Reverse Engineering Circuit Boards with ScanCAD

Reverse engineering a circuit board is usually a difficult task, but ScanCAD has combined a very high resolution scanner with dedicated application software tools (Figure 5-1) to interpret and translate a scanned image and extract relevant information. Based on the scanned images and component information, the circuit board can be reconstructed layer by layer to develop the board and schematic.

It is worthwhile to determine the level of circuit board re-engineering to be achieved. Is the objective to simply get enough Gerber and drill files to manufacture bare boards? For simple, hand assembled boards, this may be enough. Is the goal to reverse engineer to the point where you can manufacture bare PCBs and have component placement data? To manufacture and assemble circuit boards using surface mount technology and pick and place machines, this may be enough. Or finally, is the goal to have enough data to load into a CAD system and re-create the schematic? If upgrades or modifications are necessary, or there are obsolete parts, this level of effort may be necessary. These three levels will be discussed.

There are several compelling reasons forcing a consideration of reverse engineering. Old artwork is not salvageable, multiple revisions and poor documentation could have confused the integrity of the design, and vendors go out of business. Also, it can simply be less expensive to reverse engineer a circuit board and product than to redesign the board. It is also not uncommon to discover that a product that was thought to have a limited life maintains its popularity.

Using ScanCAD products, the following sequence of steps is used to generate the information necessary to re-engineer a circuit board: Gerber data, drill/route data, and the centroid/BOM information.

• Scan the loaded PCB with the components attached and get the BOM information.
• Strip the components.
• Scan the bare printed circuit board.
• Delaminate the PCB to the next layer and scan again.
• Delaminate to the next trace layer and scan again; continue for all layers.
• Create Gerber/drill/routing data for all layers.

  The ScanFAB application software will generate enough information to manufacture the bare circuit boards. If data is required for both assembly and component placement, the additional ScanPlace application software can generate this necessary information.

  With the ScanPLACE software loaded, having completed steps 1 through 6, continue in the following manner.

• Extract component centroid/BOM data with ScanPLACE.
• Output all the Gerber, drill, routing and component BOM information using the ScanPLACE software.

As seen in step 4, gathering the trace information is destructive for the circuit board. For a multi-layered board, the delamination operation takes some care. The physical removal of each layer to get the trace information can be done by computer numerical controlled (CNC) machine tools, hand sanding, or a combination of both. The fastest way would be to use a CNC machine to mill away the surface a few thousandths of an inch at a time, but care must be taken to keep the board dead flat and supported during the milling process.

As a final step in the re-engineering process, schematics and CAD information can also be developed. ScanCAD ConvertPLUS Automated Reverse Engineering (ARE) and Electronic Design for Windows (EDWinXP) application software can be incorporated to provide schematic generation and CAD upload capabilities.

Using modern equipment and software from ScanCAD International, re-engineering a circuit board is a reasonable alternative to a total redesign. Improvements in the application software are the primary driver for this increased efficiency. The process itself can be measured in days and cost from a few hundred to a few thousand dollars depending on the board. For more information or for a demonstration of this technology, contact Mike Prestoy at the EMPF at 610.362.1200, extension 241.