A brief history of the CITS
PCB Controlled Impedance Test System

CITS100

CITS200

CITS500s

CITS500s4

CITS800s

Here is a brief overview of the evolution of the product and a summary of improvements that have been implemented to keep pace with the changes and increasing demands placed on PCB production industry.

2007 CITS900s introduced offering lower long term cost of ownership and further enhanced calibration for ultra low impedance differential transmission lines. Support for optional software modules including crosstalk testing.

2004 CITS800s introduced for with enhanced support for close coupled traces and enhanced data logging

2002 CITS500s8 introduced for application in the new RITS520a

2001 CITS500s4 firmware upgraded to measure differential track imbalance. . . .

2000 CITS500s4 supports high mix differential and single ended test

1999 CITS500s(32 bit) with calibration at 28, 50 75, 100 ohms, the ONLY TDR calibrated to measure these impedances directly.

1998 CITS500s more than doubles the throughput of earlier CITS

1995 CITS200 first CITS to support differential test

1995 CITS100 for windows supports multiple tests per coupon

1992 CITS100 for Dos is where the story starts...

Impedance measurement made easy

1992

The UK Ministry of Defence and Defence Research agency, along with several UK PCB fabricators identified a need for an easy to use production test tool for PCBs using transmission line technology (controlled impedance), in its infancy at this time, but with growing demand from the military communications and instrumentation sector.  Polar worked closely with colleagues in the PCB industry and developed the first Polar CITS — the CITS100 for DOS was released in 1994.

1994

Simplicity, ease of use and reliable operation on a PCB shop floor made the CITS100 an ideal solution compared to the alternative of using a laboratory oscilloscope TDR to make measurements. Instrumental at Polar in the early years of CITS, Andy Burkhardt worked tirelessly with the PCIF (Printed Circuit Interconnection Federation) and BSI ( British Standards Institution) to help develop a standard for use in the UK PCB industry for controlled impedance PCBs. Also deeply involved, Dennis Price (then at MEPD in Selkirk ) provided insight, help and information in developing a product that was a 100% fit to the industry requirements of the early 1990s. Alongside Andy and Dennis, Gary Rich engineered the CITS measurement platform with the stability, robustness and ease of use needed for regular use in a PCB fabrication environment. In the early 1990s boards requiring transmission lines were few and far between, and maybe only had one or two critical tracks (typically around 50 Ohms); nevertheless, if they were incorrectly fabricated the resulting PCB assembly may not function correctly, with all the consequential costs involved.

1995

Now boards begin to appear with 2, 3, or maybe even 10 critical traces, sometimes with 2 or 3 impedances. CITS100 for DOS with its single test architecture begins to struggle in keeping up with these new demands.  A new architecture based on Windows 3.11 starts to develop, building in the ability to link tests in a sequence (macro test mode); this development leads to CITS100 for Windows. All the ease of use of the CITS100 in a Windows environment.

Higher speeds, lower voltage logic and the ongoing pressure to extract more performance from economic base materials, along with the relentless growth in the telecoms industry for high speed backplanes, leaves fabricators crying out for an easy to use production tester that can also support differential test. Now the challenge to produce an economical differential test solution leads to some research along with John Reeves at University of Portsmouth (UK) to investigate mathematical techniques which can extract differential impedance with a single ended TDR. The result is enormously successful, and after long correlation studies with lab TDR  the CITS200 is released, the first Polar CITS to support differential test.

(About this time PCB fabricators start to ask for an easy to use calculator which results in the development of Zcalc — that is another story — which leads through CITS25 to the latest Si6000b.) However it is interesting to note that Phil Hamilton at D2D (now Celestica) gave a copy of Zcalc to a colleague at Salford University; this colleague just happened to be Dr Alan Staniforth — little did we know at that time just how valuable a resource Dr Staniforth would be in the future of CITS...  (Dennis Price tells us that Phil has now retired and is spending more time on his hobby of hand building clocks.)

1996

By now Polar is becoming synonymous with controlled impedance test, and the launch of the Polar website www.polar.co.uk (now polarinstruments.com) lets us share controlled impedance knowledge on a world stage.  Demand continues to grow for faster, more accurate test and 1996 marks the launch of CITS500, which consolidates all the previous improvements in the CITS100 and 200.  However progress is not always as smooth as planned and changes made to the 500 to improve the ability to withstand more electrostatic discharge result in a loss of electrical performance. The 500 is recalled and modified back to the same standard as the CITS200, meanwhile work continues on a solution that will give high static protection, and maintain electrical performance. Richard Smith at Polar Instruments, Inc. works with Andy to introduce the CITS in the US market where CITS is set to become industry standard for bare board impedance measurement.

For a glimpse of the Polar web site in 1996 try:

web.archive.org/web/*/http://www.polar.co.uk

1998

CITS now well established in the USA and the UK,  the industry moves from sample based testing to needing to test a coupon on every board (this because of the increasing value of high speed boards and the need to ensure transmission line performance before further value is added). This rapid increase in demand led to the CITS500s which doubled throughput compared to previous CITS. At the same time Asia Pacific was a market yet to be explored by Polar, and Taiwan with its strong PCB industry seemed a good place to start. Our Taiwan distributor Precision International Corp singularly promoted the CITS500s as the workhorse of controlled impedance test in Taiwan and Mainland China.

1999

Now with differential testing and fast throughput, the next challenge came from those mysterious enquiries about 28 Ohm impedance, and with a very tight tolerance, connecting all the requests together led to Rambus, who were at the time developing high speed memory architecture for the PC.  Work with Rambus and Intel helped us develop two very necessary enhancements, one a 4 point calibration scheme based on traceable reference air lines, and the other an automated partner for the CITS — the RITS500s. CITS500s(32bit) was a radical revision of the CITS software designed from the outset to test multiple coupons with impedance from 20 to 120 Ohms single ended and from 40 to 150 Ohms differential. Here Dr Staniforth further extended the calibration mathematics to ensure linearity out to higher impedances.

2000

CITS500s and RITS500s powered Polar through the Y2K telecom growth cycle...the CITS500s4 rolled out to bridge the gap between manual and automated systems, proving very popular in Germany where controlled impedance board manufacture starts to take off rapidly.

2001 – 2002

While the PCB industry suffered from its worst recession in memory, work continued behind the scenes and on the other side of the recession the future still looks high speed to us. Though industry slowed, the demand for impedance test continues to increase with an emphasis on fully automated coupon and coupon in board test. 2002 marks the release of CITS500s8 primarily for use in our automated platforms.  Behind the scenes subtle enhancements continue to keep the CITS at the edge, for example the CITS now automatically checks that differential traces on fine line PCBs are symmetrically etched.

2004 On

Whilst the future is hard to predict, the demand for high speed boards is again growing steadily, but with an emphasis on performance and cost effectiveness. The sixth generation CITS the CITS800s arrives on the market, with an emphasis on accurate measurement of close coupled traces on multiple dielectric PCB substrates. The new CITS800s continues to employ the same easy to use software, which is further enhanced by direct links to real time statistical process control.

Martyn Gaudion 10 May 2004