Circuit board with embedded resistors and method of manufacturing the same

Abstract

The present application provides a circuit board with embedded resistance and a manufacturing method thereof. The circuit board includes a circuit substrate and a variable resistance region in the circuit substrate. The variable resistance region includes a first resistance layer, a second resistance layer and a liquid metal material. The first resistance layer is electrically connected to the circuit substrate, and the second resistance layer is overlaid on the first resistance layer. The liquid metal material is distributed on the first resistance layer and is electrically connected to the first resistance layer. When the liquid metal material is at an initial temperature, the liquid metal material is separated from the second resistance layer and is not electrically connected to the second resistance layer. When the liquid metal material is at a first temperature, which is higher than the initial temperature, the liquid metal material is electrically connected to the second resistance layer. In this way, the resistance value of the variable resistance region can be adjusted by changing the temperature.

Description

TECHNICAL FIELD

[0001] The present invention relates to a circuit board, and in particular, to a circuit board with embedded resistors and a manufacturing method thereof. BACKGROUND

[0002] The embedded resistor in the circuit board has the advantages of shortening the signal path, reducing the degree of signal interference from the outside world, and improving the signal transmission speed. In addition, it can also improve the wiring density, which is beneficial to reducing the area of the circuit board, so as to provide a more lightweight electronic component. Generally, the resistance value of the embedded resistor is adjusted by changing the length or width of the embedded resistor. Therefore, the resistance value of the embedded resistor provided in the circuit board is usually a fixed value, which limits the application range of the circuit board. SUMMARY

[0003] Therefore, the present invention provides a circuit board with embedded resistors and a manufacturing method thereof, which can adjust the resistance value of the embedded resistor, thereby expanding the application range of the circuit board with embedded resistors.

[0004] The circuit board provided by an embodiment of the present invention includes a circuit substrate and a variable resistor region. The variable resistor region is located in the circuit substrate and includes a first resistor layer electrically connected to the circuit substrate. A second resistor layer is located above the first resistor layer and overlaps the first resistor layer. A liquid metal material is distributed on the first resistor layer and electrically connected to the first resistor layer. When the liquid metal material is at an initial temperature, the liquid metal material is separated from the second resistor layer, and there is no electrical connection between the liquid metal material and the second resistor layer. When the liquid metal material is at a first temperature higher than the initial temperature, the liquid metal material contacts the second resistor layer, and the liquid metal material is electrically connected to the second resistor layer.

[0005] In at least one embodiment of the present invention, the second resistor layer further includes an opening. The opening communicates opposite sides of the second resistor layer and extends to the liquid metal material. When the liquid metal material is at the first temperature, the liquid metal material extends to the opening and is electrically connected to the second resistor layer through the sidewall of the opening.

[0006] In at least one embodiment of the present invention, the variable resistor region further includes a third resistor layer overlapping above the second resistor layer. The second resistor layer is located between the first resistor layer and the third resistor layer. When the liquid metal material is at a second temperature higher than the first temperature, the liquid metal material extends to the third resistor layer through the opening and is electrically connected to the third resistor layer.

[0007] In at least one embodiment of the present application, the circuit board further comprises an insulating material between the second resistive layer and the third resistive layer. The insulating material comprises an opening, and the opening is in communication with the via and the third resistive layer.

[0008] In at least one embodiment of the present application, the circuit board further comprises an insulating material between the second resistive layer and the third resistive layer. The insulating material comprises an opening, and the opening is in communication with the via and the third resistive layer.

[0009] In at least one embodiment of the present application, when the liquid metal material is at a first temperature, a liquid surface of the liquid metal material is between opposite ends of the opening and is separated from the third resistive layer.

[0010] In at least one embodiment of the present application, the liquid metal material comprises a gallium-based alloy.

[0011] In at least one embodiment of the present application, the circuit board further comprises a protective layer in the via of the second resistive layer and covering an inner wall of the via. The second resistive layer is electrically connected to the protective layer.

[0012] In at least one embodiment of the present application, the first resistive layer has a greater resistance value than the second resistive layer.

[0013] In at least one embodiment of the present application, the circuit board further comprises two cover layers respectively disposed on opposite sides of the circuit board and covering the variable resistance region.

[0014] The present application also provides a method for manufacturing a circuit board, comprising providing a first substrate; patterning the first substrate to form a first resistive layer; disposing a second substrate above the first substrate; patterning the second substrate to form a second resistive layer; removing portions of the first substrate and portions of the second substrate to form a recess, the recess being in communication with the first resistive layer and the second resistive layer; and disposing a liquid metal material in the recess and electrically connecting the liquid metal material to the first resistive layer.

[0015] Based on the above, by changing the volume of the liquid metal material at different temperatures, the electrical connection relationship between the resistive layers in the variable resistance region is adjusted, so as to change the resistance value of the circuit board. In this way, the circuit board with embedded resistors has the function of adjustable resistance value, which is beneficial to expand the application range of embedded component circuit boards. BRIEF DESCRIPTION OF DRAWINGS

[0016] Aspects of the application are illustrated by way of example in the following detailed description and in conjunction with the figures. It should be noted that the figures may not be drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or decreased for the sake of discussion.

[0017] Figures 1A-1C Cross-sectional views of a circuit board of an embodiment of the application at different temperatures.

[0018] Figures 2A-2H Cross-sectional views of a flexible circuit board manufacturing method of an embodiment of the application. DETAILED DESCRIPTION

[0019] The present application will be described in detail below with reference to the following embodiments. It should be noted that the following description of the embodiments of the present application is merely intended to illustrate and not to exhaustively disclose all embodiments or limit the specific embodiments of the present application. For example, the description of "a first feature formed on a second feature" includes various embodiments, in which the first feature is in direct contact with the second feature, and in which additional features are formed between the first feature and the second feature such that the two features are not in direct contact. In addition, the same reference numerals are used in the drawings and the description to indicate the same or similar elements as far as possible.

[0020] Spatially relative terms, such as "under", "below", "lower", "above", "upper", and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientations depicted in the figures. The devices can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0021] In the following detailed description of the application, the dimensions (e.g., lengths, widths, thicknesses, and depths) of the elements (e.g., layers, films, substrates, and regions) in the figures are exaggerated for the purpose of explanation and are not meant to be limiting. The following description of the embodiments is not to be limited by the description of the drawings, and the explanation and interpretation of the embodiments should encompass the variations in dimensions, shapes, and both that are caused by, for example, the process and / or tolerances. For example, the flat surfaces illustrated in the figures can have rough and / or nonlinear features, and the sharp corners illustrated in the figures can be replaced with rounded corners. Thus, the elements illustrated in the figures are meant to be illustrative, not exact, and are not meant to limit the claims of the application.

[0022] More specifically, the terms "about," "approximately," or "substantially" as used herein with reference to a particular value or range of values can encompass deviations of up to 30%, 20%, 10%, or 5% from the specified value or range of values, as well as values or ranges of values that would be understood by one of ordinary skill in the art to be equivalent in light of the function of the value or range of values in question. The terms "about," "approximately," or "substantially" as used herein can select an acceptable range of deviation or standard deviation for optical properties, etching properties, mechanical properties, or other properties, and not all of the above properties are to be applied with a single standard deviation.

[0023] A circuit board is disclosed Figure 1A The circuit board 10 includes a circuit substrate 100 and a variable resistance region 120, and the variable resistance region 120 is located in the circuit substrate 100. In this embodiment, the variable resistance region 120 includes a first resistance layer 122, a second resistance layer 124, a third resistance layer 126, and a liquid metal material 128. The circuit substrate 100 includes a circuit layer 102a, a circuit layer 102b, and a circuit layer 102c, and the circuit layers 102a, 102b, and 102c are respectively located on the first resistance layer 122, the second resistance layer 124, and the third resistance layer 126.

[0024] In addition, the circuit substrate 100 includes an insulating layer 104a, an insulating layer 104b, and an insulating layer 104c, and the circuit layers and the insulating layers are respectively located on opposite sides of the resistance layers. Specifically, the circuit layer 102a and the insulating layer 104a are respectively located on opposite sides of the first resistance layer 122, the circuit layer 102b and the insulating layer 104b are respectively located on opposite sides of the second resistance layer 124, and the circuit layer 102c and the insulating layer 104c are respectively located on opposite sides of the third resistance layer 126.

[0025] In this embodiment, the circuit board 100 further includes a pad layer 106, and circuit layers 102b and 102c are located between the pad layer 106 and the circuit layer 102a. In other words, the pad layer 106 and the circuit layer 102a are located on opposite sides of the circuit board 100, while other circuit layers are sandwiched between the pad layer 106 and the circuit layer 102a. On the other hand, the circuit board 100 also includes a plurality of conductive blind vias 107, which are disposed between two adjacent circuit layers. For example, some conductive blind vias 107 are disposed between circuit layers 102a and 102b, and some conductive blind vias 107 are disposed between circuit layers 102b and 102c. In addition, conductive blind vias 107 are also disposed between circuit layer 102c and the pad layer 106.

[0026] It is worth mentioning that, since the circuit layer 102a directly contacts the first resistive layer 122, and the circuit layers 102a, 102b, 102c and the pad layer 106 are electrically connected to each other through the conductive blind via 107, the first resistive layer 122 is electrically connected to the circuit layers 102a, 102b, 102c and the pad layer 106 of the circuit board 100.

[0027] like Figure 1A As shown, the second resistive layer 124 is located above and overlaps the first resistive layer 122. Furthermore, the third resistive layer 126 overlaps the second resistive layer 124, and the second resistive layer 124 is located between the first resistive layer 122 and the third resistive layer 126. On the other hand, the circuit board 100 also includes insulating materials 108a, 108b, and 108c. Insulating material 108a is located between the first resistive layer 122 and the second resistive layer 124, insulating material 108b is located between the second resistive layer 124 and the third resistive layer 126, and insulating material 108c is located between the third resistive layer 126 and the pad layer 106.

[0028] The liquid metal material 128 of the variable resistance region 120 is distributed on the first resistive layer 122. For example... Figure 1A As shown, liquid metal material 128 is disposed within insulating material 108a, and both ends of liquid metal material 128 are respectively connected to insulating layer 104a and insulating layer 104b. Notably, liquid metal material 128 is electrically connected to first resistive layer 122. Liquid metal material 128 can be a gallium-based alloy containing at least one of gallium, indium, tin, zinc, bismuth, antimony, lead, lanthanum, cerium, and neodymium, or a metal alloy that is liquid at room temperature (e.g., gallium indium tin alloy). This material has a low melting point and is liquid at room temperature.

[0029] In the present embodiment, the volume expansion rate of the liquid metal material 128 can fall within a range between 3% and 5%, but the present application is not limited thereto. In various embodiments of the present application, the volume expansion rate of the liquid metal material 128 must meet the size requirement of the variable resistance region 120 so as to achieve the electrical connection of the variable resistance region 120 at a specific temperature. Therefore, the volume expansion rate of the liquid metal material 128 can be selected according to the size requirement of the variable resistance region 120.

[0030] In the present embodiment, the second resistance layer 124 further includes an opening 124h, which communicates opposite sides of the second resistance layer 124. It is worth mentioning that the opening 124h of the present embodiment can also pass through the insulating layer 104b and extend to the liquid metal material 128 so as to communicate the liquid metal material 128 and the side of the second resistance layer 124 opposite to the liquid metal material 128. In other words, the opening 124h penetrates the second resistance layer 124 and the insulating layer 104b and stops at the liquid surface 128i of the liquid metal material 128. On the other hand, the third resistance layer 126 further includes an opening 126h, which communicates opposite sides of the third resistance layer 126. It is worth mentioning that the opening 126h of the present embodiment can also extend to the insulating material 108c.

[0031] In addition, in the present embodiment, the insulating material 108b includes an opening 108p, which communicates the opening 124h and the opening 126h of the third resistance layer 126. In detail, the opening 108p can also pass through the insulating layer 104c and extend toward the surface 126s of the third resistance layer 126 so as to communicate opposite sides of the third resistance layer 126.

[0032] Figures 1A-1C Cross-sectional views of the circuit board 10 at different temperatures are shown respectively. Please refer to Figure 1A When the liquid metal material 128 is at the initial temperature T0, the liquid metal material 128 is separated from the second resistance layer 124. In detail, at the initial temperature T0, the liquid surface 128i of the liquid metal material 128 is located between the surface 122s of the first resistance layer 122 and the surface 124f of the second resistance layer 124, and does not cut the surface 124f. Therefore, the liquid surface 128i of the liquid metal material 128 does not contact the second resistance layer 124, so there is no electrical connection between the liquid metal material 128 and the second resistance layer 124.

[0033] Please refer to Figure 1B When the liquid metal material 128 is at the first temperature T1, which is higher than the initial temperature T0, the volume of the liquid metal material 128 expands due to the temperature rise, thereby extending to the opening 124h of the second resistance layer 124.

[0034] In detail, at the first temperature Tl, the liquid level 128i of the liquid metal material 128 moves upward between the surface 124s of the second resistive layer 124 and the surface 126f of the third resistive layer 126. The portion of the liquid metal material 128 passing through the opening 124h contacts the inner wall (not shown) of the opening 124h and electrically connects the second resistive layer 124 through the inner wall. It should be noted that at this time, the liquid level 128i of the liquid metal material 128 is located between the opposite ends of the opening 108p and is separated from the third resistive layer 126, so the liquid metal material 128 is not electrically connected to the third resistive layer 126.

[0035] In particular, in the present embodiment, the circuit board 10 further comprises a protective layer 140 located in the opening 124h of the second resistive layer 124 and covering the inner wall of the opening 124h. Since the material of the protective layer 140 can comprise, for example, nickel, gold or similar metal materials, the second resistive layer 124 can be electrically connected to the protective layer 140. In this way, the liquid metal material 128 located in the opening 124h can be electrically connected to the second resistive layer 124 through the protective layer 140.

[0036] Please refer to Figure 1C When the liquid metal material 128 is at the second temperature T2, which is higher than the first temperature Tl, the volume of the liquid metal material 128 expands due to the temperature rise, and thus extends to the third resistive layer 126 through the opening 124h of the second resistive layer 124. In detail, when the temperature of the liquid metal material 128 is raised from the initial temperature T0 to the second temperature T2, the volume of the liquid metal material 128 expands and sequentially passes through the opening 124h of the second resistive layer 124, the opening 108p of the insulating material 108b and the opening 126h of the third resistive layer 126, thereby causing the liquid level 128i of the liquid metal material 128 to protrude from the surface 126s of the third resistive layer 126. The portion of the liquid metal material 128 passing through the opening 126h contacts the inner wall (not shown) of the opening 126h and electrically connects the third resistive layer 126 through the inner wall.

[0037] When the circuit board 10 is powered at the initial temperature T0, since at this time only the first resistive layer 122 is electrically connected to the circuit substrate 100, the current passes through the first resistive layer 122 and generates a resistance value R0. When the circuit board 10 is powered at the first temperature Tl, the liquid metal material 128 expands and electrically connects the first resistive layer 122 and the second resistive layer 124. In this way, the current passes through the first resistive layer 122 and the second resistive layer 124, and generates a resistance value Rl.

[0038] In the present embodiment, the resistance value r1 of the first resistance layer 122 is greater than the resistance value r2 of the second resistance layer 124, and the first resistance layer 122 and the second resistance layer 124 are electrically connected in parallel. For example, the resistance value R1 generated after the first resistance layer 122 and the second resistance layer 124 are connected in parallel (i.e., at the first temperature T1) satisfies Therefore, it can be deduced that the resistance value R1 of the circuit board 10 at the first temperature T1 is less than the resistance value R0 at the initial temperature T0.

[0039] However, the resistance values of the resistance layers in the present application are not limited to the above embodiment. In other embodiments, the resistance value r1 of the first resistance layer 122 can also be less than the resistance value r2 of the second resistance layer 124.

[0040] When the circuit board 10 is powered at the second temperature T1, the liquid metal material 128 expands and electrically connects the first resistance layer 122, the second resistance layer 124, and the third resistance layer 126. In this way, the current passes through the first resistance layer 122, the second resistance layer 124, and the third resistance layer 126, and generates a resistance value R2. As described in the above embodiment, the resistance value r1 of the first resistance layer 122 is greater than the resistance value r2 of the second resistance layer 124, which is greater than the resistance value r3 of the third resistance layer 126, and the three are connected in parallel with each other. The resistance value R2 generated after being connected in parallel satisfies Therefore, it can be deduced that the resistance value R2 of the circuit board 10 at the second temperature T2 is less than the resistance value R1 at the first temperature T1, and less than the resistance value R0 at the initial temperature T0.

[0041] It is worth mentioning that the diameters of the openings 124h and 126h fall within the range of 20 μm to 100 μm. In the present embodiment, the width of the opening 108p can be greater than the diameters of the openings 124h and 126h, so as to serve as a buffer space, allowing a portion of the liquid metal material 128 to temporarily reside in the opening 108p when expanding or contracting, so as to improve the stability of the resistance value. In detail, through the buffer space, the liquid metal material 128 must expand to a certain extent before electrically connecting the first resistance layer 122 to the second resistance layer 124. That is, the temperature must change to a certain extent before the resistance value changes.

[0042] The circuit board 10 of the present embodiment further includes two cover layers 160 disposed on opposite sides of the circuit substrate 100 and covering the variable resistance region 120. In addition, the cover layers 160 expose a plurality of pads (not shown) on the pad layer 106. The material of the cover layers 160 can include, for example, an insulating material such as resin.

[0043] Please refer to Figures 2A-2HIts illustration Figure 1A A cross-sectional schematic diagram of the manufacturing method of the circuit board 10. (e.g.) Figure 2A and Figure 2B As shown, firstly, a first substrate 210 is provided, and this first substrate 210 is patterned by photolithography and etching (e.g., copper sulfate etching and alkaline etching) to form a first resistive layer 122. This first resistive layer 122 includes an opening 122p, and this opening 122p can be formed by ablation or a similar method. Next, as... Figure 2C As shown, an insulating material 108a is formed on the first resistive layer 122, and the insulating material 108a exposes the opening 122p of the first resistive layer 122. Next, a second substrate 220 is disposed on the insulating material 108a, and the second substrate 220 covers the opening 122p.

[0044] Please refer to Figure 2D By means of, for example, electroplating, forming a plurality of conductive blind vias 107 on the second substrate 220, so that the first resistive layer 122 on the first substrate 210 is electrically connected to the second substrate 220 through these conductive blind vias 107. Then, as... Figure 2E As shown, the second substrate 220 is patterned by photolithography and etching to form the second resistive layer 124. The second resistive layer 124 overlaps the first resistive layer 122, and there is no electrical connection between the two. After forming the second resistive layer 124, an insulating material 108b is disposed on the second resistive layer 124, and this insulating material 108b includes grooves 108t.

[0045] Please refer to Figure 2F A third substrate 230 is disposed on the insulating material 108b, and the third substrate 230 is patterned to form a third resistive layer 126. For example... Figure 2G As shown, an insulating material 108c is disposed on the third substrate 230, covering the third resistive layer 126. Next, a portion of the second resistive layer 124 and a portion of the third resistive layer 126 are removed by, for example, laser ablation to form openings 124h and 126h. Furthermore, a portion of the insulating material 108b and a portion of the insulating material 108c are removed to extend the openings 124h and 126h. This forms a groove 207, the two ends of which connect the first resistive layer 122, the second resistive layer 124, and the third resistive layer 126.

[0046] Please refer to Figure 2HAfter forming the recess 207, a protective layer 140 is formed on a part of the inner wall (not shown) of the recess 207 by a surface treatment such as electroplating, electroless plating or sputtering. Then, the liquid metal material 128 is arranged in the recess 207 and electrically connected to the first resistance layer 122. After arranging the liquid metal material 128, a third substrate 230 is arranged on the insulating material 108c. The third substrate 230 covers one end of the opening 126h of the third resistance layer 126, so that the liquid metal material 128 is sealed in the recess 207.

[0047] It is particularly mentioned that the first substrate 210, the second substrate 220 and the third substrate 230 can respectively comprise an insulating layer 211, a resistance material layer 213 and a metal layer 215 (shown in Figure 2A ), and the insulating layer 211 and the metal layer 215 are respectively located on opposite sides of the resistance material layer 213. The insulating layer 211 can comprise, for example, polyimide or similar insulating material, the resistance material layer 213 can comprise, for example, nickel-phosphorus alloy (NiP), nickel-chromium alloy (NiCr) or similar metal alloy thin film material, and the metal layer 215 can comprise copper.

[0048] In summary, by changing the volume of the liquid metal material at different temperatures, the resistance layers in the variable resistance region are electrically connected or disconnected, so as to control the resistance value of the variable resistance region in the circuit board. In this way, the circuit board with embedded resistance can have the function of adjustable resistance value, thereby expanding the application range of the circuit board with embedded resistance.

[0049] Although the embodiments of the present application have been disclosed as above, they are not intended to limit the embodiments of the present application, and any person skilled in the art can make some changes and modifications without departing from the spirit and scope of the embodiments of the present application, so the protection scope of the embodiments of the present application shall be subject to the appended claims.

[0050]

Symbol Description

[0051] 10: circuit board

[0052] 100: circuit substrate

[0053] 102a, 102b, 102c: circuit layer

[0054] 104a, 104b, 104c, 211: insulating layer

[0055] 106: pad layer

[0056] 107: conductive blind hole

[0057] 108a, 108b, 108c: insulating material

[0058] 108p, 122p: opening

[0059] 108t, 207: groove

[0060] 120: variable resistance region

[0061] 122: first resistance layer

[0062] 122s, 124f, 124s, 126f, 126s: surface

[0063] 124: second resistance layer

[0064] 124h, 126h: opening

[0065] 126: third resistance layer

[0066] 128: liquid metal material

[0067] 128i: liquid surface

[0068] 140: protective layer

[0069] 160: cover layer

[0070] 210: first substrate

[0071] 213: resistance material layer

[0072] 215: metal layer

[0073] 220: second substrate

[0074] 230: third substrate

Claims

1. A circuit board, characterized by, A circuit board comprising: a circuit substrate; a variable resistance region within the circuit substrate, and the variable resistance region comprising: a first resistance layer electrically connected to the circuit substrate; a second resistance layer above and overlapping the first resistance layer; and a liquid metal material distributed on and electrically connected to the first resistance layer; wherein when the liquid metal material is at an initial temperature, the liquid metal material is separated from the second resistance layer and there is no electrical connection between the liquid metal material and the second resistance layer; wherein when the liquid metal material is at a first temperature higher than the initial temperature, the liquid metal material contacts the second resistance layer and the liquid metal material is electrically connected to the second resistance layer; an opening that communicates opposite sides of the second resistance layer; wherein when the liquid metal material is at the first temperature, the liquid metal material extends to the opening and is electrically connected to the second resistance layer through a sidewall of the opening; a protective layer in the opening of the second resistance layer and covering an inner wall of the opening, wherein the second resistance layer is electrically connected to the protective layer.

2. The circuit board of claim 1, wherein the variable resistance region further comprises: a third resistance layer above and overlapping the second resistance layer, wherein the second resistance layer is between the first resistance layer and the third resistance layer; wherein when the liquid metal material is at a second temperature higher than the first temperature, the liquid metal material extends to the third resistance layer through the opening and is electrically connected to the third resistance layer.

3. The circuit board of claim 2, wherein the circuit substrate comprises: three circuit layers, wherein the circuit layers are respectively on the first resistance layer, the second resistance layer, and the third resistance layer; a via layer, wherein two of the circuit layers are between the via layer and the other of the circuit layers; and a plurality of conductive blind vias disposed between two adjacent ones of the circuit layers and between one of the circuit layers and the via layer, wherein the circuit layers and the via layer are electrically connected to each other through the conductive blind vias.

4. The circuit board of claim 3, wherein the circuit substrate further comprises: an insulating material between the second resistance layer and the third resistance layer, wherein the insulating material comprises an opening that communicates the opening and the third resistance layer.

5. The circuit board of claim 4, wherein when the liquid metal material is at the first temperature, a liquid surface of the liquid metal material is between opposite ends of the opening and is separated from the third resistance layer.

6. The circuit board of claim 1, wherein the liquid metal material comprises a gallium-based alloy.

7. The circuit board of claim 1, wherein the first resistance layer has a resistance value greater than a resistance value of the second resistance layer.

8. The circuit board of claim 1, further comprising: ​ Two cover layers are disposed on opposite sides of the circuit substrate and cover the variable resistance region.

9. A method of manufacturing a circuit board according to any one of the preceding claims 1 to 8, characterized in that, Comprising: providing a first substrate; patterning the first substrate to form a first resistance layer; disposing a second substrate over the first substrate; patterning the second substrate to form a second resistance layer; removing portions of the first substrate and portions of the second substrate to form a recess, wherein the recess communicates the first resistance layer and the second resistance layer; and disposing a liquid metal material in the recess and electrically connecting the liquid metal material to the first resistance layer.

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