专利汇可以提供METHOD AND NOZZLE FOR HERMETICALLY SEALED PACKAGED DEVICES专利检索,专利查询,专利分析的服务。并且Microelectromechanical systems (MEMS) such as digital micromirror devices (DMD) are manufactured in arrays. Covers, packages, and lids are placed around each device and a liquid such as epoxy resin is dispensed around the packaged device. The epoxy resin acts as a sealant to form a hermetic seal. A nozzle comprises multiple orifices along a sidewall of the nozzle to dispense the epoxy resin horizontally and parallel to the plane of the wafer substrate. The distal ends of the nozzle are enclosed.,下面是METHOD AND NOZZLE FOR HERMETICALLY SEALED PACKAGED DEVICES专利的具体信息内容。
What is claimed is:
This relates generally to semiconductor devices packaged at the wafer level such as microelectromechnical systems (MEMS) and digital micromirror devices (DMD).
MEMS devices integrate very small mechanical devices with semiconductors to form sensors (temperature, pressure, gas, moisture, and motion), accelerometers, valves, gears, actuators, and micromirror devices. MEMS are often sensitive to the environment and may require a hermetically sealed package to be isolated.
A package comprises a MEMS device mounted on a packaging substrate such as plastic or ceramic, wires attached to bond pads, and a cover to enclose the device. U.S. Pat. No. 7,491,567 B2 describes one method for enclosing the MEMS by inserting the supporting substrate with mounted device into a cavity formed by the packaging. Anther method of packaging places a cover over the supporting substrate and mounted device and attaches the cover to the substrate.
A digital micromirror device (DMD), such as a Texas Instruments DLP® micromirror device, is a type of MEMS device which uses an array of individually positionable mirrors to project an image onto a display panel. The array of mirrors is fabricated above CMOS substrate wafers using a material such as silicon. Each device typically comprises multiple mirrors and multiple devices are formed on the wafer substrate in a grid array pattern. Scribe lines are etched onto the wafer substrate and form clearly defined lines which can be used to more easily singulate each packaged device. The bottom surface of the CMOS supporting substrate is bonded to another substrate, typically silicon, for additional mechanical strength. Upon completion of the MEMS fabrication process, wires are attached from the device to the bond pads and transmit signals. The bonding wires are easily damaged or dislodged. Various methods can be used to contain semiconductor and micromirror devices and bonding wires, which are also attached to substrates. One method is to deposit encapsulation material above the device and wires to enclose and cover the assembly. Various types of covers can be placed around the device and wires. The substrate is singulated once the devices are packaged.
In the case of a DMD, the package protects the micromirror device while also forming an optically transparent window above the device. The device is able to receive an incoming signal and project an image through the optically transparent window and onto a display panel. The cover surrounding the micromirror device protects the bonding wires and the DMD but also prevents extraneous illumination from being incident onto the mirrors arrayed on the device.
The mirror 102 is in an “ON” state. It is tilted towards a pad 106 on the silicon substrate 108. Light 110 is incident onto the mirror 102 and reflected light 112 is projected onto a display system to form an image. The “ON” state is equivalent to a digital “1”.
The mirror 104 is in an “OFF” state. The mirror 104 is tilted toward a pad 114 on the substrate 108. Light 116 is incident upon the mirror 104 and reflected light 118 is projected away from the display system. The “OFF” state is equivalent to a digital “0” because no image is sent for display.
Over time, as DMD devices become smaller, the dimensions of the area surrounding the packaged devices are reduced. Spacing between adjacent packaged device is smaller and more difficult for nozzles to access. The lumens used to project the optical image is increased to improve the visibility of the image but higher lumens also increases the visibility of any optical artifacts.
Light leaks into the packaged micromirror device 200 through the gap 212. The leaked light may be projected onto a display depending on the angle of incident light and the size of the gap 212 and the quality of the image reduced by the presence of leaked light.
It is desired to dispense an epoxy based liquid or similar material in proximity to the cover 202 and as a sealant between the cover 202 and the package 204. Dimensions 402, 404, 406 and 408 are small and dispensing of materials can be difficult.
As devices shrink, dimensions 508, 510, and 512 are also reduced. The reduction in space between adjacent packaged devices 504 increases the probability of a notch or gap because typical nozzles are unable to fully access the required locations for fluid coverage. More importantly, a hermetic seal is not formed when the fluid cannot be dispensed correctly.
Encapsulation liquids are viscous and self-leveling. They are typically dispensed using a nozzle placed directly above the part being sealed. The nozzle is attached to an automated system which is programmed to follow a defined path above the substrate. At predefined intervals along the path, material is dispensed through the nozzle. The height of the package and spacing between adjacent packages can cause difficulty in dispensing. Both narrow spacing between adjacent packaged device 504 and the height of the packaged device 504 may prevent a typical nozzle from dispensing material at the required location to form a hermetic seal.
The nozzle 600 is limited by its length 602 which is smaller the than height 512 and unable to access the plane of the substrate 502. The nozzle 600 is also limited by the width of its diameter 606 at the dispensing orifice 604 which is larger than widths 508 and 510.
In nozzle 630, the liquid is dispensed horizontally and parallel to the plane of the wafer substrate. Horizontal dispensing is an advantage in directing the fluid to the cover edge. However, the length 648 is longer than dimensions 508 and 510, and nozzle 630 is unable to reach within the spacing between adjacent packaged devices 504.
This method supports packaging of semiconductor substrate devices placed in close proximity.
A nozzle and method for hermetically sealing packaged devices. A sealant, such as an epoxy resin, is sprayed using a nozzle onto the sidewall of a packaged device prior to singulation (while still in wafer form). The nozzle comprises multiple dispensing orifices along its sidewall. The nozzle may be comprised of one or more sets of multiple dispensing orifices on one or both opposing sides of the nozzle wall. The nozzle is comprised of dimensions which allow it to more easily access a packaged device or be inserted between packaged devices.
Example embodiments are described with reference to accompanying drawings, wherein:
Quality and reliability of MEMS can be improved by being able to insert nozzles and dispense packaging materials more fully between adjacent micromirror devices, repeatedly and consistently using a high speed and automated dispensing system, and to dispense controlled amounts of liquid in a horizontal direction parallel to the plane of the wafer substrate. Horizontal dispensing allows improved dispensing on packaging edges.
A typical approach for forming a hermetic seal around a MEMS package is to dispense epoxy or other liquid from above the packaged device using a nozzle controlled by an automated system programmed to follow a predefined path. The method of dispensing controlled drops of liquid requires precise placement such that excessive material is not deposited on nor does it migrate onto scribe lines. Epoxy or other material deposited across scribe lines may cause unwanted cracks and defects when the packaged devices are singulated or cause the scribe lines not to fracture as intended. Excessive deposited material can also cause mechanical stress across the substrate wafer which may damage the packaged device or cause the substrate wafer to bow under stress. Uniform thickness of deposited material improves the singulation process.
A new type of nozzle can improve the precision and accuracy of dispensing while also improving the coverage of dispensed material by spraying in a direction parallel to the plane of the substrate.
The nozzle 700 is inserted adjacent to the packaged device 504. A sealant material such as epoxy is sprayed from sidewall orifices 710 and 714 onto the device 504. The volume of liquid dispensed is precisely controlled for consistent and repeatable device packaging. After dispensing, the nozzle 700 is moved vertically upwards from the packaged device 504 and to its next programmed location, is inserted adjacent to another device 504, and repeats the spraying action. The epoxy is cured after being sprayed.
Orifices 810 and 816 are a distance 822 from the distal end 808 and orifices 812 and 818 are a distance 824 from the distal end 808. The placement of sidewall orifices 810 and 816 may be adjusted to device dimensions.
It is possible that the nozzles 700 and 800 comprise more than two orifices on each side or that the distal ends 708 and 808 comprise an additional orifice for spraying in a vertical direction perpendicular to the plane of the substrate.
Nozzle 920 is inserted between adjacent packaged devices 504, epoxy is sprayed from orifices 810 and 814 and orifices 816 and 820 onto foam 902. The sum of width 804 of nozzle 920 and twice the width 910 of the foam 902 is less than widths 506 and 508 of the packaged device 504. Foam 902 is placed in contact with each side of two adjacent devices 504. Nozzle 920 is moved vertically or horizontally. Nozzle 920 is used in a brushing motion to place epoxy onto the two adjacent devices 504. The foam 902 is typically consumed with time and replaced as necessary.
Nozzle 600 or nozzle 800 may be more suitable for use at the perimeter of the device array 1000. Within the device array 1000, nozzle 800 or nozzle 920 are better configured to process two adjacent packaged devices 504 simultaneously.
Those skilled in the art to which the invention relates will appreciate that modifications may be made to the described example embodiments, and also that many other embodiments are possible, within the scope of the claimed invention.
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