TW201804886A - Wiring substrate for fingerprint sensor - Google Patents

Abstract

A wiring substrate 100 for fingerprint sensor of this disclosure including an insulating substrate 1 formed by laminating a plurality of insulating layers 1a and 1b, a plurality of surface layer strip electrodes 6 for fingerprint reading formed on the uppermost insulating layer 1b and disposed in parallel along a first direction, a plurality of inner layer strip electrodes 8 for fingerprint reading formed on next insulating layer 1a in contact with the uppermost insulating layer 1b and are disposed in parallel along a second direction orthogonal to the first direction, a pad electrode 7 formed on the uppermost insulating layer 1b and disposed on the inner layer strip electrodes 8 and between the adjacent surface layer strip electrodes 6, and a via conductor 9 for electrically connecting the pad electrode 7 and the inner layer strip electrode 8, wherein the via conductor 9 is an oval shape longer in the first direction in top view.

Description

Wiring substrate for fingerprint sensor

The present disclosure relates to a wiring substrate for a fingerprint sensor.

A conventional wiring substrate for a fingerprint sensor is composed of a substrate, a wiring conductor covering the surface of the substrate, and a solder resist layer covering the surface of the wiring conductor (JP-A-2001-46359).

The wiring substrate for a fingerprint sensor of the present invention includes: an insulating substrate in which a plurality of insulating layers are laminated; and a plurality of surface layer strip electrodes for fingerprint reading are formed on the insulating layer of the uppermost layer, along the first The direction is arranged side by side; a plurality of inner strip electrodes for fingerprint reading are formed on the insulating layer of the sub-layer in contact with the uppermost insulating layer, along a second direction orthogonal to the first direction Side by side; pad electrodes are formed on the uppermost insulating layer, disposed on the inner strip electrodes and adjacent to the surface strip electrodes; and via conductors The electrode is electrically connected to the inner strip electrode. The via-hole conductor has an elongated shape that is long in the first direction in plan view.

1‧‧‧Insert substrate

1a, 1b‧‧‧ insulation

2, 2a, 2b, 2c, 2d‧‧‧ wiring conductor

3‧‧‧ solder mask

4‧‧‧through hole

5‧‧‧ Guide hole

5a‧‧‧Guide

6‧‧‧Surface strip electrode

7‧‧‧Pad electrode

8‧‧‧ Inner layer strip electrode

9‧‧‧ Guide hole conductor

10‧‧‧External connection pads

21‧‧‧Support substrate

22‧‧‧ Carrier copper foil

23‧‧‧ copper foil

24‧‧‧with carrier copper foil

100, 100'‧‧‧Wiring substrate for fingerprint sensor

FIG. 1 is a schematic cross-sectional view showing an example of an embodiment of a wiring substrate for a fingerprint sensor according to the present disclosure.

FIG. 2 is a plan view showing a surface strip electrode and a pad electrode in an example of the embodiment of the wiring substrate for a fingerprint sensor of the present disclosure.

FIG. 3 is a plan view showing an inner layer strip electrode in an example of the embodiment of the wiring substrate for a fingerprint sensor of the present disclosure.

FIG. 4 is a plan view showing a state in which the surface layer strip electrode and the pad electrode and the inner layer strip electrode are vertically overlapped in the example of the embodiment of the wiring substrate for a fingerprint sensor of the present disclosure.

Fig. 5 is a schematic cross-sectional view showing another example of the embodiment of the wiring substrate for a fingerprint sensor of the present disclosure.

6A to 6E are schematic cross-sectional views for explaining each step of the method of manufacturing the wiring substrate for a fingerprint sensor shown in Fig. 5.

7F to 7J are schematic cross-sectional views for explaining each step of the method of manufacturing the wiring substrate for a fingerprint sensor shown in Fig. 5.

An example of an embodiment of the wiring substrate for a fingerprint sensor of the present disclosure will be described with reference to FIGS. 1 to 4 . As shown in FIG. 1, the wiring board 100 of this example is provided with the insulating substrate 1, the wiring conductor 2, and the soldering resist layer 3.

樹脂等。熱固化性樹脂之中分散有氫氧化鋁、二氧化矽等的無機絕緣物填料。 The insulating substrate 1 is formed by laminating an insulating layer 1b on the upper and lower surface areas of the core insulating layer 1a. The core insulating layer 1a is made of, for example, a thermosetting resin to which a glass cloth is added. The build-up insulating layer 1b is made of, for example, a thermosetting resin having no glass cloth. As the thermosetting resin for these insulating layers, epoxy resin, bismaleimide III is used.

Resin, etc. An inorganic filler filler such as aluminum hydroxide or cerium oxide is dispersed in the thermosetting resin.

The core insulating layer 1a has a thickness of 30 to 400 μm. A plurality of through holes 4 are formed in the core insulating layer 1a. The diameter of the through hole 4 is about 70 to 100 μm. The buildup insulating layer 1b has a thickness of 10 to 20 μm. A plurality of via holes 5 are formed in the build-up insulating layer 1b. The diameter of the guide hole 5 is 20 to 70 μm.

The wiring conductor 2 is coated on the upper and lower surfaces of the core insulating layer 1a and the through hole 4, and on the surface of the build-up insulating layer 1b and the via hole 5. The wiring conductor 2 is made of, for example, copper plating. The thickness of the wiring conductor 2 is 10 to 20 μm in the case of the wiring conductor covering the upper and lower surfaces of the core insulating layer 1a, and is 5 to 50 μm in the case of the wiring conductor covering the surface of the build-up insulating layer 1b.

A part of the wiring conductor 2 covered on the surface of the build-up insulating layer 1b on the upper surface side forms the surface strip electrode 6 for fingerprint reading. As shown in Fig. 2, the surface strip electrode 6 has a thin stripe pattern having lands 6a at its ends, and a plurality of surface strip electrodes 6 are arranged in parallel along the first direction. The strip-shaped pattern portion of the surface strip electrode 6 has a width of about 5 to 20 μm, and the interval between the strip-shaped pattern portions adjacent to each other is about 50 to 65 μm.

A part of the wiring conductor 2 covered on the surface of the build-up insulating layer 1b on the upper surface side has a plurality of pad electrodes 7 between the surface strip electrodes 6. Dimension of the pad electrode 7 along the first direction The size is about 40 to 65 μm, the size in the second direction orthogonal thereto is about 30 to 45 μm, and the distance from the surface strip electrode 6 is 10 to 20 μm. This pad electrode 7 is located on the inner layer strip electrode 8 which will be described later. The pad electrode 7 has an oblong shape with a short diameter of 20 to 40 μm and a long diameter of 30 to 60 μm. The pad electrode 7 is connected to the inner strip electrode 8 via a via conductor 9 filled in an elongated circular via 5a that is long in the first direction.

The pad electrode 7 is an oblong shape having the same or similar shape as the via-hole conductor 9. Preferably, the via-hole conductor 9 has an elliptical shape having a short diameter and a small diameter smaller than that of the pad electrode 7. The pad electrode 7 preferably has a short diameter of 20 to 25 μm and a long diameter of 30 to 40 μm. Further, it is preferable that the entire upper surface of the via conductor 9 is covered on the pad electrode 7.

Further, in the present disclosure, the concept of an oblong shape includes not only the shape shown in FIG. 2 but also an elliptical shape and an egg shape.

As shown in Fig. 1, a part of the wiring conductor 2 covered on the upper surface of the core insulating layer 1a forms an inner layer strip electrode 8 for fingerprint reading. As shown in Fig. 3, the inner layer strip electrode 8 has a thin stripe pattern having lands 8a at the end portions, and is arranged in parallel along the second direction at right angles to the first direction. The strip-shaped pattern portion of the inner layer strip electrode 8 has a width of about 30 to 65 μm, and the interval between the adjacent strip-shaped patterns is about 15 to 40 μm.

As shown in Fig. 4, the surface strip electrode 6 and the inner strip electrode 8 are vertically overlapped so as to intersect each other in the direction orthogonal to each other. The horizontal interval between the pad electrode 7 and the surface strip electrode 6 is 5 to 20 μm.

As shown in Figure 1, the build-up insulating layer on the lower surface side A part of the wiring conductor 2 covered by the surface of 1b forms the external connection pad 10. The external connection pad 10 is a circle having a diameter of 200 to 500 μm. The predetermined members of the external connection pad 10 and the surface strip electrode 6 and the inner layer strip electrode 8 are electrically connected to each other via the wiring conductor 2.

The solder resist layer 3 is coated so as to cover the build-up insulating layer 1b on the upper surface side and the lower surface side and the wiring conductor 2 on the surface thereof. The solder resist layer 3 is composed of a thermosetting resin. The cerium oxide powder is dispersed as a filler in the solder resist layer 3. The thickness of the solder resist layer 3 is about 5 to 20 μm on the surface of the wiring conductor 2. The solder resist layer 3 on the upper surface side completely covers the wiring conductor 2. The solder resist layer 3 on the lower surface side has an opening portion through which the external connection pads 10 are exposed.

When a finger is placed on the upper surface of the fingerprint sensor wiring substrate 100 to apply a voltage to the surface strip electrode 6, the surface strip electrode 6 and the finger are opposed to each other via the solder resist layer 3 on the upper surface side. An electrostatic capacitance is formed between the surfaces. The electrostatic capacitance is larger at the convex portion of the fingerprint and smaller at the concave portion of the fingerprint. By sequentially applying a voltage to a plurality of surface strip electrodes 6 and a plurality of inner strip electrodes 7 and scanning them, the difference in electrostatic capacitance is detected and processed by an external processor to thereby read out fingerprint.

Further, in the wiring substrate 100 for a fingerprint sensor, the pad electrode 7 electrically connected to the inner strip electrode 8 via the via conductor 9 is disposed between the surface strip electrodes 6. Therefore, the electrostatic coupling between the surface strip electrode 6 and the inner strip electrode 8 is enhanced, and the sensitivity of fingerprint reading is improved. Further, since the pad electrode 7 is connected to the inner strip electrode 8 The via-hole conductor 9 is formed in an elongated shape that is long in the first direction along the surface strip electrode 6 in plan view, and therefore the opposing area of the via-hole conductor 9 and the surface strip electrode 6 becomes large. As a result, the electrostatic coupling between the surface strip electrode 6 and the inner strip electrode 8 is further enhanced. Thereby, it is possible to provide the wiring substrate 100 for a fingerprint sensor which can further improve the sensitivity of fingerprint reading.

The present disclosure is not limited to the examples of the above-described embodiments, and various modifications can be made without departing from the scope of the present invention. Fig. 5 shows another example of the embodiment of the wiring substrate for a fingerprint sensor of the present disclosure. In the same manner as in the above-described embodiment, the same portions as those in the above-described embodiment are denoted by the same reference numerals, and the detailed description thereof will be omitted.

The example shown in Fig. 5 is different from the example of the embodiment shown in Fig. 1 in that the surface strip electrode 6 and the pad electrode 7 are buried in the upper surface of the uppermost insulating layer 1b. Preferably, the upper surface of the buried surface strip electrode 6 and the pad electrode 7 is 0.1 to 3 μm lower than the upper surface of the uppermost insulating layer 1b of the insulating substrate 1.

The upper surface of the surface strip electrode 6 and the pad electrode 7 is buried on the upper surface of the uppermost insulating layer 1b of the insulating substrate 1 so as to be 0.1 to 3 μm lower than the upper surface of the uppermost insulating layer 1b. In this case, even if the thickness of the solder resist layer 3 covering the surface strip electrode 6 and the pad electrode 7 is a thin thickness of, for example, 6 μm or less, the unevenness on the surface of the solder resist layer 3 can be made flat at 2 μm or less. shape. Thus, the thickness of the solder resist layer 3 covering the surface strip electrode 6 and the pad electrode 7 is 6 μm. In the following, it is thin and the unevenness of the surface is a flat shape of 2 μm or less, whereby the detection sensitivity and the detection accuracy of the fingerprint can be made good.

A method of manufacturing the wiring substrate 100' for a fingerprint sensor will be described with reference to Figs. 6 and 7. In addition, in the sixth and seventh drawings, the fingerprint sensor wiring board 100' shown in Fig. 5 is manufactured in a state in which the wiring board 100' is turned upside down.

First, as shown in FIG. 6A, a member to which the carrier copper foil 24 is attached is formed on the upper surface area of the flat support substrate 21. The support substrate 21 is, for example, an epoxy resin sheet to which a glass cloth is added. The carrier copper foil 24 is obtained by laminating the carrier copper foil 22 and the copper foil 23 so as to be peelable from each other.

Next, as shown in FIG. 6B, the wiring conductor 2a is formed on the surface of the copper foil 23. The wiring conductor 2a includes a surface strip electrode 6 and a pad electrode 7. The wiring conductor 2a is formed by a well-known semi-additive method.

Next, as shown in FIG. 6C, the insulating layer 1b is layered on the surface areas of the copper foil 23 and the wiring conductor 2. In the insulating layer 1b, a plurality of via holes 5 including via holes 5a are formed by laser processing.

Next, as shown in FIG. 6D, the wiring conductor 2b of the sub-layer is formed on the surface of the insulating layer 1b and the via hole 5.

Next, as shown in FIG. 6E, the surface layer insulating layer 1a of the insulating layer 1b of the wiring conductor 2b and the wiring conductor 2c of the sub-layer are formed.

Next, as shown in FIG. 7F, wiring conductors are formed The surface of the insulating layer 1a of 2c forms the insulating layer 1b and the wiring conductor 2d.

Next, as shown in Fig. 7G, the solder resist layer 3 on the lower surface side is formed on the surface of the insulating layer 1b on which the wiring conductor 2d is formed.

Next, as shown in Fig. 7H, the carrier copper foil 22 and the copper foil 23 are peeled off to remove the support substrate 21 and the carrier copper foil 22.

Next, as shown in Fig. 7I, the copper foil 23 is removed by etching, so that the surface strip electrode 6 and the pad electrode 7 are exposed. At this time, the surface of the surface strip electrode 6 and the pad electrode 7 is also slightly etched by etching, so that the exposed surface of the surface strip electrode 6 and the pad electrode 7 is recessed by 0.1 to 3 μm from the surface of the insulating layer 1b. .

Finally, as shown in Fig. 7J, the solder resist layer 3 is covered on the surface of the insulating layer 1b and the wiring conductor 2 (2a), whereby the wiring substrate 100' for fingerprint sensor is completed.

1‧‧‧Insert substrate

1a, 1b‧‧‧ insulation

2‧‧‧Wiring conductor

3‧‧‧ solder mask

4‧‧‧through hole

5‧‧‧ Guide hole

5a‧‧‧Guide

6‧‧‧Surface strip electrode

7‧‧‧Pad electrode

8‧‧‧ Inner layer strip electrode

9‧‧‧ Guide hole conductor

10‧‧‧External connection pads

100‧‧‧Wiring substrate for fingerprint sensor

Claims (10)

A wiring substrate for a fingerprint sensor, comprising: an insulating substrate, wherein a plurality of insulating layers are laminated; and a plurality of surface layer strip electrodes for fingerprint reading are formed on the insulating layer of the uppermost layer, along the first The direction is arranged side by side; a plurality of inner strip electrodes for fingerprint reading are formed on the insulating layer of the sub-layer in contact with the uppermost insulating layer, along a second direction orthogonal to the first direction Side by side; pad electrodes are formed on the uppermost insulating layer, disposed on the inner strip electrodes and adjacent to the surface strip electrodes; and via conductors The electrode is electrically connected to the inner strip electrode, and the via conductor is an elliptical shape that is long in the first direction in plan view. The wiring board for a fingerprint sensor according to the first aspect of the invention, wherein the pad electrode has an elongated shape that is long in the first direction in plan view, and has the same shape as the via hole conductor or Similar shape. The wiring board for a fingerprint sensor according to the second aspect of the invention, wherein the via-hole conductor has an elliptical shape having a short diameter and a long diameter smaller than that of the pad electrode. The wiring substrate for a fingerprint sensor according to any one of claims 1 to 3, wherein the upper surface of the via conductor is The body is covered on the aforementioned pad electrode. The wiring board for a fingerprint sensor according to any one of the first aspect, wherein the surface layer strip electrode and the pad electrode are buried in the uppermost layer of the insulating substrate. Upper surface. The wiring substrate for a fingerprint sensor according to any one of the first aspect, wherein the surface layer strip electrode, the inner layer strip electrode, and the pad electrode are formed. The surface is covered by a solder mask. The wiring substrate for a fingerprint sensor according to any one of the first aspect, wherein the insulating layer, the surface layer strip electrode, and the pad electrode are a solder resist layer having a flat surface. cover. The wiring board for a fingerprint sensor according to any one of the fifth aspect, wherein the upper surface of the surface layer strip electrode and the pad electrode is higher than the uppermost layer of the insulating substrate. The upper surface of the insulating layer is buried in the upper surface of the uppermost insulating layer so as to be lower by 0.1 to 3 μm. The wiring board for a fingerprint sensor according to the invention of claim 8, wherein the thickness of the solder resist layer covering the upper surface of the surface layer strip electrode and the pad electrode is 6 μm or less. The wiring board for a fingerprint sensor according to the above aspect of the invention, wherein the surface of the solder resist layer has an unevenness of 2 μm or less.