Structure for reducing grounding resistance of FPC and steel sheet
By adopting new materials and processes, the problems of high cost, low conductivity and stability of conductive adhesive in FPC and steel sheet grounding processes have been solved, achieving grounding effects with low resistance, high reliability and small space.
Patent Information
- Application Number
- CN202423068819.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-12
- Publication Date
- 2025-12-02
- Estimated Expiration
- 2034-12-12
AI Technical Summary
The existing FPC and steel sheet grounding process has high cost of conductive adhesive film, low conductivity, large fluctuation of grounding resistance, and easy migration of conductive filler, resulting in unstable grounding.
Solder paste or nickel paste is used instead of conductive adhesive. PTH holes are opened on the stainless steel sheet and tin or nickel is plated on them. The solder paste or nickel paste is then soldered to the FPC to form H-type PTH holes. Nickel-gold soldering is performed at the contact points to reduce grounding resistance.
It reduces the grounding resistance to within 0.5Ω, reduces material costs, improves grounding reliability and reinforcement stripping strength, meets the application requirements of low resistance and space, and can be applied to smaller FPCs.
Smart Images
Figure CN223626065U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of optimizing FPC and steel sheet grounding technology, and particularly relates to a structure for reducing the grounding resistance of FPC and steel sheet. Background Technology
[0002] The current process for grounding FPC (Flexible Printed Circuit) and steel sheet mainly involves opening grounding pad windows on the copper surface of the FPC and using conductive adhesive film as a connection medium to achieve effective grounding conduction.
[0003] Based on the above analysis, the problems and defects of the existing technology are as follows: the cost of the conductive adhesive film in the existing technology is relatively high; the conductivity is relatively low (resistance > 3Ω); the grounding resistance of the conductive adhesive fluctuates greatly under the influence of temperature and humidity; and the conductive filler is prone to migration. Utility Model Content
[0004] To overcome the problems existing in related technologies, the present invention discloses a structure for reducing the grounding resistance of FPC and steel sheet.
[0005] The technical solution is as follows: A structure for reducing the grounding resistance between the FPC and the steel sheet, comprising:
[0006] A PTH hole is formed sequentially through the first cover layer, the first copper layer, the polyimide layer, the second copper layer, the second cover layer, the silkscreen layer, and the stainless steel sheet. Solder paste or nickel paste is melted in the space of the PTH hole and soldered to the FPC on the surface of the stainless steel sheet.
[0007] A stainless steel sheet is provided at the bottom of the screen printing layer, and a PTH hole is provided on the upper part of the stainless steel sheet for soldering or nickel injection at the grounding coordinate.
[0008] Furthermore, a tin-plated or nickel-plated layer is welded to the pre-steel sheet reinforcement of the stainless steel sheet.
[0009] Furthermore, the solder paste or nickel paste is connected to the stainless steel sheet by hollowing out the adhesive film in the grounding area of the stainless steel sheet; the hollowing out of the adhesive film is a hollowing out of the screen printing layer.
[0010] Furthermore, the screen printing layer uses ordinary adhesive, and the PTH holes are H-shaped;
[0011] The first cover layer, the first copper layer, the polyimide layer, the second copper layer, the second cover layer, and the screen printing layer are all divided into left and right parts by PTH holes;
[0012] The first and second copper layers of the left and right parts are separated by PTH holes, connected by copper layers, and covered with the separated polyimide layers.
[0013] Furthermore, the hole walls at the contact points between the PTH hole and the first cover layer, the first copper layer, the polyimide layer, the second copper layer, the second cover layer, and the silkscreen layer are nickel-gold bonded, and the hole pads of the PTH hole are also nickel-gold bonded.
[0014] Furthermore, the diameter of the cut-through hole in the second copper layer on the second cover layer is smaller than the diameter of the cut-through hole in the second cover layer and the silkscreen layer.
[0015] Furthermore, the diameter of the through-hole cut in the first cover layer of the first copper layer is equal to the diameter of the through-hole cut in the second cover layer and the silkscreen layer.
[0016] Combining all the above technical solutions, the beneficial effects of this utility model are as follows: This utility model reduces the grounding resistance between the steel sheet reinforcement and the FPC to within 0.5Ω; ordinary thermosetting adhesive can be used for the adhesive film, reducing the cost of the adhesive film; it meets the customer's requirement for low grounding resistance of the steel sheet; and it saves structural space for the customer. This utility model differs from traditional processes by reducing the required grounding space, some of which can be placed below the device; by using solder paste instead of conductive adhesive to conduct electricity with the steel sheet, it not only reduces technical costs but also improves grounding reliability and reinforcement peel strength; compared to conductive adhesive processes, solder grounding has lower grounding resistance and very high reliability. Attached Figure Description
[0017] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure;
[0018] Figure 1 This is a flowchart provided by an embodiment of the present invention for reducing the grounding resistance between the FPC and the steel sheet;
[0019] Figure 2 This is a diagram illustrating the conductivity effect of the solder paste of this utility model replacing conductive adhesive with that of the steel sheet, as provided in this embodiment of the utility model.
[0020] Figure 3 This is a diagram of a grounding structure for conductive adhesive in existing technology.
[0021] Figure 4 This is a diagram of the welding grounding structure of this utility model;
[0022] In the diagram: 1. First cover layer; 2. First copper layer; 3. Polyimide layer; 4. Second copper layer; 5. Second cover layer; 6. Silkscreen layer; 7. Stainless steel sheet; 8. PTH hole; 9. Solder paste or nickel paste. Detailed Implementation
[0023] To make the above-mentioned objectives, features, and advantages of this utility model more apparent and understandable, the specific embodiments of this utility model are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a full understanding of this utility model. However, this utility model can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this utility model. Therefore, this utility model is not limited to the specific embodiments disclosed below.
[0024] Example 1, such as Figure 1 As shown in the embodiment of this utility model, the method for reducing the grounding resistance between the FPC and the steel sheet specifically includes:
[0025] S1, When manufacturing FPC, a PTH hole 8 for soldering or nickel is opened at the grounding coordinate of stainless steel sheet 7.
[0026] The PTH hole 8 penetrates the first cover layer 1, the first copper layer 2, the polyimide (PI) layer 3, the second copper layer 4, the second cover layer 5, and the screen printing layer 6 (AD). The screen printing layer 6 (AD) uses ordinary adhesive. The PTH hole 8 is H-shaped. The hole wall at the contact point between the PTH hole 8 and the above-mentioned structural layers is treated with nickel-gold. The hole pad of the PTH hole 8 is also treated with nickel-gold.
[0027] S2, tin or nickel plating is applied to the pre-steel sheet reinforcement area of stainless steel sheet 7, and the adhesive film in the grounding area of stainless steel sheet 7 is removed to expose stainless steel sheet 7.
[0028] S3, bonded to stainless steel sheet 7, for steel sheet reinforcement;
[0029] S4. Apply solder paste or nickel paste 9 to the PTH hole 8. After mounting and soldering SMT components, the solder paste or nickel paste 9 melts and flows through the PTH hole 8 from the FPC surface to the surface of the stainless steel sheet 7 to achieve soldering with the FPC.
[0030] In step S1, the method for creating a PTH hole 8 for soldering or nickel at the ground coordinate of the stainless steel sheet 7 includes:
[0031] S101: Obtain the cutting dimensions and cutting depth of the pre-opened PTH hole 8, and use the controller to control the cutting equipment to perform cutting.
[0032] S102, using a cutting device to cut the grounding coordinates of the stainless steel sheet 7, which is sequentially covered with the second covering layer 5 and the silk screen layer 6, and expose the stainless steel sheet 7.
[0033] S103, the second copper layer 4 adhered to the cut second cover layer 5 is cut with through holes according to the cutting operation information preset in step S101. Then, the polyimide layer 3 adhered to the cut second copper layer 4 is cut with through holes according to the cutting operation information preset in step S101. Then, the first copper layer 2 adhered to the cut polyimide layer 3 is cut with through holes according to the cutting operation information preset in step S101. At the same time, the cut first copper layer 2 and second copper layer 4 are gold-plated to connect the first copper layer 2 and the second copper layer 4 and to cover the polyimide layer 3.
[0034] S104, the first cover layer 1 adhered to the first copper layer 2 after cutting is cut into through holes according to the cutting operation information preset in step S101, and finally PTH holes 8 for soldering or nickel are obtained.
[0035] Example 2, as a preferred embodiment, in step S103, the diameter of the through hole cut on the second copper layer 4 adhered to the cut second cover layer 5 is smaller than the diameter of the through hole cut on the second cover layer 5 and the silk screen layer (6) in step S102;
[0036] In step S104, the diameter of the through hole cut into the first cover layer 1 adhered to the first copper layer 2 after cutting is the same as the diameter of the through hole cut into the second cover layer 5 and the silkscreen layer 6 in step S102.
[0037] In step S101, the method by which the controller controls the cutting device to cut through holes in each layer includes:
[0038] In the initial cutting stage, the cutting points in the cutting network composed of the size and depth of the through holes to be cut in each layer measure the size and depth of each other with their neighbors and store the distance information with their neighbors;
[0039] The initial cutting point sends its coordinate information, and unknown cutting points that have collected enough information execute the cutting point optimization method;
[0040] Once the unknown cutting point has been optimized and determined, update whether the cutting point has been optimized and determined. The initial value is 0, and it is updated to 1 after optimization and determination. In the next round of optimization and determination, it becomes a cutting point and sends its own coordinate information.
[0041] Unknown cutting points that are not optimized and determined in this round enter a waiting state, waiting for enough information to be received in the next round of optimization and determination to complete the optimization and determination.
[0042] The rules of the cutting point optimization method include:
[0043] (1) The probability P of the polyhedron formed by multiple cutting points s <P max ,Pmax The threshold for the probability number of a polyhedron;
[0044] (2) The volume of the polyhedron formed by multiple cutting points;
[0045] (3) The distance from the unknown cutting point to multiple cutting points remains consistent; the cutting point optimization method selects the cutting point on a hollow sphere centered at the unknown cutting point, and the expression is:
[0046]
[0047] In the formula, ||·|| is the L2 norm, E and F are points on the hollow sphere, and λ is the maximum value. max Let T be the norm characteristic root and T be the order.
[0048] The probability P of a polyhedron formed by multiple cutting points s The expression is:
[0049] P s =P(E1)+P(E2)+P(E3)+P(E4)
[0050] In the formula, P(E1), P(E2), P(E3), and P(E4) are the probabilities of the 1st, 2nd, 3rd, and 4th faces, respectively.
[0051] All unknown cut points communicate directly with any cut point. The accuracy of the coordinate estimation is evaluated using the mean absolute error (MAE), which is defined as follows:
[0052]
[0053] In the formula, Let X be the estimated coordinates of the i-th cutting point. i Let N be the actual coordinates of the i-th cutting point, and N be the total number of cutting points.
[0054] This invention utilizes the aforementioned controller to control the cutting equipment to cut through holes in each layer, thereby enabling precise control of the size and depth of the PTH hole 8.
[0055] As can be seen from the above embodiments, compared with the traditional conductive adhesive grounding process, the new process reduces material costs; the grounding resistance of the traditional conductive adhesive is above 3Ω and the stability is poor, while the grounding resistance of the new process is less than 0.5Ω and the stability is high; the new process requires less space for grounding than the traditional process and can be applied to smaller FPCs.
[0056] This invention solves problems such as low resistance, high cost, and improved reliability by replacing conductive adhesive with solder paste to achieve conductivity with the steel sheet. The effect is as follows: Figure 2 As shown in Table 1 below, the specific experimental comparisons are as follows;
[0057] Table 1. Experimental Comparison Table
[0058]
[0059]
[0060] A comparison of existing conductive adhesive grounding and welding grounding structures, such as... Figure 3 This is a diagram of an existing conductive adhesive grounding structure; such as... Figure 4 This is a diagram of the welding grounding structure of this utility model;
[0061] Figure 3 The following layers are sequentially attached to the upper conductor: a first cover layer 1, a first copper layer 2, a polyimide (pi) layer 3, a second copper layer 4, a second cover layer 5, a screen printing layer (AD) 6, using conductive adhesive; and a stainless steel sheet (SUS) 7.
[0062] like Figure 4 As shown, the welding grounding structure includes:
[0063] PTH holes 8 sequentially penetrate the first cover layer 1, the first copper layer 2, the polyimide (pi) layer 3, the second copper layer 4, the second cover layer 5, and the screen printing layer (AD) 6.
[0064] The bottom of the PTH hole 8 is located on the upper surface of the stainless steel sheet 7;
[0065] The screen printing layer (AD) 6 uses ordinary adhesive, and the PTH hole 8 is H-shaped;
[0066] The first cover layer 1, the first copper layer 2, the polyimide (pi) layer 3, the second copper layer 4, the second cover layer 5, and the screen printing layer (AD) 6 are all divided into left and right parts by PTH holes 8.
[0067] The first copper layer 2 and the second copper layer 4 of the left and right parts are separated by PTH holes 8, connected by copper layers, and covered by the separated polyimide (pi) layer 3.
[0068] Solder paste or nickel paste 9 is melted inside the space of the PTH hole 8;
[0069] The solder paste or nickel paste 9 is connected to the stainless steel sheet 7 by hollowing out the adhesive film in the grounding area.
[0070] In existing conductive adhesive grounding resistance testing, the minimum grounding resistance is 2.0Ω, which limits the grounding resistance testing. In this invention, the minimum grounding resistance is 0.2Ω, further expanding the application range of grounding resistance testing.
[0071] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.
[0072] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any modifications, equivalent substitutions and improvements made by those skilled in the art within the scope of the technology disclosed in the present utility model, within the spirit and principles of the present utility model, should be included within the protection scope of the present utility model.
Claims
1. A structure for reducing the grounding resistance between an FPC and a steel sheet, characterized in that, The structure includes: PTH holes (8) sequentially penetrate the first cover layer (1), the first copper layer (2), the polyimide layer (3), the second copper layer (4), the second cover layer (5), the silkscreen layer (6), and the stainless steel sheet (7). Solder paste or nickel paste (9) is melted in the space of the PTH holes (8), and the solder paste or nickel paste (9) is soldered to the FPC on the surface of the stainless steel sheet (7). A stainless steel sheet (7) is provided at the bottom of the silkscreen layer (6), and a PTH hole (8) is provided on the upper part of the stainless steel sheet (7) for soldering or nickel to the ground coordinate.
2. The structure for reducing the grounding resistance between the FPC and the steel sheet according to claim 1, characterized in that, A tin-plated or nickel-plated layer is welded to the pre-steel sheet reinforcement of the stainless steel sheet (7).
3. The structure for reducing the grounding resistance between the FPC and the steel sheet according to claim 1, characterized in that, The solder paste or nickel paste (9) is connected to the stainless steel sheet (7) by hollowing out the adhesive film in the grounding area of the stainless steel sheet (7); the hollowing out of the adhesive film is a hollowing out of the silk screen layer (6).
4. The structure for reducing the grounding resistance between the FPC and the steel sheet according to claim 1, characterized in that, The screen printing layer (6) uses ordinary adhesive, and the PTH hole (8) is H-shaped; The first cover layer (1), the first copper layer (2), the polyimide layer (3), the second copper layer (4), the second cover layer (5), and the screen printing layer (6) are all divided into left and right parts by PTH holes (8); The first copper layer (2) and the second copper layer (4) of the left and right parts are separated by PTH holes (8), connected by copper layers, and covered by the separated polyimide layer (3).
5. The structure for reducing the grounding resistance between the FPC and the steel sheet according to claim 1, characterized in that, The hole walls of the PTH hole (8) at the contact points with the first cover layer (1), the first copper layer (2), the polyimide layer (3), the second copper layer (4), the second cover layer (5), and the silkscreen layer (6) are nickel-gold welded, and the hole pad of the PTH hole (8) is nickel-gold welded.
6. The structure for reducing the grounding resistance between the FPC and the steel sheet according to claim 1, characterized in that, The diameter of the cut-through hole of the second copper layer (4) on the second cover layer (5) is smaller than the diameter of the cut-through hole of the second cover layer (5) and the silkscreen layer (6).
7. The structure for reducing the grounding resistance between the FPC and the steel sheet according to claim 1, characterized in that, The diameter of the through hole cut in the first cover layer (1) of the first copper layer (2) is equal to the diameter of the through hole cut in the second cover layer (5) and the silkscreen layer (6).