This invention generally relates to printed circuit boards and more particularly to multi-flex printed circuit board systems for use in electronic wearable devices.
Nowadays, electronic devices are involved in almost every human endeavor. Over time, a size of the electronic devices has reduced with simultaneous increase in the capability of these electronic devices. For example, a physical size of a mobile phone has drastically reduced over the years and at the same time the mobile phone, in addition to enabling a user to make and receive phone calls or send and receive messages, can now be used to click pictures, browse web, send and receive emails, play games etc.
One recent development in these attempts to make electronic devices, smaller, better and user-friendlier, is the advent of consumer wearable devices. Wearable devices include a range of products that are capable of being worn on a user's body for an extended period of time and are configured to significantly enhance a user experience as a result of the product's functions. Typically, the wearable devices contain advanced sensor circuitry and wireless connectivity, and they rely on smartphone application ecosystem to process the information. Nowadays, smartphone applications for wearable devices include software applications related to fitness, healthcare, automobile accessibility, outdoor activities, home infrastructure and even gaming.
In the case of gaming, options for wearable motion controlled gaming devices are being explored to solve many of the problems currently plaguing the gaming industry. For example, in order to play motion-controlled games, typically, a user must purchase expensive hardware and related software, such as for example suitable displays, gaming consoles (for example, Wii or Xbox and Kinect), so on and so forth. Further, a large physical space is required to support this type of gaming. Furthermore, since the touch screen has small space for a virtual gamepad and a users' finger blocks some part of the gaming display area, the limited space and no tactile impression makes mobile gaming difficult to play. Wearable motion controlled mobile gaming devices are expected to improve the mobile gaming experience by offering a three-dimension touch less space instead of a two-dimension playfield touch screen.
As wearable motion controlled mobile gaming devices fall in the category of consumer electronic devices, a stylish and ergonomic design is required. However, developing wearable mobile gaming devices with stylish and ergonomic design and at the same time maximizing a user experience is difficult. For example, configuring wearable mobile gaming devices in round or circular shapes to configure an armband, a bracelet or a ring, while designing a printed circuit board (PCB) to fit in the various hardware components poses a significant challenge. A manufacturing cost of the PCB also has to be controlled to ensure the retail product is in a fairly affordable range.
The principal object of the embodiments herein is to provide a multi-flex PCB system for wearable devices that is ultra-thin and completely bendable.
The above-mentioned needs are met by a multi-flex printed circuit board for wearable systems.
A multi-flex printed circuit board for wearable systems includes a plurality of sections made up of flexible composites and a conductive material (such as copper) that allows complete bendability of the multi-flex board. Each section is configured with a desired combination of layers; one or more components soldered on top and/or bottom copper layer. The multi-flex board is configured to enable component assembly load on one or more thicker layer sections and routing capability to one or more thinner layer sections. The middle layers of the thicker layer section extend out to form the thinner layer section.
These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.
In the accompanying figures, similar reference numerals may refer to identical or functionally similar elements. These reference numerals are used in the detailed description to illustrate various embodiments and to explain various aspects and advantages of the present disclosure.
The above-mentioned needs are met by multi-flex printed circuit board for wearable systems. The following detailed description is intended to provide example implementations to one of ordinary skill in the art, and is not intended to limit the invention to the explicit disclosure, as one or ordinary skill in the art will understand that variations can be substituted that are within the scope of the invention as described.
The best and other modes for carrying out the present invention are presented in terms of the embodiments, herein depicted in
It is noted that this invention relates to printed circuit board (PCB) systems for use in electronic devices, which include complex electronic components and require the internal PCBs to be completely bendable with all components on. It is understood that designing a PCB with a high flexibility requirement, especially for consumer electronic devices, poses significant challenges. For example, a PCB for a circular shaped wearable motion controlled mobile gaming device requires almost 360-degree flexibility. To being able to bend, the PCB has to include flexible parts. According to the amount of times that a PCB can be bent, two classification standards namely a semi-static standard and a dynamic standard are generally defined. For adhering to a semi-static standard, a PCB should be capable of flexing up to 20 times. For adhering to a dynamic standard, a PCB should be capable of being regularly twisted and flexed. As the PCB is not supposed to be twisted or flexed any more times once the PCB is assembled into the outer shell of the consumer electronic device such as a wearable gaming device, the PCB design should conform to a semi static standard.
In addition to the flexibility requirement, product reliability level and pricing also need to be considered. It is noted that three manufacturing classes are generally defined in terms of the product reliability level and the pricing. Class I relates to general electronic products where the major focus is on functionality. Class II relates to dedicated service electronics products where a higher performance and longer lifetime is demanded. This is a common class for consumer electronics such as gaming consoles. Class III relates to high reliability electronic products. For this class, the boards and the components' lifetime have to be assured and the highest reliability is required. Normally, applications related to military use or medical treatment need class III standard for the PCBs. Class III PCBs are most expensive ones among the three classes of PCBs on account of the special materials used and manufacturing process involved in their generation. As a result, PCB design for applications of consumer electronic devices, such as wearable gaming devices, may be chosen in a manner such that the design conforms to semi-static standard and dedicated to service electronic products in class II.
Typically, for designing a PCB with a high flexibility requirement for a consumer electronic device, such as a wearable motion controlled mobile gaming device, ‘flex PCB’ is preferred over other types of flexible PCBs, such as ‘rigid-flex PCB’ and ‘semi-flex PCBs’, as flex PCB provides a satisfactory balance between price and flexibility desired for consumer electronic devices. It is noted that materials normally used for designing a rigid-flex PCB include a combination of polyimide and flame retardant 4 (FR4). Since two materials (such as FR-4 and polyimide) are normally involved in manufacturing the rigid flex PCB, the manufacturing process is harder than flex PCB (which primarily uses only polyimide as a laminate) and thereby, the manufacturing cost is higher. Moreover, compared with the rigid-flex PCB, a flex PCB can be utilized in much more complex geometries and with greater spatial freedom. The flex PCB can also be built up as a single layer or a multilayer flex also called multi-flex board depending on electronics' system complexity.
A semi-flex PCB can be considered to be ultra-thin rigid-flex PCB. The semi-flex PCB normally uses FR4 thin laminate. The ultra-thin feature of the semi-flex PCB renders certain flexibility and generally speaking, FR4 costs less than the polyimide for manufacturing flex boards. However, according to different fabrication houses' capabilities, the semi-flex PCB can only be bent few times with a very limited bending radius, which may not serve the purpose for devices such as wearable devices, which are to be designed in the shape of a band, bracelet, pendant, charms, ring, earring, brooches, etc. In comparison with other types of flexible PCBs, the flex PCB has relatively good temperature and humidity tolerance with lower cost. Hence, it is the optimal type of PCBs in consumer electronic devices with high flexibility requirement, such as wearable gaming devices.
In addition to selecting an appropriate type of PCB (for example, a flex PCB with a design conforming to a semi-static standard and dedicated to service electronic products in class II), determination of how to create a stack-up of the layers that would compose a multi-flex board that is completely bendable is also critical. Flex PCB normally gives a degree of bendability, however, being able to bend 360 degree relies on the consideration of a number of layers included in the stack. It is understood that having more layers increases a flexibility of routing, however, a thickness of the multi-flex board increases. Thus, in terms of the demands of the bendability and complexity of consumer electronic devices, such as wearable motion controlled mobile gaming systems, a maximum four-layer multi-flex PCB is the best compromise. Further, choosing a right architecture of the four-layer board is also important. A multi-flex board can be implemented to include a constant number of layers as exemplarily depicted in
The first flex copper clad laminate (FCCL) layer 306 consists of Layer 1, Layer 2, two adhesive layers 306a and 306b and a polyimide layer 306c. The second FCCL layer 308 consists of Layer 3, Layer 4, two adhesive layers 308a and 308b and a polyimide layer 308c. Since each FCCL layer includes two copper layers, it is called double-sided copper-clad laminate. It is a complex film where two adhesive layers are coated on one polyimide layer and two copper foils are coated on top of each adhesive layer.
Further, coverlays, such as a top coverlay 302 and a bottom coverlay 304 are provided on the top and bottom portion of the multi-flex board 100, respectively. The coverlays 302 and 304 are used to protect the circuits and systems on the multi-flex board 100 from environmental and electrical interference. A coverlay usually includes a polyimide layer and an adhesive layer. Accordingly, the top coverlay 302 includes a polyimide layer 302a and an adhesive layer 302b, whereas the bottom coverlay 304 includes a polyimide layer 304a and an adhesive layer 304b. It is noted that a polyimide layer such as the polyimide layers 302a or 304a includes polyimide, which is a widely-used laminate material used in flex PCBs.
It is understood that a laminate is a substrate material for PCBs and it is the base film for the conductor. Polyimide is typically chosen as the laminate material because it combines chemical stability, temperature tolerance and mechanical strength with good dielectric properties. An adhesive is the material that can glue a laminate with a conductor or a laminate with another laminate. An adhesive layer, such as the adhesive layer 302b or 304b includes acrylic or epoxy, which are the most common chemical materials used for adhesives.
Furthermore, a bond ply layer 310 is included between the Layers 2 and 3. The bond ply layer 310 includes two adhesive layers 310a and 310b and a polyimide layer 310c. A simplified top-view representation of the multi-flex board 100 is depicted in
The conventional design of the multi-flex board 100 as described with reference to figures from
Various embodiments of the present technology provide a multi-flex printed circuit board system that is capable of overcoming these and other obstacles and providing additional benefits. More specifically, various embodiments of the present technology disclosed herein present a PCB design for a multi-flex printed circuit board structure that is capable of meeting requirements such as ultra-thin thickness profile of the board (thereby allowing 360 degree of bendability) and less manufacturing cost, as desired by consumer electronics, such as wearable motion controlled mobile gaming devices. Moreover, the proposed design also conforms to reliability requirement including trusty thermal stress test, solder-mask adhesive test and solderability test. A PCB design for such a multi-flex printed circuit board system is explained with reference to
Furthermore, the components are to be soldered on top of Layer 1 and/or Layer 4 of sections with four-layer thickness depending on the complexity of the design to be implemented on the multi-flex board structure 600. All the sections with two-layer thickness are used for routing and bending. The routing includes power, ground traces and all the necessary signal paths as explained with reference to
In an embodiment, the sections 702, 704 and 706 are configured to include a power plane and a ground plane. For example, the section 702 includes a power plane 712a and a ground plane 714a; the section 704 includes a power plane 712b and a ground plane 714b; and the section 706 includes a power plane 712c and a ground plane 714c. The power plane is not necessarily larger than the ground plane or vice versa. However, for EMI consideration, the power plane or the ground plane is normally designed to enclosed by the other one.
Further, the power traces, signal path zones and ground traces are disposed on the sections with two-layer thickness. For example, the section 708 is configured to include a power trace 716a, a signal path zone 718a and a ground trace 720a. Similarly, the section 710 is configured to include a power trace 716b, a signal path zone 718b and a ground trace 720b as shown in
The relatively wide power traces, such as the power traces 716a and 716b are used to connect the power planes 712a, 712b and 712c, whereas the ground traces, such as the ground traces 720a and 720b are used to connect the ground planes 714a, 714b and 714c, in between two successive sections of four-layer thickness. It is noted that signals in the multi-flex board system can be routed in the signal path zones, such as the signal path zones 718a and 718b. A stack up view of a multi-flex board is shown in
Accordingly, the stack-up view of the multi-flex board 500 depicts four layers: Layer 1, Layer 2, Layer 3 and Layer 4 (also labeled as layers 802, 804, 806 and 808, respectively). The Layers 1, 2, 3 and 4 of the multi-flex board 500 are made of a conductive material, such as copper. The Layers 1, 2, 3 and 4 are arranged in a manner to form a section 810 of four-layer thickness (i.e. including four copper layers among other layers) and another section 812 of two-layer thickness (including two copper layers among other layers). The Layers 1, 2, 3, 4 are included within four FCCLs, such as FCCL 1, FCCL 2, FCCL 3 and FCCL 4 labeled as layers 814, 816, 818 and 820. FCCLs 1 and 3 are double-sided copper clad laminate with bottom copper foil etched off. Thus, a copper layer (i.e. Layer 1), an adhesive layer 822 and a polyimide layer 824 form the FCCL 1 (i.e. layer 814) and a copper layer (i.e. Layer 3), an adhesive layer 826 and a polyimide layer 828 form the FCCL 3 (i.e. layer 818). Furthermore, FCCLs 2 and 4 are double-sided copper clad laminate with top copper foil etched off. Therefore, FCCL 2 (i.e. layer 816) includes a polyimide layer 830, an adhesive layer 832 and a copper layer (i.e. Layer 2) and FCCL 4 (i.e. layer 820) consists of a polyimide layer 834, an adhesive layer 836 and a copper layer (i.e. Layer 4).
Further, coverlays, such as a top coverlay 838 and a bottom coverlay 840 are provided on the top and bottom portion of the multi-flex board 500, respectively. The coverlays 838 and 840 are used to protect the circuits and systems on the multi-flex board 500. A coverlay usually includes a polyimide layer and an adhesive layer. The top coverlay 838 includes a polyimide layer 842 and an adhesive layer 844, whereas the bottom coverlay 840 includes a polyimide layer 846 and an adhesive layer 848 as shown in
Further, the multi-flex board 500 includes an adhesive layer 850 disposed between the FCCLs 1 and 2 (i.e. layers 814 and 816). Two bond ply layers are included between FCCLs 2 and 3 (i.e. layers 816 and 818) and FCCLs 3 and 4 (i.e. layers 818 and 820), respectively. The first bond ply layer 852 is formed by a polyimide layer 854 and two adhesive layers 856 and 858 coated on it. The second bond ply layer 860 is also composed of one polyimide layer 862 and two adhesive layers 864 and 866 in the same form.
The FCCLs 2 and 3 (i.e. layers 816 and 818) extend out of the section 810 and form the section 812, which has a thickness of around a 7-8 mils to give a reasonable impedance control capability to the multi-flex board 500. The multi-flex board structure as depicted in
The Layers 1, 2, 3 and 4 (also shown as 916, 918, 920 and 922) of the multi-flex board 900 are made of a conductive material, such as copper. The Layers 1, 2, 3, 4 are included within four FCCLs, such as FCCL 1, FCCL 2, FCCL 3 and FCCL 4.
The section 910 includes a top coverlay 924 disposed of a top portion of the FCCL 1 and a bottom coverlay 926 disposed on a bottom portion of the FCCL 4. The top coverlay 924 includes a polyimide layer 928 and an adhesive layer 930 and the bottom coverlay 926 includes a polyimide layer 932 and an adhesive layer 934 as shown in
The middle FCCLs 2 and 3 extend out of the section 910 and form the section 912, which has a thickness of around a 7-8 mils to give a reasonable impedance control capability to the multi-flex board 900. In an embodiment, the section 914 has a thickness of around 12 to 13 mils (i.e. around 0.3 mm). The section 914 is shown to include an extended portion of the section 912 and portions of the FCCL 1 (i.e. layer 902), the adhesive layer 936, adhesive layer 950 and polyimide layer 948 as shown in
In an embodiment, the multi-flex board 900 accommodates complex designs with additional routing space when compared with the multi-flex board 500 of
As depicted in
In an example embodiment, the system 1000 may be implemented on one or more multi-flex boards such as the multi-flex board 500 or the multi-flex board 900 explained above, so as to configure a multi-flex printed circuit board system. The multi-flex PCB system may be assembled for use within a consumer electronic device, such as a wearable motion controlled gaming device. One such implementation is explained with reference to
As depicted in
It is noted that since the proposed solution is an ultra-thin design, extreme heat during assembly can curve the multi-flex boards. One of the traditional ways is to use stiffeners to add hardness to the multi-flex boards. As demonstrated in
Moreover, for reasonable cost and high reliability performance either under high temperature soldering processes or variant daily circumstances, DuPont Pyralux FR may be used for flexible composites such as adhesive layers and coverlay layers as described in
Various example embodiments offer, among other benefits, techniques for a multi-flex PCB design for use in consumer electronic devices, such as wearable motion controlled mobile gaming devices. The proposed multi-flex PCB design is ultra-thin and 360 degree bendable. The board architecture and the selection of the materials make the PCB to achieve the requirement for different sizes and shapes (such as ring, band, bracelet, etc.) of the wearable devices for motion controlled mobile gaming. For some shapes, which only require a flat surface, the standard rigid PCB may also be chosen. Further, a manufacturing cost for the board is also controlled in a safe range, which keeps the wearable device at an affordable retail price. Also, the multi-flex board maintains good noise performance and routing capability. Furthermore, the multi-flex board structure could be easily transformed from a 4-2 layers' combination to a 4-3-2 layers' combination and take on flexibility of single side soldering and double side soldering. Hence, it is considered as a highly adaptive design to either relatively simple system or complex system for mobile gaming devices. Moreover, the 4-2 layers' combination or the 4-3-2 layers' combination of the multi-flex board design may be implemented for any wearable devices that are having quasi-band shape such as a bracelet, a ring, a circular earring and circular brooches etc.
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously, many modifications and variations are possible in light of the above teaching. The exemplary embodiment was chosen and described in order to best explain the principles of the present invention and its practical application, to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated.
Accordingly, the disclosure of the present invention is intended to be illustrative, but not limiting, of the scope of the invention, which is set forth in the following claims.
Number | Date | Country | |
---|---|---|---|
62335079 | May 2016 | US |