Xact Registration Protocol (XRP)

The project aims to improve yield in a high technology multilayer Printed Circuit
Board (PCB) manufacturing operation. Specifically we will target a major area of
PCB yield loss - "registration": that is the ability in the manufacturing process to
ensure that the multiple layers in the PCB align accurately and predictably to
each other. As the technology requirement of PCBs increases to cope with high
product technology and materials become thinn,er and more unstable, it becomes
progressively more difficult to align these multiple layers.
The PCB manufacturing process is, by necessity, a multi-step operation involving
mechanical and/or chemical processing. Each process step involves one or more
machines- each with a specific role to play for that process step. The majority of
such machines are designed and built by specialised companies focussed on
their "area of expertise" and there is no single machine manufacturer who can
supply systems for the complete manufacture of PCBs. Each process step in the
manufacture of PCBs is therefore handled in isolation and although data related
to the PCB at that step is available, it is generally used solely at - and for - that
process and because the data comes from multiple machine systems, there is no
standardised data format for communication.
XACT's business is focussed on solving PCB registration. Our systems have
been adopted by the leading PCB manufacturers globally. Our product range
(GeminiX) uses a link between the CAM system and just one of the PCB
manufacturing process islands: the x-ray optimiser 1 . On a timeline of PCB
manufacture for a standard product one could place this process at about 60% of
the total manufacturing time. By collecting data from that process we are able to
gain a picture of the registration status at that process step. This allows us to
build a predictive model of the total material distortion that is present at that point
in the process. We then compensate the electronic data at CAM for a production
batch to minimise the effect of distortion that will occur to that point in the
process. Our system is a feedback based system.
The above data collection point was chosen because the overriding total
distortion is visible at that process, however, it is the case that we are only
measuring the "sum of all previous process distortions" and cannot isolate
specific upstream process effects. Moreover, we are unable to monitor or
influence any process influence that is "downstream" of the current measurement
point.