The present invention relates to a flexible substrate and an optical device.
A flexible substrate is used for connection between electronic circuits (Refer to Japanese Patent Laid-Open Publication No. 2011-238883). In the flexible substrate, a transmission line such as a coplanar line for transferring a high frequency signal is provided. The coplanar line is formed by a signal line and ground patterns located at either side of the signal line.
A characteristic impedance of a coplanar line is determined by a distance between a signal line and a ground pattern, the widths of the signal line and the ground pattern or the like. Sometimes, the characteristic impedance may deviate from a desired value according to the distance and the widths. An aspect of the present invention is to provide a flexible substrate including a coplanar line having a desired characteristic impedance.
An aspect of the present invention relates to a flexible substrate including: an insulating substrate having a first surface and a second surface opposite to the first surface, the insulating substrate including resin; a first connection portion configured to be connected with an external conductor and having a first conductor, a first ground pattern, and a second ground pattern on the first surface, the first ground pattern and the second ground pattern being spaced apart from the first conductor and respectively located at opposite sides of the first conductor; a conductor pattern formed on the second surface, the conductor pattern being connected to the first conductor through a first via wire which passes through the insulating substrate; and a third ground pattern formed on the second surface, the third ground pattern being connected to the first ground pattern through a second via wire which passes through the insulating substrate, wherein a distance between the conductor pattern and the third ground pattern is smaller than a distance between the first conductor and the first ground pattern.
An aspect of the present invention relates to an optical device including: a flexible substrate including an insulating substrate having a first surface and a second surface opposite to the first surface, the insulating substrate including resin, a first connection portion configured to be connected with an external conductor and having a first conductor, a first ground pattern, and a second ground pattern on the first surface, the first ground pattern and the second ground pattern being spaced apart from the first conductor and respectively located at opposite sides of the first conductor, a conductor pattern formed on the second surface, the conductor pattern being connected to the first conductor through a first via wire which passes through the insulating substrate, and a third ground pattern formed on the second surface, the third ground pattern being connected to the first ground pattern through a second via wire which passes through the insulating substrate, wherein a distance between the conductor pattern and the third ground pattern is smaller than a distance between the first conductor and the first ground pattern; a housing including an optical element; a receptacle connected to the housing; and a lead pin configured to connect the housing and the flexible substrate.
First of all, embodiments of the invention of the subject application will be described as enumerated below.
One embodiment of the present invention is a flexible substrate including: an insulating substrate having a first surface and a second surface opposite to the first surface, the insulating substrate including resin; a first connection portion configured to be connected with an external conductor and having a first conductor, a first ground pattern, and a second ground pattern on the first surface, the first ground pattern and the second ground pattern being spaced apart from the first conductor and respectively located at opposite sides of the first conductor; a conductor pattern formed on the second surface, the conductor pattern being connected to the first conductor through a first via wire which passes through the insulating substrate; and a third ground pattern formed on the second surface, the third ground pattern being connected to the first ground pattern through a second via wire which passes through the insulating substrate, wherein a distance between the conductor pattern and the third ground pattern is smaller than a distance between the first conductor and the first ground pattern.
In the above configuration, the width of the conductor pattern may be wider than the width of the first conductor.
In the above configuration, the width of the third ground pattern may be wider than the width of the first ground pattern.
In the above configuration, the first conductor may be connected to a first electrode of the external conductor, and the first ground pattern may be connected to a second electrode of the external conductor.
In the above configuration, the flexible substrate may further comprise a microstrip line including a line conductor on the first surface of the insulating substrate and a fourth ground pattern on the second surface of the insulating substrate, wherein the line conductor is connected to the first conductor.
In the above configuration, the flexible substrate may further comprise a second connection portion having a second conductor, the second ground pattern, and a fifth ground pattern on the first substrate, wherein the second ground pattern and the fifth ground pattern is spaced apart from the second conductor and respectively located at either side of the second conductor, and wherein the second ground pattern is located between the first conductor and the second conductor.
In the above configuration, the first conductor may have an end portion whose width is wider than a width of a middle portion of the first conductor.
In the above configuration, the second conductor may have an end portion whose width is wider than a width of a middle portion of the second conductor.
In the above configuration, a first coplanar line may be constituted by the first conductor, the first ground pattern, and the second ground pattern.
In the above configuration, the third ground pattern may be connected to the second ground pattern through a third via wire which passes through the insulating substrate.
In the above configuration, a second coplanar line may be constituted by the second conductor, the second ground pattern, and the fifth ground pattern.
Another one embodiment of the present invention is an optical device including: a flexible substrate including an insulating substrate having a first surface and a second surface opposite to the first surface, the insulating substrate including resin, a first connection portion configured to be connected with an external conductor and having a first conductor, a first ground pattern, and a second ground pattern on the first surface, the first ground pattern and the second ground pattern being spaced apart from the first conductor and respectively located at opposite sides of the first conductor, a conductor pattern formed on the second surface, the conductor pattern being connected to the first conductor through a first via wire which passes through the insulating substrate, and a third ground pattern formed on the second surface, the third ground pattern being connected to the first ground pattern through a second via wire which passes through the insulating substrate, wherein a distance between the conductor pattern and the third ground pattern is smaller than a distance between the first conductor and the first ground pattern; a housing including an optical element; a receptacle connected to the housing; and a lead pin configured to connect the housing and the flexible substrate.
Specific examples of the flexible substrate according to embodiments of the present invention and of the optical device according to an embodiment of the present invention will be described below with reference to the accompanying drawings. It should be noted that the present invention is not limited to these examples but shown in the claims, and it is intended that all modifications that come within the meaning and range of equivalence to the claims should be embraced herein. In the description, the same elements or elements having the same function are denoted with the same reference signs, and an overlapping description will be omitted.
The first embodiment is an example where a width of a connection pattern 40 connected to a signal line 22 is wider than a width of the signal line 22, and a distance between the connection pattern 40 and a ground pattern 42 is smaller than a distance between the signal line 22 and a ground pattern 24.
As shown in
As shown in
As shown in
The width W1 of the signal line 22 and the width W2 of the ground pattern 24 may be made to be narrow. The flexible substrate 100 can be made to be small by making the widths W1 and W2 narrow. Further, as will be described below, bond strength between the flexible substrate 100 and the wiring substrate 50 can be improved.
As shown in
A characteristic impedance of the coplanar line 20 is changed according to dimensions of the signal line 22 and the ground patterns 24. In the comparative example described later, when the widths of the signal line 22 and the ground pattern 24 are narrowed, the characteristic impedance is increased. In contrast, according to the first embodiment, the characteristic impedance can be decreased as will be described below. As shown in
As shown in
The two coplanar lines 20 provided on the upper side and the lower side of the flexible substrate 100 function as a differential transmission line. In the two coplanar lines 20 which are adjacent to each other, the ground pattern 24 between the signal lines 22 correspond to a common component. The flexible substrate 100 may be miniaturized by commonly using the ground pattern 24. The two signal lines 22 are provided to be symmetric with respect to a central line of the commoditized ground pattern 24. Accordingly, a phase characteristic between the differential signals can be improved.
The comparative example will be described.
As shown in
A transmission characteristic and a reflection characteristic in the first embodiment and the comparative example were simulated. In the simulation, a frequency of a signal was changed, and an insertion loss of the signal and a return loss of an input signal were calculated.
As shown in
A second embodiment corresponds to an example where a width of the ground pattern 42 is wider than that of the first embodiment and where a width of the conductor pattern 40 is smaller than that of the first embodiment.
As shown in
As described in the first and second embodiments, the smaller the distance L2 is, the lower the characteristic impedance of the coplanar line 20 can be. In order to narrow the distance L2, the width of the conductor pattern 40 may be extended, or the width of the ground pattern 42 may be extended. Further, the widths of both the conductor pattern 40 and the ground pattern 42 may be extended.
A third embodiment corresponds to an example where the first embodiment or the second embodiment is applied to an optical module.
Further, in the housing 76, a light emission element such as a laser diode or the like and a driving circuit for driving the light emission element are installed. An electric signal is transferred from the circuit substrate 80 through the flexible substrate 100, the lead pin 77, and the line of the insulator 78 to the driving circuit. The driving circuit amplifies the electric signal. The laser diode converts the amplified electric signal into an optical signal, and outputs a laser beam to the optical fiber 81.
According to the third embodiment, the optical module 300 includes the flexible substrate 100 and an optical element. The optical element has the lead pin 77 for receiving an input signal or transmitting an output signal. The signal line 22 of the flexible substrate 100 is connected to the lead pin 77 and the circuit substrate 80. As described above in the first embodiment, the bond strength between the flexible substrate 100 and the lead pin 77, and between the flexible substrate 100 and the circuit substrate 80 is improved. The characteristic impedance of the coplanar line 20 may be configured to have a desired value. The flexible substrate 200 may be applied to the optical module 300.
Number | Date | Country | Kind |
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2013-153980 | Jul 2013 | JP | national |
Number | Name | Date | Kind |
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5631446 | Quan | May 1997 | A |
7696628 | Ikeuchi | Apr 2010 | B2 |
8044746 | Blair | Oct 2011 | B2 |
20050116792 | Moon | Jun 2005 | A1 |
Number | Date | Country |
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2011-238883 | Nov 2011 | JP |
Number | Date | Country | |
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20150028971 A1 | Jan 2015 | US |