ACF-free three-layer circuit structure and manufacturing method thereof
By adopting an ACF-free three-layer circuit structure and using water-based adhesive to replace ACF, the problems of high cost, complex process and poor design flexibility in membrane switch manufacturing are solved, achieving cost reduction, improved yield and flexibility in high-density circuit design.
Patent Information
- Application Number
- CN202511044938.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-29
- Publication Date
- 2025-10-03
AI Technical Summary
In existing membrane switch manufacturing, ACF glue is expensive, the process is complex, and the circuit layout is limited, resulting in high production costs, low yields, and poor design flexibility.
A three-layer circuit structure without ACF is adopted, and ACF is replaced by water glue. It includes an upper PET circuit layer, a middle PET layer and a lower PET circuit layer. Vertical through holes are set in the middle PET layer. The layers are bonded with water glue, combined with single-layer jumper design and through-hole alignment technology to achieve conduction.
The material cost is reduced by more than 40%, the production cycle is shortened, and the yield is increased to 98%, meeting the needs of miniaturized equipment and achieving design flexibility for high-density circuits.
Smart Images
Figure CN120751574A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of membrane switches, and in particular to an ACF-free three-layer circuit structure and a manufacturing method thereof. Background Art
[0002] In membrane switch manufacturing, traditional three-layer circuit structures typically use anisotropic conductive adhesive (ACF) to achieve interlayer conductivity. ACF is an adhesive containing conductive particles. Through a heat-pressing process, the conductive particles form a conductive path in the vertical direction while maintaining insulation in the horizontal direction. However, this technology presents several significant challenges. The first is cost: ACF adhesive itself is expensive, and the lamination process requires specialized equipment (such as a high-precision hot press), significantly increasing production costs. Furthermore, ACF adhesive requires demanding storage conditions (it must be kept cool and dark), further increasing supply chain costs. The second issue is the complex process: ACF lamination requires extremely strict control of temperature, pressure, and time. Any carelessness can lead to uneven distribution of conductive particles, causing short circuits or poor conductivity. For example, a lamination temperature deviation of ±5°C can affect yield. The third issue is structural limitations: ACF's conductivity relies on the vertical alignment of conductive particles, which necessitates reserved lamination areas in the circuit layout, limiting the design flexibility of high-density circuits.
[0003] In view of this, it is necessary to provide an ACF-free three-layer circuit structure and a manufacturing method thereof. Summary of the Invention
[0004] The present invention provides an ACF-free three-layer circuit structure and a manufacturing method thereof, which effectively solves the problems of high cost and complex preparation of the circuit structure of the existing membrane switch.
[0005] The technical solution adopted in the present invention is:
[0006] An ACF-free three-layer circuit structure includes an upper PET circuit layer, a middle PET layer, and a lower PET circuit layer stacked in sequence. The middle PET layer is provided with a plurality of vertical through holes. The upper PET circuit layer and the middle PET layer, as well as the middle PET layer and the lower PET circuit layer are all bonded by water glue.
[0007] Furthermore, the lower PET circuit layer includes a lower PET layer, a first silver paste circuit printed on the lower PET layer, a carbon paste protective layer printed on the PIN end of the first silver paste circuit, a first layer of UV glue and a second layer of UV glue arranged on the first silver paste circuit, a jumper, and a first layer of water glue. The first layer of water glue is provided with a number of No. 1 through holes. The jumper is isolated by the first UV glue and the second UV glue to form a number of cross circuits with the first silver paste circuit. The lower end surface of the first layer of water glue is bonded to the first layer of UV glue, the second layer of UV glue, the first silver paste circuit and the lower PET layer, and the upper end surface of the first layer of water glue is bonded to the lower end surface of the middle layer of PET.
[0008] Furthermore, the upper PET circuit layer includes an upper PET layer, a plurality of silver dots printed on the upper PET layer, and a second layer of water glue. The second layer of water glue is provided with a plurality of No. 2 through holes corresponding to the silver dots and the No. 1 through holes. The aperture of the No. 2 through holes is smaller than the diameter of the silver dots. The second layer of water glue connects the upper PET layer and the middle PET layer.
[0009] A manufacturing method for manufacturing the ACF-free three-layer circuit structure comprises the following steps:
[0010] S1, preparing an upper PET circuit layer, a middle PET layer and a lower PET circuit layer;
[0011] S2, bonding the lower circuit layer and the lower end surface of the middle PET layer;
[0012] S3, bonding the upper end surface of the middle PET layer to the upper PET circuit layer;
[0013] S4, solidifying all layers as a whole to form an ACF-free three-layer circuit structure;
[0014] S5. Post-process the ACF-free three-layer circuit structure.
[0015] Furthermore, the preparation of the lower PET circuit layer in S1 includes: S111, selecting a lower PET layer, and baking the lower PET layer in an oven; S112, printing a first silver paste circuit on the lower PET layer; S113, printing carbon oil at the PIN output end of the first silver paste circuit; S114, printing a first layer of UV glue and a second layer of UV glue on the first silver paste circuit; S115, printing a jumper so that the jumper covers the first UV glue layer and the second UV glue layer and then is connected to the first silver paste circuit; S116, printing a first layer of water glue.
[0016] Furthermore, the step of preparing the upper PET circuit layer in S1 includes S121, selecting an upper PET layer and baking the upper PET layer in an oven; and S122, printing a second silver paste circuit on the upper PET layer.
[0017] Furthermore, the post-processing of the ACF-free three-layer circuit structure in S5 includes S51, hot pressing the ACF-free three-layer circuit structure; S52, affixing adhesive backing and reinforcement sheets to the ACF-free three-layer circuit structure; S53, punching the ACF-free three-layer circuit structure; S54, performing a conductivity test on the ACF-free three-layer circuit structure; S55, performing an appearance inspection on the ACF-free three-layer circuit structure; S56, packaging the ACF-free three-layer circuit structure.
[0018] Furthermore, in step S2, a hot pressing process is used when bonding the upper PET circuit layer to the middle PET layer, with a hot pressing temperature of 80-120°C, a pressure of 0.5-1.2 MPa, and a time of 10-30 seconds; the cured thickness of the second layer of water-based adhesive is 20-50 μm, and the distance between the edge of the second through hole and the edge of the silver dot is 0.1-0.3 mm.
[0019] Furthermore, in step S3, when bonding the lower PET circuit layer to the middle PET layer, the coating thickness of the first layer of water-based adhesive is 25-60 μm, and after bonding, the adhesive is pre-cured by UV with a UV energy of 300-600 mJ / cm 2 ; The aperture of the No. 1 through hole is 0.05-0.15mm larger than that of the No. 2 through hole.
[0020] Furthermore, the hot pressing process in step S4 is divided into two stages. The first stage is: the temperature is 70-90°C, the pressure is 0.3-0.8 MPa, and the time is 5-15 seconds, which is used to preliminarily fix the three-layer structure; the second stage is: the temperature is 100-130°C, the pressure is 1.0-1.5 MPa, and the time is 20-40 seconds to ensure that the water-based adhesive is completely cured; the interlayer peel strength after hot pressing is ≥5N / cm.
[0021] Beneficial effects of the invention:
[0022] 1. By replacing ACF with water-based adhesive, the cost of ACF conductive silver adhesive is reduced, and the material cost is reduced by more than 40% (the unit price of water-based adhesive is only 1 / 5 of ACF). At the same time, the investment in ACF pressing equipment is eliminated, and the overall manufacturing cost is reduced by 25%-30%.
[0023] 2. Eliminate multiple processes such as ACF bonding, pre-pressing, and main pressing, shorten the production cycle, and increase the yield rate to more than 98% (the yield rate of traditional processes is about 90%).
[0024] 3. The single-layer jumper design and through-hole alignment technology can achieve precise correspondence between silver dots and silver paste circuits to meet the needs of miniaturized equipment.
[0025] 4. The entire manufacturing method involves the manufacture of a three-layer circuit structure without ACF and subsequent testing to ensure the product yield. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Figure 1 An exploded diagram of an ACF-free three-layer circuit structure provided in an embodiment of the present application.
[0027] Figure 2 A flowchart of a manufacturing method provided in an embodiment of the present application.
[0028] The markings in the figure are: 1. Lower PET layer; 2. First silver paste circuit; 3. Carbon paste protective layer; 4. First layer of UV glue; 5. Second layer of UV glue; 6. Jumper; 7. Upper PET layer; 8. Silver dots; 9. Second layer of water glue; 10. First layer of water glue; 11. Middle PET layer. DETAILED DESCRIPTION
[0029] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.
[0030] like Figure 1 As shown, the first embodiment provided by the present application is an ACF-free three-layer circuit structure, including an upper PET circuit layer, a middle PET layer 11 and a lower PET circuit layer stacked in sequence, the middle PET layer 11 is provided with a plurality of vertical through holes, and the upper PET circuit layer and the middle PET layer 11, and the middle PET layer 11 and the lower PET circuit are all bonded by water glue.
[0031] In the above design, the ACF-free three-layer circuit structure of this application uses water-based adhesive bonding to ensure a tight bond between the layers, improving circuit stability. The middle PET layer 11 acts as an insulator to prevent short circuits. The overall structure is lightweight and thin, suitable for a variety of electronic devices, and improves product performance.
[0032] Specifically: the lower PET circuit layer includes a lower PET layer 1, a first silver paste circuit 2 printed on the lower PET layer 1, a carbon paste protective layer 3 printed on the PIN end of the first silver paste circuit 2, a first layer of UV glue 4 and a second layer of UV glue 5 arranged on the first silver paste circuit 2, a jumper 6, and a first layer of water glue 10. The first layer of water glue 10 is provided with a number of No. 1 through holes. The jumper 6 is isolated by the first layer of UV glue 4 and the second layer of UV glue 5 to form a number of cross circuits with the first silver paste circuit 2. The lower end surface of the first layer of water glue 10 is bonded to the first layer of UV glue 4, the second layer of UV glue 5, the first silver paste circuit 2 and the lower PET layer 1, and the upper end surface of the first layer of water glue 10 is bonded to the lower end surface of the middle layer of PET.
[0033] In actual application, the carbon paste protective layer 3 can prevent the PIN end of the first silver paste circuit 2 from being oxidized. After the keycap of the keyboard is pressed, the upper PET circuit layer is pressed, and the area of the jumper 6 except the end is insulated from the first silver paste circuit 2 by the first UV glue and the second UV glue, so that the two ends of the jumper 6 are connected to the first silver paste circuit 2, and the upper PET circuit layer passes through the middle layer PET and then through the No. 1 through hole to be connected to the first silver paste circuit 2.
[0034] In the above design, the design of the lower PET circuit layer can effectively cooperate with the middle PET layer to ensure that the upper PET circuit layer and the lower PET circuit layer are conductive when the membrane switch is pressed.
[0035] Specifically: the upper PET circuit layer includes an upper PET layer 7, a plurality of silver dots 8 printed on the upper PET layer 7, and a second layer of water glue 9. The second layer of water glue 9 is provided with a plurality of No. 2 through holes corresponding to the silver dots 8 and the No. 1 through holes. The aperture of the No. 2 through holes is smaller than the diameter of the silver dots 8. The second layer of water glue 9 connects the upper PET layer 7 and the middle layer of PET.
[0036] In actual use, several silver dots 8 correspond to key positions on the membrane switch. When the keycap is pressed, the upper PET layer 7 pushes down on the corresponding silver dot 8. After the silver dot 8 passes through the second through-hole, the vertical through-hole contacts the first silver paste circuit 2 corresponding to the first through-hole, thus achieving circuit continuity. When the keycap is no longer pressed, the upper PET layer 7 drives the corresponding silver dot 8 back to its original position and breaks contact with the first silver paste circuit 2, disconnecting the circuit of the corresponding keycap.
[0037] In the above design, the structural design and specific implementation of the upper PET circuit layer facilitate the correspondence between the upper PET circuit layer and the middle PET layer 11.
[0038] The second embodiment provided by the present application is an ACF-free three-layer circuit structure, comprising an upper PET circuit layer, a middle PET layer 11 and a lower PET circuit layer stacked in sequence, the middle PET layer 11 being provided with a number of vertical through holes, the lower PET circuit layer comprising a lower PET layer 1, a first silver paste circuit 2 printed on the lower PET layer 1, a carbon paste protective layer 3 printed on the PIN end of the first silver paste circuit 2, a first layer of UV glue 4 and a second layer of UV glue 5 provided on the first silver paste circuit 2, a jumper 6, and a first layer of water glue 10, the first layer of water glue 10 being provided with a number of No. 1 through holes, the jumper 6 being isolated by the first UV glue and the second UV glue to form a number of cross circuits with the first silver paste circuit 2, the lower end face of the first layer of water glue 10 being bonded to the first layer of UV glue 4, the second layer of UV glue 5, the first silver paste circuit 2 and the lower PET layer 1, and the upper end face of the first layer of water glue 10 being bonded to the lower end face of the middle layer of PET. The upper PET circuit layer includes an upper PET layer 7, several silver dots 8 printed on the upper PET layer 7, and a second layer of water glue 9. The second layer of water glue 9 is provided with several No. 2 through holes corresponding to the silver dots 8 and the No. 1 through holes. The aperture of the No. 2 through holes is smaller than the diameter of the silver dots 8. The second layer of water glue 9 connects the upper PET layer 7 and the middle layer of PET.
[0039] In this design, the ACF-free three-layer circuit structure utilizes water-based adhesive bonding to ensure a tight bond between layers, enhancing circuit stability. The middle PET layer 11 provides insulation, preventing short circuits. The overall structure is lightweight and suitable for a variety of electronic devices, enhancing product performance. The structural design and specific implementation of the upper PET circuit layer facilitate alignment between the upper PET circuit layer and the middle PET layer 11.
[0040] like Figure 2 As shown, the third embodiment provided by the present application is a manufacturing method for manufacturing the ACF-free three-layer circuit structure, comprising the following steps:
[0041] S1, preparing an upper PET circuit layer, a middle PET layer 11 and a lower PET circuit layer;
[0042] S2, bonding the lower circuit layer and the lower end surface of the middle PET layer 11;
[0043] S3, bonding the upper end surface of the middle PET layer 11 to the upper PET circuit layer;
[0044] S4, solidifying all layers as a whole to form an ACF-free three-layer circuit structure;
[0045] S5. Post-process the ACF-free three-layer circuit structure.
[0046] In the above design, the manufacturing method processes the upper PET circuit layer, the middle PET layer 11 and the lower PET circuit layer separately and then assembles them, canceling the ACF design, eliminating the process of assembling ACF, saving process steps, and improving assembly efficiency.
[0047] Specifically, the preparation of the lower PET circuit layer in S1 includes: S111, selecting the lower PET layer 1, and baking the lower PET layer 1 in an oven; S112, printing the first silver paste circuit 2 on the lower PET layer 1; S113, printing carbon oil at the PIN output end of the first silver paste circuit 2; S114, printing the first layer of UV glue 4 and the second layer of UV glue 5 on the first silver paste circuit 2; S115, printing the jumper 6 so that the jumper 6 covers the first UV glue layer and the second UV glue layer and then conducts with the first silver paste circuit 2; S116, printing the first layer of water glue 10.
[0048] In the above design, baking the lower PET layer 1 in an oven can prevent the lower PET layer 1 from thermal expansion and contraction in subsequent processes. The first silver paste circuit 2, carbon oil, the first layer of UV glue 4 and the second layer of UV glue 5 are set by printing, which is more environmentally friendly than development and etching.
[0049] Specifically, the preparation of the upper PET circuit layer in S1 includes S121, selecting the upper PET layer 7, and baking the upper PET layer 7 in an oven; S122, printing the second silver paste circuit on the upper PET layer 7.
[0050] In the above design, the upper PET circuit layer prepared by the manufacturing method of the upper PET circuit layer can save the etching process, which has environmental benefits.
[0051] Specifically: the post-processing of the ACF-free three-layer circuit structure in S5 includes S51, hot pressing the ACF-free three-layer circuit structure; S52, affixing backing adhesive and a reinforcement sheet to the ACF-free three-layer circuit structure; S53, punching the ACF-free three-layer circuit structure; S54, performing a conductivity test on the ACF-free three-layer circuit structure; S55, performing an appearance inspection on the ACF-free three-layer circuit structure; S56, packaging the ACF-free three-layer circuit structure.
[0052] In the above design, hot pressing during post-processing ensures stronger connections between the three-layer structure, meeting user requirements. Applying adhesive backing and reinforcement sheets to the ACF-free three-layer circuit structure enhances overall product strength. Punching is performed to achieve the desired dimensions. Conductivity testing ensures product performance. Appearance inspection ensures that any defects are promptly and effectively screened.
[0053] Specifically: in the step S2, when bonding the upper PET circuit layer and the middle PET layer 11, a hot pressing process is adopted, the hot pressing temperature is 80-120°C, the pressure is 0.5-1.2 MPa, and the time is 10-30 seconds; the cured thickness of the second layer of water glue 9 is 20-50 μm, and the distance between the edge of the No. 2 through hole and the edge of the silver dot 8 is 0.1-0.3 mm.
[0054] In the above design, the hot pressing process maintains a temperature of 80-120°C to ensure the adhesive is molten, a pressure of 0.5-1.2 MPa, and a duration of 10-30 seconds to ensure adhesion between the layers. The cured thickness of the second layer of adhesive 9 is 20-50 μm, and the distance between the edge of the second through-hole and the edge of the silver dot 8 is 0.1-0.3 mm, ensuring that the silver dot 8 maintains contact and conductivity with the underlying PET circuit layer when pressed.
[0055] Specifically, in step S3, when bonding the lower PET circuit layer to the middle PET layer 11, the coating thickness of the first layer of water glue 10 is 25-60 μm, and after bonding, it is subjected to UV pre-curing treatment with a UV energy of 300-600 mJ / cm 2 The aperture of the No. 1 through hole is 0.05-0.15 mm larger than that of the No. 2 through hole to achieve precise alignment of the upper and lower layer circuits.
[0056] In the above design, effective connection between the lower PET circuit layer and the middle PET circuit layer can be achieved, while ensuring that the silver dots 8 of the upper PET circuit layer and the first silver paste circuit 2 of the lower PET circuit layer are effectively and accurately aligned.
[0057] Specifically, the hot pressing process in step S4 is divided into two stages. The first stage is: the temperature is 70-90°C, the pressure is 0.3-0.8 MPa, and the time is 5-15 seconds, which is used to preliminarily fix the three-layer structure; the second stage is: the temperature is 100-130°C, the pressure is 1.0-1.5 MPa, and the time is 20-40 seconds to ensure that the water-based adhesive is completely cured; the interlayer peel strength after hot pressing is ≥5N / cm.
[0058] In the above design, the hot pressing process is divided into two steps. The first step is to preliminarily fix the three-layer structure, and the second step is to finally solidify the positioned three-layer structure to ensure the assembly accuracy of the three-layer structure.
[0059] To explain in further detail, it should be understood that the above is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.
Claims
1. An ACF-free three-layer circuit structure, characterized by: The invention comprises an upper PET circuit layer, a middle PET layer (11) and a lower PET circuit layer stacked in sequence, wherein the middle PET layer (11) is provided with a plurality of vertical through holes, and the upper PET circuit layer and the middle PET layer (11), and the middle PET layer (11) and the lower PET circuit layer are all bonded by water glue.
2. The ACF-free three-layer circuit structure according to claim 1, characterized in that: The lower PET circuit layer comprises a lower PET layer (1), a first silver paste circuit (2) printed on the lower PET layer (1), a carbon paste protective layer (3) printed on the PIN end of the first silver paste circuit (2), a first layer of UV glue (4) and a second layer of UV glue (5) arranged on the first silver paste circuit (2), a jumper (6), and a first layer of water glue (10). The first layer of water glue (10) is provided with a plurality of No. 1 through holes. The jumper (6) is isolated by the first layer of UV glue (4) and the second layer of UV glue (5) to form a plurality of cross circuits with the first silver paste circuit (2). The lower end surface of the first layer of water glue (10) is bonded to the first layer of UV glue (4), the second layer of UV glue (5), the first silver paste circuit (2) and the lower PET layer (1). The upper end surface of the first layer of water glue (10) is bonded to the lower end surface of the middle PET layer.
3. The ACF-free three-layer circuit structure according to claim 1, wherein: The upper PET circuit layer comprises an upper PET layer (7), a plurality of silver dots (8) printed on the upper PET layer (7), and a second layer of water glue (9); the second layer of water glue (9) is provided with a plurality of second through holes corresponding to the silver dots (8) and the first through holes; the aperture of the second through holes is smaller than the diameter of the silver dots (8); the second layer of water glue (9) connects the upper PET layer (7) and the middle PET layer.
4. A manufacturing method for manufacturing the ACF-free three-layer circuit structure according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1, preparing an upper PET circuit layer, a middle PET layer (11) and a lower PET circuit layer; S2, bonding the lower circuit layer and the lower end surface of the middle PET layer (11); S3, bonding the upper end surface of the middle PET layer (11) to the upper PET circuit layer; S4, solidifying all layers as a whole to form an ACF-free three-layer circuit structure; S5. Post-process the ACF-free three-layer circuit structure.
5. The manufacturing method according to claim 4, characterized in that: The preparation of the lower PET circuit layer in S1 comprises: S111, selecting a lower PET layer (1), and baking the lower PET layer (1) in an oven; S112, printing a first silver paste circuit (2) on the lower PET layer (1); S113, printing carbon oil at the PIN output end of the first silver paste circuit (2); S114, printing a first layer of UV glue (4) and a second layer of UV glue (5) on the first silver paste circuit (2); S115, printing a jumper (6) so that the jumper (6) covers the first UV glue layer and the second UV glue layer and is then connected to the first silver paste circuit (2); S116, printing a first layer of water glue (10).
6. The manufacturing method according to claim 4, wherein: The preparation of the upper PET circuit layer in S1 includes S121, selecting an upper PET layer (7), and baking the upper PET layer (7) in an oven; S122, printing a second silver paste circuit on the upper PET layer (7).
7. The manufacturing method according to claim 4, wherein: The post-processing of the ACF-free three-layer circuit structure in S5 includes S51, hot pressing the ACF-free three-layer circuit structure; S52, affixing backing adhesive and a reinforcement sheet to the ACF-free three-layer circuit structure; S53, punching the ACF-free three-layer circuit structure; S54, performing a conductivity test on the ACF-free three-layer circuit structure; S55, performing an appearance inspection on the ACF-free three-layer circuit structure; S56, packaging the ACF-free three-layer circuit structure.
8. The manufacturing method according to claim 4, wherein: In the step S2, when bonding the upper PET circuit layer and the middle PET layer (11), a hot pressing process is adopted, the hot pressing temperature is 80-120°C, the pressure is 0.5-1.2MPa, and the time is 10-30 seconds; the cured thickness of the second layer of water glue (9) is 20-50μm, and the distance between the edge of the second through hole and the edge of the silver dot (8) is 0.1-0.3mm.
9. The manufacturing method according to claim 4, wherein: In the step S3, when bonding the lower PET circuit layer to the middle PET layer (11), the coating thickness of the first layer of water glue (10) is 25-60 μm, and after bonding, it is subjected to UV pre-curing treatment with a UV energy of 300-600 mJ / cm 2 ; The aperture of the No. 1 through hole is 0.05-0.15mm larger than that of the No. 2 through hole.
10. The manufacturing method according to claim 8, characterized in that: The hot pressing process in step S4 is divided into two stages: the first stage: the temperature is 70-90°C, the pressure is 0.3-0.8 MPa, and the time is 5-15 seconds, which is used to initially fix the three-layer structure; the second stage: the temperature is 100-130°C, the pressure is 1.0-1.5 MPa, and the time is 20-40 seconds to ensure that the water-based adhesive is completely cured; the interlayer peel strength after hot pressing is ≥5N / cm.