PCB (Printed Circuit Board) substrate with bottom copper gold-plated blind groove
By designing a composite structure of laminated resin and bottom copper gold plating in the blind groove area from the surface recessed blind groove area on the PCB substrate, the problem of poor bottom copper gold plating in the traditional blind groove process is solved, and stability and insulation in high temperature and high humidity environment are achieved.
Patent Information
- Application Number
- CN202422408890.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-30
- Publication Date
- 2025-07-25
- Estimated Expiration
- 2034-09-30
AI Technical Summary
In the prior art, the traditional blind groove process cannot meet the requirements of copper gold plating at the bottom of the blind groove, resulting in the PCB substrate being prone to failure in high temperature and high humidity environment.
The laminated resin with a blind groove area of the self-depressed surface is adopted. The side wall of the blind groove area is exposed with the resin material, the bottom copper and the bottom gold-plated composite structure, the bottom gold-plated top surface is flush with the notch, and the expansion part is embedded inside the resin, so that the blind groove depth and gold-plated thickness are reasonably planned.
It ensures that the PCB substrate is not prone to failure in high temperature and high humidity environments. The bottom copper provides sufficient gold plating area and a stable gold plating area, which improves the gold plating effect and insulation.
Smart Images
Figure CN223157303U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of printed circuit boards, and particularly to a PCB substrate with a blind via having a bottom copper and gold plating. Background Art
[0002] With the requirements of high-speed communication, during the packaging process, it is necessary to embed the chip into the substrate. Therefore, during the substrate processing, it is necessary to open blind vias and perform gold plating on the bottom of the blind vias. This method is called the blind via process (or Cavity process). The processing flow of the bottom copper and gold plating of the blind via is as follows: pattern formation, solder mask, blind via process, gold plating (nickel-gold or nickel-palladium-gold).
[0003] The traditional blind via machining after the solder mask cannot meet the requirements of the bottom copper and gold plating of the blind via bottom, while laser machining (or laser processing) can meet the requirements of the bottom copper and gold plating. Figure 3 It is a schematic structural diagram of the bottom copper and gold plating. Figure 3 The gold plating area 5 in [reference] mainly includes two parts. One part is the bottom surface gold 51 located on the bottom surface of the blind via. In addition, if the gold plating effect is not good and the gold plating area is not accurate, the PCB substrate may fail in a high-temperature and high-humidity environment. Summary of the Utility Model
[0004] In view of the state of the above-mentioned prior art, this application is made. The purpose of this application is to provide a PCB substrate with a blind via having a bottom copper and gold plating.
[0005] The technical solution adopted by this application to solve its technical problems includes: a PCB substrate with a blind via having a bottom copper and gold plating, including: a laminated resin, the laminated resin has a blind via area recessed from its surface, and the side walls of the blind via area expose the material of the laminated resin; dry ink, at least part of the area of the front surface of the laminated resin except the blind via area is covered with the dry ink; bottom copper, the bottom of the blind via area is provided with the bottom copper; bottom gold plating, the upper surface of the bottom copper has a top surface groove, and the top surface groove is filled with the bottom gold plating, and the top surface of the bottom gold plating is flush with the opening surface of the top surface groove.
[0006] As a further improvement of this application, when observing along the depth direction of the blind via area, the bottom surface area of the blind via area is equal to the top surface area of the bottom gold plating, the top surface area of the bottom copper is greater than the top surface area of the bottom gold plating, and the bottom copper has an expansion part inserted into the laminated resin.
[0007] As a further improvement of this application, the depth value of the blind via area is greater than half of the thickness value of the laminated resin.
[0008] As a further improvement of this application, the depth value of the blind via area is less than the width value of the blind via area.
[0009] As a further improvement of the present application, the thickness value of the bottom gold plating is less than half of the thickness value of the bottom copper.
[0010] As a further improvement of the present application, the front surface of the bonding layer resin around the opening of the blind groove area further has an exposed area not covered by the dry ink.
[0011] As a further improvement of the present application, the expansion dimension of the expansion part in the width direction of the blind groove area is greater than the dimension of the exposed area in the width direction of the blind groove area.
[0012] The beneficial effects of the PCB substrate with a bottom copper and gold-plated blind groove of the present application include: the side wall of the blind groove area is the original material of the bonding layer resin, only the bottom of the blind groove area is made of gold-plated material for conduction, while the resin on the side wall of the blind groove area is non-conductive, which ensures the insulation of the PCB product in this specified direction and is not easily damaged in a high-temperature and high-humidity environment. In addition, the bottom of the blind groove area is in the composite form of "gold on top and copper at the bottom". The bottom copper provides sufficient gold-plating area, sufficient gold-plating thickness, and a stable gold-plating area for the bottom gold plating, ensuring that only the bottom of the blind groove area has gold plating and the gold-plating effect is good. Brief Description of the Drawings
[0013] In order to more clearly illustrate the technical solutions in the embodiments, the drawings of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.
[0014] Figure 1 It is a schematic structural diagram of an embodiment of the PCB substrate with a bottom copper and gold-plated blind groove of the present application;
[0015] Figure 2 It is a process flow diagram of an embodiment of the PCB substrate with a bottom copper and gold-plated blind groove of the present application;
[0016] Figure 3 It is a schematic structural diagram of a bottom copper and gold plating;
[0017] Figure 4 It is a microscopic view of the cross section of the blind groove area after laser treatment in an embodiment of the PCB substrate with a bottom copper and gold-plated blind groove of the present application;
[0018] Figure 5 It is a microscopic view of the cross section of the blind groove area after preliminary cleaning, middle-stage cleaning, and final cleaning in an embodiment of the PCB substrate with a bottom copper and gold-plated blind groove of the present application;
[0019] Figure 6It is a photograph of the blind via area of an embodiment of the PCB substrate with bottom copper and gold-plated blind vias of the present application;
[0020] Figure 7 It is a micrograph of a slice of the blind via area of an embodiment of the PCB substrate with bottom copper and gold-plated blind vias of the present application;
[0021] Figure 8 It is a process problem diagram in the field of PCB board processing;
[0022] Figure 9 It is a process flow diagram of an embodiment of the preparation method of the PCB substrate with bottom copper and gold-plated blind vias of the present application;
[0023] Figure 10 It is a schematic structural diagram of an embodiment of the PCB substrate with bottom copper and gold-plated blind vias of the present application;
[0024] Figure 11 It is a micrograph of the blind via area of an embodiment of the PCB substrate with bottom copper and gold-plated blind vias of the present application;
[0025] Figure 12 It is a micrograph of the blind via area of an embodiment of the PCB substrate with bottom copper and gold-plated blind vias of the present application.
[0026] Description of Reference Numerals
[0027] 1 - Dry ink; 2 - Laminating resin; 21 - Exposure area; 22 - Blind via area; 3 - Bottom copper; 31 - Expansion part; 32 - Top surface groove; 4 - Bottom gold plating; 5 - Existing gold-plated area; 51 - Bottom surface gold; 6 - Laser; 7 - Charged gas; 9 - Pad; 11 - Vacuum dust collector; 12 - Vaporized resin; 13 - Liquefied resin; C - Side elevation area; D - Bottom plane area; θ - Side wall bottom corner angle; Z - Total depth of blind via; L1 - Protrusion distance at the bottom of blind via; L2 - Distance from the top of blind via to pad; L3 - Distance from the bottom of blind via to pad. Detailed Embodiments
[0028] The following describes exemplary embodiments of the present application with reference to the accompanying drawings. It should be understood that these specific descriptions are only used to teach those skilled in the art how to implement the present application, rather than to exhaust all possible ways of the present application, nor to limit the scope of the present application.
[0029] As Figure 1 shown, an embodiment of the present application provides a PCB substrate with bottom copper and gold-plated blind vias. The main body of the PCB substrate includes a laminating resin 2, and also includes dry ink 1, bottom copper 3, and bottom gold plating 4. Among them, the top surface of the laminating resin 2 is recessed with a blind via area 22, and the front surface of the laminating resin 2 ( Figure 1The upper surface (except for the blind groove area 22) is at least partially covered with dry ink 1. The bottom copper 3 is located at the bottom of the blind groove area 22. Refer to Figure 1 and Figure 3 , the top surface of the bottom copper 3 has a top surface groove 32, and the top surface groove 32 is filled with bottom gold plating 4. The top surface of the bottom gold plating 4 is flush with the opening surface of the top surface groove 32 (i.e., the top surface of the peripheral wall of the bottom copper 3 that defines the opening of the top groove 32). Finally, the bottom surface of the entire blind groove area 22 is covered with gold, but the side walls of the blind groove area 22 expose the material of the bonding resin 2 itself.
[0030] In another embodiment, when observing along the depth direction of the blind groove area 22, the bottom surface area of the blind groove area 22 is equal to the top surface area of the bottom gold plating 4, and the top surface area of the bottom copper 3 is greater than the top surface area of the bottom gold plating 4. In the cross-section cut along the depth direction, the bottom copper 3 has an expansion part 31 (edge) inserted into the bonding resin 2.
[0031] The beneficial effects of adopting the above embodiment are as follows: ensuring that the area of the bottom copper 3 is large enough. First, the expansion part 31 is embedded in the bonding resin 2, so the assembly is firm; second, it can also ensure that there is enough area to occupy the bottom of the blind groove area 22, and then be covered by the bottom gold plating 4, and the relative position accuracy requirements for the bottom copper 3 are not high.
[0032] In another embodiment, the depth value of the blind groove area 22 is greater than half of the thickness value of the bonding resin 2. The depth value of the blind groove area 22 is less than the width value of the blind groove area 22. The thickness value of the bottom gold plating 4 is less than half of the thickness value of the bottom copper 3.
[0033] The beneficial effects of adopting the above embodiment are as follows: reasonably planning the depth of the blind groove area 22 and the thickness of the bottom gold plating 4.
[0034] In another embodiment, the front surface of the bonding resin 2 around the opening of the blind groove area 22 also has an exposed area 21 that is not covered by the dry ink 1. The expansion size of the expansion part 31 in the width direction of the blind groove area 22 (i.e., the size inserted into the bonding resin 2) is greater than the size of the exposed area 21 in the width direction of the blind groove area 22.
[0035] In another embodiment, as Figure 10 shown, there is also a layer of solder pad 9 provided between the dry ink 1 and the bonding resin 2. There is bonding resin 2 around the opening of the blind groove area 22 that is not covered by the solder pad 9, and the upper surface of the bonding resin 2 is partially exposed here; there is also solder pad 9 around the opening of the blind groove area 22 that is not covered by the dry ink 1, and the upper surface of the solder pad 9 is partially exposed here. That is, at the position of the blind groove area 22, the opening areas of the bonding resin 2, the solder pad 9, and the dry ink 1 are getting larger and larger.
[0036] As Figures 10 to 12As shown, first, from the opening to the bottom surface of the blind groove area 22, the width of the blind groove area 22 gradually decreases. The included angle range at the junction of the side wall of the blind groove area 22 and the bottom surface of the blind groove area 22 is from 90° to 110°, that is, the side wall bottom angle θ satisfies the range of 80° to 90°. The included angle at the junction of the side wall of the blind groove area 22 and the bottom surface of the blind groove area 22 is supplementary to the side wall bottom angle θ. In the actual preparation method, the process capability index (Cpk) of the side wall bottom angle θ is equal to 1.21. Cpk is a key index to measure process stability. The higher the Cpk value, the more stable the process and the smaller the fluctuation of product quality. Here, Cpk being equal to 1.21 means that the overall actual processing quality meets the design requirements. Secondly, the lateral dimension from the opening edge of the bonding resin 2 corresponding to the opening of the blind groove area 22 to the bottom edge of the blind groove area 22 is not greater than 2 mil. The distance L2 from the blind groove top to the pad is not greater than 2 mil. The mil is also known as a milliinch, which is a unit of length. 1 mil is equal to 25.4 um. The distance L3 from the blind groove bottom to the pad is not greater than 50.8 um. Thirdly, the lateral dimension of the opening edge of the pad 9 corresponding to the opening of the blind groove area 22 is not greater than 4 mil larger than the bottom edge of the blind groove area 22. That is, the distance L3 from the blind groove bottom to the pad is not greater than 4 mil, which means the distance L3 from the blind groove bottom to the pad is not greater than 101.6 um. The actual Cpk of the distance L3 from the blind groove bottom to the pad is greater than 1.33, indicating that the qualified rate of this process is very high. The lateral distance that the bottom side of the blind groove area 22 extends forward towards the center of the blind groove area 22 compared to the opening edge side of the blind groove area 22 is the blind groove bottom protrusion distance L1. The distance L3 from the blind groove bottom to the pad is equal to the sum of the blind groove bottom protrusion distance L1 and the distance L2 from the blind groove top to the pad. The size values of the blind groove bottom protrusion distance L1, the distance L2 from the blind groove top to the pad, and the distance L3 from the blind groove bottom to the pad are all size values measured along the depth direction perpendicular to the blind groove area 22. Finally, the vertical distance from the bottom surface of the blind groove area 22 to the top surface of the dry ink 1 is the total blind groove depth Z. In a non - restrictive embodiment, the value of the total blind groove depth Z is 0.429 mm.
[0037] Figure 11 and Figure 12 are electron microscope images, respectively showing the position indicated by the actual side wall bottom angle θ and the position indicated by the blind groove bottom protrusion distance L1.
[0038] In a non - restrictive embodiment, the actually sampled side wall bottom angle θ satisfies the range of 80° to 90°, with an average value of 85.93°. The average value of the blind groove bottom protrusion distance L1 is 26.72 um, the average value of the distance L2 from the blind groove top to the pad is 18.54 um, and the average value of the distance L3 from the blind groove bottom to the pad is 45.26 um. The specific data is shown in the following table:
[0039] θ (unit: °) L1 (unit: um) L2 (unit: um) L3 (unit: um) Average value 85.93 26.72 18.54 45.26 Standard deviation 1.12 4.57 5.80 6.71 Maximum value 87.81 35.62 24.91 57.61 Minimum value 83.62 19.79 7.48 35.62
[0040] As Figure 2 shown, the manufacturing process flow of the PCB substrate with bottom copper and gold-plated blind vias of the present application successively includes, for example: pattern formation, solder mask, laser grooving, cleaning treatment (i.e., preliminary cleaning), enhanced cleaning treatment (i.e., middle-section cleaning), cleaning treatment (i.e., terminal cleaning), and gold plating. Figure 2 The four modules in are, in the order of the arrow, the laser treatment of the blind via (i.e., laser grooving), the enhanced cleaning treatment for strong dirt removal, the cleaning treatment, and gold plating.
[0041] After the solder mask, the blind via process is carried out. Through the enhanced cleaning treatment and two cleaning treatments, the dirt after laser grooving is removed, reducing the impact of excessive dirt on electroplating, avoiding gold plating on the side walls of the blind via area 22, and reducing the risk of short-circuit failure at high temperature and high humidity after packaging. In addition, the formation of the solder mask in the process flow is relatively easy. At this time, the blind via process has not been carried out, and the surface of the bonding resin 2 has no deep depression and is relatively flat as a whole. Whether it is wet ink or dry ink after the solder mask, there are no wrinkles, and there is no residual ink impact. The laser grooving is significantly superior to the boring machine in terms of the control accuracy of length, width, and depth. The role of the enhanced cleaning treatment is to strongly remove the dirt after the blind via process. The role of the cleaning treatment is to use its water washing ability to remove the remaining dirt. The cleaning treatment is carried out twice before and after to ensure the removal of the dirt on the side walls of the blind via area 22, thereby reducing the probability of side wall gold plating.
[0042] Compare Figure 4 and Figure 5 , Figure 4 is the cross-section of the blind via after laser grooving, Figure 5 is the cross-section state of the blind via after the enhanced cleaning treatment and the cleaning treatment after the blind via process. Figure 4 shows the covered fluffy dust layer, while Figure 5 removes the fluffy dust layer, and the neat tubular objects exposed are the glass fibers contained in the bonding resin 2.
[0043] The finished product effect of the PCB substrate with bottom copper and gold-plated blind vias in the embodiment of the present application is as Figure 6 shown, Figure 6 the upper part (left side of the paper surface) of is the state without gold on the side walls, Figure 6 the lower part of is gold plating at the bottom, that is, the state of the bottom gold surface. Figure 6 It can be clearly seen that the side walls of the blind via area 22 do not contain gold (i.e., Figure 6 the bottom plane area D in contains gold, and the side elevation area C does not contain gold). At the same time, as Figure 7 shown, Figure 7 is a slice of the blind via area 22 after electroless nickel electroless palladium immersion gold (abbreviated as ENEPIG).Figure 7 Confirm the squareness of the side wall of the blind groove area 22 from the side (i.e., pay attention to Figure 7 the vertical degree of the connection line of the edges on one side of the layered dark gray blocks in it), and the state of the copper layer at the bottom of the blind groove area 22 (i.e., Figure 7 the continuous bright gray blocks on the left and right at the bottom of the figure in it Figure 7 on the left and right). And Figure 7 the "gentle slope" contour in the upper left of the figure, and the object corresponding to its lower part is the filler for slicing, which is used to ensure the fixed state of the interface and no abnormal damage caused by grinding.
[0044] Figure 8 Shown is a process problem diagram for processing in the field of PCB boards. When the laser 6 processes the resin, the vacuum dust collector 11 will suck the dust near the laser 6 processing area, but subsequently, palladium ions (Pd 2+ ) are also likely to be adsorbed on the side walls of the pits on the resin.
[0045] Step S1, laser processing: Refer to Figure 9 State four in the figure, use the laser 6 on the PCB board to process specific grooves or holes to meet the electrical connection requirements; Step S2, cleaning treatment (i.e., preliminary cleaning): Remove the dirt generated during laser processing; Step S3, enhanced cleaning treatment (i.e., mid-section cleaning): Refer to Figure 9 State five in the figure, use the charged gas 7 to perform surface modification on the blind groove area 22 (or called Cavity) after laser processing; Step S4, second cleaning treatment (i.e., terminal cleaning): Refer to Figure 9 State six in the figure, perform water washing and cleaning on the blind groove area 22 after being treated with the charged gas 7, remove the residues on the PCB board, and ensure that the board surface is clean and free of impurities; Step S5, refer to Figure 9 State seven in the figure, gold plating: Gold plate the bottom copper 3.
[0046] In a non-limiting example, the laser 6 can be a high-speed laser, with a small aperture, low thermal effect, and fast processing speed; in addition, the charged gas 7 can be a negatively charged gas, with strong dirt removal ability, high removal efficiency, and fast speed.
[0047] Cleaning treatment, that is, terminal cleaning, removes foreign objects on the substrate surface. During the water washing and cleaning process, the water pressure for terminal cleaning is not less than 0.6 MPa. The PCB board is contacted and transported in a three-point manner. In a non-limiting embodiment, the handling mechanism can use three suction cup heads to adsorb and contact the PCB board, thereby reducing the probability of the PCB board being scratched.
[0048] Before step S1, there can also be a pre-step. The pre-step includes: Pre-step S01, image formation: Form a circuit pattern on the PCB board. Pre-step S02, solder resist: Refer toFigure 9 In state one, a solder mask ink is coated on the PCB board to form a dry ink 1 to protect the parts that do not need to be soldered.
[0049] The gold plating in step S5 can also be pre-treatment and nickel-palladium-gold plating; Step S501, pre-treatment: Chemically corrode the bottom copper 3 to remove the oxides, stains and uneven parts on the surface copper layer of the bottom copper 3, so as to ensure the adhesion. Step S502, nickel-palladium-gold plating: First, deposit a layer of nickel on the surface of the bottom copper 3 as an intermediate layer. Then deposit a layer of palladium to prevent the diffusion of nickel and ensure the stability of the coating. Finally, deposit a layer of gold to improve the corrosion resistance and solderability of the PCB board.
[0050] An inspection step can also be included after step S5. Refer to Figure 9 In state eight, the inspection step is to use a microscope and visual inspection respectively. The actual states of defective products during the processing are shown by photos and microscope images respectively. The typical characteristics of defective products are made into a kanban or process instruction manual to facilitate the comparison between the inspectors and the actual finished products one by one.
[0051] The above embodiments are only used to illustrate the technical concept and features of the present application, and their purpose is to enable those who are familiar with this technology to understand the content of the present application and implement it. It cannot be used to limit the protection scope of the present application. Any equivalent changes or modifications made according to the spirit of the present application should be covered within the protection scope of the present application.
Claims
1. A PCB substrate with a bottom copper-gilded blind via, characterized in that, Comprising: A pasting resin, the pasting resin having a blind groove area recessed from its surface, and the side wall of the blind groove area exposing the material of the pasting resin; Dry ink, at least a part of the area of the front surface of the pasting resin except the blind groove area being covered with the dry ink; Bottom copper, the bottom of the blind groove area being provided with the bottom copper; Bottom gold plating, the upper surface of the bottom copper having a top surface groove, and the top surface groove being filled with the bottom gold plating, the top surface of the bottom gold plating being flush with the opening surface of the top surface groove.
2. The PCB substrate with a bottom copper gold-plated blind via according to claim 1, wherein: Viewed along the depth direction of the blind groove area, the bottom surface area of the blind groove area is equal to the top surface area of the bottom gold plating, the top surface area of the bottom copper is greater than the top surface area of the bottom gold plating, and the bottom copper has an expansion part inserted into the interior of the pasting resin.
3. The PCB substrate with a bottom copper gold-plated blind via according to claim 1, characterized in that: The depth value of the blind groove area is greater than half of the thickness value of the pasting resin.
4. The PCB substrate with a bottom copper gold-plated blind via according to claim 1, characterized in that: The depth value of the blind groove area is less than the width value of the blind groove area.
5. The PCB substrate with bottom copper gold-plated blind vias according to claim 1, characterized in that: The thickness value of the bottom gold plating is less than half of the thickness value of the bottom copper.
6. The PCB substrate with a bottom copper gold-plated blind via according to claim 2, characterized in that: The front surface of the pasting resin around the opening of the blind groove area further has an exposed area not covered by the dry ink.
7. The PCB substrate with a bottom copper gold-plated blind via according to claim 6, characterized in that: The expansion dimension of the expansion part in the width direction of the blind groove area is greater than the dimension of the exposed area in the width direction of the blind groove area.