Structure of step plate

Abstract

The utility model relates to a structure of a stepped plate. The structure comprises a first substrate, a first copper sheet, a second copper sheet, a top solder mask, a first PP plate, a light plate, a second PP plate, a third copper sheet, a second substrate, a fourth copper sheet and a bottom solder mask. The middle parts of the first PP plate, the light plate and the second PP plate are respectively provided with a first PP window, a light plate window and a second PP window; and a second copper sheet uncovering area, a first substrate uncovering area, a first copper sheet uncovering area and a top solder mask uncovering area are respectively arranged above the first PP window. The middle part of the third copper sheet is provided with a circuit wire and a bonding pad, and the circuit wire and the bonding pad are provided with a middle-layer solder mask. And filling mechanisms are arranged in the first PP window, the light plate window and the second PP window. According to the scheme, resistance welding is carried out on the inner-layer circuit, the inner-layer resistance welding is exposed on the surface of the outer layer after a finished product is obtained, the inner-layer circuit and resistance welding ink cannot be damaged when the outer layer is uncovered in the production process, the quality of the step plate is guaranteed, the production qualification rate is high, and the large-batch production requirement can be met.

Description

Technical Field

[0001] The utility model relates to the technical field of PCB board production, in particular to a structure of a stepped board. Background Art

[0002] With the rapid development of the PCB board industry, the application range of PCB boards (i.e., circuit boards) is becoming more and more extensive, and the production complexity of circuit boards is also increasing continuously. For example, for rigid stepped type circuit boards (i.e., stepped boards), in order to meet the design requirements of customers, solder mask is applied on the inner layer circuit. After the product is finished, the inner layer solder mask needs to be exposed on the outer layer surface, and the inner layer SMD (pad) needs to be treated with immersion gold. How to avoid damaging the inner layer circuit and solder mask ink when uncovering the outer layer has become the focus of the industry.

[0003] The existing production method of ordinary rigid multi-layer boards cannot uncover the outer layer to expose the inner layer pattern and inner layer surface treatment. It is necessary to develop new process flows and PCB board structures to complete the operation of rigid stepped type circuit boards.

[0004] To solve this new problem, this solution proposes a structure of a stepped board. Content of the Utility Model

[0005] The invention purpose of the utility model is to solve the technical problem that the existing production method of ordinary rigid multi-layer boards cannot uncover the outer layer to expose the inner layer pattern and inner layer surface treatment. The specific solution is as follows:

[0006] The structure of a stepped board includes a first substrate, a first copper foil disposed on the upper side of the first substrate, a second copper foil disposed on the lower side of the first substrate, a top solder mask disposed on the upper side of the first copper foil, a first PP board disposed on the lower side of the second copper foil, a bare board disposed on the lower side of the first PP board, a second PP board disposed on the lower side of the bare board, a third copper foil disposed on the lower side of the second PP board, a second substrate disposed on the lower side of the third copper foil, a fourth copper foil disposed on the lower side of the second substrate, and a bottom solder mask disposed on the lower side of the fourth copper foil. First PP openings, bare board openings, and second PP openings are respectively provided in the middle parts of the first PP board, the bare board, and the second PP board. The first PP opening and the second PP opening are equal in size, and the bare board opening is smaller than the first PP opening and the second PP opening. In the middle parts of the second copper foil, the first substrate, the first copper foil, and the top solder mask above the first PP opening, there are respectively second copper foil uncovering areas, first substrate uncovering areas, first copper foil uncovering areas, and top solder mask uncovering areas that are equal in size. A circuit trace and pads are provided in the middle part of the third copper foil, and a middle solder mask is provided on the circuit trace and the pads. A pad opening is provided on the surface of the pads, and the middle solder mask is larger than the second PP opening. A filling mechanism is provided inside the first PP opening, the bare board opening, and the second PP opening. A second conductive mechanism is provided between the third copper foil, the second substrate, and the fourth copper foil. A first conductive mechanism is provided between the first copper foil, the first substrate, the second copper foil, the first PP board, the bare board, the second PP board, the third copper foil, the second substrate, and the fourth copper foil.

[0007] Further, the perimeter of the bare board opening is reduced inward by 0.5 mm compared to the perimeters of the first PP opening and the second PP opening.

[0008] Further, the perimeter of the middle solder mask is expanded outward by 0.5 mm compared to the perimeter of the second PP opening.

[0009] Further, the perimeters of the second copper foil uncovering area, the first substrate uncovering area, the first copper foil uncovering area, and the top solder mask uncovering area are expanded outward by  0.1 mm compared to the perimeter of the bare board opening.

[0010] Further, the perimeter of the filling mechanism is reduced inward by 0.5 mm compared to the perimeter of the bare board opening.

[0011] Further, the filling mechanism includes a backing plate in the middle, a first high-temperature tape disposed on the upper side of the backing plate, and a second high-temperature tape disposed on the lower side of the backing plate.

[0012] Further, the first copper foil, the first substrate, and the second copper foil are combined into one double-sided board, and the third copper foil, the second substrate, and the fourth copper foil are combined into another double-sided board.

[0013] Furthermore, the thickness of the second substrate is greater than that of the first substrate, and the thickness of the light plate is less than that of the first substrate.

[0014] Furthermore, both the first conductive mechanism and the second conductive mechanism are copper-plated vias.

[0015] Alternative Option 1: The middle solder mask, the first PP opening window, the light plate opening window, the second PP opening window, the second copper foil uncovering area, the first substrate uncovering area, the first copper foil uncovering area, and the top solder mask uncovering area are all rectangles with rounded corners.

[0016] Or Alternative Option 2: The middle solder mask, the first PP opening window, the light plate opening window, the second PP opening window, the second copper foil uncovering area, the first substrate uncovering area, the first copper foil uncovering area, and the top solder mask uncovering area are all ellipses.

[0017] In summary, adopting the technical solution of the present utility model has the following beneficial effects:

[0018] A structure of a stepped board proposed in this solution solves the customer's design requirements. Solder mask is applied on the inner layer circuit. After the product is finished, the inner layer solder mask needs to be exposed on the outer layer surface, and the inner layer SMD (pad) needs to be gold-plated. During the production process, the outer layer cover can be removed without damaging the inner layer circuit and solder mask ink. The quality of the stepped board is guaranteed, and the production qualification rate is high, which can meet the requirements of mass production and increase the company's order quantity. In this solution, a bare board is provided between two double-sided boards stacked up and down. A bare board opening is provided in the middle of the bare board, and a first PP board and a second PP board with middle openings are provided on the upper and lower sides of the bare board. A filling mechanism with a border smaller than that of the bare board opening is provided inside the bare board opening, the first PP board opening, and the second PP board opening. Above the bare board opening and the first PP board opening, an accurate cover removal area is set for the upper double-sided board, and the border of the cover removal area is expanded 0.1 mm outward compared with the border of the bare board opening. When the two double-sided boards and the middle bare board are pressed together through the first PP board and the second PP board, after the first conductive mechanism is processed between the two double-sided boards, the bare board, the first PP board, and the second PP board, the top and bottom surfaces of the pressed board are processed for wiring and pads, and then the top and bottom surfaces of the pressed board are processed for the solder mask layer. Finally, the cover removal area of the upper double-sided board is removed by routing. During routing, the routing depth is strictly controlled to finally complete the cover removal processing of the upper double-sided board. Since the filling mechanism of this solution has a backing plate with a first high-temperature tape and a second high-temperature tape attached to its upper and lower sides respectively, when the two double-sided boards, the middle bare board, the first PP board, and the second PP board are subjected to high-temperature pressing, the first PP board and the second PP board will not overflow into the bare board opening and stick to the backing plate at high temperature, nor will there be adhesion between the filling mechanism and the middle layer solder mask or the second copper foil. This solution, through the careful design of the opening size and the cover removal area size, and strictly controlling the depth when routing the cover removal area board, ensures that the inner layer circuit and solder mask ink will not be damaged during cover removal and improves the qualification rate of the stepped board. Brief Description of the Drawings

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings in the following description are only a part of the embodiments of the present invention, and those of ordinary skill in the art can also obtain other drawings based on these drawings without creative efforts.

[0020] Figure 1 It is a schematic cross-sectional structure diagram of a stepped board of the present invention;

[0021] Figure 2 It is a schematic diagram after the cover of a stepped board of the present invention is removed;

[0022] Figure 3 It is a schematic diagram after the cover of a stepped board of the present invention is removed for the panel.

[0023] Description of reference numerals:

[0024] 10-first substrate, 101-first substrate uncovering area, 11-first copper foil, 111-first copper foil uncovering area, 12-second copper foil, 121-second copper foil uncovering area, 13-top solder resist, 131-top solder resist uncovering area, 14-SMD pad, 20-bare board, 201-bare board window, 21-first PP board, 211-first PP window, 22-second PP board, 221-second PP window, 30-second substrate, 31-third copper foil, 311-circuit trace, 312-pad, 32-fourth copper foil, 33-bottom solder resist, 34-middle solder resist, 35-first conductive mechanism, 36-second conductive mechanism, 40-filling mechanism, 41-first high-temperature tape, 42-second high-temperature tape, 43-pad. DETAILED DESCRIPTION

[0025] The following will be combined with the accompanying drawings of the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0026] like Figure 1 、 2, as shown in FIGS. 3, a structure of a stepped board includes a first substrate 10, a first copper foil 11 disposed on the upper side of the first substrate 10, a second copper foil 12 disposed on the lower side of the first substrate 10, a top solder mask 13 disposed on the upper side of the first copper foil 11, a first PP board 21 disposed on the lower side of the second copper foil 12, a bare board 20 disposed on the lower side of the first PP board 21, a second PP board 22 disposed on the lower side of the bare board 20, a third copper foil 31 disposed on the lower side of the second PP board 22, a second substrate 30 disposed on the lower side of the third copper foil 31, a fourth copper foil 32 disposed on the lower side of the second substrate 30, and a bottom solder mask 33 disposed on the lower side of the fourth copper foil 32. First PP openings 211, bare board openings 201, and second PP openings 221 are respectively provided in the middle parts of the first PP board 21, the bare board 20, and the second PP board 22. The sizes of the first PP opening 211 and the second PP opening 221 are equal, and the bare board opening 201 is smaller than the first PP opening 211 and the second PP opening 221. In the middle parts of the second copper foil 12, the first substrate 10, the first copper foil 11, and the top solder mask 13 above the first PP opening 211, second copper foil uncovering areas 121, first substrate uncovering areas 101, first copper foil uncovering areas 111, and top solder mask uncovering areas 131 with equal sizes are respectively provided. A circuit trace 311 and pads 312 are provided in the middle of the third copper foil 31, and a middle solder mask 34 is provided on the circuit trace 311 and the pads 312. Pad openings (that is, the middle solder mask 34 is opened on the surface of the pads 312 to expose the pads 312, not shown in the figure) are provided on the surfaces of the pads 312, and the middle solder mask 34 is larger than the second PP opening 221. A filling mechanism 40 is provided inside the first PP opening 211, the bare board opening 201, and the second PP opening 221. A second conductive mechanism 36 is provided between the third copper foil 31, the second substrate 30, and the fourth copper foil 32. A first conductive mechanism 35 is provided between the first copper foil 11, the first substrate 10, the second copper foil 12, the first PP board 21, the bare board 20, the second PP board 22, the third copper foil 31, the second substrate 30, and the fourth copper foil 32. Both the first conductive mechanism 35 and the second conductive mechanism 36 are copper-plated vias, and their specific quantities should be determined according to the customer requirements of the stepped board. The PP board is also called polypropylene (PP) board.

[0027] Specifically, the perimeter of the bare board opening 201 is reduced inward by 0.5 mm compared to the perimeters of the first PP opening 211 and the second PP opening 221. The purpose of doing this is to effectively prevent the melt of the first PP board 21 and the second PP board 22 from flowing into the bare board opening 201 during high-temperature lamination. The perimeter mentioned in this solution refers to the outer perimeter, and this outer perimeter is a closed trajectory.

[0028] Specifically, the perimeter of the middle solder mask 34 extends 0.5 mm outward from the perimeter of the second PP opening 221. That is, the perimeter of the middle solder mask 34 extends 1 mm outward from the perimeter of the bare board opening 201. The purpose of this is to prevent the area outside the perimeter edge of the middle solder mask 34 from being seen through the bare board opening 201 after the stepped board cover is removed, thereby effectively protecting other traces and areas on the third copper foil 31 that do not have a solder mask layer from being exposed.

[0029] Specifically, the perimeters of the second copper foil cover removal area 121, the first substrate cover removal area 101, the first copper foil cover removal area 111, and the top solder mask cover removal area 131 extend 0.1 mm outward from the perimeter of the bare board opening 201. Additionally, the perimeter of the filling mechanism 40 is reduced by 0.5 mm inward from the perimeter of the bare board opening 201. The purpose of this is to facilitate the removal of the filling mechanism 40 after the stepped board cover is removed.

[0030] Specifically, the first copper foil 11, the first substrate 10, and the second copper foil 12 are combined into a double-sided board, and the third copper foil 31, the second substrate 30, and the fourth copper foil 32 are combined into another double-sided board.

[0031] Specifically, the filling mechanism 40 includes a backing plate 43 in the middle, a first high-temperature tape 41 disposed on the upper side of the backing plate 43, and a second high-temperature tape 42 disposed on the lower side of the backing plate 43. The purpose of this is that when the two double-sided boards and the middle bare board 20 are hot-pressed with the first PP board 21 and the second PP board 22, the first PP board 21 and the second PP board 22 will not overflow into the bare board opening 201 and stick to the backing plate 43 in the high-temperature state, nor will there be an adhesion phenomenon between the filling mechanism 40 and the middle solder mask 34 or the second copper foil 12.

[0032] Specifically, the thickness of the second substrate 30 is greater than the thickness of the first substrate 10, and the thickness of the bare board 20 is less than the thickness of the first substrate 10. As an example of the implementation of this solution, preferably: the materials of the first substrate 10, the second substrate 30, and the bare board 20 are fiber boards. The thickness of the first substrate 10 is 400 μm, the thickness of the second substrate 30 is 670 μm, and the thickness of the bare board 20 is 250 μm. The thickness of the first copper foil 11 is 45 μm, the thickness of the second copper foil 12 is 30 μm, and the thickness of the top solder mask is 20 μm. The thickness of the third copper foil is 30 μm, the thickness of the fourth copper foil is 45 μm, the thickness of the bottom solder mask is 20 μm, and the thickness of the middle solder mask is 20 μm. The thickness of the first PP board 21 is 66 μm, and the thickness of the second PP board 22 is 75 μm. The thickness of the backing plate 43 is 250 μm, and the thicknesses of the first high-temperature tape 41 and the second high-temperature tape 42 are both 60 μm.

[0033] As Example 1: The middle solder mask 34, the first PP opening 211, the bare board opening 201, the second PP opening 221, the second copper skin uncovering area 121, the first substrate uncovering area 101, the first copper skin uncovering area 111, and the top solder mask uncovering area 131 are all rectangles with rounded corners at the four corners.

[0034] As Example 2: The middle solder mask 34, the first PP opening 211, the bare board opening 201, the second PP opening 221, the second copper skin uncovering area 121, the first substrate uncovering area 101, the first copper skin uncovering area 111, and the top solder mask uncovering area 131 are all ellipses (not shown in the figure).

[0035] A processing step of a stepped board in this solution is briefly described as follows:

[0036] (1) Blanking: Cut two double-sided boards into sizes that match the capabilities of in-plant equipment for convenient production.

[0037] (2) First through-hole drilling: Process the through-holes of the second conductive mechanism 36.

[0038] (3) First electroplating: Electroplate copper on the through-holes and the board surface of the second conductive mechanism 36.

[0039] (4) Resin plugging + grinding: Plug the through-holes of the second conductive mechanism 36 with resin and grind the resin at the hole openings flat.

[0040] (5) Inner layer circuit: According to customer requirements, engrave the circuit traces of the second copper skin 12 and the third copper skin 31 and the SMD pads for chip mounting on the copper-clad board surface.

[0041] (6) Middle solder mask: Use insulating photosensitive ink to process the middle solder mask 34 on the third copper skin 31 and open the windows for the pads 312.

[0042] (7) Prepare the bare board, PP board, and backing plate: Process the bare board 20 and the bare board opening 201, the first PP board 21 and the first PP opening 211, the second PP board 22 and the second PP opening 221 according to the above structural requirements. Stick the first high-temperature tape 41 and the second high-temperature tape 42 on the upper and lower surfaces of the backing plate 43, and then process them into the above structural requirements, such as rectangles with rounded corners at the four corners.

[0043] (8) High-temperature lamination: Press and cure the boards of all layers shown in Figure 1 together as one body. (Note: During production, positioning holes are provided in the middle of the four sides of the panel of each layer except the backing plate)

[0044] (9) Second through-hole drilling: Process the through-holes of the first conductive mechanism 35.

[0045] (10) Second electroplating: Copper plating is carried out on the vias of the first conductive mechanism 35, and the surfaces of the first copper foil 11 and the fourth copper foil 32.

[0046] (11) Outer layer circuit: According to the customer's requirements, the outermost copper-clad board surface (referring to the first copper foil 11 and the fourth copper foil 32) is etched to form circuit traces and SMD pads 14 for chip mounting.

[0047] (12) Top and bottom solder mask: The circuit trace parts of the outer layer (the trace parts on the first copper foil 11 and the fourth copper foil 32) are protected with insulating photosensitive ink, and the SMD pads 14 of the parts that need to be chip-mounted are opened to expose.

[0048] (13) Letter silk screen printing: Add text descriptions to the SMD pads of the parts that need to be chip-mounted for the customer, which is convenient for chip mounting.

[0049] (14) Uncover the cover and rout the board: According to the above structural requirements, strictly control the routing depth of the board, rout the top solder mask uncovering area 131, the first copper foil uncovering area 111, and the second copper foil uncovering area 121, and take out the filling mechanism 40.

[0050] (15) Surface treatment: The copper surfaces of the outer layer (the first copper foil 11 and the fourth copper foil 32) and the inner layer exposed on the surface (referring to the opening area) are subjected to surface treatment according to the customer's requirements (such as gold plating, tin spraying, OSP, etc.).

[0051] (16) Shaping: According to the finished unit size requirements provided by the customer, the stepped board (such as the Figure 3 shown panel) is cut (milled, routed).

[0052] (17) Testing: Conduct conduction performance testing on each unit stepped board, and transfer the boards with qualified conduction to the next process.

[0053] (18) Inspection: Conduct appearance inspection on the boards with qualified conduction testing, and transfer them to the next process after passing.

[0054] (19) Packaging: According to the customer's requirements, package and ship the qualified stepped boards.

[0055] In summary, the technical solution of the present utility model has the following beneficial effects:

[0056] This proposal proposes a stepped board structure that solves customer design requirements. Solder mask is applied on the inner layer circuit. After the product is finished, the inner layer solder mask needs to be exposed on the outer surface. The inner layer SMD (pad) needs to be gold-treated. During the production process, the inner layer circuit and solder mask ink will not be damaged when the outer layer is removed. The quality of the stepped board is guaranteed, the production qualification rate is high, it can meet the requirements of mass production, and increase the company's order quantity. In this solution, a light plate is provided between two double-sided boards stacked one above the other, a light plate window is provided in the middle of the light plate, and a first PP plate and a second PP plate with a middle window are provided on the upper and lower sides of the light plate. A filling mechanism with a surrounding edge smaller than the surrounding edge of the light plate window is provided inside the light plate window, the first PP plate window and the second PP plate window. Above the light plate window and the first PP plate window, a precise uncovering area is set for the upper double-sided board, and the surrounding edge of the uncovering area is expanded outward by 0.1mm than the surrounding edge of the light plate window. After the two double-sided boards and the light plate in the middle are pressed together by the first PP plate and the second PP plate, the first conductive mechanism is processed between the two double-sided boards and the light plate, the first PP plate and the second PP plate, and the top and bottom surfaces of the pressed board are routed and the pads are processed. After the top and bottom surfaces of the pressed board are treated with a solder mask layer, the uncovering area of the upper double-sided board is gonged down by gonging. The gonging depth is strictly controlled during gonging, and finally the uncovering process of the upper double-sided board is completed. Because the filling mechanism in this solution consists of a backing plate with first and second high-temperature tapes attached to its upper and lower sides, respectively, when the two double-sided boards and the middle bare board are subjected to high-temperature lamination with the first and second PP boards, the first and second PP boards will not overflow into the bare board windows at high temperatures and adhere to the backing plate. Furthermore, there will be no adhesion between the filling mechanism and the middle solder mask or the second copper foil. Through careful design of the window opening and the dimensions of the cover area, and strict control of the depth of the cover area during removal, this solution ensures that the inner layer circuits and solder mask ink will not be damaged during removal, thereby improving the pass rate of the step board.

[0057] The above-described embodiments do not constitute a limitation on the scope of protection of this technical solution. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the above-described embodiments shall be included in the scope of protection of this technical solution.

Claims

1. Structure of a stepped plate, characterized in that: It includes a first substrate, a first copper foil disposed on the upper side of the first substrate, a second copper foil disposed on the lower side of the first substrate, a top solder mask disposed on the upper side of the first copper foil, a first prepreg board disposed on the lower side of the second copper foil, a bare board disposed on the lower side of the first prepreg board, a second prepreg board disposed on the lower side of the bare board, a third copper foil disposed on the lower side of the second prepreg board, a second substrate disposed on the lower side of the third copper foil, a fourth copper foil disposed on the lower side of the second substrate, and a bottom solder mask disposed on the lower side of the fourth copper foil; a first prepreg opening, a bare board opening, and a second prepreg opening are respectively provided in the middle parts of the first prepreg board, the bare board, and the second prepreg board, the sizes of the first prepreg opening and the second prepreg opening are equal, and the bare board opening is smaller than the first prepreg opening and the second prepreg opening; middle parts of the second copper foil, the first substrate, the first copper foil, and the top solder mask above the first prepreg opening are respectively provided with a second copper foil uncovering area, a first substrate uncovering area, a first copper foil uncovering area, and a top solder mask uncovering area with equal sizes; a circuit trace and a pad are provided in the middle part of the third copper foil, and a middle solder mask is provided on the circuit trace and the pad, a pad opening is provided on the surface of the pad, and the middle solder mask is larger than the second prepreg opening; a filling mechanism is provided inside the first prepreg opening, the bare board opening, and the second prepreg opening, a second conductive mechanism is provided between the third copper foil, the second substrate, and the fourth copper foil, and a first conductive mechanism is provided between the first copper foil, the first substrate, the second copper foil, the first prepreg board, the bare board, the second prepreg board, the third copper foil, the second substrate, and the fourth copper foil.

2. The structure of a stepped plate according to claim 1, characterized in that: The periphery of the bare board opening is reduced inward by 0.5 mm compared with the peripheries of the first prepreg opening and the second prepreg opening.

3. The structure of a stepped plate according to claim 1, wherein: The periphery of the middle solder mask is expanded outward by 0.5 mm compared with the periphery of the second prepreg opening.

4. The structure of a stepped plate according to claim 1, characterized in that: The peripheries of the second copper foil uncovering area, the first substrate uncovering area, the first copper foil uncovering area, and the top solder mask uncovering area are expanded outward by 0.1 mm compared with the periphery of the bare board opening.

5. The structure of a stepped plate according to claim 1, characterized in that: The periphery of the filling mechanism is reduced inward by 0.5 mm compared with the periphery of the bare board opening.

6. The structure of a stepped plate according to claim 5, characterized in that: The filling mechanism includes a backing plate in the middle, a first high-temperature tape disposed on the upper side of the backing plate, and a second high-temperature tape disposed on the lower side of the backing plate.

7. The structure of a stepped plate according to claim 1, wherein: The middle solder mask, the first prepreg opening, the bare board opening, the second prepreg opening, the second copper foil uncovering area, the first substrate uncovering area, the first copper foil uncovering area, and the top solder mask uncovering area are all rectangles with rounded corners, or the middle solder mask, the first prepreg opening, the bare board opening, the second prepreg opening, the second copper foil uncovering area, the first substrate uncovering area, the first copper foil uncovering area, and the top solder mask uncovering area are all ellipses.

8. The structure of a stepped plate according to claim 1, wherein: The first copper foil, the first substrate, and the second copper foil are combined into one double-sided board, and the third copper foil, the second substrate, and the fourth copper foil are combined into another double-sided board.

9. The structure of a stepped plate according to claim 1, wherein: The thickness of the second substrate is greater than the thickness of the first substrate, and the thickness of the bare board is less than the thickness of the first substrate.

10. The structure of a stepped plate according to claim 1, characterized in that: Both the first conductive mechanism and the second conductive mechanism are copper-plated vias.

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