PCB Reverse Engineering Guide

PCB reverse engineering, also known as cloning or copy, is essentially the process of extracting the original information from electronic products’ circuit boards through various scanning and disassembly techniques and copy them. As technology has advanced, reverse engineering has undergone significant changes. Nowadays, it involves not only simple information extraction and cloning but also more complex tasks such as modifying original information, extracting three-dimensional data, copy components, and decrypting chips. In this article, TechSparks will delve into PCB reverse engineering, covering its legality, the cloning process, and methods to prevent cloning, among other aspects, to help you understand and master this technology. Let’s dive in!

Is Reverse Engineering Legal

When discussing the definition of reverse engineering, a prominent concept is “copy.” However, the term “copy” often carries negative connotations, leading some to question its legality. In reality, it’s a widely accepted technique because it not only speeds up the product development process but also provides ample opportunities for learning. However, before you embark on cloning PCB, it’s essential to understand and comply with relevant laws and ethical guidelines such as the Copyright Directive and the Digital Millennium Copyright Act (DMCA) to avoid legal risks.

For instance, cloning projects must not involve circumventing any form of copyright protection measures or digital rights management systems to ensure that the original design’s copyright protection is not infringed upon. In simple terms, all designs or products generated during reverse engineering should be independent, rather than merely copying or adapting the original design to obtain derivative works covered by the original copyright.

Moreover, all analysis and research during the project must be based on legally obtained information, refraining from misappropriating or disclosing others’ trade secrets. Ultimately, you should only analyze information obtained from public sources or conduct analysis with explicit permission.

Why is PCB Reverse Engineering Important

Fundamentally, PCB reverse engineering involves dismantling a complete PCBA (Printed Circuit Board Assembly) to its pre-assembled state, enabling designers to study its manufacturing methods or operating principles. This process is highly beneficial as it helps designers quickly identify flaws, enhance security, or understand the underlying mechanisms of the technology.

Moreover, in situations where PCBA fail, and the original files cannot be traced due to various reasons, reverse engineering enables systematic analysis of the PCBA to identify components and their connection methods. This information can then be used to reconstruct production data, providing theoretical and data support for troubleshooting, maintenance, and other tasks.

For businesses, developing a new product is challenging and often requires starting from scratch, from conceptual design to manufacturing. PCB cloning accelerates this process by duplicating and modifying existing designs, allowing companies to iterate and update their products faster, gaining a competitive edge in the market.

Furthermore, mastering reverse engineering technology and understanding its principles and processes enable companies to better protect their PCB from being copied by competitors. Importantly, it allows companies to obtain manufacturing data, ensuring they can independently copy PCB board rather than solely relying on manufacturers, thus gaining better control over their PCB requirements and avoiding dependency.

Challenges of PCB Reverse Engineering

With the continuous advancement of technology, an increasing number of PCB employ multi-layer structures, containing hundreds or even thousands of components in extremely compact areas. This complexity requires designers to exercise more patience and time when tracing connections and reproducing paths.

Beyond layout complexity, the core challenge lies in integrated circuits, which serve as the brains of PCBA boards, controlling the operation of the entire circuit board. However, modern chips often come with security features to prevent unauthorized access, making chip decryption exceptionally difficult. Additionally, some chips may be custom-made or obsolete, making them difficult to identify or procure, further adding to the complexity of the reverse engineering process.

How to Reverse Engineer a PCB

Step 1: Preparation

When obtaining a circuit board nead for reverse engineering, avoid immediate disassembly. First, conduct a comprehensive analysis and inspection of the circuit board, recording key information such as component designators, package types, and temperature grades. Before desoldering components, ensure the PCBA board surface is clean and perform high-resolution scanning (at least 600 dpi) to ensure clear visibility of components and PCB silkscreen for backup purposes.

Step 2: Desolder Components and Create a BOM (Bill of Materials) Table

Prepare a record table, label component information, and attach double-sided tape below the table to sequentially paste the removed components to their corresponding positions to prevent confusion or loss. Desolder components in descending order from high to low, starting with resistors and capacitors, and ending with chips. After each batch of desoldering, scan and record before proceeding to the next batch. When using a hot air gun to heat the soldering area, use tweezers to hold the components to prevent them from blowing away. After removing all components, use a multimeter to measure their values (measure after components cool down to ensure accuracy) and input the data into the computer for archiving.

Step 3: Surface Solder Removal

After desoldering components, the PCB surface may have some residual solder. Use tools such as a soldering iron, flux, and desoldering pump to remove excess solder. First, heat the soldering iron to the appropriate temperature and apply flux to the areas where excess solder needs to be removed. Use the soldering iron to heat the solder until it completely melts, then quickly use the desoldering pump to suck away the melted solder.

Step 4: Cloning Software Operation

Scan the surface layer images and label them as top layer and bottom layer, then convert them into bottom maps recognizable by the software. Based on the bottom map, first create component packages (including silkscreen, pad diameter, and positioning holes). After completing all component packages, place them in their respective positions, adjust the characters to match the font size, font type, and position of the original board, and then proceed to the next step.

Use sandpaper to remove the silkscreen, ink, and characters on the PCB surface, exposing the copper layer (the direction of sanding should be perpendicular to the scanning direction of the scanner), or use heated alkaline solution to remove ink.

For cloning multi-layer PCB, the sequence should be from outer to inner layers. For example, for an 8-layer PCB, clone the 1st and 8th layers first, then the 2nd and 7th layers, and finally the 3rd and 6th layers.

During the operation, always pay attention to the error between the image and the actual board, and adjust the size and direction promptly. After ensuring consistent dimensions, adjust the component positions one by one to fully overlap with the bottom map, facilitating subsequent hole drilling, wire tracing, and copper laying.

Step 5: Inspection

After completing the cloning, it is essential to inspect its quality. The most effective way is to use image processing software, PCB drawing software, and physical circuit connections to make precise judgments. For high-frequency PCB, impedance plays a significant role. In physical cases, impedance testers can be used for testing, or the PCB can be sliced, and a metallographic microscope can be used to measure copper thickness and layer spacing. Additionally, analyze the dielectric constant of the substrate to ensure that the PCB parameters match the original board.

How to Prevent PCB Reverse Engineering

To protect design copyrights and prevent illegal copying, you can take some effective measures. These techniques not only increase the difficulty of copying but also reduce the interest of potential copiers.

Firstly, consider using fine sandpaper to grind off the model numbers on chips. While some common chips may be guessed by tracing power and ground pins, this method is highly effective for less common chips.

Additionally, potting is also a viable option. Cover the PCB and all its components with epoxy or ceramic adhesive. To increase complexity, intentionally set up a few flywires as traps, which will be damaged during potting, making it impossible for copiers to reverse the process.

Moreover, incorporating components with no markings or only codes into the design, and serially connecting resistors above 60 ohms on signal lines can increase the difficulty of replication and consume the copier’s patience.

For high-end products, you may opt for chips like ATMEL’s AT88SC153, which cannot be reverse-engineered as long as the software cannot be disassembled, or consider ACTEL’s CPLDs, which are uncrackable, or use techniques such as buried and blind vias to hide through-holes inside the board.

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