JP2008034550A - Wiring substrate for light-emitting element and light-emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring substrate for light-emitting element and a light-emitting device, which are suppressed in color uneveness and small in size, while being superior in heat dissipation. <P>SOLUTION: The light-emitting device is equipped with an insulating substrate 1 comprising of ceramics, and a sintered metallic body 3 baked and embedded, simultaneously with the insulating substrate 1. The sintered metallic body 3 is provided with an upper end 3a positioned below the upper surface 1a of the insulating substrate 1, and is provided with a recess 5 for receiving the light-emitting element 23, while a connecting electrode 7 electrically connected to the light-emitting element 23 is arranged on the surface 1a of the insulating substrate 1 at the outside of the recess 5. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a light emitting element wiring board and a light emitting device for mounting a light emitting element such as a light emitting diode.

  Conventionally, light emitting devices using LEDs have been used for various applications because of their extremely high luminous efficiency and the small amount of heat generated by light emission compared to incandescent bulbs. However, since it emits less light than incandescent bulbs and fluorescent lamps, it is used as a light source for display rather than for illumination, and the energization amount is very small at about 30 mA. (For example, refer to Patent Document 1).

  In recent years, with the increase in brightness and whiteness of light-emitting devices using light-emitting elements, light-emitting devices have been frequently used for backlights of mobile phones, large liquid crystal TVs, and the like. However, as the brightness of light emitting elements increases, the heat generated from the light emitting device also increases, and in order to eliminate the decrease in the brightness of the light emitting elements, such heat dissipation that dissipates such heat more quickly than the elements is high. There is a need for a light emitting element wiring board having the above (for example, see Patent Document 2).

  In addition, as a substrate structure that takes heat dissipation into consideration, in order to effectively diffuse the heat generated in the light emitting element, a high thermal conductor such as metal and the light emitting element are brought into structural contact to increase heat dissipation. (For example, refer to Patent Document 3).

  However, Patent Document 3 proposes a wiring board in which an insulating base is filled with a metal body. However, the metal body is peeled off from the insulating base as the light emitting element is heated and lowered, and reliability after mounting deteriorates. . Further, the metal body is detached from the insulating base and the wiring breaks, so that the LED does not function.

On the other hand, Patent Document 4 proposes a penetrating metal body that is fired at the same time as an insulating substrate, and is a wiring board excellent in heat dissipation and reliability. (For example, see Patent Document 4)
In addition, the light emitting device is also required to be small in size, and a light emitting element wiring board having a heat radiating base made of metal and a recess for accommodating the light emitting element has been reported (for example, Patent Document 5). reference.).
JP 2002-134790 A JP 2003-347600 A Japanese Patent No. 3259420 JP 2006-93565 A JP 2006-80165 A

  However, in the invention described in Patent Document 4, since light emitted from the light emitting element is irradiated not only to the through conductor but also to the insulating substrate and the electrode, the light utilization efficiency is reduced due to the difference in reflectance and color tone. Or have color irregularities.

  On the other hand, in the invention described in Patent Document 5, although uneven color can be suppressed, since the heat dissipation base and the lower sealing part which is an insulator are separately manufactured and both are thermocompression bonded, Each of the heat dissipating base and the lower sealing portion has a drawback that it is difficult to reduce the size because it is necessary to secure a strength, that is, a size that can be handled without breaking or deforming each member.

  Accordingly, an object of the present invention is to provide a light-emitting element wiring substrate and a light-emitting device that are excellent in light utilization efficiency, have little color unevenness, have excellent heat dissipation, and can be miniaturized.

  The wiring board for a light-emitting element of the present invention comprises an insulating base made of ceramics and a sintered metal body that is simultaneously fired and embedded in the insulating base, and the upper end of the sintered metal body is the insulating base. And a recess for accommodating the light emitting element, and a connection electrode electrically connected to the light emitting element is disposed on the surface of the insulating base outside the recess. It is characterized by.

  In the light-emitting element wiring board of the present invention, it is desirable that the sintered metal body is embedded so as to penetrate the insulating base.

  The wiring board for a light-emitting element according to the present invention has a connection terminal disposed on the lower surface of the insulating base, and the connection terminal and the connection electrode are electrically connected by an internal wiring provided inside the insulating base. It is desirable that the connection terminals and the sintered metal body are arranged so as to overlap with each other through the insulating base in the thickness direction of the light emitting element wiring board.

  In the light emitting device of the present invention, the light emitting element is accommodated in the recess of the light emitting element wiring board described above, and the electrode of the light emitting element is electrically connected to the connection electrode of the light emitting element wiring board. It is characterized by being.

  The wiring board for a light-emitting element of the present invention is miniaturized by simultaneously firing a sintered metal body having a recess for housing the light-emitting element and an insulating base made of ceramics and embedding the sintered metal body in the insulating base. Easy to do. In addition, since most of the light emitted from the light emitting element is irradiated to the sintered metal body and not to the insulating substrate or the wiring, the light use efficiency is not lowered due to the difference in reflectance and color tone, and color unevenness does not occur. As a result, the light utilization efficiency can be increased and the color unevenness can be reduced.

  Furthermore, by providing the sintered metal body so as to penetrate the insulating base, heat generated from the light emitting element can be released from the bottom surface of the recess to the opposite main surface on which the light emitting element is mounted. Therefore, it is possible to prevent the light emitting element from being excessively heated and to further increase the luminance.

  In addition, a connection terminal is provided on the lower surface of the light-emitting element wiring board, and the connection terminal having excellent thermal conductivity compared to the insulating base and the sintered metal body overlap with each other through the insulating base in the thickness direction of the light-emitting element wiring board. By arranging in this way, it is possible to maintain the heat dissipation of the wiring board for light emitting element while securing the area of the connection terminal.

  According to the light emitting device of the present invention in which the light emitting element is mounted on the wiring substrate for light emitting element of the present invention described above, the light emitting device is small, has little color unevenness, and has excellent heat dissipation.

  The light-emitting element wiring board of the present invention is embedded in an insulating base 1 made of ceramics and simultaneously fired in the insulating base 1, as shown in FIGS. 1 (a), 1 (b), and (c), for example. The sintered metal body 3 includes a recessed metal 5 in which the upper end 3a of the sintered metal body 3 is positioned below the upper surface 1a of the insulating substrate 1 and which houses the light emitting element. A connection electrode 7 that is electrically connected to the light emitting element is disposed on the surface 1 a of the insulating base 1 outside the recess 5.

  Since the sintered metal body 3 is simultaneously fired and embedded in the insulating base 1, the sintered metal body 3 and the insulating base 1 can be integrally formed. Since it is not necessary to assemble, the small light emitting element wiring board 9 can be easily manufactured.

  Further, the upper end 3a of the sintered metal body 3 is positioned below the upper surface 1a of the insulating base body 1 so that the upper end 3 of the sintered metal body 3 coincides with the upper surface 1a of the insulating base body 1 or the sintered metal body 3 Is disposed inside the insulating substrate 1. By arranging the sintered metal body 3 in this way, it is possible to easily achieve a reduction in the height of the light emitting element wiring substrate 9.

  Further, the connection terminal 11 is provided on the lower surface 1b of the light emitting element wiring substrate 9, and the connection terminal 11 and the connection electrode 7 are electrically connected by the internal wiring 13 disposed inside the insulating base 1, thereby realizing a three-dimensional structure. A light-emitting element wiring board 9 can be reduced in size by incorporating a typical electric circuit.

  Further, according to the present invention, most of the light output from the light emitting element is output as it is or is reflected by the bottom surface 5a of the recess 5 or the inner wall surface 5b of the recess, so that uneven color of the reflected light hardly occurs. There is also an advantage.

  In particular, the sintered metal body 3 is preferably thick from the viewpoint of heat dissipation. In particular, as shown in FIG. 1B, it is desirable that the sintered metal body 3 is embedded so as to penetrate the insulating base 1 from the viewpoint of improving heat dissipation. The form in which the sintered metal body 3 penetrates the insulating base 1 means a form in which the sintered metal body 3 is arranged in the vertical direction of the through hole formed so as to penetrate the insulating base 1. Yes.

  If the heat dissipation is limited, the side wall of the sintered metal body 3 is made vertical as shown in FIG. 1B, or the sintered metal body 3 becomes larger on the lower surface side of the wiring board 9 for light emitting elements. It is desirable to do so.

  However, since it is difficult to increase the area of the connection terminal 11 in such a form, it is difficult to position the light-emitting device using the light-emitting element wiring board 9 of the present invention when mounted on the external circuit board. There is a case.

  Therefore, as shown in FIG. 1C, a step is provided on the side surface of the sintered metal body 3 so that the sintered metal body 3 becomes smaller on the lower surface side of the light emitting element wiring substrate 9, thereby penetrating the insulating substrate 1. Even when the sintered metal body 3 is provided as described above, the connection terminal can be enlarged.

  As shown in FIG. 1C, when the connection terminal 11 and the sintered metal body 3 are arranged so as to overlap with each other with the insulating base 1 in the thickness direction of the light emitting element wiring substrate 9, an external circuit is provided. The mounting property to the substrate is improved and the sintered metal body 3 and the connection terminal 11 having excellent thermal conductivity are brought close to each other although the insulating base 1 is interposed between the sintered metal body 3 and the connection terminal 11. Therefore, it is possible to form a heat transfer path with a small distance and excellent thermal conductivity, and thus excellent heat dissipation.

  That is, among the forms of FIGS. 1A, 1B, and 1C, the light emitting element wiring substrate 9 of the form shown in FIG. 1B is most excellent from the viewpoint of heat dissipation. On the other hand, although the heat dissipation is slightly inferior, the light-emitting element wiring substrate 9 shown in FIGS. 1A and 1C has an advantage of being excellent in mountability with an external circuit substrate.

  Note that the connection terminal 11 and the sintered metal body 3 overlap with each other through the insulating base 1 when the connection terminal 11 is viewed through the insulating base 1 perpendicularly from above the light emitting element wiring substrate 9. And the sintered metal body 3 are arranged so as to overlap at least partially.

  When the exposed area of the sintered metal body 3 is equal on the lower surface of the light emitting element wiring substrate 9, the heat dissipation improves as the area where the connection terminal 11 and the sintered metal body 3 overlap increases. Further, when the light emitting element wiring board 9 is mounted on an external board via solder or the like, even if a slight misalignment occurs, the tolerance of physical misalignment is increased and melting is performed. Since the effect of alignment due to the surface force of the solder is increased, the mountability is improved.

  Further, the thinner the insulating substrate 1 interposed between the connection terminal 11 and the sintered metal body 3, the better the heat dissipation. However, from the viewpoint of securing the insulating property, it is preferably 30 μm or more.

As the ceramic used as the insulating substrate 1, an Al ₂ O ₃ -based sintered body having Al ₂ O ₃ as a main crystal phase is excellent in that it is inexpensive and easy to manufacture. Further, there is expensive, but thermally conductive, may be used better AlN sintered body and Si ₃ N ₄ quality sintered body strength.

Further, by setting the thermal expansion coefficient of the insulating substrate 1 used for the light emitting element wiring substrate 9 to 8.5 × 10 ⁻⁶ / ° C. or more, the connection reliability with a sintered metal body or an external printed board can be improved. It can be much higher. Needless to say, the reliability of bonding with a sealing resin or the like provided to cover the light emitting element to be mounted is also improved. In particular, 9.0 × 10 ⁻⁶ / ° C. or higher is preferable, and 10.0 × 10 ⁻⁶ / ° C. or higher is more preferable. For example, the insulating substrate 1 of 8.5 × 10 ⁻⁶ / ° C. or higher is forsterite or It can be produced by using MgO. Further, the insulating substrate 1 of 10.0 × 10 ⁻⁶ / ° C. or higher can be produced by using MgO.

  Further, by setting the thermal conductivity of the insulating base 1 used for the light emitting element wiring substrate 9 to 30 W / m · K or more, the heat dissipation from the insulating base 1 itself is improved, and the luminance of the light emitting element is prevented from being lowered. Is possible. In particular, it is preferably 35 W / m · K or more, more preferably 40 W / m · K or more, and most preferably 45 W / m · K or more. For example, an insulating substrate of 30 W / m · K or higher can be manufactured by using high-purity alumina or MgO having a purity of 99% or higher.

Further, when an Al ₂ O ₃ sintered body having Al ₂ O ₃ as a main crystal phase is used as the insulating base 1, an inexpensive raw material can be used, and an inexpensive wiring board 9 for a light-emitting element is formed. Obtainable.

Note that the _Al 2 _{O 3} and _Al 2 _{O 3} quality sintered body composed mainly crystalline phase, for example, by X-ray diffraction, is like the peak of _Al 2 _{O 3} is detected as the main peak, Al ₂ It is desirable to contain 50 volume% or more of O ₃ crystals as a volume ratio.

Moreover, such a sintered compact is made of, for example, Al ₂ O ₃ powder having an average particle diameter of 1.0 to 2.0 μm and a purity of 99% or more, and Mn ₂ O ₃ having an average particle diameter of 1.0 to 2.0 μm. , SiO ₂ , MgO, SrO, CaO. A molded body to which at least one sintering aid selected from the group consisting of CaO is added is fired in a temperature range of 1300 to 1500 ° C.

And, for the addition amount of Al ₂ O ₃ other than the compositions, such as sintering aids, in order to obtain a dense body of the Al ₂ O ₃ as a main crystal, preferably 15 wt% or less, more desirably, 10 It is desirable to set it as the mass% or less. In particular, when the amount of the composition other than Al ₂ O ₃ such as a sintering aid is set to 15% by mass or less, most of the obtained insulating substrate 1 can be formed of Al ₂ O ₃ crystals. . These sintering aids are preferably added in an amount of 5% by mass or more, and more preferably 7% by mass or more in order to lower the firing temperature.

A binder and a solvent are further added to such a composition containing Al ₂ O ₃ as a main component to produce a slurry. For example, a sheet-like molded article is produced by a doctor blade method, After printing and filling a conductive paste containing at least metal powder on the surface or through-holes provided in the sheet-like molded body, this sheet is laminated and fired in an oxidizing atmosphere, a reducing atmosphere, or an inert atmosphere. Thereby, the wiring board 9 for light emitting elements provided with the wiring circuit by which the connection electrode 7, the connection terminal 11, and the penetration conductor 13 are arrange | positioned at the insulating base | substrate 1 is producible. Needless to say, the wiring circuit can be formed on the surface of the insulating substrate 1 by a thin film method or by transferring a metal foil onto the surface of the molded body.

  The conductor used for the wiring circuit is composed mainly of at least one of W, Mo, Cu, and Ag as a conductor component, and ceramic binder added at a ratio of 0 to 5% by weight with an acrylic binder and acetone. It can be formed by mixing as a solvent, preparing a conductive paste, and printing and applying it on a ceramic green sheet using a screen printing method or the like.

  The sintered metal body 3 includes a step of producing a ceramic green sheet, a metal sheet made of a metal material having substantially the same thickness as the ceramic green sheet, and a step of forming a through hole at a predetermined location of the ceramic green sheet. A step of laminating a metal sheet in which through holes are formed in advance on a ceramic green sheet in which through holes are formed or a metal sheet in which through holes are not formed, and a through hole forming portion in the ceramic green sheet is a metal sheet By pressing from the side, a part of the metal sheet can be embedded in the through hole, and a formed body in which the ceramic green sheet and the metal sheet are integrated can be formed by simultaneous firing.

  Such a metal sheet is mainly composed of at least one of W, Mo, Cu, and Ag, and ceramic powder is added to this at a ratio of 0 to 5% by weight with an organic resin (binder) and toluene as a solvent. To form a slurry, and then formed into a sheet using a doctor blade method or the like.

  In addition, since the metal surface is exposed in the recess 5, it is not necessary to print a conductor in a separate process, so a plating layer (not shown) made of Ni, Au, Ag, Al or the like is easily formed. And the light utilization efficiency can be improved.

  Then, for example, as shown in FIGS. 2 (a) and 2 (b), the LED chip 23 or the like, or an adhesive 25 such as solder or resin is applied to the light emitting element wiring board 9 of the present invention described above. The terminal (not shown) of the light emitting element 23 and the connection electrode 7 are connected by the bonding wire 27 and sealed so as to cover the light emitting element 23, the bonding wire 27 and the connection electrode 7 accommodated in the recess 5. By covering with the stopping resin 29, the light emitting device 31 of the present invention is obtained.

  Further, in the light emitting device 31 of the present invention, it is desirable to adjust the depth of the concave portion 5 so that the upper end of the light emitting element 23 is located below the upper surface 1 a of the insulating substrate 1. Since the reflected light is reflected only by the bottom surface 5a of the recess 5 and the inner wall surface 5b of the recess, uneven color can be suppressed.

  In addition, you may add the fluorescent substance (not shown) for wavelength-converting the light which the light emitting element 23 radiates | emits to this sealing resin 29 as needed.

  In the example described above, the example in which the internal wiring 13 is provided has been described, but it is needless to say that the internal wiring 13 may not be provided.

  In addition, in the example of FIG. 1 (a), (b), (c) and FIG. 2 (a), (b), the magnitude | size seen from the top of the sintered metal body 3 is the metal sintered body 3 in a figure. The portions having the same width are constant, and the shape viewed from above may be a square or a circle, and various shapes may be used as necessary.

As a raw material powder, an Al ₂ O ₃ powder having a purity of 99% or more and an average particle diameter of 1.5 μm is 90% by mass, a purity of 99% or more, an Mn ₂ O ₃ powder having an average particle diameter of 1.3 μm is 5% by mass, and a purity of 99 The raw material powder was mixed with 5% by mass of SiO ₂ powder having an average particle size of 1.0 μm or more and a slurry was prepared by mixing an acrylic binder as a molding organic resin (binder) and toluene as a solvent.

  Thereafter, a ceramic green sheet was prepared by a doctor blade method.

  Also, a conductive paste was prepared by mixing 50% by mass of W powder with an average particle size of 1.5 μm and 50% by mass of Cu powder with an average particle size of 3.5 μm using a metal powder, an acrylic binder, and acetone as a solvent. .

  The metal sheet was prepared by mixing a metal powder and an acrylic binder as a molding organic resin (binder) and toluene as a solvent at the same ratio as the conductor paste to prepare a metal slurry to be a metal sheet. Thereafter, a metal sheet having substantially the same thickness as that of the ceramic green sheet was produced using this metal slurry by a doctor blade method.

  The ceramic green sheet was punched to form a via hole having a diameter of 100 μm. The via hole was filled with a conductive paste by a screen printing method and printed and applied in a wiring pattern.

  And a through-hole is formed in the predetermined location of the ceramic green sheet whose thickness after baking becomes 200 micrometers, and a part of metal sheet is penetrated in a through-hole by pressing the sintered metal body formation part in a ceramic green sheet from a metal sheet. Embedded in a ceramic green sheet and a metal sheet.

  Moreover, the recessed part which accommodates a light emitting element was formed by giving a punching process so that a wall surface might become slanting. In order to make the wall surface slant as described above, for example, a die may be pressed against a punched metal sheet so that the wall surface is slanted.

  That is, the reverse taper-shaped concave portion was formed by using a die having an inner diameter dimension of the die different from that of the punching pin and having a larger inner diameter dimension of the die.

  At this time, two sheets in which a metal sheet was embedded in advance in an insulating layer were prepared by aligning the positions. In addition, the sintered metal body was formed so as to be disposed substantially at the center of the light emitting element wiring board.

  In this way, for example, a laminate having an outer shape of 5 mm × 5 mm × thickness 0.8 mm after firing as shown in FIG. In addition, this laminated body is formed by forming a concave portion having a depth of 200 μm, a bottom size of 1 mm square, and an opening size of 1.4 mm square in a 3 mm square sintered metal body after firing.

  Then, after degreasing in a nitrogen-hydrogen mixed atmosphere at a dew point of + 25 ° C., it was subsequently fired for 2 hours at a maximum temperature of 1300 to 1700 ° C. in a nitrogen-hydrogen mixed atmosphere at a dew point of + 25 ° C. And the wiring board for light emitting elements which provided the connection electrode in one main surface of the insulating base | substrate, provided the connection terminal in the other main surface, and connected both with the internal wiring was produced.

  Thereafter, Ni, Au, and Ag plating were sequentially applied to the surfaces of the sintered metal body, the connection electrode, and the connection terminal.

An LED chip, which is a light emitting element with an output of 1.5 W, is mounted on the wiring board for these light emitting elements using an epoxy resin as an adhesive so that the upper end of the LED chip is completely accommodated in the concave portion. Then, the LED chip and the connection terminal were connected, and the LED chip and the connection terminal were further covered with a sealing resin made of a silicone resin having a thermal expansion coefficient of 40 × 10 ⁻⁶ / ° C. to obtain a light emitting device.

  Further, a current of 0.4 A was passed through the light emitting device, and the presence or absence of color unevenness was visually determined. In addition, the total radiant flux was measured 1 hour after energization. It can be determined that the larger the total radiant flux, the better the heat dissipation.

  Table 1 shows the test results of the light-emitting element wiring substrate manufactured through the above steps. In addition, although the total thickness of the sintered metal body is described in the table, the sintered metal body is continuously laminated from the concave portion. For example, when the total thickness of the sintered metal body is 600 μm It shows that one layer of the insulating base is formed under the formation of the sintered metal body in three consecutive layers.

Moreover, in Table 1, the sample described as “Yes” in the column of whether or not there is overlap is one in which the sintered metal body and the connection electrode overlap with each other in an area of 3 mm × 1.1 mm in the thickness direction of the wiring board for light emitting elements. It is.

  As shown in Table 1, there are no recesses or sintered metal bodies, and sample No. In 1, there was uneven color and the total radiant flux was low.

  On the other hand, sample no. In Nos. 2 to 5, color unevenness could not be confirmed at all, and the total radiant flux was also high.

It is sectional drawing of the wiring board for light emitting elements of this invention. It is sectional drawing of the light-emitting device of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Insulating base | substrate 1a ... Upper surface 1b of an insulating base | substrate ... Lower surface 3 of an insulating base | substrate ... Sintered metal body 3a ... Upper end 5 of a sintered metal body ... Recessed part 7 ... Connection Electrode 9 ... Light emitting element wiring substrate 11 ... Connection terminal 13 ... Internal wiring 11 ... Sealing part 15 ... Light emitting element wiring substrate 23 ... Light emitting element 31 ... Light emitting device

Claims (4)

An insulating base made of ceramics and a sintered metal body that is simultaneously fired and embedded in the insulating base, and the upper end of the sintered metal body is located below the upper surface of the insulating base and emits light. A wiring board for a light-emitting element, comprising: a concave portion that accommodates an element; and a connection electrode that is electrically connected to the light-emitting element is disposed on a surface of the insulating base outside the concave portion. The light emitting element wiring board according to claim 1, wherein the sintered metal body is embedded so as to penetrate the insulating base. A connection terminal is disposed on the lower surface of the insulating base, and the connection terminal and the connection electrode are electrically connected by an internal wiring provided inside the insulating base, and the thickness direction of the wiring board for the light emitting element 3. The wiring board for a light emitting element according to claim 1, wherein the connection terminal and the sintered metal body are arranged so as to overlap with each other with the insulating base interposed therebetween. 4. The light emitting element is accommodated in the concave portion of the light emitting element wiring substrate according to claim 1, and an electrode of the light emitting element is electrically connected to the connection electrode of the light emitting element wiring substrate. A light emitting device characterized by that.

Images