A high-power flip-chip LED PAD structure

Abstract

This utility model relates to the field of LED structure technology, specifically to a high-power flip-chip LED PAD structure. The PAD structure includes a PAD and a gap strip disposed in the middle of the PAD, wherein the width at both ends of the gap strip is greater than the width at the center of the gap strip. This PAD structure improves the stress trend of the metal film layer and avoids deformation of the photomask by reducing the aspect ratio of the photomask.

Description

Technical Field

[0001] This utility model relates to the field of LED structure technology, specifically to a high-power flip-chip LED PAD structure. Background Technology

[0002] Flip-chip bonding often uses gold-tin eutectic bonding to achieve chip bonding, while horizontal and vertical chips can be bonded using conductive silver paste, lead-free solder paste, etc. Compared to silver paste and lead-free solder paste, gold-tin eutectic bonding has higher bonding strength, better interface quality, and higher thermal conductivity of the bonding layer, thus reducing the thermal resistance of LEDs (light-emitting diodes).

[0003] In addition to the outermost gold-tin eutectic layer, flip chips are typically layered with other metal films deposited alternately as the bottom layer, with Ni being a commonly used metal. Ni has high stress, and to ensure chip reliability, the Ni film thickness is often designed to be relatively thick. This results in thicker PAD (pad) deposition, which can easily lead to photoresist roll-up, causing abnormal deposition patterns and resulting in inconsistencies between the chip's appearance and the design, thus reducing chip yield. Utility Model Content

[0004] The technical problem to be solved by this utility model is to provide a high-power flip-chip LED PAD structure that improves the stress trend of the metal film layer.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is as follows: A high-power flip-chip LED PAD structure, including a PAD and a GAP strip (spacer strip) disposed in the middle of the PAD, wherein the width at both ends of the GAP strip is greater than the width at the center of the GAP strip.

[0006] The GAP strip includes a rectangular portion and at least two circular portions, with the short side of the rectangular portion connecting two adjacent circular portions respectively.

[0007] The diameter of the circular portion is at least 1.5 times the shorter side of the rectangular portion.

[0008] The center-to-center distance between two adjacent circular portions is at least 200 μm.

[0009] The number of GAP strips is at least two.

[0010] The distance between two adjacent GAP strips is greater than 250 μm.

[0011] At least two adjacent GAP strips are connected at one end.

[0012] The GAP strip in the middle is shorter than the other GAP strips.

[0013] One end of the GAP strip is positioned on the long side of the PAD.

[0014] The length of the GAP strip is less than or equal to 4 / 5 of the width of the PAD.

[0015] The beneficial effects of this invention are as follows: by reducing the aspect ratio of the photomask (GAP strip pattern), this invention improves the stress trend of the metal film layer and avoids deformation of the photomask roll. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the high-power flip-chip LED PAD structure according to Embodiment 1 of this utility model;

[0017] Label Explanation:

[0018] 1. PAD; 2. GAP strip; 21. Rectangular part; 22. Circular part. Detailed Implementation

[0019] To explain in detail the technical content, objectives, and effects of this utility model, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0020] A high-power flip-chip LED PAD structure includes a PAD and a GAP strip disposed in the middle of the PAD, wherein the width at both ends of the GAP strip is greater than the width at the center of the GAP strip.

[0021] As can be seen from the above description, the GAP strip of this utility model serves as a separation zone between P and N electrodes. The bottom layer of the GAP region is the N electrode region. To avoid P / N short circuits, it is necessary to avoid depositing metal electrodes on the GAP region.

[0022] Photomasks are used to deposit metal films of a specified shape on chips. Photomask patterns with a large aspect ratio result in higher stress in the metal film formed during the deposition process, easily leading to warping and deformation of the photomask at the short edges. This invention reduces the aspect ratio of the photomask by limiting the width at both ends of the GAP strip (i.e., the photomask pattern) to be greater than the width at the center of the GAP strip. This improves the stress distribution of the metal film, preventing warping and reducing the proportion of gold defects caused by deposition from 80% to 0%, significantly improving the yield rate.

[0023] Furthermore, the GAP strip includes a rectangular portion and at least two circular portions, with the short side of the rectangular portion connecting to two adjacent circular portions respectively.

[0024] The circular and rectangular parts overlap to form a single structure.

[0025] As described above, photomask warpage mainly occurs at the edges of the short sides, extending from the edges towards the center. If warpage does not occur at the short sides, warpage will not occur in the middle area of ​​the photomask. This invention reduces the aspect ratio of the photomask by combining multiple patterns, thus preventing the photomask from warping at the edges of the short sides during evaporation.

[0026] Furthermore, the diameter of the circular portion is at least 1.5 times the shorter side of the rectangular portion.

[0027] As can be seen from the above description, reducing the diameter of the circle increases the risk of warping and deformation of the photoresist mask.

[0028] Furthermore, the center-to-center distance between two adjacent circular portions is at least 200 μm.

[0029] Furthermore, the number of gaps must be at least two.

[0030] Furthermore, the distance between two adjacent GAP stripes is >250μm.

[0031] Furthermore, at least two adjacent gap strips are connected at one end.

[0032] Furthermore, the GAP strip located in the middle is shorter than the other GAP strips.

[0033] Furthermore, one end of the GAP strip is positioned on the long side of the PAD.

[0034] Furthermore, the length of the GAP strip is less than or equal to 4 / 5 of the width of the PAD.

[0035] Please refer to Figure 1 The first embodiment of this utility model is: a high-power flip-chip LED PAD structure, including PAD1 and five GAP strips 2 arranged in the middle of PAD1. The length of the GAP strip 2 is 4 / 5 of the width of PAD1; the distance between two adjacent GAP strips 2 is 260μm, and the length of the middle GAP strip 2 is shorter than the length of the other GAP strips 2.

[0036] GAP strip 2 includes two rectangular portions 21 and three circular portions 22. The circular portions 22 and rectangular portions 21 partially overlap and form an integral structure. The short sides of the rectangular portions 21 are connected to two adjacent circular portions 22 respectively. The diameter of the circular portion 22 is 1.5 times the diameter of the short side of the rectangular portion 21. The center-to-center distance between two adjacent circular portions 22 in the middle GAP strip 2 is 200μm and 100μm respectively. The center-to-center distance between two adjacent circular portions 22 in the other GAP strips 2 is 200μm. One end of the GAP strip 2 is set on the long side of PAD1, and the ends of the three middle GAP strips 2 near the long side of PAD1 are connected.

[0037] In summary, the high-power flip-chip LED PAD structure provided by this utility model reduces the aspect ratio of the photomask, avoiding the deformation of the photomask roll during evaporation, thereby reducing the proportion of gold defects caused by evaporation from the original 80% to 0%, and greatly improving the appearance yield.

[0038] The above description is merely an embodiment of this utility model and does not limit the patent scope of this utility model. Any equivalent modifications made based on the content of this utility model specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of this utility model.

Claims

1. A high power flip-chip LED (P AD) structure, characterized in that, The device includes a pad and a gap strip located in the middle of the pad. The width of the gap strip at both ends is greater than the width of the center of the gap strip. The gap strip includes a rectangular portion and at least two circular portions. The short side of the rectangular portion connects to two adjacent circular portions. The diameter of the circular portion is at least 1.5 times the short side of the rectangular portion.

2. The high-power flip-chip LED PAD structure according to claim 1, characterized in that, The center-to-center distance between two adjacent circular portions is at least 200 μm.

3. The high-power flip-chip LED PAD structure according to claim 1, characterized in that, The number of GAP strips is at least two.

4. The high-power flip-chip LED PAD structure according to claim 3, characterized in that, The distance between two adjacent GAP strips is >250μm.

5. The high-power flip-chip LED PAD structure according to claim 3, characterized in that, At least two adjacent GAP strips are connected at one end.

6. The high-power flip-chip LED PAD structure according to claim 3, characterized in that, The middle gap strip is shorter than the other gap strips.

7. The high-power flip-chip LED PAD structure according to claim 1, characterized in that, One end of the GAP strip is positioned on the long side of the PAD.

8. The high-power flip-chip LED PAD structure according to claim 7, characterized in that, The length of the GAP strip is less than or equal to 4 / 5 of the width of the PAD.

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