Hi Speed interconnect PCB for Radar Application

Overview

Client profile –  Award winning Radar company developing commercial solutions for Traffic and Security sectors.

Description of the advance in science or technology that was being sought

We sought to design a high-speed connector polyimide PCB with controlled impedance over a tight range, for a high technology radar application. The setup, PCB Design and PCB Manufacturing procedures and systems had to allow for consistent performance of the product to a very tight and demanding criteria, as the signal timing across the multiple challenges were critical.
 
A high technology solution to connect two pieces of equipment where the communication between the two had to be in perfect sync, was not possible with existing solutions. Precise timings of signals had to be optimised by trial and error through sample production with various substrates and multiple calculations.

List of the scientific or technological uncertainties faced

Having calculated the optimal specifications for a manufactured solution we were faced with some unusual but challenging issues, namely:
  • How could we overcome the differing thicknesses of substrate that caused the machines to ‘lose’ sync?
  • Was it technically possible to achieve the tight tolerances on the PCB’s?
  • How could we eliminate the risk of variations in the copper track and gap widths going into potential failure mode?
  • Could we identify materials and techniques to allow for tight bend radii of the finished product without the copper signal tracks breaking?

 

Description of work carried out in order to resolve the uncertainties

We generated designs, drawings and specifications, and then produced prototypes. However, on testing we were achieving variable results as some failed and others worked.  We identified the errors and revised and tightened up the specifications to close out the tolerances.
In order to produce the samples we worked in conjunction with the client and our PCB partner  to  undertake calculations and with a view to parametric requirements, and available materials, designed new layouts and committed these to manufacture and impedance testing.
After the initial batch we redesigned the pcbs by incrementally tuning the performance criteria on the pcbs – this subtle change gave us the results we wanted.
Multiple calculations and samples were produced to trial connections between machines by trial and error. The initial batches made produced signals at the incorrect frequencies, which meant critical timing triggers on the machines were not activated in the time required.  The revised modified units gave the correct signal timings and are now in production.
The final inspection for both manual and setting up of automation had to be very high so additional inspection processing and QA was introduced to ensure only perfectly conforming product would be released to client and is currently in use in their production units.