How are high-speed copper wires terminated today?

In our last blog post, we discussed traditional methods of terminating high-speed copper wires. In today’s discussion, we’ll highlight how these processes have modernized in recent years, starting with hot bar solder reflowing.

Hot Bar solder reflowing evolved for use through an upper and lower wide opposite bar machine that did simultaneous reflowing of twin-axial wire elements of 50 pins on top and 50 contacts on the bottom of a modified MDR plug connector. This type of cable assembly was for an early version of the NumaLInk Link interface. (See the Miyachi explanation of its pulsed heat Thermode technology.) Some companies, such as MicroJoining, developed electrode probe tipped reflow soldering equipment as well as resistance welding, as can be seen in its guideline chart and tip shape information, pictured. Welding uses more power and creates a very high heat profile. Welding melts the contact and wire into a new diffused molecular crystal structure that is strong compared to solder which is in a plastic state and is not really a solid.

During the 2000s more refined and precise termination equipment for high-speed copper wires became available as smaller wire sizes and termination zones became common. CAT-8 twisted pairs are not untwisted; they are IDC’d in a special contact configuration that keep the electrical profile symmetrical for most of the patch cord assembly length. AquaFlame’s hydrogen micro-torch and its 2000°-plus micro flame was developed for high-precision solder reflow of fine contacts and wires especially for medical high-speed I/O cables. Companies like Sunstone developed opposite and parallel resistance pulse welders as well as capacitive discharge spot welders. Those are good for larger wire sizes, such as 24 AWG. Litron System’s Red Laser welding and cutting statin is an example of green environmental wire termination processing. It requires no solder, no hands and offers optical inspection and networked automation, etc. Current high-speed SFP and QSFP twin-axial cable elements are very neatly trimmed and welded using this type of equipment.

The 2010s have brought green laser welding equipment for very fine, high-volume and high-speed throughput wire terminations. Miyachi’s green pulse laser welder is an example of this up-to-date wire welding termination equipment. Green laser processing leaves very little carbon particle residues compared with older red laser welders. But green lasers tend to cost a lot more. It takes some time to learn to operate this type of equipment and to do the required calculations to determine the focal point of the laser energy slightly within the wire. Laser welding of wires directly to PCB pads is done with a very precise process set up. Fine optical comparators and cameras are embedded to achieve highest yields and stored images, etc. Often the twin-axial wire tips protrude and the end is no longer

a round cylinder but a precision formed tip that optimized SI performance. This special wire-formed tip is designed closely to work with the pad shape and escape routing trace design. The wire is made of very smooth, oxygen-free copper with very smooth silver plating to support the skin-effect of high frequency signaling. Hugely challenging in the near future will be the need to terminate fine wires carrying 100 Gbps signal in volume cable assemblies. Extra special care will be needed to handle geometry transition zones and disturbances relative to electrical wave speeds running on it.

Because exact detailed wire termination methodology and inline high-speed testing of cable assemblies is very competitive, very proprietary and is a primary factor of corporate profitability, this author cannot share certain specifics but would be happy to answer many possible questions.