# US 2021/0243882 A1 · Flexible substrate

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- Number: US 2021/0243882 A1
- Document ID: US20210243882A1
- Status: Published application
- Kind: A1
- Application number: 17/053,161
- Filed: 2018-08-23
- Published: 2021-08-05
- Earliest claimed: 2018-08-23
- Assignees: Mitsubishi Electric Corporation
- Applicants: Mitsubishi Electric Corporation
- Inventors: Shinjiro NISHIZU
- Web page: https://patentgrep.com/patent/US20210243882A1

## CPC

- H05K 1/028: {Bending or folding regions of flexible printed circuits (H05K1/0283 takes precedence)}
- H05K 1/0281: {Reinforcement details thereof}
- H05K 2201/09063: Holes or slots in insulating substrate not used for electrical connections
- H05K: PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS

## Abstract

A flexible substrate includes a base substrate layer; and two patter layers laminated together on the front- and back-sides of the flexible substrate, on which electric circuit lines are printed each. In order to reduce a stress generated in the flexible substrate when it is folded and soldered to an optical communication semiconductor package, the flexible substrate has a thickness-wise concavely deformed portion in a lengthwise middle portion thereof. Also to reduce the stress, the flexible substrate having the deformed portion further has end sections and a middle section formed in its longitudinal direction, and the widths of the end sections are larger than that of the middle section, and the flexible substrate having the deformed portion further has holes and holes respectively formed near the side edges of a lengthwise middle section thereof.

## Claims

### Claim 1

A flexible substrate comprising:
a base substrate layer formed of an insulation material;
a front-side pattern layer on a front-side of the base substrate layer, on which pattern layer electric circuit lines are printed; and
a back-side pattern layer on a back-side of the base substrate layer, on which pattern layer electric circuit lines are printed,
wherein the base substrate layer, the front-side pattern layer, and the back-side pattern layer are laminated together, and the flexible substrate has a deformed portion deformed concavely in a thickness direction of the flexible substrate.

### Claim 2 (depends on 1)

The flexible substrate of claim 1, wherein the deformed portion has a cylindrical shape, and letting a width and a depth of the deformed portion be B and H, respectively, H/B is set smaller than 0.46.

### Claim 3 (depends on 1)

The flexible substrate of claim 1, wherein the deformed portion has a cylindrical shape, and letting a curvature radius of the deformed portion be R and a thickness of the flexible substrate be d, d/R is set to smaller than 0.26.

### Claim 4 (depends on 1)

The flexible substrate of claim 1, wherein widths of both end sections of the flexible substrate are larger than a width of a lengthwise middle section of the flexible substrate.

### Claim 5 (depends on 1)

The flexible substrate of claim 1, wherein at least one hole is formed near each of side edges of the flexible substrate.

### Claim 6 (depends on 2)

The flexible substrate of claim 2, wherein widths of both end sections of the flexible substrate are larger than a width of a lengthwise middle section of the flexible substrate.

### Claim 7 (depends on 2)

The flexible substrate of claim 2, wherein at least one hole is formed near each of side edges of the flexible substrate.

### Claim 8 (depends on 3)

The flexible substrate of claim 3, wherein widths of both end sections of the flexible substrate are larger than a width of a lengthwise middle section of the flexible substrate.

### Claim 9 (depends on 3)

The flexible substrate of claim 3, wherein at least one hole is formed near each of side edges of the flexible substrate.

### Claim 10 (depends on 4)

The flexible substrate of claim 4, wherein at least one hole is formed near each of side edges of the flexible substrate.