What is PCB Reverse Engineering?
As a general rule of the thumb, you can gain enormous information concerning anything by deconstructing the components.
This is the basic concept of reverse engineering.
Reverse engineering not only applies in hardware engineering, but the concept also plays a critical role in computer software development and human DNA mapping.
In printed electronics, PCB reverse engineering implies to move backward from the PCB to schematics with the aim of understanding and analyzing the printed circuit board.
PCB Design
The analysis will enable you to generate documentation, determine the design and operation concept of the PCB, or re-manufacture it.
Oftentimes, the documentation even enables you to better your product to exceed competitors.
The main reason of reverse engineering PCB is to comprehend how components interconnect. One step in that procedure is to access and take pictures of every layer of the PCB.
When you patch together all the layers, you will be able to identify a complete circuit layout.
Equipped with this set of information, you are capable of identifying areas where you can add new functionalities or features, locating specific connections, or cloning the design.
Additionally, the information allows you to create a schematic diagram making you understand the working principle of a product.
Nonetheless, reverse engineering PCB is obviously not a simple one-day training session. It is not as easy as knowing it all merely from a search engine online. The process requires years of experience in electronic design and mastery of how other engineers model their circuits.
Why Learn the Art of PCB Reverse Engineering?
Usually, engineers confuse between PCB reverse engineering and PCB clone designs. In PCB cloning, you copy the exact design of the target circuit board.
So, if reverse engineering PCB is not similar to producing a clone; then what is it?
Actually, moving from PCB to schematic enables you to develop a PCB prototype that has the same working principle as the original printed circuit board without being a replica.
Let us look at the reasons why it is important to know about PCB reverse engineering;
PCB Reverse engineering
·Substitute obsolete components with cost-effective modern components
One aim of PCB layout reverse engineering is to establish and replace obsolete components.
These parts may have been utilized due to their market availability at the time of PCB manufacturing.
But, we are all informed of the rapid evolution in semiconductor technology that the original components used may have gone out of date or experience environmental compliance challenge.
Reverse engineering PCB to schematic enables you to boost the functionality of electronic circuitry.
You can utilize state of the art components that are economical and readily available.
·Analyzing and understand the original PCB
PCB reverse engineering is conducted for the purposes of learning and education in order to master technology better so that you can propose improvements publicly.
PCB Analysis
PCB deconstruction and netlists allow you to disassemble the components to examine how the circuit, process, and whole systems operate in an integrated setup.
At the circuit level, you can study the interconnections at the components and transistor levels.
At the process level, you are able to know about the layout features and patented semiconductor’s packaging.
This helps you understand the technology and materials used to build the integrated circuit. System evaluation meets the purpose of comprehending the role of the PCB in any system.
·Correct the corrupted files or move to a new platform
Your current PCB design may be having some corrupted files which require you to modify.
Equally, there may be a pressing need to move to a completely new platform yet you do not have the PCB design files, schematics, netlists and bill of materials.
These are essential for system updates. This is the point where PCB reverse engineering comes into play.
·Copying the design
Yes, it is possible to copy designs through PCB reverse engineering.
However, it is exceedingly cumbersome to mimic exact designs due to the complex VLSI designs employed in multilayer PCBs.
You can use automated X-rays and photocopy but still, there will be deviations in the re-engineered circuit which would impact negatively on the function of the PCB.
It is essential to note that most copyright regulations permit companies to replicate functionality and not the design of PCB.
Therefore, you must disclose the new PCB details if you intend to copy the design. Additionally, you need to identify trace routing modification and application of upgraded PCB electronic components.
Best Way to Reverse Engineer a PCB
When it comes to reverse engineering PCB, you can adopt many processes and procedures.
It will all depend on your manufacturing capacity and capability.
In this section, I will take you through some of the best techniques to reverse engineer PCB.
Let’s dive right in:
PCB Layout
Manual PCB Reverse Engineering Process
At times, advanced techniques of reverse engineering PCB are time-consuming and expensive.
In practice, most PCB reverse engineers undertake manual procedures to know how a particular embedded system is made.
Here I illustrate manual workflow on how to reverse engineer a PCB.
i.Identify Components
The most fundamental thing you should identify is the electronic components that you observe on the printed circuit board.
Make sure you recognize each component on the PCB.
Identify as many components as you can, including a capacitor, transistor, IC CHIPS, resistor, fuse, inductor, diode, connectors, among other components.
TV PCB
Having knowledge of their names and classification can assist you to quicken the time required to identify them.
In Modern PCB, there is more use of IC chips than passive components, and all the IC chips appear similar (black encapsulation with different shape and size).
For this matter, it is crucial to scrutinize the number printed on the IC chip. Because, without the number, you will require more experience and brain power to decode the PCB.
Some manufacturers will develop mechanisms to delete the number on the chips as a way of hindering reverse engineering of their PCB.
Erasing the lettering reduces the chances of copying their circuit design.
The number is essential since it helps you search for the components’ datasheet from the internet.
The design of most current PCB uses surface mount components, which can be small making it difficult to apply the traditional color band scheme regarding a component such as a resistor.
Number coding similar to the color band scheme is applied for bigger SMD resistor. The first few digits stand for the actual digit as the last digit stands for the number of zeros.
Sample SMD Resistor
Smaller SMD resistors having smaller printed area apply a standard coded system to print their value.
The standard coding system is referred to as EIA marking code. The coding system makes it very difficult to establish the resistor value.
Fortunately, the internet has simplified the task since you only need to search and find the value base on the code.
There also exist apps which enable you to enter the EIA code, and in return gives you the resistance value.
The applications also have extra features which can help you in your PCB reverse engineering process.
ii.Gather and Extract Information on Related PCB Documents
Data acquisition is the next stage in reverse engineering PCB and to carry out a successful PCB reverse engineering, get at least two samples of the PCB.
Obtain a detailed scanned image of the populated PCB since this will help you establish the polarities and locations of the components.
Next, you collect detailed information about the component specifications and types.
Collect the technical manuals and information concerning the PCB assembly. Additionally, obtain usage and maintenance data and performance specifications.
Visually inspect the printed circuit board unit and take note of inconsistency between the available data and the real PCB.
After completing the process of data collection, remove the components from the board. Thereafter, using a thinner, clean the board to remove the solders. Finally, blow dry air to remove dirt and dust from the PCB.
iii.Analyze Important Signals
The analysis is the most tedious phase of PCB reverse engineering process.
The operation involves the mapping out how the components are interconnected.
You map out the entire connection (referred to as traces) component by component.
However, before commencing the tracing procedure, it is critical to identify the printed circuit board type which is categorized as a single layer, double layer, and multilayer board.Sample of PCB tracing
Single layer PCB is the simplest circuit board where one face of the board has only the PCB trace routing, while the other face consists of the electronic components.
Single layer board usually contains majorly through-hole components and it is fairly easy to map out the connection.
Double layer PCB is the second type of circuit board where the trace routing can be found on both faces of the board.
In most cases, you will find surface mount components on one face of the board while the through-hole components are placed on the other side.
Usually, traces routing is done beneath the through-hole components and the IC chips.
This type of traces routing makes it impractical to trace out the connection with the naked eye.
You will require a multimeter function continuity (also referred to as continuity tester) to identify a connection.
Typically, it will buzz the moment the probes get in contact with two points connected by a trace.
However, you can as well utilize an Ohm meter function which registers a zero ohm when you probe a connection.
I recommend the buzz since while you concentrate on tracing the circuit, you do not need to check the continuity tester display to confirm a connection.
The buzz sound signal is more convenient.
Even though continuity tester is a convenient device for tracing the connection, it is of essence understanding how it functions.
The buzz is made to sound at a specific ohm threshold.
This implies that a 10 Ohm resistor between two points may result in a buzz, which can mislead you into believing that there is a connection between the two points.
It is therefore important to be aware of this during the probing operation.
Combining the help of your vision and continuity tester should help reduce mistakes.
You should take note of components such as inductors, transformer, a sense resistor (normally bigger than the other types of resistor), coil, and any external wiring or connection to the PCB.
Another popular mistake is probing the trace without unplugging the power supply.
It is important to make sure that you switch off all connections to the printed circuit board before mapping out the connection.
Multilayer PCB is the most complex board to trace.
Commonly for a 4 layer circuit board, most developers prefer to use the middle layer for power traces such as GND and VCC.
Nonetheless, it is not always definite, but there are higher chances based on experience working with different printed circuit boards and common circuit theory.
PCB reverse engineering needs you to reason more like the designer of the circuit board you want to hack.
For a multilayer board, it is almost near impossible to trace the printed circuit board using your normal vision.
Ensure to match component pins connection for the entire circuit board, matching one pin at a time to the rest of the pins.
In some cases, knowledge of the components coupled with your experience as a designer might help you shorten the procedure.
There will be areas that you will instinctively know that it is not a must you try.
Draw out the position and the connection of the components, mark all the components, and designate the trace the moment you are in a position to establish its function.
Power supply traces are the easiest, to begin with.
This is so since we always know where the power supply is attached to the circuit board.
From there you can trace out where the power connection heads to next.
You will be capable of mapping out the next stage which is commonly the voltage regulator.
However, in the case of an AC power line, you will commonly locate a rectifier before it connects with the voltage regulator.
But this proposal presumes standard design thus it will be upon you to recognize it since there exist many varieties of PCB design.
PCB Reverse engineering design
Analysis of the datasheet of the IC chip can also assist you to establish the connection.
Order the component sign into the standard stamp circuit layout that you can identify.
With the configuration, you can easily recognize common standard circuit such as relay circuits, pull up, input circuit, voltage regulator, driver circuit using transistor, among others.
Draw them out in a layout that aids you to identify the circuit module functionality.
The process is complicated, and it is a never an ending conversation on PCB reverse engineering.
The more you reverse engineer PCB, the more you will master and advance your techniques, realizing new methods to decode and master the design of other circuits.
Automated PCB Reverse Engineering Process
Automated PCB reverse engineering automates the majority of the undertakings necessary during the procedure.
Automated reverse engineering of PCB has the ability to:
- Automatically detect components applying machine vision
- Collecting technical documents from the internet
- Scrutinizing the technical documentation to extract relevant information
1.Use PCB Reverse Engineering Software
Majority of PCB reverse engineering software come with features including:
- Schematic diagram drawing
- Multilayer circuit board design
- Drawing generation
- Digital circuit and analog circuit combination signal simulation
- Programmable logic semiconductor design, etc.
Generally, the software processes high-resolution pictures of either side of the printed circuit board.
Specifically, it automates the prerequisite first steps of components identification and the collection and scrutiny of information associated with those components.
2. Documents Analysis and Evaluation
High-resolution cameras are affordable and we normally take pictures for documentation purposes.
You begin by segmenting the images by identifying common visual features of microchips.
The segmentation generates areas of the chip packages.
You then pass down the areas to an Optical Character Recognition (OCR) library with the purpose of extracting the part number printed on the integrated circuit package.
You then match the OCR outcome against known manufacturer naming patterns and part numbers so as to minimize false positives.
Sample OCR
After establishing a valid part number, you search the internet for associated technical documents.
You can do the part number web search using ordinary search engines besides special search engines, which only index datasheets.
Download the matching documents and extract from them the basic data such as pinout diagrams, feature description, and pin signal tables.
Since technical documents normally come in PDF form, it is vital to convert them to XML so as to easily understand the documentation’s structure and appropriate pages.
The software filters out unlinked documents like marketing brochures based on the number of pages and matching keywords.
Also, the app then puts the results in a well-organized file system database or structure.
The processed data is displayed in a graphical user interface, enabling you to access all information faster.
After identifying critical components and analyzing technical documents, you then probe the actual connections between the components on the printed circuit board.
You achieve this utilizing a multi-meter and key them into the application.
For instance, you can add a serial connection joining two components by choosing both components and designating their connection utilizing the graphical user interface.
The database stores the connections and you can alter or annotate them at any given time.
This is particularly important for producing a visual report of all results and communicating the attackers’ perception to other concerned parties such as engineering teams or customers.
PCB Reverse Engineering Technique
PCB reverse engineering entails getting the internal structure and all layers connections by either non-destructive process or destructive process of delayering.
The non-destructive process involves imaging tomography, which you can apply to image the entire PCB without delayering.
On the other hand, the destructive process entails delayering, which you follow with imaging of each layer before you embark on the following round of material removal.
In either scenario, you can do the analysis manually or automatically whose outcome is a netlist that you can use to reproduce the PCB.
PCB reverse engineering technique
a)Non-destructive PCB Reverse Engineering Technique
The sector has expressed interest in switching to reverse engineering practices grounded in non-destructive techniques.
The industry shift is because of the method’s reduced costs, the shorter duration it takes to conduct PCB reverse engineering. And, the possibility of developing a test for detecting trust issues or faults.
The non-destructive nature of this technique of reverse engineering PCB gives more margins for error in the course of the operation.PCB Reverse engineering – Photo source: Semantic Scholar
Besides, you can put the PCB into other uses afterward.
Non-destructive PCB reverse engineering commonly uses X-ray tomography.
Tomography is a non-invasive imaging method which enables you to observe the interior structure of a substance without interfering with the under- and over-layer structures.
X-ray tomography enables you to extract the geometrical information of connections, via holes and traces on PCB layers.
Scanning PCB – Image source: SMTNet
The technique allows you to capture all the printed circuit board layers (front, interior, and back) in a single imaging session.
The concept of tomography is to obtain a pile of two dimensional (2D) images.
Then apply mathematical algorithms like center slice theory and direct Fourier transform and to regenerate the three dimensional (3D) image.
You collect the 2D projections from many varying angles based on the quality you require for the final image.
The PCB features such as material density and dimension are vital to factor in when selecting the tomography parameters which comprise of:
- Source power: relates to the amount of penetration and X-ray energy
- Detector objective: dictates the resolution range and the field of view
- Filtering: regulates the dose which permits higher energy X–rays to pass through
- The distance of the detector and source to the sample: has inverse proportionality to the number of counts
- Number of X-ray projections: determines the angular increment for every rotation for the sample in the process of tomography
- Exposure Time: linearly correlated to counts and establishes the total time and, ultimately, the cost of scanning.
These parameters can impact on the signal-to-noise ratio and pixel size, which you must optimize depending on the region-of-interest.
Analysis of the interior and exterior structure is possible after reconstructing the 3D image, which requires beam hardening and center shift tuning.
The pixel size is the most essential parameter for determining the quality of the regenerated 3D images.
Based on it, you can tune many other parameters including detector objective (same as optical magnification and distance of detector and source from the sample (the geometric magnification.
b)Destructive PCB Reverse Engineering Techniques
The printed circuit board might be single, double or multilayered depending on how complex the system.
In destructive reverse engineering of PCB, you first analyze the external layer of the board to identify the components mounted on it, its ports, and its traces.
Consequently, you then delayer the multilayered circuit board to expose the via, connectivity, and traces within its interior layers.
Reverse engineering PCB
Often, destructive PCB reverse engineering entails three procedures: solder mask removal, delayering, and imaging.
·Solder Mask Removal
The aim of this step is to take out the solder mask from the PCB and reveal the copper traces on the bottom and/or top layers with minimal destruction.
Even though it is at times possible to recognize the copper traces via the existing solder mask, extracting the solder mask will facilitate a more clear view.
You should carry out the procedure after detaching all the components from the PCB.
You can apply the following techniques to remove the solder mask on the printed circuit board:
- Sandpaper
- Abrasive blasting
- Fiberglass scratch brush
- Chemical
- Laser
·Delayering
The aim of this step is to access the internal copper layers of a multilayer PCB by means of physical, destructive delayering.
You should also carry out the process after removing all the components on the PCB. Below are some methods of PCB delayering you can apply:
- X-ray
- Sandpaper
- Dremel Tool
- Surface Grinding
- CNC Milling
·Imaging
The aim of this step is to get individual images of each layer of a multilayer PCB, employing non-destructive imaging methods.
Such techniques may be effective even against populated or fully assembled PCB.
You can complete imaging during PCB reverse engineering by using either X-ray (2D) or Computerized tomography (3D X-ray).
Requirements for PCB Reverse Engineering Services
Before you start the process of reverse engineering PCB, you should have the following:
1)Populated Printed Circuit Board or PCB without Components
A PCB is a laminated non-conductive material that links electronic components via conductive copper traces.
Figure 15 PCB populated with components – Image Source: USENIX
The traces connect electrically with the components and chips mounted on the circuit board.
Printed circuit boards are manufactured with thin copper foil conductive layers laminated to insulating non-conductive layers.
They make up the physical carrier for and offer the electrical route between electronic components.
By gaining access and imaging every copper layer of a PCB, it is practical for you to reverse engineer the whole PCB layout.
Conventional technology of PCB fabrication permits for mechanically-drilled holes diameters of 8mil and trace widths as low as 3mil.
Advanced processes allow for laser-drilled micro via diameters of 0.4mil, space and trace widths less than 1mil, passive electronic components implanted into the substrate, via-in-pad construction.
Copper thickness, described as the weight of copper per square foot, generally varies from 0.7mil to 5.6mil.
A PCB cross-section will in most cases offer hints to its design and complexity.
After fabrication of a PCB, its surface is covered with a solder mask (also referred to as solder resist).
The solder mask constitutes epoxy, dry film photo-imageable material, or liquid photoimageable ink (LPI).
The non-conductive solder resist layer provides protection to the PCB from oxidation and dust.
It also enables access to the copper zones on the board that should be exposed (like test points and component pads).
The most popularly employed solder mask color is green, even though there are several other colors available.
Darker colors cause difficulty in visual identification of traces.
To get harder contact surfaces and/or enhance solderability, a thin surface finish, comprised of lead-free or lead-based solder, palladium, silver, gold, or tin is applied to the exposed copper.
Lastly, the manufacturer prints a component legend (also called a silk-screen) onto the board using printable ink or epoxy.
This layer usually has the logos, identification symbols, part designators, and other manufacturing labels important for the printed circuit board testing/assembly and field service undertakings.
2)Scanned Picture of PCB
Scanning is the most widely applied technique for changing pictures into electronic layout, which yields raster image. In raster image format, you break down the picture into a matrix of pixels.
Electronic layout of PCB
During this step, you capture the authentic PCB by scanning it using a high-resolution scanner. Most scanners are able to produce images with superb color resolution.
Some can give images with a resolution of up 3200 x 6400 dot per inch (dpi) with a color depth of 48-bit for above 281 trillion possible colors.
Nonetheless, there are higher chances of experiencing problems as you capture the image.
The problem encompasses the reflection of light from the masks and copper tracks of the PCB. To reduce the problem, use a black colored paper having a hole at its center that is the same size as the circuit board.
When scanning, place the paper on the printed circuit board ensuring that it covers all the areas around it completely.
Applying this simple technique, you will be able to minimize the reflection of light which can compromise the quality of the scanned image.
Note that it is advisable to furnish a sample board when reverse engineering multilayer PCB.
3)Regenerate Gerber Files
Gerber data is a simple, generic method of conveying PCB information to a broad array of devices that transform the electronic PCB data to artwork created by photo-plotter.
Essentially, every CAD, PCB system produces X, Y coordinates augmented by commands that decide where the PCB image begins, the shape it will assume, and where it ends.
In conjunction with the coordinates, Gerber data comprises of aperture information, which dictates the shapes and sizes of holes, lines and other properties.
Versions of Gerber Files
Currently, there exist three versions of Gerber formats:
Figure 17 Garber file format sample – Image source: Wikimedia
- Gerber X2 – the newest Gerber format containing stackup data and attributes.
- RS-274-X – an improved version of Gerber format which has been in wide application.
- RS-274-D – the oldest version of Gerber format and RS-274-X is gradually replacing it.
Applications of PCB reverse engineering
Here are some of the situations where you can apply PCB Reverse engineering techniques:
- An obsolete device where the artwork is no longer in existence
- Device re-designed for WEEE/RoHS compliance
- Obsolete products lacking circuit diagrams
- Migration from Through-hole to SMD components
- Migration to emerging technologies while maintaining the logic and core features of existing systems.
- Design modifications
- To enhance functionalities, maintenance and support concerns on older printed circuit Boards
- For boosted performance.
- Lower life-cycle costs and reduced System Cost.
Frequently Asked Question on Reverse Engineering PCB
Do you have questions on reverse engineering PCB?
Well, here, I have sampled questions and answers that will give you an in-depth understanding on PCB reverse engineering.
PCB Assembly
1. What is Reverse Engineering?
Reverse engineering is a procedure where the aim is to reproduce, duplicate, or improve chips and systems relying on the analysis of an original device or system. For electronic systems, you can carry out reverse engineering (RE) at chip, board, and system levels. Because such electronics generally have multiple layers, reverse engineering entails getting the interior structure and connections of all layers by either non-destructive procedures or destructive process of delayering.
2.What is the difference between a schematic diagram and a PCB layout?
A schematic diagram is essentially a wiring diagram which details the components used and how they are interconnected. It is the plan.
The schematic diagram does not describe how this is attained in practice.
It does not, for instance, display the physical location of components on a PCB nor does it show how the routing of the numerous interconnects (i.e. PCB traces) between the components is achieved.
PCB Schematic – Image source: Stack Exchange
A schematic diagram just indicates “Pin A of component X is linked to pin B of component Y”. During the process of designing, you would create this first before proceeding to the PCB layout.
The PCB layout is the actual application of the schematic diagram. It details how to produce a printed circuit board that would if connected with parts, physically represent the circuit portrayed in the schematic.
It illustrates how big the board is, the construction of the PCB ( number of vias, layers, among other components), the location of all the components, and the routing of the numerous tracks connecting the parts.
Flex PCB Layout
However, PCB layout does not express any of the components’ values but only their pinouts and physical dimensions.
With the PCB layout, it is very easy to perform the PCB reverse engineering process.
Potentially, when you have the bill of materials and the PCB layout, you do not require the schematic since you can use one to reverse engineer the other though it will be a tedious task.
A schematic is much easier to read and you can draw it in an abstract way to make it simple to follow.
Therefore, when performing PCB reverse engineering, it would advise you have both.
The schematic will help you figure out what you are supposed to do and how you will connect the components.
On the other hand, you will use the layout as a map to locate the components/ signals of interest on the actual PCB.
3.Which one should I develop first, the PCB designs or Schematic?
Even though you can, in theory, begin with either the schematic or the PCB.
If you are the one designing the entire project then it is advisable to begin from the schematic. You can then utilize the schematic to create the contents of the PCB layout.
Though there is a PCB reverse engineering feature that will develop a ‘starting point’ schematic out of the PCB design.
The feature is usually meant for application when you have been furnished with a PCB design lacking the corresponding schematic, and you should develop the Schematic as ‘documentation’ for the PCB layout.
Any alterations to the ‘netlist’ (changing, adding, or removing nets, connections, or components) need to be carried out on the schematic.
You can back annotate only the component names from the PCB to the schematic.
4.How do I add my own values to components?
Components can have an infinite number of values, enabling you to improve the information kept with every component by adding aspects such as:
- Distributor
- Bin Number
- MTBF Value
- Tolerance
- Manufacturers Part Number
- Manufacturer, among other fields
When doing Component editing in the Library Manager, select the Edit menu and Values alternative to insert Values and their value series to the Component.
Do not forget to save the Component to Library after you are done with the editing.
Remember also to utilize the Update Component tab on the context menu for a chosen component in the design to reconfigure it after adding any new values to it.
Make sure perform this for both PCB designs and schematic.
When adding a new Component to the design, it will assume any Values added to the Library editor.
Check Component values for a Component by choosing it in the design and applying Properties option from the context menu.
Equally, you can add additional Component Values into a Parts list by employing the Report Builder feature found in the Output menu.
5.What is a netlist in PCB design?
A netlist comprises of a list of electronic components and the nodes they are linked to in the circuit.
A network (net) is an assembly of two or more interconnected parts.
The netlist consists of the circuitry between the components on the PCB, and it is normally held in textual form.
In PCB fabrication, you use the netlist to conduct electrical test (E-test) to locate missing or incorrect connections.
The complexity, representation, and structure of netlists can differ broadly, but the primary role of each netlist is to transmit connectivity information.
Netlists normally offer nothing more than nodes, instances, and maybe some features of the components used.
If they show more information than this, then they are normally taken to be a hardware description language.
You should always generate a netlist during PCB reverse engineering since it gives an extra level of authentication during the CAM review process.
It ensures that when you are finalizing the electrical test of the PCB, the operation will be correctly testing against the meant design.
6.What is the difference between PCB and PCBA?
A printed circuit board (PCB) is a board utilized to electrically link and mechanically underpin components using conductive tracks, pads, and various elements stamped from sheets of copper glazed onto non-conductive bases.
There exist several types of PCB including single layer, double layer or multilayer PCB.
Conversely, printed circuit board assembly (PCBA) is the board attained after solder paste printing on the PCB.
And, then mounting the numerous components such as integrated circuits (ICs), capacitors, resistors, and any other components such as transformers based on the application and required features of the circuit board.
A PCBA is normally subjected to reflow furnace heating to engineer a mechanical connection between the components and the PCB.
7.What is the difference between double layer PCB and Multilayer PCB?
·Single-layered PCBs
Single layered PCBs are the simplest PCB types. They consist of only a single conductive layer and this constricts their application to simple low-density designs.
Moreover, single-sided PCBs are low cost and are suitable for simple and high volume devices.
·Double layer PCB
Double–layered PCBs possibly are the most popular types of PCB.
This type of circuit board allows for traces routing about each other by joining between a bottom and top layer by means of vias.
The possibility to cross paths from bottom to top greatly boosts your flexibility in circuit designing, and this increases the circuit densities substantially.
Double-sided PCB is comparatively low cost, but only permits an intermediary level of circuit complexity. Reducing electromagnetic interference in this type of circuit board is difficult.
· Multilayer PCB
Multilayer PCBs enhances the density and complexity of the PCB designs by inserting extra layers beyond the bottom and top observed in a double layer formation.
With over 30 layers present in a multilayer PCB configuration, this type of PCB enables you to fabricate very dense and exceedingly complex designs.
Often, the additional layers in multilayer PCBs act as power planes which help in the supplying power to the circuit, and reduction of electromagnetic interference released by the designs.
You achieve lower levels of electromagnetic interference by putting signal levels between the power planes.
Also, you should know that if you increase power planes number in a PCB design, you will boost the thermal dissipation levels the PCB can offer.
This feature is essential in high power designs.
The entire layers in multilayer PCBs are almost usually committed to Power and Ground. Therefore, we group the layers as Power, Ground, or Signal planes.
At times there exists more than one of either Ground or Power planes, particularly when various components on the PCB need different supply voltages.
8.Who has the intellectual property rights for a PCB reverse engineered schematic?
If you reverse engineer a schematic from a PCB, then you are the developer of the schematic and thus the developer of that specific intellectual property.
Any patents which protect the final product or system are a different issue in totality.
Patent administration is between the patent holder and the manufacturer of the device, and it has no connection with the reverse engineered PCB.
Remember that patent claims should be made public, hence they are not meant to be a secret.
However, it is important I talk about PCB layouts and schematics extracted directly from service manuals.
Such kind of undertakings is considered an infringement on intellectual property because you will be directly copying another author’s work.
You should realize that some components of a PCB could be a company’s trade secret.
However, unless you are associated with the company developed the original circuit; you have no obligation to shield the firm’s secrets.
9. What is the importance of BOM during reverse engineering PCB?
The “Bill of Materials”, popularly known as the BOM, is basically a list.
In a PCB design, the BOM is a list of all the components you require to fabricate a printed circuit board.
You generate the PCB bill of materials from PCB design software.
To do this successfully, the CAD system must already have the part information needed to generate the BOM.
Each part always has its information kept in its distinct CAD library section.
As you instantiate each part in the design, its information is tagged along with it from the CAD library.
Once put in the PCB design, the part information is then accessible for utilization in the various elements of the bill of materials.
The elements inside of a BOM
There can be several kinds of information in a PCB bill of materials, although the BOM needs to possess a core group of elements, to begin with.
Let’s look at some of the most popular core elements that you will observe in a printed circuit board BOM:
- Comment: Every part types should have a distinct identification which is registered as a comment in the BOM. Usually, a company branded part number is applied as the comment, though this not a precondition. Vendor part numbers or other labels can be applied instead. For example, a company part number could be the comment “27-0477-03”.
- Description: This is a primary illustration of the part. In terms of the comment 27-0477-03 aforementioned, the description can be “CAP 10uF 20% 6.3V”.
- Designator: Every individual part on the PCB will possess its distinct reference designator. In relation to the 10uF capacitor, the designator could be “C27”.
- Footprint: This is the designation of the physical CAD footprint the part is using. For example, C27 could be utilizing a CAD footprint designated as “CAP-1206”.
In most cases, you organize the bill of materials by the value of the elements of the comment.
You would then include the other core elements related with the BOM on the same line.
For instance, let’s use the core element values from our above illustrations, and exemplify a small one-line BOM report:
Comment: 27-0477-03
Description: CAP 10uF 20% 6.3V
Designator: C19, C26, C27, C31, C46
Footprint: CAP-1206
Depending on your needs, the BOM can as well consist of extra elements of information.
These can comprise values and tolerances, or any other kind of information that is related to the component.
The only disadvantage is that the BOM report can become very long based on the number of elements you have chosen to include in it.
Advanced uses for a BOM
So far we have been discussing the basics of BOM. There exist some more advanced properties that we should equally mention.
You can as well organize PCB BOM by elements different from the comments, and you can also utilize them to show some more advanced design information.
Here are a few examples:
Alter the BOM format: You can alter how your BOM appears by arranging it differently. Essentially you will categorize the BOM by information of the comment, though you could rather organize it by footprint information.
Include parts not fitted: You have the choice to add components labeled as being un-stuffed in the BOM.
Generate BOMs for the various variety of the board: When you have developed different stuffing alternatives (fitted or not fitted) for components in different versions of the board, you are in a position to generate a different bill of materials for those different versions.
10. What the procedure of merging layers during PCB reverse engineering?
For a double layer board, you find the netlist of each layer independently. You then merge the netlists by locating the corresponding nets on either side of each drill. Here is how you should go about the merging procedure for each drill:
- Locate the top-layer net having the drill.
- Locate the equivalent drill on the bottom layer.
- Locate the bottom-layer net having that drill.
- Move the group of pads linked to the bottom-layer net to the list of connections of the top-layer net.
If you cannot find the equivalent bottom-side drill, assume the drill is a false detection and ignore it. After processing all the drills, unite the two netlists and the result is the complete netlist.
11. What is the main purpose of PCB vias?
The main role of any PCB via is to offer a conductive route for transmitting an electrical signal from one circuit layer to the other by way of a plated hole wall.
Nevertheless, there are various kinds of vias and various alternatives for the final vias appearance on the surface of the PCB.
Even though vias have basically similar roles, you should define each type correctly in your documentation to ensure that your assembly goes successfully and the PCBA functions efficiently.
There are three main types of vias which include:
· Through vias
This is a hole perforated all the way across from the top to the bottom layer of the PCB.
The hole is open at either end to facilitate the flow of plating solution across for the purposes of coating in order to make it conductive.
There are no shortcuts to drilling through vias. You have to observe the rules pertaining to adjacency (the least distance allowed between the margin of one via and the nearest via), minimum diameter, and maximum aspect ratio.
·Blind vias
This is a hole perforated from the bottom or top layer but halts at a given point before going the full distance across the PCB.
You can use a mechanically drilled blind via to link an external layer to an adjoining layer.
In some instances, you can use blind via to connect an external layer to another layer underneath though this requires careful planning so that you get a good result.
A blind via is open at one end only unlike the case in a through via.
Therefore, it is not possible for the plating solution to flow all the way across the hole. This makes the plating procedure complicated.
·Buried vias
You use this type of via to link interior layer structures only. First, you drill them as through holes from top to bottom of a glazed interior structure (like from L2-L7 of an 8-layer PCB), you then plate and fill in readiness for final lamination.
·Laser micro vias
This is the smallest type of via, typically about .003”-.004” in diameter.
The greatest advantage of micro vias is their capacity to fix onto very tight land areas, often as vias-in-pads inside tight pitch BGA or SMT footprints.
You planarize the pads back to their original smooth state after plating, reinstating the pad surface so that you can use it for component soldering.
12. How do I generate a netlist when reverse engineering PCB?
Once you have found the components and nets and you have determined the component pad locations, you can generate a netlist.
For every pad on each component, you locate the net having the center point of the pad, and then you add the pad and component to a list of connections on the net.
A pad being a connected copper region, every pad is part of precisely one net.
You can now print the netlist for a single layer board, and each netlist line assumes the form:
net_name: component1–pad1 component2 –pad2
You can apply numerous schematic capture tools to generate a netlist of the same form.
Although the component, pad, and net names are different, you should match the connectivity of this netlist to one generated from the correct board schematic.
In a double layer board scenario, you process the second layer in the same manner as the first one. You will then employ a merging procedure to generate the complete netlist.
13. Why is it important to generate the Gerber files?
Even though reconstructed 3D images comprise valuable information, you cannot use them directly for PCB elaborate quantified inspection or manufacturing.
You require a sequence of image processing stages to convert the picture to a CAD (computer-aided design) system file.
Transforming the images to CAD system file is a prerequisite for PCB fabrication.
Specifically, in order to print circuits on the board, you must generate Gerber files for every layer.
The files are 2 D binary card files having geometric information.
Image segmentation is the most crucial step for the transformation from a 3D X-ray to a Gerber file.
Image segmentation is the allocation of labels to every pixel (each voxel in the case of 3D) to extract point cloud (x, y, z) information.
A lot of research has been done to conduct an image processing on PCBs images for the purposes of PCB reverse engineering.
14. Can I reverse engineer any PCB?
The choice of a possible for the PCB reverse engineering depends on technical complexity, economics, and the amount of available data.
PCBs that have wide usage and high per-unit cost but comparatively minimal technical complexity are better options for the reverse engineering operation.
15. Does Computerized Tomography have limitations?
A minor demerit of computerized tomography is the field of view size of the X-ray system.
You will get fewer details or resolution on the obtained images with an increase in the field of view.
Therefore, you will need to balance between the quality of image and sufficient board visibility, which in most instances will not include the whole PCB area.
For you to process the entire PCB, you will need to create and stitch together multiple “segments”.
16.What makes Surface Mount Technology better than through-hole mounting?
· Through-Hole Technology
For years, fabricators applied through-hole technology in the manufacturing of almost all printed circuit boards.
This mounting technique entailed the utilization of leads to electrical components.
You would then insert the leads into holes drilled on the circuit board then solder them to pads located on the other side of the PCB.
Through-hole mounting is exceedingly reliable, as it offers a strong mechanical bond, nonetheless, the extra drilling makes the fabrication of boards substantially more costly.
In addition, the existence of holes in the PCB produce barriers in the context of the accessible areas of routing for signal traces on the layers.
They are immediately below the top layer on multiple layer PCB.
These two are some of the numerous reasons why surface mount technology got so popular in the 1980s.
Surface Mounted Technology
Alternatively to drilling holes, surface mount technology allows you to mount electrical components, or directly place them onto the PCB surface.
Generally, surface mount components are smaller than the through-hole ones.
This is because SMT components either got smaller leads or lack the leads completely.
Higher circuit densities are practical on a smaller PCB of a surface mount device because the components are more compact and it does not require several drilled holes.
This is particularly essential since modern electronics are becoming more sophisticated and compact.
In addition, surface mount technology is relatively economical than through-hole mounting.