Industrial customers often find themselves in a situation where they have hardware samples of a Printed Circuit Board Assembly (PCBA) but the engineering design and fabrication information has been lost.

Engineering design information would include schematic diagrams and bill of materials.  Fabrication information would consist of assembly drawings, fabrication drawings and gerber files. All of these documents are required in order to maintain full ownership of the PCBA design.

The result of the loss of this critical design and fabrication data is that the customer no longer has the ability to build, maintain and update the design to meet changing needs.  In other words, intellectual property ownership has been lost.

Reverse engineering is the process of re-creating the engineering design documentation and fabrication files from a hardware sample PCBA. This process restores the full intellectual property ownership.

What is the reverse engineering process?

Component Identification & BOM Generation

The first step in any Reverse Engineering effort is to identify all of the components on the PCBA. This identification is normally done by visual inspection and by device measurement. Once identified either by part number or value, each component is added to a preliminary Bill of Materials (BOM) along with the reference designator for the component. The reference designator is normally read from the PCBA sample silkscreen labeling if it is visible. Component choices to complete the BOM must be made by an experienced design engineering team with knowledge of the component capabilities and the desired system design goals.

Netlist Generation

The next step in the process is to determine how these components are interconnected on the sample PCBA. As each node to node connection is discovered the connection is added to a PCBA Netlist. The Netlist is a point to point list of all of the connections on the PCBA. The discovery of these node to node connections can be done in one of two methods:

Node to Node Probing:  This method of determining node to node connections employs either manual probing by a technician or automated probing by a flying probe machine.

“The goal is to generate an accurate net list that defines how each of the components on the customer hardware sample are connected to each other,” said MJS Designs Director of Engineering Chuck Chase. “On simple boards, this net list is generated using manual probing and on more complex boards the net list is generated using a flying probe tester that takes a continuity measurement between all node combinations to determine which are connected.”

This node to node method of netlist generation supports a form, fit, and function (FFF) reverse engineering end result. The FFF netlist generation is used in cases where only a FFF end result is desired. This netlist generation does not support the “exact” duplication of the board, layer by layer.

Delamination and Optical Scanning:  This method of determining node to node connections involves grinding or delaminating the PCBA one layer at a time to reveal the interconnections on each PCBA layer. Normally, as each layer is uncovered, the layer connections are optically scanned. This produces an exact duplicate of the layer connections which can be used to produce an “exact” duplicate of the board.  Obviously, this is a process that results in the destruction of the original sample. This type of layer duplication is time consuming and very costly and is needed only in certain circumstances to avoid re-qualification requirements for safety critical hardware.

Regardless of the netlist generation method used, the net list is reviewed by multiple individuals for accuracy to ensure that all connections are transferred from the original design.

New Schematic Generation

Once the component identification and netlist generation steps are complete, the components and node to node connections are entered into an electronic schematic capture tool. The resulting new schematic design formally documents the electronic design that exists on the PCBA sample hardware.

Printed Circuit Board Design

When the new electronic schematic design is complete the printed circuit board design phase begins. The PCB design phase of the project defines the interconnect traces that connect the nodes in the design. Many of the design choices must be made by an experienced PCB design engineer. For example, to ensure the traces are designed to handle the desired current loads and in some cases provide a specific trace impedance.  The PCB designer also generates an assembly drawing that shows component locations and reference designators. A fabrication drawing is created which defines the PCB layer thicknesses and the hole locations and dimensions. Gerber files required for the manufacture of the bare PCB are also generated.

PCBA Fabrication and Test

In the final step of the process, the new PCB design is manufactured using the latest fabrication files and documentation. The components are procured and assembled on to the bare PCB board to complete the printed circuit board assembly.  Engineers test the new design in a laboratory to verify the new PCBA operates as expected and matches the original design in performance.

“The new board design is tested both electrically and functionally to verify that it performs similarly to the original design specification,” Chase explained.

The new PCBA is production ready once the re-design meets the needs and expectations of the client.

Why would you reverse engineer a part?

Reverse engineering serves a number of purposes and has been used in nearly every industry and type of manufacturing imaginable.

Companies can use reverse engineering to analyze and update obsolete designs, defend patents by reverse engineering a competitor copy, create a replacement part when the original manufacturer no longer exists, discover the inner workings of a part when documentation has been lost, and more.

The engineering team at MJS Designs works with clients to meet their project needs, including electronic design services, electronic product development, and printed circuit board design. Learn more about our electrical engineering services at mjsdesigns.com/electronic-engineering-services.