In PCB manufacturing, Step and Repeat is a general term in phototooling referring to an image unit, which is stepped and repeated into multiple image units.
Background
Gent, Belgium – September 30th, 2015 – Ucamco proposes extending the Gerber format to make it more efficient in handling fabrication and assembly panels. The proposed new features will no doubt have other applications.
Printed circuit boards are fabricated in panels. The PCB is repeated a number of times on a production panel. The image file representing a panel must represent all instances of the PCB. One way to represent the PCB instances is with a so-called ‘flat’ file: the objects representing the PCB are simply copied n times in the file, each time at the appropriate place. While this defines the correct image it blows up the file size and slows down processing the image in CAM and on the production equipment. A more efficient way is to store the PCB objects only once, and add an instruction to step and repeat the PCB over the image. The current SR command in Gerber exactly does that.
However, the PCB assemblers, where the bare boards are populated with components, more and more works in panels themselves, often called an ‘array’, ‘biscuit’ or ‘assembly panel’. The PCB fabricator then ships arrays to the assembler, not single PCBs. What he repeats in his bare-board production panel are the arrays. The efficient way to represent this image is by a nested step and repeat: the single PCB is stepped into an array, and the array is stepped into the production panel. With a nested step and repeat the PCB data is only once in a file.