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Microminiature Connector Solutions for Wireless Handheld Devices

Fri, 08/21/2009 - 8:54am

Size Matters with Consumer Electronics Components.

Molex-author-0909Microminiature connector solutions offer compact size, low cost, high performance and flexibility – making them a perfect fit for wireless handheld devices.  Below is a review of three key microminiature solutions for typical 40-circuit signal applications including relative performance, features and benefits, size attributes and rank by total cost of system solution.

FPC-to-Board Solutions
Fine pitch flexible printed circuitry (FPC) connectors available on the market today offer many features that are critical for use in tight packaging applications.  Their compact size offers space savings that are ideal for mobile device applications, such as the use of FPC connectors between PC boards and LCD modules.

0.25_FPC-0909FPC connectors feature a ZIF actuator, which allows for repeat cycling with minimum wear.  These miniature connectors come in various fine-pitch options, including push-pull and flip-type actuators, which are pre-assembled covers that secure the connection between the FPC and the connector terminals.

Some connectors are offered with dual-contact design, eliminating the need to order two different types of FPC connectors for applications that require a top-contact style on one board and a bottom contact on the other board due to cable-configuration needs.  Some products offer a unique FPC lock that helps provide positioning and cable retention, while keeping the cable in place to facilitate insertion.

In summary, FPC connectors offer flexibility in board design in tight packaging.  They also save costs by offering a one-piece solution that does not require a mating connector such as wire-to-board or board-to-board connectors.


Connector Type
Features

Low Cost
Performance/Reliability
Small Pitch/Size
Flexibility
Notes
Micro Coax

High speed signal
FPC–to-Board

Low profile, Reduce part count
Board-to-Board

High density, Low profile

Micro Coax Wire-to-Board Solutions

The multi-pin micro coaxial wire-to-board connection system is in high demand given the massive data transactions that occur in tightly packaged mobile devices.

MicroCoax_3_NoWords_300Flexible printed circuitries (FPC) have been used to connect high resolution LCD units to the main keypad of flip style mobile phones.  However, these flex solutions have issues such as electromagnetic interference (EMI) and insufficient mechanical durability and flexibility.  For example, the LCD screens of the latest swivel phones are required to rotate almost 360 degrees in any direction, and flex circuitries cannot handle the abuse of this movement.  In order to absorb stray EMI, a ground or shield can be placed between signal traces. However, extra traces for ground take up more space, going against the miniaturization trend of handheld devices.  If shielded FPCs are used, flexibility and durability are compromised if the device has a flip or swivel hinge.
      
Fully shielded and available in multi-pin 0.40 or 0.30mm pitch with super thin 42 or 44 AWG coaxial wires, a micro coax system can provide solutions to all these problems.  Although it is more expensive than flex solutions in general, micro coax is more suitable when designers are looking for a better performance and added functionality.  A micro coax wire-to-board system is especially suited for applications such as the rotating hinge/neck area of mobile phones, digital video cameras, notebook PCs, smart phones and IP network cameras.

Micro Board-to-Board Solutions
In the housing real estate market, the three things that matter are location, location, location.  For design engineers in the PCB “real estate” market for microminiature board–to-board connectors, size, size, size is what counts.  As consumer entertainment devices, smartphones and other handheld devices shrink in size but increase in functionality, there are four dimensions that matter most when designing PCBs to connect two small PCBs together – 1) Small profile – stack height (H) less than 1.00mm; 2) Small depth –  narrow width connectors less than 3.00mm;  3) Small footprint  – end-to-end dimension of the connector (varies by circuit size); 4) Small Pitch – center–to-center contact spacing of 0.40mm or less. 

SlimStack_04_BB_NoWords_300-webThe 3G smartphones on the market today require connectors to be smaller than ever.  Design engineers have available to them connectors with a very low profile (H=0.70mm), ultra narrow depth (W=2.60mm) and very fine pitch of 0.40mm with fitting nails uniquely designed under the plastic housing to minimize the footprint and maximize the design flexibility.  For example, a 40-circuit ultra low profile (H=0.70mm) micro board-to-board connector will consume less than 28mm2  of PCB real estate.

For those worried about other PCB components being too noisy or causing signal integrity issues or interference, some micro board-to-board connectors offer external metal shielding to improve performance.  Engineers concerned about electronic devices working in high vibration applications can leverage fine pitch micro board-to-board connectors that achieve very high retention forces or provide permanent-mate solutions to withstand drop tests. 

The cost of PCB real estate is approximately $0.015 cents per millimeter. These tiny connectors pack a powerful punch for designers who must connect LCD displays, keypads, membrane switches, A/V or RF boards, modems, or GPS cards to main PCBs. 

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