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JP-2026075422-A - Circuit board manufacturing method

JP2026075422AJP 2026075422 AJP2026075422 AJP 2026075422AJP-2026075422-A

Abstract

[Problem] To provide a "circuit board manufacturing method" that allows for the formation of multiple pixel circuits using a film with a thickness of a certain value or more, while also enabling the appropriate connection of the wiring patterns of each pixel circuit with an appropriate amount of liquid metal. [Solution] In the first step, multiple pixel circuits 2 are formed on the PI film 1 with the pixels connected by the wiring pattern 3. In the second-first to second-fourth steps, the PI film 1 is processed to reduce the thickness at the positions between pixels, and the PI film 1 is divided into individual pixel pieces so that the PI film 1 is cut together with the wiring pattern 3 at the positions between pixels. This makes it possible to properly connect the wiring patterns 3 of each pixel circuit 2 with an appropriate amount of liquid metal 6 in the region where the liquid metal 6 is attached between pixels, by making the difference in height between the wiring pattern 3 formed on the pixel circuit 2 and the flexible substrate 5 to which the individual pieces 4 are transferred less than a certain value, thereby enabling the wiring patterns 3 of each pixel circuit 2 to be properly connected with an appropriate amount of liquid metal 6. [Selection Diagram] Figure 1A

Inventors

  • 岸田 克彦

Assignees

  • アルプスアルパイン株式会社

Dates

Publication Date
20260508
Application Date
20241022

Claims (6)

  1. The first step involves forming multiple pixel circuits on a film with the pixels connected by a wiring pattern, A second step involves processing the above film to reduce its thickness at least at the positions between the pixels, and separating the film into individual pixel units such that the film is cut along with the wiring pattern at the positions between the pixels. A third step involves transferring a plurality of individual pixel units, each having the pixel circuit formed on the film, onto a flexible substrate. A method for manufacturing a circuit board, characterized by comprising a fourth step of forming expandable wiring by depositing liquid metal between the wiring patterns cut in the second step.
  2. The second step described above is: An etching process to thin the film by immersing a portion of the film's thickness in an etching solution from the side of the film opposite to the side on which the pixel circuit is formed, A method for manufacturing a circuit board according to claim 1, characterized by comprising a cutting step of cutting the etched film together with the wiring pattern at the positions between the pixels to separate it into pixel units.
  3. The second step described above is: A masking step in which a region including at least a part of the region in which the above wiring pattern between the above pixels is formed is designated as a non-masked region, and a resist is applied to the region excluding the non-masked region. An etching step is performed to partially thin the non-masked area by immersing the portion of the film from the surface on which the pixel circuit is formed to a predetermined thickness of the film in an etching solution, A method for manufacturing a circuit board according to claim 1, comprising a cutting step of cutting the etched film at the positions between the pixels to separate it into individual pixel units.
  4. The above etching process is referred to as the first etching process. The method for manufacturing a circuit board according to claim 3, further comprising a second etching step between the first etching step and the cutting step, in which a portion of the film thickness region is immersed in an etching solution from the side of the film opposite to the side on which the pixel circuit is formed, thereby thinning the film.
  5. The second step described above is: A masking step in which a region including at least a part of the region in which the above wiring pattern between the above pixels is formed is designated as a non-masked region, and a resist is applied to the region excluding the non-masked region. A first etching step involves immersing the portion of the film from the surface on which the pixel circuit is formed to a predetermined thickness of the film in an etching solution to partially thin the non-masked area. A method for manufacturing a circuit board according to claim 1, comprising: a second etching step of thinning the film by immersing the side of the film opposite to the side on which the pixel circuit is formed in the etching solution, in a thickness region that reaches the bottom surface of the region partially thinned in the first etching step, and separating the film at the positions between the pixels to form individual pixel units.
  6. The second step described above is: A masking step in which a region including at least a part of the region in which the above wiring pattern between the above pixels is formed is designated as a non-masked region, and a resist is applied to the region excluding the non-masked region. A method for manufacturing a circuit board according to claim 1, characterized by comprising an etching step of immersing the entire structure, including the film, the pixel circuit, the wiring pattern between pixels, and the resist, in an etching solution, thereby partially thinning the non-masked region of the film from the side on which the pixel circuit is formed, thinning the film from the side opposite to the side on which the pixel circuit is formed, and separating the film at the positions between pixels to form individual pixel units.

Description

This disclosure relates to a method for manufacturing a circuit board. In recent years, the development of flexible devices capable of bending and stretching deformation has been widely advanced. As an example of a circuit board used in a flexible device, a circuit board comprising a base member having elasticity or flexibility, a conductive layer containing a predetermined pattern and liquid metal formed on the base member, and a coating layer laminated on the conductive layer is known (see, for example, Patent Document 1). For example, the circuit board for a stretchable film display using micro-LEDs is manufactured using the procedure shown in Figure 6. First, multiple pixel circuits 102 are formed on the film 101 (first step). For example, a polyimide film (hereinafter referred to as PI film 101) is used for the film 101. At this stage, the multiple pixel circuits 102 formed on the PI film 101 are connected to each other by metal wiring patterns 103. Next, the PI film 101 is cut along with the wiring pattern 103 at the positions between each pixel, thereby separating the PI film 101 into individual pixel pieces (second step). Then, each individual piece 104 is transferred onto a stretchable and flexible rubber substrate 105 (third step). Afterward, stretchable wiring is formed by applying liquid metal 106 to the positions between the wiring patterns 103 on each individual piece 104 (fourth step). Finally, micro LEDs 107 are mounted on the pixel circuits 102 of each individual piece 104 (fifth step). In the fourth step, in order to connect each individual piece 104 with the liquid metal 106, the step difference between the wiring pattern 103 formed on the pixel circuit 102 of each individual piece 104 and the rubber substrate 105 must be smaller than a certain value. If this step difference is large, as shown in Figure 7, the wiring patterns 103 of the pixel circuit 102 on each individual piece 104 will not be connected by the liquid metal 106 due to the influence of the surface tension of the liquid metal 106. Using a thin PI film 101 makes it possible to reduce the step height. However, when the first process is performed using a roll-to-roll method for the purpose of cost reduction or productivity improvement, it is difficult to reduce the thickness of the PI film 101 below a certain value. While it is possible to connect the wiring patterns 103 of each individual piece 104 with liquid metal 106 by increasing the amount of liquid metal 106 introduced in the fourth process after processing the first to third processes using a PI film 101 thicker than a certain value, this leads to the problem of liquid metal 106 overflowing into unnecessary locations on the pixel circuit 102, causing a short circuit. Patent No. 7509980 This is a process diagram showing a method for manufacturing a circuit board according to the first embodiment.This is a process diagram showing a method for manufacturing a circuit board according to the first embodiment.This is a process diagram showing a method for manufacturing a circuit board according to the second embodiment.This is a process diagram showing a method for manufacturing a circuit board according to the second embodiment.This is a process diagram showing a method for manufacturing a circuit board according to a first modified example of the second embodiment.This is a process diagram showing a method for manufacturing a circuit board according to a second modified example of the second embodiment.This is a process diagram showing a method for manufacturing a circuit board according to the third embodiment.This is a process diagram showing a method for manufacturing a circuit board according to the third embodiment.This is a process diagram showing a conventional method for manufacturing circuit boards.This is a diagram to explain the conventional problem. (First embodiment) The first embodiment will be described below with reference to the drawings. Figures 1A and 1B are process diagrams showing the manufacturing method of a circuit board according to the first embodiment. Figures 1A and 1B show the manufacturing process of a circuit board for a stretchable film display using microLEDs, and show a side cross-sectional view of a part of the circuit board. First, as shown in Figure 1A(a), multiple pixel circuits 2 are formed on the film 1 with the pixels connected by a metal wiring pattern 3 (first step). The state of pixels being connected by the wiring pattern 3 means that the wiring pattern 3 connects from the surface of one pixel circuit 2 through its side and across the film 1 between pixels to the adjacent pixel circuit 2. Note that while only two pixel circuits 2 are shown in Figures 1A and 1B, in reality, many more pixel circuits 2 are arranged on the film 1 (the same applies to the figures shown below). For example, polyimide film (hereinafter referred to as PI film 1) is used for film 1, but it is not limited to this. In this first step, multiple pixel circui