阅读说明：本技术 发光器件及其封装方法 (Light emitting device and method of packaging the same ) 是由 H·L·潘 H·S·尤 X·严 于 2019-11-14 设计创作，主要内容包括：一种发光器件(100A),包括：引线框架(110),其包括彼此间隔开的管芯焊盘(111)和引线(112)；发光管芯(120),其附接在管芯焊盘(111)上；导线(130),其将发光管芯(120)接合到引线(112),其中导线(130)的第一端(131)和发光管芯(120)的与导线(130)的第一端(131)接合的区域形成第一颈缩区(141)；第一树脂盖(150a),其覆盖第一颈缩区(141)；以及第二树脂盖(160),其覆盖第一树脂盖(150a)、发光管芯(120)和导线(130)。第一树脂盖(150a)的硬度低于第二树脂盖(160)的硬度。(A light emitting device (100A) comprising: a lead frame (110) including a die pad (111) and a lead (112) spaced apart from each other; a light emitting die (120) attached on the die pad (111); a wire (130) bonding the light emitting die (120) to the lead (112), wherein a first end (131) of the wire (130) and a region of the light emitting die (120) bonded to the first end (131) of the wire (130) form a first necked down region (141); a first resin cover (150 a) covering the first necked-down region (141); and a second resin cover (160) covering the first resin cover (150 a), the light emitting dice (120), and the wires (130). The first resin cover (150 a) has a lower hardness than the second resin cover (160).)

1. A light emitting device (100A) comprising:

a lead frame (110), the lead frame (110) including a die pad (111) and leads (112) spaced apart from each other;

a light emitting die (120), the light emitting die (120) being attached on the die pad (111);

a wire (130), the wire (130) bonding the light emitting die (120) to the lead (112), wherein a first end (131) of the wire (130) and a region of the light emitting die (120) bonded to the first end (131) of the wire (130) form a first necked down region (141);

a first resin cover (150 a), the first resin cover (150 a) covering only the first necked-down region (141); and

a second resin cover (160), the second resin cover (160) directly covering the first resin cover (150 a), the light emitting dies (120), and the wires (130),

wherein the first resin cover (150 a) has a lower hardness than the second resin cover (160).

2. The light emitting device (100B) according to claim 1,

wherein the second end (132) of the wire (130) and a region of the lead (112) joined to the second end (132) of the wire (130) form a second necked-down region (142),

wherein the light emitting device (100B) further comprises another first resin cap (150B) covering the second necked-down region (142), and

wherein the second resin cover (160) further covers the other first resin cover (150 b).

3. The light-emitting device (100A) according to claim 1, wherein the first resin cover (150A) is made of silicone.

4. The light emitting device (100B) according to claim 2, wherein the further first resin cover (150B) is made of silicone.

5. The light-emitting device (100A) according to claim 3, wherein the silicone resin has a dynamic viscosity in a range of 1 to 8 Pa-s before curing.

6. A light emitting device (100A) according to claim 3, wherein said silicone has a hardness after curing of 30A to 70D on the shore hardness scale.

7. The light emitting device (100A, 100B) according to claim 1, wherein the second resin cover (160) is made of epoxy resin.

8. The light emitting device (100A, 100B) according to any one of claims 1-7, wherein the light emitting die (120) is a light emitting diode die.

9. The light emitting device (100A, 100B) according to any one of claims 1-7, wherein a transmittance of the first resin cover (150A) is lower than a transmittance of the second resin cover (160).

10. A method (300) of packaging a light emitting device (100A), the light emitting device (100A) comprising a lead frame (110) and a light emitting die (120), the lead frame (110) comprising a die pad (111) and leads (112) spaced apart from each other, the light emitting die (120) being attached on the die pad (111), the method (300) comprising:

bonding (330) the light emitting die (120) to the lead (112) with a wire (130), wherein a first end (131) of the wire (130) and a region of the light emitting die (120) bonded to the first end (131) of the wire (130) form a first necked down region (141);

covering (340) only the first necked-down region (141) with a first resin cover (150 a); and

forming (350) a second resin cover (160) directly on the first resin cover (150 a), the light emitting dice (120), and the wires (130) to seal the first resin cover (150 a), the light emitting dice (120), and the wires (130), wherein a hardness of the first resin cover (150 a) is lower than a hardness of the second resin cover (160).

11. The method (300) of claim 10, wherein the second end (132) of the wire (130) and a region of the lead (112) joined to the second end (132) of the wire (130) form a second necked-down region (142), and wherein the method (300) further comprises covering the second necked-down region (142) with another first resin cover (150 b).

12. The method (300) of claim 10, wherein said covering (340) the first necked down region (141) comprises dispensing silicone at the first necked down region (141).

13. The method (300) of claim 10, wherein said forming (350) the second resin cover (160) comprises molding or casting an epoxy over the first resin cover (150 a), the light emitting die (120), and the wires (130).

14. The method (300) of claim 11, wherein said covering the second necked-down region (142) comprises dispensing silicone at the second necked-down region (142).

15. The method (300) of claim 11, wherein said forming (350) the second resin cover (160) comprises molding or casting an epoxy over the first resin cover (150 a), the further first resin cover (150 b), the light emitting die (120), and the wires (130).

Technical Field

The present invention relates to a wire-bonded product, and more particularly, to a light emitting device and a method of packaging the same.

Background

Wire bonding, which is common in the electronics industry, provides electrical connection for the chip to external circuitry. Typically, thin wires are connected between the electronic chip and the metal lead frame to make electrical connection.

For optical devices, such as light emitting diodes, a transparent resin without any filler is generally used to encapsulate a chip due to its light transmission efficiency. However, transparent resins (such as epoxy resins without fillers) harden and become brittle after curing. When the packaged chip is exposed to thermal shock, the difference in the Coefficients of Thermal Expansion (CTE) of the metal and resin can cause pull/push stresses on the bonded wires. This effect becomes greater as the optical resin becomes harder.

US 6710377B2 discloses a light emitting device comprising a semiconductor light emitting element and a silicone resin provided to embed the semiconductor light emitting element. Using silicone resin as the resin for sealing the semiconductor light emitting element instead of using conventional epoxy resin can reduce the possibility of wire breakage.

Disclosure of Invention

Despite the ability of existing devices to resist wire breakage, there remains a need for light emitting devices with improved optical properties and/or mechanical strength.

According to an aspect of the present invention, there is provided a light emitting device including: a lead frame including a die pad and a lead spaced apart from each other; a light emitting die attached on the die pad; a wire bonding the light emitting die to the lead, wherein a first end of the wire and a region of the light emitting die to which the first end of the wire is bonded form a first necked down region; a first resin cover covering the first necked-down region; and a second resin cover covering the first resin cover, the light emitting dice, and the wires, wherein a hardness of the first resin cover is lower than a hardness of the second resin cover.

By using the first resin to cover only the necked region, rather than the entire die and wire, it is desirable to improve the optical properties of the device while still providing the desired mechanical strength. On the one hand, the first (softer) resin, such as silicone, will provide a cushion for mechanical deformation during thermal shock, thereby protecting the wires from harsh stresses that could easily lead to breakage. In this sense, even the mechanical strength can be improved, since the interface between the first (softer) resin and the second (harder) resin is smaller, and thus less stress will be generated, than in the case where the soft resin covers the entire die and the wires and then the hard resin covers the soft resin. On the other hand, covering only the necked region with the first softer resin means that most of the light emitting region of the die remains uncovered by the soft resin. Thus, most of the light leaving the light emitting die enters the second resin directly, without having to pass through the first resin first. This has at least two advantages: 1) since hard resins generally have optical properties superior to those of soft resins, in particular better transparency, less light is absorbed; and 2) since the boundary between the soft resin and the hard resin is reduced, less light must pass through such boundary, and loss of absorption and refraction upon such passage is reduced. Thus, the optical properties of the light emitting device may be improved, e.g. more light may be coupled out of the light emitting die.

In some embodiments, the second end of the wire and the region of the lead to which the second end of the wire is bonded form a second necked down region. In this case, the light emitting device may further include another first resin cap covering the second necked region, and the second resin cap may further cover the another first resin cap. This provides improved reliability by reducing the risk of breakage at the second end of the wire.

In some embodiments, the first resin cover(s) is made of silicone. In some embodiments, the silicone resin has a dynamic viscosity in the range of 1 to 8Pa · s prior to curing. Preferably, the silicone resin can be cured at room temperature. In some embodiments, the hardness of the cured first resin may be in the range of 30A to 70D (measured on a durometer scale on the shore hardness scale a and D as indentation hardness).

In some embodiments, the second resin cover is made of epoxy. The term epoxy resin as used herein is the popular name for epoxy functional groups. Epoxy resins, also known as polyepoxides, are a class of reactive prepolymers and polymers containing epoxy groups.

In some embodiments, the light emitting die is a Light Emitting Diode (LED) die. As used herein for the purposes of the present invention, the term "LED" should be understood to include any electroluminescent diode or other type of carrier injection/junction-based system capable of generating radiation in response to an electrical signal. Thus, the term LED includes, but is not limited to, various semiconductor-based structures that emit light in response to an electrical current, light emitting polymers, Organic Light Emitting Diodes (OLEDs), electroluminescent strips, and the like. In particular, the term LED refers to all types of light emitting diodes (including semiconductor light emitting diodes and organic light emitting diodes) that may be configured to generate radiation in one or more of the various portions of the infrared, ultraviolet, and visible spectrums (typically including radiation wavelengths from about 400 nanometers to about 700 nanometers).

According to another aspect of the present invention, there is provided a method of packaging a light emitting device. The light emitting device includes a lead frame including a die pad and leads spaced apart from each other, and a light emitting die attached on the die pad. The method comprises the following steps: bonding the light emitting die to the lead with a wire, wherein a first end of the wire and a region of the light emitting die to which the first end of the wire is bonded form a first necked down region; covering the first necked-down region with a first resin cap; and forming a second resin cover to seal the first resin cover, the light emitting dice and the wires, wherein the first resin cover has a lower hardness than the second resin cover.

These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiment(s) described hereinafter.

Drawings

Further details, features and advantages of the invention are disclosed in the following description of exemplary embodiments with reference to the accompanying drawings, in which:

fig. 1 is a schematic cross-sectional view of a light emitting device according to an embodiment of the present invention;

fig. 2 is a schematic cross-sectional view of a light emitting device according to another embodiment of the present invention; and

fig. 3 is a flowchart illustrating a method of packaging a light emitting device according to an embodiment of the present invention.

The drawings are not necessarily to scale. Like reference numerals refer to like elements throughout.

Detailed Description

It will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention.

Spatially relative terms, such as "below," "lower," "below," "upper," "above," and the like, may be used herein to facilitate describing one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary terms "below" and "beneath" can encompass both an orientation of "above" and "below". For example, terms such as "front" or "before" and "back" or "after" may be similarly used to indicate the order in which light passes through the elements. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

It will be understood that when an element or layer is referred to as being "on," "connected to," "coupled to" or "adjacent to" another element or layer, it can be directly on, connected to, coupled to or adjacent to the other element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on," "directly connected to," "directly coupled to" or "directly adjacent to" another element or layer, there are no intervening elements or layers present. However, in any event, "on … …" or "directly on … …" should not be construed as requiring one layer to completely cover an underlying layer.

Embodiments of the present invention are described herein with reference to schematic illustrations of idealized embodiments (and intermediate structures) of the present invention. Variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments of the invention should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of the invention.

Unless defined otherwise, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and/or the present specification and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

Fig. 1 shows a schematic cross-sectional view of a light emitting device 100A according to an embodiment of the present invention.

The light emitting device 100A includes a lead frame 110, a light emitting die 120, a wire 130, a first resin cover 150A, and a second resin cover 160.

The lead frame 110 includes a die pad 111 to which the light emitting die 120 is attached, and leads 112 spaced apart from the die pad 111. The die pad 111 provides mechanical support for the light emitting die 120 and additionally provides heat dissipation. The leads 112 allow the light emitting die 120 to be contacted to external circuitry (e.g., a power supply), among possibly other leads.

The light emitting die 120 is attached to the die pad 111 by an adhesive 170, such as silver (Ag) paste. The light emitting die 120, such as an LED die, may have an electrode (not shown) on its surface that is connected to the lead 112 by a bonding wire 130, such as a gold (Au) wire, where a first end 131 of the wire 130 is connected to the electrode of the light emitting die 120 and a second end 132 of the wire 130 is connected to the lead 112.

As shown in fig. 1, the first end 131 of the wire 130 and the region of the light emitting die 120 to which the first end 131 of the wire 130 is bonded form a first necked-down region 141, and in practice, the first necked-down region 141 is particularly susceptible to fracture due to the difference in CTE between the metal electrode and the sealing resin. In the present embodiment, a first resin cover 150a is provided to cover the first necked region 141, and a second resin cover 160 is provided to cover the first resin cover 150a, the light emitting die 120 and the wire 130. The first resin cover 150a is made of, for example, silicone, and is softer than the second resin cover 160. In some embodiments, the first resin cover 150A has a hardness in the range of 30A to 70D (measured as indentation hardness on the durometer scale on shore hardness scale a and D), and the second resin cover 160 has a hardness higher than that of the first resin cover 150A. Therefore, the first resin cover 150a may provide a buffer for mechanical deformation during thermal shock. The second resin cover 160 is made of, for example, epoxy resin, and thus provides superior optical properties (e.g., higher transmittance) than the first resin cover 150 a. Advantageously, the configuration of the first and second resin covers 150a, 160 provides a compromise between mechanical strength and optical properties.

Fig. 2 shows a schematic cross-sectional view of a light emitting device 100B according to another embodiment of the present invention. For the sake of brevity, the same configuration as that of the above-described light emitting device 100A with respect to fig. 1 is not repeated here.

As shown in fig. 2, the second end 132 of the wire 130 and the region of the lead 112 to which the second end 132 of the wire 130 is bonded form a second necked-down region 142, and the second necked-down region 142 is also susceptible to fracture due to the difference in CTE between the metal lead 112 and the sealing resin 160. In the present embodiment, another first resin cover 150b made of, for example, the same silicone resin as the first resin cover 150a is provided to cover the second necked region 142, and the second resin cover 160 further covers the other first resin cover 150b accordingly. This further reduces the risk of breakage at the second end 132 of the wire 130, resulting in improved reliability of the light emitting device 100B.

Fig. 3 is a flowchart illustrating a method 300 of packaging a light emitting device according to an embodiment of the present invention. The method 300 may be used to package the light emitting device 100A and/or the light emitting device 100B, and is described further below with reference to fig. 1 and 2.

At step 310, the light emitting die 120 is attached to the die pad 111 of the lead frame 110. Specifically, the die pad 111 is coated with an adhesive 170 such as silver (Ag) paste, and then the die 120 is bonded on the die pad 111 by the silver paste.

At step 320, the silver paste is cured. This may be, for example, nitrogen (N) at 175 deg.C₂) The atmosphere lasted for one hour.

At step 330, light emitting die 120 is wire bonded to wire 112 with wire 130. This can be accomplished by typical wire bonding processes used in the integrated circuit industry. Thus, the first necked-down region 141 is formed by the first end 131 of the wire 130 and the region of the light emitting die 120 to which the first end 131 of the wire 130 is bonded, and the second necked-down region 142 is formed by the second end 132 of the wire 130 and the region of the lead 112 to which the second end 132 of the wire 130 is bonded.

At step 340, the first necked-down region 141 is covered with a first resin cover 150 a. Specifically, a dispenser (e.g., a needle) is used to dispense (distense) a small amount of a first resin (such as silicone) at the first necked region 141. The silicone resin may have a dynamic viscosity in the range of, for example, 1 to 8Pa · s (Pa · s stands for "pascal times second") before curing. The amount of resin dispensed can be controlled by the dispenser such that the resin stays where it is dispensed to form a hemispherical shape without spreading to coat the entire surface of the light emitting die 120. In some embodiments, the second necked-down region 142 is also covered with the first resin cover 150 b. This may be done in the same manner as the first resin cover 150a is formed. The first resin dispensed at the first necked region 141 (and potentially the second necked region 142) is then cured by a suitable curing process (e.g., wetting or heating). In some embodiments, the first resin may be cured by first baking at 80 ℃ for two hours and then baking at 150 ℃ for three hours in an oven. Preferably, the first resin may be selected such that it can be cured at room temperature. Other embodiments are possible as long as the light emitting die 120 is able to withstand the curing process used. In some embodiments, the cured first resin has a hardness in the range of 30A to 70D (measured as indentation hardness on a durometer on the shore hardness scale a and D).

At step 350, a second resin cover 160 is formed to seal the first resin cover 150a, the light emitting dice 120 and the wires 130. In an embodiment where the first resin cover 150b is formed at the second necked-down region 142, the second resin cover 160 is formed such that it also seals the first resin cover 150 b. Step 350 may be accomplished by a typical hard resin forming process (e.g., molding or casting). As shown in fig. 1 and 2, the second resin cover 160 surrounds the light emitting die 120 and the wires 130 (including the first resin covers 150a, 150 b).

In an embodiment, after step 350, the resulting light emitting device may be further processed with subsequent processes, such as post-mold curing (PMC), deflashing, plating, annealing, and the like, which are not described in detail herein, so as not to obscure the subject matter of the present invention.

Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Reference numerals

100A, 100B light emitting device of the invention

110 lead frame

111 die pad

112 lead wire

120 light emitting die

130 wire

131 first end of wire

132 second end of conducting wire

141 first necked down region

142 second necked down region

150a first resin cover

150b another first resin cover

160 second resin cover

170 adhesive

300 method of packaging the light emitting device of the present invention

310 attaching the light emitting die 120 to the die pad 111

320 step of curing the adhesive 170

330 step of wire bonding

340 covering the first necked down region with a first resin cover

350 step of forming the second resin cover 160