What is SGC?
“SGC” in today’s language simply means “small gauge coax”. However, in years past it was used by some engineers in the RF industry to describe “shielded grounded cable”. The acronym is used to describe a range of wire gauges that are of a coaxial cable construction. Coaxial cable involves the use of a wire (center conductor) that has either an extruded insulator over it or taped insulator over it (sometimes referred to as a “dialectric” material), a braided wire shield over that insulator and then an outer jacket. Another acronym used to describe the smaller wire gauges of SGC is “MCX” which means “micro-coaxial”. Micro-coaxial cable is usually termed as such when wire gauges are in the 28-44AWG, generally. Wires of that size are about the thickness of a human hair. “Micro-coax” and “small gauge coax” are often used to describe the same coaxial cable or connector.
What are SGC connectors?
Single conductor SGC connectors are used today in connectivity between antennas and circuit boards in mobile product applications. Mass terminated SGC connectors came into use in the early 90’s in the manufacturing of ultrasound devices. Today, mass terminated SGC connectors are used where flat panel displays are connected internally to a graphics card for LVDS or eDP applications. Most SGC connectors use a plastic connector body with stamped metal contacts molded into the plastic, a grounding bar for the shielding and a shell to house the assembly in. Major SGC connector manufacturers typically manufacture their own mated pair of connectors in each connector family they offer. They provide both a board mount receptacle connector (board side) which inter-mates to a plug connector (cable side) terminated onto the end of the cable. Care must be taken when ordering parts from two different manufacturers to create a mated pair. A plug from one manufacturer may not intermate to a receptacle from another manufacturer, even though they look the same to the naked eye. While most manufacturers of SGC type connectors provide both plug and receptacles as a mated pair and guarantee inter-mateability, not all manufacturers of SGC connectors are inter-mateable between manufacturers. Subtle nuances in contact plating, contact alignment and connector body characteristics can prevent two different manufacturer’s products from working optimally together. Even though there are standards in the marketplace for certain styles of SGC connectors, such as the VESA standard, there is still no guarantee of optimal inter-mateability. It is usually safest to use the same manufacturer’s plug and receptacle in your application. Make sure your manufacturing source provides the data to prove their claims to inter-mateability with their competitors. The temptation to save a little money by going with a mixed pair could cost you far more than you thought you were saving. Even if a manufacturer licenses a competitor to make the same connector, you will need proof of inter-mateability from the licensee.
How is SGC Terminated?
Working with SGC requires specialized equipment and skilled operators. Lazers are used to strip back outer jacket material to prep for soldering. Specialized soldering equipment provides the right amount of heat and solder to make good soldering connections to connector contacts or printed circuit board solder pads. Some manufacturers attempt these operations by hand and often apply too much heat, causing insulation breakdown or excessive solder wicking which compromise the performance of the cable termination. Higher end shops who terminate SGC use proprietary jigs that reduce variabilities in the manufacturing process.
What are the important quality control criteria for SGC?
Not all SGC assemblies are created equal.
Scrupulous buyers of SGC cable assemblies recognize that a cable assembly that works fine today may not work well tomorrow, even if the electrical test data for each individual assembly looks great coming in the door. With the help of a microscope, a trained eye will notice the quality of the lazer stripping, to see if the cable jacket and insulation were damaged in places critical to the longer term performance of the cable assembly. Without proper equipment and training, an inexperienced and unskilled operator can compromise the cable in ways that will not show up until higher electrical speeds and mechanical stresses are introduced.
Another area to watch for is solder wicking of material back into the space between the dialectric material (extruded or tapped layer applied to the conductor) and the jacket. This can occur for a number of reasons, including excessive heat from over-exposure to high soldering temperatures, poor quality solder material used or bad fixturing.
A third area to watch for is solder bridging. This is easier to catch before product is shipped out the door, but can be indicative of other quality problems not as easily seen or tested for.
High volume cable assembly shops tend to base their quality on go/no-go yield rates. For them, if a few do not meet electrical performance criteria during test, they are scrapped. In volume applications, for consumer products mainly, a certain level of failure is considered acceptable. Lower volume, higher quality oriented shops who support higher speed applications for test/validation or instrumentation cannot afford any failures since their products are used in very costly applications. Shops who cater to these markets are more inclined to pay attention to the quality details that ensure top performance of the cable assembly for the life of the product.
Quality issues emerge after a product hits the market when shock and vibration begin to degrade an already flawed assembly. It may not be evident at slower signal speeds, but will show as the signal speeds increase. If the cable assembly shop is approved by the manufacturer in the use of their connectors, the chances of failure are greatly diminished. I-PEX has a policy that requires potential cable assembly vendors to demonstrate competence. This ensures that their cable assembly manufacturers understand how to terminate their connectors to SGC properly.
Who manufactures SGC cable assemblies?
There are multiple sources in Asia who tend to serve consumer electronic applications in high volume and only two or three sources in the U.S. who presently terminate small gauge coax to connectors. Most low end SGC is used in consumer product mobile phones and mobile computing and are manufactured in low cost regions such as Asia. Higher end applications such as high speed test cards and ultrasound are served by U.S. based manufacturers of SGC cable assemblies. Many U.S. design centers for consumer products use U.S. manufacturers for development and low volume needs in order to take advantage of quick turn capabilities. They pay a premium for this quick turn service. Once the product goes into higher volume production in Asia, OEMs tend to migrate production of the assemblies to low cost center sources.
Here are some of the U.S. cable assembly manufacturers who specialize in SGC :
1. Mitas Electronics, Austin, TX
2. High Speed Interconnects/Micro Interconnects, Tualatin, OR
3. Tyco Medical, Wilsonville, OR
While others may offer SGC assemblies, they most likely import a pre-terminated cable assembly from an offshore supplier and then splice another connector to one end locally. In those cases, they do not control the quality processes for the SGC connector end. Make sure they are sourcing the pigtail end of the assembly from a qualified source recognized by the connector manufacturer. If you need special jacketing or sheathing for your design, the above shops also have that capability.
Contribute To the SGC Community
This information is provided as a service to the SGC community. If you are aware of any other domestic manufacturers of SGC assemblies, or any other helpful information about SGC cable assemblies that would benefit the SGC community, including corrections or updates to this information, please email us and we will add your information to our page.