For both the consumer electronics and automotive industries, the main design focus for connectors is on miniaturization and simplification.
By James Higdon
One size does not fit all, especially when it comes to connectors used in consumer electronic products, such as cellular telephones, televisions, and digital and video cameras. Today, the main design thrust is toward miniaturization and simplification. J.S.T. Corp. is seeing a growth rate of about 15 percent per year of customers that want smaller connectors. Although some industries are still satisfied with connectors in the 1.5 to 2.0 mm-pitch range, the consumer electronics industry is driving miniaturization at an astonishing rate.
Specifically, original equipment manufacturers (OEMs) want smaller connectors with smaller pitch. Also, they want to reduce the number of connectors used, which results in higher pin counts per connector. Connector pitch size is down to 1.0 mm (0.039") for wire-to-board connectors in both crimp and insulation displacement types. Board-to-board connectors are down to 0.4 mm (0.016") pitch. Flexible printed circuit connectors have as low as 0.3 mm (0.012") pitch.
An Under-the-hood Revolution
Miniaturization of electronic packaging in the consumer electronics market is visually obvious. People walk down the street using devices that are just a fraction of the size they were only a few years ago. Not so obvious is the miniaturization revolution occurring in the automotive industry. It is "all under the hood" so to speak. Automotive engineers are facing 2.0 mm or less contact spacing. This is compared to 1.0 mm or less for the telecommunications industry, but automotive miniaturization requirements are increasing. With more and more computerized control of car functions, space behind the dashboard or engine compartment is highly prioritized. Just reducing the size of printed circuit boards (PCBs) by 1 sq in. is considerable.
Automotive miniature connectors must still face harsh environments. The most critical connector environmental considerations today are for the automotive industry. Consider car warranties approaching 10 years or 100,000 miles, and what that can do to mean-time-between-failure specifications. Also, hostile automobile environments play havoc with shock, vibration and temperature requirements.
Wire Harnesses
Wire harnesses are a strange breed when it comes to miniaturization. For instance, a few subcontractor companies that have been outsourced by major automotive manufacturers largely control wire harness manufacturing in the automotive industry. Connector suppliers wishing to do business with this market must have a line of miniature connectors that can be readily applied to automotive wire harness needs. These connectors must meet:
- Mistake-proof terminal insertion needs
- Terminal insertion force needs
- Terminal position assurance.
Rather than compete with wire harness suppliers, connector manufacturers can also offer value-added services. In cases where new state-of-the-art miniaturization is desired, in addition to designing the new connectors, connector manufacturers can also offer equipment that can assemble the connectors and wire harness. This becomes a value-added type of service to wire harness companies, including, in some cases, actual assembly of the complete harness.
Insulation displacement connectors (IDCs) offer fully automatic wire harness assembly. The IDC housing is injection-molded, and the IDC terminal is stamped and wound on reels. The terminals are inserted into the housing via an assembly machine. The tooling is expensive, but can be amortized (over connector life) to keep manufacturing costs (piece price/harness price) reasonable.
Pick-and-place Connectors
Another aspect of smaller connector size is problems associated with surface mount manufacturing. For high-speed, automated manufacturing, connectors that are pick-and-place capable and reflow-temperature stable are needed. This increases the cost of the connectors because of the tape-and-reel packaging and the high-temperature material. The ultimate manufacturing/labor cost savings, however, more than justifies the higher initial cost.
Reflow Soldering
Miniaturization can also cause special problems with using reflow soldering. As connector density increases, so does the problem of contact bridging where excess solder shorts the contacts that should be individually soldered to the PCB. Proper connector placement is critical because even a slight skewing makes it difficult to solder properly. This can introduce circuit malfunction or even destruction.
Lack of enough solder is also a problem. In this case, the contacts fail to become connected or the connection ruptures under normal handling.
Manufacturers are becoming much more consistent with their reflow soldering techniques. They are carefully controlling solder formulation, temperature and flow rate to achieve optimum results. And they look for connectors specifically designed for reflow applications.
Reflow solder miniature connectors that have leads designed that force the connector to be pulled down into the molten solder pool as it cools to achieve positive connection integrity have been developed. The plating and bowed shape of these leads allows them to actually be pulled down toward the pad during the soldering process. Just five years ago, through-hole leads were bent flat, then surface mount soldered. Now, leads with special tail designs that help eliminate bridging and other nonsoldering issues are available.
An Evolution of Miniatures
Miniature connector development is an evolutionary process. Connectors are seldom designed from scratch to exact customer specifications. Normally, a customer wants a connector similar to an existing line, except with tighter pitch and a lower profile.
The connector manufacturer then goes back to the drawing board and finds out what it will take to fulfill the customer`s requirements. First, it is determined if it can be done with present state-of-the-art materials and processes. If not, special research is required.
This is how breakthroughs in connector technology are achieved. For instance, a lot of high-density, fine-pitch connectors requiring unique contact designs, materials and platings have been developed for the video camera industry. These advances can now be used in additional markets. In many cases, a little ingenuity applied to a present design brings a new design to fruition. Then, it is a matter of amortizing manufacturing costs over the quantities involved.
The Future Is Smart Connectors
Smart connectors are coming, for both the consumer electronics and automotive industries, but it is still unclear how it all will settle out. OEMs are thinking that they will just add connectorization to their bag of tricks. Connector manufacturers are thinking that they will just add smart electronics to their bag. Probably, there will be a meeting of the minds somewhere in between. The result will be electronics built into the connector that will sense what signals are being connected to it and route the signals to a preplanned array of output pins. This will require built-in signal recognition electronics and pin-distribution (switching) capability.
Automotive applications are where one main power distribution system will be routed on an as-needed basis. For instance, if the windshield wipers are turned on, electronics within the connector will automatically sense the switch actuation and distribute power to the wiper motor. This same connector would automatically sense actuation of the window switch and route power to that motor. It is possible that the pin output could depend on both input and output electronics. The benefit of this would be reduced cable weight and complexity, plus reduced connector size and pin count. Efforts to reduce weight and standardize cabling are, of course, ongoing in the automotive industry.
Connector manufacturers are striving to make their products smarter, smaller, lighter, and more versatile and reliable. The next century will surely see new materials, processes and manufacturing techniques that will help to reach these goals. 3
JAMES HIGDON is an engineer, J.S.T. Corp., 1957 S. Lakeside Drive, Waukegan, IL 60085; (800) 947-1110; Fax: (847) 473-1373; Web site: www.jst.com.
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The Series HO connector is a single-piece, board-to-board connector for mating PCBs.
It permits adjacent board spacing of 3.9 mm (0.154").
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The Series ASR connector is an ultra-compact, disconnectable, insulation displacement, wire-to-board connector with 1.0 mm (0.039") pitch.
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The Series CN connector is a compact wire-to-wire or wire-to-board connector designed specifically for Global Positioning Systems.
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The Series DMX connector has a 5.4 mm (0.213") height and 1.0 mm (0.039") pitch.
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The Series SCG connector is a 0.4 mm (0.016") connector for Subscriber Identity Modules.
SPEC SHEET
End Applications: Consumer electronics products, automobiles
Related Products: Wire-to-board, board-to-board, flexible printed circuit and smart connectors; PCBs; wire harnesses; solder
Main Point: Connector manufacturers are striving to make their products smaller and lighter for the consumer electronics and automotive industries. OEMs are demanding smaller connectors with smaller pitches. They also want to reduce the number of connectors used, resulting in higher pin counts per connector. Miniaturization affects all aspects of design and manufacturing, from contact spacing and harsh environment requirements to wire harnesses and the reflow process.
