JP2004524681A - Radiation emitter device and manufacturing method thereof - Google Patents

Abstract

The radiation emitting device of the present invention encloses at least one radiation emitter 35, first and second electrical leads 16-14 electrically coupled to the radiation emitter 35, and a portion of the radiation emitter 35 and the electrical lead. And an integral enclosing portion 12 in a form that can be used. The envelope 12 has a first region 30 and a second region 32, the second region exhibiting at least one different characteristic from the first region. The different features are selected from the group consisting of mechanical strength, thermal conductivity, thermal expansion coefficient, specific heat, oxygen permeability, moisture permeability, cohesive strength, and permeability. This radiation emitter is preferably an LED.

Description

【Technical field】
[0001]
The present invention relates generally to radiation emitter devices such as, for example, light emitting diode (LED) packages, methods of making the radiation emitter devices, and optoelectronic emitter assemblies incorporating the optical radiation emitter devices.
BACKGROUND OF THE INVENTION
[0002]
As used herein, the term "discrete optoelectronic emitter assembly" refers to a packaged radiation emitter device that emits ultraviolet (UV), visible, or infrared (IR) when powered. Shall mean. Such a discrete optoelectronic emitter assembly comprises one or more radiation emitters. Radiation emitters, particularly optical radiation emitters, are used in a wide variety of commercial and industrial products and systems, and are therefore sold in many forms and packages. As used herein, the term "optical radiation" is intended to include any emitter device that emits visible, near infrared, or ultraviolet radiation. Such an optical radiation emitter can be photoluminescent, electroluminescent, or another type of solid state emitter. Photoluminescent sources include phosphorescent and fluorescent sources. Fluorescent sources include phosphors and fluorescent dyes, pigments, crystals, substrates, coatings and other materials.
[0003]
Electroluminescent sources include semiconductor optical radiation emitters and other devices that emit optical radiation in response to electrical excitation. Semiconductor optical radiation emitters include light emitting diode (LED) chips, light emitting polymers (LEPs), organic light emitting diodes (OLEDs), and polymer light emitting devices (PLEDs).
[0004]
Components of semiconductor optical emitters, especially LED devices, have become commonplace in a wide variety of consumer and industrial eptoelectronic applications. Other types of semiconductor optical emitter components, including OLEDs, LEPs, etc., can also be packaged in discrete components suitable for many of these applications as alternatives to conventional inorganic LEDs.
[0005]
All color visible LED components are used alone or as small groups as status indicators in products such as computer monitors, coffee makers, stereo receivers, CD players, VCRs, and the like. Such indicators are also found on a wide variety of systems, such as instrument panels on aircraft, trains, ships, cars, trucks, minivans, and sports vehicles. Readable arrays holding hundreds or thousands of visible LED components can be used on mobile message displays, such as those found in many airport and stock market trade centers, and in many sports complexes and some. It can be seen on a high-brightness, large-area outdoor television screen on a billboard in a city.
[0006]
In visual signage systems, such as stop lights (CHMSLs), brake lights, external directional and danger flashing lights, external signage mirrors, and road sign danger lights mounted in the upper center position of the car Amber, red, and red-orange visible light emitting LEDs have been used in up to 100 component arrays. Amber, red, and blue-green visible light-emitting LEDs are being increasingly used in much larger arrays of up to 400 components as stop / deceleration / progress lights at city and suburban intersections.
[0007]
A multicolor combination of a plurality of visible light LEDs is being used as a floodlight white light source for illumination in a binary complementary illuminator and a ternary RGB illuminator. Such illuminators are useful, for example, as vehicle or aircraft map lights, such as vehicle or aircraft reading lights or curtain sheet lights, cargo lights, license plate illuminators, backup lights, and external mirror paddle lights. Other related applications include portable flashlights, other illuminator applications where a robust, compact, lightweight, high efficiency, long life, low voltage white light source is required. In some of these cases, a phosphor-enhanced "white light" LED may also be used as the illuminator.
[0008]
IR emitting LEDs are being used for remote control and communication in devices such as VCRs, TVs, CDs and other audiovisual remote controls. Similarly, IRAD devices such as desktops, laptops, palm-top computers, PADs (Personal Digital Assistants) and printers, network adapters, pointing devices ("mouse", "trackball", etc.), keyboards and other computers. High intensity IR emitting LEDs are being used for communication between various computer peripherals. Also, IR LED emitters and IR receivers can be used as proximity or presence sensors in industrial control systems, as position or orientation sensors in op-electronic devices such as pointing devices and optical encoders, and as bar code scanners. Also functions as a read head in the system. IR LED emitters can also be used as night vision systems for automobiles.
[0009]
Blue, violet, and ultraviolet light emitting LEDs and LED lasers are becoming widely used for data storage and retrieval applications, such as reading and writing to high density optical storage disks.
[0010]
In the case of discrete LED devices and other discrete ("packaged") optoelectronic emitters, improved performance is essentially a matter of increasing the power capacity of a reliable package, reducing the thermal resistance of the package. , Automatic insertion, soldering, and other dependencies on the package's fragility during the circuit or system manufacturing process.
[0011]
In operation, keeping the discrete op-electronic emitters cool will improve performance in several respects. Emitter efficiency typically decreases with increasing operating temperature and increases with decreasing operating temperature. Conversely, the efficiency of the emitter usually increases with decreasing internal operating temperature. The reliability of the emitter and the life of the materials and sub-components that make up the emitter usually increase with decreasing operating temperature. The uniformity of the emission spectrum of the emitter usually increases with decreasing or more uniform operating temperature. Emitter decay lifetime usually increases with decreasing operating temperature. For these and other reasons, it is apparent that it would be beneficial to employ a novel mechanism for reducing the operating temperature of a discrete eptoelectronic emitter.
[0012]
The temperature of the surrounding environment is an external factor that is not always controllable, but the fact that the temperature of the device rises above the ambient temperature is mainly determined by the thermal resistance and operating power of the device.
Unfortunately, most discrete optoelectronic emitters exhibit features that conflict with the goal of reducing the internal operating temperature. In summary, these types of devices typically emit more useful radiation in proportion to the increase in power up to some practical limit of the package or mechanical material or subcomponent. Thus, in applications where more radiation is useful (i.e., nearly all known applications), the device must be at the highest power compatible with the reliability of the device and system and with the power radiation characteristics of the device. It is beneficial to drive However, increased power in devices with limited (positive, non-zero) thermal resistance results in an increase in internal operating temperature.
[0013]
Thus, it would be beneficial to reduce the internal operating temperature without reducing the power of the device, or, alternatively, to maintain the internal operating temperature while increasing the power of the device. . This can be achieved by reducing the thermal resistance of the device.
[0014]
Partly due to the relatively low prevalence of standardized LED forms, and because these forms are almost universally used automated processing equipment in the electronics assembly industry worldwide. Billions of LED components have been used in applications such as those described above due to their ease of processing. Automated processing through mainstream equipment and methods contributes to achieving low capital costs, low reject rates, low labor costs, high production volumes, high precision, high repeatability, and flexible manufacturing methods. Without these properties, the use of LEDs would not be cost-effective or otherwise unattractive from a quality point of view for most mass production applications.
[0015]
Two of the most important processes used in modern electronics assembly processes are high speed automated insertion and high volume automated soldering. Compatibility with automatic insertion or placement machines and one or more common bulk soldering processes are critical to whether discrete semiconductor optical emitters (including LEDs) are commercially available on a large scale. It is important.
[0016]
Thus, the majority of the LEDs used take the form of discretely packaged THD (Through Hole Device) or SMD (Surface Mount Device) components. These configurations mainly include similar devices in the form of a radial lead THD or rectangular shape known as "5 mm", "T-1", "T-1 3/4", which are all transport, To be easily adaptable on tape and reel, tape and ammo or other standardized packages for convenience in handling and for inserting at high speed into printed circuit boards with radial inserts. Have been. Other common stand-alone THD LED packages are easily adaptable to tape and reel for convenience in transport, handling and automatic insertion into printed circuit boards at high speeds in axial inserts. Includes axial components such as "poly LEDs". Common SMD LED components, such as "TOPLED (R)" and Pixar, are also convenient for transportation, handling and high speed automatic placement on printed circuit boards by chip shooters. As such, they are easily spread within blister pack reels and are thus commonplace.
[0017]
Soldering, whether THD or SMD, is a central process in the manufacture of most conventional circuit assemblies using standardized discrete electronic equipment. By soldering the leads or contacts of discrete electronic components, such as LEDs, to the printed circuit board, the components are electrically connected to the conductive traces on the PCB and also provide power to the discrete electronic devices. It remains in electrical communication with other proximal or remote electronics used to supply, control, or otherwise interact with the device electronically. Soldering is generally performed by sonic soldering, IR reflow soldering, convective IR reflow soldering, vapor phase reflow soldering, or manual soldering. Each of these strategies differs from each other, but they all provide an economical electrical connection of discrete electronic devices to a printed circuit board with nearly the same final effect, namely, metal or dissimilar metal bonding. Bring effect. The sonic and reflow soldering process is capable of soldering a very large number of discrete devices together and achieving very high yields and low costs with excellent solder joint quality and uniformity. Are known.
[0018]
There is currently no widely available economical alternative to sonic and reflow soldering processes for mass production. Manual soldering suffers from non-uniformity and high cost. Mechanical connection methods are uneconomical and cumbersome, and are generally unsuitable for multiple electrical connections in multiple circuits. Conductive adhesives, such as epoxies containing silver, can be used to establish electrical connections in some circuit assemblies, but these materials are more costly and expensive to apply than solder. It is. Laser spot welding and other optional soldering techniques are very specialized for particular configurations and applications and can undermine the preferred flexible manufacturing methods in automated electronics circuit assembly processes. For this reason, compatibility with sonic or reflow soldering processes is a desirable property of semiconductor optical emitter components. The effect of this property is much greater because these soldering steps can introduce thermal stresses into the electronic component that are sufficiently large to degrade or destroy the component. Thus, an effective semiconductor optical emitter component is one that can protect the device from encapsulation and transient heat exposure during soldering of the encapsulated wire joints, die attach and chips. Must be manufactured in a manner.
[0019]
Conventional soldering processes require that the ends of the leads of the device (any standoff, ie, the part below the point where the leads contact the pads on the designated PCB) be heated to the melting point of the solder for an extended period of time. And This profile can include cycling the temperature at 230-300 ° C. on the device leads for 15 seconds. Given that the leads of the device are typically made of a plated metal or alloy, such as copper or steel, this high temperature transition is not a problem for the leads themselves. Instead, the problem is the ability of these leads to conduct heat along their length to the encapsulated body of the device. Because these heated leads are in contact with the interior of the body of the device, they will temporarily increase the local internal temperature of the device during the soldering process. This can harm the slightly weaker encapsulation, the encased wire joint, the die attach, and the chip. This phenomenon represents one of the fundamental limitations of today's low cost, optoelectronic semiconductor devices.
[0020]
It is very important to prevent the body of the electronic component from rising excessively above the glass transition temperature of its encapsulant during the soldering process, which is the coefficient of thermal expansion of the polymer encapsulant. Is typically dramatically increased above its glass transition temperature by a factor of two or more. Above its glass transition temperature, polymers soften, expand and plastically deform. Deformation due to this transition of the polymer phase and thermal expansion within the envelope cause mechanical stress and cumulative fatigue large enough to damage discrete semiconductor devices, thereby degrading device performance and Potential pre-deposition can result in premature failure of the field. Such damage is typically caused by: 1) fatigue or breakage of the wire joints (at the bond pads or leadframe of the chip); 2) partial delamination or separation of the die attach adhesive; Fractures; 4) especially due to degradation of the device encapsulant near the entrance where the lead enters the encapsulation and impaired ability to seal environmental water vapor, oxygen or other damaging media.
[0021]
With respect to such thermal fragility, an important difference must be recognized between encapsulating materials suitable for non-optical electronic devices and those suitable for optical devices. Encapsulations used for non-optical devices may be opaque, while encapsulations used in the manufacture of optoelectronic emitters and receivers must be substantially transparent within the operating wavelength band of the device. The side effect of this difference is slight and cannot be grasped.
[0022]
Because transparency is not required in non-optical devices, encapsulating materials for non-optical semiconductor devices include a wide range of compositions including a wide variety of opaque polymer binders, crosslinkers, fillers, stabilizers, etc. be able to. Compositions of this type, such as thickly filled epoxies, have high glass transition temperatures (R _g ), Low coefficient of thermal expansion (C _te ) And / or high thermal conductivity, making these compositions suitable for transient exposure up to 175 ° C. The opaque ceramic composition is thermally stable up to several hundred degrees Celsius, the phase transition temperature is not appreciably noticeable, and the very low C _te And high thermal conductivity. For this reason, exposing conventional opaque encapsulating materials for non-optical devices to electrical leads heated to 130 ° C. or higher, such as for 10 seconds, (by sonic soldering at 230-300 ° C.) is usually , Does not matter.
[0023]
However, the need for optical clarity in the envelopes for optoelectronic emitters and receivers requires the use of the highest performance polymer-filler mixtures, ceramics and compositions suitable for non-optical semiconductors. Is unnecessary. In the absence of inorganic fillers, cross-linking agents or other opaque additives, most optoelectronic devices can be encapsulated.
Transparent polymer materials used for relatively low T _g Value, large C _te A wide variety of epoxies with low thermal conductivity. Therefore, these materials are not suitable for exposing to extreme transition temperatures of about 130 ° C. or higher, as occurs during normal soldering.
[0024]
Numerous improvements and compromises have been made to prior art optoelectronic devices to compensate for the significant potential damage effects of the soldering process. The most notable improvement is the comparison of developing transparent epoxies for encapsulations that can withstand temperatures 10-20 ° C. higher than previously available (currently 110 ° C. to 130 ° C. today). This is a recent technology. Although useful, this method only alleviates some of the above-mentioned problems-the state-of-the-art materials used are still about the same as conventional non-optical semiconductor encapsulation materials, with a drop of 50 ° C. or more.
[0025]
The most common compromise used to successfully avoid the problem of elevated transition temperatures associated with soldering is simply to increase the thermal resistance of the electrical leads used in manufacturing the device. By increasing the thermal resistance of these solderable leads, thermal transitions that occur within the device body during soldering are minimized. Such an increase in thermal resistance can typically be achieved without appreciably affecting the electrical performance of the leads as follows. 1) using a lead material with low thermal conductivity (such as steel); 2) increasing the standoff length of the lead (the distance between the solder contact and the device body); or 3). This is to reduce the cross-sectional area of the lead.
[0026]
Using these three techniques, prior art devices have been achieved by increasing the thermal resistance of the electrical leads and providing the desired protection from the soldering process.
While these approaches are effective in protecting prior art devices from soldering-related thermal transitions, they have limitations, especially in high power semiconductor optoelectronic emitter applications. As a result of the increased thermal resistance of the leads, the operating temperature inside prior art devices increases, significantly impairing the operating performance and reliability of these devices. The soldered electrical leads of most prior art LED devices conduct power to the device and also act as a primary heat dissipation path for heat generated within the device during operation. For this reason, the electrical leads of the prior art devices must be configured to have as low a thermal resistance as possible to facilitate heat dissipation during normal operation. Radiation and natural convection from prior art devices play only a small role in conducting internal heat to the surrounding atmosphere, and the heat conduction through the encapsulating medium is the heat of the optical materials used. Significant impairment due to low conductivity. For this reason, electrically and thermally conductive metal leads must dissipate most of the heat to the surrounding environment by a conduction mechanism. The higher thermal resistance at the solderable pins of these devices required to protect the devices from the transitional thermal effects of the soldering process causes a greater temperature rise within the encapsulated device body during operation.
[0027]
The maximum temperature rise in the portion of the device body that is in contact with the semiconductor emitter under steady state is approximately equal to the product of the power dissipation of the emitter and the thermal resistance between the emitter and the surrounding environment.
As mentioned above, a significant consequence would be if the internal temperature of the device rises substantially above the Tg value of the encapsulant. When the temperature is higher than this temperature, C _te Typically rises very quickly, causing large thermo-mechanical stresses and cumulative fatigue at the LED wire joints and die attach. In most mobile applications, such as automobiles, aircraft, etc., the ambient temperature typically reaches 80 ° C. Thus, when the maximum operating temperature of the encapsulant is in the range of 130.degree. C., opto-etronic emitters for these purposes must limit their operation .DELTA.T to a maximum absolute value of about 50.degree. This limits the power that can be dissipated in a given component, while limiting the current that can pass through that component. Limiting the maximum current will also limit the luminous flux generated, since the emitted luminous flux of semiconductor optical emitters is typically proportional to the current through them.
[0028]
Thus, reducing the internal operating temperature without having to reduce the power of the device, or, alternatively, increasing the brittleness of the device against transient thermal processing damage due to soldering Rather, it would be desirable to maintain the internal operating temperature while increasing the power of the device by reducing the thermal resistance of the device.
[0029]
Other prior art devices circumvent these limitations, but only by ignoring the need for standardized, automated electronics assembly processes and by employing configurations that are incompatible with these processes. Has achieved performance. Other prior art devices achieve high performance by employing unusually expensive materials, sub-components or processes in their manufacture.
[0030]
For example, one prior art approach that has been used to overcome these limitations is the use of special materials such as hermetic semiconductor packages, hybrid chip-on-board technology, ceramics, KOVAR and glass. Alternatively, a complex assembly is used instead of or in addition to the polymer encapsulant. When involved in certain high cost aerospace and telecommunications applications (where component cost is not a significant issue), such devices require expensive materials and specialized assembly processes. As a result, high cost and manufacturing capacity are limited, both of which significantly hinder the use of such components in high-volume applications. The apparatus disclosed in U.S. Pat. No. 4,267,559 issued to Johnson et al. And U.S. Pat. No. 4,125,777 issued to O'Brien et al. Here is a good example of this.
[0031]
The Johnson et al. Patent discloses an apparatus having both a TO-18 header component and a thermal coupling means for mounting the LED chip and transferring internally generated heat to an external heat dissipation means. The header is comprised of several components, including a cover member, an insulator sleeve and an electrical post, and to ensure that the post is electrically insulated as the post passes through the head. Manufactured by a special process. The thermal coupling means is a component that is separate from the header and is made of copper, copper alloy, aluminum or other high thermal conductivity material. According to the teachings of Johnson et al., The coba header subassembly and the copper thermal coupling means are joined together with solder or conductive adhesive to provide electrical continuity, and current is passed into the thermal coupling means, and then It must be allowed to flow into the LED chip. Further, the header and thermal coupling means of the Johnson et al patent are made entirely of dissimilar materials due to their original role in the described assembly. The header must be manufactured at Coba so that it can have a similar coefficient of thermal expansion for the insulator sleeve extending through the header. At least one such sleeve is required to electrically isolate the electrical pins from the header itself. However, the coba has a relatively low thermal conductivity, which necessitates the inclusion of a separate thermal coupling means made of a material such as copper having a higher thermal conductivity. Since the header itself is a complex assembly and is made of a different material than the thermal coupling means, the header is manufactured separately from the thermal coupling means and then heat-treated with solder or conductive adhesive. Must be attached to the coupling means.
[0032]
LED devices similarly manufactured according to the teachings of the Johnson et al. Patent are now sold in special forms similar to the TO-66 package. These devices are complex and typically involve dedicated pins and header structures and / or contain dedicated sub-components therein, such as ceramic insulating sheets.
[0033]
Another strategy used to avoid soldering damage to optoelectronic emitters is to completely prevent the components from being soldered together or to use laser spot soldering or other special electrical mounting methods Need to do. This allows for the fabrication of devices with low thermal resistance from the semiconductor emitter to the interior of the electrical pins without the risk of damage to the device due to the soldering process. Snap LED 70 and Snap LED 150 devices manufactured by Hewlett Packard illustrate this approach. In these devices, electrical connection with the circuit is made by mechanically punching the leads, rather than by soldering, into a simple metal circuit. The resulting device can continuously dissipate as much power as 475 mW at room temperature. However, this configuration involves complex integration of such mechanical elements with extremely complex electronic circuits (such circuits are conventionally formed using printed circuit boards, automatic inserters and sonic or reflow soldering processes). Need to be
[0034]
The last strategy is illustrated by an LED package called Superflux Package (also known as "Piranha") available from Hewlett-Packard. This superflux device combines a moderate degree of thermal resistance between the encapsulated chip and the solder standoff at the pin with a high quality optical encapsulant and dedicated chip material and optical design. This achieves a moderate level of power dissipation without utilizing non-solderable features such as snap LEDs. However, this form has several significant problems that hinder its widespread adoption.
[0035]
The package form of the superflux package makes the form incompatible with conventional high speed THD radial or axial insertion machines or SMT chip shooters known to the inventors. Instead, this package must be placed manually or by an expensive slow robotic profile insertion device. The superflux package will be in a form that can only be used as an “end-on” source—a convenient lead bending technique that can easily convert this device to a 90 ° C. “sidelooker” source. not exist. The device is still susceptible to damage due to poorly controlled soldering processes because the solderable pins of the device have a moderate degree of thermal resistance and a relatively low heat capacity. For some electronic circuit manufacturers, controlling the soldering process to the extent required for this configuration would be inconvenient and costly. Finally, the inventors are not aware that there is a convenient mechanism to package the superflux package with a conventional active or passive heat sink.
[0036]
One major factor that prevents further use of these and other LED devices in signage, lighting, and display applications is that they have high power capabilities and high luminous flux, automated insertion and / or ) There is no device currently available that is easily adaptable to mass soldering processes. These limitations prevent practical use of LEDs in many applications that require high luminous flux emission, or they use many LED component arrays to achieve the desired luminous flux emission Is mandatory.
[0037]
Conventional "5 mm" or "T 1-3 / 4" devices typically have a high thermal resistance of 240 ° C./watt or more, and are usually limited by the transparency of the encapsulant, As a result, if the emitters in the device are operated continuously, routinely or cyclically above 130 ° C. (less than anything except the best available transparent material), reliability will be improved. Will be lacking. Generally, at typical ambient temperatures of 85 ° C. or higher in the automotive environment, the temperature rise in these devices must be limited to 45 ° C. to avoid these material limitations. This means that the power of the device must be limited to about 0.18W. To accommodate manufacturing variations, with a reasonable 33% design manufacturing tolerance, the practical reliable power limit for this device should be about 0.12W. This is not a high power, which limits the luminous flux of these devices. To solve this, it is often the case that many of these devices are used in combination to generate the luminous flux or radiation flux required for the application (for example, 50 in the case of a CHSML in a car, the traffic lights of a traffic light). In the case, as many as 400).
[0038]
The Hewlett-Packard superflux or piranha device has a lower thermal resistance than the "5 mm""T1-3 / 4" device, typically 145 ° C / watt. As in the case of “5 mm” or “T1-3 / 4” devices, superflux or piranha devices typically have an emitter in the device of 130 ° C. or higher (less than any other than the best available transparent material). If operated continuously, routinely or cyclically (low), it is limited by the less reliable transparent encapsulant. For typical ambient temperatures, typically greater than 85 ° C. in the automotive environment, the temperature rise in these devices must be limited to 45 ° C. to properly avoid these material limits. This means that the power of the device must be limited to about 0.3W. These devices are then mounted by high thermal stress sound waves or other soldering processes, and their thermal resistance from lead to joint decreases, making them more susceptible to damage during processing into circuits. . Thus, to accommodate manufacturing variability and increased fragility, larger design manufacturing tolerances of 40% must be employed, and the practically reliable power limit of this device is about 0,0. It must be 18W. This is a significant increase (33%) compared to "5 mm" or "T1-3 / 4" devices, but not high power, and the emitted light flux of these devices is similarly limited. Will be. To alleviate this, many of these devices are used in combination to generate the luminous flux or radiation flux required for the application (eg, as many as 30 for a motor vehicle CHSML).
[0039]
Hewlett-Packard's snap LED devices have a lower thermal resistance than "5 mm" or "T1-3 / 4" or superflux or piranha devices, at 100C / W. As in the case of "5 mm" or "T1-3 / 4" or superflux, piranha or snap LED devices typically have an emitter in the device of 130 [deg.] C. or higher (anything except the best available transparent material). (If lower), is limited by a transparent encapsulating material that would be less reliable if operated continuously, routinely or cyclically. For typical ambient temperatures, typically above 85 ° C. in an automotive environment, the temperature rise in these devices must be limited to 45 ° C. so that the limits of these materials can be properly avoided. This means that the power of the device must be limited to about 0.45W. As mentioned above, these devices cannot be soldered without damage by conventional means because of the extremely low thermal resistance of these devices from the lead to the joint. This significantly limits its usefulness, but is still suitable for some applications. Since these devices are subsequently mounted by a mechanically stressful bending process, they are still susceptible to damage during the processing process. Thus, it is necessary to use manufacturing tolerances as large as 40% to accommodate manufacturing variations and to accommodate increased fragility during processing, and the practical and reliable power of this device. The limit value should be about 0.27W. This is a significant increase compared to "5 mm" or "T1-3 / 4" or superflux or piranha devices, but still not great power (this at the expense of conventional solderability. Realized). To overcome the luminous flux limitations imposed by these devices, many are often used in combination to generate the luminous or radiation flux required for a single application (for example, in the case of a car CHSML, 12 (In the case of individual and rear combination stop / turn signal / taillight lamps for cars, 70 lamps).
[0040]
Surface mount devices such as TOPLED (R), PLCC and Hewlett-Packard's "high luminous flux" or "Barracuda" devices use dissimilar polymer materials in their manufacture and the first one used in the assembly sequence is A plastic material that forms the basic structure of the device body and holds the leads of the device together. This strategy involves first processing the leadframe via insert molding (to place the first support material around the leadframe), then attaching the die, wire bonding, and setting up a second molding step. Need to do. The second molding stage must be optical molding (to initially provide die and line bonding opportunities). Such designs and processes are difficult and uneconomical to perform with high yield and quality. Cumulative variations will be excessive with the multi-stage molding process, interrupted by die and wire bonds.
[0041]
A further problem faced by designers of conventional LED devices is that the wire joints used to connect one of the LED leads to the LED chip may break or lose contact with the lead or chip. There is a point. Such failures may occur, for example, due to shear forces transmitted to the wire joint through the envelope or through thermal expansion / contraction of the envelope around the wire joint.
[0042]
Other forms of the radiation emitters described above also experience reduced performance, increased potential for damage, breakage or accelerated degradation if exposed to excessive operating temperatures.
Accordingly, it is desirable to provide a radiation emitter device that has a higher emission power capability than conventional LED devices, while being less susceptible to breakage due to broken wire junctions or other defects due to excessive operating temperatures. Is desirable.
[0043]
Further, while minimizing the need for retrofits to the devices used for the manufacture of LED devices, it can facilitate the immediate use of the LED devices of the present invention instead of conventional LED devices. It would be desirable to provide a radiation emitter device having improved emission power over conventional LED devices, while retaining the same dimensions and shape as conventional LED devices.
[Patent Document 1]
U.S. Pat. No. 4,267,559
[Patent Document 2]
U.S. Pat. No. 4,125,775
DISCLOSURE OF THE INVENTION
[Problems to be solved by the invention]
[0044]
It is therefore one object of the present invention to solve the above-mentioned problems and to provide a radiation emitter device with improved performance and less susceptibility to catastrophic damage.
[Means for Solving the Problems]
[0045]
According to one embodiment of the present invention, a radiation emitting device includes at least one radiation emitter, first and second electrical leads electrically coupled to the radiation emitter, a radiation emitter and first and second radiation leads. An integral encapsulant configured to enclose a portion of the second electrical lead. The encapsulant has at least a first region and a second region. The second region exhibits at least one characteristic different from the first region. The different features can be physical, structural and / or compositional features. For example, the at least one different feature can include at least one or more of the following: mechanical strength, thermal conductivity, heat capacity, specific heat, coefficient of thermal expansion, adhesion, Oxygen impermeability, water impermeability and the transmission of radiation emitted from the radiation emitter.
[0046]
The method of manufacturing a radiation emitting device according to the present invention includes: (1) attaching and electrically connecting at least one radiation emitter to a lead frame to form a subassembly; and (2) attaching the subassembly to a mold cavity. (3) filling at least a portion of the mold cavity with a first encapsulating material, and (4) filling the remainder of the mold cavity with a second encapsulating material. (5) removing the encapsulated sub-assembly from the mold cavity.
[0047]
In a wide range of otherwise discrete opto-electronic emitters, which are otherwise conventional, the present invention significantly increases the power capacity of a reliable package and improves the package thermal resistance and package fragility. In a significant way.
[0048]
The above and other features, advantages and objects of the present invention will be better understood and appreciated by those skilled in the art by reference to the following description, appended claims and accompanying drawings.
[Detailed description of preferred embodiments]
[0049]
The present invention will now be described in more detail with reference to the presently preferred embodiments, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
[0050]
For the purposes of this description, “up”, “down”, “right”, “left”, “rear”, “front”, “vertical”, “horizontal”, “top”, “bottom” The terms and their derivatives refer to the invention when looking directly at the radiation emitting device along the main optical axis of the light source. It should be understood, however, that the invention is capable of various alternative orientations, except where explicitly stated. It is also to be understood that the specific devices illustrated in the accompanying drawings and described below are merely examples of the spirit of the invention as defined in the following claims. Therefore, specific dimensions, ratios, and other physical features related to the embodiments disclosed herein are not to be considered as limiting, unless the claims clearly state otherwise. Absent.
[0051]
Some embodiments of the present invention generally relate to improved optical radiation emitting devices that can be used in both high power and low power applications. Such an embodiment of the present invention is particularly suited for use in limited power applications such as vehicles, portable lamps, special lighting. Vehicles include, but are not limited to, cars, trucks, vans, buses, recreational vehicles (RVs), bicycles, motorcycles and mopeds, motor-driven carts, electric vehicles, electric carts, electric bicycles, ships, boats, hovercraft, It shall mean land vehicles, surface vehicles, aircraft and manned space vehicles, including submarines, airplanes, helicopters, space stations, shuttle vehicles and the like. By portable lamps is meant head or helmet mounted lamps, such as camping lanterns, mining, mountaineering and caving, handheld flashlights and the like. By special lighting is meant emergency lights that are activated when a power outage, fire or smoke in the building fills, stage illuminators on microscopes, front lighting on billboards, rear lighting on signs, and the like. The light emitting assembly of the present invention can be used as either an illuminator or an indicator. Some examples of applications in which the present invention can be used are disclosed in U.S. Patent No. 6,441,943 to Roberts and assigned to the assignee.
[0052]
Some embodiments of the present invention are capable of generating white light of sufficient illumination intensity with sufficient appearance color and brightness to be sufficient to observe the object of interest and to be easily identifiable. To provide a reliable, low voltage, long life light source for vehicles, portable lighting and special lighting. Some of the radiation emitter devices of the present invention can be well suited for use with AC or DC power supplies, pulse width modulated DC light sources, and electronic control systems. The radiation emitting device of the present invention emits light of various colors and / or can be further used to emit non-visible radiation, such as IR or ultraviolet radiation.
[0053]
As used herein, the terms "radiation emitter" and "radiation emitting device" include any structure that generates and emits optical or non-optical radiation, while "optical radiation emitter" or "radiation emitter". The term "optical radiation emitting device" is intended to include radiation emitters that emit optical radiation, including visible light, near infrared (IR) radiation, and / or ultraviolet (UV) radiation. As mentioned above, the optical radiation emitter can include an electroluminescent source or other solid phase source and / or a photoluminescent or other light source. One form of an electroluminescent light source includes a semiconductor optical radiation emitter. For purposes of the present invention, a "semiconductor optical radiation emitter" is any semiconductor that emits electromagnetic radiation having a wavelength in the range of 100 nm to 2000 nm by a physical mechanism of electroluminescence when a current passes through a component or material. Components or materials. The main function of the semiconductor optical radiation emitter in the present invention is to convert the transmitted power to the emitted optical power. Semiconductor optical radiation emitters include typical IR, visible or UV LED chips or dies known in the art and used in a wide variety of prior art devices or any of the alternatives described below. May include a conventional form of semiconductor optical radiation emitter.
[0054]
Alternative forms of semiconductor optical radiation emitters that can be used in the present invention include light emitting polymers (LEPs), polymer light emitting diodes (PLEDs), organic light emitting diodes (OLEDs), and the like. Such materials and optoelectronic structures made therefrom are electrically similar to conventional inorganic LEDs, but utilize organic compositions such as derivatives of the conductive polymer polyaniline for electroluminescence. Such semiconductor optical radiation emitters, although relatively new, are available from sources such as Cambridge Display Technology, Ltd. of Cambridge, California and Uniax of Santa Barbara. it can.
[0055]
For simplicity, the term semiconductor optical radiation emitter can be replaced by the term LED or alternative form of emitter described above or known in the art. Examples of emitters suitable for the present invention have associated conductive paths and pads for electrical attachment and are mainly doped with AlGaAs, AlInGaP, GaAs, GaP, InGaN, AlInGaN, GaN, SiC, ZnSe, etc. Including a wide variety of LEDs that emit at the PN or NP junctions within the inorganic compound.
[0056]
Because LEDs do not appreciably degrade in reliability or in-service life when switched on and off mechanically or electronically over millions of cycles, the LEDs are of the present invention. It is a preferred electroluminescent light source for use in radiation emitting devices. The luminous intensity and illuminance from the LEDs accurately approximates a linear response function to the applied current over a wide range of conditions, making control of its intensity relatively simple. Finally, recent generations of AlInGaP, AlGaAs, InGaN, AlInGaN, and GaN LEDs draw less power per lumen or candela of generated visible light than incandescent light, resulting in a more economical, compact, and Lightweight lighting device wiring harness, fuse, connector, battery, generator, alternator, switch, electronic control unit, and optical element. While numerous examples have been previously described and are within the scope of the present invention, the present invention does not deviate appreciably from the teachings set forth herein, and thus falls within the scope of the present invention. It should be understood that it has other distinct uses other than the specific ones described.
[0057]
Another preferred radiation source that can be used in the light emitting assembly of the present invention is a photoluminescent source. Photoluminescent sources generate visible light by absorbing some of the visible or non-visible radiation and re-emitting the visible radiation. Photoluminescent sources are phosphorescent and fluorescent materials, including fluorescent dyes, pigments, crystals, substrates, coatings and phosphors. Such phosphorescent or fluorescent materials may be excited by an LED or other radiation emitter and placed in or on the LED device, or in a separate optical element such as a lens or diffuser that is not integral with the LED device. Or it can be arranged thereon. Exemplary structures using phosphorescent or fluorescent sources are described in further detail below.
[0058]
1 to 3 show a radiation emitter device 10 having a structure according to a first embodiment of the present invention. As shown, the radiation emitter device 10 includes an encapsulant 12, first and second electrical leads 14, 16, and a radiation emitter 35. The encapsulant 12 encloses a portion of each of the emitter 35 and the electrical leads 14,16. The electrical leads 14, 16 may have optional respective standoffs 18, 20 provided when configured for THD applications, to assist in automatically inserting the device.
[0059]
As best shown in FIG. 3, the upper end of the first electrical lead 14 extends horizontally upward and defines a reflective cup 36, and the radiation emitter 35 is preferably mounted on the reflective cup. Electrically connecting the first contact terminal of the radiation emitter 35 to the first electrical lead 14 can be through a die attach (not shown) or through a wire bond or other connector. it can. Apparatus 10 further includes a wire joint 38 or other means for electrically coupling the second contact terminal of radiation emitter 35 to second electrical lead 16. The upper ends of the first lead 14 and the second lead 16 are electrically connected to each other due to the spaced relationship and because the encapsulant 12 is preferably made of a material having a relatively high electrical resistance. Insulated.
[0060]
The radiation emitter device 10 illustrated in FIGS. 1-3 is intended to have the same relative dimensions and shape as a conventional 5 mm / T-1 3/4 LED device or 3 mm T-1 device, and thus, The seal 12 has a lower edge 22 and a flat side 24, which facilitates alignment of the radiation emitter device with an automatic insertion device.
[0061]
As best shown in FIG. 3, an optional globe top 40 or other optical or physical modulator is located on at least a portion of the radiation emitter 35 and the line junction 38. The glove top 40 is made of silicone or silastic, and may include an optional phosphor or other photoluminescent material. The use of the glove top 40 is beneficial in helping to protect the radiation emitter 35 and its connection with the line joint 38 during the molding process. Other advantages of providing glove top 40 are described further below.
[0062]
The encapsulant 12 of the radiation emitter device 10 according to the invention has at least two active areas 30, 32 between which there is a transition area 31. The two separate working areas 30, 32 are such that different portions of the encapsulant perform significantly different actions than the other parts of the encapsulant, and the first area 30 has a second area 32 and at least one Provided based on the inventors' recognition that they have different features and can optimize the performance of the action performed by the particular area. For example, the first region 30 is at least partially transparent to the wavelength of the radiation emitted from the radiation emitter 35, while the second region 32 need not be transparent to such a wavelength. This allows the radiation emitter device of the present invention to take advantage of the particular advantages of high performance power semiconductor encapsulants and transfer molding compounds in the second region. These features include a relatively small coefficient of thermal expansion, a relatively large thermal conductivity, a relatively large T _g , Relatively high specific heat, relatively low permeability to oxygen gas or water vapor, and relatively high physical strength properties. Compounds used for packaging or potting a large number of high power non-optical electronic devices are those conventionally used for conventional optoelectronic emitters due to the large margins in these many categories. Better than. One of the main reasons for the difference is that the described high-performance materials are usually opaque mixtures, ie, they are not transparent to the radiation bands emitted in discrete optoelectronic emitter devices. is there. The opacity of these operatively attractive materials is inherently related to their advantageous properties (eg, due to mineral, metal and metal oxide fillers that enhance performance), and therefore, these materials Has not heretofore been considered for use in optoelectronic components due to its opacity. However, by limiting the use of such materials to those areas of the encapsulant 12 that do not require transparency, the present invention enjoys all the advantages of these material features.
[0063]
The first region 30 of the encapsulant 12 is preferably a substantially transparent material so as to maintain optical performance. The first region 30 can be selectively partially diffused. First region 30 may be made of any conventional transparent encapsulant commonly used for optoelectronic emitter devices. The first region 30 of the lens 12 covers, encloses, protects and supports a portion of the radiation emitter 35, the die attach (if present) and any wire joints 38 connected to the radiation emitter 35. Is preferred.
[0064]
The first region 30 of the encapsulant 12 may consist of two or more parts, the innermost part being pre-applied to the radiation emitter 35 before the first stage of molding the encapsulant of the invention. Silicone or silastic glove top 40. The innermost portion of the first region 30 may alternatively be a high performance epoxy, silicone, urethane or other polymeric material including an optically translucent or transparent filler or diffusing material.
[0065]
The first region 30 of the encapsulant 12 preferably comprises a composition comprising an optical epoxy mixture that is substantially transparent to the radiation emitted by the radiation emitter 35. However, other transparent materials can be used and the material need not be transparent in zones outside the primary emission band of the radiation emitter.
[0066]
The second region 32 of the encapsulant 12 is preferably made of a material that optimizes the action of the region of the encapsulant 12. As mentioned above, the second area 12 does not need to be transparent. However, the specific function of region 32 is to minimize catastrophic failure, stress and cumulative fatigue due to mechanical stress that propagates up to conductive leads 14 and 16 as a whole. Not only can the material be better suited for this purpose because it need not be transparent, but the material also has higher tensile and compressive strengths, including higher tack and / or cohesiveness. It can also have strength properties.
[0067]
Another effect that the second region 32 of the encapsulant 12 plays is that it would otherwise propagate upwardly into the device through the second region 32 or the interface between the leads 14, 16 and the encapsulant 12. It acts as a barrier to any oxygen, molecular water vapor or other reagents that may be present. Thus, the second region 32 includes the radioactive emitter 35, the die attach (if present), the wire bond 38, the encapsulant portion of the leadframe plating, and any photoluminescent material that may be present. The internal composition of the other devices, including the materials, must be effectively protected from oxygen, molecular water vapor and other reagents. Because the second region 32 of the encapsulant 12 need not be transparent, the second region 32 has a structure that has improved barrier properties compared to those present in conventional transparent encapsulants. be able to.
[0068]
One of the features in which the second region 32 differs significantly from the first region 30 is probably that it has improved thermal characteristics. In order to achieve a lower thermal resistance of the device, the second region 32 is present at least in the critical region of the device surrounding the electrical leads 14, 16 and also on the part of the lead that supports the radiation emitter 35 (ie, is present). Then, it is preferable to have a large thermal conductivity at the thermal junction with the reflective cup 36). To maintain a relatively high thermal resistance protection from the soldering process, the bottom portion of the second region 32 of the encapsulant 12 may have a lower height than the standoffs 18, 20 (if present) or a standoff. In the absence of a solderable portion or end of conductive leads 14, 16 than an equivalent point on the lead designed to remain in almost no contact with the molten solder during processing. It does not stretch to near.
[0069]
By forming the second region 32 of the encapsulant 12 to have a large heat capacity, the second region 32 will serve to suppress transient temperature spikes during processing or operation. Also, by configuring the second region 32 to have a low coefficient of thermal expansion, catastrophic failure, stress and cumulative fatigue due to thermal expansion and contraction within the device are minimized.
[0070]
To achieve different operational characteristics for the first and second regions 30, 32 of the encapsulant 12, the two regions may have different physical properties. Such physical properties can be structural or compositional. Such different structural features use the same overall composition for the first and second regions 30, 32, but by changing the particle size or microstructural orientation in the two regions. Can be realized. Such structural features can be modified during the molding process by treating the areas differently by annealing, radiation hardening or other radiation treatment. Further, the microstructural orientation can be changed by applying a magnetic field to one or more of the regions forming the encapsulant 12.
[0071]
Where two different compositions are utilized to form the first and second regions 30, 32, the method of the present invention will be described in further detail below to form one preferred embodiment of the present invention. As such, it is preferred that the composition of the material be adapted for molding in the same mold. By integrally molding the first and second regions 30 and 32, a cohesive joint can be formed at the transition portion 31 between the regions 30 and 32. Such cohesive joints generally increase the strength of the encapsulant and allow oxygen, water vapor or other reagents to pass through the radiation interface 35 through all interfaces between the regions 30, 32 that would otherwise be present. Is desired to prevent reaching. Further, such cohesive joints provide continuity with the outer surface. As further described below, it is desirable that the composition used for the first and second regions 30, 32 be partially intermixed at the transition 31. The transition 31 may be a fairly narrow cross-section of the encapsulant 12, or wider and larger if a composition gradient is formed using the composition of the first and second regions 30, 32. Can be.
[0072]
A further advantage of making the second region 32 of the encapsulant 12 opaque is that any backscattered light from the device 10 is substantially reduced. Such backscattered light is problematic when the optical sensor is mounted in the same housing as the radiation emitting device 10, as often occurs when such a radiation emitter device is mounted in an electrochromic rearview mirror assembly for a vehicle. .
[0073]
Having described the general physical structure of the radiation emitting device of the present invention, the method of the present invention for manufacturing such a radiation emitter device will now be described. However, it will be appreciated that the radiation emitter device 10 can be formed using other methods.
[0074]
FIG. 10 shows a flow diagram illustrating the steps and optional steps for the method of the present invention. FIG. 10 will be described with simultaneous reference to FIGS. 4 to 9 which show various stages of the device assembly. The first step 100 of the method of the present invention is to prepare a lead frame. One example of a lead frame is shown in FIG. The lead frame can be formed in any conventional form using any conventional technique. The lead frame 52 is made of metal and can be stamped and selectively post-plated. The lead frame 52 can also be selectively ultrasonically or otherwise cleaned. As shown in FIG. 4, the lead frame 52 has first and second conductive leads 14, 16 for a plurality of radiation emitter devices. The leads 14 and 16 are held together by a first tie bar 54 and a second tie bar 56 that extend substantially perpendicular to the leads 14 and 16. The lead frame 52 may further include a vertical frame member 58 extending between the first and second tie bars 54, 56 at both ends of the lead frame 52 and extending between the plurality of pairs of leads 14, 16.
[0075]
The lead frame 52 is also preferably shaped to have a support (preferably the reflective cup 36) at one end of the first electrical lead 14. The reflective cup 36 can be polished or plated to improve its reflectivity.
[0076]
The next step in the process (step 102) is to attach one or more radiation emitters 35 to each of the reflective cups 36 on the lead frame 52. In the most preferred embodiment, the radiation emitter 35 is an LED chip, which is in or on each of the cups 36 or to other support structures of the lead frame by conductive epoxy attachments or eutectic joints. , Die bonded. The LED chip, if used, can be any conventional LED chip or any LED chip or other radiation emitter developed later. As part of this process, the mounting epoxy can be selectively degassed by vacuum pressure and then cured / cooled. The structure can then optionally be subjected to ultrasonic and other cleaning steps after the above steps.
[0077]
In the most preferred embodiment, the radiation emitter 35 is then wire bonded with a bond wire to establish a desired conductive path to the radiation emitter 35 (step 104). Next, in step 106, a selective phosphor, glove top or other optical or physical conditioning agent is deposited on the radiation emitter 35. It should be appreciated that one or more of such optical or physical conditioning agents can be used (eg, applying a phosphor first, curing / drying, and then applying a silicone glove top). Can be). Regardless of which is applied at this stage, it is usually then dried and cured (step 108). Optionally, such selective optical or physical conditioning agents can be degassed by vacuum before proceeding to the next step.
[0078]
The next step (step 110) is to selectively apply a transparent epoxy into the reflective cup 36, followed by an optional degassing step, which may be performed by vacuum pressure. This selective application of the transparent epoxy can be performed during subsequent molding steps to prevent bubbles from forming in and around the reflective cup. The applied clear epoxy may be the same material as applied during the first molding step described below. After step 110, fabrication of the leadframe subassembly 50 (FIG. 4) is complete and such subassembly is ready for molding.
[0079]
Thus, the next step (step 112) is to invert leadframe subassembly 50 and insert and align leadframe subassembly into enclosing mold cavity 62 formed in mold 60. It is. As shown in FIG. 5, the mold preferably has a plurality of leadframe supports 64 for receiving and aligning the leadframe subassembly 50 with the proper position relative to the mold cavity 62. FIG. 6 shows a cross-sectional view of one such mold cavity 62, with a corresponding portion of the leadframe sub-assembly 50 inverted and inserted into the cavity 62.
[0080]
The next step (114) performs the first stage of encapsulation, whereby the transparent epoxy lens material is dispensed into the encapsulant mold cavity 62 (preferably by an injection method). Using a precision metering supply or feedback bag, fill the transparent epoxy up to or above the edge of the inverted reflective cup 36, or if for any reason the reflective cup is not present in the device. It is preferable to fill up to the surface of the radiation emitter 35. For example, see FIG. Next, an optional degassing step (step 116) is performed to remove bubbles from the clear epoxy by vacuum pressure. Next, a step (118) of pre-curing the transparent epoxy can be optionally performed. This selective pre-cure may be sufficient to cure to minimize free mixing of the two primary encapsulating materials, but not so significant as to prevent any mixing. Some slight mixing in the transition region 31 is considered good for homogeneous strength, condensable bonding, etc.
[0081]
The next step (step 120) is the first of an encapsulation method (preferably by injection) in which the base epoxy is dispensed into the mold cavity 62 so as to fill the rest of the mold cavity 62. Is to perform the following steps. Precise metering or feedback is preferably used to accurately fill the predetermined bottom of the device body or the top of standoffs 18, 20 (if present). FIG. 8 illustrates the appropriately filled mold cavity 62 after the second stage.
[0082]
After step 120, step 122 is optionally performed, whereby the base encapsulant is degassed by vacuum pressure to remove any air bubbles.
Next, in step 124, the base encapsulant is cured, along with curing any previously unresolved residues of other materials that have not yet been fully cured. Next, in step 126, the substantially finished lead frame structure is ejected from the mold 60. Next, an optional post-curing step 128 can be performed, followed by an optional cleaning / deburring step 130. The resulting structure is illustrated in FIG.
[0083]
The next step is a singulation step 132 whereby the second tie bar 56 and vertical leadframe member 58 are cut from the finished leadframe assembly and the first tiebar 54 is removed for each of the devices. Cut between the first and second electrical leads 14, 16 and between each of the devices. If a standoff is not desired, the entire first tie bar 54 can be removed, otherwise the remaining tie bar 54 portion can act as the standoffs 18,20.
[0084]
After the unification step 132, an optional test step 134 can be performed, and then the device is packaged and shipped. Variations on this method are described below with respect to alternative embodiments of the present invention.
[0085]
FIG. 11 shows a radiation emitter device 150 having a structure according to the second embodiment of the present invention. Apparatus 150 differs from apparatus 10 described above in having a plurality of radiation emitters 35a, 35b. Both emitters 35a, 35b can be mounted in a common reflective cup or in separate cups on the same or separate leads. Depending on the desired electrical connection and control, additional leads 16b can be provided. The radiation emitters 35a, 35b may be connected in series or in parallel and may have the same structure or different structures to emit light of different wavelengths. In one preferred embodiment, the emitters 35a, 35b emit light of a complementary nature (complementary color) of bipolar so as to be able to generate useful white light. LED chips and devices suitable for such applications are described in D-Bert, R., et al. U.S. Patent Application No. 5,803, filed by Robert R. Turnbull et al. 579.
[0086]
The base epoxy used to form the second encapsulation region 12 differs from the transparent lens epoxy used to form the first region 30 not only in terms of composition, but additionally or Alternatively, one or more physical properties (spectral transparency at the wavelength of interest, diffuse scattering properties at one or more wavelengths of interest, microcrystalline structure, strength, thermal conductivity, CT _E , T _g Etc.). The transition region 31 between the first region 30 and the second region 32 can occur at the transition boundary region 31, which can be narrow (change properties more rapidly) or wide ( The properties can be changed more gradually or have a gradient). Also, as described above, the difference between the lens epoxy and the base epoxy is compositional, and this difference can be realized by using a mixture of two different materials in the manufacturing process. Next, the narrow transition boundary region 31 between the regions 30, 32 secures two substantially immiscible preparations, or one material is slightly or completely before adding the other material. It can be realized by curing. On the other hand, the large boundary area 31 ensures that the first material is not pre-cured before adding the second material, or that the formulation of the two materials allows significant mixing at that boundary. Will be realized.
[0087]
If the desired difference between the lens epoxy and the base epoxy is primarily a physical rather than a compositional difference, use alternative means to achieve this if the above means are inadequate. Can be. For example, it is possible to improve the material properties of the compositionally identical base epoxy portion by disposing the base epoxy portion after dispensing into the mold. Such a post-treatment may be a different heat treatment (by establishing a temperature gradient in the mold or by using a layered furnace or a layered heated air flow). Such pre-treatment may additionally or alternatively be local IR, UV, visible, microwave, X-ray or other sources of electromagnetic radiation or differential irradiation by E-beam or other particle beams. Also, by exposing all or a portion of the device material to an electric field, magnetic field, centrifugal / centripetal force, or gravity before, during, or after dispensing, certain microstructural effects (particle migration, lamination, Orientation, size, agglomeration, etc.).
[0088]
FIG. 12 shows a radiation emitter device having a structure according to the third embodiment of the present invention. The device shown in FIG. 12 is configured to have the same size and shape as a Hewlett-Packard superflex or piranha device. However, as shown, the device 200 includes an envelope having a first region 230 and a second region 232 applied in a manner similar to that applied in the first two embodiments. The difference is that the material 212 is incorporated.
[0089]
13 and 14 show a radiation emitter device 250 structured according to a fourth embodiment of the present invention. As is evident from FIGS. 13 and 14, this fourth embodiment is intended to mimic the Hewlett-Packard snap LED device configuration in both size and configuration. By setting the various embodiments of the present invention to be able to mimic conventional products in terms of size and shape, the device of the present invention has some advantages over the devices used to construct circuit boards. It can be easily replaced with conventional equipment without the need for modification. Further, by setting these embodiments to mimic the conventional structure, the present invention can be implemented using the same encapsulation mold cavities used to manufacture the conventional device. , Which can obviate the need for major modifications to the equipment used to manufacture these radiation emitter devices.
[0090]
FIG. 15 shows a radiation emitter device 300 structured according to a fifth embodiment of the present invention. The device 300 has an additional heat-dissipating member 310 that extends outwardly from the encapsulation separately and separate from the electrical leads. Other suitable arrangements utilizing heat-dissipating members are disclosed in the above-mentioned U.S. Patent No. 6,335,548, assigned to Robert et al. And assigned to the assignee.
[0091]
In the case of the structure shown in FIG. 15, it is desirable to form a micro-groove lens such as a Fresnel lens directly in the enclosing portion. This is particularly beneficial when different color LED chips are provided within a single discrete LED where light from the chips mix to form another color, such as white light. is there. Also, a reflective element may be coupled to the light output surface of the device to further modify the light emitted from the device. An example of a micro-groove lens and an LED device having such a reflective element is disclosed in commonly assigned U.S. Patent Application No. 60 / 270,054.
[0092]
The invention will be further clarified by the following examples, which are intended to illustrate the invention and thus are not intended to limit the invention in any way.
Embodiment 1
[0093]
To demonstrate the effectiveness of the present invention, two LED devices were manufactured and tested. The first LED device is a conventional T-13 / 4 LED device, while the second LED device has an encapsulation 12 as disclosed above with respect to the first embodiment of the present invention. It has the same structure except that it is included in the region 32. A conventional T-13 / 4 LED device was manufactured using Hysol (registered trademark) OS4000 transparent epoxy available from Dexter Electronic Materials Division. The T-13 / 4 LED device of the present invention was fabricated using the same clear epoxy as for the first region 30. However, the second region 32 was similarly manufactured using the Hisol® EO0123 casting compound available from Dexter. The two LED devices were then operated by DC operation at room temperature, their normalized average luminous flux was measured and plotted on the graph shown in FIG. As is clear from this graph, the LED device of the present invention had a much larger amount of luminous flux especially at high power.
[0094]
In contrast to this example, the improved illuminance at each power level of the LED device of the present invention over the conventional LED device indicates that the working temperature of the junction has been reduced and the thermal resistance of the assembly has been reduced.
[0095]
Although the invention has been described generally as employing two or more regions in a substantially vertically disposed encapsulation when the main optical axis of the device is vertical, these regions may have a central optical axis. It is understood that the azimuth can be controlled with respect to the left or right side of the camera, respectively, or oriented so that one is on the outside and the other is on the inside. Such an inside / outside arrangement of the encapsulation area provides an outside-to-inside "cure gradient" whereby the inside does not completely cure and remains flexible for the life of the radiation emitter device. This can be realized by doing so. Such a configuration can also be used by using heat generated by the radiation emitter 35 itself to cure the inside of the LED. This is beneficial when low mechanical residual stress is desired.
[0096]
In some embodiments of the present invention, the thermal resistance from the radiation emitter junction (junction with the lead) to the surrounding environment is reduced without reducing the thermal resistance, thereby reducing the heat generated by soldering the lead. Excellent operating temperatures at a given power (i.e., low operating temperatures) can be achieved without being more susceptible to mechanical damage.
[0097]
The above description is considered that of the preferred embodiments only. Modifications of the invention will occur to those skilled in the art and to make or use the invention. For this reason, the embodiments shown in the drawings and described above are merely for illustrative purposes only, and are not intended to limit the scope of the invention, which It is defined by the claims, which are construed in accordance with the principles of patent law, including the theory of matter.
[Brief description of the drawings]
[0098]
FIG. 1 is a perspective view of a radiation emitter device manufactured according to a first embodiment of the present invention.
FIG. 2 is a top view of the radiation emitter device shown in FIG.
FIG. 3 is a cross-sectional view of the radiation emitter device shown in FIGS. 1 and 2 along a line 3-3 ′ shown in FIG. 2;
FIG. 4 is a side view of a leadframe subassembly capable of manufacturing the radiation emitter device shown in FIGS. 1-3.
FIG. 5 is a perspective view of the leadframe subassembly shown in FIG. 4 inverted and inserted into a mold in accordance with the method of the present invention for manufacturing a radiation emitter device.
FIG. 6 is a section along line 6-6 ′ of FIG. 5, showing a portion of the leadframe subassembly inverted and inserted into the mold shown in FIG. 5 prior to the first molding step; It is sectional drawing.
7 is a partial cross-section taken along line 6-6 'of FIG. 5, showing a portion of the leadframe subassembly inverted and inserted into the mold shown in FIG. 5 after an initial molding step; FIG.
8 is a partial cross-section taken along line 6-6 'of FIG. 5, showing a portion of the leadframe subassembly inverted after the last molding step and inserted into the mold shown in FIG. FIG.
FIG. 9 is a side view of the final lead frame assembly after removal from the mold.
FIG. 10 is a flow chart showing the steps of the method of the invention for manufacturing a radiation emitter device according to the invention.
FIG. 11 is a sectional view of a radiation emitter device manufactured according to the second embodiment of the present invention.
FIG. 12 is a perspective view of a radiation emitter device manufactured according to the third embodiment of the present invention.
FIG. 13 is a perspective view of a radiation emitter device manufactured according to a fourth embodiment of the present invention.
14 is an exploded perspective view of the radiation emitter device shown in FIG.
FIG. 15 is a perspective view of a radiation emitter device manufactured according to a fifth embodiment of the present invention.
FIG. 16 is a graph showing the normalized average luminous flux as a function of applied power for a conventional T-1 3/4 LED device and the inventive T-1 3/4 LED device shown in FIGS. 1-3. is there.

Claims (74)

In the radiation emitting device,
At least one radiation emitter;
First and second electrical leads electrically coupled to the radiation emitter;
An integral envelope configured to encapsulate the radiation emitter and a portion of the first and second electrical leads, the integral envelope having at least one first region and one second region. A radiation emitting device, wherein said second region comprises said integral encapsulation exhibiting at least one characteristic different from said first region. The radiation emitting device of claim 1, wherein said at least one different feature is a physical feature. The radiation emitting device of claim 1, wherein the at least one different feature is an optical feature. 4. The radiation emitting device of claim 3, wherein the at least one different feature is transparency. 4. The radiation emitting device of claim 3, wherein the at least one different feature is a diffusivity. The radiation emitting device of claim 1, wherein the at least one different feature is a thermal feature. 7. The radiation emitting device of claim 6, wherein the at least one different feature is a coefficient of thermal expansion. 7. The radiation emitting device of claim 6, wherein the at least one different feature is specific heat. 7. The radiation emitting device of claim 6, wherein the at least one different thermal feature is a glass transition temperature. The radiation emitting device of claim 1, wherein the at least one different feature is a structural feature. 11. The radiation emitting device of claim 10, wherein the at least one different feature comprises at least one of tensile strength and compressive strength. The radiation emitting device of claim 1, wherein the at least one different feature is a compositional feature. The radiation emitting device of claim 1, wherein the radiation emitter is mounted on one of the first and second electrical leads. 2. The radiation emitting device of claim 1, further comprising a line junction extending from one of the first and second electrical leads to the radiation emitter. 2. The radiation emitting device of claim 1, wherein the at least one different feature comprises mechanical strength, thermal conductivity, heat capacity, specific heat, coefficient of thermal expansion, tackiness, oxygen impermeability, moisture impermeability, and the radiation. A radiation emitting device comprising at least one of the transmittances for radiation emitted from the emitter. The radiation emitting device of claim 1, wherein one of the regions is at least partially transparent to radiation emitted from the radiation emitter. The radiation emitting device according to claim 1, wherein one region of the enclosing portion is configured to be able to function as a lens. 2. The radiation emitting device of claim 1, wherein one of the first regions of the enclosing portion is configured to act as a lens. 19. The radiation emitting device of claim 18, wherein the second region of the enclosing portion is configured to hold the electrical lead. 20. The radiation emitting device of claim 19, wherein the lens is formed on one side of the enclosing portion that is different from a side on which the electrical leads extend. 21. The radiation emitting device of claim 20, wherein the side on which the lens is formed is opposite to the side on which the electrical leads extend. 21. The radiation emitting device of claim 20, wherein the side on which the lens is formed is adjacent to the side on which the electrical leads extend. The radiation emitting device according to claim 1, wherein the electrical lead is sonically solderable. The radiation emitting device according to claim 1, wherein the radiation emitter is an LED chip. The radiation emitting device according to claim 1, wherein the radiation emitter is a PLED. The radiation emitting device according to claim 1, wherein the radiation emitter is an OLED. 30. The radiation emitting device of claim 29, wherein said radiation emitter is an LED. The radiation emitting device of claim 1, wherein said radiation emitter is a semiconductor optical radiation emitter. 2. The radiation emitting device according to claim 1, wherein the at least one radiation emitter is a first radiation emitter and a second radiation emitter both enclosed by the enclosing part. 30. The radiation emitting device of claim 29, wherein said second radiation emitter is an LED chip. 30. The radiation emitting device of claim 29, wherein said second radiation emitter is a photoluminescent emitter. 30. The radiation emitting device of claim 29, wherein the first radiation emitter is an LED chip and the second radiation emitter is a photoluminescent emitter. 2. The radiation emitting device of claim 1, wherein the first region of the envelope is optically transparent and extends from a radiation emitter to a light output surface of the envelope. The radiation emitting device according to claim 1, wherein the second region has a lower thermal resistance than the first region. 2. The radiation emitting device of claim 1, wherein the second region has a greater thermal resistance than the first region. The radiation emitting device according to claim 1, wherein the second region has a greater mechanical strength than the first region. The radiation emitting device of claim 1, wherein the second region has a lower coefficient of thermal expansion than the first region. The radiation emitting device according to claim 1, wherein the second region has a greater adhesive strength than the first region. The radiation emitting device according to claim 1, wherein the second region has a lower oxygen transmission rate than the first region. 2. The radiation emitting device according to claim 1, wherein the second region has a lower moisture permeability than the first region. 2. The radiation emitting device of claim 1, wherein the second region has a higher specific heat than the first region. The radiation emitting device according to claim 1, wherein the first and second regions of the enclosing portion are cohesively bonded. 2. The radiation emitting device of claim 1, wherein said integral envelope is non-uniform. 2. The radiation emitting device of claim 1, wherein the electrical leads extend from the enclosure substantially non-perpendicular to the optical axis of the device. 2. The radiation emitting device of claim 1, wherein the first and second regions are made of different compositions, wherein a mixture of different composition gradients exists between the regions. 2. The radiation emitting device according to claim 1, wherein both of said regions of said envelope are made of a thermosetting material. The radiation emitting device according to claim 1, wherein the enclosing portion is integrally formed. The radiation emitting device of claim 1, further comprising a globe top distributed over the radiation emitter. 49. The radiation emitting device of claim 48, wherein said glove top comprises a photoluminescent material. In an optical radiation emitting device,
An optical radiation emitter;
First and second electrical leads electrically coupled to the optical radiation emitter, and integrally formed and configured to enclose the optical radiation emitter and a portion of the first and second electrical leads. An enclosing portion comprising a first composition that is substantially optically transparent to radiation emitted by the radiation emitter, and a second composition having properties different from the first composition. An optical radiation emitting device comprising: the enclosing unit. 51. The radiation emitting device of claim 50, wherein the first and second compositions are substantially separated into different regions of the envelope. 51. The radiation emitting device of claim 50, wherein the second composition is substantially opaque. 51. The radiation emitting device of claim 50, wherein said first composition is substantially transparent. 51. The radiation emitting device of claim 50, wherein the second composition has a greater thermal resistance than the first composition. 51. The radiation emitting device of claim 50, wherein the second composition has a greater heat capacity than the first composition. 51. The radiation emitting device of claim 50, wherein the second composition has a greater mechanical strength than the first composition. 51. The radiation emitting device of claim 50, wherein the second composition has a lower coefficient of thermal expansion than the first composition. 51. The radiation emitting device of claim 50, wherein the second composition has a greater adhesive strength than the first composition. 51. The radiation emitting device of claim 50, wherein said second composition has a lower oxygen transmission rate than said first composition. 51. The radiation emitting device of claim 50, wherein the second composition has a lower moisture permeability than the first composition. 51. The radiation emitting device of claim 50, wherein the second composition has a higher specific heat than the first composition. 51. The radiation emitting device of claim 50, wherein the first and second compositions are substantially separated into different regions of the encapsulation and are cohesively bonded at an interface between the regions. 51. The radiation emitting device of claim 50, wherein said optical radiation emitter is attached to one of said first and second leads. 51. The radiation emitting device of claim 50, wherein said radiation emitter is an LED chip. 51. The radiation emitting device of claim 50, wherein said radiation emitter is a semiconductor optical radiation emitter. 51. The radiation emitting device of claim 50, further comprising a globe top distributed over said optical radiation emitter. 67. The radiation emitting device of claim 66, wherein the glove top comprises a photoluminescent material. In a method for manufacturing a radiation emitting device,
Attaching and electrically coupling at least one radiation emitter to the leadframe to form a subassembly;
Inserting the sub-assembly into a mold cavity;
Partially filling the mold cavity with the first encapsulating material;
Filling the remainder of the mold cavity with a second encapsulating material;
Removing the encapsulated sub-assembly from the mold cavity. 69. The method of claim 68, further comprising partially curing the first encapsulant before filling the remaining portion of the mold cavity with the second encapsulant. 69. The method of claim 68, further comprising curing the first and second encapsulating materials before removing the encapsulated subassembly from the mold assembly. 69. The method of claim 68, wherein the first encapsulant is substantially transparent to radiation emitted by the radiation emitter. 70. The method of claim 68, wherein the second encapsulating material is opaque. 70. A radiation emitter device manufactured by the method of claim 68. In the light emitting device,
At least one LED chip;
First and second electrical leads electrically coupled to the LED chip;
An integrated encapsulation configured to enclose a portion of the LED chip and a portion of the first and second electrical leads, comprising at least one transparent first and second region. The integrated envelope, wherein the second region has a higher thermal conductivity than the first region.

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