Pad reinforcing structure and circuit board manufacturing process

Abstract

The invention relates to a bonding pad reinforcing structure and a circuit board manufacturing process, the bonding pad reinforcing structure comprises a PCB with a multi-layer structure, the PCB comprises an outer dielectric layer and a bonding pad arranged on the outer dielectric layer, the bonding pad reinforcing structure is characterized in that the edge of the bonding pad is connected with a plurality of reinforcing parts, the reinforcing parts and the bonding pad are made of the same material, and the bonding pad is made of the same material. The outer dielectric layer is provided with a blind hole at an open position on the periphery of the bonding pad, and the reinforcing part extends into the blind hole and is not conductively connected with a circuit of the inner layer of the PCB. According to the bonding pad reinforcing structure, the reinforcing parts which are integrally connected and embedded in the blind holes are additionally arranged on the periphery of the bonding pad, so that the walls of the blind holes generate acting force on the reinforcing parts under the condition that short circuit is not caused, the edge of the bonding pad is pulled, the bonding pad is prevented from falling off from the outer dielectric layer in the SMT process, and the percent of pass of products is improved. The process comprises the steps of drilling, copper plating, pattern transferring, etching and film removing. The reinforcing part can be generated during copper plating, so that the bonding pad is reinforced on the basis of not increasing process steps, and the manufacturing is simple.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of printed wiring board, in particular to a kind of pad reinforcing structure and circuit board manufacturing process. BACKGROUND

[0002] With the development of FP-COIL (fine pitch coil) product technology, the product line width grade requirement is more and more fine, which leads to the product must choose SAP (semi-additive process) process to make, which leads to the adhesion of SMT (surface mount technology) welding PAD (solder pad) and substrate surface becomes small, which leads to the product under the action of stress after welding, the copper PAD and substrate of product welding fall off and separate, finally form poor welding, this paper studies how to improve the adhesion of SMT welding PAD and substrate, to ensure that FP-COIL product will not be affected by stress when welding based on SAP process, causing substrate adhesion problem.

[0003] Chinese patent CN105792512A discloses a kind of pad reinforcing structure, including the PCB board of multiple layer structure and pad, the pad is located at the surface layer of the PCB board, it further includes via, the via passes through pad and the PCB board, so that the metal of the pad is fused together between the metal of the via and the insulating layer on the PCB board.The present application strengthens the stress structure of surface layer pad, and is not easy to fall off.Only the via here can be multiple, but without exception will penetrate the pad, but the lower projection range of pad may be covered by the useful part of the line of the next layer, the metal filled in the via will cause short circuit, so such setting has requirement to the structure of product, and the degree of freedom is limited.

[0004] Chinese patent CN203015288U discloses an electronic product pad anti-falling structure, including the PCB board of multiple layer structure, the surface layer of the PCB board is provided with pad, the surface layer and the second layer below the surface layer of the PCB board are provided with through hole, the second layer is fixed with metal foil at the position corresponding to the pad, and the pad is connected together with the metal foil through the through hole.So here the pad and the metal foil also have the relationship of vertically opposite.

[0005] Therefore, it is necessary to design a new circuit board structure to solve the above problems. SUMMARY

[0006] One of the main purposes of the present application is to provide a kind of pad reinforcing structure, can make blind hole wall force on reinforcing part without causing short circuit, avoid pad from outer dielectric layer in SMT process fall off.

[0007] The application realizes the above-mentioned purpose through the following technical scheme: a solder pad reinforcing structure, comprising a PCB board with a multi-layer structure, the PCB board comprising an outer dielectric layer and a solder pad arranged on the outer dielectric layer, the edge of the solder pad being connected with a plurality of reinforcing parts, the reinforcing parts being made of the same material as the solder pad, the outer dielectric layer being provided with a blind hole at a vacant position around the solder pad, and the reinforcing parts extending into the blind hole and not being in conductive connection with the circuit in the inner layer of the PCB board.

[0008] Specifically, the blind hole is a screw hole, and the reinforcing part fills the sidewall of the blind hole.

[0009] Specifically, the PCB board further comprises a plurality of inner metal layers and a plurality of inner dielectric layers alternately laminated, and the blind hole passes through at least one inner dielectric layer.

[0010] Further, the inner metal layer is provided with a prefabricated tensile part at the position where the reinforcing part is located and passes through the blind hole, the prefabricated tensile part is not in conductive connection with the circuit in the inner layer of the PCB board, the prefabricated tensile part is made of the same material as the reinforcing part and is integrated with the reinforcing part.

[0011] Specifically, the surface of the PCB board is further provided with a solder mask layer, the solder mask layer is windowed at the position of the solder pad and covers the reinforcing part.

[0012] Another main purpose of the application is to provide a circuit board manufacturing process for manufacturing a PCB board with a solder pad reinforcing structure.

[0013] The application realizes the above-mentioned purpose through the following technical scheme: a circuit board manufacturing process for manufacturing a PCB board with a solder pad reinforcing structure, the steps comprising: S1, drilling: preparing a base material with an outer dielectric layer, drilling on the surface of the base material, the position of the drilling including a blind hole at the design position of the reinforcing part, obtaining a drilled base plate; S2, copper plating: first chemically depositing copper on the surface of the drilled base material, then electroplating copper on the surface thereof, metalizing all the blind holes, and making the copper layer cover the surface of the outer dielectric layer, obtaining a copper-plated plate; S3, pattern transfer: coating photoresist on the surface of the copper-plated plate, then exposing and developing, removing the uncured photoresist, and the cured photoresist covering the design position of the solder pad and the design position of the reinforcing part, obtaining a photoresist-coated plate; S4, etching: etching the copper surface not covered by the photoresist, leaving the design area of the circuit, solder pad and reinforcing part, obtaining an etched plate; S5, film removal: removing the cured photoresist, obtaining a PCB board.

[0014] Specifically, the drilling step adopts a laser drilling method, and the drilling depth of the blind hole where the reinforcing part is located is 60-100% of the depth of the outer medium layer.

[0015] Specifically, the drilling step adopts a mechanical drilling method, and a thread structure is left on the surface of the blind hole where the reinforcing part is located.

[0016] Specifically, before the substrate is prepared, a prefabricated tensile part is reserved in the inner part of the outer medium layer, and the position of the prefabricated tensile part covers the range of the blind hole where the reinforcing part is located; when drilling, the blind hole where the reinforcing part is located passes through the prefabricated tensile part; when copper plating, the metalization of the blind hole makes the reinforcing part generated and the prefabricated tensile part become an integral whole.

[0017] Specifically, the process further includes surface solder mask, and the method is to cover the surface of the PCB with solder mask ink, to perform windowing on the solder mask ink including the position where the solder pad is located, and to form a solder mask layer covering the reinforcing part by curing the solder mask ink.

[0018] The beneficial effects of the technical scheme of the present application are: 1. The solder pad reinforcing structure increases a plurality of reinforcing parts which are integrally connected and embedded in the blind hole around the solder pad, and in the case of not causing short circuit, the blind hole wall exerts force on the reinforcing part, thereby pulling the edge of the solder pad, avoiding the solder pad from falling off the outer medium layer in the SMT process, and improving the product qualification rate.

[0019] 2. The position of the reinforcing part can be independent of the limitation of the solder pad range, so that it can be set in the open area on the PCB and the appropriate number is selected, and the method is flexible.

[0020] 3. The reinforcing part can be generated at the same time as copper plating, and the reinforcing of the solder pad is realized without increasing the process steps, and the manufacturing is simple. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is a design principle diagram of the solder pad reinforcing structure (the dashed line in the figure represents the range of the blind hole); Figure 2 It is a partial sectional view of the PCB in Example 1; Figure 3 It is a partial sectional view of the PCB in Example 2; Figure 4 It is a partial sectional view of the PCB in Example 3; Figure 5 It is a partial sectional view of the PCB in Example 4; Figure 6 It is a partial sectional view of the PCB in Example 5.

[0022] The marks in the figure are: 1-PCB board, 11-outer dielectric layer, 12-pad, 13-reinforcement part, 14-circuit, 15-inner metal layer, 16-inner dielectric layer, 17-solder mask layer, 18-thread structure, 19-prefabricated tensile strength part. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to specific embodiments.

[0024] Example 1: like Figure 1 and Figure 2 As shown, a pad reinforcement structure includes a multi-layer PCB board 1. The PCB board includes an outer dielectric layer 11 and pads 12 disposed on the outer dielectric layer. Three reinforcing portions 13 are connected to the edges of the pads 12. The reinforcing portions 13 are made of the same material as the pads 12. Blind vias are provided in open areas around the pads 12 in the outer dielectric layer 11. The reinforcing portions 13 extend into the blind vias and do not make conductive connections with the circuitry 14 of the inner layers of the PCB board 1. In practical applications, the number of reinforcing portions 13 is not limited to three.

[0025] The pad reinforcement structure adds several integrally connected and blind-via embedded reinforcement parts 13 around the pad 12. Without causing a short circuit, the blind-via walls exert force on the reinforcement parts 13, thereby holding the edge of the pad 12 in place and preventing it from falling off the outer dielectric layer 11 during the SMT process, thus improving the product yield. The position of the reinforcement parts 13 can be freed from the limitations of the pad 12 area, allowing for flexible placement in open areas on the PCB board 1 and in appropriate numbers.

[0026] The manufacturing method of the circuit board including this pad reinforcement structure is as follows: S1. Drilling: Prepare a substrate with an outer dielectric layer 11, and perform drilling on the surface of the substrate. The drilling locations include blind holes at the designed locations of the reinforcing part 13, resulting in a drilled substrate. The drilling method here is laser drilling, and the drilling depth at the blind holes where the reinforcing part 13 is located is 100% of the depth of the outer dielectric layer 11. S2, Copper plating: First, chemically deposit copper on the surface of the substrate after drilling, and then electroplate copper on its surface to metallize all blind holes and make the copper layer cover the surface of the outer dielectric layer 11 to obtain a copper-plated board. S3. Pattern transfer: Photoresist is coated on the surface of the copper plated board, then exposed and developed to remove the uncured photoresist. The cured photoresist covers the design position of the pad 12 and the design position of the reinforcement part 13 to obtain the coated board. S4. Etching: Etching the copper surface not covered by photoresist to leave the design area of ​​line 14, pad 12 and reinforcement 13, to obtain an etched board; S5. Removal: Remove the cured photoresist to obtain PCB board 1.

[0027] The reinforcement 13 can be generated simultaneously with copper plating, reinforcing the pad 12 without adding process steps, simplifying manufacturing. Considering that the blind via containing the reinforcement 13 needs to avoid contact with the trace 14 to prevent short circuits, its diameter can be controlled using laser drilling. Although the PCB board 1 has an inner metal layer 15, the trace 14 on the inner metal layer 15 does not pass through this blind via. This pad reinforcement structure is suitable for products with densely packed traces 14.

[0028] Example 2: like Figure 3 As shown, the difference from Embodiment 1 is that the blind hole is a threaded hole, and the reinforcing part 13 fills the sidewall of the blind hole. The inner wall of the threaded hole is the threaded structure 18.

[0029] The manufacturing method of the circuit board including this pad reinforcement structure is as follows: S1. Drilling: Prepare a substrate with an outer dielectric layer 11, and perform drilling on the surface of the substrate. The drilling location includes blind holes at the designed location of the reinforcement part 13. The substrate after drilling is obtained. The drilling step adopts mechanical drilling method, leaving a thread structure on the surface of the blind hole where the reinforcement part 13 is located. S2, Copper plating: First, chemically deposit copper on the surface of the substrate after drilling, and then electroplate copper on its surface to metallize all blind holes and make the copper layer cover the surface of the outer dielectric layer 11 to obtain a copper-plated board. S3. Pattern transfer: Photoresist is coated on the surface of the copper plated board, then exposed and developed to remove the uncured photoresist. The cured photoresist covers the design position of the pad 12 and the design position of the reinforcement part 13 to obtain the coated board. S4. Etching: Etching the copper surface not covered by photoresist to leave the design area of ​​line 14, pad 12 and reinforcement 13, to obtain an etched board; S5. Removal: Remove the cured photoresist to obtain PCB board 1.

[0030] Compared to laser drilling, mechanical drilling produces slightly larger holes, making it more suitable for products with lower circuit density (14). After drilling blind holes, a threaded structure (18) is typically machined using a lead screw. After the blind hole is metallized, the threaded structure (18) creates an interlocking connection with the reinforcing part (13). Even with a shallow drilling depth, the outer dielectric layer (11) provides significant tensile strength to the reinforcing part (13), making the pads (12) more robust.

[0031] Example 3: like Figure 4 As shown, the difference from Embodiment 1 is that the PCB board 1 also includes several inner metal layers 15 and several inner dielectric layers 16 that are alternately stacked, and blind vias pass through one inner dielectric layer 16.

[0032] The manufacturing method of the circuit board containing the solder pad reinforcing structure is the same as that of Embodiment 1, except that the depth of the drilled hole is not limited by the thickness of the outer dielectric layer 11. The depth of the reinforcing portion 13 is increased, that is, the contact area between the outer dielectric layer 11 and the reinforcing portion 13 is increased, the difficulty of the reinforcing portion 13 being separated from the outer dielectric layer 11 is increased, and thus the solder pad 12 is more firmly fixed.

[0033] Embodiment 4: As shown in Figure 5 The difference from Embodiment 3 is that the inner metal layer 15 is provided with a pre-tensioning portion 19 at the position where the reinforcing portion 13 is located in the through hole. The pre-tensioning portion 19 is not in conductive connection with the inner layer circuit 14 of the PCB 1, and the pre-tensioning portion 19 is made of the same material as the reinforcing portion 13 and is integrated with the reinforcing portion 13.

[0034] Before preparing the substrate, the pre-tensioning portion 19 is reserved in the inner part of the outer dielectric layer 11, and the position of the pre-tensioning portion 19 covers the range of the blind hole where the reinforcing portion 13 is located. When drilling, the blind hole where the reinforcing portion 13 is located passes through the pre-tensioning portion 19. When plating copper, the metalization of the blind hole causes the reinforcing portion 13 to be integrated with the pre-tensioning portion 19.

[0035] The solder pad 12 and the reinforcing portion 13 are formed in the same step (copper plating), so the two parts are originally an integral whole, and the pre-tensioning portion 19 is made in advance during the manufacture of the inner layer circuit 14, which is different from the forming step of the former two. However, because the materials are the same, the reinforcing portion 13 can be well combined with the pre-tensioning portion 19 after being formed. The integral whole formed by the reinforcing portion 13 and the pre-tensioning portion 19 is similar to the concave-convex staggered connection relationship in Embodiment 2, but does not need to be mechanically processed, can control the aperture of the blind hole, and can have sufficient tensile effect.

[0036] Embodiment 5: As shown in Figure 6 The difference from Embodiment 1 is that the surface of the PCB 1 is further provided with a solder mask layer 17, and the solder mask layer 17 is windowed at the position of the solder pad 12 and covers the reinforcing portion 13.

[0037] The manufacturing method of the circuit board containing the solder pad reinforcing structure is as follows: S1, drilling: preparing a substrate with an outer dielectric layer 11, drilling on the surface of the substrate, the position of the drilled hole including the blind hole at the design position of the reinforcing portion 13, obtaining the drilled substrate, the drilling method here is laser drilling, and the drilling depth at the blind hole where the reinforcing portion 13 is located is 60% of the depth of the outer dielectric layer 11; S2, copper plating: first, chemical copper deposition on the surface of the substrate after drilling, then electroplating copper on the surface, metalize all blind holes, and make the copper layer cover the surface of the outer dielectric layer 11, to obtain a copper plated board; S3, pattern transfer: coating photoresist on the surface of the copper plated board, then exposing and developing, removing the uncured photoresist, and the cured photoresist covering the design position of the solder pad 12 and the design position of the reinforcing part 13, to obtain a photoresist coated board; S4, etching: etching the copper surface not covered by the photoresist, leaving the design area of the circuit 14, the solder pad 12 and the reinforcing part 13, to obtain an etched board; S5, film removal: removing the cured photoresist; S6, surface solder resist: covering the solder resist ink on the surface of the PCB board 1, and windowing the solder resist ink including the position of the solder pad 12, and the cured solder resist ink forming a solder resist layer 17 covering the reinforcing part 13, to obtain the PCB board 1.

[0038] The inherent function of the solder resist layer 17 is to prevent the tin paste from flowing out of the range of the solder pad 12, and to avoid short circuiting of the adjacent circuit 14. When used here, the solder resist layer 17 will also cover the top of the reinforcing part 13, thereby providing the reinforcing part 13 with resistance to tension. As a result, the force directly applied by the outer dielectric layer 11 to the reinforcing part 13 can be reduced, and thus the depth of the reinforcing part 13 can be appropriately reduced.

[0039] The above only describes some embodiments of the present application. For those skilled in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are all within the scope of protection of the present application.

Claims

1. A pad reinforcement structure, comprising a multilayer PCB board, the PCB board including an outer dielectric layer and pads disposed on the outer dielectric layer, characterized in that: The edge of the pad is connected to multiple reinforcing parts, which are made of the same material as the pad. The outer dielectric layer has blind holes in an open area around the pad. The reinforcing parts extend into the blind holes and do not make conductive connections with the circuitry of the inner layer of the PCB board.

2. The pad reinforcement structure according to claim 1, characterized in that: The blind hole is a screw hole, and the reinforcing part fills the sidewall of the blind hole.

3. The pad reinforcement structure according to claim 1, characterized in that: The PCB board also includes several alternating inner metal layers and several inner dielectric layers, and the blind vias pass through at least one inner dielectric layer.

4. The pad reinforcement structure according to claim 3, characterized in that: The inner metal layer has a prefabricated tensile strength portion at the location where the blind hole of the reinforcement part passes through. The prefabricated tensile strength portion is not electrically connected to the circuit of the inner layer of the PCB board. The prefabricated tensile strength portion is made of the same material as the reinforcement part and is integrated with it.

5. The pad reinforcement structure according to claim 1, characterized in that: The PCB board surface is also provided with a solder resist layer, which has windows at the location of the solder pads and covers the reinforcement part.

6. A circuit board manufacturing process for manufacturing a PCB board having any of the pad reinforcement structures of claims 1-5, characterized in that... The steps include: S1. Drilling: Prepare a substrate with an outer dielectric layer, and perform drilling on the surface of the substrate. The drilling location includes blind holes at the design location of the reinforcement part, and obtain a substrate after drilling. S2, Copper plating: First, chemically deposit copper on the surface of the substrate after drilling, and then electroplate copper on its surface to metallize all blind holes and make the copper layer cover the surface of the outer dielectric layer to obtain a copper-plated board. S3. Pattern Transfer: Photoresist is coated on the surface of the copper plate, then exposed and developed to remove the uncured photoresist. The cured photoresist covers the design positions of the pads and the design positions of the reinforcement to obtain a coated plate. S4. Etching: Etching the copper surface not covered by photoresist to leave the design area of ​​the circuit, pads and reinforcement, resulting in an etched board; S5. Removal: Remove the cured photoresist to obtain the PCB board.

7. The circuit board manufacturing process according to claim 6, characterized in that: The drilling step employs laser drilling, and the drilling depth at the blind hole where the reinforcement part is located is 60%-100% of the depth of the outer medium layer.

8. The circuit board manufacturing process according to claim 6, characterized in that: The drilling step employs mechanical drilling, leaving a threaded structure on the surface of the blind hole where the reinforcement part is located.

9. The circuit board manufacturing process according to claim 6, characterized in that: Before preparing the substrate, a pre-fabricated tensile strength portion is reserved inside the outer dielectric layer. The position of the pre-fabricated tensile strength portion covers the range of the blind hole where the reinforcement portion is located. When drilling, the blind hole where the reinforcement portion is located passes through the pre-fabricated tensile strength portion. When copper plating, the metallization of the blind hole makes the reinforcement portion generated and the pre-fabricated tensile strength portion merge into a whole.

10. The circuit board manufacturing process according to claim 6, characterized in that: It also includes surface solder resist, the method of which is to cover the surface of the PCB board with solder resist ink, open the solder resist ink including the location of the solder pads, and the cured solder resist ink forms a solder resist layer covering the reinforcement.

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