This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2009-195282 filed on Aug. 26, 2009, the entire contents of which are incorporated herein by reference.
An embodiment discussed herein relates to a flexible substrate provided in an electronic apparatus.
In the field of flex-rigid circuit boards, there exists technology capable of preventing substrate deformations, circuit disconnections, and the formation of waves, which can easily occur at the sites of flexion. Meanwhile, in the field of multilayer circuit boards, there exists technology for matching impedance among wiring patterns.
Since flexible substrates bend, it is necessary to secure certain mechanical characteristics, such as those related to strength and operability. However, it is difficult to adjust the thickness of wiring patterns or add additional layers to a flexible substrate in order to achieve higher-frequency transmission through the substrate, because doing so changes the mechanical characteristics of the flexible substrate.
According to an aspect of an embodiment, an electronic apparatus includes: a flexible substrate including, a first portion having a first wiring pattern, and a second portion connected to the first portion and having a second wiring pattern whose pattern width is wider than a pattern width of the first wiring pattern, wherein the second portion is supported by the first portion; a support unit configured to support the first portion of the flexible substrate; a first circuit unit connected to one of the first and second portions; and a second circuit unit connected to the first circuit unit via the first portion and second wiring patterns.
It is to be understood that both the foregoing summary description and the following detailed description are explanatory as to some embodiments of the present invention, and not restrictive of the present invention as claimed.
In the figures, dimensions and/or proportions may be exaggerated for clarity of illustration. It will also be understood that when an element is referred to as being “connected to” another element, it may be directly connected or indirectly connected, i.e., intervening elements may also be present. Further, it will be understood that when an element is referred to as being “between” two elements, it may be the only element layer between the two elements, or one or more intervening elements may also be present.
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
By way of example, a present embodiment will be described for the case of being applied to a hard disk drive (HDD) apparatus, hereinafter “HDD” for short. However, it should be appreciated that the technology disclosed in the present embodiment is also applicable to apparatuses or devices other than HDDs, such mobile phones or other electronic apparatuses having flexible substrates mounted therein.
The HDD 1 additionally includes a flexible substrate mounted therein. The flexible substrate includes regions whereupon a controller circuit 21 and an amp circuit 22 are mounted, as well as point-to-point wiring 23a. The controller circuit 21 sends write signals to the amp circuit 22, and receives read signals from the amp circuit 22. The amp circuit 22 includes a preamp (e.g., an amp IC) that amplifies write signals and read signals. The region whereupon the controller circuit 21 is mounted is affixed to the hard drive assembly 11, while the region whereupon the amp circuit 22 is mounted is affixed to the actuator block 18. Since the point-to-point wiring 23a bends in accordance with the rotation of the actuator block 18, the point-to-point wiring 23a is not fixed in place, and is highly flexed in a curved shape.
The circuitry related to write signals will now be described. The controller circuit 21 includes a write signal driver. The amp circuit 22 includes a read signal receiver. The receiver may be a preamp, for example. A write signal output from the driver in the controller circuit 21 is transmitted to the amp circuit 22 via the point-to-point wiring 23a. The write signal transmitted to the amp circuit 22 is amplified by the receiver inside the amp circuit 22.
A lid (not shown) is attached to the hard drive assembly 11, thus creating a hermetically sealed space. The magnetic disk 12, the spindle motor 13, the head slider 14, the head suspension 15, the arm 16, the bearings 17, the actuator block 18, the VCM 19, the amp circuit 22, and the point-to-point wiring 23a exist inside this hermetically sealed space. The controller circuit 21 exists outside this hermetically sealed space. A metal plate 24a is affixed to the hard drive assembly 11. By sealing off the boundary portion between the inside and the outside of the hermetically sealed space, the metal plate 24a keeps the hermetically sealed space airtight. The metal plate 24a may be realized by a metal such as stainless steel, for example.
Hereinafter, a flexible substrate will be described using
In order to match the characteristic impedance, the thicknesses of the surface-protecting layer 27, the base layer 29, and the individual adhesive layers may be altered, or alternatively, the thicknesses of the wiring patterns 26a and 26b may be altered. However, if such thicknesses are altered, then the flexibility, strength, and other mechanical characteristics of the flexible substrate 2 will change. Therefore, it is preferable to adjust the pattern widths such that the mechanical characteristics of the flexible substrate 2 remain unchanged, and thereby match the characteristic impedance without altering the thicknesses of the surface-protecting layer 27, the base layer 29, the individual adhesive layers, or the wiring patterns 26a and 26b.
Ideally, the pattern widths of the wiring patterns 26a and 26b for the metal attachment portions 25a and 25b as well as the point-to-point wiring 23a should be adjusted such that the characteristic impedance becomes equal to the impedance of the receiver and the driver. Herein, it should be appreciated that wiring patterns other than the wiring patterns 26a and 26b may also be collected in the metal attachment portions 25a and 25b as well as in the point-to-point wiring 23a. Since modifying the pitch of the wiring patterns 26a and 26b will affect the wiring pitch of other collected wiring patterns, it is possible that the design of the wiring patterns themselves may need to be re-evaluated. Consequently, it is preferable to adjust the pattern widths of the wiring patterns 26a and 26b without modifying the pattern pitch. In addition, there exist pattern width constraints for preserving the mechanical characteristics of the flexible substrate 2 against fabrication problems and vibrations. If the pattern widths are not at least substantially equal to the lower-bound values of these constraints, then disconnections might occur in the wiring patterns 26a and 26b. Thus, the pattern widths of the wiring patterns 26a and 26b should satisfy the constraints.
First, as a result of instructions issued by the user via the input unit 54, the CPU 51 designs a flexible substrate (S101) as shown in
After computation, the CPU 51 uses the computation results as a basis for setting the respective pattern widths for the wiring patterns 26a and 26b in the metal attachment portions 25a and 25b as well as the point-to-point wiring 23a (S105). More specifically, the CPU 51 sets the characteristic impedance respectively for the wiring patterns 26a and 26b in the metal attachment portions 25a and 25b as well as the point-to-point wiring 23a, such that the characteristic impedance is as close as possible to the impedance of the receiver. The CPU 51 then sets pattern widths corresponding to this characteristic impedance in the metal attachment portions 25a and 25b, respectively, as well as the point-to-point wiring 23a. In other words, the characteristic impedance is matched among the metal attachment portions 25a and 25b as well as the point-to-point wiring 23a.
After setting the pattern widths, the CPU 51 conducts circuit analysis of the flexible substrate as a whole, including circuits near the point-to-point wiring 23a (e.g., all wiring patterns in the flexible substrate), and checks whether any problems exist in the behavior (for example, the transmission characteristics or other aspects of signal quality) of the flexible substrate (S106). If there are no problems in the behavior of the flexible substrate (S106, No), then the present flow is terminated.
In contrast, if a problem does exist in the behavior of the flexible substrate 2 (S106, Yes), then the CPU 51 once again executes the processing for adjusting the wiring pattern widths in operation S105. In this case, the set pattern widths may be re-adjusted, and the set characteristic impedance may be re-adjusted. This circuit analysis may be conducted using a circuit simulation, for example.
Next, the transmission characteristics of the flexible substrate 2 will be compared to the transmission characteristics of a flexible substrate 2a (not illustrated), herein given as a comparative example. In the flexible substrate 2a, the pattern widths of the wiring patterns 26a and 26b in the point-to-point wiring 23a are equal to those in the metal attachment portions 25a and 25b. First, the pattern widths of the wiring patterns 26a and 26b in the metal attachment portions 25a and 25b as well as the point-to-point wiring 23a will be described.
The fundamental frequency of the flexible substrate 2a is f1. The fundamental frequency of the flexible substrate 2 is f2. The frequency f2 is higher than the frequency f1. Accordingly, the pattern width of the point-to-point wiring 23a is set such that its characteristic impedance matches the characteristic impedance of the wiring patterns 26a and 26b in the metal attachment portions 25a and 25b. In so doing, the frequency that attenuates at −3 dB can be increased. Consequently, improved transmission characteristics can be anticipated.
Meanwhile, as illustrated in
Gradually increasing the pattern width of the wiring patterns 26a and 26b exhibits the effect of inhibiting the concentration of stress at the boundary portions 61 and 62. Herein, the shapes of the wiring patterns 26a and 26b at the boundary portions 61 and 62 are shaped so that any effects on the characteristic impedance and the transmission characteristics can be ignored, and may be appropriately set according to factors such as the width and thickness of the wiring patterns 26a and 26b.
This technique is executed as part of the wiring pattern adjustment process in operation S105. For example, after setting the pattern widths in the metal attachment portion 25a and the point-to-point wiring 23a, the CPU 51 may gradually increase the pattern width of the wiring pattern 26a, starting at a point along the metal attachment portion 25a. The CPU 51 makes the pattern width of the wiring pattern 26a equal to the pattern width of the point-to-point wiring 23a at the boundary where the metal attachment portion 25a becomes the point-to-point wiring 23a.
An HDD has been given as an example of an electronic apparatus, but the present embodiment is not limited thereto. For example, the present embodiment may also be an electronic apparatus such as a mobile phone handset.
In the process for creating 2D cross-sectional models in operation S102, a 2D cross-sectional model of the metal attachment portion 25a is created. However, a 2D cross-sectional model of the metal attachment portion 25b may be created, or 2D cross-sectional models for both the metal attachment portions 25a and 25b may be created. In the process for computing an impedance change in operation S104, the characteristic impedance is computed with respect to the wiring patterns 26a and 26b. However, in cases where the wiring patterns 26a and 26b have identical structures, the characteristic impedance may be computed with respect to just one of either the wiring pattern 26a or the wiring pattern 26b, with the computation results being applied to the remaining wiring pattern. The above may be similarly applied to the wiring pattern width adjustment process in operation S105.
In the wiring pattern width adjustment process in operation S105, the computation results are described as being used as a basis for setting respective pattern widths for the wiring patterns 26a and 26b in the metal attachment portions 25a and 25b as well as the point-to-point wiring 23a. However, in the standard flexible substrate creation process in operation S101, the characteristic impedance of the pattern widths in the metal attachment portions 25a and 25b may be set to the value closest to the impedance of the receiver, and a flexible substrate may be designed with such pattern widths are the standard pattern widths. In this case, the pattern widths of the metal attachment portions 25a and 25b become fixed in the wiring pattern width adjustment process in operation S105, and only the pattern width of the point-to-point wiring 23a is set.
In the wiring pattern width adjustment process in operation S105, the respective characteristic impedance of the wiring patterns 26a and 26b in the metal attachment portions 25a and 25b as well as the point-to-point wiring 23a is described as being set to the characteristic impedance that is closest to the impedance of the receiver. However, the respective characteristic impedance of the wiring patterns 26a and 26b in the metal attachment portions 25a and 25b as well as the point-to-point wiring 23a may also be set to the characteristic impedance that is closest to the impedance of the driver. However, in this case, the impedance of the driver and the receiver may be matched.
In the standard flexible substrate creation process in operation S101, the characteristic impedance of the pattern width in the point-to-point wiring 23a may be set to the value closest to the impedance of the receiver, and a flexible substrate may be designed with this pattern width as the standard pattern width. In this case, the pattern width of the point-to-point wiring 23a becomes fixed in the wiring pattern width adjustment process in operation S105, and only the pattern widths of the metal attachment portions 25a and 25b are set. For example, the pattern width of the point-to-point wiring 23a may be fixed at the initially designed pattern width in the standard flexible substrate creation process in operation S101, and then reduced by a factor of approximately 0.5 to 0.8 to set the pattern widths of the wiring patterns 26a and 26b in the metal attachment portions 25a and 25b.
However, in the case of fixing the pattern widths of either the metal attachment portions 25a and 25b or the point-to-point wiring 23a, the design is subject to the conditions that the characteristic impedance be matched for the metal attachment portions 25a and 25b as well as the point-to-point wiring 23a, and that no problems occur in the fabrication of the flexible substrate 2. Similar conditions apply to the case of modifying both the pattern widths of the metal attachment portions 25a and 25b as well as the pattern width of the point-to-point wiring 23a.
Herein, the pattern widths to be modified are described as being the pattern widths of the wiring patterns 26a and 26b that transmit write signals. However, the widths of the wiring patterns that transmit read signals may also be modified. In addition, in cases where additional wiring patterns are formed in the point-to-point wiring 23a for purposes other than transmitting write signals or read signals, such wiring patterns may also be modified.
The pattern widths of the wiring patterns 26a and 26b are described as being modified for the metal attachment portions 25a and 25b as well as the point-to-point wiring 23a. However, the pattern widths of the wiring patterns 26a and 26b may be modified for the other metal attachment portions 25c and 25d as well as the point-to-point wiring 23b and 23c. In this case, the pattern widths may be modified for the wiring patterns 26a and 26b in a portion of the point-to-point wiring, without modifying the pattern widths of the wiring patterns 26a and 26b in the entire plurality of point-to-point wiring. Similarly, the pattern widths may be modified for the wiring patterns 26a and 26b in a portion of the metal attachment portions, without modifying the pattern widths of the wiring patterns 26a and 26b in the entire plurality of metal attachment portions.
Metal plates such as the metal plate 24a are described as being attached to one side of the flexible substrate 2. However, metal plates may be attached to both sides, and the wiring patterns 26a and 26b may be formed on both sides of the flexible substrate 2. Furthermore, although the metal plates are herein attached to the metal attachment portions 25a to 25d, the metal plates may also be provided in a joined state with the metal of the hard drive assembly 11 or the actuator block 18, for example, instead of being attached.
Due to increases in the transfer speeds of electronic apparatuses, such as the HDD 1, degradation of the transmission characteristics in the flexible substrates housed in such electronic apparatus becomes a problem. In the case of improving the transfer rate, it becomes necessary to raise the frequency of the transmission characteristics of the flexible substrate. There exists technology for adjusting the thickness of wiring patterns or adding additional layers to a flexible substrate in order to achieve impedance matching or techniques for higher-frequency transmission. If pattern thicknesses are adjusted or additional layers are added, then the mechanical characteristics of the flexible substrate will change. With flexible substrates that include areas such as the point-to-point wiring 23a, changing the mechanical characteristics is not desirable.
According to the present embodiment, the patterns widths of the wiring patterns 26a and 26b in the metal attachment portions 25a and 25b as well as the point-to-point wiring 23a are set to widths such that the characteristic impedance is matched. Accordingly, it becomes possible to improve transmission characteristics at higher frequencies, while leaving the mechanical characteristics almost entirely unchanged. By increasing the frequency of the transmission characteristics, signal quality is improved.
When additional layers are added to the flexible substrate 2 or the thicknesses of the wiring patterns 26a and 26b are adjusted in order to match the characteristic impedance, the number of fabrication steps and the change in the mechanical characteristics increases considerably. In contrast, with the adjustment of the widths of the wiring patterns 26a and 26b in the present embodiment, the increase in the number of fabrication steps and the change in the mechanical characteristics are decreased.
All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Although the embodiments of the present inventions has been described in detail, it should be understood that various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.
Number | Date | Country | Kind |
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2009-195282 | Aug 2009 | JP | national |