Patent Application
20150060929
1. Field of the Invention
The present invention relates generally to circuit boards and more particularly, to a ceramic circuit board and an LED package module using the ceramic circuit board.
2. Description of the Related Art
A conventional ceramic circuit board primarily comprises a substrate made of ceramic material, and a plurality of electro-conductive wires mounted on an exterior surface of the substrate. Because the substrate made of ceramic material is higher in thermal conductivity, heat resistance and electric insulativity than traditional substrates, the ceramic circuit board is applicable in electrical products having high heat-emitting rate, such as high-brightness LED.
In a manufacturing process of the ceramic circuit board, a seed layer is at first provided on the exterior surface of the substrate by sputtering with an electro-conductive material such as copper. After that, the electro-conductive wires are developed on the seed layer by photolithography and electroplating with a metal material such as copper. At this time, the electro-conductive wires can optionally be plated with bonding pads at predetermined positions according to applications of the ceramic circuit board, such as LED package modules. After that, spare parts of the seed layer exposed on the exterior surface of the substrate without being covered by the electro-conductive wires are removed by etching.
In the aforesaid ceramic circuit board, the electro-conductive wires are protruded from the exterior surface of the substrate, resulting in structural infirmness of the ceramic circuit board. At present, electronic elements are tending to be miniaturized in size, so the electro-conductive wires of the ceramic circuit board are correspondingly developed thinner and thinner. However, the thinner the electro-conductive wire is, the smaller connecting area and the less structural firmness are between the electro-conductive wire and the substrate. Besides, when the aforesaid spare parts of the seed layer are removed, the other parts of the seed layer located between the electro-conductive wires and the substrate are liable to be removed fractionally, resulting in further decrease of the structural firmness between the electro-conductive wires and the substrate. In addition, the width and the thickness of the electro-conductive wire are respectively limited by usage requirement and sputtering, so the electro-conductive wire can only carry a small electric current.
The present invention has been accomplished in view of the above-noted circumstances. It is an objective of the present invention to provide a ceramic circuit board wherein an electro-conductive wire is mounted to a substrate firmly and capable of carrying a relatively larger electric current.
To attain the above objective, the present invention provides a ceramic circuit board which comprises a substrate and an electro-conductive wire. The substrate is made of aluminum oxide (Al2O3) or aluminum nitride (AlN) and has an exterior surface and a groove recessed from the exterior surface. The groove has a bottom surface provided with an arithmetic mean roughness (hereinafter referred to as “roughness Ra”) of 1-20 μm, a plurality of crests and a plurality of troughs. The crests are substantially located in an imaginary plane substantially parallel to and separated from the exterior surface at a distance of 1-100 μm. The electro-conductive wire is embedded in the groove of the substrate and has a top surface substantially flush with the exterior surface of the substrate.
As a result, the electro-conductive wire is completely located in the groove of the substrate; besides, the groove is quite deep and the bottom surface of the groove is quite lumpy. Therefore, the connection between the electro-conductive wire and the substrate is relatively firmer. In addition, the electro-conductive wire can be made quite thick for carrying a relatively larger electric current.
It is another objective of the present invention to provide an LED package module which is firm in structure and capable of carrying relatively larger electric currents.
To attain the above objective, the present invention provides an LED package module which comprises a substrate, two electro-conductive wires, two bonding pads and an LED chip. The substrate is made of aluminum oxide (Al2O3) or aluminum nitride (AlN) and has an exterior surface and two grooves recessed from the exterior surface. Each of the grooves has a bottom surface provided with a roughness Ra of 1-20 μm, a plurality of crests and a plurality of troughs. The crests are substantially located in an imaginary plane substantially parallel to and separated from the exterior surface at a distance of 1-100 μm. Said two electro-conductive wires are embedded in said two grooves of the substrate respectively. Each of the electro-conductive wires has a top surface substantially flush with the exterior surface of the substrate. Said two bonding pads are mounted on the top surfaces of said two electro-conductive wires, respectively. The LED chip has two contacts electrically connected with said two bonding pads, respectively.
As a result, the electro-conductive wires are connected with the substrate relatively more firmly and can be made thicker than electro-conductive wires of a conventional ceramic circuit board so that the electro-conductive wires in the present invention are capable of carrying relatively larger electric currents. Therefore, the LED package module is firm in structure and capable of carrying relatively larger electric currents.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:
Referring to
The substrate 20 is made of a ceramic material, including aluminum oxide (Al2O3) and aluminum nitride (AlN), and has an exterior surface 22 and two grooves 24 recessed from the exterior surface 22. Each of the grooves 24 has a bottom surface 242 provided with a roughness Ra of 1-20 μm. This means in microscopic view, the bottom surface 242 of each groove 24 is lumpy and has a plurality of crests 242a and a plurality of troughs 242b. The crests of the bottom surface 242 of each groove 24 are approximately located in an imaginary plane P which is approximately parallel to the exterior surface 22 and separated from the exterior surface 22 at a distance of 1-100 μm. In other words, each groove 24 can be defined with a depth D which is the distance between the imaginary plane P and the exterior surface 22 and ranged from 1 μm to 100 μm.
Said two electro-conductive wires 30 are made of metals having high electric conductivity, such as copper (Cu), silver (Ag) or gold (Au), and embedded in said two grooves 24, respectively. Each of the electro-conductive wires 30 has a top surface 32 approximately flush with the exterior surface 22 of the substrate 20. In other words, the electro-conductive wires 30 are complementary in shape to the grooves 24 of the substrate 20. In this embodiment, each of the electro-conductive wires 30 has a rectangular first bonding portion 34, a rectangular second bonding portion 36 narrower than the first bonding portion 34, and a connecting portion 38 connecting the first and second bonding portions 34, 36.
It will be appreciated that the electro-conductive wires 30 shown in
In fact, the characteristics of the present invention are the depth D of the grooves 24, the roughness of the bottom surfaces 242 of the grooves 24, and a feature that the electro-conductive wires 30 are completely embedded in the grooves 24 and flush with the exterior surface 22 of the substrate 20. The amounts of the grooves 24 and the electro-conductive wires 30 and their shapes shown on the exterior surface 22 are not limited but modifiable according to different applications.
Said two bonding pads 50 are plated and mounted on the top surfaces 32 of said two electro-conductive wires 30, respectively. In this embodiment, said two bonding pads 50 are located on a pair of adjacent said first and second bonding portions 34, 36 (referring to
The LED chip 60 is fixed to said two bonding pads 50 in a way of flip chip bonding. That is, the LED chip 60 has two contacts 62 protruding downward and fastened to said two bonding pads 50 respectively by welding. In this way, said two contacts 62 are electrically connected with said two bonding pads 50 respectively so as to be electrically connected with said two electro-conductive wires 30 respectively.
In the ceramic circuit board 10, the electro-conductive wires 30 are completely located in the grooves 24 of the substrate 20 and made quite thick because the grooves 24 are quite deep (depth D is 1-100 μm); besides, the bottom surfaces 242 of the grooves 24 are quite lumpy (roughness Ra is 1-20 μm). Therefore, the connection between each electro-conductive wire 30 and the substrate 20 is very firm, and the electro-conductive wire 30 is capable of carrying a relatively larger electric current because of relatively larger thickness thereof. Due to the aforesaid characteristics of the ceramic circuit board 10, the LED package module 40 is firm in structure and capable of carrying relatively larger electric currents.
In fact, the roughness Ra of the bottom surface 242 of each groove 24 is preferably in a range of 1-10 μm and more preferably in a range of 5-10 μm for achieving firmer connection between the electro-conductive wire 30 and the substrate 20. In addition, the depth D of each groove 24, i.e. the distance between the imaginary plane P and the exterior surface 22, is preferably in a range of 1-70 μm and more preferably in a range of 1-30 μm to minimize the quantity of metal used for electro-conductive wires 30 and time for electroplating so as to lower manufacturing cost.
In the following paragraphs, results of manufacturing ceramic circuit boards practiced by the inventor of the present invention will be disclosed and verify that the aforesaid numerical ranges of features in the present invention can cause a good result that the electro-conductive wires are fixed to the substrate firmly.
In the first comparative ceramic circuit board 71 shown in
In the second comparative ceramic circuit board 72 shown in
In the third comparative ceramic circuit board 73 shown in
Referring to a table 1 below, wherein first to sixth examples of ceramic circuit board of the present invention are listed, the depths D of the grooves in the examples are different from each other but all in the range of 1-100 μm and the roughness Ra of the bottom surface in the groove of each example is in the range of 1-20 μm.
The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102216723 | Sep 2013 | TW | national |
