GENT, BELGIUM -- The caretaker of the Gerber electronics data transfer format is proposing efficiency improvements for handling fabrication and assembly panels.

Ucamco has embellished the Gerber language with nested step-and-repeat to accommodate panelized boards at assembly without severely expanding the file size. A draft specification is available for review and comment.

The revisions focus on the step-and-repeat process for creating multiple identical boards for a single panel (array). Repeating the same image several times increases the file size and slows CAM processing, a problem Gerber resolves by storing the PCB data only once, along with instructions to step-and-repeat.

This works well at the fabrication level but not assembly, where the arrays are "nested," Ucamco said in a press release announcing the revisions.

"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, which the current SR command in Gerber does."

As assemblers process migrate to processing panels (arrays) as opposed standalone boards, the images are represented 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 again is contained only once in a file.

"The problem with the SR in Gerber is that it supports only one level, no nesting. So one has to flatten either the array or the working panel. The resulting big files can become a problem when a small but complex piece of electronics such as a smartphone is fabricated."

Ucamco is addressing this issue by extending the Gerber language with nested step-and-repeat. Tests performed with Via Mechanics in Japan reportedly demonstrated "dramatic" productivity increases in writing and reading the files as well as in processing them.

Ucamco has created a new command, called SN, to accommodate legacy Gerber readers that do not yet support nested step-and-repeat and might, when receiving an SR with nesting, not notice this and produce the wrong image, without warning.

Another issue, Ucamco said, is that the step-and-repeat only allows to repeat object blocks in a regular array. To allow more general repeats Ucamco introduced a command called AB that creates a block aperture that can be flashed in any location and orientation.

New attributes unequivocally identify the fabrication panel, assembly panel, and the single PCB.

"Nested step and repeat and block apertures will make Gerber more efficient with panelized data. Further more, the block aperture is a powerful general constructs that will no doubt have many other applications. Together, they are a powerful extension of the Gerber format," Ucamco said. 

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