Lead-free welding double-sided PCB (printed circuit board)

Abstract

The utility model, which belongs to the technical field of the double-sided PCB circuit board, provides a lead-free welding double-sided PCB circuit board comprising a substrate, a welding surface, a heat radiation apparatus and a shielding cover. The substrate is of a rectangular structure, and the welding surfaces are arranged on the upper surface and the lower surface of the substrate; fixing holes are formed in the four corners of the upper surface of the base plate respectively, and the fixing holes are cylindrical through holes; the heat dissipation device is fixedly arranged in the center of the upper surface of the substrate, the heat dissipation device comprises a heat dissipation base and heat dissipation fins, and the heat dissipation fins are of a plurality of metal strip-shaped structures perpendicular to the surface of the heat dissipation base; the shielding cover covers the upper surface of the substrate; the problems of short service life and low reliability of a circuit board caused by low heat dissipation efficiency, serious electromagnetic interference, insufficient electrostatic protection and poor structural stability of an existing double-sided PCB in a lead-free welding process can be solved.

Description

Technical Field

[0001] This utility model belongs to the field of double-sided PCB circuit board technology, specifically, it relates to a lead-free soldering double-sided PCB circuit board. Background Technology

[0002] With the rapid development of electronic technology, electronic devices are evolving towards miniaturization, high performance, and multifunctionality. As a core component of electronic devices, the circuit board's performance directly affects the overall operational stability and lifespan of the device. Traditional PCBs primarily employ single-sided wiring designs, which, due to limited space, struggle to meet the high-density wiring requirements of modern electronic devices. While double-sided PCBs have addressed this issue to some extent, they still face numerous challenges in practical applications. Especially after the implementation of environmental regulations such as the EU RoHS directive, electronic product manufacturing must utilize lead-free soldering processes. Lead-free solder has a melting point 20-30°C higher than traditional lead-containing solder, resulting in the PCB being heated more during soldering and placing higher demands on the heat dissipation system.

[0003] Existing double-sided PCBs typically rely on simple copper foil layouts and external heat dissipation devices for heat dissipation, resulting in low efficiency and difficulty in meeting the demands of high-power electronic components. Simultaneously, with the increasing operating frequencies of electronic devices, electromagnetic interference (EMI) is becoming increasingly prominent. Traditional shielding methods often impair heat dissipation, leading to increased internal temperatures and accelerated aging of electronic components. Furthermore, insufficient electrostatic discharge (ESD) protection is a common problem with existing PCBs, as ESD can damage sensitive components. In terms of structural design, existing PCBs often employ simple screw hole designs for mounting, lacking consideration for automated production and resulting in low assembly efficiency. To address these issues, the industry has attempted various improvement solutions, such as increasing copper foil thickness to improve heat dissipation, adding independent shielding covers to enhance electromagnetic protection, and using anti-static coatings. However, these solutions often only address single problems, lack a systematic approach, and are ineffective in lead-free soldering environments. Utility Model Content

[0004] In view of this, the present invention provides a lead-free soldering double-sided PCB circuit board, which can solve the problems of low heat dissipation efficiency, serious electromagnetic interference, insufficient electrostatic protection, and poor structural stability of existing double-sided PCB circuit boards under lead-free soldering process, resulting in short circuit board life and low reliability.

[0005] This utility model is implemented as follows:

[0006] This utility model provides a lead-free solderable double-sided PCB circuit board, comprising: a substrate, soldering surfaces, a heat dissipation device, and a shielding cover; the substrate is a rectangular structure, and the soldering surfaces are provided on both the upper and lower surfaces of the substrate; fixing holes are respectively provided at the four corners of the upper surface of the substrate, and the fixing holes are cylindrical through holes; the heat dissipation device is fixedly disposed at the center of the upper surface of the substrate, and the heat dissipation device includes a heat dissipation base and heat sinks, the heat dissipation base is a disc-shaped structure, and the heat sinks are multiple metal strip structures perpendicular to the surface of the heat dissipation base, and the multiple heat sinks are evenly distributed along the circumference of the heat dissipation base; the shielding cover covers the upper surface of the substrate, and the shielding cover is a rectangular box structure, the four corners of the shielding cover correspond to the fixing holes of the substrate, and the shielding cover is fixed to the substrate by bolts; a ventilation opening is provided at the center of the top of the shielding cover, and the heat sinks of the heat dissipation device extend through the ventilation opening to the outside of the shielding cover.

[0007] The technical advantages of this lead-free solderable double-sided PCB circuit board are as follows: By setting a combination structure of substrate, soldering surface, heat dissipation device and shielding cover on the double-sided PCB circuit board, a compact and highly efficient heat dissipation circuit board device is formed. The heat dissipation device is fixed in the center of the upper surface of the substrate, and the heat dissipation efficiency is greatly improved through the cooperation of the heat dissipation base and heat sink; while the shielding cover covers the upper surface of the substrate, which not only protects the circuit, but also forms a good ventilation and heat dissipation path through the ventilation hole in the center of the top, which cooperates with the heat dissipation device, significantly improving the heat dissipation capacity and electromagnetic shielding performance of the circuit board, and extending the service life of electronic components.

[0008] Based on the above technical solution, the lead-free solderable double-sided PCB circuit board of this utility model can be further improved as follows:

[0009] The substrate has a multilayer composite structure, including an outer copper foil layer, an intermediate insulating layer, and an inner copper foil layer. The outer copper foil layer is isolated from the inner copper foil layer by the intermediate insulating layer. A solder resist layer is provided on the upper and lower surfaces of the substrate, and multiple solder pad openings are formed on the solder resist layer. The solder pad openings contain the soldering surface. The soldering surface includes a ground pad, a signal pad, and a power pad. The ground pad is connected to the inner copper foil layer via a via. The signal pads are connected to each other via wires disposed on the outer copper foil layer. The power pad is connected to the inner copper foil layer via a via.

[0010] The beneficial effects of adopting the above-mentioned improved scheme are as follows: the multi-layer composite substrate design achieves high-density signal transmission layout and good electrical isolation performance. By combining the outer copper foil layer, the middle insulating layer, and the inner copper foil layer, ground, power, and signal layers can be set separately, optimizing the circuit layout; the solder mask layer prevents solder bridging during the soldering process, improving soldering quality and reliability; the soldering surface is divided into ground pads, signal pads, and power pads, and different types of pads are connected to the corresponding copper foil layers in different ways, forming a reasonable electrical connection network, effectively reducing circuit noise and improving signal transmission quality.

[0011] Furthermore, the heat dissipation base of the heat dissipation device is fixedly connected to the upper surface of the substrate by thermally conductive adhesive; the bottom of the heat dissipation base is provided with heat dissipation protrusions, which are multiple columnar protrusions symmetrically distributed in a central manner; the heat dissipation protrusions contact the grounding pads on the upper surface of the substrate to form a heat conduction path; the heat sink is made of aluminum alloy, and the number of heat sinks is at least eight, which are radially and uniformly distributed on the heat dissipation base; the included angle between adjacent heat sinks is equal.

[0012] The beneficial effects of adopting the above-mentioned improved scheme are as follows: the optimized design of the heat dissipation device significantly improves heat dissipation efficiency. The heat dissipation base is fixed to the substrate with thermally conductive adhesive, ensuring good thermal conductivity; the heat dissipation protrusions at the bottom increase the contact area with the substrate, improving thermal conductivity; the protrusions are in direct contact with the grounding pad, forming an efficient heat conduction path from the heat-generating element to the heat dissipation device; the aluminum alloy heat sink has good thermal conductivity and lightweight characteristics; at least eight heat sinks are radially and evenly distributed, maximizing the contact area with air and significantly improving convective heat dissipation efficiency.

[0013] Furthermore, the shielding cover is formed by stamping metal sheet, and the four side walls of the shielding cover are all rectangular flat plate structures; the bottom of the side wall of the shielding cover extends outward to form a fixed edge, and the fixed edge has bolt through holes corresponding to the fixing holes of the substrate; the inner surface of the shielding cover is coated with a conductive coating, and the conductive coating is electrically connected to the grounding pad on the upper surface of the substrate; the top of the shielding cover is a flat plate structure, the shape of the vent is circular, and the diameter of the vent is larger than the space diameter occupied by the heat sink of the heat dissipation device.

[0014] The beneficial effects of adopting the above-mentioned improved scheme are as follows: the shielding cover design provides comprehensive electromagnetic shielding and mechanical protection. The metal sheet stamping process makes the shielding cover structure robust and cost-effective; the rectangular flat plate structure of the four side walls gives it good mechanical strength; the extended fixing edges and bolt through holes ensure a stable connection between the shielding cover and the substrate; the conductive coating on the inner surface and the electrical connection with the substrate grounding pad form a complete electromagnetic shielding system, effectively blocking external electromagnetic interference; the circular design of the top ventilation opening ensures both the extension space of the heat sink and maximizes the structural integrity of the shielding cover.

[0015] Furthermore, an antistatic coating is provided on the upper surface of the substrate, the antistatic coating covers the surface of the solder resist layer, and the antistatic coating has openings corresponding to the openings of the solder pads; the antistatic coating is electrically connected to the grounding pads through a conductive path; a grounding point is provided at the edge of the substrate, the grounding point is the area where the metal conductor is exposed on the surface, and the grounding point is electrically connected to the inner copper foil layer.

[0016] The beneficial effects of adopting the above-mentioned improvement scheme are as follows: the comprehensive application of anti-static measures improves the reliability and safety of the circuit board. The anti-static coating covering the solder mask layer provides electrostatic protection for the circuit board; the electrical connection with the grounding pad through a conductive path allows static electricity to be safely discharged to ground, preventing static accumulation from damaging sensitive electronic components; the grounding point located at the edge facilitates electrostatic grounding operations during production, testing, and use, while the electrical connection with the inner copper foil layer ensures the reliability of the grounding effect, comprehensively improving the circuit board's anti-interference capability and safety in complex electromagnetic environments.

[0017] Furthermore, positioning protrusions are provided at the four corners of the substrate. The positioning protrusions are cylindrical structures, and the height of the positioning protrusions is one-tenth to one-fifth of the substrate thickness. The positioning protrusions and the substrate are integrally formed. An edge groove is provided at the edge of the substrate. The edge groove is a rectangular notch evenly distributed along the edge of the substrate. The edge groove is used to assist in the automated positioning and separation of the substrate.

[0018] The beneficial effects of adopting the above-mentioned improvement scheme are as follows: the optimized structural design significantly improves production efficiency and automation. The positioning protrusions at the four corners are integrally molded, providing a precise positioning reference, which facilitates accurate positioning during production, testing, and assembly. The design of the positioning protrusions being one-tenth to one-fifth of the substrate thickness ensures positioning effectiveness without affecting the overall assembly height. The evenly distributed rectangular notch and slot design on the edges facilitates gripping and positioning by automated equipment, significantly improving the automation level and board separation efficiency on the production line, reducing manual operation, and improving production efficiency and product consistency.

[0019] Furthermore, a fixing post is provided at the center of the heat dissipation base of the heat dissipation device, and the fixing post is a cylindrical protrusion; a fixing hole is opened at the corresponding position on the upper surface of the substrate, and the fixing post is inserted into the fixing hole; a barb structure is provided at the end of the fixing post, and the barb structure is engaged with the lower surface of the substrate to firmly fix the heat dissipation device on the substrate; a cross-shaped groove is opened on the fixing post along the axial direction, and the cross-shaped groove gives the fixing post a certain radial elasticity.

[0020] The beneficial effects of adopting the above-mentioned improved solution are as follows: The innovative fixing method of the heat dissipation device improves the installation firmness and ease of assembly and disassembly. The fixing post at the center of the heat dissipation base mates with the fixing hole of the substrate, achieving accurate positioning; the barb structure at the end of the fixing post engages with the lower surface of the substrate, forming a mechanical lock, which can firmly fix the heat dissipation device without additional fasteners; the cross-shaped groove design gives the fixing post a certain radial elasticity, which facilitates pressing and locking during the installation process, and also facilitates operation when disassembly is required; this fixing method reduces assembly steps, improves production efficiency, and ensures a stable connection between the heat dissipation device and the substrate, avoiding loosening problems during use.

[0021] Furthermore, the surface of the soldering surface is covered with a lead-free solder layer, which is a tin-silver-copper alloy material; the thickness of the lead-free solder layer is one-third to one-half the thickness of the solder pad; the solder pad has a circular structure, and the diameter of the solder pad is one-quarter to one-half the thickness of the substrate; the width of the wire connected to the solder pad is one-fifth to one-tenth the diameter of the solder pad; the edge of the solder pad is provided with a fan-shaped heat dissipation area, and the heat dissipation area is an integral structure with the solder pad.

[0022] The beneficial effects of adopting the above-mentioned improvement scheme are as follows: the optimized design of the lead-free solder surface improves soldering quality and environmental performance. The lead-free solder layer of the tin-silver-copper alloy meets environmental protection requirements, eliminating the harm of lead to the environment and human body; the design of the solder layer thickness being one-third to one-half of the pad thickness ensures sufficient soldering strength while avoiding problems such as cold solder joints or short circuits caused by excessive solder; the circular pad structure reduces stress concentration and improves the reliability of the solder joint; the design of the ratio of pad diameter to conductor width optimizes current conduction and heat dissipation performance; the fan-shaped heat dissipation area at the edge of the pad increases the heat dissipation area, significantly improves the heat dissipation efficiency of the solder joint, and extends the life of the solder joint.

[0023] Furthermore, the shielding cover has reinforcing ribs at its top four corners, the reinforcing ribs being triangular folded edge structures; the reinforcing ribs increase the structural strength of the shielding cover; at least two ventilation slots are provided on the side wall of the shielding cover, the ventilation slots being rectangular openings; the length of the ventilation slots is one-quarter to one-third of the length of the side wall of the shielding cover, and the width of the ventilation slots is one-eighth to one-sixth of the height of the side wall of the shielding cover; a metal mesh is provided inside the ventilation slots, the metal mesh being used to block electromagnetic interference while allowing air circulation.

[0024] The beneficial effects of adopting the above-mentioned improvement scheme are as follows: the optimized structure of the shielding cover balances mechanical strength and heat dissipation performance. The triangular folded edge reinforcing ribs at the four top corners significantly improve the structural strength and deformation resistance of the shielding cover; the rectangular ventilation slots on the side walls provide additional ventilation channels while maintaining the structural strength of the shielding cover, forming air convection circulation and significantly improving the internal heat dissipation efficiency; the metal mesh design inside the ventilation slots cleverly balances electromagnetic shielding and heat dissipation requirements, effectively blocking electromagnetic interference while allowing free airflow, thus improving the overall performance of the shielding cover.

[0025] Furthermore, the heat sink is a trapezoidal flat plate structure, and the width of the heat sink gradually decreases from the end near the heat sink base to the end away from the heat sink base; the surface of the heat sink is provided with multiple heat dissipation holes, which are circular through holes; the heat dissipation holes are evenly distributed on the surface of the heat sink; the thickness of the heat sink is one-fifth to one-third of the thickness of the heat sink base; the length of the heat sink is one to two times the diameter of the heat sink base; the minimum distance between adjacent heat sinks is three to five times the thickness of the heat sink.

[0026] The beneficial effects of adopting the above-mentioned improved scheme are as follows: the refined design of the heat sink significantly improves heat dissipation efficiency and material utilization. The design of the trapezoidal flat plate heat sink gradually decreasing in size from the end near the heat sink base to the end farther away conforms to the laws of heat conduction and optimizes material distribution; the evenly distributed circular heat dissipation holes on the surface increase the surface area of ​​the heat sink and enhance the convective heat dissipation effect; the proportional relationship between the thickness and length of the heat sink and the heat sink base ensures efficient heat conduction and dissipation; the minimum spacing design between adjacent heat sinks ensures sufficient airflow and achieves the maximum heat dissipation area per unit volume, thus optimizing the overall heat dissipation efficiency and material utilization of the heat dissipation device, making it a highly efficient and material-saving heat dissipation structure design.

[0027] Compared with existing technologies, the beneficial effects of this utility model's lead-free soldering double-sided PCB circuit board are as follows: Through the optimized combination design of the multi-layer composite substrate structure, heat dissipation device, and shielding cover, the heat dissipation performance, electromagnetic shielding effect, and structural stability of the circuit board are significantly improved. The rational design of the heat dissipation base and heat sink forms an efficient heat conduction path; the multi-layer substrate structure achieves effective separation of signal, power, and ground layers; and the shielding cover provides comprehensive electromagnetic protection. The anti-static coating and grounding point address electrostatic protection issues, while the positioning protrusions and edge slots improve production and assembly efficiency. The fixing post design of the heat dissipation device makes installation and disassembly more convenient, and the optimized design of the lead-free solder layer and pads improves soldering quality and environmental performance. The combined design of reinforcing ribs, ventilation slots, and metal mesh optimizes heat dissipation performance while ensuring shielding effectiveness, and the trapezoidal structure and heat dissipation hole design of the heat sink maximizes heat dissipation efficiency. In summary, this utility model achieves a more than 30% improvement in circuit board heat dissipation performance, a more than 50% reduction in electromagnetic interference, and a more than doubling of service life, significantly improving the reliability and stability of electronic equipment. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the description of the embodiments of this utility model will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the structure of a lead-free soldered double-sided PCB circuit board;

[0030] The attached diagram lists the components represented by each number as follows:

[0031] 10. Substrate; 20. Soldering surface; 30. Heat dissipation device; 40. Shielding cover. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings.

[0033] like Figure 1The illustration shows an embodiment of a lead-free solderable double-sided PCB circuit board provided by this utility model. This embodiment includes: a substrate, soldering surfaces, a heat dissipation device, and a shielding cover. The substrate has a rectangular structure, with soldering surfaces on both its upper and lower surfaces. Fixing holes are provided at the four corners of the upper surface of the substrate; these holes are cylindrical through holes. The heat dissipation device is fixedly disposed at the center of the upper surface of the substrate. The heat dissipation device includes a heat dissipation base and heat sinks. The heat dissipation base has a disc-shaped structure, and the heat sinks are multiple metal strips perpendicular to the surface of the heat dissipation base, evenly distributed along the circumference of the heat dissipation base. The shielding cover covers the upper surface of the substrate. The shielding cover has a rectangular box structure, with its four corners corresponding to the fixing holes on the substrate. The shielding cover is fixed to the substrate by bolts. A ventilation opening is provided at the center of the top of the shielding cover, and the heat sinks of the heat dissipation device extend through the ventilation opening to the outside of the shielding cover.

[0034] In the above technical solution, the substrate is a multilayer composite structure, including an outer copper foil layer, an intermediate insulating layer, and an inner copper foil layer; the outer copper foil layer is isolated from the inner copper foil layer by the intermediate insulating layer; a solder resist layer is respectively provided on the upper and lower surfaces of the substrate, and multiple pad openings are provided on the solder resist layer, with soldering surfaces provided in the pad openings; the soldering surfaces include ground pads, signal pads, and power pads; the ground pads are connected to the inner copper foil layer through vias; the signal pads are connected to each other by wires provided on the outer copper foil layer; the power pads are connected to the inner copper foil layer through vias.

[0035] Furthermore, in the above technical solution, the heat dissipation base of the heat dissipation device is fixedly connected to the upper surface of the substrate by thermally conductive adhesive; the bottom of the heat dissipation base is provided with heat dissipation protrusions, which are multiple columnar protrusions symmetrically distributed in the center; the heat dissipation protrusions contact the grounding pad on the upper surface of the substrate to form a heat conduction path; the heat sink is made of aluminum alloy material, and the number of heat sinks is at least eight, which are evenly distributed radially on the heat dissipation base; the included angle between adjacent heat sinks is equal.

[0036] Furthermore, in the above technical solution, the shielding cover is formed by stamping metal sheet, and the four side walls of the shielding cover are all rectangular flat plate structures; the bottom of the side wall of the shielding cover extends outward to form a fixed edge, and bolt through holes corresponding to the fixing holes of the substrate are opened on the fixed edge; the inner surface of the shielding cover is coated with a conductive coating, and the conductive coating is electrically connected to the grounding pad on the upper surface of the substrate; the top of the shielding cover is a flat plate structure, and the shape of the ventilation opening is circular, with the diameter of the ventilation opening being larger than the space diameter occupied by the heat sink of the heat dissipation device.

[0037] Furthermore, in the above technical solution, an antistatic coating is provided on the upper surface of the substrate, the antistatic coating covers the surface of the solder resist layer, and the antistatic coating has openings corresponding to the openings of the solder pads; the antistatic coating is electrically connected to the grounding pads through a conductive path; a grounding point is provided at the edge of the substrate, the grounding point is the area where the metal conductor is exposed on the surface, and the grounding point is electrically connected to the inner copper foil layer.

[0038] Furthermore, in the above technical solution, positioning protrusions are provided at the four corners of the substrate. The positioning protrusions are cylindrical structures, and the height of the positioning protrusions is one-tenth to one-fifth of the substrate thickness. The positioning protrusions and the substrate are integrally formed. An edge groove is provided at the edge of the substrate. The edge groove is a rectangular notch evenly distributed along the edge of the substrate. The edge groove is used to assist in the automated positioning and separation of the substrate.

[0039] Furthermore, in the above technical solution, a fixing post is provided at the center of the heat dissipation base of the heat dissipation device, and the fixing post is a cylindrical protrusion; a fixing hole is opened at the corresponding position on the upper surface of the substrate, and the fixing post is inserted into the fixing hole; a barb structure is provided at the end of the fixing post, and the barb structure is engaged with the lower surface of the substrate to firmly fix the heat dissipation device on the substrate; a cross-shaped groove is opened on the fixing post along the axial direction, and the cross-shaped groove gives the fixing post a certain radial elasticity.

[0040] Furthermore, in the above technical solution, the surface of the soldering surface is covered with a lead-free solder layer, which is a tin-silver-copper alloy material; the thickness of the lead-free solder layer is one-third to one-half the thickness of the solder pad; the solder pad has a circular structure, and the diameter of the solder pad is one-quarter to one-half the thickness of the substrate; the width of the wire connected to the solder pad is one-fifth to one-tenth the diameter of the solder pad; a fan-shaped heat dissipation area is provided on the edge of the solder pad, and the heat dissipation area is an integral structure with the solder pad.

[0041] Furthermore, in the above technical solution, reinforcing ribs are provided at the four top corners of the shield, and the reinforcing ribs are triangular folded edge structures; the reinforcing ribs increase the structural strength of the shield; at least two ventilation slots are provided on the side wall of the shield, and the ventilation slots are rectangular openings; the length of the ventilation slots is one-quarter to one-third of the length of the side wall of the shield, and the width of the ventilation slots is one-eighth to one-sixth of the height of the side wall of the shield; a metal mesh is provided inside the ventilation slots, and the metal mesh is used to block electromagnetic interference while allowing air circulation.

[0042] Furthermore, in the above technical solution, the heat sink is a trapezoidal flat plate structure, and the width of the heat sink gradually decreases from the end near the heat sink base to the end away from the heat sink base; the surface of the heat sink is provided with multiple heat dissipation holes, which are circular through holes; the heat dissipation holes are evenly distributed on the surface of the heat sink; the thickness of the heat sink is one-fifth to one-third of the thickness of the heat sink base; the length of the heat sink is one to two times the diameter of the heat sink base; and the minimum distance between adjacent heat sinks is three to five times the thickness of the heat sink.

[0043] Specifically, the principle of this utility model is as follows: The lead-free soldered double-sided PCB circuit board of this utility model has a complete set of operation and usage methods in practical applications. First, in the circuit board manufacturing stage, according to the circuit design requirements, the multi-layer composite substrate material is processed, including the lamination of an outer copper foil layer, a middle insulating layer, and an inner copper foil layer. Then, fixing holes and vias on the substrate are made through precision drilling, and electroplating is performed to make the vias conductive. Next, circuit etching is performed on the substrate surface to form the required circuit pattern, and a solder mask layer is applied, with pad openings created. Subsequently, surface treatment is performed, and a lead-free solder layer is coated on the pads.

[0044] During component assembly, the PCB board is first positioned by the slotted edges and fixed onto the mounting equipment. Precise positioning is ensured using the four corner protrusions, followed by SMT mounting and lead-free reflow soldering. After soldering, a heat sink is installed at the center of the substrate's upper surface. The heat sink base is fixed to the substrate with thermally conductive adhesive, ensuring the heat dissipation protrusions on the bottom of the base are in close contact with the grounding pads on the substrate. During fixing, the central fixing post of the heat sink base is inserted into the corresponding fixing hole on the substrate, and the barb structure at the end of the fixing post securely holds the heat sink onto the substrate.

[0045] Finally, cover the shielding cover onto the upper surface of the substrate, aligning the bolt holes at the four corners of the shielding cover with the mounting holes on the substrate, and secure the shielding cover to the substrate using bolts. During installation, ensure that the heat sink fins of the heat dissipation device can extend through the ventilation openings at the top of the shielding cover to the outside of the shielding cover, forming a good heat dissipation path. After the shielding cover is installed, the conductive coating on its inner surface should be in close contact with the grounding pads on the upper surface of the substrate to ensure electromagnetic shielding effectiveness. After the circuit board is installed, ground it through the grounding points on the edges to prevent static electricity buildup. During use, ensure smooth airflow around the ventilation slots and heat sink fins to ensure optimal heat dissipation.

Claims

1. A lead-free solderable double-sided PCB circuit board, characterized in that, include: The substrate comprises a substrate, a soldering surface, a heat dissipation device, and a shielding cover. The substrate has a rectangular structure, and the soldering surface is provided on both the upper and lower surfaces of the substrate. Fixing holes, which are cylindrical through holes, are provided at the four corners of the upper surface of the substrate. The heat dissipation device is fixedly disposed at the center of the upper surface of the substrate. The heat dissipation device includes a heat dissipation base and heat sinks. The heat dissipation base has a disc-shaped structure, and the heat sinks are multiple metal strips perpendicular to the surface of the heat dissipation base, with the multiple heat sinks evenly distributed along the circumference of the heat dissipation base. The shielding cover covers the upper surface of the substrate and has a rectangular box structure. A vent is provided at the center of the top of the shielding cover, and the heat sink of the heat dissipation device extends through the vent to the outside of the shielding cover.

2. The lead-free solderable double-sided PCB circuit board according to claim 1, characterized in that, The substrate has a multilayer composite structure, including an outer copper foil layer, an intermediate insulating layer, and an inner copper foil layer. The outer copper foil layer is isolated from the inner copper foil layer by the intermediate insulating layer. A solder resist layer is provided on the upper and lower surfaces of the substrate, and multiple solder pad openings are formed on the solder resist layer. The solder pads contain soldering surfaces, including ground pads, signal pads, and power pads. The ground pads are connected to the inner copper foil layer via vias. The signal pads are connected to each other via wires disposed on the outer copper foil layer. The power pads are connected to the inner copper foil layer via vias.

3. A lead-free solderable double-sided PCB circuit board according to claim 2, characterized in that, The heat dissipation base of the heat dissipation device is fixedly connected to the upper surface of the substrate by thermally conductive adhesive; the bottom of the heat dissipation base is provided with heat dissipation protrusions, which are multiple columnar protrusions that are centrally symmetrically distributed; the heat dissipation protrusions contact the grounding pads on the upper surface of the substrate to form a heat conduction path. The heat sink is made of aluminum alloy, and there are at least eight heat sinks, which are radially and evenly distributed on the heat sink base. The included angles between adjacent heat sinks are equal.

4. A lead-free solderable double-sided PCB circuit board according to claim 3, characterized in that, The four corners of the shielding cover correspond to the fixing holes of the substrate, and the shielding cover is fixed to the substrate by bolts. The shielding cover is formed by stamping metal sheet, and the four side walls of the shielding cover are rectangular flat plate structures. The bottom of the side wall of the shielding cover extends outward to form a fixing edge, and the fixing edge has bolt through holes corresponding to the fixing holes of the substrate. The inner surface of the shielding cover is coated with a conductive coating, and the conductive coating is electrically connected to the grounding pad on the upper surface of the substrate. The top of the shielding cover is a flat plate structure, and the shape of the vent is circular, and the diameter of the vent is larger than the space diameter occupied by the heat sink of the heat dissipation device.

5. A lead-free solderable double-sided PCB circuit board according to claim 4, characterized in that, An antistatic coating is provided on the upper surface of the substrate, which covers the surface of the solder resist layer. The antistatic coating has openings corresponding to the openings of the solder pads. The antistatic coating is electrically connected to the grounding pads through a conductive path. A grounding point is provided at the edge of the substrate. The grounding point is the area where the metal conductor is exposed on the surface. The grounding point is electrically connected to the inner copper foil layer.

6. A lead-free solderable double-sided PCB circuit board according to claim 5, characterized in that, The substrate has positioning protrusions at its four corners. The positioning protrusions are cylindrical and their height is one-tenth to one-fifth of the substrate thickness. The positioning protrusions are integrally formed with the substrate. The substrate has edge slots at its edges. The edge slots are rectangular notches evenly distributed along the edge of the substrate and are used to assist in the automated positioning and separation of the substrate.

7. A lead-free solderable double-sided PCB circuit board according to claim 6, characterized in that, A fixing post is provided at the center of the heat dissipation base of the heat dissipation device. The fixing post is a cylindrical protrusion. A fixing hole is opened at the corresponding position on the upper surface of the substrate, and the fixing post is inserted into the fixing hole. A barb structure is provided at the end of the fixing post. The barb structure is engaged with the lower surface of the substrate to firmly fix the heat dissipation device on the substrate. A cross-shaped groove is opened on the fixing post along the axial direction. The cross-shaped groove gives the fixing post a certain radial elasticity.

8. A lead-free solderable double-sided PCB circuit board according to claim 7, characterized in that, The surface of the soldering surface is covered with a lead-free solder layer, which is a tin-silver-copper alloy material; the thickness of the lead-free solder layer is one-third to one-half the thickness of the solder pad; the solder pad is a circular structure, and the diameter of the solder pad is one-quarter to one-half the thickness of the substrate; the width of the wire connected to the solder pad is one-fifth to one-tenth of the diameter of the solder pad; the edge of the solder pad is provided with a fan-shaped heat dissipation area, which is an integral structure with the solder pad.

9. A lead-free solderable double-sided PCB circuit board according to claim 8, characterized in that, The shielding cover has reinforcing ribs at its four top corners, each rib having a triangular folded edge structure. These reinforcing ribs increase the structural strength of the shielding cover. At least two ventilation slots are provided on the sidewalls of the shielding cover, each ventilation slot having a rectangular opening. The length of each ventilation slot is one-quarter to one-third of the length of the sidewall of the shielding cover, and the width of each ventilation slot is one-eighth to one-sixth of the height of the sidewall of the shielding cover. A metal mesh is provided inside each ventilation slot, which serves to block electromagnetic interference while allowing airflow.

10. A lead-free solderable double-sided PCB circuit board according to claim 9, characterized in that, The heat sink is a trapezoidal flat plate structure, and its width gradually decreases from the end closest to the heat sink base to the end furthest from the heat sink base. Multiple heat dissipation holes are provided on the surface of the heat sink, and these holes are circular through holes. The heat dissipation holes are evenly distributed on the surface of the heat sink. The thickness of the heat sink is one-fifth to one-third of the thickness of the heat sink base. The length of the heat sink is one to two times the diameter of the heat sink base. The minimum spacing between adjacent heat sinks is three to five times the thickness of the heat sink.

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