JP2008300773A - Manufacturing method of light emitting element mounting wiring board and light emitting element mounting wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a light emitting element mounting wiring board and a light emitting element mounting wiring board capable of enhancing heat radiation efficiency and of keeping light emission efficiency high over a long period of time. <P>SOLUTION: The manufacturing method of a light emitting element mounting wiring board 1 on which a light emitting element is mounted includes a bonding process of bonding a substrate part 2 on which the light emitting element is provided and an aluminum reflecting plate 3 undergoing mirror surface processing via a bonding sheet 5. The reflecting plate 3 can enhance heat radiation efficiency and light emission efficiency. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a light emitting element mounting wiring board and a light emitting element mounting wiring board.

Conventionally, various light-emitting element mounting wiring boards on which light-emitting elements such as LEDs are mounted have been used (see, for example, Patent Document 1).
Here, since light emitting elements such as LEDs emit heat when driven, it is necessary to radiate the heat. Therefore, heat can be efficiently radiated by using a copper pattern having high thermal conductivity.
However, since copper has low reflectance, it is difficult to improve the light emission efficiency of light emitting elements such as LEDs. Therefore, by providing nickel or silver with high reflectivity on the copper surface, the light emission efficiency of the LED or the like can be improved.
JP 2006-73842 A

  However, the above-described nickel and silver have a problem that the surface is easily discolored by oxidation, and the light emission efficiency decreases with the passage of time.

  The present invention has been made in view of such circumstances, and it is possible to improve the heat dissipation efficiency and to maintain the light emission efficiency high over a long period of time and the light emitting element mounting wiring board manufacturing method and light emission An object is to provide an element mounting wiring board.

In order to solve the above problems, the present invention provides the following means.
The present invention is a method of manufacturing a light emitting element mounting wiring board on which a light emitting element is mounted, wherein a substrate portion on which the light emitting element is provided and a reflecting plate made of mirror-finished aluminum are interposed via an adhesive sheet. It includes a bonding step of bonding.

  According to the present invention, the heat generated from the light emitting element is dissipated through the reflecting plate, and the light emitted from the light emitting element is reflected by the reflecting plate.

  Further, according to the present invention, in the bonding step, the reflective sheet is temporarily bonded to the back surface of the adhesive sheet temporarily bonded in the temporary pressing step, and the temporary pressing step of temporarily bonding the adhesive sheet to the back surface of the substrate portion. And a curing heating step of heating and curing the adhesive sheet that has been finally press-bonded in the main press-bonding step.

  According to this invention, a board | substrate part and a reflecting plate can be adhere | attached favorably.

  Moreover, this invention includes the through-hole formation process which forms a through-hole over the said board | substrate part and the said adhesive sheet in the state by which the said adhesive sheet was temporarily crimped | bonded in the said temporary crimping process before the said main crimping | compression-bonding process. It is characterized by.

  According to the present invention, a light emitting element mounting wiring board can be manufactured quickly and easily.

  Further, the present invention is characterized in that, in the main press-bonding step, a dimension in which the adhesive sheet protrudes inward in the radial direction of the through hole by pressurization is within 1/4 of a radial dimension of the through hole. To do.

  According to this invention, it is possible to satisfactorily bond the substrate portion and the reflecting plate without blocking the through hole.

  Further, the present invention is characterized in that the substrate part is composed of a plurality of layers, and a stepped through hole is formed in the substrate part in the through hole forming step.

  According to this invention, a light emitting element, a connection line, etc. can be stored in a through-hole.

  Further, the present invention is to pressurize the adhesive sheet and the substrate portion in a state of being heated to a temperature of 70 ° C. to 140 ° C. in the temporary pressure bonding step, and to be a temperature of 120 ° C. to 180 ° C. in the final pressure bonding step. The adhesive sheet and the reflecting plate are pressurized in a heated state, and the adhesive sheet is cured and heated at a temperature of 130 ° C. to 160 ° C. in the curing and heating step.

  According to this invention, a board | substrate part and a reflecting plate can be adhere | attached favorably and reliably.

  In addition, the present invention provides a substrate portion on which a light emitting element is mounted, a reflector made of mirror-finished aluminum, and the substrate portion and the reflector, provided between the substrate portion and the reflector. A through-hole is formed in each of the substrate part and the adhesive sheet, and the reflection plate is exposed from the surface side of the substrate part through the through-hole. Features.

  According to the present invention, the heat generated from the light emitting element is dissipated through the reflecting plate, and the light emitted from the light emitting element is reflected by the reflecting plate.

  According to the present invention, since the mirror-finished reflector made of aluminum is provided via the adhesive sheet, the heat dissipation efficiency can be improved and the light emission efficiency can be kept high over a long period of time.

(Embodiment 1)
Hereinafter, a light emitting element mounting wiring board according to a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a wiring board for mounting a light emitting element as a first embodiment of the present invention.
The light emitting element mounting wiring board 1 includes a rectangular plate-like substrate portion 2.
The board | substrate part 2 consists of an epoxy resin insulation board | substrate with a glass cloth. In addition, as the board | substrate part 2, it is preferable to use the epoxy resin insulation board | substrate with a glass cloth filled with white inorganic powders, such as a titanium oxide, in an epoxy resin. The thickness of the substrate part 2 is 0.1 mm.
A through hole 9 is formed in the substrate portion 2, and a light emitting element such as an LED is provided in the through hole 9.

Further, a connection terminal 7 made of copper is provided in the vicinity of the through hole 9 in one main surface (upper surface) 2 a of the substrate portion 2.
A light emitting element or an external device is connected to the connection terminal 7.
A thin gold layer is provided on the surface of the connection terminal 7 in order to ensure connection reliability such as solder connection or wire bonding connection. The thin gold layer may be silver or the like.
For the formation of the gold or silver thin layer, a vapor deposition method or a plating method can be used. From the viewpoint of mass productivity and economical efficiency, it is desirable to use electrolytic plating or electroless plating.
A solder resist 6 is provided at a predetermined location on the upper surface of the connection terminal 7.

Further, a rectangular plate-like aluminum substrate (reflecting plate) 3 is provided on the other main surface (back surface) 2 b of the substrate portion 2 via an adhesive sheet 5.
One main surface 3a of the aluminum substrate 3 is mirror-finished, and the surface has a reflectivity of 95% when measured at a wavelength of 400 nanometers. The mirror surface processing includes, for example, polishing or anodizing, and anodizing may be provided on the surface of the aluminum substrate 3.
Moreover, the thickness of the aluminum substrate 3 should just be a grade which does not produce a deformation | transformation at the time of a manufacturing process or mounting of a light emitting element, and it is desirable that it is 0.1 mm or more. In addition, although the thickness of the aluminum substrate 3 is more advantageous for heat dissipation, it is disadvantageous in terms of workability and cost. Therefore, the thickness of the aluminum substrate 3 is desirably 2 mm or less.
Under such a configuration, when the light emitting element mounted in the through holes 9 and 11 generates heat, the heat is radiated through the aluminum substrate 3.

In addition, a through hole 11 is formed in the adhesive sheet 5. And the through-hole 9 and the through-hole 11 are arrange | positioned and corresponded. Thereby, the mirror surface portion 10 on the surface of the aluminum substrate 3 is exposed to the one main surface 2 a side through the through holes 9 and 11. Thereby, when the light emitting element is mounted in the through holes 9 and 11 and radiates light, a part of the light is reflected by the mirror surface portion 10 and radiated outward.
As the adhesive sheet 5, a low-fluidity adhesive sheet is used in which a projecting dimension inward in the radial direction to the through hole 11 is within ¼ of the radial dimension of the through hole 11 in a main press-bonding process described later. . That is, a low-fluidity adhesive sheet is used in which the protruding dimension inward in the radial direction to the through hole 11 is three times or less the thickness of the adhesive sheet 5.

As such an adhesive sheet, a high molecular weight epoxy resin sheet, a thermosetting thermosetting polyamideimide resin, a polyimide resin, an acrylic resin sheet, or the like can be used. That is, a resin whose fluidity is controlled by parameters such as the molecular weight of the resin and heating conditions during sheet production is used.
The thickness of the adhesive sheet 5 is selected from the range of 5 μm to 100 μm. As the thickness increases, the protruding dimension to the through hole 11 increases. On the other hand, when it becomes thin, workability, resin embedding property and smoothness are inferior. From these points, a more preferable thickness range is 10 μm to 50 μm.

Next, the manufacturing method of the light emitting element mounting wiring board 1 in the present embodiment configured as described above will be described.
First, as shown in FIG. 2, the board | substrate part 2 which is the epoxy resin copper clad laminated board (Mitsubishi Gas Chemical Co., Ltd. make, brand name: CCL-HL820WDI) containing a glass cloth is prepared. The thickness of the substrate part 2 is 0.1 mm. Reference numeral 21 denotes a copper layer provided on the front and back surfaces of the substrate unit 2.
As shown in FIG. 3, the connection terminal 7 is formed from the copper layer 21 on the substrate portion 2 by an etching method (terminal formation step).
Then, as shown in FIG. 4, a solder resist 6 is formed at a predetermined location of the connection terminal 7. Further, a nickel layer is formed on the surface of the connection terminal 7, and a silver layer is formed on the surface of the nickel layer. Note that a nickel alloy layer may be used instead of the nickel layer, and a gold layer may be used instead of the silver layer.

Furthermore, as shown in FIG. 5, the adhesive sheet 5 (Hitachi Chemical Industry Co., Ltd., trade name: KS7003) having a thickness of 25 μm is temporarily pressure-bonded to the entire surface of the other main surface 2b (temporary pressure-bonding step).
In the temporary pressure bonding step, pressure bonding is performed for 50 seconds at an ambient temperature of 95 ° C. and a pressure pressure of 0.5 Mpa.
Next, as shown in FIG. 6, through holes 9 and 11 are formed across the substrate portion 2 and the adhesive sheet 5 by a drill (through hole forming step). The diameter of the through holes 9 and 11 is 3.0 mm.

Then, one main surface is polished to a mirror surface, and the aluminum substrate 3 having a reflectivity of 95% is overlaid so that the mirror surface side and the adhesive sheet 5 are in contact with each other and subjected to main pressure bonding (main pressure bonding step).
In the main pressure bonding step, pressure bonding is performed for 80 seconds at an atmospheric temperature of 150 ° C. and a pressure pressure of 0.5 Mpa.
Thereafter, curing is performed for 2 hours at a temperature of 150 ° C. without applying pressure (curing heating step).
Thereby, the adhesive sheet 5 and the aluminum substrate 3 are bonded together, and the light emitting element mounting wiring board 1 shown in FIG. 1 is obtained.

Here, when the aluminum substrate 3 comes into contact with a plating solution or an etching solution used in the terminal forming step, the aluminum substrate 3 is easily corroded and a smooth mirror surface is lost, resulting in a decrease in reflectance.
Therefore, it is necessary to provide the aluminum substrate 3 after the terminal forming step.
Therefore, it is conceivable to provide the aluminum substrate 3 by a normal lamination press after the terminal forming step.
The lamination press usually performs pressure bonding for 2 to 3 hours at an atmospheric temperature of 180 to 200 ° C. and a pressure pressure of 3 to 4 MPa.
However, since the solder resist 6 melts at 150 ° C., the solder resist 6 is damaged in a normal lamination press. In addition, a normal laminating press causes circuit disconnection or short circuit.

In the present embodiment, the pressure bonding is performed separately in the temporary pressure bonding process and the main pressure bonding process.
FIG. 7 is a table showing the relationship between the temperature and the viscosity of the thermosetting resin that is the material of the adhesive sheet 5.
If it heats from a room temperature state, the resin component which comprises the adhesive sheet 5 will flow easily, and a viscosity will fall. On the other hand, when the temperature reaches a certain temperature, the resin is cured by a crosslinking reaction (crosslinking reaction between constituent molecules) of the resin with heating. That is, as the temperature rises, the fluidity of the resin is first improved, and then the fluidity of the resin is lowered (cured) by a crosslinking reaction by heating. As a result, the temperature-viscosity curve becomes a downwardly convex curve as shown in FIG.

In the present invention, one surface 5 a of the adhesive sheet 5 is temporarily bonded to the other main surface 2 b of the substrate portion 2 in the temporary pressure bonding step. Selection of temperature, pressure, and time during the pre-bonding process is such that peeling occurs on the bonding surface between the one main surface 5a and the other main surface 2b during drilling in the through-hole forming step performed after the temporary bonding. It is based on the degree that there is no. This is to prevent drilling debris and the like from entering the gap between one main surface 5a and the other main surface 2b.
In this temporary press-bonding step, if the heating is excessive, the resin cross-linking reaction proceeds, and in the main press-bonding step, the fluidity of the adhesive sheet 5 is lowered and the adhesion becomes insufficient. Therefore, temporary pressure bonding is performed to such an extent that the crosslinking reaction does not proceed. For this purpose, the temperature is 70 ° C. to 140 ° C., the pressure is 0.1-1 Mpa, and the time is 10-90 seconds.

  Next, after the through-hole forming step, main pressure bonding is performed. In the main press bonding step, the other main surface 5b of the adhesive sheet 5 and one main surface 3a of the aluminum substrate 3 are bonded. If the flow is excessive in the main pressure bonding step, the adhesive sheet 5 flows out of the through hole 11 and the through hole 11 is blocked. Furthermore, when the heating is excessive, the crosslinking reaction of the resin proceeds and the curing of the resin proceeds. Therefore, the main pressure bonding is performed to such an extent that the fluid does not excessively flow and does not excessively heat. Therefore, the temperature in the main press bonding step is 120 ° C. to 180 ° C., the press bonding pressure is 0.1 to 1 Mpa, and the time is 20 to 600 seconds. Further, the temperature in the curing and heating step is from 130 ° C. to 160 ° C., and the time is from 30 minutes to 150 minutes.

As described above, according to the light emitting element mounting wiring board 1 of the present embodiment, the heat generated from the light emitting element can be efficiently radiated by being transmitted through the aluminum substrate 3. Further, by reflecting the light emitted from the light emitting element by the mirror surface portion 10, the luminous efficiency can be kept high over a long period of time.
Moreover, since the board | substrate part 2 and the aluminum substrate 3 are adhere | attached through the adhesive sheet 5 by the temporary crimping | compression-bonding process, this crimping | compression-bonding process, and the hardening heating process, the aluminum substrate 3 is adhere | attached appropriately to the board | substrate part 2 after terminal formation. can do.
In addition, since the through holes 9 and 11 are formed by the through hole forming process after the temporary pressure bonding process, the through holes can be formed quickly and easily.
In addition, as the adhesive sheet 5, a low-fluidity adhesive sheet in which the projecting dimension inward in the radial direction to the through hole 11 is within ¼ of the radial dimension of the through hole 11 is used in the main crimping step. Thus, the substrate portion 2 and the aluminum substrate 3 can be favorably bonded without blocking the through hole 11.

(Embodiment 2)
Next, a second embodiment of the present invention will be described.
FIG. 8 shows a second embodiment of the present invention.
In FIG. 8, the same components as those shown in FIGS. 1 to 7 are denoted by the same reference numerals, and the description thereof is omitted.
This embodiment and the first embodiment have the same basic configuration, and different points will be mainly described here.

In the present embodiment, the first substrate portion 25 having a rectangular plate shape and the second substrate portion 23 having the same shape are laminated. The first substrate unit 25 and the second substrate unit 23 are joined by an adhesive sheet (not shown). A large-diameter through hole 26 is formed in the second substrate portion 23. Further, a small-diameter through hole 27 is formed in the first substrate portion 23. These through holes 26 and 27 are arranged on concentric lines. That is, the through holes 26 and 27 are formed in a step shape when viewed from the side.
Under such a configuration, light emitting elements are provided in the through holes 26, 27, and 11, and the light emitting elements and the connection terminals 7 are connected by wire bonding. At this time, since the through holes 26 and 27 are stepped, wires for wire bonding including the light emitting elements can be accommodated in the through holes 26 and 27.
In addition, the first substrate portion 25 is not damaged by the temporary pressure bonding step, the main pressure bonding step, and the curing heating step without damaging an adhesive sheet (not shown) between the first substrate portion 25 and the second substrate portion 23. And the second substrate portion 23 can be firmly maintained.

In the above embodiment, the reflectance of the mirror surface of the aluminum substrate 3 is 95%. However, the present invention is not limited to this and can be changed as appropriate. In particular, it is desirable that it is 80% or more and 100% or less.
Moreover, about the adhesive sheet 5, although the protrusion dimension to radial direction inner side to the through-hole 11 was 3 times or less of the thickness of the adhesive sheet 5, it is not restricted to this, It can change suitably. . In particular, the range of 0 to 5 times is desirable.
Furthermore, although the diameter of the through holes 9 and 11 is 3 mm, it is not limited to this and can be changed as appropriate. In particular, the range of 1 to 5 mm is desirable.
Moreover, although the thickness of the board | substrate part 2 was 0.1 mm, it is not restricted to this, A thickness dimension can be changed suitably.
The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

It is a sectional side view which shows 1st Embodiment of the wiring board for light emitting element mounting which concerns on this invention. It is a figure which shows the manufacturing method of the wiring board for light emitting element mounting of FIG. 1, Comprising: It is a sectional side view which shows a mode that the copper layer was provided in the front and back of a board | substrate part. It is a sectional side view which shows a mode that the connection terminal was formed from the copper layer of FIG. It is a sectional side view which shows a mode that the soldering resist was provided in the connecting terminal of FIG. It is a sectional side view which shows a mode that the adhesive sheet was provided in the board | substrate part of FIG. It is a sectional side view which shows a mode that the through-hole was formed in the board | substrate part and adhesive sheet of FIG. It is a table | surface which shows the relationship between the temperature of a thermosetting resin which is a material of an adhesive sheet, and a viscosity. It is a sectional side view which shows 2nd Embodiment of the wiring board for light emitting element mounting which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wiring board for light emitting element mounting 2 Board | substrate part 3 Aluminum substrate (reflection board)
5 Adhesive sheet 9, 11, 26, 27 Through hole

Claims (7)

A method of manufacturing a light emitting element mounting wiring board on which a light emitting element is mounted,
The manufacturing method of the wiring board for light emitting element mounting characterized by including the adhesion process which adhere | attaches the board | substrate part in which the said light emitting element is provided, and the reflecting plate which consists of mirror-finished aluminum through an adhesive sheet. The bonding step includes
A temporary pressure bonding step of temporarily pressing the adhesive sheet to the back surface of the substrate portion;
A main press-bonding step of finally press-bonding the reflection plate to the back surface of the adhesive sheet temporarily press-bonded in the temporary press-bonding step;
The method for manufacturing a wiring board for mounting a light-emitting element according to claim 1, further comprising a curing heating step of heating and curing the adhesive sheet that has been subjected to the final pressure bonding in the main pressure bonding step.   The through-hole formation process of forming a through-hole between the said board | substrate part and the said adhesive sheet in the state by which the said adhesive sheet was temporarily crimped | bonded in the said temporary crimping process before the said crimping | compression-bonding process, The manufacturing method of the wiring board for light emitting element mounting of 2 characterized by the above-mentioned.   4. The dimension according to claim 3, wherein, in the main press-bonding step, a dimension in which the adhesive sheet protrudes inward in a radial direction of the through hole by pressurization is within ¼ of a radial dimension of the through hole. Manufacturing method of the light emitting element mounting wiring board. The substrate part is composed of a plurality of layers,
5. The method for manufacturing a wiring board for mounting a light emitting element according to claim 3, wherein, in the through hole forming step, a stepped through hole is formed in the substrate portion. In the temporary press-bonding step, the adhesive sheet and the substrate portion are pressed in a state heated to a temperature of 70 ° C. to 140 ° C.,
In the main press-bonding step, the adhesive sheet and the reflection plate are pressed in a state heated to a temperature of 120 ° C. to 180 ° C.,
The method for manufacturing a wiring board for mounting a light-emitting element according to any one of claims 2 to 5, wherein in the curing and heating step, the adhesive sheet is cured and heated at a temperature of 130 ° C to 160 ° C. . A substrate portion on which the light emitting element is mounted;
A reflector made of mirror-finished aluminum;
An adhesive sheet that is provided between the substrate portion and the reflector, and bonds the substrate portion and the reflector;
A through hole is formed in each of the substrate part and the adhesive sheet, and the reflector is exposed from the surface side of the substrate part through the through hole. Board.

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