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Underfill process for flip-chip LEDs

A technology of flip-chip and underfill materials, which is applied in the direction of electrical components, electric solid devices, circuits, etc., can solve problems such as LED cracking, and achieve the effect of reducing the time of underfill process

Active Publication Date: 2011-06-01
LUMILEDS HLDG BV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Also, since the void region does not support the LED during the laser lift-off process, the downward stress on the LED during the laser lift-off process can crack the LED

Method used

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  • Underfill process for flip-chip LEDs
  • Underfill process for flip-chip LEDs
  • Underfill process for flip-chip LEDs

Examples

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Embodiment Construction

[0037]As a preliminary matter, conventional LEDs were formed on a growth substrate. In the example used, the LEDs are GaN-based LEDs for producing blue light, such as AlInGaN or InGaN LEDs. Typically, a relatively thick n-type GaN layer is grown on a sapphire growth substrate using conventional techniques. Relatively thick GaN layers typically include a low temperature nucleation layer and one or more additional layers to provide a low defect lattice structure for the n-type cladding and active layers. Then, one or more n-type cladding layers are formed on the thick n-type layer, followed by an active layer, one or more p-type cladding layers, and a p-type contact layer (for metallization).

[0038] For flip-chip, portions of the p-layer and active layer are etched away to expose the n-layer for metallization. In this way, the p-contact and n-contact are on the same side of the chip and can be electrically attached directly to the base contact pads. Current from the n-metal...

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Abstract

An underfill technique for LEDs (10, 12) uses compression molding (50) to simultaneously encapsulate an array of flip-chip LED dies mounted on a submount wafer (22). The molding process causes liquid or softened underfill material (41) to fill the gap between the LED dies and the submount wafer. The underfill material is then hardened, such as by curing. The cured underfill material (54) over thetop and sides of the LED dies is removed using microbead blasting (58). The exposed growth substrate (12) is then removed from all the LED dies by laser lift-off (60), and the underfill supports the brittle epitaxial layers (10) of each LED die during the lift-off process. The submount wafer is then singulated. This wafer-level processing of many LEDs simultaneously greatly reduces fabrication time, and a wide variety of materials may be used for the underfill since a wide range of viscosities is tolerable.

Description

technical field [0001] The present invention relates to flip chip light emitting diodes (LEDs), and in particular to a process for providing a dielectric underfill material in the gap between an LED chip and its submount. Background technique [0002] Prior Art FIG. 1 shows a conventional LED 10 flip-chip mounted on a portion of a submount wafer 22 . In flip chip, the n and p contacts are formed on the same side of the LED die opposite the growth substrate 12 side. [0003] In FIG. 1 , an LED 10 is formed of a semiconductor epitaxial layer including an n layer, an active layer, and a p layer grown on a growth substrate 12 such as a sapphire substrate. In one example, the epitaxial layer is GaN based and the active layer emits blue light. Any other type of flip-chip LEDs can be applied to the present invention. [0004] A metal electrode 14 electrically contacting the p-layer is formed on the LED 10 and a metal electrode 16 electrically contacting the n-layer is formed on ...

Claims

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Application Information

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IPC IPC(8): H01L33/00H01L33/54H01L33/56
CPCH01L33/54H01L33/56H01L33/0079H01L24/97H01L2224/16225H01L2224/32225H01L2224/73204H01L33/0093H01L2924/00
Inventor G·巴辛F·戴纳P·S·马丁D·西莫尼安
Owner LUMILEDS HLDG BV
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