JP4452216B2 - Ceramic package for light emitting device and method for manufacturing the same - Google Patents

Description

  The present invention relates to a ceramic package for a light emitting device and a method for manufacturing the same, and more particularly, to a structure capable of reflecting a luminous flux of a light emitting device in a predetermined direction when the light emitting device is mounted in a cavity formed in a ceramic substrate. The present invention relates to a ceramic package and a manufacturing method thereof.

  As a kind of light emitting element, a light emitting diode (hereinafter also referred to as an LED element) is well known. In recent years, as a result of putting high-luminance blue light-emitting diodes into practical use, high-luminance white light can be obtained by combining red, green, and blue LED elements. Therefore, development for using these three-color LED elements as a light bulb or a headlight of an automobile is underway. Since the LED element has an advantage of low power consumption, if the LED element is used for the headlight, the load on the battery can be reduced. In addition, since the LED element also has an advantage of a long life, application to indoor lighting such as a fluorescent lamp and a light bulb is also being studied. When the LED element is used in the above-described application, in order to maximize the advantages of the LED element, it is an important factor that the performance of the package itself for mounting the LED element is good. In this regard, the ceramic package is considered to be suitable for mounting an LED element because it is superior in durability, heat resistance, corrosion resistance, and heat dissipation compared to, for example, an organic package.

  A conventional ceramic package for an LED element has a cavity capable of accommodating the LED element at the center of the upper surface of the ceramic substrate (see, for example, Patent Document 1). A conductor layer which is a mounting portion of the LED element is formed by metallization at a substantially central portion of the bottom surface of the cavity, and the LED element is bonded onto the conductor layer. A metallized layer is formed on the side surface of the cavity, and a first nickel layer, a second nickel layer, and a silver plating layer are sequentially stacked thereon. As a result, the surface of the outermost silver plating layer functions as a light reflecting surface, and reflects the luminous flux of the LED element in the thickness direction of the ceramic substrate.

A package having such a structure can be manufactured by the ceramic green sheet lamination method through the following procedure. First, a green sheet having a cavity is prepared, and a conductive paste for forming a metallized layer is applied to the inner surface of the cavity by a screen printing method or the like. Next, the green sheet after paste printing is fired to obtain a ceramic sintered body having a metallized layer. Thereafter, the first nickel plating, the second nickel plating, and the silver plating are sequentially performed to complete the package. In this case, both the first nickel plating layer and the second nickel plating layer are formed using a general matte nickel plating bath that is usually used.
JP 2004-228549 A

By the way, in the prior art described in Patent Document 1, the first nickel plating layer containing cobalt is formed in order to ensure suitable adhesion with the metallized layer. Moreover, in order to ensure suitable adhesiveness with the silver plating layer in a surface layer, the 2nd nickel plating layer containing cobalt is formed.
However, when the second nickel plating layer is formed using a general matte nickel plating bath, the crystal grains of the second nickel plating layer become rough, and minute irregularities are likely to occur on the surface. Therefore, when a silver plating layer is formed on such a second nickel plating layer, the influence of the minute unevenness also affects the silver plating layer, and the surface of the silver plating layer (that is, the light reflecting surface) becomes rough. End up. Therefore, the glossiness decreases and the light from the LED element cannot be efficiently reflected.

  The present invention has been made in view of the above problems, and its object is to provide a high-quality light reflecting surface that is excellent in adhesion between the metallized layer and the nickel layer and can efficiently reflect the luminous flux from the light emitting element. An object of the present invention is to provide a ceramic package for a light emitting device. Another object of the present invention is to provide a method suitable for manufacturing the above-described excellent ceramic package.

As means (means 1) for solving the above problems, a ceramic having a substrate main surface and a cavity opened in the substrate main surface, and a mounting portion capable of mounting a light emitting element on the inner surface of the cavity is provided. A substrate, a metallized layer formed on the inner surface of the cavity, a first nickel layer formed on the metallized layer, a second nickel layer located on the surface layer side of the first nickel layer, and the first Between the second nickel layer and the reflective metal layer, which is located on the surface layer side of the 2 nickel layer and whose surface can function as a light reflecting surface that reflects the luminous flux from the light emitting element, and between the second nickel layer and the reflective metal layer and a strike plating layer interposed, the second nickel layer is a nickel plating layer containing a brightening agent, the first layer of nickel Ri nickel plating layer der substantially free of brightener The thickness of the first nickel layer is 0.5 μm to 2 μm, the thickness of the second nickel layer is 2 μm to 10 μm, and the thickness of the strike plating layer is 0.03 μm to 0.2 μm. as its gist the ceramic package for a light emitting element, characterized in that it.

  Therefore, according to the package of means 1, the nickel plating layer containing the brightener generally has fine crystal grains and has a high surface smoothness. Therefore, the surface smoothness of the reflective metal layer formed thereon with such a nickel plating layer as a base layer is also high, and the luminous flux from the light emitting element can be efficiently reflected. Moreover, since the 1st nickel layer formed on a metallization layer is a nickel plating layer which does not contain a brightener substantially, compared with the same nickel plating layer containing a brightener, the adhesiveness with respect to a metallization layer is high. Therefore, a package having excellent connection reliability with the metallized layer can be realized.

  The ceramic substrate constituting the ceramic package is a plate-like member having a substrate main surface, and is mainly composed of a ceramic insulating material such as alumina, aluminum nitride, silicon nitride, boron nitride, beryllia, or mullite. The ceramic substrate preferably has a conductor layer for supplying electric power to the light emitting element, and it is particularly preferable to use a ceramic multilayer substrate having two or more such conductor layers.

  The ceramic substrate has one or more cavities that open at the main surface of the substrate. A mounting portion for mounting the light emitting element is provided at a substantially central portion of the bottom surface of the cavity. Specific examples include a mounting pad formed by a technique such as metallization.

  Although a LED element is mentioned as a suitable example of the light emitting element which should be mounted in a mounting part, things other than this, for example, a semiconductor laser element (LD element), VCSEL, etc. may be used. There may be one light emitting element or a plurality of light emitting elements mounted in one cavity. For example, you may comprise so that white light may be obtained by mounting red, green, and blue LED elements in one cavity.

  The side surface of the cavity may be inclined with respect to the bottom surface of the cavity, for example, at an angle of 20 ° or more and less than 80 °, particularly 30 ° or more and less than 70 °, and the cavity may be expanded from the bottom surface toward the substrate main surface. . With this configuration, the emitted light flux of the light emitting element is easily reflected in the thickness direction of the ceramic substrate. The side surface of the cavity may be a vertical surface that forms an angle of 90 ° with respect to the bottom surface of the cavity.

  The metallized layer constituting the ceramic package is formed on the inner surface of the cavity. The metallized layer is formed by applying a conductive paste containing a metal powder by a conventionally well-known method, for example, a metallized printing method, followed by baking. When the metallized layer and the ceramic substrate are formed by the simultaneous firing method, the metal powder in the metallized layer needs to have a melting point higher than the firing temperature of the ceramic substrate. For example, when the ceramic substrate is made of a so-called high-temperature fired ceramic (for example, alumina or the like), tungsten (W), molybdenum (Mo), manganese (Mn), or the like can be selected as the metal powder in the metallized layer. When the ceramic substrate is made of a so-called low-temperature fired ceramic (for example, glass ceramic), copper (Cu), silver (Ag), or the like can be selected as the metal powder in the metallized layer in addition to tungsten and molybdenum.

  The first nickel layer constituting the ceramic package is formed on the metallized layer. Further, the second nickel layer is located on the surface layer side of the first nickel layer. All of these layers serve as an underlayer for the reflective metal layer. The second nickel layer may be directly formed on the first nickel layer, or may be indirectly formed through one or more metal layers made of a metal other than nickel. . Specific examples of the latter include a structure in which a brazing material layer is formed on a first nickel layer and a second nickel layer is formed thereon. As the brazing material layer, copper-based brazing material, silver-based brazing material and the like are suitable. The brazing material layer may be formed in a flat shape with a uniform thickness, but may be intentionally formed in a fillet shape. An advantage of forming the brazing material layer in a fillet shape is that the side surface of the cavity can be inclined with relative ease.

  The second nickel layer is a nickel plating layer containing a brightener (that is, a bright nickel plating layer). This is because the bright nickel plating layer has high surface smoothness, and thus when the reflective metal layer is formed thereon, the surface smoothness of the reflective metal layer also becomes high. The second nickel layer may be a so-called semi-bright nickel plating layer having a brightener content less than that of a normal bright plating layer.

  On the other hand, the first nickel layer is a nickel plating layer (matte nickel plating layer) that does not substantially contain a brightener. This is because the first nickel layer formed on the metallized layer has higher adhesion to the metallized layer than the nickel plated layer containing the brightener. “Substantially no brightener” means not containing any brightener, and the amount of the brightener is very small compared to other ingredients containing the brightener. Including cases that are hardly recognized.

  Here, the brightener includes a primary brightener and a secondary brightener. The primary brightener refers to an additive having a function of imparting luster by refining the crystal of plating. Specific examples thereof include benzenesulfonic acid, saccharin, sodium 1,3,6 naphthalene trisulfonate, Paratoluenesulfonamide and the like. The secondary brightener refers to an additive having a function of smoothing the plating surface, and specific examples thereof include formaldehyde, coumarin, 2 butyne-1,4 diol, thiourea, pyridine and the like. As this type of brightener, not only organic type but also inorganic type can be used.

  The glossiness of the second nickel layer is preferably greater than the glossiness of the first nickel layer. To give a more specific example, light is incident from two locations that form an angle of 45 ° with respect to the measurement target surface of the measurement object, and the reflected light of the incident light is 90 ° with respect to the measurement target surface. When the value obtained by subtracting the logarithm of the reflected light intensity with respect to the incident light intensity from 2 is defined as the glossiness (BLK value), the glossiness (BLK value) of the second nickel layer is 1.0 or more. It is preferably 2.5 or less, and the glossiness (BLK value) of the first nickel layer is preferably 0.1 or more and 0.8 or less. More preferably, it is 0.2 or more and 0.4 or less. The measurement of glossiness (BLK value) by this method is usually carried out not on the finished product but on the in-process product (that is, the intermediate product with the measured layer exposed on the surface).

  The first nickel layer may or may not contain cobalt. However, when there is a brazing material layer between the first nickel layer and the second nickel layer, it is preferable that the first nickel layer does not contain cobalt from the viewpoint of wettability of the brazing material.

  On the other hand, it is preferable that the second nickel layer does not substantially contain cobalt. The reason is that since the second nickel layer is not in contact with the metallized layer, it is not necessary to have heat resistance that can withstand heat treatment for improving adhesion. Further, the nickel layer substantially not containing cobalt is likely to have higher surface smoothness and therefore higher glossiness than the nickel layer containing cobalt. “Substantially free of cobalt” means that it contains no cobalt at all, and its amount is very small compared to other components containing cobalt, so that the effect of addition is hardly recognized. Including cases. For example, the cobalt content of the second nickel layer is preferably 0.1% by weight or less in the finished product, and particularly preferably 0% by weight or more and 0.001% by weight or less (detection level or less). Here, as a measuring method of cobalt content, the method etc. which cut | disconnect a nickel layer and quantitatively analyze the cross section by EDS etc. are mentioned, for example. In addition, the measurement of cobalt content by this method is implemented regardless of a finished product and an intermediate product.

  The nickel crystal grains constituting the second nickel layer are preferably finer than the nickel crystal grains constituting the first nickel layer. More specifically, the average grain size of the nickel crystal grains constituting the second nickel layer is preferably less than 1.0 μm, more preferably less than 0.1 μm. The average grain size of the nickel crystal grains constituting the first nickel layer is preferably 1.0 μm or more and 10.0 μm or less. It is because it is convenient for improvement of glossiness that the 2nd nickel layer is 1.0 micrometer or less.

  The surface roughness Ra of the first nickel layer is preferably smaller than the surface roughness Ra of the metallized layer, and the surface roughness Ra of the second nickel layer is smaller than the surface roughness Ra of the first nickel layer. It is preferable. More specifically, the surface roughness Ra of the metallized layer is 1.0 μm or more, the surface roughness Ra of the first nickel layer is 0.4 μm or more and less than 1.0 μm, and the surface roughness Ra of the second nickel layer is 0.00. It is good that they are 1 micrometer or more and less than 0.4 micrometer. That is, it is preferable that the surface roughness Ra decreases as it goes to the surface layer side, such as metallized layer → first nickel layer → second nickel layer. And according to this structure, it becomes easy to form a reflective metal layer with high surface flatness. Here, as a method for measuring the surface roughness Ra, there are conventionally known methods such as a stylus method, a light cutting method, a light reflection method, and the like. The measurement of the surface roughness Ra by these methods is usually performed not on the finished product but on the in-process product. The stylus method refers to a method of measuring by moving mechanically, electrically, or optically the movement of the needle up and down according to the unevenness of the surface by moving the object on the surface of the object to be measured. The light cutting method is a method for optically observing the profile in one cross section of the object to be measured directly, irradiating parallel light from a thin slit toward the surface, and measuring the surface with a microscope. That means. The light reflection method refers to a method of irradiating the surface of an object to be measured with a parallel light beam and obtaining an average roughness based on the intensity of the reflected light beam.

  The thickness of the second nickel layer is preferably 1 μm or more, preferably 1 μm or more and 15 μm or less, and particularly preferably 2 μm or more and 10 μm or less. That is, when the thickness is less than 1 μm, it is difficult to ensure the smoothness of the surface, and there is a possibility that the second nickel layer having a sufficiently high glossiness may not be obtained. In that respect, if it is in the range of 2 micrometers or more and 10 micrometers or less, the 2nd nickel layer which has sufficiently high glossiness can be obtained reliably, suppressing the cost for formation of a layer to some extent.

  The thickness of the first nickel layer is preferably 0.5 μm or more, and preferably 0.5 μm or more and 2 μm or less. It is because there exists a possibility that suitable adhesiveness with respect to a metallization layer may not be obtained as it is thickness of less than 0.5 micrometer. Moreover, it is because the influence of the unevenness | corrugation in a metallization layer will spread easily on the surface of a 1st nickel layer. In that respect, if it is in the range of 0.5 μm or more and 2 μm or less, the first nickel layer having sufficiently high adhesion and few surface irregularities can be reliably obtained while suppressing the cost for forming the layer to some extent. Can do.

  The total thickness of the first nickel layer and the second nickel layer is not particularly limited, but is preferably 1.5 μm or more and 17 μm or more, and particularly preferably 2.5 μm or more and 12 μm or more.

  The reflective metal layer constituting the ceramic package is located on the surface layer side of the second nickel layer, and the surface thereof can function as a light reflecting surface for reflecting the luminous flux from the light emitting element. Examples of suitable reflective metal layers include noble metal layers such as silver and gold, and platinum group layers such as platinum, palladium and rhodium. Among these, a silver layer having particularly high glossiness can be selected. desirable. The reflective metal layer may be formed directly on the second nickel layer, or may be indirectly formed through one or more metal layers made of a metal other than nickel. As a specific example of the latter, for example, a structure in which a thin gold layer is formed on the second nickel layer and a silver layer as a reflective metal layer is formed thereon can be exemplified.

  The ceramic package may further include a light emitting element mounted on the mounting portion, and a transparent resin filled in the cavity to cover the light emitting element. With this configuration, the light-emitting element mounted on the mounting portion is protected by being sealed with a transparent resin. Further, a transparent resin that can transmit light can be emitted outside the cavity without blocking the luminous flux from the light emitting element.

  As another means (means 2) for solving the above-mentioned problem, there is provided a substrate main surface and a cavity that opens on the substrate main surface, and a mounting portion on which the light emitting element can be mounted is provided on the inner surface of the cavity. A ceramic substrate, a metallized layer formed on the inner surface of the cavity, a first nickel layer formed on the metallized layer, a second nickel layer located on the surface layer side of the first nickel layer, A reflective metal layer that is located on the surface layer side of the second nickel layer and whose surface functions as a light reflecting surface that reflects the luminous flux from the light emitting element, and the second nickel layer substantially contains cobalt. There is a ceramic package for a light-emitting element, which is not contained in any of the above.

  Therefore, according to the package of means 2, the surface nickel plating layer substantially free of cobalt has higher surface smoothness than the base nickel layer. Therefore, the surface smoothness of the reflective metal layer formed on such a nickel layer as a base layer is also high, and the luminous flux from the light emitting element can be efficiently reflected.

  Further, as a method (means 3) suitable for manufacturing the ceramic package for the light-emitting element of means 1 or means 2, a preparation step of preparing a ceramic substrate having a metallized layer formed on the inner surface of the cavity, matte Performing a nickel plating to form a first nickel layer on the metallized layer, a heat treatment step for heating the metallization layer and the first nickel layer, and performing a bright nickel plating after the heat treatment step There is a method for manufacturing a ceramic package for a light emitting device, comprising: a second plating step for forming a second nickel layer; and a reflective metal layer forming step for forming a reflective metal layer after the second plating step.

  Therefore, according to the manufacturing method of the means 3, the first nickel layer can be adhered to the metallized layer by performing the heat treatment step after the first plating step. Further, by forming the second nickel layer after the heat treatment step, the thermal decomposition of the brightener is avoided, so that the second nickel layer having a smooth surface and high glossiness can be obtained with certainty. Therefore, if the reflective metal layer forming step is performed after the second plating step, a reflective metal layer having a smooth surface and a high glossiness can be formed relatively easily and reliably. In addition, since the formation of the first nickel layer and the second nickel layer is performed by a plating method that is an inexpensive method, an increase in manufacturing cost can be prevented.

  Hereinafter, the manufacturing method of the means 3 will be described.

  In the preparation step, a ceramic substrate having a metallized layer formed on the inner surface of the cavity is prepared.

  The ceramic substrate includes, for example, a step of producing a ceramic green sheet in which a portion to be a cavity is formed in advance, a step of disposing a metallized layer forming material on a portion to be an inner surface of the cavity, The ceramic green sheet and the metallized layer forming material can be simultaneously fired.

  Alternatively, the ceramic substrate includes a step of producing a ceramic green sheet in which a portion to be a cavity is formed in advance, a step of firing the ceramic green sheet to form a sintered body, and the cavity in the sintered body The metallized layer forming material can be manufactured through a step of disposing a metallized layer forming material on the inner surface of the metallized material and a step of sintering the metallized layer forming material.

  In this case, the ceramic green sheet is produced by forming a slurry obtained by mixing ceramic raw material powder, an organic binder, a solvent, a plasticizer, and the like into a sheet shape. The part to be the cavity (specifically, the through hole) is formed by, for example, a conventionally known punching process. As an example of a suitable method, first, a first ceramic green sheet and a second ceramic green sheet in which a through hole to be a part of a cavity later is formed by punching are prepared. Next, a metallized layer forming material is disposed on the inner peripheral surface of the through hole of the second ceramic green sheet. In this case, a suitable metallized layer forming material is a conductor paste made of a refractory metal powder, and the conductor paste is applied to the inner peripheral surface of the through hole by a conventionally known method. When it is necessary to form a metallized wiring layer or a via conductor, a conductor paste may be applied to the first ceramic green sheet. Next, after the first ceramic green sheet and the second ceramic green sheet are laminated and pressure-bonded to obtain a laminated body, the laminated body is heated to a firing temperature of the ceramic. As a result, a ceramic substrate having a cavity is obtained, and a metallized layer is formed by sintering the metallized layer forming material.

  In the subsequent first plating step, matte nickel plating is performed to form a first nickel layer on the metallized layer. As the matte nickel plating in this case, for example, electrolytic nickel plating using a nickel plating bath typified by a sulfamic acid bath is suitable. It is also possible to select electroless nickel plating using an electroless nickel plating bath typified by a nickel-boron bath. In addition, it is preferable that the brightener is not contained substantially in the plating bath used at a 1st plating process. The reason is as described above.

  In the subsequent heat treatment step, the metallized layer and the first nickel layer are heated to a temperature of, for example, 700 ° C. or higher and 900 ° C. or lower, and the first nickel layer is adhered to the metallized layer. In particular, the first nickel plating layer formed using a nickel plating bath containing cobalt has heat resistance that can withstand the heating temperature, and thus is preferable in terms of improving adhesion.

  Next, a brazing material layer forming step may be performed as necessary to form a brazing material layer on the first nickel layer. In this step, a brazing material is placed on the first nickel layer and heated to a temperature of about 700 ° C. to 900 ° C. to melt the brazing material to form a brazing material layer. The heating temperature in this case is preferably set to a temperature lower than the heat resistance temperature of the first nickel layer.

  In the second plating step, the second nickel layer is formed by performing bright nickel plating after the heat treatment step (or after the brazing material layer forming step). As the bright nickel plating in this case, for example, electrolytic nickel plating using a Watt bath-based bright nickel plating bath is suitable. The Watt bath is conventionally known as a highly practical nickel plating bath, and refers to a bath mainly composed of nickel sulfate, nickel chloride and boric acid. In addition, while it is preferable that the predetermined amount of brightener is contained in the plating bath used at a 2nd plating process, it is preferable that cobalt is not contained substantially. The reason is as described above.

  In the subsequent reflective metal layer forming step, the reflective metal layer is formed after the second plating step. The method for forming the reflective metal layer is not particularly limited, and a conventionally known method for forming a metal thin film can be employed. Specific examples thereof include a plating method, a sputtering method, and a CVD method. Among them, the plating method is preferable from the viewpoint of cost and the like.

  After the reflective metal layer forming step, an element mounting step for mounting a light emitting element on the mounting portion may be further performed. Further, after the element mounting process, a filling process may be further performed in which the cavity is filled with a transparent resin and the light emitting element is covered with the transparent resin.

[First Embodiment]

  Hereinafter, a ceramic package 10 for a light emitting device and a manufacturing method thereof according to an embodiment of the present invention will be described with reference to FIGS.

  As shown in FIG. 1, the ceramic package 10 for light emitting element of the present embodiment is a device for mounting an LED element 21 that is a light emitting element. The ceramic substrate 11 constituting the ceramic package 10 is a rectangular flat plate member having an upper surface 12 (substrate main surface) and a lower surface 13 as shown in FIG. The ceramic substrate 11 has a two-layer structure including an upper ceramic sintered layer 14 and a lower ceramic sintered layer 15. In the present embodiment, the upper ceramic sintered layer 14 and the lower ceramic sintered layer 15 are both made of an alumina sintered body.

  A bottomed cavity 31 having a size that can accommodate the LED element 21 is formed at the center of the upper surface 12 of the ceramic substrate 11. The cavity 31 has a circular shape in plan view, and the depth corresponds to the thickness of the upper ceramic sintered layer 14. In the central portion of the bottom surface 33 of the cavity 31, a conductor layer 34 as a mounting portion of the LED element 21 is formed in a rectangular shape by a nickel-silver plating layer on tungsten metallization. On the conductor layer 34, the LED element 21 is bonded using, for example, a thermosetting adhesive. In addition, since such a conductor layer 34 is not essential, you may join the LED element 21 directly to the center part of the bottom face 33 of the cavity 31. FIG. The cavity 31 is filled with a transparent resin 25 made of a thermosetting resin such as epoxy, and the LED element 21 is entirely covered with the transparent resin.

  As shown in FIGS. 1 and 2, a pair of bonding pads 35 are formed around the conductor layer 34 on the bottom surface 33. In the present embodiment, the bonding pad 35 has a structure in which a nickel-gold plating layer 39 is formed on a metallized layer 38 mainly composed of tungsten. A silver plating layer may be further formed on the nickel-gold plating layer 39. Bonding wires 22 that electrically connect the conductor on the LED element 21 side and the conductor on the ceramic substrate 11 side are joined on the bonding pads 35. Via holes 16 are formed at locations corresponding to the bonding pads 35 in the lower ceramic sintered layer 15, and via conductors 36 mainly composed of tungsten are provided in these via holes 16. A metallized wiring layer 37 mainly composed of tungsten is patterned on the lower surface 13 of the ceramic substrate 11, and the metallized wiring layer 37 is electrically connected to the lower end of the via conductor 36.

  As shown in FIG. 1, the side surface 32 of the cavity 31 is a surface having an inclination angle θ of about 45 ° with respect to the bottom surface 33. For this reason, the cavity 31 has a tapered shape whose diameter gradually increases from the bottom surface 33 toward the top surface 12. On the side surface 32 of the cavity 31, a metallized layer 42 having a thickness of about 10 μm to 30 μm mainly composed of tungsten is formed. As shown in detail in FIG. 3, a first nickel layer 43 is formed on the metallized layer 42, a second nickel layer 44 is further formed thereon, and a silver plating layer 45 is further formed thereon. Is formed. That is, in the present embodiment, the light reflecting portion 41 is configured by the metallized layer 42 mainly composed of tungsten, the first nickel layer 43, the second nickel layer 44, and the silver plating layer 45, and the silver plating layer 45 located at the outermost layer is formed. The surface functions as a light reflecting surface.

  In the present embodiment, the first nickel layer 43 is a nickel plating layer that does not substantially contain a brightener, and the thickness thereof is set to about 1.0 μm. On the other hand, the second nickel layer 44 is a nickel plating layer containing a brightener or a decomposition product thereof, and the thickness thereof is set to about 3 μm thicker than the first nickel layer 43. Here, the cobalt content in the 1st nickel layer 43 and the 2nd nickel layer 44 is very low, and has become below a detection limit (here 0.001 weight% or less).

  In such a ceramic package 10, the luminous flux of the LED element 21 is reflected on the surface of the silver plating layer 45 in the thickness direction of the ceramic substrate 11 (upward in FIG. 1).

  Next, a method for manufacturing the ceramic package 10 having the above structure will be described.

  First, a slurry is prepared by mixing alumina powder, an organic binder, a solvent, a plasticizer and the like. And this slurry is shape | molded by the conventionally well-known method (For example, a doctor blade method or a calender roll method), and two ceramic green sheets are produced. Next, drilling of these ceramic green sheets is performed as follows. As shown in FIG. 4, one of the two sheets (upper ceramic green sheet 64) is punched using a conventionally known punching die (not shown) to form a through hole 66. . Since this through hole 66 will later become a part of the cavity 31, it is formed in a tapered shape. On the other hand, the via hole 16 penetrating the front and back surfaces of the sheet is formed on the other of the two sheets (the lower ceramic green sheet 65) by a conventionally known punching process. The via hole 16 can also be formed by a technique such as laser processing or drilling.

  Next, a tungsten paste 71, which is a metallized layer forming material, is applied to the inner peripheral surface of the through hole 66 of the upper ceramic green sheet 64 using a conventionally known paste printing apparatus. Further, using the same apparatus, the tungsten paste 71 is applied to predetermined locations on the front and back surfaces of the lower ceramic green sheet 65 and filled into the via holes 16 (see FIG. 5).

  Next, the upper ceramic green sheet 64 is laminated on the lower ceramic green sheet 65, and a predetermined load is applied in the thickness direction using a conventionally known laminating apparatus, so that these are bonded and integrated to form a laminated body. (See FIG. 6). Then, the baking process which heats this laminated body to the predetermined | prescribed temperature (for example, temperature of about 1500 degreeC-1700 degreeC) which an alumina can sinter is performed. When this firing is performed, as shown in FIG. 7, the lower ceramic green sheet 65 and the upper ceramic green sheet 64 are sintered, and the ceramic substrate 11 having the cavity 31 is obtained. Further, by sintering the tungsten paste 71, a metallized layer 42 that forms a part of the light reflecting portion 41 is formed on the side surface 32 of the cavity 31. Via conductors 36, metallized wiring layers 37, and metallized layers 38 that form part of the bonding pads 35 are respectively formed at predetermined locations on the ceramic substrate 11.

  Next, matte nickel plating is performed in the first plating step to form the first nickel layer 43 on the metallized layer 38 (see FIG. 8). In this embodiment, a conventionally well-known sulfamic acid bath is selected as the nickel plating bath, and electrolytic nickel plating is performed using the well-known conditions. The sulfamic acid bath does not contain a brightener. The first nickel layer 43 formed through the first plating step has a surface roughness Ra measured by a stylus method of less than 0.5 μm, and the average grain size of nickel crystal grains is about 3.0 μm. Yes. That is, the surface roughness (Ra = 0.475 μm: measured value by the stylus method) of the first nickel layer 43 is as rough as the surface roughness (Ra = 1.120 μm: measured value by the stylus method) of the metallized layer 42. None (see Table 1 in FIG. 12). However, since the gloss level (BLK value) of the first nickel layer 43 is 0.266, it can be said that the first nickel layer 43 does not have such a high gloss level (see Table 2 in FIG. 13).

The measurement of glossiness (BLK value) was performed using a measuring apparatus shown in FIG. This measuring apparatus includes light sources 91 at two locations (two locations obliquely above the measurement target 93 in FIG. 11) that form an angle of 45 ° with the measurement target surface of the measurement target 93. The tip of each light source 91 is aimed at the surface to be measured of the measuring object 93. On the other hand, this measuring apparatus includes a light receiving means 92 at a position of 90 ° with respect to the measurement target surface of the measuring object 93 (a position directly above the measuring object 93 in FIG. 11). The light receiving portion of the light receiving means 92 is disposed to face the surface to be measured of the measurement object 93. In the measurement using the measuring apparatus, first, the two light sources 9 1 applying light to the measurement surface of the measurement object 93 to emit light at a predetermined intensity. Then, the reflected light of the incident light was received by the light receiving means 92 and the intensity of the reflected light was obtained. Next, a value obtained by subtracting the logarithm of the reflected light intensity with respect to the incident light intensity from 2 was calculated, and this calculated value was defined as the glossiness (BLK value).

  In the subsequent heat treatment step, the ceramic substrate 11 in which the first nickel layer 43 is formed on the metallized layer 42 is heated to a temperature of about 850 ° C. in a reducing atmosphere using a conventionally known heating device. Then, the first nickel layer 43 was securely adhered to the metallized layer 42 by this heating.

  In the subsequent second plating step, bright nickel plating is performed to form the second nickel layer 44 on the first nickel layer 43 (see FIG. 9). In the bright nickel plating in this case, electrolytic nickel plating was performed using a bright nickel plating bath based on a watt bath mainly composed of nickel sulfate, nickel chloride and boric acid, and a predetermined brightener added thereto. . The “bright nickel plating bath A” and “bright nickel plating bath B” shown in Tables 1 and 2 mean that they are different products. These plating baths contain at least 0.1% by weight or more of brightener, but are substantially free of cobalt.

  When the second nickel layer 44 formed through the second plating step was measured by the stylus method, the surface roughness Ra was 0.193 μm for the one formed by “bright nickel plating A” and “bright nickel plating B”. The surface roughness Ra was 0.322 μm (see Table 1 in FIG. 12). The average grain size of the nickel crystal grains constituting the second nickel layer 44 was smaller than the average grain size of the nickel crystal grains constituting the first nickel layer 43, and was about 0.3 μm. Incidentally, in the second nickel layer formed by matte nickel plating, the surface roughness Ra was 0.472 μm.

  Further, when the second nickel layer 44 was measured by the measuring device of FIG. 11, the glossiness (BLK value) formed by “bright nickel plating A” was 2.336, and “bright nickel plating B” was formed. The glossiness (BLK value) was 1.921 (see Table 2 in FIG. 13). Incidentally, the second nickel layer formed by matte nickel plating had a glossiness (BLK value) of 0.303, which was inferior to the above.

  In the subsequent reflective metal layer forming step, electrolytic silver plating is performed to form a silver plating layer 45 that is a reflective metal layer, thereby completing the light reflecting portion 41 (see FIG. 10).

  The nickel-gold plating layer 39 on the metallized layer 38 forming a part of the bonding pad 35 is formed by performing electrolytic nickel plating and electrolytic gold plating after the first plating step and the second plating step. Is possible. Alternatively, the gold plating layer can be formed by forming a nickel layer on the metallized layer 38 by the first plating step and the second plating step and performing electrolytic gold plating on the nickel layer.

  About the ceramic package 10 for light emitting elements obtained as mentioned above, an element mounting process is further performed after this, and mounting of LED element 21 and wire bonding are implemented. Next, a ceramic package with a light emitting element is completed by performing a filling process, filling the cavity 31 with the transparent resin 25 and thermally curing the resin.

Therefore, according to the present embodiment, the following effects can be obtained.
(1) In the case of the ceramic package for light emitting element 10, the first nickel layer 43 is formed on the metallized layer 42, and the second nickel layer 44 is formed on the first nickel layer 43. And the 1st nickel layer 43 is a nickel plating layer which does not contain a brightener substantially. The second nickel layer 44 is a nickel plating layer containing a brightener, but does not contain cobalt.

  Since the 1st nickel layer 43 is a nickel plating layer which does not contain a brightener substantially, the adhesiveness with respect to the metallizing layer 42 is originally high compared with the same nickel plating layer containing a brightener. In addition, the nickel plating layer (second nickel layer 44) containing the brightener has fine crystal grains and has high surface smoothness. Therefore, the surface smoothness of the silver plating layer 45 formed on the second nickel layer 44 as a base layer is also increased. Therefore, it is possible to obtain a light reflecting surface that can efficiently reflect the luminous flux from the LED element 21.

  From the above, it is possible to realize the light emitting element ceramic package 10 provided with a high-quality light reflecting surface that can efficiently reflect the luminous flux from the LED element 21.

  (2) In the case of the light emitting element ceramic package 10 of the present embodiment, not only the adhesion between the metallized layer 42 and the first nickel layer 43 but also the adhesion between the first nickel layer 43 and the second nickel layer 44, the first The adhesion between the 2 nickel layer 44 and the silver plating layer 45 is also excellent. Therefore, even if a structure in which the cavity 31 is sealed with the transparent resin 25 is employed, it is possible to prevent “breaking” in the light reflecting portion 41 during the filling process. Therefore, the ceramic package 10 for light emitting elements excellent in reliability can be realized.

(3) In the manufacturing method of the present embodiment, the first plating step for forming the first nickel layer 43 by performing matte nickel plating, the heat treatment step, and the second for forming the second nickel layer 44 by performing bright nickel plating. The plating process and the reflective metal layer forming process for forming the silver plating layer 45 are performed in this order. Then, the first nickel layer 43 can be adhered to the metallized layer 42 by performing a heat treatment step after the first plating step. Further, by forming the second nickel layer 44 after the heat treatment step, it is possible to reliably obtain the second nickel layer 44 having a smooth surface and high gloss as a result of avoiding thermal decomposition of the brightener. Therefore, if the reflective metal layer forming step is performed after the second plating step, the silver plating layer 45 (reflective metal layer) having a smooth surface and high gloss can be formed relatively easily and reliably. In addition, since the first nickel layer 43 and the second nickel layer 44 are formed by a plating method which is an inexpensive method, an increase in manufacturing cost can be prevented.
[Second Embodiment]

  Hereinafter, another embodiment of the ceramic package 110 for a light emitting device embodying the present invention will be described with reference to FIG. Here, differences from the first embodiment will be described, and description of common points will be omitted.

As shown in FIG. 14, in this embodiment, the structure of the light reflecting portion 41 is slightly different from that of the first embodiment, and the gold plating layer 46 is interposed between the second nickel layer 44 and the silver plating layer 45. Is intervened. The gold plating layer 46 is a thin plating layer formed by so-called electrolytic strike gold plating. The thickness of the gold plating layer 46 is arbitrary, but if it exceeds 0.2 μm, for example, gold plating precipitates are likely to be generated, and the surface may become rough. Therefore, the thickness of the gold plating layer 46 is preferably 0.2 μm or less, and more preferably 0.03 μm or more and 0.2 μm or less. In addition to strike gold plating, strike silver plating or strike palladium plating may be used.

According to this embodiment having such a structure, as in the first embodiment, the adhesion between the metallized layer 42 and the first nickel layer 43 is excellent, and the luminous flux from the LED element 21 is efficiently reflected. A ceramic package 110 for a light emitting element having a good light reflecting surface can be realized. Further, by interposing the gold plating layer 46 by electrolytic strike gold plating between the second nickel layer 44 and the silver plating layer 45, the adhesion between both layers can be further improved.
[Third Embodiment]

  Hereinafter, a ceramic package 210 for a light emitting device according to an embodiment of the present invention will be described with reference to FIG. Here, differences from the first embodiment will be described, and description of common points will be omitted.

  As shown in FIG. 15, in this embodiment, the cross-sectional shape of the cavity 31 is different from that of the first embodiment. That is, here, the side surface 32 of the cavity 31 is a vertical surface that forms an angle of 90 ° with respect to the bottom surface 33 of the cavity 31. A metallized layer 42 is formed on the outer peripheral portions of the side surface 32 and the bottom surface 33, and a first nickel layer 43 is formed thereon. On the first nickel layer 43, a silver brazing layer 47 as a brazing material layer is formed. The silver brazing layer 47 has a so-called fillet shape, and the surface thereof is an inclined surface having an angle of 40 ° to 50 ° with respect to the bottom surface 33. A second nickel layer 44 is formed on the inclined surface of the silver brazing layer 47, a thin gold plating layer 46 is formed thereon, and a silver plating layer 45 is further formed thereon.

And according to this embodiment of such a structure, it is excellent in the adhesiveness of the metallization layer 42 and the 1st nickel layer 43 similarly to 1st Embodiment, and reflects the emitted light beam from LED element 21 efficiently. A ceramic package 210 for a light emitting element having a good light reflecting surface can be realized. Further, by interposing the gold plating layer 46 by electrolytic strike plating between the second nickel layer 44 and the silver plating layer 45, the adhesion between both layers can be further improved. Furthermore, since the fillet-like silver brazing layer 47 is formed to obtain the inclined surface, the upper ceramic green sheet 64 can be easily punched, and the ceramic package 210 for a light emitting element that can be easily manufactured can be obtained. In addition, since the first nickel layer 43 substantially free of cobalt has good wettability with respect to silver brazing, high adhesion can be ensured with the silver brazing layer 47.

  In addition, you may change embodiment of this invention as follows. For example, in the above embodiment, the structure in which one LED element 21 is mounted in the cavity 31 is illustrated, but the number may be two or more. As a specific example, an elliptical cavity 31 is formed in plan view, and three conductor layers 34 are formed at a substantially central portion of the bottom surface 33 of the cavity 31. The red, green, and blue LED elements 21 are mounted on the three conductor layers 34, respectively. If comprised in this way, the apparatus which can obtain high-intensity white light is realizable.

  Next, the technical ideas grasped by the embodiment described above are listed below.

  (1) A ceramic substrate having a substrate main surface and a cavity that opens at the substrate main surface, and a mounting portion capable of mounting a light emitting element on the inner surface of the cavity, and the inner surface of the cavity. A metallized layer, a first nickel layer formed on the metallized layer, a second nickel layer located on the surface layer side of the first nickel layer, and located on the surface layer side of the second nickel layer, A reflective metal layer capable of functioning as a light reflecting surface for reflecting the luminous flux from the light emitting element, the second nickel layer is a bright nickel plating layer, and the first nickel layer is a matte nickel plating layer A ceramic package for a light-emitting element, characterized in that

  (2) A ceramic substrate having a substrate main surface and a cavity that opens at the substrate main surface, and a mounting portion capable of mounting a light emitting element on the inner surface of the cavity, and the inner surface of the cavity. A metallized layer, a first nickel layer formed on the metallized layer, a second nickel layer formed on the first nickel layer, and a surface of the light emitting element formed on the second nickel layer A reflective metal layer that can function as a light reflecting surface that reflects the luminous flux from the first nickel layer, the second nickel layer is a nickel plating layer containing a brightener, and the first nickel layer substantially contains the brightener. A ceramic package for a light-emitting element, characterized by being a nickel plating layer that does not contain.

  (3) A ceramic substrate having a substrate main surface and a cavity that opens at the substrate main surface, and a mounting portion capable of mounting a light emitting element on the inner surface of the cavity, and the inner surface of the cavity. A metallized layer; a first nickel layer formed on the metallized layer; a second nickel layer formed on the first nickel layer; a gold layer formed on the second nickel layer; and the gold A nickel layer having a silver layer as a reflective metal layer, the surface of which is formed on a layer and whose surface functions as a light reflecting surface that reflects the luminous flux from the light emitting element, and wherein the second nickel layer contains a brightener A ceramic package for a light emitting device, wherein the first nickel layer is a nickel plating layer that does not substantially contain a brightener.

  (4) A ceramic substrate having a substrate main surface and a cavity that opens at the substrate main surface, and a mounting portion capable of mounting a light emitting element on the inner surface of the cavity; A metallized layer formed thereon, a first nickel layer formed on the metallized layer, a fillet-like brazing material layer formed on the first nickel layer, and formed on the brazing material layer A second nickel layer, and a reflective metal layer formed on the second nickel layer, the surface of which can function as a light reflecting surface that reflects the luminous flux from the light emitting element, and the second nickel layer is glossy A ceramic package for a light-emitting element, wherein the first nickel layer is a nickel plating layer containing substantially no brightener.

  (5) A ceramic substrate having a substrate main surface and a cavity that opens at the substrate main surface, and a mounting portion capable of mounting a light emitting element on the inner surface of the cavity, and the inner surface of the cavity. A metallized layer, a first nickel layer formed on the metallized layer, a second nickel layer located on the surface layer side of the first nickel layer, and located on the surface layer side of the second nickel layer, A reflective metal layer having a surface that can function as a light reflecting surface that reflects the luminous flux emitted from the light emitting element, and the second nickel layer contains a brightener and a nickel plating layer substantially free of cobalt. A ceramic package for a light emitting device, wherein the ceramic package is a nickel plating layer substantially free of a brightener.

  (6) A ceramic substrate having a substrate main surface and a cavity that opens at the substrate main surface, and provided with a mounting portion capable of mounting a light emitting element on the inner surface of the cavity, and formed on the inner surface of the cavity A metallized layer, a first nickel layer formed on the metallized layer, a second nickel layer located on the surface layer side of the first nickel layer, and located on the surface layer side of the second nickel layer, A reflective metal layer whose surface can function as a light reflecting surface for reflecting the luminous flux from the light emitting element, wherein the glossiness of the second nickel layer is greater than the glossiness of the first nickel layer Ceramic package for light emitting devices.

  (7) A ceramic substrate having a substrate main surface and a cavity that opens at the substrate main surface, and a mounting portion capable of mounting a light emitting element on the inner surface of the cavity, and the inner surface of the cavity. A metallized layer, a first nickel layer formed on the metallized layer, a second nickel layer located on the surface layer side of the first nickel layer, and located on the surface layer side of the second nickel layer, A nickel metal grain constituting the first nickel layer, wherein the nickel crystal grains constituting the second nickel layer comprise a reflective metal layer capable of functioning as a light reflecting surface for reflecting the luminous flux from the light emitting element. A ceramic package for light-emitting elements characterized by being finer.

  (8) A ceramic substrate having a substrate main surface and a cavity that opens at the substrate main surface, and a mounting portion on which the light emitting element can be mounted on the inner surface of the cavity, and the inner surface of the cavity. A metallized layer, a first nickel layer formed on the metallized layer, a second nickel layer located on the surface layer side of the first nickel layer, and located on the surface layer side of the second nickel layer, A reflective metal layer whose surface can function as a light reflecting surface for reflecting the luminous flux from the light emitting element, the surface roughness Ra of the first nickel layer is smaller than the surface roughness Ra of the metallized layer, 2. A ceramic package for a light emitting device, wherein the surface roughness Ra of the second nickel layer is smaller than the surface roughness Ra of the first nickel layer.

  (9) In any one of the above (1) to (8), the nickel crystal grains constituting the second nickel layer have an average grain size of 1.0 μm or less, and the nickel constituting the first nickel layer A ceramic package for a light-emitting element, wherein an average grain size of crystal grains is larger than 1.0 μm and not larger than 3.0 μm.

  (10) In any one of the above (1) to (8), the metallized layer has a surface roughness Ra of 1.0 μm or more, and the first nickel layer has a surface roughness Ra of 0.4 μm or more. A ceramic package for a light emitting device, wherein the second nickel layer has a surface roughness Ra of not less than 0.1 μm and less than 0.4 μm.

  (11) The ceramic package for a light emitting element according to any one of (1) to (8), wherein the reflective metal layer is a silver plating layer.

  (12) In any one of the above items (1) to (8), the light emitting device mounted on the mounting portion and the transparent resin filled in the cavity to cover the light emitting device are provided. A ceramic package for light emitting devices.

1 is a schematic sectional view showing a ceramic package for a light emitting device according to a first embodiment embodying the present invention. The schematic plan view which shows the same ceramic package. The schematic sectional drawing which shows the principal part of the ceramic package. Process drawing for demonstrating the manufacturing method of the ceramic package. Process drawing for demonstrating the manufacturing method of the ceramic package. Process drawing for demonstrating the manufacturing method of the ceramic package. Process drawing for demonstrating the manufacturing method of the ceramic package. Process drawing for demonstrating the manufacturing method of the ceramic package. Process drawing for demonstrating the manufacturing method of the ceramic package. Process drawing for demonstrating the manufacturing method of the ceramic package. Schematic for demonstrating the measuring method of glossiness. The table | surface which shows the comparison result of surface roughness Ra. The table | surface which shows the comparison result of glossiness. The schematic sectional drawing which shows the principal part of the ceramic package of 2nd Embodiment. The schematic sectional drawing which shows the principal part of the ceramic package of 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,110,210 ... Ceramic package for light emitting elements 11 ... Ceramic substrate 12 ... Upper surface as substrate main surface 21 ... LED element as light emitting element 31 ... Cavity 34 ... Conductor layer as mounting part 41 ... Light reflecting part 42 ... Metallization Layer 43 ... 1st nickel layer 44 ... 2nd nickel layer 45 ... Silver plating layer as reflective metal layer 46 ... Gold plating layer 47 ... Silver brazing layer as brazing material layer

Claims (7)

A ceramic substrate having a substrate main surface and a cavity opened at the substrate main surface, and a mounting portion capable of mounting a light emitting element on the inner surface of the cavity;
A metallization layer formed on the inner surface of the cavity;
A first nickel layer formed on the metallized layer;
A second nickel layer located on the surface side of the first nickel layer;
A reflective metal layer located on the surface layer side of the second nickel layer, the surface of which can function as a light reflecting surface that reflects the luminous flux from the light emitting element ;
A strike plating layer interposed between the second nickel layer and the reflective metal layer ;
The second nickel layer is a nickel plating layer containing a brightening agent, the first layer of nickel Ri nickel plating layer der substantially free of brightener,
The thickness of the first nickel layer is 0.5 μm to 2 μm, the thickness of the second nickel layer is 2 μm to 10 μm, and the thickness of the strike plating layer is 0.03 μm to 0.2 μm. ceramic package for a light emitting element characterized <br/> that is.   2. The ceramic package for a light emitting device according to claim 1, wherein the glossiness of the second nickel layer is greater than the glossiness of the first nickel layer.   Light is incident from two locations that form an angle of 45 ° with respect to the surface to be measured of the measurement object, and reflected light of the incident light is received at a position of 90 ° with respect to the surface to be measured. When the value obtained by subtracting the logarithm of the reflected light intensity from 2 is defined as the glossiness, the glossiness of the second nickel layer is 1.0 or more and 2.5 or less, and the glossiness of the first nickel layer is 0. The ceramic package for a light emitting device according to claim 1 or 2, wherein the ceramic package is 1 or more and 0.8 or less.   4. The ceramic package for a light emitting device according to claim 1, wherein the second nickel layer does not substantially contain cobalt. 5.   5. The ceramic package for a light-emitting element according to claim 1, further comprising a brazing material layer between the first nickel layer and the second nickel layer. 6. The ceramic package for a light emitting device according to claim 1, wherein nickel crystal grains constituting the second nickel layer are finer than nickel crystal grains constituting the first nickel layer. . It is a manufacturing method of the ceramic package for light emitting elements of any one of Claims 1 thru | or 6, Comprising:
Preparing a ceramic substrate having a metallized layer formed on the inner surface of the cavity;
Performing a matte nickel plating to form a first nickel layer on the metallized layer;
A heat treatment step for heating the metallized layer and the first nickel layer;
A second plating step of forming a second nickel layer by performing bright nickel plating after the heat treatment step;
A method of manufacturing a ceramic package for a light emitting device, comprising: a reflective metal layer forming step of forming a reflective metal layer after the second plating step.

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