JPH0462188B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a light emitting diode sealed with an ultraviolet curable resin.

[Technical Background of the Invention and Problems Therein] Conventionally, light emitting diodes have been sealed with a liquid epoxy resin composition or the like because they are extremely sensitive to moisture and impurities.

Resin sealing methods include the so-called potting method, which involves injecting a liquid resin composition into a transparent container, embedding the light emitting diode component up to the desired area, and then heating and curing the resin composition to integrate it. The so-called casting method, in which a container is similarly sealed and then removed from the mold, and the so-called dipping method, in which a light-emitting diode component is immersed in a resin composition, pulled up once, and the adhering resin is cured by heating. , the so-called dropping method, in which a liquid resin composition is dropped onto a desired area and cured as is.

The resin used for such resin sealing is required to have the following performance.

That is, (1) in the case of methods such as potting and casting, the resin must be of low viscosity, easy to work with during sealing, and defoaming must be accomplished in a short time.

(2) Curing shrinkage during curing must be small. If curing shrinkage is large, cracks may occur during sealing, or cracks may occur due to residual distortion due to heat shock.
Alternatively, problems such as breakage of the bonded gold wire may occur.

(3) The resulting cured product has good electrical insulation and a small coefficient of thermal expansion.

(4) The obtained cured product has good environmental resistance.

(5) It should have little discoloration due to thermal deterioration.

etc., and resin compositions containing acid anhydride-curable epoxy resins as a main component are currently widely used to satisfy these required performances.

However, since this resin is heat-curable, it takes a long time to cure, resulting in poor productivity.

That is, in the case of the casting method, for example, it takes about 60 minutes before the mold can be removed. Increasing the amount of curing agent in an attempt to shorten the curing time,
Although the use of a method of increasing the curing temperature has been considered, such a method increases internal heat generation during curing, resulting in various problems.

As a way to overcome these problems, some attempts have recently been made to use UV-curable, low-viscosity resin compositions made by adding photopolymerization initiators to unsaturated polyester, acrylic, or methacrylic resin compositions. being done.

However, when this ultraviolet curable low viscosity resin composition is used, it has been difficult to put it into practical use due to the following drawbacks.

In other words, oxygen in the air inhibits polymerization in the parts that come into contact with the air (so-called polymerization inhibition effect), resulting in the resin surface becoming sticky.In order to improve this, increasing the content of the photopolymerization initiator causes discoloration. This has resulted in a disadvantage that the light transmittance of the light emitted from the light emitting diode element becomes worse, resulting in lower reliability.

In addition, radical addition type resins inherently have large curing shrinkage, which has drawbacks such as making them more likely to crack during sealing, and causing so-called open failures in which internal distortion remains and bonding wires break. Ta.

[Purpose of the Invention] The present inventors have carried out intensive research in order to solve these problems, and as a result, the present inventors have developed a method for the reaction of a cationically polymerizable organic substance such as an epoxy resin and an allylionium salt photopolymerization initiator to a light-emitting diode. It has been found that excellent effects can be obtained when applied to resin sealing.

In other words, while the conventional acrylic ultraviolet curing reaction system is a radical addition polymerization system that causes curing shrinkage due to so-called double bonds,
The reaction system used in the present invention is a cationic polymerization reaction, which causes no curing shrinkage, can be polymerized with a small amount of photopolymerization initiator, has little discoloration of molded products due to the initiator, and can be cured uniformly. It has been found that various advantages can be obtained.

The present invention was made based on this knowledge, and can be cured in a short time, preventing discoloration, internal distortion, and
The object of the present invention is to provide a light emitting diode that is free from cracks and the like.

[Summary of the Invention] That is, the light emitting diode of the present invention is a light emitting diode element made of an ultraviolet curable low viscosity resin composition containing an epoxy resin or other cationically polymerizable organic substance and an allyl onium salt photopolymerization initiator as main components. And the lead portion is sealed with resin.

The ultraviolet curable low viscosity resin composition used in the present invention mainly contains a cationically polymerizable organic substance such as an epoxy resin and an allyl onium salt photopolymerization initiator, and optionally contains an antioxidant and other additives. A coloring agent is added.

This allyl onium salt-based photopolymerization initiator has the general formula (Ar)n-A ⁺ ·B ^- (wherein Ar: aryl group, n: 2-3, A;
I, S, Se, B; BF ₄ , PF ₆ , SbF ₆ , AsF ₆ ).

Unlike conventional diazonium salt type polymerization initiators, this allyl onium salt type photopolymerization initiator does not cause foaming or coloring of the cured product, and the pot life of the compounded resin is also good. Since it is a polymerization process, it has the advantage that oxygen in the air does not inhibit polymerization.

Note that when applying the dropping method or dipping method, an inorganic filler or a thixotropic agent may be added.

[Embodiments of the invention] Next, examples of the present invention will be described.

Embodiment The drawing is a sectional view showing an embodiment of the present invention.
In the figure, a silver paste 2 is discharged onto a reflecting plate 1 by a dispenser, and a gallium-arsenic chip 3 is mounted on top of the silver paste 2 and bonded by heating. After bonding, a gold wire 5 is connected between the chip 3 and the bonding side electrode 4.
connected by.

Next, a resin sealing composition was prepared by stirring and mixing 100 parts by weight of CX221 (trade name of epoxy resin manufactured by Chitsuso Corporation), 1.0 parts by weight of trilauryl trithiosphite, and 3.0 parts by weight of diphenyliodonium tetrafluoroborate at room temperature for 30 minutes. The resin composition was injected into a mold, and the above-mentioned element was immersed in this resin composition, and then irradiated with ultraviolet rays for 40 seconds using three 80 W/cm high-pressure mercury lamps for curing. The distance to the light source was 15 cm. Thereafter, the mold was removed to obtain a resin-sealed light emitting diode 6.

The properties of the light emitting diode encapsulated molded product thus produced were as shown in the following table, and were sufficiently durable for practical use.

Table 1 Appearance Colorless and transparent Humidity resistance No deterioration in brightness at 40°C x 95%RH x 1000h Heat resistance No deterioration in brightness at 125°C x 500h Soldering resistance Passed solder bath at 260°C for 20 seconds Current brightness deterioration 2.2V- Brightness deterioration of 30% at 25 mA x 170 hours [Effects of the invention] As explained above, the resin-sealed light emitting diode of the present invention can be cured in a short time, resulting in high productivity, and it also reduces internal distortion and cracks in the molded product. , there is no discoloration, and there is very little deterioration in brightness. Moreover, it has the advantage that thick sealing is also possible.

[Brief explanation of drawings]

The drawing is a sectional view showing an embodiment of the light emitting diode of the present invention. 1... Reflection plate, 2... Silver paste, 3... Chip, 4... Bonding side electrode, 5... Gold wire,
6...Sealing resin.

Claims (1)

[Claims] 1. A light-emitting diode element and lead portion are sealed with a UV-curable low-viscosity resin composition whose main components are an epoxy resin or other cationic polymerizable organic substance and an allyl onium salt-based photopolymerization initiator. Features a light emitting diode.