Light emitting diode load board and manufacturing process thereof

A light emitting diode load board includes a substrate, a first dielectric layer, a second dielectric layer and a first conductive pad and a second conductive pad. The second dielectric layer includes a first structure part, a second structure part and a third structure part. The first dielectric layer is disposed on the substrate. The first structure part is disposed on the first dielectric layer and has a first sidewall. The second structure part is disposed on the first structure part and has a second sidewall. The third structure part is disposed on the second structure part and has N sidewalls. The second sidewall is more prominent than the first sidewall. The first sidewall, the second sidewall and the N sidewalls define the first etched part, and the part of the first dielectric layer is exposed from the first etched part. The first conductive pad is disposed in the first etched part. The second conductive is disposed on the second dielectric layer, covers part of the second dielectric and exposes the open of the first etched part.

BACKGROUND

Technical Field

The disclosure relates to a light emitting diode (LED) load board and a manufacturing method thereof, more particularly to a LED load board with an alignment structure and a manufacturing method thereof.

Related Art

Generally, when LEDs are powered to emit light, the supplied power is partly used to emit light and partly converted into thermal energy. In practice, the luminous efficiency of a LED rapidly drops under the influence of a high temperature environment, so the LED wastes more power and also produces more heat, resulting in the increase of temperature. The LED then falls into a vicious spiral. Therefore, it would be better to load LEDs on a load board with a better thermal conductivity in order to avoid wasting power and a shorter lifespan.

Additionally, for the ease of manufacturing, modern LED load boards use a simple laminated structure without any design on the junction between the load board and LEDs, and such a concern about the junction between the load board and LEDs is left to a later assembling process. This will bring in a difficulty in the assembling process and also decrease the yield rate of the manufacturing of load boards.

SUMMARY

For this, the disclosure promotes a LED load board and a manufacturing method thereof in order to enhance the thermal conductivity of the LED load board during the manufacturing of the LED load board and meanwhile solve the problems in the aligning connection between LEDs and the load board.

According to one or more embodiments, the disclosure provides a LED load board. The LED load board includes a substrate, a first dielectric layer, a second dielectric layer, a first conductive pad and a second conductive pad. The second dielectric layer includes a first structure portion, a second structure portion and a third structure portion. The first dielectric layer is formed on the substrate. The first structure portion is formed on the first dielectric layer and includes a first sidewall. The second structure portion is formed on the first structure portion and includes a second sidewall. The second sidewall is more prominent than/protrudes from the first sidewall. Third structure portion is formed on the second structure portion and includes N pieces of sidewall. Even one of the N pieces of sidewall is more prominent than/protrudes from odd one of the N pieces of sidewall. The first sidewall, the second sidewall and the N pieces of sidewall constitute a first etched portion, which exposes a fraction of the first dielectric layer. The first conductive pad is formed in the first etched portion. The second conductive pad is formed on the second dielectric layer, covers a fraction of the second dielectric layer, and exposes openings of the first etched portion.

In an embodiment, the second structure portion and the first dielectric layer have a gap portion therebetween. The width of the gap portion is substantially equal to the thickness of the first structure portion. In an embodiment, the first conductive pad does not contact the first and second sidewalls. In an embodiment, the first structure portion is made of polysilicon, and the first structure portion and the second structure portion have a difference in material. In an embodiment, the insulation layer covers the openings of the first etched portion and exposes a fraction of the second conductive pad. In an embodiment, the LED load board further includes a conductive pillar, which has one terminal connecting to the second conductive pad, and has another terminal sticking out from the insulation layer.

Also, the disclosure provides a manufacturing method of a LED load board in one or more embodiments. In an embodiment, the manufacturing method includes the following steps. Form a first dielectric layer on a substrate, and form a second dielectric layer on the first dielectric layer. The second dielectric layer includes a first structure portion, a second structure portion, and an Nth structure portion. The first structure portion is between the second structure portion and the first dielectric layer. The first structure portion includes a first sidewall, the second structure portion includes a second sidewall, and the Nth structure portion includes an Nth sidewall. The second sidewall is more prominent than/protrudes from the first sidewall. The first, second and Nth sidewalls constitute a first etched portion, which exposes a fraction of the first dielectric layer. Then, form a first conductive pad on the first dielectric layer, and form a second conductive pad on either the second structure portion or the Nth structure portion.

In an embodiment, the manufacturing method may further include the following steps. Form an insulation layer on the second conductive pad. The insulation layer may cover the openings of the first etched portion and expose a fraction of the second conductive pad. Form a conductive pillar on the second conductive pad. One terminal of the conductive pillar contacts the second conductive pad, and another terminal of the conductive pillar sticks out from insulation layer.

As described above, the structure of the LED load board in the disclosure may not only avoid the interconnection between different conductive layers but also has conductive pillars at the interface with LEDs, and these conductive pillars are helpful to the aligning connection with LEDs. Moreover, in an embodiment polysilicon is used to form one of the constitution layers of the LED load board, so the thermal conductivity of the LED load board may be enhanced. Therefore, the LED load board and the manufacturing method thereof may enhance the efficiency of aligning and connecting the LED load board to LEDs and also enhance the thermal conductivity of the LED load board.

DETAILED DESCRIPTION

Please refer toFIG. 1A.FIG. 1Ais a schematic structure diagram of a LED load board in an embodiment. A LED load board1includes a substrate11, a first dielectric layer12, a second dielectric layer13, a first conductive pad14and a second conductive pad15. The second dielectric layer13includes a first structure portion131, a second structure portion132and a third structure portion135. The first structure portion131includes a first sidewall1311, the second structure portion132includes a second sidewall1321, and the third structure portion135is constructed by multiple layers and thus, includes multiple third sidewalls, such as third sidewalls1351a˜1351d. In practice, the third structure portion135has no limitation on the number of sidewalls. The first sidewall1311, the second sidewall1321and the third sidewalls1351a˜1351dconstitute a first etched portion133.

The first dielectric layer12is on the substrate11. The first structure portion131of the second dielectric layer13is on the first dielectric layer12, and the second structure portion132of the second dielectric layer13is on the first structure portion131. The first conductive pad14is at the bottom of the first etched portion133. The second conductive pad15is on the third structure portion135, covers a fraction of the second dielectric layer13, and exposes the openings of the first etched portion133.

Instances of the material of the substrate11include silicon. Instances of the first dielectric layer12include a film which is formed on the surface of the substrate11by heating the surface of the substrate11in the heating process.

The materials of the first structure portion131and the second structure portion132of the second dielectric layer13are the same in an embodiment or are different in another embodiment. That is, the second dielectric layer13is formed integrally or formed by piling multiple layers. Moreover, the second sidewall1321of the second structure portion132is more prominent than the first sidewall1311of the first structure portion131, so the first etched portion133constituted by the first sidewall1311and the second sidewall1321has an undercut structure. Specifically, the second structure portion132and the first dielectric layer12have a gap portion1331therebetween, and the gap portion1331is a fraction of the first etched portion133. The second structure portion132is separated from a fraction of the first dielectric layer12by the gap portion1331and faces the fraction of the first dielectric layer12. The width of the gap portion1331is substantially equal to the thickness of the first structure portion131.

In an embodiment, the first structure portion131, the second structure portion132and the third structure portion135are oxide materials. In another embodiment, the first structure portion131and the odd layers of the third structure portion135are made of, for example, but not limited to, polysilicon, and the second structure portion132and the even layers of the third structure portion135are made of, for example, but not limited to, oxide or dielectric materials. In this embodiment, the thermal conductivity and etching rate of the first structure portion131are higher than those of the second structure portion132, and the thermal conductivity and etching rate of odd layers of the third structure portion135are higher than those of even layers of the third structure portion135.

The material of the first conductive pad14is the same as that of the second conductive pad15. In this embodiment, the first conductive pad14and the second conductive pad15are made of, for example, but not limited to, sliver. More particularly, the first conductive pad14and the second conductive pad15are formed by, for example, but not limited to, coating sliver on the LED load board1in a sputtering process or evaporation deposition process. Because of the structure relief of the LED load board1as well as the undercut structure, a fraction of the sliver film will constitute the first conductive pad14on the first dielectric layer12as another fraction of the sliver film will constitute the second conductive pad15on the third structure portion135. Moreover, the first conductive pad14does not contact the second conductive pad15, and the first conductive pad14does not contact the first structure portion131.

Please refer toFIG. 1Bto describe another embodiment of the second conductive pad15.FIG. 1Bis a schematic structure diagram of the LED load board inFIG. 1Ain another embodiment. Different from the structure inFIG. 1A, a second conductive pad15′ inFIG. 1Bsticks out from a third sidewall1351d′ of a third structure portion135′, and the second conductive pad15′ extends toward a substrate11′ and covers third sidewalls1351a′˜1351d′ and at least part of a second sidewall1321′. In this embodiment, the second conductive pad15′ does not contact a first conductive pad14′. The structure of the LED load board1′ is exemplary and will not be restricted to that the second conductive pad15′ covers all the third sidewalls1351a′˜1351d′, on condition that the second conductive pad15′ does not contact the first conductive pad14′.

Please refer toFIG. 1C.FIG. 1Cis a schematic structure diagram of the LED load board inFIG. 1Ain yet another embodiment. The material of a second structure portion132″ is mainly made of polysilicon, and the material of the second structure portion132″ is different from the material of a first structure portion131″. A protruding part of a second sidewall1321″ and the periphery thereof are subject to a high-temperature oxidization to constitute a polysilicon oxide insulation layer1353″. In other words, the polysilicon oxide insulation layer1353″ externally covers a primary polysilicon material, so the conductivity between a first conductive pad14″ and a second conductive pad15″ decreases.

In view of the structure of the LED load board1, the disclosure also provides a manufacturing method of LED load boards. Please refer toFIGS. 1A˜1C andFIG. 2to illustrate the manufacturing method.FIG. 2is a flow chart of a manufacturing method of the LED load board in an embodiment. The manufacturing method includes the following steps. First, in step S201, form the first dielectric layer12on the substrate11. Then, in step S203, form the second dielectric layer13on the first dielectric layer12. The second dielectric layer13includes the first structure portion131, the second structure portion132and the third structure portion135. Next, in step S205, form the first conductive pad14on the first dielectric layer12and form the second conductive pad15on the second structure portion132. The detailed structure of the LED load board1can be referred to the foregoing description and thus, will not be repeated hereinafter. In view of the LED load board1″ inFIG. 1C, the protruding part of the first sidewall is further subject to a high-temperature heating process to form the aforementioned oxide insulation layer in step S203.

In step S203, an integral second dielectric layer is formed by the following manufacturing process, and the second dielectric layer has an undercut structure. Please refer toFIG. 3A˜FIG. 3E.FIG. 3A˜FIG. 3Fare schematic diagrams illustrating a process of manufacturing the LED load board1inFIG. 1Ain an embodiment.

In the step shown inFIG. 3A, a first dielectric layer32is formed on a substrate31, and a deposition layer334is formed on the first dielectric layer32. Then, a first photoresist layer91is formed on the deposition layer334, and the first photoresist layer91has a first pattern. The substrate31is, for example, but not limited to, a silicon substrate. The first dielectric layer32is, for example, but not limited to, a film formed on the surface of the silicon substrate by heating the surface of the silicon substrate. The deposition layer334is, for example, but not limited to, boro-phospho-silicate glass (BPSG) formed by depositing a molecule material on the first dielectric layer32. The first photoresist layer91is, for example, but not limited to, a positive photoresist layer, and in another embodiment, the first photoresist layer91is a negative photoresist layer and has a relevant pattern.

In the step shown inFIG. 3B, the transition structure formed in the step shown inFIG. 3Ais subject to a photolithography process to remove a fraction of the deposition layer334. After that, remove the first photoresist layer91to let the rest of the deposition layer334be exposed.

In the step shown inFIG. 3C, a first structure portion331and a second structure portion332are formed on the transition structure produced in the step with respect toFIG. 3B. The deposition layer334and the first dielectric layer32are covered with the first structure portion331and the second structure portion332, and the first structure portion331and the second structure portion332fill the one or more spaces (referred to as accommodation space) in the deposition layer334.

Subsequently, in the step shown inFIG. 3D, the transition structure of a third structure portion335is formed again on the second structure portion332by the methods with respect toFIGS. 3B and 3C. The details of the transition structure of the third structure portion335can be referred to the aforementioned description and thus, will not be repeated hereinafter. Herein, a second dielectric layer33is being shaped on the first dielectric layer32. Then, a second photoresist layer92is formed on this second dielectric layer33, and the second photoresist layer92has a second pattern. In this embodiment, the second dielectric layer33is made of, for example, but not limited to an oxide material, and the second photoresist layer92is, for example, but not limited to a positive photoresist layer.

In the step shown inFIG. 3E, the transition structure produced in the step with respect toFIG. 3Dis subject to another photolithography process to remove a fraction of the second dielectric layer33and a fraction of the reset of the deposition layer334. After that, the second photoresist layer92is removed. Herein, the second dielectric layer33substantially becomes a structure constituted by stacking multiple T-shaped layers, and the rest of the deposition layer334is in the spaces between the head parts of these T-shaped layers and is also in the spaces between the T-shaped layer and the first dielectric layer32.

In the step shown inFIG. 3F, the rest of the deposition layer334is removed, so the second dielectric layer33herein has an undercut structure as described above.

On the other hand, in addition to carrying out the production of the second dielectric layer by the manufacturing process with respect toFIGS. 3A˜3F, the second dielectric layer, which has a multi-player structure and an undercut structure, in step S203can be produced by the following manufacturing process with respect toFIG. 4A˜FIG. 4E.FIG. 4A˜FIG. 4Eare schematic diagrams illustrating a process of manufacturing the LED load board inFIG. 1Ain another embodiment.

In the step shown inFIG. 4A, a first dielectric layer42is formed on a substrate41. In the step shown inFIG. 4B, a first structure portion431is formed on the first dielectric layer42, then after a second structure portion432is formed on the first structure portion431, a third structure portion435is formed on the second structure portion432. Herein, a second dielectric layer43is formed in rough. In this embodiment, the first structure portion431and odd layers of the third structure portion435are made of, for example, but not limited to, polysilicon, and the second structure portion432and the first structure portion431are made of different materials. Also, the material of odd layers of the third structure portion435is different from the material of even layers of the third structure portion435. Therefore, the etching rate for the first structure portion431is different from the etching rate for the second structure portion432, and the etching rate for the odd layers of the third structure portion435is different from the etching rate of the even layers of the third structure portion435. In this embodiment, the etching rate for the first structure portion431is higher than the etching rate for the second structure portion432, and the etching rate for the odd layers of the third structure portion435is higher than the etching rate for the even layers of the third structure portion435.

Then, in the step shown inFIG. 4C, a third photoresist layer93is formed on the third structure portion435, and the third photoresist layer93has a third pattern. In the step shown inFIG. 4D, the transition structure produced in the step with respect toFIG. 4Cis subject to a wet etching process to remove a fraction of the first structure portion431, a fraction of the second structure portion432, and a fraction of the third structure portion435. Since the etching rate for the first structure portion431is relatively high, the removed part of the first structure portion431is more than that of the second structure portion432, thereby forming an undercut structure. Moreover, the odd layers of the third structure portion435has a relatively high etching rate as compared to the even layers of the third structure portion435, so the sidewalls of the even layers of the third structure portion435are more prominent than the sidewalls of the odd layers of the third structure portion435. Subsequently, the third photoresist layer93is removed in the step shown inFIG. 4E.

Note that the embodiments with respect toFIG. 3A˜FIG. 4Eemploy rectangles to represent the construction layers of the load board for the concise description of the disclosure. A person skilled in the art should understand that the disclosure has no limitation in the aspect ratio or angles of the rectangle.

Hereinafter, the structure and applications of the LED load board in the disclosure will be described in more detail, where in view of the foregoing description, the first and second structure portions of the second dielectric layer are integrated or are formed by piling multiple layers using a polysilicon material and thus, will not be repeated.

Please refer toFIG. 5A.FIG. 5Ais a schematic structure diagram of a LED load board in another embodiment. As compared to the embodiment inFIG. 1A, a LED load board5inFIG. 5Afurther includes an insulation layer57and conductive pillars58. The insulation layer57covers openings of a first etched portion533and exposes a fraction of a second conductive pad55. In another embodiment, the insulation layer57further fills the spaces in the first etched portion533. The conductive pillar58is on the second conductive pad55, one terminal of the conductive pillar58contacts the second conductive pad55, and another terminal of the conductive pillar58sticks out from the insulation layer57.

InFIG. 5A, a LED component2is further disposed. The LED component2has connecting points21. The conductive pillars58of the LED load board5are connected to the connecting points21in pairs. In other words, when the LED component2is disposed on the LED load board5, the two terminals of the conductive pillar58are electrically connected to the second conductive pad55and the connecting point21, respectively. In the drawing, the two connecting points21of the LED component2are electrically connected to the two second conductive pads55, respectively, and the two second conductive pads55are not connected. In an embodiment, the two separated second conductive pads55in use are set at two different voltage potentials respectively, so the LED component2will sense the two different voltage potentials through the two connecting points21and will according to the difference between the two voltage potentials, decide whether to emit light. Moreover, the conductive pillars58are further aligned and connected with the LED component2, so as to increase the assembling quality.

Please refer toFIG. 5B.FIG. 5Bis a schematic structure diagram of the LED load board inFIG. 5Ain another embodiment. As compared to the embodiment with respect toFIG. 5A, a LED load board5′ inFIG. 5Bfurther includes a third dielectric layer56′. A first terminal of the third dielectric layer56′ contacts a first dielectric layer52′, a second terminal of the third dielectric layer56′ contacts a second structure portion532′, and a third terminal of the third dielectric layer56′ contacts a first sidewall5311′. In the LED load board5′ inFIG. 5B, the third dielectric layer56′ is further disposed between a first conductive pad54′ and a first structure portion531′ to more efficiently prevent the first conductive pad54′ from contacting the first structure portion531′ because of the diffusion of first conductive pad54′, as compared to the previous embodiments in which air is used as an insulation medium separating the first conductive pad from the first structure portion. The third dielectric layer56′ is made of, for example, but not limited to, an oxide material.

Please refer toFIG. 5C.FIG. 5Cis a schematic structure diagram of the LED load board inFIG. 5Ain yet another embodiment. As compared to the embodiment with respect toFIG. 1A, a LED load board5″ inFIG. 5Cfurther includes an insulation layer57″ and conductive pillars58″. The openings of the first etched portion533″ are covered by the insulation layer57″, and the insulation layer57″ exposes a fraction of a second conductive pad55_2. In another embodiment, the insulation layer57″ further fills the spaces in the first etched portion533″. The conductive pillar58″ is formed on the second conductive pad55_2. That is, when the second conductive pad55_1is used for strengthening the reflectivity merely. One terminal of the conductive pillar58″ contacts a fraction of the second conductive pad55_2, which is insulated, and the other terminal of the conductive pillar58″ sticks out from the insulation layer57″.

Furthermore, a LED component2is disposed as shown inFIG. 5C. The LED component2includes connecting points21. The conductive pillars58″ of the LED load board5″ are aligned and connected with the connecting points21, respectively. That is, when the LED component2is disposed on the LED load board5″, the two terminals of the conductive pillar58″ are electrically connected to the second conductive pad55_2and the related connecting point21, respectively. In the drawing, the two connecting points21of the LED component2are electrically connected to the two separated second conductive pads55_2, respectively. In an embodiment, the two separated second conductive pads55_2are set at two different voltage potentials in use respectively; the LED component2will sense two different voltage potentials through the two connecting points21, so as to emit light according to the difference between the two different voltage potentials. Since the conductive pillar58″ can be aligned and connected with the LED component2, the assembling quality may be better.

Please refer toFIG. 6.FIG. 6is a schematic structure diagram of a LED load board in yet another embodiment. In this embodiment, a second sidewall6321is more prominent than an edge of an insulation layer67, so the insulation layer67exposes a fraction of a second conductive pad65, which is around openings of a first etched portion633. As shown in the drawing, a LED component2is disposed on the insulation layer67, and the LED component2is electrically connected to the fraction of the second conductive pad65, which is exposed by the insulation layer67, through connecting points21directly. This is different from the previous embodiments, in which the LED component2is electrically connected to the second conductive pads through the conductive pillars indirectly.

Please refer toFIG. 7.FIG. 7is a schematic structure diagram of a LED load board in yet another embodiment. In a LED load board6shown inFIG. 7, an insulation layer77covers a second conductive pad75, a second sidewall7321, a first sidewall7311, and multiple sidewalls of a third structure portion735. The insulation layer77exposes at least a fraction of a first conductive pad74. Conductive pillars78are formed in the first conductive pad74. One terminal of the conductive pillar78is electrically connected to the first conductive pad74, and the other terminal of the conductive pillar78sticks out from the insulation layer77. In other words, the conductive pillar78is separated from the second conductive pad75by the insulation layer77and is electrically connected to only the first conductive pad74. Also, the conductive pillars78stick out from the insulation layer77and thus, can be aligned and connected with the connecting points21of the LED component2.

As set forth above, the disclosure provides the above LED load board and the above manufacturing method thereof. The LED load board not only has an undercut structure, which is used to avoid the interconnection between different conductive layers, but also has multiple conductive pillars which are formed at the interface between the LED load board and the LEDs and are aligned and connected with the LEDs. Moreover, in the LED load board, one of the dielectric layers is made in part of polysilicon so that the thermal conductivity of the LED load board may increase. Therefore, the LED load board and the manufacturing method thereof in the disclosure may efficiently solve the problems caused by neglecting the aligning connection between the load board and LEDs in the art, and may enhance the thermal conductivity of the LED load board.