“Smart” technology is rapidly becoming an integral part of daily life. Sparked by the introduction of smartphones, the intelligent device trend has experienced tremendous growth in the automotive, household appliance, and wearable markets. Expanding into homes and other buildings, the smart home concept connects thermostats, security devices, lighting, and other connected appliances capable of communicating with each other. Such devices can be controlled with multifunction remotes, wall-mounted touchscreens, smartphones, and other web-enabled devices. For optimum comfort and efficiency, smart homes give homeowners the ability to automate and monitor and control the building’s connected devices.
Consumers want devices that are easy to use and innately blend into their home’s design by incorporating user-friendly, aesthetically pleasing, and exceptionally subtle smart home electronics. To meet these demands, design engineers for smart home electronics are challenged to make these devices as small as possible, while retaining all of their current capabilities, and often while incorporating even more functionality. The quickest way to reduce the size of an electronic device is to reduce the size of its PCB, which requires a combination of creative space management and reduced-size components.
Historically, electronics have trended toward smaller, sleeker, and lighter designs, driving connector manufacturers to achieve improved performance and reliability in smaller profiles and footprints. Largely due to the need to accommodate modular expansion cards, card edge connectors are usually some of the biggest components on a PCB. The size of these connectors can effectively limit the degree by which engineers are capable of shrinking the PCB’s footprint. However, connector manufacturers are finding creative new ways to solve this design problem, including the recent release of new connector designs, such as an M.2 card edge connector designed to accept dual-sided module cards loaded with additional components for expanded capabilities, and another that is terminated into, rather than onto, a PCB—reducing its profile height to a mere 1.8mm.
To be relevant in the smart home market, a device’s user interface needs to be wireless-compatible. Components that support this feature, like wireless module cards and the connectors that accept them, are generally large in size compared to other board-level components. However, a recent specification change has enabled significantly smaller form factors, making use of these components more viable. Formerly known as Next-Generation Form Factor (NGFF), the M.2 specification for internally mounted computer expansion cards and connectors supersedes the Miniature Serial AT Attachment (mSATA) specification, which uses the PCI Express Mini Card (PCIe Mini) physical layout and connectors.
Designed for use with a wider range of module widths and lengths than its predecessor, the M.2 specification features a more flexible physical specification and advanced interfacing capabilities, and also enables smaller computer expansion cards that operate at faster transfer speeds. Due to the standard M.2 criteria for pin count and keying layouts—depending on which capability the expansion card provides—these sleek, WiFi, WWAN, and SSD expansion cards can be inserted into virtually any card edge connector, regardless of the manufacturer. Connector manufacturers distinguish themselves by offering different mounting options for this seemingly universal M.2 connector design.
The different mounting options primarily affect the connector’s above-board height and the location of the module’s seating plane, which is where the card edge of a module enters a connector. Standard M.2 card edge connectors measure a slight 2.3mm high, and are designed to leave just enough space for the bottom of the module card to clear the mounting surface of the host PCB, but offer no performance benefits beyond contributing to PCB size reductions and connecting an M.2 module card.
To meet the smart home market’s demand for both reduced PCB size and expanded capabilities, several manufacturers have introduced larger 3.2mm M.2 connectors. Designed to accept dual-sided module cards and module cards outfitted with additional components, the minimal height these connectors add to a design enables improved functionality that 2.3mm M.2 connectors are unable to deliver.
Largely driven by the thinning of electronic devices like tablets and notebook PCs, several connector manufacturers are developing M.2 connectors with a module seating plane slimmer than the 2.3mm version. By cutting into the host PCB, designers have developed an innovative workaround solution that maintains compatibility with the universal M.2 requirements, which isn’t possible with further adjustments to the size of the actual connector. Measuring just 1.8mm high, these latest M.2 card edge connectors are half a millimeter shorter than the standard device, which provides a significant reduction in the connector’s height. With these, engineers are afforded extra space to run a cable or populate components—including FFC/FPC cables with thicknesses of 0.3mm or less and capacitors with profile heights as low as 0.18mm—where there once wasn’t room, providing another effective solution for simultaneously shrinking PCB size while increasing functionality.
Designing for smart home electronics requires combined efforts from several links in the electronics supply chain, but innovative, reliable, and cost-effective component-level solutions like the new M.2 card edge connectors available in various mounting positions with respective benefits are one way device designers can achieve sleeker, subtler, and more attractive designs while simultaneously increasingly its functionality.
