Patent Application
20140362590
Various embodiments relate to an electronic module, a lighting device and a manufacturing method of the electronic module.
Currently, lighting devices have found increasingly wide application in daily life. Most of the electronic modules of these lighting devices have a plastic potting material generally in the form of external housing. Such a potting material ensures that the electronic module meets the dustproof and waterproof requirements in industrial use and prevents the damage of a circuit board and electronic components mounted thereon, especially a LED, during a transportation or installation process.
As shown in
Hence, various embodiments provide a novel electronic module. Such an electronic module which is simple in structure and low in manufacturing cost. Due to the improvement of the potting material of the module, the electronic module according to the present disclosure has lower thermal resistance and good stability.
An electronic module to be mounted on a mounting surface is provided according to the present disclosure, including a circuit board provided with a heat source, wherein a thermal via is formed through the circuit board and is in thermal contact with the heat source; and a potting material packaging the circuit board at least at the other side opposite to one side of heat source, wherein the potting material has a recess formed in at least part of an area corresponding to the thermal via at the other side of the circuit board and a thermal conductive material, which is thermal-conductively connected to the mounting surface, is filled in the recess.
The design idea of the present disclosure lies in breaking through the barrier of the traditional package design of the electronic module. Herein, the potting material exists in the form of potting housing. In order for the heat in the thermal via provided in the circuit board to be better dissipated to its outside, the housing section (hereinafter short for “bottom-surface housing section”) corresponding to the area of thermal via on the bottom surface of the packaged circuit board shall be designed to be as thin as possible. In the most preferred case, the bottom-surface housing section may be removed, such that the thermal via may directly reach the thermal conductive material provided for replacing the bottom-surface housing section and the corresponding area of the bottom surface of the circuit board may be in direct contact with the thermal conductive material rather than enclosed completely and airtightly by the potting housing. Thus, based on such a specific structure as a potting housing and the properties of insulation and thermal conduction of the thermal conductive material, the thermal resistance of the whole electronic module can be advantageously reduced, thereby allowing the electronic module to obtain good stability in an operating state.
In various embodiments, the recess includes at least an area corresponding to the thermal via in position and size, whereby the heat generated by the heat source in an operating state may be directly dissipated to the outside of the circuit board.
In various embodiments, the area of the recess covers up to 90% of that of the other side, viz. the back side of the circuit board. The recess located at the other side of the circuit board is set as wide as possible for providing sufficient heat dissipation pathways. As long as the potting material at the side surface of the electronic module may extend for enclosing the edge of the other side of the circuit board, viz. only covering 10% of the other side of the circuit board from the edge to the inside, better heat dissipation design may be achieved.
In various embodiments, the recess is in communication with the thermal via, such that the heat flow guided by the thermal via may be directly transferred to the thermal conductive material.
In various embodiments, a thin protective layer is provided between the recess and the circuit board. Said thin protective layer may be either part of the potting material or made of other materials with low thermal resistances. The thickness of the thin layer is, for example, less than 0.2 mm. Thus, the high airtightness of the whole electronic module can be ensured while realizing the minimum thermal resistance so as to meet the waterproof and dustproof requirements in industry.
In various embodiments, the thermal conductive material is designed as a step, including a first portion received by the recess, an enlarged second portion extending beyond the recess which covers the potting material. Therefore, the design achieves the effect of dual-layer thermal conduction and improves the airtightness of the electronic module. The material of the first portion and that of the second portion may be either the same or different.
In various embodiments, the thermal conductive material only fills up the recess or the thermal conductive material is filled to extend beyond the recess with same size as that in the recess, and the extended portion of the thermal conductive material is used to be mounted to the mounting surface. In the case where the thermal conductive material only fills up the recess, the thermal conductive material is level with the recess, such that the bottom surface of the electronic module may be adhered evenly to the mounting surface. In the latter case, only the end surface of the thermal conductive material extended beyond the recess may be used as a contact surface to be adhered to the mounting surface, which makes a gap present between the potting material and the mounting surface.
In various embodiments, a front side and a back side of the thermal conductive material are each coated with an adhesive layer for adhering respectively to the bottom surface of the recess and the mounting surface. Coating the double surfaces of the thermal conductive material with the adhesive layer may, on one hand, fix firmly the thermal conductive material in the recess, and on the other hand, make the whole of the electronic module adhere to different mounting surfaces.
In various embodiments, the thermal conductive material is made of an electrical insulating material.
In various embodiments, the thermal conductive material is a filler based on any one of resin, silica gel, and plastic, containing one type of particles or a plurality of particles selected from silicon carbide, aluminum oxide, magnesium oxide, and aluminum nitride. That is to say, the thermal conductive material is a gap filler containing particles with high thermal conductivity. The basic material may be resin, silica gel, or plastic. The particles with high thermal conductivity contained therein may be particles (nanosized particles) of silicon carbide, aluminum oxide, magnesium oxide, or aluminum nitride. Other materials also having properties of high thermal conductivity and electrical insulation may also be considered for manufacturing a thermal conductive material.
In addition, various embodiments provide to a lighting device, including the above electronic module, wherein the heat source is an LED. Certainly, a light engine or the like may be considered to replace the circuit board provided with the LED to form the lighting device.
Further, various embodiment provide a method for manufacturing the above electronic module, including the following steps:
(a) providing a circuit board provided with a heat source, wherein a thermal via is formed through the circuit board and is in thermal contact with the heat source;
(b) putting the circuit board into one mold, wherein the mold is designed to be at least in contact with at least part of the bottom surface of the circuit board provided with the thermal via and a gap is formed between the mold and the rest of the bottom surface of the circuit board;
(c) injecting a potting material to form a recess on at least part of the contacted bottom surface.
Various embodiments further includes step (d), after the mold is removed, in step (d), a thin layer is formed via injection moulding on the recess. Said thin layer may be either part of the potting material or made of other materials. The thickness of the thin layer is less than 0.2 mm.
In various embodiments, there is also provided a method for manufacturing the above electronic module, including the following steps:
(a) providing a circuit board provided with a heat source, wherein a thermal via is formed through the circuit board and is in thermal contact with the heat source;
(b) putting the circuit board into one mold, wherein the mold is designed to form a first gap between the mold and the part of the bottom surface of the circuit board and to form a second gap between the mold and the rest of the bottom surface of the circuit board, the first gap being smaller than the second gap;
(c) injecting a potting material to form a recess at the position corresponding to the first gap.
Thus obtained is either a through recess the bottom surface of which is the bottom surface of the circuit board or a recess the bottom surface of which is a thin film also made of the potting material. The thickness of the thin film is less than 0.2 mm.
Various embodiments further includes step (e) following step (d), in the step (e): filling a solid thermal conductive material in the recess or filling a liquid thermal conductive material in the recess and solidifying the thermal conductive material via standing or heating.
Preferably, in step (e), the thermal conductive material has adhesive layers at two sides facing and away from the circuit board and only fills up the area of the recess. The electronic module thus manufactured may achieve IP65 level.
In various embodiments, there is further included step (f): covering the outside of the filled potting material at the back side of the circuit board with another layer of thermal conductive material. The electronic module thus manufactured may achieve IP66-67 level.
Various embodiments further includes step (g) following step (d): using the liquid thermal conductive material to fill up the recess and to solidify, and further includes step (h) following step (g): adhering a tape to the outside of the filled potting material at the back side of the circuit board. The electronic module thus manufactured may achieve IP66-67 level.
Preferably, the thermal conductive material is made of thermal interface material, and the potting material is rigid plastic.
In the drawings, like reference characters generally refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the disclosed embodiments. In the following description, various embodiments described with reference to the following drawings, in which:
The following detailed description refers to the accompanying drawing that show, by way of illustration, specific details and embodiments in which the disclosure may be practiced.
The difference as compared with
The thermal resistance of the electronic module according to the present disclosure may be calculated by the formula: thermal resistance=thickness/(area*thermal conductivity). Without affecting the packaging, the thermal resistance of the potting material 4 may be reduced satisfactorily by reducing the thickness of the potting material 4 on the bottom surface and increasing the corresponding area of the recess 8. The area of the recess 8 is preferably 90% of that of the whole electronic module. The recess 8 located at the back side of the circuit board 2 is set to be as large as possible so as to provide sufficient heat dissipation pathways. As long as the potting material 4 at the side surface of the electronic module may extend for enclosing the edge of the back side of the circuit board 2, viz. for example, only covering 10% of the back side of the circuit board 2 from the edge to the inside, the best heat dissipation design may be achieved.
In order to ensure the packaging effect and further improve thermal performance, a thermal conductive material 5 made of thermal interface material (TIM) may be filled in the recess 8. The thermal conductive material 5 with an electrical insulation property is, for example, a filler based on silica gel. The thickness of the thermal conductive material 5 shall be equal to or larger than the depth of the recess 8. In order to make the thermal conductive material 5 in firm thermal contact with the bottom surface of the recess 8, both the front side and the back side thereof may be coated with adhesive layers for adhering respectively to the bottom surface of the recess 8 and the mounting surface 6. Another possible case is: adhering a double-side-adhesive second layer of thermal interface material (not shown) to a side where the thermal conductive material 5 faces the mounting surface 6. The area of the second portion of thermal interface material shall be larger than that of the thermal conductive material 5 and enlarged second portion extending beyond the recess 8 which covers the potting material 4 for forming a step thermal conductive structure, thereby ensuring good airtight and thermal conductive effects.
The thermal conductive material 5 is a filler containing particles with high thermal conductivity. The basic material may be resin, silica gel, or plastic. The particles with high thermal conductivity contained therein may be particles (nanosized particles) of silicon carbide, aluminum oxide, magnesium oxide, or aluminum nitride. Other materials also having properties of high thermal conductivity and electrical insulation may also be considered for manufacturing a thermal conductive material.
As shown in
It can be seen from
According to another manufacturing method, a certain space is preserved at the recess 8 when designing the mold, viz. the mold is designed to form a first gap between the mold and part of the bottom surface of the circuit board 2 and to form a second gap between the mold and the rest of the bottom surface of the circuit board 2, the first gap being smaller than the second gap. Thus, the protective thin film 9 is formed on the recess 8 after the removal of the mold. The protective thin film 9 constitutes the bottom surface of the recess 8. As shown in
In
Preferably, the thermal interface material for manufacturing the thermal conductive material is an electrical insulating material. Particularly preferably, the thermal conductive material 5 is a filler based on silica gel. Organic silicone resin or silica gel doped with silica particles or ceramic particles may be selected for manufacturing the thermal conductive material according to the present disclosure. Other materials also having properties of high thermal conductivity and electrical insulation may also be considered for manufacturing the thermal conductive material.
While the disclosed embodiments have been particularly shown and described with reference to specific embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the disclosed embodiments as defined by the appended claims. The scope of the disclosed embodiments is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201110235306.1 | Aug 2011 | CN | national |
The present application is a national stage entry according to 35 U.S.C. §371 of PCT application No.: PCT/EP2012/065712 filed on Aug. 10, 2012, which claims priority from Chinese application No.: 201110235306.1 filed on Aug. 16, 2011, and is incorporated herein by reference in its entirety.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2012/065712 | 8/10/2012 | WO | 00 | 4/23/2014 |
