JPH04329680A - Light emitting device - Google Patents

Abstract

PURPOSE:To omit a flash removing step and to reduce a cost of a mold by injection molding thermoplastic resin having low thermal expansion coefficient at the time of molding sealing resin. CONSTITUTION:A light emitting diode 1 is die bonded to a lead frame 3 via conductive paste, and then internally wired with bonding wires 2. Then, permeable thermoplastic polyimide resin is injected from an inlet 9 in a state that the frame is inserted to a mold 8, and resin-sealed. In this case, since the injection molding is executed by using the thermoplastic resin, a molding cycle until the resin is cured is shortened to 10-30sec. Accordingly, even in the case of the mold for injecting a small number can obtain a sufficient mass productivity. Sealing resin 4, i.e., a lens 4 is injection molded in a high viscosity state by using permeable thermoplastic polyimide resin having a low linear expansion coefficient, high melting viscosity.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light-emitting device such as a light-emitting diode lamp, which is composed of a light-emitting diode chip, a metal lead frame for mounting the chip, and a resin for sealing them.

0002

[Prior Art] Conventional light emitting diode lamp (hereinafter referred to as LE)
The structure of a light emitting device such as D) is shown in FIGS. FIG. 12 is a sectional view of an LED lamp using a casting method, and FIG. 13 is a perspective view of a surface-mounted LED lamp using a transfer molding method.

In the figure, 1 is a light emitting diode, 2 is a bonding wire, 3 is a lead frame, and 4 is a transparent sealing resin body.

[0004] Casting type LED shown in FIG.
The lamp is manufactured by inserting a lead frame 3 equipped with a light emitting diode 1 into a plastic female mold, injecting liquid thermosetting epoxy resin, and heating and solidifying the epoxy resin in an oven to form a lens-shaped mold. The sealing resin body 4 is molded, and the lead frame 3 is cut with tie bars to separate the products.

On the other hand, the method of manufacturing an LED lamp using the transfer molding method shown in FIG. 13 involves inserting a lead frame 3 on which a light emitting diode 1 is mounted into a mold, and then injecting a thermosetting epoxy resin. , heat and harden in a mold to seal with resin. After resin sealing, deburring and tie bar cutting are performed to separate the products into products, and if necessary, lead frames are formed as shown in FIG. 13. In addition, in FIG. 13, 6 is a burr part.

[0006]

However, the following problems have been pointed out in the casting method shown in FIG.

(1) As shown in FIG. 12, the surface shape of the base of the lead frame of an LED lamp is not constant, with unevenness 5 occurring due to variations in the amount of epoxy resin injected and the surface tension of the resin.

(2) The female mold made of plastic has a diameter of 10 to 1
It has a low service life of about 00 cycles, so it needs to be replaced frequently.

(3) Since the accuracy of alignment between the lead frame and the female die is as high as several hundred μm, misalignment between the lead frame and the sealing resin body 4 occurs.

(4) Since resin shrinkage also occurs when molding the female mold, the shape of the sealing resin body 4 cannot be molded with high precision.

(5) Since the curing time of the epoxy resin is as long as about 10 hours, it is difficult to inline the production process.

On the other hand, in the transfer method shown in FIG. 13, the lead frame is inserted directly into the molding die, so dimensional accuracy is superior to the casting method, but the following problems have been pointed out. .

(1) The curing time of epoxy resin for transfer molding is as long as 3 to 5 minutes, and in order to increase mass production,
The number of cavities in the molding die must be approximately several hundred, which increases the manufacturing cost of the mold.

(2) As shown in FIG. 13, burrs 6 are likely to occur along the parting surface of the mold, requiring a burr removal step after molding.

(3) Cracks may occur in the sealing resin body 4 due to deburring.

In addition, in both the casting and transfer methods, as shown in FIGS. 14 and 15, peeling and cracking may occur due to the difference in linear expansion coefficient between the resin and the lead frame at high temperatures during solder reflow. . Here, FIG. 14 is a side view of a conventional light emitting device showing the state after the heat resistance test, and FIG. 15 is an enlarged view of the light emitting diode portion of the same plan view. As shown in FIGS. 14 and 15, it can be seen that peeling Z occurred after the heat resistance test.

Further, conventional light emitting devices use epoxy resin, which is a thermosetting resin, but the glass transition point of epoxy resin can only be used at a relatively low temperature of about 100°C. On the other hand, especially for surface-mounted LED lamps, the temperature reaches 250° C. due to surface-mounted solder reflow, which is difficult to cope with with the heat resistance properties of the resin described above.

In view of the above, the present invention aims to omit the deburring process, reduce mold costs, and provide a light emitting device compatible with surface mounting.

[0019]

[Means for Solving the Problems] The means for solving the problems according to claim 1 of the present invention, as shown in FIGS. In the light emitting device equipped with a translucent sealing resin body 4, the sealing resin body 4 is injection molded using a thermoplastic resin having a low coefficient of linear expansion.

[0020] Furthermore, the problem solving means according to claim 2 of the present invention is that a thermoplastic polyimide resin is used as the thermoplastic resin according to claim 1.

[0021]

[Operation] In the means for solving the problem according to claim 1, since the sealing resin body 4 is formed by injection molding in the mold using a thermoplastic resin having translucency, the molding cycle takes several tens of seconds. This makes it shorter than conventional molds, making it possible to sufficiently mass-produce even molds with a small number of molds. Therefore, it is possible to reduce mold costs.

Moreover, since the thermoplastic resin has a high melt viscosity, it can be molded in a high viscosity state.
Molding burrs are less likely to occur, and the burr removal process after molding can be omitted.

In the second aspect, since a thermoplastic polyimide resin is used as the thermoplastic resin, the coefficient of linear expansion of the sealing resin body 4 can be lowered to reduce the difference between the coefficient of linear expansion and the coefficient of linear expansion of the lead frame 3.

Therefore, peeling between the sealing resin body 4 and the lead frame 3 and cracks in the sealing resin body 4 are less likely to occur, and reliability is improved.

Furthermore, thermoplastic polyimide resin has extremely high heat resistance, with a heat distortion temperature of 238°C and a glass transition point of 250°C, and can withstand temperatures of 250°C during surface mounting by solder reflow. It is possible.

[0026]

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings.

[First Embodiment] FIG. 1 is a sectional view showing the resin sealing work of a light emitting device according to the first embodiment of the present invention, FIG. 2 is a sectional view showing the state after completion, and FIG. FIG. 4 is a side view of the light emitting device showing the state after the heat resistance test, and FIG. 4 is an enlarged view of the light emitting diode portion of the same plan view. Note that the same reference numerals are given to the same functional parts as those of the prior art shown in FIGS. 12 and 13.

As shown in FIG. 2, the light emitting device (LED
The lamp) includes a light emitting element 1 (light emitting diode), a lead frame 3 on which the light emitting diode 1 is mounted and internally connected to the light emitting diode 1 via bonding wires 2, and a sealing resin body 4 (lens) covering these elements. body).

The lens body 4 is injection molded in a highly viscous state using a translucent thermoplastic polyimide resin having a low linear expansion coefficient and high melt viscosity.

In this example, the thermoplastic polyimide resin has a melt viscosity of 500 to 1000 poise, a heat distortion temperature of 238° C., and a linear expansion coefficient of 5.5×10 −5
(cm/cm・°C) is used.

In FIG. 1, 8 is a molding die used for molding the sealing resin body 4, 8a is an upper mold thereof, 8b is a lower mold,
Reference numeral 9 indicates an injection port for injecting resin into the mold. Further, 8c is a mold member specially provided to smoothly form the lens shape of the lens body 4 of the LED lamp.
It is a sliding type that can be attached and detached by moving it in the horizontal direction X when removing a.

[0032] The above LED lamp is manufactured as follows.

First, the light emitting diode 1 is die-bonded to the lead frame 3 using a conductive paste (for example, silver paste), and then internal connections are made using the bonding wire 2. Next, as shown in FIG. 1, with this lead frame inserted into the molding die 8, a translucent thermoplastic polyimide resin is injected from the injection port 9 to perform resin sealing.

At this time, since injection molding is performed using thermoplastic resin, it takes 10 molding cycles until the resin hardens.
It will be as short as ~30 seconds. Therefore, sufficient mass productivity can be achieved even with a mold for a small number of molds.

Thereafter, the lead frame is separated into individual products by tab cutting.

[0036] Here, in the above-mentioned resin sealing process,
When a resin other than polyimide resin is used, the expansion coefficient of the resin is generally about 10×10 −5 (cm/cm·°C). For example, polymethylpentene is 11.7×10
-5 (cm/cm・°C), 6×10 for methacrylic resin
-5 (cm/cm・°C), polycarbonate is 7×1
0-5 (cm/cm·°C), and the epoxy resin for transfer is 7.5×10-5 (cm/cm·°C).

On the other hand, the linear expansion coefficient of a lead frame is 1.18×10-5 (cm/cm・°) for an iron frame.
C), 1.7 x 10-5 (cm/cm) with copper alloy frame
・°C). These resins and lead frame 3
Due to the mismatch in linear expansion coefficients between them, peeling between the lens body 4 and lead frame 3 and cracking of the lens body 4 occur during environmental tests such as temperature cycling. In order to prevent these, it is necessary to reduce the linear expansion coefficient of the resin as much as possible.

Therefore, in this embodiment, a thermoplastic polyimide resin is used as the epoxy for the sealing resin body 4, and the coefficient of linear expansion of the resin is as small as 5.5×10-5 (cm/cm・°C). This prevents the above-mentioned peeling and cracks from occurring.

Here, a heat resistance test was conducted on the light emitting device of this example. That is, a light emitting device in which a resin and a lead frame were closely bonded was heated to 260° C. for 30 seconds. As a result, as shown in FIGS. 3 and 4, no peeling or cracking occurred. This verified that the light emitting device of this example had excellent heat resistance.

By the way, conventional thermosetting resins are
The melt viscosity is low, for example, epoxy resin for transfer is 100 to 150 poise. Here, if the melt viscosity of the resin is low, when molding with the mold 8, the upper mold 8a and the lower mold 8
Uncured resin gets into the gaps created between b, etc., and when this hardens, resin burrs occur. In order to prevent this, it is necessary to set the melt viscosity of the resin high.

Therefore, in this embodiment, thermoplastic engineering plastics are used for the sealing resin body 4 (lens body) by taking advantage of the fact that they generally have a higher melt viscosity than epoxy resins. This prevents resin burrs from forming.

Moreover, since polyimide resin is used as this thermoplastic engineering plastic, as shown in Table 1, it is among the thermoplastic resins that usually have a melt viscosity of 2,000 to 10,000 poise, and its melt viscosity is 500 poise. The melt viscosity can be maintained at a medium level of ~1000 poise, and while the viscosity is higher than that of the conventional method and resin burrs are prevented, the bonding wire 2 can be prevented from breaking due to too high resin viscosity.

[0043]

[Table 1]

From the above, the following effects can be obtained.

(2) Misalignment between the lead frame and the sealing resin body, cracks in the sealing resin body, etc. can be prevented, and reliability can be improved.

(2) The occurrence of molding burrs can be prevented, and the burr removal process after molding can be omitted.

■Since sufficient mass productivity can be achieved even with a mold for a small number of molds, it is possible to reduce mold costs.

[Second Embodiment] FIG. 5 is a sectional view showing a resin sealing operation of a light emitting device according to a second embodiment of the present invention, and FIG. 6 is a sectional view showing the state after completion.

As shown in the figure, the light emitting device of this embodiment is a surface-mounted LED lamp, the sealing resin body 4 is formed in a rectangular shape, and the lead frame 2 is formed as necessary. It is something.

In this embodiment as well, the mold 8 shown in FIG.
The thermoplastic polyimide resin is injected from the injection port 9 to be molded.

After molding, the light emitting device is surface mounted on a substrate (not shown).

By the way, the temperature during surface mounting by solder reflow is approximately 250° C. If the glass transition point of the resin is low, resin deformation may occur during reflow, which may deteriorate the quality of the light emitting device.

However, the thermoplastic polyimide resin used in this example has extremely high heat resistance, with a heat distortion temperature of 238°C and a glass transition point of 250°C, and a surface mounting temperature of 250°C. It is possible to correspond to

A heat resistance test was also conducted in the same manner as in the first example to check for peeling and cracks between the resin and the lead frame. That is, the light emitting device was heated to 260°C for 30 seconds. As a result, as in the first example, no peeling or cracking occurred. Other functions and effects are the same as in the first embodiment.

It should be noted that the present invention is not limited to the above embodiments, and it goes without saying that many modifications and changes can be made to the above embodiments within the scope of the present invention.

FIGS. 7 and 8 are cross-sectional views showing an application example of the LED lamp of the present invention. All of these are sealed with resin and then filled with a thermoplastic resin with good light reflectivity (for example, a liquid crystal polymer colored white by mixing a white inorganic filler such as titanium white, or a thermoplastic resin such as polyphenylene sulfide). This is an example in which a reflector plate 10 is formed so as to surround the bottom and side surfaces of an LED lamp to provide a reflective effect and increase the output of light.

In addition, there are examples of side-lead type photodiodes as shown in FIG. 9, examples of surface-mounted photodiodes as shown in FIG. 10, and examples of photodiodes using a ceramic stem 11 as shown in FIG. The same effect can be obtained in the case of using thermoplastic polyimide resin as in the first and second embodiments.

Furthermore, in order to lower the coefficient of linear expansion of the sealing resin body 4, a transparent inorganic filler may be mixed into the sealing resin body 4.

[0059]

As is clear from the above description, according to claim 1 of the present invention, injection molding is performed using thermoplastic resin when molding the sealing resin body of the light emitting device, so the molding cycle takes several tens of seconds. This makes it shorter than conventional molds, making it possible to sufficiently mass-produce even molds with a small number of molds. Therefore, it is possible to reduce mold costs.

Furthermore, since thermoplastic resins generally have a high melt viscosity, molding can be carried out in a high viscosity state, making it difficult for molding burrs to occur, and making it possible to omit the burr removal step after molding.

In claim 2, since a thermoplastic polyimide resin having a small linear expansion coefficient is used as the thermoplastic resin, the difference in linear expansion coefficient between the sealing resin body and the lead frame can be reduced, and the sealing resin body Peeling between the lead frame and the lead frame and cracks in the sealing resin body are less likely to occur, improving reliability.

Furthermore, thermoplastic polyimide resin has extremely high heat resistance, with a heat distortion temperature of 238°C and a glass transition point of 250°C, so it can be used at surface mounting temperatures of 250°C by solder reflow. It has great effects if you can handle it.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a resin sealing operation of a light emitting device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the state after completion.

FIG. 3 is a side view of the light emitting device showing the state after the heat resistance test.

FIG. 4 is an enlarged view of a light emitting diode portion of the same plan view.

FIG. 5 is a sectional view showing a resin sealing operation of a light emitting device according to a second embodiment of the present invention.

FIG. 6 is a cross-sectional view showing the state after completion.

FIG. 7 is a sectional view showing an application example in which a reflective plate is provided at the bottom of the light emitting device of the present invention.

FIG. 8 is a sectional view showing another application example in which a reflector is provided at the bottom of the light emitting device of the present invention.

FIG. 9 is a cross-sectional view showing an application example in which the present invention is applied to a side lead type photodiode.

FIG. 10 is a cross-sectional view showing an example of application of the present invention to a surface-mounted photodiode.

FIG. 11 is a sectional view showing an example of application of the present invention to a ceramic stem type photodiode.

FIG. 12 is a sectional view of a light emitting device using a conventional casting method.

FIG. 13 is a perspective view of a surface-mounted light emitting device also using the transfer molding method.

FIG. 14 is a side view of the conventional light emitting device showing the state after the heat resistance test.

FIG. 15 is an enlarged view of the light emitting diode portion of the same plan view.

[Explanation of symbols]

1 Light emitting element 2 Bonding wire 3 Lead frame 4 Sealing resin body

Claims (2)

[Claims] 1. A light-emitting device comprising a light-emitting element, a lead frame on which the light-emitting element is mounted, and a translucent sealing resin body covering these, wherein during molding of the sealing resin body, A light emitting device characterized by being injection molded using a thermoplastic resin having a low coefficient of thermal expansion. [Claim 2] The thermoplastic resin according to Claim 1,
A light emitting device characterized by using thermoplastic polyimide resin.