JP2008187053A - Thermally conductive paste, light emitting diode substrate using the same, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate for a light-emitting diode whose reflection member for enhancing luminance of the light-emitting diode can be easily formed and in which a countermeasure for heat generation can be taken, a method of manufacturing the same, and a paste material used for the same. <P>SOLUTION: A thermally-conductive as well as electrically-conductive paste, in which a thermosetting resin, curing agent, and thermally-conductive filler are included, is printed on a substrate, and is cured on the substrate to form a protrusion that is to be a light reflection member. The light reflection member is formed by electroplating preferably Ag or Ni on the surface of the cured paste. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a thermally conductive paste used for forming a light reflecting portion (hereinafter also simply referred to as a reflecting portion) for the purpose of increasing the brightness of a light emitting diode, and a light emitting diode substrate using the same and a light emitting diode substrate therefor It relates to a manufacturing method.

  More specifically, a reflective part used for the purpose of increasing the brightness of the light emitting diode is formed using a paste that has thermal conductivity and electrical conductivity and can be screen-printed. The present invention relates to a light emitting diode substrate capable of preventing heat generation and conducting electrical connection, a method for manufacturing the same, and a heat conductive conductive paste that enables this method.

  Conventionally, when a reflecting plate is used for the purpose of increasing the brightness of a light emitting diode, the reflecting portion is formed by using a heat-resistant engineering plastic such as polycarbonate as described in JP-A-9-81055. Using a resin as a material, a reflecting member of a predetermined shape is formed by injection molding, melt molding, extrusion molding, etc., electroless Ni (nickel) plating is performed, then Ag (silver) plating is performed, and this is bonded In general, the reflective portion is formed by adhering to a predetermined light emitting diode substrate with an agent.

  However, the method as described above has a problem that several steps are required until the formation of the reflective portion, and considerable time and cost are required.

Further, in order to improve the luminance of the light emitting diode, it is necessary to increase the input power, but heat generation at that time is a problem.
JP-A-9-81055

  The present invention has been made in view of the above, and a light-emitting diode substrate capable of easily forming a reflective portion used for increasing the brightness of a light-emitting diode at low cost, a manufacturing method thereof, and heat usable in the light-emitting diode substrate. An object is to provide a conductive paste. Another object of the present invention is to provide a countermeasure against heat generation when the input power is increased.

  The heat conductive conductive paste of the present invention is a heat conductive conductive paste (hereinafter also simply referred to as a paste) containing a thermosetting resin, a curing agent, and a heat conductive filler, and solves the above problems. In order to achieve this, it is assumed that a protrusion printed on the substrate and cured on the substrate to become a light reflecting portion is formed.

  In the above, as a heat conductive filler, the 1 type (s) or 2 or more types of metal powder selected from the group which consists of silver powder, copper powder, and silver coat copper powder can be used.

  The thermal conductivity of the paste after curing is preferably in the range of 5 to 50 W / m · K.

Moreover, it is preferable that the volume resistivity after hardening is 5 * 10 < ^-3 > (omega ^| ohm) * cm or less.

  The viscosity of the paste is No. BH type viscometer. It is preferable that the viscosity measured at 10 rpm using 7 rotors is in the range of 1000 to 8000 dPa · s.

  No. BH type viscometer. It is preferable that a thixo ratio (viscosity at 2 rpm / viscosity at 20 rpm), which is a ratio of a viscosity measured at 2 rpm and a viscosity measured at 20 rpm, is within a range of 3 to 7 using a 7 rotor.

  The paste of the present invention is preferably one that can be subjected to electroplating with Ag plating or Ni plating on the surface of the cured product.

  The method for producing a light-emitting diode substrate of the present invention includes printing the thermally conductive conductive paste of the present invention on a resin substrate or a ceramic substrate using a screen printing method, and curing the printed thermally conductive paste by heating, A light reflecting portion is formed by the cured product.

  In the said manufacturing method, it is preferable to form a light reflection part by performing Ag plating or Ni plating by electrolytic plating on the surface of the hardened thermally conductive paste.

  Through-hole conductive connection can also be performed by the heat conductive conductive paste printed using the screen printing method.

  Moreover, a heat conductive path can also be formed with the heat conductive conductive paste printed using the screen printing method.

  The light emitting diode substrate of the present invention is manufactured by any one of the above manufacturing methods.

  According to the present invention, it is possible to easily form a reflective portion at low cost by printing a heat conductive conductive paste on a light emitting diode substrate by a screen printing method, and excellent in heat dissipation and conductive connection. A light emitting diode substrate can be provided.

  In the present invention, by using a paste material having conductivity and thermal conductivity, printing is directly performed on a substrate by a screen printing method, heat curing is performed, and the obtained cured product is reflected by Ag plating treatment or the like. The part can be formed.

  At that time, if necessary, the conductive connection and the heat conduction path can be formed by filling the through hole of the substrate with the paste.

  In addition, the light beam reflection part as used in the field of this invention is the protrusion (bump) protruded from the surface of the board | substrate, and what kind of thing may be used as long as it can reflect the light of the light emitting diode provided in a board | substrate. However, in order to improve the reflection efficiency, a shape having a wide surface facing the light emitting diode is preferable. For example, a ring shape surrounding the light emitting diode as described later is preferably used. The surface shape may be flat, curved, or uneven.

  The thermally conductive paste of the present invention contains at least a thermosetting resin, a curing agent, and a thermally conductive filler as essential components.

  As the thermosetting resin, one or two or more selected from an epoxy resin, a phenol resin, an alkyd resin, a melamine resin, an acrylate resin, and a silicone resin are blended and used suitably. Among these, an epoxy resin is preferable from the viewpoint of heat resistance and adhesion.

  As the metal filler, metal powder such as silver powder, copper powder, silver-coated copper powder and nickel powder is used. Among these, silver powder, copper powder, and silver-coated copper powder are preferable.

  Although there is no restriction | limiting in particular in the shape of a metal filler, A dendritic shape, spherical shape, flake shape etc. are illustrated. Moreover, 1-50 micrometers is preferable and a particle size is more preferable 2-15 micrometers. Only one type of metal filler may be used or a mixture of two or more types may be used.

  The metal filler is blended in an amount of 400 to 1300 parts, more preferably 500 to 1000 parts, with respect to 100 parts of the thermosetting resin. When it is less than 400 parts, the thermal conductivity is low, and when it exceeds 1300 parts, workability may be reduced due to thickening.

  As the curing agent for the epoxy resin used in the present invention, an imidazole curing agent is preferable.

  Examples of imidazole curing agents include imidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-ethylimidazole, 2-phenylimidazole, 2-ethyl-4-methyl-imidazole, 1-cyanoethyl-2-un. Decylimidazole, 2-phenylimidazole, 2,4-diamino-6- [2'-methylimidazolyl- (1 ')]-ethyl-s-triazine.

  The imidazole curing agent is preferably blended in an amount of 1.5 to 40 parts by weight, more preferably 3 to 20 parts by weight with respect to 100 parts by weight of the epoxy resin. When the number of added parts is less than 1.5 parts by weight, curing is insufficient, and when it exceeds 40 parts by weight, the degree of thickening over time is large, and printability is deteriorated. In addition, the paste becomes thicker during storage and the workability deteriorates.

  The viscosity of the heat conductive paste of the present invention is preferably in the range of 1000 to 8000 dPa · s. When the viscosity is lower than 1000 dPa · s, problems such as paste bleeding and sagging occur after printing. If the viscosity exceeds 8000 dPa · s, screen printing becomes difficult. In addition, the viscosity of the paste in this specification is No. by BH type viscometer. The measured value at 25 ° C. and 10 rpm when using 7 rotors.

  The thixo ratio of the heat conductive conductive paste of the present invention is preferably in the range of 3-8. If the thixo ratio is lower than 3, problems such as bleeding and sagging of the paste after printing occur. If the thixo ratio is higher than 8, printing becomes difficult. In addition, the thixo ratio of the paste in this specification is No. by BH type viscometer. This is a value obtained by dividing the measured value at 2 rpm at 25 ° C. by the measured value at 20 rpm when using 7 rotors.

  Next, a method for forming the reflective portion, the heat conduction path, and the conductive connection in the light emitting diode substrate will be described.

  In the present invention, the above-described thermally conductive conductive paste is used for screen printing, and the paste is printed on a ceramic or organic substrate, for example, in a shape as shown in FIG. 1 or FIG. A reflective portion for the above is produced. For printing, screen plates prepared so as to be printed in these shapes are used.

  That is, FIG. 1 is an enlarged schematic view showing an example of formation of a reflection portion by a thermally conductive paste, (a) shows a plan view, and (b) shows a cross-sectional view taken along line AA in (a). Show. Reference numeral 1 denotes a reflection portion made of a heat conductive conductive paste, reference numeral 2 denotes a light emitting diode, and reference numeral 3 denotes an organic or ceramic substrate. As shown in these drawings, the heat conductive conductive paste is printed in a ring shape around the light emitting diode 2 to form a wall surface surrounding the light emitting diode 2, so that the reflecting portion 1 with extremely high reflection efficiency can be easily formed. Can get to.

  FIG. 2 is a plan view showing another example of the reflection portion formation. Reference numeral 4 denotes a heat conductive conductive paste (reflective portion), reference numeral 5 denotes a light emitting diode, and reference numeral 6 denotes an organic or ceramic substrate. This figure shows an example in which the paste is printed on the opposing wall. The reflective surface is not continuous, so the reflection efficiency is inferior to that of FIG. 1, but even in this shape, sufficient reflection can be obtained in practice. it can.

  The printed paste is heated and cured using an air oven or the like to obtain a cured paste. The curing conditions vary depending on the resin and curing agent to be used, but are usually preferably 120 to 200 ° C. and about 30 to 120 minutes.

  After the paste is cured, it is preferable to directly perform Ag plating or Ni plating using electrolytic plating in order to increase the reflection efficiency. That is, the paste of the present invention can increase the electrical conductivity, and by increasing the electrical conductivity, Ag plating can be directly performed by electrolytic plating.

  FIGS. 3A to 3C are cross-sectional views more specifically showing a light emitting diode substrate on which a reflection portion is formed with a heat conductive paste. These drawings show an example in which a ring-shaped reflecting portion is formed of a heat conductive conductive paste as in FIG.

  In these drawings, reference numerals 10, 20, and 30 indicate reflection portions (bumps) formed of paste, reference numerals 11 and 21 indicate heat conduction paths formed by filling the paste, and reference numerals 12, 22, and 32, respectively. Indicates a light emitting diode chip, reference numerals 13, 23 and 33 indicate conductive wires, reference numerals 14 and 24 indicate Al or Cu substrates, reference numerals 15 and 25 indicate glass epoxy substrates, and reference numerals 16, 26 and 36 indicate copper. A foil layer (copper plating) is indicated, numerals 17 and 27 indicate lid plating (copper plating), numerals 18, 28, and 38 indicate Ag or Ni plating, and numerals 19, 29, and 39 indicate epoxy for filling irregularities. A resist such as a resin is shown, and reference numeral 34 denotes a ceramic substrate.

  In any of the examples shown in any of the figures, a ring-shaped reflection portion made of a heat conductive paste is formed around the light emitting diode chip. The figure is bilaterally symmetric, and the parts where the reference numerals are omitted indicate the same as the symmetrical parts.

  In the example shown in FIG. 3A, a heat conduction path (thermal via) 11 for heat dissipation is formed under the light emitting diode chip 12, and in the example shown in FIG. 3B, the light emitting diode chip. The heat conduction path 21 is formed under the reflector 22 and the reflector 28. In the example shown in FIG. 3C, it is shown that the through hole is formed simultaneously with the reflector. Yes. That is, according to the necessity of the light emitting diode substrate, a reflective portion can be formed, and a heat conduction path such as these and / or through-hole conduction connection can be appropriately performed.

  Although the manufacturing method of a light emitting diode substrate is not specifically limited, Taking the thing of FIG.3 (c) as an example, it can manufacture with the following method.

  First, through holes and patterns are formed at predetermined positions of a copper foil layer 36 formed by copper plating on both surfaces of a ceramic substrate 34 such as alumina. Next, an epoxy resin resist 39 is applied and cured under predetermined conditions. Next, a paste is printed using a mesh screen or a metal screen, and filling of the through-holes and formation of a reflection part (bump) 30 having a predetermined shape are simultaneously performed with this paste. Next, heat treatment is performed at 160 ° C. for about 60 minutes in an air oven or the like to cure the printed paste.

  Next, by using a polishing machine or the like, the excess paste surface layer on the back surface (the surface on which the reflecting portion is not formed) is polished and made to the copper foil 36 surface. Furthermore, Ag or Ni plating 38 is applied to the surface layer of the copper foil 36 and the reflection portion 30 by electrolysis or electroless plating, and the electrical connection between the front and back of the substrate and the formation of the reflection portion plated with Ag or Ni are performed simultaneously. The light emitting diode substrate shown in FIG. 3C is obtained by attaching 32 and wiring the conducting wire 33.

  3 (a) and 3 (b) can also be manufactured according to this.

  That is, in the thing of Fig.3 (a), the opening part used as the heat conduction path 11 under the light emitting diode chip 12 is previously formed in the glass epoxy board | substrate 15 which provided the copper foil layer 16 on one side, and this is made into Al or Bonding with the Cu substrate 14, the paste is filled in the opening, cured, polished and leveled. Next, a lid plating 17 is applied to the heat conduction path 11 filled with this paste, followed by pattern formation to form a resist 19. Thereafter, in the same manner as described above, the reflective portion 10 is printed and cured, and the reflective portion 10 is subjected to Ag or Ni plating 18 by electrolysis or electroless plating, and the light emitting diode chip 12 is attached.

  3 (b) has a glass epoxy substrate 25 provided with a copper foil layer 26 on one side, and an opening serving as a heat conduction path 21 below the light emitting diode chip 22 and below the reflecting portion 20, respectively. Then, this is bonded to an Al or Cu substrate 24, the opening is filled with paste, cured, polished and leveled. After applying the lid plating 27 to the heat conduction path 21 filled with the paste, a pattern is formed and a resist 29 is formed. Thereafter, the reflecting portion 20 is printed and formed so as to cover the heat conduction path 21 to which the lid plating 27 is applied, and the reflecting portion 20 is subjected to Ag or Ni plating 28 by electrolysis or electroless plating. Can be attached.

  Examples of the present invention are shown below, but the present invention is not limited to the following examples.

[Examples and Comparative Examples]
The epoxy resin, the curing agent, and the silver-coated copper powder shown in Table 1 were mixed at the ratio (weight ratio) shown in the same table to prepare a thermally conductive paste. The details of each component are as follows.

Epoxy resin: Epoxy resin EP-4901E (Asahi Denka Kogyo Co., Ltd.) 80% by weight, ED-529 (Asahi Denka Kogyo Co., Ltd.) 20% by weight
Curing agent: 2-ethylimidazole (Shikoku Chemicals Co., Ltd.)
Silver-coated copper powder A: average particle size 15 μm, spherical powder, Ag coating amount 10 wt%
Silver-coated copper powder B: average particle size 10 μm, spherical powder, Ag coating amount 10 wt%
Silver-coated copper powder C: average particle size 3 μm, spherical powder, Ag coating amount 10 wt%

  About the said heat conductive electrically conductive paste, a viscosity, a thixo ratio, a volume change rate, heat conductivity, printability, and reflective part formation property were investigated. The results are also shown in Table 1. The test method and measurement method are as follows.

  The viscosity was 25 ° C. with BH viscometer rotor No. 7 (10 rpm).

  The thixo ratio was determined by measuring the rotor no. When 7 was used, the measured value at 2 rpm and the measured value at 20 rpm were determined, and the former was divided by the latter.

  The volume resistivity is obtained by screen-printing a paste on a glass epoxy resin having a thickness of 1.0 mm using a metal plate having a pattern of 6 cm in length, 1 mm in width, and 1 mm in thickness, and heat-curing at 160 ° C. for 60 minutes. I asked for it.

  The thermal conductivity was obtained by processing a paste cured product cured at 160 ° C. for 60 minutes into 1 cmφ and 1 mm thickness, and using a laser flash method.

  The printability is obtained by performing hole-filling printing using a metal plate in a hole having a hole diameter of 300 μm provided on a substrate having a plate thickness of 1 mm, and checking the filling property of the paste. What was not done was set as x.

  Reflective part formability is such that bump printing is performed using a metal plate on a 1 mm thick substrate, and after heat curing, bumps with a bump height of 40 μm or more and an inclination angle of 45 ° ± 15 ° can be formed. Those that could not be formed were marked with x.

It is an expansion schematic diagram which shows the example of the reflection part of the light emitting diode substrate formed with the heat conductive paste, (a) shows a top view, (b) is sectional drawing in the AA of (a). Show. It is a top view which shows the example of reflective part formation of another shape. It is sectional drawing which shows more specifically the example of the light emitting diode board | substrate which formed the reflection part etc. with the heat conductive conductive paste.

Explanation of symbols

1, 4 ... Reflection part (paste)
2,5 …… Light emitting diode chip 3,6 …… Organic or ceramic substrate 10,20,30 …… Reflecting part (paste)
11, 21 ... Heat conduction path (paste)
12, 22, 32 ... Light-emitting diode chip 13, 23, 33 ... Conductor 14, 24 ... Al or Cu substrate 15, 25 ... Glass epoxy substrate 16, 26, 36 ... Copper foil layer (copper plating)
17, 27 ... Lid plating (copper plating)
18, 28, 38 ... Ag or Ni plating 19, 29, 39 ... Resist 34 ... Ceramic substrate

Claims (12)

A heat conductive conductive paste comprising a thermosetting resin, a curing agent, and a heat conductive filler,
A thermally conductive paste, printed on a substrate, cured on the substrate, and the cured product forms a protruding portion that becomes a light reflecting portion.   The thermal conductivity according to claim 1, wherein the thermally conductive filler is one or more metal powders selected from the group consisting of silver powder, copper powder, and silver-coated copper powder. Conductive paste.   The heat conductive paste according to claim 1 or 2, wherein the heat conductivity after curing is in the range of 5 to 50 W / m · K. The thermally conductive conductive paste according to claim 1, wherein the volume resistivity after curing is 5 × 10 ⁻³ Ω · cm or less.   No. BH type viscometer. The heat conductive conductive paste according to any one of claims 1 to 4, wherein the viscosity measured at 10 rpm using a 7 rotor is in the range of 1000 to 8000 dPa · s.   No. BH type viscometer. The thixo ratio, which is the ratio of the viscosity measured at 2 rpm to the viscosity measured at 20 rpm (viscosity at 2 rpm / viscosity at 20 rpm), using 7 rotors is in the range of 3-7, Item 6. The thermally conductive conductive paste according to any one of Items 1 to 5.   The thermally conductive conductive paste according to any one of claims 1 to 6, wherein the surface of the cured product can be subjected to Ag plating or Ni plating by electrolytic plating.   The thermally conductive conductive paste according to any one of claims 1 to 7 is printed on a resin substrate or a ceramic substrate using a screen printing method, and the printed thermally conductive paste is cured by heating, and the curing is performed. A method for producing a light-emitting diode substrate, comprising forming a light reflecting portion by an object.   9. The method of manufacturing a light emitting diode substrate according to claim 8, wherein the light reflecting portion is formed on the surface of the cured heat conductive conductive paste by applying Ag plating or Ni plating by electrolytic plating.   The method for manufacturing a light-emitting diode substrate according to claim 8 or 9, wherein through-hole conductive connection is also performed by a thermally conductive conductive paste printed using the screen printing method.   The method for manufacturing a light-emitting diode substrate according to any one of claims 8 to 10, wherein a heat conduction path is also formed by a heat conductive conductive paste printed using the screen printing method.   The light emitting diode substrate manufactured by the manufacturing method of any one of Claims 8-11.

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