Single-Action Connectors Simplify Portable Device Designs

By Contributed Article | May 03, 2022

Space constraints within small devices create challenges for component placement on the boards. Innovations in ZIF-style flex connectors offer designers a possible solution.


By Jeff Combs, Director of Sales, CE Segment at Hirose Electric USA 

Hardware designs for IoT, consumer, modular, and other complex applications often leave limited space for the mating and assembly of the connector system. These space constraints can also restrict the type of connector that can be implemented. Stacked board designs or encased modular systems may not allow sufficient Z-height for vertical mating of board-to-flex connectors, or enough access for the manual closing of the actuator on zero-insertion-force (ZIF) flex connectors. At the same time, retention force is essential when the end devices are used in higher vibration environments, such as portable devices. Connectors that maintain retention force on the flex, but reduce the space needed for a manual mating process, can allow more flexibility in the application design. Additional concerns include actuator damage (a common failure mode associated with ZIF connector use), the need to reduce mating cycle time, and accommodations that may be needed for robotic assembly technologies. 

Portable Device Design Challenges

Device designs are becoming more complex in terms of board stacking and shell integration, particularly in the areas of wearables, portables, and IoT modules. Mobile devices need to maintain a small form factor while continuing to add more hardware features. IoT devices have new form factors in the X, Y, and Z dimensions. These space constraints within the devices create challenges for component placement on the boards and introduce vertical clearance and assembly concerns for stacked component or board architectures.  


Examples of portable device designs.

From the connector perspective, providing solutions that balance the space requirements while also addressing the practical concerns of assembly is a challenge. Connector solutions need to consider not only electrical and mechanical factors but operation and mating ability as well. For example, placing multiple components on a board requires layering flexes and connectors, which can limit assembly order or require mating in tight constraints. Similarly, the vertical stacking of components creates additional mating and assembly complications.  

Finally, the mating connection must be sufficiently rugged and robust to withstand the rigors of assembly and usage without accidental unmating. An acceptable level of quality is essential to meeting end users’ expectations in terms of production processes.  

Connector Technologies for Portable Devices

The small form factor of wearables and portable devices impacts the types of connectors that can be used. Traditionally, there are four types of connectors that can be used to connect boards via FPC or FFC. While the first two connectors listed below are not typically used in portable devices, they led to the development of the connectors that are used. Each connector type has advantages and disadvantages: 

Low-Insertion-Force (LIF) Connectors employ an older technology that features a one-piece design with no moving parts. The flex is simply inserted into the connector, offering very easy assembly with horizontal mating. However, there is no mechanism to hold the flex in place, other than the friction of the contacts on the flex, so LIFs provide little to no retention force. They are also quite limited in size and pitch offerings.  

Slide-Lock Zero-Insertion-Force (ZIF) Connectors also use an older technology that requires no insertion force to push the flex into an open actuator. However, they must then be manually activated and closed to provide the retention force. Slide-lock ZIFs have a complicated assembly process and are susceptible to user error and damage when the actuator is touched during assembly. They also provide horizontal mating and are limited in size and pitch. 

Flip-Lock ZIF connectors evolved from previous designs and are widely used in mobile devices. The flex is inserted into the connector with one hand, and the other hand is used to flip the actuator to close and lock it. They come in both front flip-lock and backflip-lock styles and enable easier assembly than slide-lock ZIFs do, but users still have to touch the actuator, which has the potential to cause damage. Flip-lock ZIFs also provide horizontal mating but with better retention forces and more options in terms of size and pitch than LIF and slide-lock ZIF connector. One of their biggest advantages is that they are optimized for mobile electronics. Their biggest drawback is that they require two-handed operation.  

Mezzanine Board-to-Board (BTB) Connectors are two-piece connector systems with an easy, one-handed mating mechanism that allows users to guide the plug into the receptacle and simply press down. BTB connectors offer easy assembly, better retention forces, and numerous options in terms of size and pitch. They only support vertical mating, but they are a very popular choice in mobile devices when vertical access is available.  

Connector Technology Evolves to Satisfy Portable Device Demands

Flip-lock ZIF and BTB connectors have become the default connectors for most portable devices and other small-form-factor designs. However, Hirose Electric Co., Ltd. has developed new technologies for ZIF-style flex connectors that support flex insertion without the need to engage an actuator and while still maintaining retention force on the flex. Hirose’s One Action connectors simplify the mating process by keeping the primary benefits of the older LIF and existing BTB connectors — the easy, one-handed mating action — as well as the top benefits of the actuator-style ZIF connectors, including improved retention force and the ability to unmate the connector using the actuator.  

Hirose’s One Action FH

Hirose’s One Action FH design offers low insertion force and high retention force.

One Action FH connectors are a flip-lock-style connector that can be mated without ever touching the actuator, even in designs where the actuator is natively closed. When the flex is inserted into the connector, the retention force is provided by side hooks built into the actuator that interface with side-tab cutouts on the flex. To unmate the system, the actuator can be popped open from the backside to release the side locks, or the flex can be pulled out with zero retention force.  

Hirose’s space-saving FH62 Series One Action lock connector

With a 0.25mm pitch, 1.1mm height, and a width of 4.0mm, Hirose’s space-saving FH62 Series One Action lock connector for FFC and FPC enables size reductions in medical, point-of-sale, and consumer electronics and other small electronic devices.

Finally, the contactless mating process of the One Action connector lends itself to the possibility of robotic assembly, as robots can grab a flex and insert it into a One Action connector without the need for human hands.  

New connector technologies that leverage the best elements of existing solutions while improving others to satisfy evolving market demands provide optimal solutions for many of the challenges facing portable device design engineers. One Action FH Series connectors borrow from LIF, actuator-style ZIF, and BTB connector designs to provide easy, no-actuator-contact, one-handed or even robotic mating with virtually no risk of mating damage and excellent retention forces and come in a wide range of sizes and pitches optimized for space-constrained portable device designs.  

To learn more about solutions for devices, visit Hirose Electric.

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