A tin joint prevention rhombus pad structure for high-density PCBA

Abstract

The utility model relates to a display card mainboard technical field especially a kind of anti-tinning rhombus pad structure for high-density PCBA, including the substrate of the pad of being equipped with several rhombus structures;Solder resist is provided with the avoiding hole for avoiding the pad in the upper portion of the substrate, solder resist constructs solder resist dam between adjacent two pads;Wherein, the upper portion of the pad is also provided with plating structure, the utility model is designed by adopting rhombus pad, cooperates the synergic effect of solder resist and plating structure, significantly improves high-density PCBA welding yield and reliability, especially applicable to micro pitch welding scene such as display card GPU, high-speed connector;Through pad long axis oblique design, effectively increase the equivalent spacing of adjacent pad, greatly reduce the tinning defect rate, the synergic effect of solder resist and plating structure, significantly enhance the tensile strength of solder joint and improve high-frequency signal return loss.

Description

Technical Field

[0001] This utility model relates to the field of graphics card motherboard technology, and in particular to a diamond-shaped solder pad structure for preventing solder bridging in high-density PCBA. Background Technology

[0002] With the rapid development of electronic devices towards higher density and miniaturization, the component layout on circuit boards such as graphics cards and server motherboards is becoming increasingly compact, and the spacing between solder pads has been reduced to 0.5mm or less. Under such micro-pitch conditions, traditional rectangular solder pads are prone to irregular diffusion during wave soldering due to the surface tension of the solder, resulting in solder bridging (i.e., solder joints) between adjacent pads, which can cause short circuits and seriously affect product yield and long-term reliability.

[0003] To address these issues, existing technologies typically employ two methods: one is to reduce the pad size to decrease the solder contact area, thereby reducing the risk of bridging; the other is to increase the coverage of the solder mask layer, using a physical barrier to restrict solder flow. However, both methods have significant drawbacks: reducing the pad size weakens the mechanical bond strength between the solder joint and the pad, leading to a decrease in the tensile strength of the solder joint; while increasing the solder mask layer coverage may cause impedance mismatch problems, especially in high-frequency signal transmission paths, where changes in the dielectric constant of the solder mask layer can induce signal reflection and loss, affecting signal integrity.

[0004] Therefore, in order to suppress the problem of solder bridging in high-density PCBAs, we propose a diamond-shaped pad structure for preventing solder bridging in high-density PCBAs. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies, such as the irregular diffusion of solder due to surface tension during wave soldering of traditional rectangular pads, which leads to solder bridging between adjacent pads. Therefore, this invention proposes a diamond-shaped pad structure for high-density PCBAs to prevent solder bridging.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: Design a diamond-shaped pad structure to prevent solder bridging for high-density PCBA, including a substrate with pads configured with a number of diamond structures; A solder resist layer is provided above the substrate. The solder resist layer has clearance holes to avoid the pads. The solder resist layer forms a solder resist dam between two adjacent pads. The solder pads are also provided with a plating structure above them.

[0007] Furthermore, the long axis of the pad is tilted at an angle of 15°-45° to the arrangement direction of the adjacent pads; The ratio of the major axis length to the minor axis length of the pad is greater than or equal to 1.4 and less than or equal to 1.6.

[0008] Furthermore, the solder resist layer includes: A solder resist ink layer formed on the surface of the substrate; And a photosensitive material layer covering the solder resist ink layer.

[0009] Furthermore, the width of the weld barrier dam is 0.1mm-0.15mm.

[0010] Furthermore, the plating structure includes a chemical nickel layer, a palladium layer, and an immersion gold layer sequentially deposited on the surface of the pad; Several grooves are also arrayed along the edge of the coating structure.

[0011] Furthermore, the thickness of the electroless nickel layer is 4 μm - 6 μm; The thickness of the palladium layer is 0.05 μm - 0.1 μm; The thickness of the gold immersion layer is 0.03μm - 0.08μm; The depth of the groove is 2μm-3μm.

[0012] The present invention proposes a diamond-shaped pad structure for preventing solder bridging in high-density PCBA. The beneficial effects are as follows: By adopting the design of diamond-shaped pads, combined with the synergistic effect of the solder mask layer and the plating layer structure, the present invention significantly improves the soldering yield and reliability of high-density PCBA, and is particularly suitable for micro-pitch soldering scenarios such as graphics card GPUs and high-speed connectors. By using the long axis tilt design of the solder pads, the equivalent spacing between adjacent solder pads is effectively increased, significantly reducing the solder bridging defect rate. The synergistic effect of the solder mask layer and the plating layer structure significantly enhances the tensile strength of the solder joints and improves the return loss of high-frequency signals. Solder control is achieved through geometric optimization and co-design of structural layers, effectively solving the bridging defect in high-density soldering, while significantly improving electrical performance and mechanical reliability. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the structure of this utility model; Figure 2 This is a schematic diagram of the weld barrier dam structure of this utility model; Figure 3 This is a schematic diagram of the coating structure of this utility model.

[0014] In the figure: 1. Substrate; 10. Pad; 2. Solder resist layer; 20. Solder resist dam; 21. Solder resist ink layer; 22. Photosensitive material layer; 3. Plating structure; 31. Chemical nickel layer; 32. Palladium layer; 33. Immersion gold layer; 34. Groove. Detailed Implementation

[0015] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments.

[0016] Reference Figure 1-3 As one embodiment of this utility model, a rhomboid pad structure for preventing solder bridging in high-density PCBA is disclosed. Specifically, the pad structure includes a substrate 1 with a plurality of rhomboid pads 10 arranged in a straight line above the substrate 1. Of course, in this embodiment, a via structure design can be adopted on the surface of the substrate 1, and a copper layer is electroplated in the via. The pads 10 are connected above the electroplated copper layer. The above is an example of a single-layer pad 10 structure. Those skilled in the art will obviously know that the same structure design can be adopted on both sides of the substrate 1 to achieve the via conductivity design by using two pads 10 to connect the electroplated copper layer of the via. This method is a conventional technical means for those skilled in the art and will not be described in detail here. A solder resist layer 2 is provided above the substrate 1. The solder resist layer 2 has clearance holes to avoid the pads 10. The solder resist layer 2 forms a solder resist dam 20 between two adjacent pads 10. The solder pad 10 is further provided with a plating structure 3 above it.

[0017] In some embodiments, the long axis direction of the pad 10 in this invention is inclined at an angle of 15°-45° to the arrangement direction of the adjacent pads 10; The ratio of the major axis length to the minor axis length of the pad 10 is greater than or equal to 1.4 and less than or equal to 1.6. That is, in this embodiment, by adopting an inclined design for the major axis of the diamond-shaped pad 10, the equivalent spacing between adjacent pads is increased by 18%-25%, which can effectively reduce the solder bridging defect rate.

[0018] Furthermore, in this embodiment, the solder mask layer 2 includes: Solder resist ink layer 21 formed on the surface of the substrate 1; And a photosensitive material layer 22 covering the solder resist ink layer 21.

[0019] In an optional embodiment, the solder resist ink layer 21 of this invention is a solder resist ink layer with a high glass transition temperature Tg ≥ 180℃, and the dielectric constant Dk of the photosensitive material layer 22 is ≤ 3.0. The photosensitive material layer 22 can be configured as a photosensitive dry film or a liquid photoresist. The thickness of the solder resist ink layer 21 is 10μm–30μm, and the thickness of the photosensitive material layer 22 is 5μm–20μm.

[0020] Furthermore, the width of the weld barrier dam 20 in this embodiment is 0.1mm-0.15mm.

[0021] In some embodiments, the plating structure 3 includes a chemical nickel layer 31, a palladium layer 32, and an immersion gold layer 33 sequentially deposited on the surface of the pad 10; Several grooves 34 are also arranged in an array along the edge of the coating structure 3.

[0022] Specifically, the thickness of the electroless nickel layer 31 is 4μm-6μm; The thickness of the palladium layer 32 is 0.05 μm - 0.1 μm; The thickness of the gold immersion layer 33 is 0.03μm - 0.08μm; The depth of the groove 34 is 2μm-3μm.

[0023] In a specific embodiment, taking a 0.4mm pitch BGA package as an example: The major axis of pad 10 is set to 0.35mm, the minor axis is set to 0.25mm, and its tilt angle is set to 15°. The total width of the solder resist dam 20 is set to 0.12 mm. The solder resist ink layer 21 is made of 25 μm thick Tg180℃ ink, and the photosensitive material layer 22 is made of 15 μm thick Dk2.8 photosensitive material. In addition, the electroless nickel layer 31 can be designed to be 5 μm thick, the palladium layer 32 can be set to 0.08 μm thick, the immersion gold layer can be set to 0.05 μm thick, and the depth of the groove 34 can be set to 2.5 μm thick.

[0024] In summary, this utility model, by adopting the design of diamond-shaped solder pads 10, combined with the synergistic effect of solder resist layer 2 and plating structure 3, significantly improves the soldering yield and reliability of high-density PCBA, and is particularly suitable for micro-pitch soldering scenarios such as graphics card GPUs and high-speed connectors. By using the inclined design of the long axis of the pad 10, the equivalent spacing between adjacent pads is effectively increased, significantly reducing the solder bridging defect rate. The synergistic effect of the solder mask layer 2 and the plating structure 3 significantly enhances the tensile strength of the solder joint and improves the return loss of high-frequency signals. Solder control is achieved through geometric optimization and co-design of structural layers, effectively solving the bridging defect in high-density soldering, while significantly improving electrical performance and mechanical reliability.

[0025] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the technical scope disclosed in the present utility model, based on the technical solution and the inventive concept of the present utility model, should be included within the protection scope of the present utility model.

Claims

1. A diamond-shaped pad structure for preventing solder bridging in high-density PCBAs, characterized in that, The substrate (1) includes a number of diamond-shaped pads (10). A solder resist layer (2) is provided above the substrate (1). The solder resist layer (2) has clearance holes to avoid the pads (10). The solder resist layer (2) forms a solder resist dam (20) between two adjacent pads (10). The pad (10) is also provided with a plating structure (3) above it.

2. The anti-tin bridging diamond-shaped pad structure for high-density PCBA according to claim 1, characterized in that: The long axis of the pad (10) is tilted at an angle of 15°-45° to the arrangement direction of the adjacent pads (10); The ratio of the major axis length to the minor axis length of the pad (10) is greater than or equal to 1.4 and less than or equal to 1.

6.

3. The anti-tin bridging diamond-shaped pad structure for high-density PCBA according to claim 1, characterized in that: The solder resist layer (2) includes: Solder resist ink layer (21) formed on the surface of the substrate (1); And a photosensitive material layer (22) covering the solder resist ink layer (21).

4. The anti-tin bridging diamond-shaped pad structure for high-density PCBA according to claim 3, characterized in that: The width of the weld barrier dam (20) is 0.1mm-0.15mm.

5. The anti-tin bridging diamond-shaped pad structure for high-density PCBA according to claim 1, characterized in that: The plating structure (3) includes a chemical nickel layer (31), a palladium layer (32) and an immersion gold layer (33) sequentially deposited on the surface of the pad (10). Several grooves (34) are also arranged in an array along the edge of the coating structure (3).

6. The anti-bridging diamond-shaped pad structure for high-density PCBA according to claim 5, characterized in that: The thickness of the electroless nickel layer (31) is 4 μm - 6 μm; The thickness of the palladium layer (32) is 0.05 μm - 0.1 μm; The thickness of the gold immersion layer (33) is 0.03 μm - 0.08 μm; The depth of the groove (34) is 2μm-3μm.

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