JP2006351568A - Method of manufacturing light emitting device mounting package - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a silver-plated layer surface serving as a light reflecting surface from discoloring for a long term in a manufacturing method of a light emitting device mounting package. <P>SOLUTION: After a silver-plated layer 20 is formed on a peripheral face of a cavity 13 of a package body 11, a light emitting device 12 is mounted on a device mounting region 24 in the cavity 13 via a sheetlike preform 23, and the light emitting device 12 is soldered onto the device mounting region 24. Thereafter, an electrode of the device 12 and the pad 15 are connected via a bonding wire 14. Then, the package body 11 (at least an entire surface of the silver-plated layer 20) is soaked in a solution of a silver discoloration inhibitor to form a silver discoloration preventive coat 21 on the surface of the layer 20. Thereafter, the package body 11 is taken out from the solution of the inhibitor, washed in water and dried. Thus, the entire surface of the silver-plated layer 20 to serve as the light reflecting surface 22 is coated with the transparent and thin silver discoloration preventive coat 21. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a light emitting element mounting package in which a light reflecting surface for reflecting light of the light emitting element is formed on an inner surface of a cavity for mounting the light emitting element.

  For example, in the light emitting element mounting package described in Patent Document 1 (Japanese Patent Laid-Open No. 2004-207672), the light emitting element 3 is mounted in the cavity 2 formed on the upper surface side of the alumina substrate 1 as shown in FIG. The light reflecting surface 4 that reflects the light of the light emitting element 3 is formed on the peripheral side surface of the cavity 2. In this case, a base metallized layer 5 containing tungsten and molybdenum is co-fired on the light reflecting surface 4 together with the alumina substrate 1, and a silver plated layer 7 is formed on the base metallized layer 5 via a nickel plated layer 6, The surface of the silver plating layer 7 is used as the light reflecting surface 4. Here, the reason why the silver plating layer 7 is used as the light reflecting surface 4 is that the metal color is white and the light color does not change between the incident light and the reflected light (see paragraph [0032]). ).

In this light emitting element mounting package, the cavity 2 in which the light emitting element 3 is mounted is filled with a transparent resin so as to seal the light emitting element 3 and the silver plating layer 7 (see paragraph [0040]).
JP-A-2004-207672 (first page, sixth page, etc.)

  As described above, the silver plating layer 7 to be the light reflecting surface 4 is sealed with the transparent resin together with the light emitting element 3, but the surface of the silver plating layer 7 has a tendency to discolor due to secular change. The discoloration of the surface of the silver plating layer 7 is considered to be caused by various phenomena such as a sulfidation phenomenon, an oxidation phenomenon, and a chlorination phenomenon. The main cause is considered to be a sulfidation phenomenon. Originally, if the sealing of the silver plating layer 7 with a transparent resin is perfect, the sulfidation phenomenon on the surface of the silver plating layer 7 should not occur, but the sealing resin has some gas permeability, It is presumed that the surface of the silver plating layer 7 is sulfurized by the sulfur component in the gas that permeates the sealing resin, or the surface of the silver plating layer 7 is sulfurized by the sulfur component contained in the sealing resin. When the surface of the silver plating layer 7 changes color due to this sulfurization phenomenon, there arises a problem that the light reflectance (glossiness) is lowered.

  In order to solve this problem, the present applicant recently developed a technique for preventing silver discoloration treatment with a silver discoloration preventing agent on the light reflection surface on the side surface of the cavity, as shown in the application specification of Japanese Patent Application No. 2005-121068. I am researching, but in the course of this research, I found the following new problems.

  When a silver discoloration prevention treatment process is added to the manufacturing process of the light emitting element mounting package, the light on the cavity inner surface of the package body (alumina substrate 1 in Patent Document 1) after the completion of the silver plating process, as in the comparative example shown in FIG. It is conceivable that the light-emitting element is mounted in the cavity of the package body after the surface of the silver plating layer serving as the reflective surface is subjected to silver discoloration prevention treatment with a silver discoloration inhibitor. At this time, the mounting of the light emitting element is sometimes performed without applying heat using an adhesive, but is more often performed by applying heat of about 230 ° C. with solder or the like. Accordingly, when the surface of the silver plating layer is subjected to silver discoloration prevention treatment with a silver discoloration preventing agent before mounting the light emitting element, the light emitting element is then mounted by applying heat of about 230 ° C. with solder or the like. It was found that the silver discoloration prevention treatment film on the surface of the plating layer was almost burned down by the heat during mounting, and the silver discoloration prevention effect was almost lost.

  The present invention has been made in view of such circumstances, and therefore the object of the present invention is to manufacture a light emitting element mounting package capable of preventing discoloration of the surface of the silver plating layer serving as a light reflecting surface over a long period of time. It is to provide a method.

  In order to achieve the above object, a method of manufacturing a light emitting element mounting package according to the present invention includes: a silver plating step of forming a silver plating layer on at least a portion of a cavity inner surface of a package body where a light reflecting surface is formed; An element mounting step of mounting a light emitting element in the cavity of the main body, and a silver discoloration prevention processing step of performing silver discoloration prevention treatment on the surface of the silver plating layer which becomes the light reflecting surface after mounting of the light emitting element with a silver discoloration inhibitor; It is characterized by including. In this manufacturing method, since the surface of the silver plating layer is subjected to silver discoloration prevention treatment with a silver discoloration preventing agent after the light emitting element is mounted, the surface of the silver plating layer is used even when the light emitting element is mounted at a temperature of about 230 ° C. The silver discoloration prevention coating film of the silver plating layer surface that can maintain the silver discoloration prevention effect by the silver discoloration prevention treatment for a long period of time and can be used for a long time without being damaged by heat during mounting. Can be prevented over a long period of time.

  Furthermore, in the silver discoloration preventing treatment step, the present invention is to immerse at least the surface of the silver plating layer serving as the light reflecting surface of the package body on which the light emitting element is mounted in a silver discoloration preventing agent solution. Thus, the surface of the silver plating layer is preferably subjected to a silver discoloration prevention treatment. In this way, the surface of the silver plating layer can be efficiently processed to prevent silver discoloration by a very simple method of immersion, and the requirements for productivity and cost can be satisfied.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration example of a light emitting element mounting package in which only one cavity 13 for mounting the light emitting element 12 is formed in the package body 11. It goes without saying that a plurality of cavities 13 for mounting the light emitting elements 12 may be formed in the package body 11.

  The package body 11 is constituted by a multilayer ceramic substrate in which, for example, a plurality of ceramic layers 11a to 11c (ceramic green sheets) are laminated and fired and integrated, and a cavity 13 is formed by a through hole formed in the uppermost ceramic layer 11a. Has been. Each of the ceramic layers 11a to 11c is formed of a high-temperature fired ceramic such as alumina or aluminum nitride that is fired at 1000 ° C. or higher, and the peripheral side surface of the cavity 13 reflects the light of the light emitting element 12 toward the outside. Is formed in a tapered surface shape that expands outward.

  Formed on the bottom surface of the cavity 13 are an element mounting portion 24 for mounting the light emitting element 12 with a solder preform 23 and a pad 15 for connecting the electrode of the light emitting element 12 with a bonding wire 14. Vias 16 and wiring patterns 17 that electrically connect the layers are printed and fired on the ceramic layers 11b and 11c with a refractory metal conductor paste such as tungsten or molybdenum.

  A base metallized layer 18 made of a refractory metal such as tungsten or molybdenum is simultaneously fired on the peripheral side surface of the cavity 13 together with the package body 11, and a base nickel plating layer 19 is formed on the base metallized layer 18. A silver plating layer 20 is formed on the nickel plating layer 19, and the surface of the silver plating layer 20 is a light reflecting surface 22. In this case, the base metal layer has a two-layer structure of the base metallized layer 18 and the base nickel plated layer 19, but the base nickel plated layer 19 is omitted and the silver plated layer 20 is directly formed on the base metallized layer 18. You may make it form.

  In this case, the thickness of the underlying nickel plating layer 19 is desirably 1 to 8 μm in order to ensure the bonding strength with the silver plating layer 20. Further, if the thickness of the silver plating layer 20 is too thin, the underlying nickel penetrates the surface of the silver plating layer 20 and the surface of the silver plating layer 20 (light reflection surface 22) is discolored. It is desirable to be 2.5 μm or more. Further, the silver plating layer 20 may be formed by bright silver plating to which a brightening agent is added. Similarly, the base nickel plating layer 19 may be formed by bright nickel plating.

  Further, on the silver plating layer 20, a silver discoloration prevention treatment film 21 (organic film) with a silver discoloration preventing agent is formed after the light emitting element 12 is mounted, and the entire surface of the silver plating layer 20 serving as the light reflection surface 22 is transparent. The thin silver discoloration prevention coating 21 is applied. As the silver discoloration preventing agent for forming the silver discoloration preventing treatment film 21, for example, any one of organic silver discoloration preventing agents such as water-based, solvent-based, isopropyl alcohol, and aliphatic organic compound may be used.

  When manufacturing the light emitting element mounting package configured as described above, the ceramic layers 11a to 11c (ceramic green sheets) before firing are respectively provided with the base metallized layer 18, the via 16, the wiring pattern 17, the element mounting portion 24, After printing any one of the pads 15 with a conductive paste of a refractory metal such as tungsten or molybdenum, the ceramic layers 11a to 11c are laminated and pressure-bonded to be integrated and fired at the sintering temperature of the high-temperature fired ceramic. As a result, the package body 11 and the refractory metal (the base metallized layer 18, the via 16, the wiring pattern 17, the element mounting portion 24, and the pad 15) are simultaneously fired.

  Thereafter, the process proceeds to a nickel plating step, and a base nickel plating layer 19 is formed on the base metallization layer 18 on the peripheral side surface of the cavity 13 by electrolytic plating or electroless plating using a nickel plating solution.

  Thereafter, the process proceeds to a silver plating step, and a silver plating layer 20 having a thickness of, for example, 2.5 μm or more is formed on the underlying nickel plating layer 19 on the peripheral side surface of the cavity 13 by an electrolytic plating method or an electroless plating method using a silver plating solution. Form. The surface of the silver plating layer 20 becomes the light reflecting surface 22.

  After completion of this silver plating process, the process proceeds to an element mounting process. As shown in FIGS. 2 (a) and 2 (b), a light emitting element having a sheet-like solder preform 23 sandwiched between the element mounting portion 24 in the cavity 13 is provided. In this state, heat of about 230 ° C. is applied to melt the solder preform 23, and the light emitting element 12 is soldered onto the element mounting portion 24. Thereafter, as shown in FIG. 2C, the electrode of the light emitting element 12 and the pad 15 are connected by the bonding wire 14.

  After the element mounting process, the process proceeds to a silver discoloration prevention treatment process, and the package body 11 (at least the entire surface of the silver plating layer 20) is immersed in a silver discoloration inhibitor solution for a short time (for example, about 30 seconds to 1 minute). After forming the silver discoloration prevention treatment film 21 (organic film) on the surface of the silver plating layer 20, the package body 11 is taken out from the solution of the silver discoloration prevention agent, washed with water and dried. As a result, the entire surface of the silver plating layer 20 to be the light reflecting surface 22 is covered with the transparent thin silver discoloration prevention coating 21.

  Thereafter, the light emitting element 12 and the light reflection surface 22 may be sealed by filling the cavity 13 of the package body 11 with a transparent resin.

  As described above, in the conventional structure, the surface of the silver plating layer serving as the light reflecting surface is not covered with the silver discoloration prevention coating film, so the surface of the silver plating layer is discolored due to a sulfurization phenomenon or the like as the service period increases. It is inevitable that the light reflectance (glossiness) is lowered.

  In contrast, in this embodiment, after the light emitting element 12 is mounted in the cavity 13 of the package body 11, the surface of the silver plating layer 20 that becomes the light reflecting surface 22 is subjected to silver discoloration prevention treatment with a silver discoloration inhibitor. Therefore, the surface of the silver plating layer 20 can be covered with the silver discoloration prevention treatment film 21. Thereby, the surface of the silver plating layer 20 can be shielded from the discoloration environment (sulfur component) by the silver discoloration prevention treatment coating 21, and the discoloration of the surface of the silver plating layer 20 can be prevented over a long period of time.

  The inventor produces a sample of a light emitting element mounting package by the manufacturing method of the above-described embodiment (see FIG. 3), and the type of silver discoloration preventing agent that forms the silver discoloration prevention treatment film 21 and the surface of the silver plating layer 20. Since the test which considers the relationship with the discoloration prevention effect of was performed, the test result is demonstrated.

  In the example sample used in this test, the package body 11 is formed of aluminum nitride, the base metallized layer 18 is formed by printing and co-firing tungsten paste, and the base nickel plated layer 19 is formed on the base metallized layer 18. After forming the silver plating layer 20, the light emitting device 12 is mounted in the cavity 13 of the package body 11 by heating at about 230 ° C. using the solder preform 23, and then the water-soluble elements shown in Table 1 below are mounted. A silver discoloration prevention coating film 21 is formed on the surface of the silver plating layer 20 by using a silver discoloration preventive agent based on isopropyl alcohol, aliphatic organic compound or solvent.

  The silver discoloration prevention treatment film 21 was formed by immersing the example sample in the silver discoloration inhibitor solution shown in Table 1 below for 1 minute to form the silver discoloration prevention treatment film 21 on the surface of the silver plating layer 20. Thereafter, the example sample is taken out of the silver discoloration inhibitor solution, washed with water for 1 minute, air blown to blow off water droplets attached to the example sample, and then dried with warm air. For comparison, a sample corresponding to a conventional example without the silver discoloration prevention coating 21 was also produced.

Example Samples A-1, A-2, and A-3 are water-soluble silver discoloration inhibitors (trade names “AC-20”, “AC-70”, and “AC-80” of Kitaike Sangyo Co., Ltd.), respectively. It was used.
In Example Sample B-1, an isopropyl alcohol-based silver discoloration inhibitor (trade name “Silver Keeper” of Nippon Electroplating Enclosures Co., Ltd.) was used.

In Example Sample C-1, a water-based silver discoloration inhibitor (trade name “ENTEC CU-56” from Meltex Co., Ltd.) was used.
In Example Samples D-1 and D-2, aliphatic organic compound-based silver discoloration inhibitors (trade names “New Dyne Silver” and “New Dyne Silver S-1” from Daiwa Kasei Co., Ltd.) were used.

In Example Sample E-1, a solvent-based silver discoloration inhibitor (trade name “B-1057” of Chiyoda Chemical Co., Ltd.) was used.
In Example Sample E-2, an isopropyl alcohol-based silver discoloration inhibitor (trade name “B-1009NS” of Chiyoda Chemical Co., Ltd.) was used.

The conventional sample is not subjected to surface treatment with a silver discoloration inhibitor.
Using these samples, the sulfuration test was conducted as follows.
In this sulfidation test, a desiccator containing 1% ammonium sulfide solution is prepared to accelerate the degree of color change due to the sulfidation phenomenon. The discoloration level (degree of discoloration) on the surface of the plating layer was visually evaluated in five stages. The results of this sulfidation test are shown in Table 1 and FIG. Here, the numerical value of the discoloration level means that the degree of discoloration increases as the value increases. Discoloration level = 0 indicates no discoloration, discoloration level = 1 slightly discoloration, discoloration level = 2 indicates medium discoloration, discoloration level = 3 means a strong color change, and a color change level = 4 means a very strong color change (blackening).

  In each of the above examples, since the silver discoloration prevention treatment film 21 (organic film) is formed on the surface of the silver plating layer 20, the surface of the silver plating layer 20 is discolored by the silver discoloration prevention treatment film 21. Thus, the effect of preventing discoloration of the surface of the silver plating layer 20 is obtained, which cannot be obtained with the conventional sample without the silver discoloration prevention treatment film 21.

  Specifically, Example Samples A-1, A-2, and A-3 are formed by forming an organic coating (silver discoloration prevention coating 21) on the surface of the silver plating layer 20 with an S-based fatty acid compound, and silver plating. The surface of the layer 20 is shielded from sulfide gas in the air, and discoloration of the surface of the silver plating layer 20 is prevented.

  In Example Sample B-1, an organic chelate film (silver discoloration prevention treatment film 21) is formed on the surface of the silver plating layer 20 with an isopropyl alcohol-based silver discoloration inhibitor to change the color of the surface of the silver plating layer 20. To prevent.

  In Example Sample C-1, an organic film (silver discoloration prevention treatment film 21) having a thickness of about 30 angstroms was formed on the surface of the silver plating layer 20 with a water-based silver discoloration prevention agent. Prevent surface discoloration.

  In Example Samples D-1 and D-2, an organic chelate coating (silver discoloration prevention coating 21) is formed on the surface of the silver plating layer 20 using an aliphatic organic compound-based silver discoloration inhibitor, and silver plating is performed. Prevent discoloration of the surface of the layer 20.

  In Example Samples E-1 and E-2, an organic coating (silver discoloration prevention coating 21) was formed on the surface of the silver plating layer 20 with a solvent-based, isopropyl alcohol-based silver discoloration inhibitor, and the silver plating layer 20 Prevent discoloration of the surface.

  Among these example samples, those having particularly great discoloration prevention effects are the example samples D-2, D-1 and isopropyl using an aliphatic organic compound-based silver discoloration inhibitor that forms an organic chelate film. It was Example Samples B-1 and E-2 using alcohol-based silver discoloration inhibitors. Therefore, when an aliphatic organic compound-based or isopropyl alcohol-based silver discoloration inhibitor is used, an organic chelate film (silver discoloration prevention film 21) is formed on the surface of the silver plating layer 20, and the discoloration of the surface of the silver plating layer 20 is achieved. It seems that the preventive effect can be stably maintained over a long period of time.

  On the other hand, water-based and solvent-based silver discoloration inhibitors generally have less discoloration prevention effects than aliphatic organic compound-based or isopropyl alcohol-based silver discoloration inhibitors, but water-based silver discoloration inhibitors. Among them, only A-2 was effective in preventing discoloration similar to that of an aliphatic organic compound-based or isopropyl alcohol-based silver discoloration preventing agent.

  In contrast, in the conventional sample, the surface of the silver plating layer is not coated with the silver discoloration prevention treatment film, so that the discoloration proceeds in a shorter time than the example sample.

  According to the present embodiment described above, after the light emitting element 12 is mounted, the surface of the silver plating layer 20 to be the light reflecting surface 22 is surface-treated with the silver discoloration inhibitor to form a transparent thin silver discoloration prevention treatment film 21. In the case where the light emitting element is mounted after the surface of the silver plating layer is subjected to silver discoloration prevention treatment with a silver discoloration inhibitor before mounting the light emitting element, as in a comparative example (see FIG. 4) described later. Unlike the case where the light emitting element 12 is mounted by applying heat of about 230 ° C., the problem that the silver discoloration prevention coating film 21 on the surface of the silver plating layer 20 is burned out by heat during mounting cannot occur at all. Moreover, the silver discoloration prevention effect by the silver discoloration prevention treatment film 21 can be maintained over a long period of time. For this reason, even if the resin that seals the cavity 13 is gas permeable, or the sulfur component is contained in the sealing resin, the sulfur component in the permeate gas or the sulfur component in the sealing resin is a silver plating layer. Touching 21 can be prevented by the silver discoloration prevention treatment film 21, and discoloration of the surface of the silver plating layer 20 due to a sulfurization phenomenon or the like can be prevented over a long period of time.

  Moreover, in this embodiment, the base metallized layer 18 is simultaneously fired on the peripheral side surface of the cavity 13 of the package body 11, and the silver plated layer 20 is formed on the base metallized layer 18 via the base nickel plated layer 19. Therefore, the bonding strength between the package body 11 (ceramic), the base metallized layer 18, the base nickel plating layer 19 and the silver plating layer 20 is increased, and the process of mounting the light emitting element 12 on the package body 11 or the like There is also an advantage that the silver plating layer 20 can be prevented from peeling off even when a thermal load is applied to the silver plating layer 20 in a process of sealing the surface with a transparent resin.

  As described above, when the silver discoloration prevention treatment process is added to the manufacturing process of the light emitting element mounting package, after the completion of the silver plating process, as shown in the comparative example shown in FIG. It is conceivable that the surface of the silver plating layer is subjected to silver discoloration prevention treatment with a silver discoloration preventing agent, and then a light emitting element is mounted in the cavity of the package body. For this comparative example, using the same silver discoloration inhibitor as in the example (Table 1), a test was conducted to examine the relationship between the type of silver discoloration inhibitor and the discoloration prevention effect on the surface of the silver plating layer. The test results are shown in Table 2 below. The sample of this comparative example is different from the sample of the example in that after the silver discoloration prevention treatment was performed before mounting the light emitting element, the light emitting element was mounted by heating at about 230 ° C. using a solder preform. .

  As is clear from this test result, in the comparative example, after performing the silver discoloration prevention treatment, the light emitting element was mounted by heating at about 230 ° C., so any silver discoloration preventing agent was used. It was found that the silver discoloration prevention treatment film on the surface of the silver plating layer was almost burned away by heat during mounting, and the silver discoloration prevention effect was almost lost. Therefore, in order to avoid burning of the silver discoloration prevention treatment film due to heat at the time of mounting, it is necessary to perform a silver discoloration prevention treatment after the light emitting element is mounted.

  In the package configuration example of FIG. 1, the light reflecting surface 22 is formed only on the peripheral side surface of the inner surface of the cavity 13, but the light reflecting surface 21 is formed across the bottom surface of the cavity 13, There may be a portion where the light reflecting surface 22 is not formed on a part of the peripheral side surface.

  The method for mounting the light emitting element 12 in the cavity 13 is not limited to the method using the solder preform 23. For example, cream light solder is applied to the element mounting portion 24 and the light emitting element 12 is soldered. Of course, the light emitting element may be mounted without applying heat using an adhesive.

  In addition, it goes without saying that the present invention can be implemented in various modifications, such as being applicable to a light emitting element mounting package formed of a low temperature fired ceramic in which the package body is fired at 1000 ° C. or lower.

It is a longitudinal cross-sectional view which shows the structural example of the light emitting element mounting package in one Example of this invention. It is a figure explaining the work procedure of the element mounting process of an Example. It is a figure which shows the order of the process of the principal part of the manufacturing method of an Example. It is a figure which shows the order of the process of the principal part of the manufacturing method of a comparative example. It is a longitudinal cross-sectional view which shows the structure of the conventional light emitting element mounting package.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Package main body, 12 ... Light emitting element, 13 ... Cavity, 18 ... Base metallizing layer, 19 ... Base nickel plating layer, 20 ... Silver plating layer, 21 ... Silver discoloration prevention coating film, 22 ... Light reflection surface, 23 ... Solder Preform, 24 ... Element mounting part

Claims (2)

In a method of manufacturing a light emitting element mounting package in which a light emitting element is mounted in a cavity of a package body and a light reflecting surface for reflecting light of the light emitting element is formed on the inner surface of the cavity.
A silver plating step of forming a silver plating layer on at least a portion of the cavity inner surface of the package body forming the light reflecting surface;
An element mounting step of mounting the light emitting element in the cavity of the package body;
And a silver discoloration prevention treatment step of performing silver discoloration prevention treatment on the surface of the silver plating layer that becomes the light reflecting surface after mounting of the light emitting element with a silver discoloration prevention agent.   In the silver discoloration prevention treatment step, at least the surface of the silver plating layer serving as the light reflecting surface of the package body on which the light emitting element is mounted is immersed in a solution of a silver discoloration inhibitor, The method of manufacturing a light emitting element mounting package according to claim 1, wherein the surface of the layer is subjected to silver discoloration prevention treatment.

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