A pad distribution structure for small pitch LEDs

Abstract

A kind of small pitch LED's pad distribution structure, it includes PCB board, LED lamp pearl, pad assembly.The LED lamp pearl includes lamp pearl main body, pin, the pad assembly includes first pad group, second pad group.The first pad assembly includes first upper pad, first lower pad.The distance between two first upper pad is less than the distance between two first lower pad.The bending position of pin middle section is formed with a bending part, and the bending part on the pin has a certain tin paste climbing area between pad edge.The width of the tin paste climbing area corresponding to two first upper pad is less than the width of the climbing area in conventional pad, so that the liquid tin paste capacity in the tin paste climbing area is far less than the capacity in conventional pad, even if the bending part has larger arc, a large amount of liquid tin paste does not climb up, so that the difference of wetting force between left and right pin and the tin paste is neutralized to the maximum.

Description

Technical Field

[0001] This utility model relates to the field of LED welding technology, and in particular to a pad distribution structure for small-pitch LEDs. Background Technology

[0002] With the rapid development of MiniLED technology, its application fields are becoming increasingly wide, and it is highly favored by the market due to its unique advantages such as high contrast, high brightness, and long lifespan. As the pixel pitch of MiniLEDs becomes smaller, the LED package size also decreases. This places extremely high demands on every step of the SMT reflow soldering process. Different manufacturers and different batches of LEDs will exhibit variations in shape; specifically, there are objective and unavoidable differences in the bending curvature of the LED's leads. During the reflow stage, as the solder paste melts and begins to wet the component's soldering surface, wetting force is generated. The leads with different bending curvatures have different contact areas with the liquid solder paste, resulting in differences in contact area and surface tension. Figure 4 As shown, due to the wetting force of liquid solder paste, it rises to the sidewalls of leads with larger bends, resulting in a larger contact area between the leads with larger bends and the liquid solder paste than the leads with smaller bends. This causes a difference in wetting speed between the two sides: one side wets quickly and with strong wetting force, while the other side wets slowly and with weak wetting force, leading to inconsistent wetting forces. When the wetting force acts on the leads, it generates torque. However, the large contact area due to the bend of the leads results in different surface tensions, amplifying the torque difference. When this torque difference exceeds the weight of the LED, the LED will tilt or lean towards the side with stronger wetting force. This tilt changes the light intensity distribution angle of the LED. For example, an LED tilted to the right is biased in a single direction, and this accumulates to create a "half-lit face" effect. The combination of tilts in multiple modules causes a "tile" phenomenon. Utility Model Content

[0003] In view of this, the present invention provides a pad distribution structure for small-pitch LEDs to solve the above problems.

[0004] A pad distribution structure for a small-pitch LED includes a PCB board, a plurality of LED chips arranged on the PCB board, and a plurality of pad assemblies disposed between the PCB board and the LED chips. Each LED chip includes a chip body and four pins disposed on one side of the chip body. Each pad assembly includes a first pad group and a second pad group disposed on one side of the first pad group. The first pad assembly includes two spaced-apart first upper pads and two spaced-apart first lower pads on one side of the first upper pads. The distance between the two first upper pads is less than the distance between the two first lower pads. A bend is formed at the midpoint of each pin, and a solder paste creep area exists between the bend and the edge of the pad. The width of the solder paste creep area corresponding to the two first upper pads is smaller than the width of the solder paste creep area in a conventional pad.

[0005] Furthermore, the four pins are located on both sides of the lamp bead body, and each side of the lamp bead body is provided with at least two pins.

[0006] Furthermore, the pin is L-shaped, and the opening direction is towards the lamp bead body.

[0007] Furthermore, the second pad group has a similar structure to the first pad group, and is arranged at intervals with the first pad group.

[0008] Furthermore, the second pad group includes two second upper pads spaced apart, and two second lower pads spaced apart on one side of the second upper pads.

[0009] Furthermore, the distance between the two second upper pads is greater than the distance between the two second lower pads.

[0010] Furthermore, the distance between the two second upper pads is equal to the distance between the two first lower pads, and the distance between the two second lower pads is equal to the distance between the two first upper pads. The second pad group is the inverted first pad group.

[0011] Compared to existing technologies, the solder pad distribution structure of the small-pitch LED provided by this utility model has a solder paste climbing area width corresponding to the two first upper solder pads that is smaller than the width of the climbing area in conventional solder pads. This results in a significantly smaller volume of liquid solder paste in the climbing area compared to that in conventional solder pads. Even with the large curvature of the bend, a large amount of liquid solder paste will not climb up, thus avoiding the influence of the curvature difference between the left and right sides of the bend and maximizing the neutralization of the difference in wetting force between the left and right leads and the solder paste. Conversely, the width of the solder paste climbing area corresponding to the two first lower solder pads is larger than the width of the climbing area in conventional solder pads. The large curvature of the bend causes a large amount of liquid solder paste to climb onto the sidewall of the lead at that location, resulting in a slight tilt of the LED towards the first lower solder pad on the right side. Furthermore, the second pad group is the inverted first pad group. The pad distribution in this way is arranged in a cross-row layout, which will cause the LED beads to be slightly tilted towards the upper right or lower right direction. This can further balance the overall bias of light intensity distribution caused by the tilt of the LED beads and reduce the impact of tilt in a single direction. Attached Figure Description

[0012] Figure 1 A schematic diagram of the pad distribution structure for small-pitch LEDs provided by this utility model.

[0013] Figure 2 for Figure 1 A schematic diagram of the pad distribution structure for small-pitch LEDs, with LED beads soldered onto the first upper pad.

[0014] Figure 3 for Figure 1 A schematic diagram of the pad distribution structure for small-pitch LEDs, with LED beads soldered onto the first lower pad.

[0015] Figure 4 This is a schematic diagram of the LED chip welding structure in the prior art. Detailed Implementation

[0016] The specific embodiments of this utility model are described in further detail below. It should be understood that the description of the embodiments of this utility model herein is not intended to limit the scope of protection of this utility model.

[0017] like Figure 1The diagram shows a schematic representation of the pad distribution structure for a small-pitch LED provided by this invention. The pad distribution structure includes a PCB board 10, a plurality of LED beads 20 arranged on the PCB board 10, and a plurality of pad assemblies 30 disposed between the PCB board 10 and the LED beads 20. It is conceivable that the pad distribution structure for the small-pitch LED also includes other functional modules, such as a hot air gun for melting solder paste, electronic components on the PCB board, etc., which are technologies known to those skilled in the art and will not be described in detail here.

[0018] Please refer to the following: Figure 2 and Figure 3 The PCB board 10 is made of insulating material and has a conductive copper foil pattern laid on its surface to form electrical connections between electronic components. The PCB board 10 itself is prior art and will not be described in detail here.

[0019] The LED bead 20 includes a bead body 21 and four pins 22 disposed on one side of the bead body 21.

[0020] The lamp bead body 21 is a light-emitting device that encapsulates three types of light-emitting chips: red, green, and blue. It is existing technology and will not be described in detail here.

[0021] The four pins 22 are located on both sides of the LED bead body 21, with at least two pins 22 on each side of the LED bead body 21. The pins 22 are L-shaped, with their openings facing the LED bead body 21. A bend 23 is formed at the bend in the middle of the pin 22. It should be noted that the bending arc of the bend 23 on the pins 22 on the left and right sides of the LED bead 20 varies due to manufacturing processes or mold issues, and this cannot be overcome. Also, the pins with larger bending arcs are all located on the same side and will not be diagonally opposite. In this embodiment, the bending arc of the right pin 22 is greater than that of the left pin 22.

[0022] When the pin 22 is soldered to the PCB board 10, there is a solder paste climbing area 40 between the bend 23 on the pin 22 and the edge of the pad. The solder paste climbing area 40 causes the liquid solder paste placed thereon to climb to the bend 23 under the action of wetting force, and even to the side wall of the pin 22. This pulls the pin 22, thereby causing the LED bead 20 to tilt.

[0023] The pad assembly 30 includes a first pad group 31 and a second pad group 32 disposed on one side of the first pad group 31.

[0024] The LED beads 20 are soldered one-to-one onto the first pad group 31 and the second pad group 32 respectively.

[0025] The first pad assembly 31 includes two first upper pads 311 spaced apart, and two first lower pads 312 spaced apart on one side of the first upper pads 311.

[0026] Each of the aforementioned pads is provided with solder paste 33 for soldering. The four pins 22 on the LED bead 20 are placed on the four solder pastes 33 respectively, and the solder paste 33 is heated by a hot air gun to melt it into a liquid state. After the liquid solder paste 33 solidifies, the LED bead 20 can be fixed on the four pads to ensure the stability of its electrical connection.

[0027] The distance between the two first upper pads 311 is less than the distance between the two first lower pads 312, thus forming a pad distribution pattern that is narrower at the top and wider at the bottom. When the four pins 22 on the LED bead 20 are respectively placed on the two first upper pads 311 and the two first lower pads 312, the width of the solder paste climbing area 40 at the two first upper pads 311 will be very narrow and smaller than the width of the solder paste climbing area in a conventional pad due to the close proximity of the two first upper pads 311. This results in a much smaller volume of liquid solder paste 33 in the solder paste climbing area 40 than in a conventional pad. As a result, even if the bend 23 has a large curvature, a large amount of liquid solder paste 33 will not climb up, thus avoiding the influence of the curvature difference of the bend 23 on the left and right sides, and thus maximally neutralizing the difference in wetting force between the left and right pins 22 and the solder paste 33.

[0028] The two first lower pads 312 correspond to the other two left and right pins 22. Since the two first lower pads 312 are far apart from each other, that is, the width of the solder paste climbing area 40 corresponding to the two first lower pads 312 is greater than the width of the solder paste climbing area in a conventional pad, and the bending part 23 with a large bending arc will cause a large amount of liquid solder paste to climb onto the side wall of the pin 22 at that point, thereby causing the LED bead 20 to be slightly tilted toward the first lower pad 312 on the right. In this way, the pad distribution structure of the following cross-row layout causes each LED bead 20 to be slightly tilted in different directions, avoiding the "yin-yang face" phenomenon caused by the LED bead 20 being tilted in the same direction.

[0029] The second pad group 32 includes two second upper pads 321 spaced apart, and two second lower pads 322 spaced apart on one side of the second upper pads 321.

[0030] The second pad group 32 has a similar structure to the first pad group 31, and is arranged at intervals across the first pad group 31. Each pad on it is provided with solder paste 33, and the distance between two second upper pads 321 is greater than the distance between two second lower pads 322, thus forming a pad distribution pattern that expands upwards and contracts downwards. The distance between two second upper pads 321 is equal to the distance between two first lower pads 312, and the distance between two second lower pads 322 is equal to the distance between two first upper pads 311. The second pad group 32 is essentially an inverted version of the first pad group 31, resulting in a cross-row arrangement of pads.

[0031] Since the first lower pad 312 on the right and the second upper pad 321 on the right will always be in contact with the curved portion 23 with a large curvature, the resulting effect will cause the LED bead 20 to be slightly tilted toward the first lower pad 312 or the second upper pad 321 on the right. The pad distribution structure with a cross-row arrangement can further balance the overall bias of light intensity distribution caused by the tilt of the LED bead 20, so that the LED bead 20 will be tilted toward the upper right or lower right. In this way, even if there is an effect, it will only be a slight pitting at a large angle, which is acceptable compared to "yin-yang face" or "tile".

[0032] Compared with the prior art, the solder pad distribution structure of the small-pitch LED provided by this utility model has a solder paste climbing area 40 with a width smaller than that of the climbing area in a conventional solder pad at the two first upper solder pads 311. This results in a much smaller volume of liquid solder paste 33 in the solder paste climbing area 40 compared to that in a conventional solder pad. Even with the large curvature of the bend 23, a large amount of liquid solder paste 33 will not climb up, thus avoiding the influence of the curvature difference of the bend 23 on the left and right sides, thereby maximizing the neutralization of the difference in wetting force between the left and right pins 22 and the solder paste 33. On the other hand, the width of the solder paste climbing area 40 corresponding to the two first lower solder pads 312 is larger than that of the climbing area in a conventional solder pad. The bend 23 with a large curvature will cause a large amount of liquid solder paste to climb onto the sidewall of the pin 22 at that location, thus causing the LED bead 20 to be slightly tilted towards the first lower solder pad 312 on the right side. Furthermore, the second pad group 32 is the inverted first pad group 31. The pad distribution in this way is arranged in a cross-row layout, which will cause the LED beads 20 to be slightly tilted in the direction of the upper right or lower right. This can further balance the overall bias of light intensity distribution caused by the tilt of the LED beads 20 and reduce the impact caused by the tilt in a single direction.

[0033] The above are merely preferred embodiments of the present utility model and are not intended to limit the scope of protection of the present utility model. Any modifications, equivalent substitutions or improvements within the spirit of the present utility model are covered within the scope of the claims of the present utility model.

Claims

1. A pad distribution structure for small-pitch LEDs, characterized in that: The pad distribution structure of the small-pitch LED includes a PCB board, a plurality of LED beads arranged on the PCB board, and a plurality of pad assemblies disposed between the PCB board and the LED beads. Each LED bead includes a bead body and four pins disposed on one side of the bead body. The pad assembly includes a first pad group and a second pad group disposed on one side of the first pad group. The first pad assembly includes two spaced-apart first upper pads and two spaced-apart first lower pads disposed on one side of the first upper pads. The distance between the two first upper pads is less than the distance between the two first lower pads. A bend is formed at the bend position in the middle of the pin. There is a solder paste creep area between the bend on the pin and the edge of the pad. The width of the solder paste creep area corresponding to the two first upper pads is less than the width of the solder paste creep area in a conventional pad.

2. The pad distribution structure for small-pitch LEDs according to claim 1, characterized in that: The four pins are located on both sides of the lamp bead body, and each side of the lamp bead body has at least two pins.

3. The pad distribution structure for small-pitch LEDs according to claim 1, characterized in that: The pin is L-shaped, and the opening faces the lamp bead body.

4. The pad distribution structure for small-pitch LEDs according to claim 1, characterized in that: The second pad group has a similar structure to the first pad group, and is arranged at intervals with the first pad group.

5. The pad distribution structure for small-pitch LEDs according to claim 1, characterized in that: The second pad group includes two second upper pads spaced apart, and two second lower pads spaced apart on one side of the second upper pads.

6. The pad distribution structure for small-pitch LEDs according to claim 5, characterized in that: The distance between the two second upper pads is greater than the distance between the two second lower pads.

7. The pad distribution structure for small-pitch LEDs according to claim 5, characterized in that: The distance between the two second upper pads is equal to the distance between the two first lower pads, and the distance between the two second lower pads is equal to the distance between the two first upper pads. The second pad group is the inverted first pad group.

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