PCB for LED and Method for Making the Same, Light Emitting Device and Luminaire

Technical Field

The present invention relates to a PCB for LED and a method for making the same, a light emitting device, a light emit ^¬ ting apparatus and a luminaire. Background Art

As a new energy, LED luminaries have been widely used due to advantages such as high efficiency, pure light color, low en ^¬ ergy consumption, long service life, reliability and endura- bility, no-pollution and flexible control. Currently, LED- based luminaires have replaced traditional light sources such as incandescent luminaire, fluorescent luminaire and HID lu ^¬ minaire .

For LED-based luminaires, one key part is the PCB (printed circuit board) . Fig. 1 shows a traditional PCB structure 100 comprising a substrate 101, an insulating layer 103, a copper layer 105 on the insulating layer 103 and a solder mask 107 on the copper layer 105. The LED will be electrically connected through the patterned copper layer 107 on the PCB, so as to realize the serial/parallel connection between the LEDs and the con ^¬ nection with the power supply.

The solder mask 107 can usually be formed with a liquid pho- tosenstive material which can be cured after being roasted. The solder mask is a patterned layer and is used to cover the overall surface of the PCB except the solder pad. For most applications of the LED, the solder mask is formed in a white color so that the light absorption is minimized. The method for forming the known PCB in Fig. 1 will be described hereinafter referring to Figs. 2a-2d.

First, the substrate 101 and the insulating layer 103 are prepared, and the copper layer 105 is formed on the insulat ^¬ ing layer 103. Then, as shown in Fig. 2a, the copper layer 105 is patterned for electrical connection with the LED.

Then, as shown in Fig. 2b, the photosensitive material is ap ^¬ plied to the overall surface.

Subsequently, as shown in Fig. 2c, some area is shielded us- ing the patterned mask 109, and the photosensitive material is exposed under UV light.

Then, as shown in Fig. 2d, the patterned mask 109 is removed and the overall device is immersed in a developer. The pho ^¬ tosensitive material in the exposed area will be removed and the photosensitive layer 107 is patterned.

However, the PCB formed with this solution has drawbacks. Specifically, the reflectivity of the photosensitive layer 107 formed of the photosensitive material usually is not high due to the material limitation and is typically less than 80%. In addition, as shown in Fig. 3, in some applications of the LED, for example, comprising a diffusion cover 110 (especially a remote-phosphor cover) , most of the light 120 is scattered back by the diffusion cover 110 and will be ab ^¬ sorbed due to the low reflectivity of the material of the photosensitive layer 107 on the surface of the PCB, thereby rendering light loss and then a low optical efficiency.

To make improvements to this situation, a known method is to cover a patterned high-reflectivity sheet over the PCB, and the high-reflectivity sheet exposes the surface of the PCB and out of the LED, so that it reflects the light from the LED. Usually, the reflecting sheet will be first adhered to PCB using an adhesive and is further fixed on the PCB using a screw. This solution at least has following drawbacks:

1. Patterning of the reflecting sheet should be conducted us ^¬ ing a stamping machine, and different molds are needed for different patterns, thus the production is difficult and the cost is high;

2. The assembling of the reflecting sheet is difficult and not reliable. Use of the screws adds extra work, and the screws will also absorb light during the operation of the LED and then lowers optical efficiency. Use of the adhe ^¬ sive renders the structure unreliable, especially in a situation of high temperature or after long service period; and

3. The reflecting sheet is usually casted with an expensive material and formed by mechanical processing, and thus the cost is very high.

Summary of the Invention

The present invention aims to overcome the drawbacks in the prior art and then provides a PCB for LED and a method for making the same, a light emitting device, a light emitting apparatus and a luminaire, and thus provides fine reflectiv ^¬ ity so as to minimize absorption of light from the LED.

According to an aspect of the present invention, a PCB for LED is provided, comprising: an insulating base; and a metal layer located above the insulating base and comprising a pat ^¬ tern for electrical connection with the LED, and the PCB further comprises a reflecting layer formed of a non- photosensitive reflecting material which reflectivity is greater than 80%, and the reflecting layer is located on the metal layer to reflect the light from the LED.

Furthermore, the reflecting layer is formed of a polyester material .

Furthermore, the reflecting layer is formed of Interpon 600 powder.

Furthermore, the thickness of the reflecting layer is formed to be 60 μιη.

Furthermore, the reflecting layer is formed by sputtering the powder on the metal layer. Furthermore, the reflectivity of the reflecting layer is at least 93%.

Furthermore, the pattern of the reflecting layer is formed to correspond to that of the metal layer.

Furthermore, the metal layer is copper layer. Furthermore, the reflecting layer is an insulating layer. According to another aspect of the present invention, a method for making a PCB for LED is provided, and the method comprises following steps: (a) preparing an insulating base; (b) forming a metal layer on the insulating base, and pat- terning the metal layer for electrical connection with the LED; (c) providing a blocking layer on the metal layer, wherein, the pattern of the blocking layer is formed to expose the metal layer; (d) covering a non-photosensitive re ^¬ flecting material, which reflectivity is greater than 80%, over the metal layer and the blocking layer; and (e) removing the blocking layer and a part which covers the reflecting material and is located on the blocking layer, so as to form a reflecting layer for reflecting light from the LED.

Furthermore, the step (c) comprises adhering an LED mock-up with an adhesive material to the metal layer to be used as the blocking layer.

Furthermore, the step (c) further comprises following steps: (cl) coating a photoresist on the metal layer; (c2) providing an etching mask on the photoresist; (c3) etching the photore- sist with UV light; and (c4) removing the etching mask and thus forming the photoresist layer as the blocking layer.

Furthermore, in the step (cl), the photoresist is a negative photoresist, and in the step (c2), the etching mask comprises a pattern which is the same with that of the metal layer. Furthermore, in the step (cl), the photoresist is a positive photoresist, and in the step (c2), the etching mask is formed to expose the metal layer.

Furthermore, the step (d) comprises sputtering a reflecting powder on the metal layer and the blocking layer. Furthermore, there is a step which follows the step (d) and comes before the step (e) : (f) heating the PCB in a heating chamber or on a heating plate, so that the sputtered reflect ^¬ ing powder is cured. Furthermore, a following step is conducted when the step (e) is being conducted: (f) heating the PCB in a heating chamber or on a heating plate, so that the sputtered reflecting pow ^¬ der is cured.

Furthermore, the reflectivity of the reflecting layer is at least 93%.

Furthermore, the reflecting layer is formed of a polyester material .

Furthermore, the reflecting layer is formed of Interpon 600 powder . Furthermore, the thickness of the reflecting layer is βθμιη.

Furthermore, the metal layer is copper layer.

According to still another aspect of the present invention, an LED light emitting device is provided, the LED light emit ^¬ ting device comprises any of the above PCBs for the LED and the LED, and the LED is electrically connected with the metal layer through the pattern of the metal layer.

According to still another aspect of the present invention, a light emitting apparatus is provided, the light emitting ap ^¬ paratus comprises the above LED light emitting device. According to still another aspect of the present invention, a luminaire is provided, the luminaire comprises the above light emitting apparatus.

By way of the embodiments of the present invention, at least one or several of the following effects can be achieved:

1. the reflectivity of the reflection layer is high and can reach at least 93%, so that absorption of the light is minimized;

2. unlike the prior art, the complex apparatuses and proc ^¬ esses such as the stamping machine need not be used, thus easy automation and mass-production can be achieved;

3. the final assembly does not need any screw or adhesive, so that the assembling is simple and reliable;

4. the present invention uses a material with a high reflec ^¬ tivity while a low cost, and thus the product cost is greatly lowered; and

5. The present invention has high reflectivity while fine in ^¬ sulation property, and can bear a large alternating current, so that the reliability of the PCB is further im ^¬ proved .

Brief Description of the Drawings

The accompanying drawings constitute a part of the present Description and are used to provide further understanding of the present invention. Such accompanying drawings illustrate the embodiments of the present invention and are used to de ^¬ scribe the principles of the present invention together with the description. In the accompanying drawings the same com- ponents are represented by the same reference numbers. As shown in the drawings :

Fig. 1 illustrates a cross section view of the PCB for LED comprising a photosensitive material according to the prior art;

Figs. 2a-2d are cross section views showing the method for making the PCB for LED comprising a photosensitive material according to the prior art;

Fig. 3 illustrates a cross section view of the PCB for LED comprising a photosensitive material according to the prior art which produces light loss;

Fig. 4 illustrates cross section view of the PCB for LED comprising a high-reflectivity material according to the embodi ^¬ ments of the present invention; Figs. 5a-5d are cross section views showing the method for making the PCB for LED comprising a high-reflectivity mate ^¬ rial according to the first embodiment of the present inven ^¬ tion; and

Figs. 6a-6f are cross section views showing the method for making the PCB for LED comprising a high-reflectivity mate ^¬ rial according to the second embodiment of the present inven ^¬ tion.

Detailed Description of the Embodiments

The present invention will be described hereinafter more com- prehensively referring to the accompanying drawings illus ^¬ trating the explanatory embodiments of the present invention. However, the present invention can be implemented in many different manners and should not be made only with the ex ^¬ planatory embodiments described herein. Of course, such ex ^¬ planatory embodiments are provided to make the disclosure more comprehensive and more complete and to fully describe the scope of the present invention to those skilled in the art .

The present invention will be explained in details hereinaf ^¬ ter referring to the accompanying drawings. Referring to Fig. 4, it illustrates a PCB 200 for the LED ac ^¬ cording to an embodiment of the present invention. The PCB 200 comprises an insulating base and a metal layer 205. Usu ^¬ ally the insulating base can consist of the substrate 201 and the insulating layer 203 located above the substrate 201. The metal layer 205 is preferably copper layer which is lo ^¬ cated above the insulating layer 201 and comprises a pattern for electrical connection with the LED. The PCB 200 further comprises a reflecting layer 207 which is located on the metal layer to reflect light from the LED. Particularly, the reflecting layer is formed of a non-photosensitive reflecting material having a reflectivity greater than 80%. As shown in Fig. 4, the pattern of the reflecting layer is substantially formed to correspond to that of the metal layer, so that it is suitable for mounting the LED during disposing the LED. Through the reflecting layer 207, compared with the known technical solution shown in Fig. 1, as a high-reflectivity reflecting layer is used, the optical efficiency is improved. Also, for the PCB 200, compared with the known solution of using the adhesive and the screw for fixing, as the adhesive and the screws are avoided, its structure is simple and the assembling is convenient, and the reliability is fine during use .

According to a preferable embodiment of the present inven ^¬ tion, the reflecting layer can be formed of a polyester material. Particularly, it can be formed of Interpon 600 powder, and particularly formed of Interpon 600 powder purchased from AkzoNobel, which is a high-reflectivity polyester material within a visible light range and has a reflectivity of at least about 93% when its thickness is about βθμιη. Meanwhile, the material has fine insulating property and can bear an al ^¬ ternating current of 4000V when its thickness is βθμιη.

During forming the PCB, the reflecting layer can be formed by sputtering the powder on the metal layer, which will be detailed hereinafter. Furthermore, compared with the known so ^¬ lution of conducting fixing using the screws and the adhe- sive, the reflecting layer formed by sputtering the powder has a simple structure and can be assembled conveniently and is reliable during use.

The method for making the PCB for the LED according to the first embodiment of the present invention will be described hereinafter referring to Figs. 5a-5d.

First, referring to Fig. 5a, the substrate 201 and the insu ^¬ lating layer 203 are prepared, the metal layer 205 which can be copper layer is formed on the insulating layer 203, and the metal layer is patterned for future electrical connection with the LED.

Furthermore, referring to Fig. 5b, the LED mock-up 209 is provided on the metal layer 205, wherein, the LED mock-up 209 and the actual LED have the same size, and the LED mock-up 209 is formed to have a pattern which is substantially oppo- site to that of the metal layer 205, that is, the metal layer 205 is exposed. Specifically, the LED mock-up 209 is adhered to the metal layer 205 with an adhesive material to be used as the blocking layer. Furthermore, as shown in Fig. 5c, the reflecting material is sputtered on the metal layer 205 and the LED mock-up 209. Specifically, a high-reflectivity polyester material can be sputtered. More specifically, the Interpon 600 powder can be sputtered and is made to have a thickness of βθμιη, so that its reflectivity can reach at least 93%.

Furthermore, preferably, the PCB is heated in a heating cham ^¬ ber or on a heating plate, so that the sputtered reflecting powder is cured.

Still furthermore, as shown in Fig. 5d, the LED mock-up 209 and a part of the sputtered reflecting material on the LED mock-up 209, 211 are removed, thereby forming the reflecting layer 207 for reflecting the light from the LED. Preferably, the removing step is conducted when the sputtered reflecting powder is being cured. Specifically, when the PCB is heated in a heating chamber or on a heating plate so as to cure the sputtered reflecting powder, the adhesive material adhering the LED mock-up 209 is heated and then melted, so that the LED mock-up 209 falls off the PCB and is thus removed.

In the Figs. 5a-5d, the LED mock-up 209 is used as the block- ing layer in a simple way, so that the sputtered reflecting powder is prevented from entering the position for mounting the LED. However, the present invention is not limited to this. For example, the blocking layer can be formed in various manners, for example, formed with the method shown in Figs. 6a-6f. The method for making the PCB for the LED according to the second embodiment of the present invention will be described hereinafter referring to Figs. 6a-6f.

First, referring to Fig. 6a, the substrate 201 and the insu- lating layer 203 are prepared, the metal layer 205 which can be copper layer is formed on the insulating layer 203, and the metal layer is patterned for future electrical connection with the LED.

Furthermore, referring to Fig. 6b, the photoresist 211 is coated on the metal layer 205, and the photosenstive material will form the blocking layer in subsequent steps.

The blocking layer can be formed with many methods, for example, Figs. 6ca and 6cb illustrate two methods for forming the blocking layer through the photoresist 211. As shown in Fig. 6ca, the photoresist 211 is a negative one. In this situation, a mask 213 is provided on the photoresist 211, wherein, the mask 213 comprises a pattern which is the same with that of the metal layer. Then UV light is used to etch the photoresist, so that a pattern which is substan- tially opposite to that of the metal layer 205 is formed on the negative photoresist in the presence of the mask 213.

Or, alternatively, as shown in Fig. 6cb, the photoresist 211 is a positive one. In this situation, a mask 213 is provided on the photoresist 211, wherein, the mask 213 comprises a pattern which is substantially opposite to that of the metal layer. Then UV light is used to etch the photoresist, so that a pattern which is substantially opposite to that of the metal layer 205 is formed on the positive photoresist in the presence of the mask 213. The shape of the blocking layer formed in Figs. 6ca and 6cb is shown in Fig. 6d.

Furthermore, as shown in Fig. 6e, the reflecting material is sputtered on the blocking layer formed of the metal layer 205 and the photoresist 211. Specifically, a high-reflectivity polyester material can be sputtered. More specifically, the Interpon 600 powder can be sputtered and is made to have a thickness of βθμιη, so that its reflectivity can reach at least 93%. Furthermore, preferably, the PCB is heated in a heating cham ^¬ ber or on a heating plate, so that the sputtered reflecting powder is cured.

Still furthermore, as shown in Fig. 6f, the blocking layer formed of the photoresist can be removed with methods such as a chemical solvent, and then a part of the sputtered reflect ^¬ ing material on the LED photoresist 211 is removed, thereby forming the reflecting layer 207 reflecting the light from the LED.

In the present invention, a high-reflectivity material is used to form the reflecting layer, so that absorption of the light is minimized, and also, automatic production and mass- production are made easy due to the simplified structure, the additional devices (for example, stamping machine) in the prior art are not needed any more, and the assembling is sim- pie and reliable, as the final assembly does not need any screw and/or adhesive. In addition, the PCB according to the present invention has a greatly lowered material cost and producing cost. The above are merely preferred embodiments of the present in ^¬ vention and are not intended to limit the present invention. For the person skilled in the art, the present invention may have various alterations and changes. Any alterations, equi- valent substitutions, improvements, within the spirit and principle of the present utility model, should be covered in the scope of protection of the present invention.