JP2002016293A - Surface-mounted type light-emitting diode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface-mounted type light-emitting diode, in which generation of crack of thermosetting resin and generation of open failure to a lead frame of an LED chip are prevented, by improving a thermal curing process of the thermosetting resin when at least the LED chip is sealed with the thermosetting resin, having light transmission property, and to provide a method for manufacturing the light-emitting diode. SOLUTION: A sealing member 60 is formed by filling an accommodation part 12 of a casing 10 with an epoxy rein and curing it thermally. The epoxy resin is formed by a heating process at 90 deg.C for two hours, a heating process at 135 deg.C for four hours and then an annealing process at 190 deg.C for four hours.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a surface mount type light emitting diode and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, as a surface mount type light emitting diode, there is one as disclosed in Japanese Patent Application Laid-Open No. 9-293904. In manufacturing this light emitting diode (hereinafter, referred to as LED), the LED chip is adhered to the inner end of the lead located on the bottom wall of the casing made of an electrically insulating resin by a silver paste, The casing is sealed by filling the casing with a sealing resin.

[0003]

By the way, the above LED
In this case, since the sealing resin is made of a transparent thermosetting resin such as an epoxy resin, if the thermosetting method of the sealing resin is inappropriate, the following problems occur.

That is, when a thermal shock is repeatedly applied to the epoxy resin in which the LED chip is sealed in the casing by thermosetting, microcracks are generated in the epoxy resin in the vicinity of the corners of the LED chip, and the epoxy resin grows and grows. The cracks reach the opening surface of the storage section. This is presumably because when the epoxy resin is rapidly cured, a residual compressive stress remains inside the epoxy resin, and the residual stress causes cracks due to repeated thermal shock.

Therefore, such a phenomenon was examined in further detail.

An epoxy resin is employed as a sealing resin, and when the epoxy resin is filled in a housing portion of a casing to seal an LED chip, the epoxy resin is sealed by a thermosetting method as shown in FIG. The epoxy resin is to be cured.

According to this thermosetting method, the epoxy resin is heated at 90 ° C. for 2 hours in the thermosetting step S1, and then heated at 135 ° C. for 4 hours in the thermosetting step S2. And cured. In this case, the temperature condition of the thermosetting step S2 is 135 ° C., which is slightly higher than the thermosetting temperature (about 120 ° C. to 130 ° C.) of the epoxy resin, and is lower than the temperature of 90 ° C. of the thermosetting step S1. The temperature difference between them is small and low.

In the case of such a thermosetting method, since the temperature of the thermosetting step S2 is low as described above, an uncured portion remains in the epoxy resin even after the curing in the thermosetting step S2, and the thermosetting step S2 It can be said that the reaction of the epoxy resin corresponding to the heat curing treatment in the above is insufficient, but the epoxy resin remains soft and is advantageous for preventing the occurrence of cracks.

However, when an LED is soldered to a printed wiring board by a flow or reflow process, the epoxy resin is heated at a high temperature (about 240 ° C.) during the soldering.
Easy to expand. For this reason, since the epoxy resin is open at the opening surface of the housing portion of the casing, the epoxy resin tends to extend toward the opening surface of the housing portion due to its thermal expansion. When the LED chip receives such an extension effect due to the thermal expansion of the epoxy resin, the LED chip is pulled by the epoxy resin toward the opening surface of the housing portion and is an adhesive portion with the inner end of the lead of the LED chip. Open failure occurs in the silver paste part.

If the epoxy resin is cured by a thermosetting method as shown in FIG.
The epoxy resin is heated at 90 ° C. for 2 hours in the thermosetting step S1, and then heated and cured at 195 ° C. for 4 hours in the thermosetting step S3.
In this case, the temperature condition of the thermosetting step S3 is 190 ° C., and the temperature difference between the temperature setting of the thermosetting step S1 and 90 ° C. is large and high.

In the case of such a thermosetting method, since the temperature of the thermosetting step S3 is high as described above, the epoxy resin is hardened without leaving an uncured portion after being cured in the thermosetting step S3. This is advantageous for preventing the occurrence of open failure as described above, but the temperature rises sharply from a low temperature in the thermosetting step S1 to a high temperature in the thermosetting step S3. Residual stress is generated in the resin, which tends to cause the above-described crack.

When this point was examined in detail,
If the temperature of the heat curing step S3 is high, the vicinity of the surface of the epoxy resin starts to cure faster than the inside. For this reason, the surface of the epoxy resin is in a hard state and the inside is in a soft state, and there is a difference in the cured state between the surface and the inside of the epoxy resin. Then, although the epoxy resin finally hardens to the inside, the above-mentioned compressive residual stress is generated inside the epoxy resin. This causes the crack to occur.

Therefore, in order to cope with the above, the present invention devises a thermosetting process of the thermosetting resin in sealing at least the LED chip with a translucent thermosetting resin. It is another object of the present invention to provide a surface-mounted light emitting diode that prevents cracks in the thermosetting resin and open defects between the LED chip and a lead frame, and a method of manufacturing the same.

[0014]

In order to solve the above-mentioned problems, a surface-mounted light-emitting diode according to the first aspect of the present invention has a housing portion (12) which is opened outward at an upper wall (11). Is formed in a concave shape, and a casing (10) made of an electrically insulating resin, and one side portion (1
3) a lead frame (20) made of a metal material extending from the inner end (21) along the bottom surface (12b) into the housing portion, and the other side portion (15) of the peripheral wall of the casing. ) Is formed from a metal material and has an inner end (31) extending into the housing portion along the bottom surface thereof so as to face the inner end of the one-side lead frame (30). And a conductive adhesive layer (5) on the inner end of one (30) of both lead frames housed in the housing section.
0) and a translucent thermosetting resin that fills the housing and seals the LED chip, the inner ends of both lead frames, and the conductive adhesive layer. A sealing member (60).

In the surface mount type light emitting diode,
The sealing member heats the thermosetting resin at a temperature slightly lower than the thermosetting temperature for a tentative curing time, and thereafter, the thermosetting resin is fully cured at a temperature slightly higher than the thermosetting temperature. Then, the thermosetting resin is annealed at a temperature slightly lower than the soldering temperature of both lead frames for an annealing time.

Accordingly, the heating temperature of the thermosetting resin is:
The heating temperature during temporary hardening does not suddenly increase from the heating temperature during temporary curing to the heating temperature during annealing, but rather increases from the heating temperature during temporary curing to the heating temperature during annealing through the intermediate heating temperature of the heating temperature during main curing.

As described above, when the heating temperature of the thermosetting resin rises from the temperature at the time of temporary curing to the temperature at the time of annealing, the uncured portion of the thermosetting resin is generated, and the LED chip and the lead frame are hardened. The occurrence of an open defect with the end can be prevented beforehand. In addition, as described above, the heating temperature of the thermosetting resin is increased in three stages with an intermediate temperature therebetween, so that the thermosetting resin is slowly thermoset. Therefore, the above-mentioned compressive residual stress does not occur inside the thermosetting resin, and as a result, cracks do not occur in the thermosetting resin.

According to the second aspect of the present invention, in the first aspect, the thermosetting resin is a translucent epoxy resin, and the temperature slightly lower than the thermosetting temperature is 90 ° C.
The temperature slightly higher than the thermosetting temperature is 135 ° C., the temperature slightly lower than the soldering temperature is 190 ° C., the temporary curing time is 2 hours, and the main curing time and the annealing time are both: It is 4 hours.

Thus, the function and effect of the invention described in claim 1 can be more reliably achieved.

According to the third aspect of the present invention, the casing (10) made of an electrically insulating resin is formed such that the accommodation portion (12) is formed in a concave shape so as to open outward on the upper wall (11).
And a one-sided lead frame (20) made of a metal material which is inserted into the casing from one side (13) of its peripheral wall and extends into the housing along the bottom surface (12b) at the inner end (21). And the other side of the peripheral wall (1
5) The other lead frame (30) made of a metal material having an inner end (31) inserted into the housing portion and extending along the bottom surface thereof so as to face the inner end of the one lead frame. ) And an LED chip (40) housed in the housing part and mounted on the inner end of one of the two lead frames (30) via a conductive adhesive layer (50). A sealing member (6) is filled with a translucent thermosetting resin and thermally cured so as to seal the chip, the inner ends of both lead frames and the conductive adhesive layer.
0), the sealing member is heated at a temperature slightly lower than the thermosetting temperature of the thermosetting resin for a temporary curing time, and then the thermosetting resin is heated. That the thermosetting resin is fully cured at a temperature slightly higher than its thermosetting temperature, and then the thermosetting resin is annealed at a temperature slightly lower than the soldering temperature of both lead frames for an annealing time. Features.

This makes it possible to manufacture a surface-mounted light emitting diode that can achieve the functions and effects of the first aspect of the present invention.

According to a fourth aspect of the present invention, in the third aspect, the thermosetting resin is a translucent epoxy resin, and the temperature slightly lower than the thermosetting temperature is 90 ° C.
The temperature slightly higher than the thermosetting temperature is 135 ° C., the temperature slightly lower than the soldering temperature is 190 ° C., the temporary curing time is 2 hours, and the main curing time and the annealing time are both: It is 4 hours.

According to the fifth aspect of the present invention, the LED chip, the inner ends of both the lead frames, and the conductive adhesive layer are sealed in the accommodation portion of the LED body according to the third aspect. In a method of manufacturing a surface-mounted light-emitting diode by filling a translucent thermosetting resin and thermosetting to form a sealing member (60), the sealing member is made of a thermosetting resin. The heating is performed for a predetermined time from a temperature slightly lower than the thermosetting temperature to a temperature slightly lower than the soldering temperature of both lead frames.

According to this, substantially the same operation and effect as those of the third aspect can be achieved.

The reference numerals in parentheses of the above means indicate the correspondence with specific means described in the embodiments described later.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. 1 and 2 show an embodiment of a surface-mounted LED according to the present invention. This LED includes a rectangular parallelepiped casing 10 made of an electrically insulating resin (for example, a high heat-resistant polymer having a glass transition temperature of 110 ° C. such as a white epoxy resin containing glass or a polyphthalic acid containing white glass). In addition, a housing portion 12 is formed in a concave shape on an upper wall 11 of the casing 10. The housing portion 12 opens outward from the upper wall 11 of the casing 10 at the opening 12a, and the bottom surface 12b of the housing portion 12 is parallel to the upper wall 11. Further, the inner peripheral surface 12c of the housing portion 12 is slightly tapered from the opening 12a to the bottom surface 12b in order to increase the light reflection efficiency.

The LED includes two plate-shaped lead frames 20 and 30 made of a metal material. The two lead frames 20 and 30 are arranged in a casing 10 so as to have a structure as shown in FIG. Insert molded. Note that, instead of the above metal material, both lead frames 2 are made of a conductive elastic material (for example, a conductive spring material).
0 and 30 may be formed.

Here, the lead frame 20 constitutes the anode of the LED.
The housing portion 1 is inserted into the casing 10 from one side wall 13 thereof.
2 are inserted along the bottom surface 12b. The inner end 21 of the lead frame 20 extends into the housing portion 12 along the bottom surface 12b.

On the other hand, the lead frame 30 constitutes the cathode of the LED.
It is inserted into the casing 10 from the other side wall 15 along the bottom surface 12 b of the housing 12. The inner end 31 of the lead frame 30 has its bottom surface 1
It extends along 2b and faces the inner end 21 of the lead frame 20 via the partition 14 of the casing 10. Also,
The partition wall 14 is formed on the bottom surface 12 b of the housing 12 of the casing 10.
The partition wall 14 is formed so as to protrude between the inner end portions 21 and 31, and the partition wall 14 serves to electrically insulate the inner end portions 21 and 31 of the lead frames 20 and 30 from each other.

The lead frame 20 extends from one side wall 13 of the casing 10 to the outside (hereinafter referred to as a leg portion 22) of the lower wall 16 of the casing 10 from the one side wall 13. In FIG. 1, the lead frame 20 is bent toward the left end in the drawing, and the lead frame 20 is soldered 22b to the wiring portion of the wiring board P such as a printed board at the outer end 22a (the tip of the leg 22). Have been.

On the other hand, the lead frame 30 extends from the other side wall 15 of the casing 10 to the lower wall 16 of the casing 10 at a portion extending outward from the other side wall 15 of the casing 10 (hereinafter referred to as a leg 32). The lead frame 30 is bent to the right end in FIG. 1 and soldered 32b to another wiring portion of the wiring board P at an outer end portion 32a (a distal end portion of the leg portion 32). I have. Thus, the LED is surface-mounted on the wiring board P. The surface mounting by the two solders 22b and 32b is performed by a flow or reflow process.

The LED is provided with an LED chip 40, which is housed in the housing section 12 and provided with a silver paste layer 50 by means of a silver paste layer 50.
0 is adhered to the surface of the inner end 31. The LED chip 40 has a compound semiconductor chip forming a PN junction, and the LED chip 40 emits light toward the opening surface side of the housing portion 12 by flowing a current in the forward direction through the PN junction. I do. The silver paste layer 50 plays a role of electrically connecting the negative electrode of the LED chip 40 to the inner end 31 of the lead frame 30. Also, the LED chip 40
Is connected to the lead frame 20 by the gold wire 41 at its positive electrode.
Are electrically connected to the inner end portion 21 of the main body.

The housing member 12 has a sealing member 60 therein.
Is formed by thermosetting by filling with a sealing potting resin (for example, a transparent epoxy resin), and the sealing member 60 is formed of the LED chip 40, the gold wire 41, and each of the lead frames 20 and 30. It seals in the accommodation part 12 so that the inner ends 21 and 31 may be covered.

In the embodiment configured as described above, a method of manufacturing the LED will be described. First, a portion of the LED shown in FIG. 1 having a configuration other than the sealing member 60 (hereinafter, referred to as an LED main body) is manufactured. Thereafter, the housing 12 of the casing 10 is filled with a transparent epoxy resin. This filling is performed by the LED chip 40, the gold wire 4
1 and the inner ends 21, 3 of both lead frames 20, 30
1 to cover.

After such filling, the thermosetting treatment of the epoxy resin in the casing 10 is performed as follows in the thermosetting step shown in FIG. First, the LED main body in which the epoxy resin is filled in the housing section 12 as described above is heated at 90 ° C. for 2 hours (temporary curing time) in the thermosetting step S1 of FIG. Thereby, the epoxy resin is temporarily cured.

Thereafter, in the heat curing step S2, the LED main body having the above-mentioned structure is heated at 135 ° C. for 4 hours (main curing time).
During the heat curing step S3 in FIG.
Heat at 190 ° C. for 4 hours (annealing time). Thereby, the epoxy resin is annealed after being fully cured.

As described above, in the present embodiment, the thermosetting treatment of the epoxy resin is different from the two-stage thermosetting process of FIG. 4A and the two-stage thermosetting process of FIG. As shown in FIG. 2, the process is performed through a three-stage thermosetting process incorporating the advantages of both processes of FIGS. 4 (a) and 4 (b). Therefore, the heating temperature of the epoxy resin does not rapidly rise from 90 ° C to 190 ° C, but rises to 190 ° C via an intermediate heating temperature of 90 ° C to 135 ° C. Thus, in the thermosetting step S3, an annealing process is performed on the epoxy resin.

Therefore, the heating temperature of the epoxy resin is 90 ° C.
4A, the uncured portion of the epoxy resin is generated when the epoxy resin is heat-treated in the two-step heating process of FIG.
Silver paste 5 between the lead frame 30 and the inner end of the lead frame 30
The occurrence of an open defect of 0 can be prevented beforehand. Further, as described above, the heating temperature of the epoxy resin is set at 2 in FIG.
The heating temperature of the epoxy resin is increased from 90 ° C. to 190 ° C. through an intermediate heating temperature of 135 ° C. without rapidly increasing the temperature from 90 ° C. to 190 ° C. as in the thermal curing step.
Up to Therefore, the epoxy resin is gently thermally cured, so that the above-mentioned compressive residual stress does not occur inside the epoxy resin, and as a result, cracks do not occur in the epoxy resin.

Thus, according to the present embodiment, it is possible to manufacture a surface-mounted LED which can reliably prevent the occurrence of uncured portions of the epoxy resin, the occurrence of open defects in the silver paste 50, and the occurrence of cracks in the epoxy resin. It becomes possible.

The LED manufactured in this manner is
In the flow or reflow process, the circuit board P is soldered as shown in FIG. In this case, the heating temperature at the time of soldering by the flow or reflow treatment is a temperature close to the heating temperature of 190 ° C. in the thermosetting step S3 and the temperature at which the epoxy resin does not turn yellow. The epoxy resin does not yellow.

By the way, the case where a large number of LEDs having the above configuration are manufactured through the thermosetting process of FIG. 2 described in the present embodiment, and the case where each LED is formed by the thermosetting process of FIGS. 4 (a) and 4 (b) When the above open defect and crack defect in the case of manufacturing through each process were examined, the result as shown in FIG. 3 was obtained. According to this, in each LED in the conventional thermosetting process of FIG. 4A, the crack failure did not occur, but the open failure occurred. Further, in each LED in the conventional thermosetting process of FIG. 4B, the above-mentioned open failure did not occur, but the above-mentioned crack failure occurred. On the other hand, in the LED according to the present embodiment, neither the open failure nor the crack failure occurred. The thermal shock repetition for examining the crack generation was carried out between 40 ° C. and 100 ° C. for 15 minutes.
It was performed 00 times.

In the practice of the present invention, even if a conductive adhesive layer, for example, an adhesive layer obtained by mixing conductive particles with an adhesive resin is employed in place of the silver paste layer 50, the above-mentioned open defect can be prevented. This is the same as the case of the silver paste layer 50.

In practicing the present invention, the heating temperature in the thermosetting step S1 described in the above embodiment is 90 ° C. ±
The heating temperature in the thermosetting step S2 may be a temperature within a range of ± 10 ° C. of the curing temperature of the epoxy resin. The heating temperature in the thermosetting step S3 may be a temperature slightly lower than the temperature at which the LED is mounted on the wiring board P by the reflow or flow processing. The heating time in the thermosetting step S1 may be one hour or more as the temporary curing time of the epoxy resin.
The heating time in step S3 may be at least 3 hours as the main curing time of the epoxy resin, and the heat curing time in the heat curing step S3 may be at least 3 hours as the annealing time of the epoxy resin.

In practicing the present invention, the temperature in each of the thermosetting steps described in the above embodiment, 90 ° C., 135 ° C.
And 190 ° C., even if the heating temperature changes continuously from 90 ° C. to 190 ° C. instead of stepwise, it is possible to achieve substantially the same operation and effect as in the above embodiment. In this case, due to the heating time at each temperature, the temporal gradient of the temperature rise is 135 ° C. between 90 ° C. and 135 ° C.
Less than between ° C and 190 ° C. After reaching 190 ° C., the temperature is maintained for 4 hours.

In implementing the present invention, the inner peripheral wall of the housing 12 of the casing 10 has the same cross-sectional shape from the bottom surface 12b to the opening 12a, unlike the case described in each of the above embodiments. You may.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a view illustrating a thermosetting process of an epoxy resin of the LED of FIG. 1;

FIG. 3 is a table comparing the LED manufactured through the thermosetting process and the LED manufactured through each of the conventional thermosetting processes of FIGS.

FIGS. 4A and 4B are diagrams showing a conventional thermosetting process.

[Explanation of symbols]

10 ... casing, 11 ... upper wall, 12 ... accommodation part, 13 ...
One side wall, 15 ... Other side wall, 20, 30 ... Lead frame, 21, 31 ... Inner end, 40 ... LED chip, 5
0: silver paste layer, 60: sealing member.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiromasa Shibata 1-1-1 Showa-cho, Kariya-shi, Aichi F-term in DENSO Corporation (reference) 4M109 AA01 BA01 CA02 EA02 EC11 GA01 5F041 AA41 CA73 DA02 DA12 DA17 DA44 DA74 DA78 DB09 DC23 DC66 5F061 AA01 BA01 CA21 CB13 FA01

Claims (5)

[Claims] 1. A casing (10) made of an electrically insulating resin having a recess (12) formed so as to open outward on an upper wall (11), and one side of a peripheral wall of the casing. A lead frame (20) made of a metal material which is inserted from (13) and extends into the housing portion along the bottom surface (12b) of the inner end portion (21); An inner end (31) inserted from the portion (15) and extending into the housing along the bottom surface thereof so as to face the inner end of the one-side lead frame;
Lead frame (3) made of a metal material having
0), an LED chip (40) housed in the housing part and mounted on the inner end of one (30) of the two lead frames via a conductive adhesive layer (50), and filled in the housing part. And a sealing member (60) made of a translucent thermosetting resin for sealing the LED chip, the inner ends of both lead frames and a conductive adhesive layer. The sealing member heats the thermosetting resin at a temperature slightly lower than the thermosetting temperature for a tentative curing time, and then fully cures the thermosetting resin at a temperature slightly higher than the thermosetting temperature. Then, the thermosetting resin is annealed at a temperature slightly lower than the soldering temperature of the two lead frames for an annealing time, and is a surface-mounted light emitting diode. 2. The thermosetting resin is a translucent epoxy resin, a temperature slightly lower than the thermosetting temperature is 90 ° C., a temperature slightly higher than the thermosetting temperature is 135 ° C., The temperature slightly lower than the soldering temperature is 190
2. The surface-mounted light emitting diode according to claim 1, wherein the temporary curing time is 2 hours, and the main curing time and the annealing time are both 4 hours. 3. An electrically insulating resin casing (10) having a recess (12) formed so as to open outward on the upper wall (11), and one side of a peripheral wall of the casing. (13) and is inserted into the housing portion at its bottom surface (1).
A one-side lead frame (20) made of a metal material extending along an inner end portion (21) along 2b), and a bottom surface inserted into the casing from the other side portion (15) of the peripheral wall and inserted into the housing portion; And a second lead frame (30) made of a metal material having an inner end (31) extending so as to face the inner end of the one-side lead frame. One of the two lead frames (3
The LED chip, the respective inner ends of the two lead frames and the conductive material are disposed in the housing portion of the LED body having the LED chip (40) mounted on the inner end of the LED frame via the conductive adhesive layer (50). A method of manufacturing a surface-mounted light-emitting diode by filling a light-transmitting thermosetting resin and thermosetting to form a sealing member (60) so as to seal the adhesive layer. The member is heated for a temporary curing time at a temperature slightly lower than the thermosetting temperature of the thermosetting resin, and thereafter, the thermosetting resin is fully cured at a temperature slightly higher than the thermosetting temperature, Then, the thermosetting resin is annealed at a temperature slightly lower than the soldering temperature of the two lead frames for an annealing time. 4. The thermosetting resin is a translucent epoxy resin, a temperature slightly lower than the thermosetting temperature is 90 ° C., a temperature slightly higher than the thermosetting temperature is 135 ° C., The temperature slightly lower than the soldering temperature is 190
4. The method of claim 3, wherein the temporary curing time is 2 hours, and the main curing time and the annealing time are both 4 hours. 5. 5. An electrically insulating resin casing (10) having a recess (12) formed so as to open outward on an upper wall (11), and one side of a peripheral wall of the casing. (13) and is inserted into the housing portion at its bottom surface (1).
A one-side lead frame (20) made of a metal material extending along an inner end portion (21) along 2b), and a bottom surface inserted into the casing from the other side portion (15) of the peripheral wall and inserted into the housing portion; And a second lead frame (30) made of a metal material having an inner end (31) extending so as to face the inner end of the one-side lead frame. One of the two lead frames (3
The LED chip, the respective inner ends of the two lead frames and the conductive material are disposed in the housing portion of the LED body having the LED chip (40) mounted on the inner end of the LED frame via the conductive adhesive layer (50). A method of manufacturing a surface-mounted light-emitting diode by filling a light-transmitting thermosetting resin and thermosetting to form a sealing member (60) so as to seal the adhesive layer. Wherein the member is heated for a predetermined time from a temperature slightly lower than the thermosetting temperature of the thermosetting resin to a temperature slightly lower than the soldering temperature of the two lead frames. Production method.