactured by Big Chemie) were blended and mixed to prepare a slurry. .

  This slurry was applied onto a polyethylene terephthalate (PET) film by a doctor blade method and dried to produce a green sheet for a substrate having a thickness after firing of 0.15 mm.

  On the other hand, a metal powder mainly composed of silver (manufactured by Daiken Chemical Industry Co., Ltd., trade name: S400-2) and ethyl cellulose as a vehicle are blended at a mass ratio of 90:10, and the solid content is 87% by mass. After being dispersed in α-terpineol as a solvent, a metal paste was produced by kneading for 1 hour in a porcelain mortar and further dispersing three times with three rolls.

  A through hole having a diameter of 0.3 mm is formed in a portion where the through conductor 5 of the green sheet for substrate is formed by using a hole puncher, and a metal paste is filled into the through hole by a screen printing method to form an unfired through conductor. 5 and a metal paste was applied on both sides by screen printing to form an unfired thick film conductor layer 3 to produce an unfired substrate 2.

  Next, a 1 mm thick stainless steel plate having a mirror-finished surface is pressed against both sides of the unfired substrate 2 on which the unfired thick film conductor layer 3 is formed, and a pressure of 10 MPa is applied in the thickness direction to unfire the unfired substrate 2. The thick film conductor layer 3 was pushed into the unfired substrate 2. Then, after releasing the pressure, degreasing was performed by holding at 550 ° C. for 5 hours, and baking was further performed at 870 ° C. for 30 minutes. In this way, a substrate in which the surface of the thick film conductor layer 3 was embedded so as to be the same height as the surface of the LTCC substrate 2 was manufactured.

  Thereafter, a 7 μm nickel plating film was formed on the thick film conductor layer 3 exposed from the LTCC substrate 2 by electrolytic plating using a nickel sulfamate bath. A plating layer 4 was formed by forming a gold plating film having a thickness of 0.3 μm on the surface by electrolytic plating using a potassium gold cyanide bath. In this way, the element mounting substrate 1 was manufactured.

(Comparative example)
In the manufacture of the element mounting substrate of the example, the unfired substrate 2 on which the unfired thick film conductor layer 3 was formed was degreased and fired without being pressed by a stainless steel plate. Then, the entire surface of the thick film conductor layer 3 of the fired substrate was plated to manufacture the element mounting substrate 1.

  Next, the element mounting substrates 1 manufactured in the examples and comparative examples were exposed for 100 hours in a sulfidation test according to JIS-C-60068-2-43, and the surface of the gold plating film was sulfidized (black). Was observed with a 20 × microscope. Moreover, about peeling of the thick film conductor layer 3, the cross section was observed by 2000 times with the electron microscope.

  As a result of the sulfidation resistance test, the end portion of the thick film conductor layer 3 is not peeled off in the element mounting substrate 1 of the example, and the diffusion and sulfidation of silver ions on the surface of the plating layer 4 are effectively suppressed. It was recognized that On the other hand, regarding the element mounting substrate 1 of the comparative example in which the thick film conductor layer 3 was not embedded, peeling of the end portion of the thick film conductor layer 3 from the LTCC substrate 2 was observed. It was confirmed that silver ions diffused and sulfided on the surface of the plating layer 4.

The element mounting substrate provided by the present invention, which prevents the thick film conductor layer from peeling off from the substrate and has excellent sulfidation resistance, has excellent characteristics such as weather resistance, light extraction efficiency, and heat dissipation. As a mounting substrate for a light emitting element such as a diode (LED), it is used in a wide range of fields.
The entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2010-107053 filed on May 7, 2010 are cited herein as disclosure of the specification of the present invention. Incorporated.

DESCRIPTION OF SYMBOLS 1 ... Element mounting board | substrate 2 ... LTCC board | substrate 3 ... Thick film conductor layer 4 ... Plating layer 5 ... Through-conductor 6 ... Metal plate

Claims (10)

A low-temperature fired ceramic substrate;
A thick-film conductor layer made of a metal mainly composed of silver and formed on at least one main surface of the low-temperature fired ceramic substrate, having a smooth surface, and the surface is the main surface of the low-temperature fired ceramic substrate A thick film conductor layer embedded to be approximately the same height as,
It has a plating layer of a conductive metal formed on the thick film conductor layer,
The element mounting substrate , wherein the thick film conductor layer has a surface roughness (Ra) of 0.3 μm or less .   The element mounting substrate according to claim 1, wherein a difference in height between the surface of the thick film conductor layer and the main surface of the low-temperature fired ceramic substrate is 2 μm or less. The element mounting substrate according to claim 1, wherein the plating layer includes a nickel layer and a gold plating layer thereon. The element mounting substrate according to claim 1, wherein the plating layer has a nickel plating layer having a thickness of 5 to 40 μm and a gold plating layer having a thickness of 0.1 to 1.0 μm. The element mounting substrate according to claim 1, wherein the thick film conductor layer is formed on an element mounting surface of a low-temperature fired ceramic substrate. A device mounting substrate manufacturing method for manufacturing the device mounting substrate according to claim 1,
Forming an unfired thick film conductor layer made of a metal paste mainly composed of silver on at least one principal surface of an unfired substrate made of a glass ceramic composition containing glass powder and a ceramic filler;
A pressure plate having a smooth pressing surface is disposed on the unfired thick film conductor layer, and the unfired thick film conductor is pressed through the pressure plate in the thickness direction. Pressing the green substrate until the surface of the layer is substantially the same height as the main surface of the green substrate;
Heating and firing the unfired substrate into which the unfired thick film conductor layer has been pressed, together with the unfired thick film conductor layer;
Forming a plated layer made of a conductive metal on the surface of the fired thick film conductor layer;
A method for manufacturing an element mounting substrate, comprising: The manufacturing method of the board | substrate for element mounting of Claim 6 in which the said glass ceramic composition contains 30-50 mass% of glass powder, and 50-70 mass% of ceramic fillers. The method for manufacturing an element mounting substrate according to claim 6 or 7, wherein the metal mainly composed of silver is silver, silver and palladium, or silver and platinum. The manufacturing of the element mounting substrate according to any one of claims 6 to 8, wherein the step of heating and baking is performed by heating to a temperature of 500 to 600 ° C and then heating to a temperature of 800 to 1000 ° C. Method. The method for manufacturing an element mounting substrate according to any one of claims 6 to 9, wherein in the step of forming the plating layer, a nickel plating layer is formed by electrolytic plating, and a gold plating layer is formed thereon by electrolytic plating.

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