A FPC whole board and FPC circuit board manufacturing process

Abstract

The present application belongs to the field of circuit boards, and in particular, relates to an FPC whole board, which includes multiple FPC boards and side boards, and the positions of circuits and components are preset on the FPC boards; a clearance groove is provided at the junction of the FPC boards and the side boards, and the clearance groove runs through the entire FPC board, and there are multiple connection positions between each FPC board and the side board, which are used to fix the FPC board to the side board. The present application has the effect of ensuring the dimensional accuracy and shape stability of the FPC circuit board, thereby improving the functional reliability of the FPC circuit board.

Description

Technical Field

[0001] The present application relates to the field of circuit boards, and in particular to a FPC whole board and a FPC circuit board manufacturing process. Background Art

[0002] At present, the processing method of flexible printed circuit board (FPC) is usually to divide a whole board into multiple small circuit boards. Specifically, components are first printed and soldered on a whole board to form multiple FPC circuit boards with independent circuits but interconnected in structure, and then the unnecessary side boards are cut and removed to obtain multiple finished FPC circuit boards.

[0003] This processing method has certain advantages and wide application. Its main advantage is that it can improve production efficiency and reduce costs. By presetting multiple small circuit boards, multiple circuit boards can be processed simultaneously during one processing process, which greatly shortens the production cycle and improves production efficiency. In addition, whole board processing can also make irregularly shaped FPC circuit boards occupy the edge space between each other, make full use of the board area, reduce material waste, and thus reduce costs.

[0004] However, this processing method also has some problems. During the production process, the FPC circuit board will be heated due to soldering components and printed circuits, while the side board will remain at a low temperature because there is no subsequent processing. The FPC circuit board that expands due to heat and the side board that still maintains the original size squeeze each other, resulting in the instability of the FPC circuit board and the positioning deviation of the components. Since the FPC is in a high temperature state at this time, the defects at this stage may still be retained in the finished product, thereby affecting the yield rate. Summary of the invention

[0005] In order to solve the above problems and ensure the dimensional accuracy and shape stability of the FPC circuit board, thereby improving the functional reliability of the FPC circuit board, in a first aspect, the present application provides an FPC whole board.

[0006] The FPC board provided in this application adopts the following technical solution:

[0007] A whole FPC board comprises a plurality of FPC boards and side boards, wherein components are arranged on the FPC boards; a clearance groove is provided at the junction of the FPC boards and the side boards, the clearance groove runs through the whole FPC board, and a plurality of connection positions are provided between each of the FPC boards and the side boards, for fixing the FPC boards to the side boards.

[0008] By adopting the above technical solution, a gap is reserved between the FPC board and the side board, and the connection position provides necessary positioning and support. When the FPC board becomes larger in size due to heat during the production process, the clearance groove can provide it with expansion space, and the FPC board will not be squeezed against the side board, effectively avoiding the reduction of dimensional accuracy and shape stability of the FPC board due to squeezing.

[0009] Optionally, a straight-line distance between the connection positions corresponding to adjacent FPC boards is greater than or equal to 0.55 mm.

[0010] By adopting the above technical solution, a sufficient distance is maintained between adjacent connection positions, ensuring that there is a sufficient force-bearing structure between adjacent connection positions to provide support for the FPC board.

[0011] Optionally, a V-shaped groove is provided on the connection position, and a side of the V-shaped groove close to the FPC board has an intersection line with the surface of the FPC board, and the intersection line is located at an edge of the FPC board.

[0012] By adopting the above technical solution, after processing the circuits and components on the FPC single board, the FPC single board and the side board can be separated more easily to obtain a finished workpiece.

[0013] Optionally, a plane passing through the bottom edge of the V-shaped groove and bisecting the V-shaped groove is perpendicular to the surface of the FPC board.

[0014] By adopting the above technical solution, the cracks caused by the bottom edge of the V-shaped groove as the crack source are perpendicular to the surface of the FPC board. Under stress concentration, the burrs of the FPC board will not be too large due to bias towards the side board, nor will the edge of the FPC board be missing due to bias towards the FPC board.

[0015] Optionally, each of the connection positions is provided with two V-shaped grooves that are arranged opposite to each other, and the bottom sides of the two V-shaped grooves are parallel to the surface of the FPC substrate.

[0016] By adopting the above technical solution, the two V-shaped grooves create stress concentration from both sides, which can more easily induce cracks. Moreover, because both sides of the connection position are crack sources, the crack depth caused by a single crack source decreases, further preventing the burrs of the FPC board from being too large and the edges of the FPC board from being missing due to the inclination of the cracks.

[0017] Optionally, the width of the clearance groove is 0.7 mm.

[0018] By adopting the above technical solution, the width of the give way groove can meet the working requirements in most common production scenarios, and the small size will not excessively waste the plate raw materials.

[0019] Optionally, the width of the clearance groove is positively correlated with the dimension of the FPC board in the width direction of the clearance groove.

[0020] By adopting the above technical solution, since the thermal expansion of the board is proportional to its thermal expansion coefficient, temperature difference and the original size of the object, the expansion after heating is also larger in the direction where the FPC board is larger, and the wider clearance groove can ensure that the FPC board is not squeezed between the side boards.

[0021] Optionally, the width of the clearance groove is greater than or equal to 2% of the dimension of the FPC board in the width direction of the clearance groove.

[0022] By adopting the above technical solution, at a common reflow temperature of 150°C-280°C and a common expansion coefficient of the FPC board, even without considering the additional clearance space provided by the expansion of the side board after heating, the space of the clearance groove is sufficient to accommodate the expansion of the FPC board.

[0023] In a second aspect, the present application provides a FPC circuit board manufacturing process.

[0024] The present application provides an FPC circuit board manufacturing process using the following technical solutions:

[0025] A FPC circuit board manufacturing process comprises the following steps:

[0026] B1. Provide a whole board, on which at least two FPC board areas should be preset;

[0027] B2. Processing a clearance groove according to the preset position of each FPC board, wherein a side of the clearance groove close to the FPC board coincides with an edge of the FPC board;

[0028] B3, printing the circuit on the FPC board;

[0029] B4, placing flux on the FPC board;

[0030] B5. Attaching components to the position of the whole board where the flux is provided, and performing reflow soldering;

[0031] B6. Punch the whole board to separate the FPC board from the remaining material to obtain a finished FPC circuit board provided with circuits and components.

[0032] By adopting the above technical solution, a clearance groove is opened in advance near the FPC board in step B2. When the FPC board expands due to heat in subsequent processing, the expansion size is accommodated by the clearance groove to prevent the FPC board from contacting the side board and causing product defects.

[0033] Optionally, in step B6, the blade used for punching has a cutting edge close to the FPC board and perpendicular to the surface of the FPC board.

[0034] By adopting the above technical solution, the chips generated during the punching operation slide away from the FPC board to avoid the formation of built-up edge on the side of the tool close to the FPC, thereby preventing the finished FPC circuit board from having a missing edge or curling edge.

[0035] In summary, the present application includes at least one of the following beneficial technical effects:

[0036] 1. Set a clearance groove between the FPC board and the side plate in advance. When the FPC board expands due to the increase in temperature during processing, the expansion size is carried by the clearance groove, avoiding the extrusion of the FPC board and the side plate, thereby ensuring the dimensional accuracy of the finished FPC circuit board and the positioning accuracy of components;

[0037] 2. The width of the clearance groove is positively correlated with the size of the FPC board in the width direction of the clearance groove, because the expansion size of the sheet is proportional to its original size. Therefore, in the direction where the sheet expands more, there is a wider clearance groove to carry it, ensuring the gap between the FPC board and the side board while avoiding material waste caused by opening an overly wide clearance groove;

[0038] 3. The V-shaped groove on the connection position provides a crack source for the subsequent separation of the FPC board and the side board. When external force acts on the FPC board and the side board, stress concentration will occur at the bottom of the V-shaped groove, so that the FPC can be removed from the side board;

[0039] 4. Single-sided punching tools can prevent the accumulation of built-up edge on the side of the FPC board, avoiding the edge missing or curling of the finished FPC circuit board. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a structural schematic diagram of the entire FPC board of Example 1 of the present application;

[0041] Figure 2 yes Figure 1 A partial enlarged view of area A;

[0042] Figure 3 is along Figure 2 A partial cross-sectional view of line BB;

[0043] Figure 4 It is a schematic diagram of the process flow of the FPC circuit board manufacturing process of Example 2 of the present application;

[0044] Figure 5 It is a schematic diagram of the structure of the product of step B5 in Example 2 of the present application.

[0045] Description of reference numerals:

[0046] 1. FPC board; 2. Side board; 3. Components; 4. Make way groove; 5. Connection position; 6. V-shaped groove. DETAILED DESCRIPTION

[0047] The following is combined with Figure 1-5 This application is described in further detail.

[0048] In the conventional FPC circuit board production process, several or even dozens of FPC single board 1 areas are usually preset on a whole FPC blank board, and there are residual side boards 2 between the areas. It is inevitable to generate a large amount of heat in the process of printing circuits and welding components 3 on the FPC circuit board. Once a temperature difference occurs between the FPC single board 1 and the side board 2, the mutual compression between the two will cause the instability of the FPC circuit board and the positioning deviation of the components 3. Moreover, the defects caused under high temperature conditions are very likely to be retained in the final finished product, which will have an adverse effect on the yield rate.

[0049] In fact, this defect caused by the uneven heating of the FPC board 1 and the side board 2 and the mutual squeezing also occurs in the processing of irregularly shaped FPC circuit boards. Due to considerations such as clamping and equipment compatibility, special-shaped circuit boards are often provided with rectangular whole boards of universal sizes in the cutting step. The special-shaped circuit boards are not punched or laser cut to obtain the finished products until the steps such as printing the circuit board and welding the components 3 are completed. In the production process, the FPC board 1 and the side board 2 will still be squeezed.

[0050] In addition, even in the case where part of the FPC board 1 and the side board 2 are heated together, such as during the reflow soldering process, due to the limitation of the fixture, the side board 2 cannot thermally expand synchronously with the FPC board 1, and extrusion will still occur, affecting the dimensional accuracy and shape stability of the product.

[0051] Therefore, how to solve the defects caused by the FPC single board 1 being squeezed by the side board 2 after thermal expansion is of great significance in production practice.

[0052] The embodiments of the present application disclose a manufacturing process of an FPC whole board and an FPC circuit board.

[0053] Example 1

[0054] Reference Figure 1 , Figure 2 The outer edge of the FPC whole board is rectangular, and the FPC whole board has a uniform thickness. It includes multiple FPC boards 1 and side boards 2. The FPC boards 1 are arranged on the PFC whole board, and the side boards 2 do not interfere with any FPC boards 1.

[0055] The size and shape of the FPC board 1 are arranged according to product requirements, preferably multiple identical FPC boards 1, and in other embodiments of the present application, multiple FPC boards 1 of different shapes can also be arranged. In the case of arranging multiple identical FPC boards 1 on the same whole board, each FPC board 1 can be arranged in an array, or reasonably densely laid on the premise of ensuring that the side boards 2 between adjacent FPC boards 1 have sufficient supporting strength, so that the protruding part of the special-shaped FPC board 1 is embedded in the concave part of the adjacent FPC board 1.

[0056] A clearance groove 4 is provided at the junction of each FPC board 1 and the side board 2 . The clearance groove 4 is arranged around the edge of each FPC board 1 . The FPC board 1 is fixed to the side board 2 via a connection position 5 .

[0057] The direction of the tangent parallel to the surface of the entire FPC board and perpendicular to the edge of the clearance groove 4 is defined as the width direction, and the direction perpendicular to the surface of the entire FPC board is defined as the depth direction. The depth of the clearance groove 4 is the same as the thickness of the entire FPC board. In other words, the clearance groove 4 runs through the entire FPC board and separates the FPC single board 1 from the side board 2.

[0058] The width of the clearance groove 4 is positively correlated with the size of the FPC board 1 in the width direction of the clearance groove 4. The larger the size of the FPC in the corresponding direction, the greater its expansion under the same temperature difference, material and other conditions, and a wider clearance groove 4 is required to bear the size difference caused by its thermal expansion. Specifically, the width of the clearance groove 4 is greater than or equal to 2% of the size of the FPC board 1 in the width direction of the clearance groove 4.

[0059] In another embodiment of the present application, for an FPC board 1 with a relatively uniform shape, the width of the clearance groove 4 is 0.7 mm and is not adjusted according to the shape and size of the FPC board 1 .

[0060] At least three connection positions 5 are arranged at the edge of each FPC board 1 to ensure stable connection. All connection positions 5 around the same FPC board 1 are connected in sequence, and the geometric center of the FPC board 1 is located within the polygon formed by the connection. In order to avoid damaging the bearing capacity of the side board 2, the connection positions 5 of adjacent FPC boards 1 should be staggered to avoid any two connection positions 5 facing each other, and the straight-line distance between any two connection positions 5 is greater than or equal to 0.55mm.

[0061] refer to Figure 2 , Figure 3 Preferably, there is a V-shaped groove 6 on the connection position 5 for easy cutting, and the side of the V-shaped groove 6 close to the FPC board 1 has an intersection line with the surface of the FPC board 1, and the intersection line is located at the edge of the FPC board 1. The bottom edge of the V-shaped groove 6 is parallel to the surface of the FPC board 1, and the plane passing through the bottom edge of the V-shaped groove 6 and bisecting the V-shaped groove 6 is perpendicular to the surface of the FPC board 1.

[0062] Further preferably, two opposite V-shaped grooves 6 are provided on each connection position 5 , and the bottom edges of the two V-shaped grooves 6 are coplanar with a plane perpendicular to the surface of the FPC board 1 .

[0063] The implementation principle of Example 1 is:

[0064] For the FPC whole board disclosed in this embodiment, when any FPC single board 1 on the FPC whole board is processed, when the FPC expands due to circuit printing or component 3 welding, the clearance groove 4 arranged around its edge will provide it with expansion space. After the size of the FPC single board 1 increases, there is still a gap with the side board 2, and no squeezing will occur, which naturally will not cause the shape of the finished FPC circuit board to be unstable and the positioning of the component 3 to be offset.

[0065] Specifically, the dimensional change of the sheet material when it is heated and expanded is proportional to the temperature difference, the original size of the sheet material and the material expansion coefficient, and the same is true for the FPC board 1. Taking the reflow soldering analysis, where the FPC sheet material is most severely thermally expanded, the average temperature of the reflow soldering is usually around 220°C, and the highest temperature is less than 300°C, while the expansion coefficient of the FPC board 1 is usually less than or equal to 0.0001 / °C. Therefore, in most cases, the dimensional change of the FPC board 1 during the processing is less than or equal to 3% of its corresponding size, and this size is shared by the clearance grooves 4 on both sides. Even if the side board 2 is not considered to make way for a larger space after thermal expansion, the original size of the clearance groove 4 itself is sufficient to bear the dimensional expansion of the FPC board 1 during the processing, avoiding contact and extrusion between the FPC board 1 and the side board 2.

[0066] It is undeniable that there will be a little extrusion at the place where the connection position 5 is set. However, on the one hand, the potential energy stored by the small-scale extrusion deformation is relatively small compared to the entire FPC board 1, and there is a high probability of natural recovery after cooling; on the other hand, during the design, the connection position 5 can be intentionally set at the part of the FPC circuit board where the components 3 and circuits are sparse, so that even if a slight deformation is caused on the FPC board 1, it will not cause the positioning deviation of the components 3 of the finished FPC circuit board.

[0067] The embodiment of the present application also discloses a FPC circuit board manufacturing process.

[0068] Example 2

[0069] Reference Figure 4 , Figure 5 , the FPC circuit board manufacturing process includes the following steps:

[0070] B1. Provide a whole board, on which at least two areas of the FPC board 1 should be preset;

[0071] B2. Processing a clearance groove 4 according to the preset position of each FPC board 1, wherein a side of the clearance groove 4 close to the FPC board 1 coincides with an edge of the FPC board 1;

[0072] B3, printing a circuit on the FPC board 1;

[0073] B4, placing flux on the FPC board 1;

[0074] B5, attaching the component 3 to the position of the whole board where the flux is provided, and performing reflow soldering;

[0075] B6. Punch the whole board to separate the FPC board 1 from the remaining material, and obtain a finished FPC circuit board provided with circuits and components 3.

[0076] In step B1, the entire board should have upper and lower surfaces that are parallel to each other.

[0077] In step B2, the clearance groove 4 is arranged around the edge of the FPC board 1, and each FPC board 1 is surrounded by multiple sections of the clearance groove 4, and there are connection positions 5 between adjacent clearance grooves 4 to ensure the connection between the FPC board 1 and the side board 2, so that the FPC board 1 is fixed and positioned with the entire board. The depth of the clearance groove 4 is the thickness of the entire board, and the width is positively correlated with the size of the FPC board 1 in the width direction of the clearance groove 4. Preferably, the width of the clearance groove 4 is greater than or equal to 2% of the size of the FPC board 1 in the width direction of the clearance groove 4. The method of processing the clearance groove 4 can be mechanical processing subtractive manufacturing or laser processing.

[0078] The product of step B2 is an FPC whole board disclosed in Example 1.

[0079] The tool used for punching in step B6 is a single-sided blade tool, and the cutting edge of the blade is close to the FPC board 1 and is perpendicular to the surface of the FPC board 1.

[0080] The implementation principle of a FPC circuit board manufacturing process in the embodiment of the present application is:

[0081] Heat is generated during the processing of steps B3 and B5, causing the FPC board 1 to expand due to the heat. The expanded FPC board 1 extends in all directions in the makeshift groove 4. Because the deformation amount is smaller than the width of the makeshift groove 4, and the connection position 5 positions the FPC board 1 from multiple directions to prevent it from shifting, the FPC board 1 and the side plate 2 are never in contact, so they will not be squeezed under high temperature conditions. The finished FPC circuit board has excellent dimensional accuracy, the components 3 are accurately positioned, the connection is stable, and the yield rate is high.

[0082] In addition, in step B6, the use of a single-sided cutting tool can effectively prevent the built-up edge formed by the chips from accumulating on the side of the cutting edge close to the FPC board 1 or even squeezing the FPC board 1 during the punching process, thereby avoiding missing edges or curling of the finished FPC circuit board.

[0083] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A FPC whole board, characterized in that: The invention comprises a plurality of FPC boards (1) and side boards (2), wherein the positions of the circuits and components (3) are preset on the FPC boards (1); a clearance groove (4) is provided at the junction of the FPC boards (1) and the side boards (2); the clearance groove (4) runs through the entire FPC board, and a plurality of connection positions (5) are provided between each of the FPC boards (1) and the side boards (2), for fixing the FPC boards (1) on the side boards (2); The width of the clearance groove (4) is positively correlated with the dimension of the FPC board (1) in the width direction of the clearance groove (4); the width of the clearance groove (4) is greater than or equal to 2% of the dimension of the FPC board (1) in the width direction of the clearance groove (4); The connection position (5) is provided with a V-shaped groove (6); a side of the V-shaped groove (6) close to the FPC board (1) has an intersection line with the surface of the FPC board (1), and the intersection line is located at the edge of the FPC board (1); a plane passing through the bottom edge of the V-shaped groove (6) and bisecting the V-shaped groove (6) is perpendicular to the surface of the FPC board (1); each connection position (5) is provided with two V-shaped grooves (6) arranged opposite to each other, and the bottom edges of the two V-shaped grooves (6) are parallel to the surface of the FPC board (1).

2. The FPC whole board according to claim 1, characterized in that: The straight-line distance between the connection positions (5) corresponding to adjacent FPC boards (1) is greater than or equal to 0.55 mm.

3. The FPC whole board according to claim 1, characterized in that: The width of the clearance groove (4) is 0.7 mm.

4. A FPC circuit board manufacturing process according to claim 1, characterized in that: The following steps are involved: B1. Provide a whole board, on which at least two FPC boards (1) should be pre-set; B2. machining a clearance groove (4) according to the preset position of each FPC board (1), wherein a side of the clearance groove (4) close to the FPC board (1) coincides with an edge of the FPC board (1); B3, printing a circuit on the FPC board (1); B4, placing flux on the FPC board (1); B5, attaching the component (3) to the position of the whole board where the flux is provided, and performing reflow soldering; B6. Punching the entire board to separate the FPC board (1) from the remaining material, thereby obtaining a finished FPC circuit board provided with circuits and components (3).

5. The FPC circuit board manufacturing process according to claim 4, characterized in that: In step B6, the blade used for punching has a cutting edge close to the FPC board (1) and perpendicular to the surface of the FPC board (1).

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