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PCB Test: the Complete Guide

In this blog post, you’ll read:In recent years, we have witnessed the rising popularity of PCB applications. PCBs are now used in many industries around the world, including the PCB testing industry. PCB testing involves verifying PCB design and PCB manufacturing processes to ensure a quality product. PCB Testing can be performed during all three phases of the PCB life cycle: Design verification; Manufacturing process control; In-circuit functional test.

Table of Contents

In recent years, we have witnessed the rising popularity of PCB applications. Do you know PCB is applied in different industries? Do you agree that PCB test is highly required before, in the process of and after the manufacturing?

Here is the complete guide on PCB test. Lets’s read it!

 

PCB Test

 

What is PCB Test?


 

PCB test is the process of functional verification and quality control that PCB circuits, PCB components, and PCB assemblies can function normally.

As a result, PCB test ensures that built PCB boards are safe to be used with other electronic components such as solid-state devices (transistors), vacuum tubes, LEDs, etc., in a variety of applications including consumer electronics (TVs, DVD players) automotive electronics (heating fans, air-conditioning systems), industrial electronics (machine controls).

Components or complete sub-assemblies are typically paid for before tests are performed on them. Therefore PCB testing also serves as an inspection technique to verify that these components satisfy certain standards or requirements during manufacturing.

PCB testing helps PCB companies to meet PCB quality requirements. PCB Testing may also involve PCB rework or PCB repair of defective PCBs, which involves the removal and/or replacement of components (such as reflow soldering), for example when printed circuit board assembly (PCBA) shows signs of overheating during operation.

 

Why PCB Test is Necessary?


 

Often after building a circuit, you have this unpleasant surprise of not seeing it work properly. Even after checking the mount, you don’t find anything wrong. However, there are many common defects that can occur which compromise the assembly of PCB. To avoid these faults, you can apply many (printed circuit board) PCB testing methods while manufacturing.  A PCB test is a specialized quality test that subjects the board to the most rigorous excellence tests. The goal is to have 100% certainty that each component, weld, plate, and connection made will support the demands to which it will be subjected.

PCB Test

 

Benefits and Advantages of PCB Test


Increased Safety

PCBs are not only used in smartphones, laptops, or small devices, but also are often used in security systems, electronic technologies, and other sensitive products. Failure of such products not only implies major damage in the performance of essential systems and organization’s services where they are installed but also creates great damage to the reputation of the manufacturer. Dangerous damages that may be caused by PCB failures are starting a fire, electric short circuits and even taking human lives. All can be avoided by performing essential PCB tests in every step of production.   

 

Bug Identification

One of the most difficult tasks while manufacturing PCB is finding the problem or bug and also the location of that bug.  PCB testing methods  help you in identifying, if there is any bug or issue and where it lies, in design, manufacturing, assembling, or the functionality of the devices so that they can be easily modified without causing any further damage.

 

Fewer Defective Products

PCB testing methods are necessary to avoid selling defective products. Companies make sure of meeting performance and efficiency standards by doing these tests for a better quality of the product. This leads to less return of products by customers, a better life span of items, less production, and maintenance cost. Other than these benefits, PCB tests ensure good public reviews and customer satisfaction due to improved quality.

 

Cost Reduction

Another fascinating benefit that you can get from PCB testing methods is less production cost. As you test the product in every phase of manufacturing and designing, the final product is defect free and you don’t need to go through the whole process again, which can be expensive and time taking. Additionally, maintenance cost is also saved due to careful PCB inspections on the products.

 

Time-Saving

If you are performing PCB testing methods at every step of production of PCBs, you are saving energy, cost, enhancing the quality, and also saving a big amount of time. I am saying this because tests along with designing, manufacturing, and assembling PCBs, reduce the risk of any bug in every process. However, if you test the device only at the final stage and unfortunately, deduct a defect then you have to go through the whole process again which is quite time-consuming.

 

What Parts should be Tested by PCB Test?


 

Most importantly, the best solution is selecting the right PCB test machine to accurately test PCB components, ensuring to meet the highest quality requirements. The following are some connection methods of components or parts you should pay attention to, as well as some effective tests.

  • Lamination: Lamination provides a better lifespan for your PCBs. If the quality of laminate is low and it can be peeled easily then it affects the functionality of the product. PCB lamination test includes checking the durability of lamination against peeling or heat. 
  • Electrical: Electrical conductivity test ensures the minimum leakage of current in working conditions. It is one of the most essential functionality tests
  • Copper plating: The next important thing which you should check in PCB is its copper foil plating as it is providing conductivity. The foil is laminated to the PCB board. The quality tests which are applied on copper plating are analyzing the strength and elongation of tensile in detail.
  • Hole wall: Hole wall quality ensures that when it is in use, it will not crack in changing temperatures or cycling environments. Hole wall tests mostly check the amount of thermal stress in which PCB can survive. This enhances the reliability of the product.
  • Solderability: It means how firmly components are attached to the PCB board. It affects the functionality of PCB. Tests related to solderability prevent faults in the final stage. There are many types of solderability tests but the most basic is wetting, which means resistance to liquid solder.  
  • Environment and cleanliness: Cleanliness for PCBs is the capability to survive different environmental conditions for example corrosion and humidity. PCB testing machines analyze the final product by passing through various environmental conditions like tests for water absorption.

 

PCB Test

 

Common PCB Defects


Misaligned Components

Defects of misaligned components are usually called shifts. It occurs in the soldering process. or it  occurs when the printed circuit board or component is not aligned correctly during the soldering process. Shifts can produce defects like shorts, open joints, and crossed signal lines.

 

Incomplete Solder Connections

Sometimes, connections of PCB do not get enough heat and can cause the incomplete formation of joints. The main reason can be bigger components jamming smaller parts of PCBs.

 

Excess Solder

If you use excess solder on a pin then the extra mass is what you’ll get which ultimately causes a solder bridge. This can give rise to many new small defects.

 

Wrong Orientation

Wrong orientation is an electrical defect and can be repaired by checking connections which give supply.  PCB in circuit tests are used to resolve this defect.

 

Missing Electrical Components

The missing electrical component is the same as missing another component. It also causes power failure. But the difference is that it fails the whole device.

 

Defective Components

Other than physical damages, defective components are one of the common PCB issues. It may result in power loss or inefficient operation.  You can repair it or replace it to make the device active again.

 

7 Most Popular PCB Test Methods during Manufacturing and Assembly


Visual Inspection

Visual control is a PCB testing method in which appearance has the properties of diagnostic control.

 

Advantages:

  • The most cost-effective test method
  • Deduct faults which cannot be deducted by electric control

 

Disadvantages:

  • A high probability of errors and omissions of defects
  • The inaccessibility of observing connections in the structures of multilevel PCBs

 

Applications:

  • Detecting base defects
  • loosening of conductors 
  • Ring cracks in holes and others

 

In-circuit testing (ICT)

PCB in circuit tests individual components on a board or portions of circuits. Methods of eliminating the influence of parallel circuits are applied. If you are checking a resistor, for example, it is its resistance that is measured, and not the resistance of the circuit to which it is connected. In-circuit testing is subdivided into analog and digital.

 

Advantages:

  • Versatile and inexpensive
  • Can be used in medium and large-scale production

 

Disadvantages:

  • Requires a lot of time and a high level of training 
  • Only used in one-off production and repairs

 

Applications:

  • The presence of short circuits and breaks
  • Discrete component ratings (resistors, capacitors, inductors, semiconductor devices)
  • presence and correct installation of microcircuits

 

X-Ray PCB Testing

X-ray inspection equipment (3D and 2D inspection equipment on the market now) mainly use X-rays to penetrate the PCB board, and then obtain images on a dedicated image sensor to realize the perspective projection of the circuit board, thereby intuitively judging from the image Whether the quality of the product is up to standard.

 

PCB Testing

 

Advantages:

  • It can quickly detect defective products
  • For layered or multilayer PCBs, only It takes only one inspection to complete double-sided and multi-panel defect inspection

 

Disadvantages:

  • Experienced and skilled labors are necessary
  • Time-taking
  • X ray PCB testing machine are costly

 

Applications:

X-Ray inspection equipment has a high product coverage rate and can simultaneously detect abnormalities that cannot be observed by other inspection methods, such as false soldering, false soldering, and missing soldering.

 

Flying Probe Testing (FPT)

A form of circuit inspection, flying probe, or flying needle detection is usually seen as an improvement through the ICT. As test points, a flying probe machine can also access its vias or component ends and can be programmed to check the value of passive parts, to directly check the orientation of the diode/transistor, and to perform voltage measurements.

Advantages:

  • Not Expensive and faster 
  • Fixture is not necessary
  • Better test analysis 
  • Save space on board

 

Disadvantages:

  • Too slow for large size of test 
  • Cannot deduct defects, like extra or deficient solder and voids

 

Applications:

  • Prototypes
  • small and medium group production
  • Boards with module density

 

X-ray PCB inspection: – PCB X-ray Inspection method is a non-destructive PCB test that uses low-level x-rays of PCBs to see inside PCB boards and PCB components. You can use it on both PCB as well as PCB assemblies.

 

Functional Testing (FCT)

Functional testing is intended to check the functionality of the PCB modules and, if necessary, adjust and configure it. Contact with the product is usually made through the edge connector. 

 

Advantages:

  • Minimizing the expensive cost as done in stimulate environment 
  • Can check the functionality from anywhere 
  • It improves the other test types like ICT and flying probe tests

 

Disadvantages:

  • It provides information only about PCB is working properly or not

 

Applications:

  • Supply voltage with the ability to change it in automatic mode
  • Supply of input signals in a wide range of frequencies and voltages
  • Measurement of parameters of output signals
  • Emulation of loads
  • Data exchange with the tested device
  • Measurement of results and their output to the display
  • Accumulation and processing of statistical information

 

Automated Optical Inspection(AOI)

It is a preliminary quality control that is used in any production. It takes place at various stages of PCB assembly. It checks places which are invisible to the eye or standard optical systems (magnifiers, microscopes, photo and video shooting, micro video and photo). In large serial production, it is more technologically advanced.

Advantages:

  • Automatically determine the presence of components in their places
  • Provide a test backlight zones

Disadvantages:

  • Doesn’t catch defects such as glue or seal defects
  • AOI does not discover new detects, it only detects defects that are preprogrammed

Applications:

  • Check the marking, polarity, read barcodes, 2D codes and other textual, graphic information on the board

 X-ray testing involves using controlled amounts of x-rays of the items being checked (PCBs or PCB assemblies) onto photographic film in an x-ray machine to capture images of the defects that were present at the time when the tests were carried out.

 

Burn-in Testing

The combustion test is very efficient and accurate, you can analyze the performance and also track secret defects before introducing the boards in the field. In the combustion test process, the plates are installed to check to detect early faults and test the load capacity, thus eliminating premature faults.

 

Advantages:

  • Checks real time performance
  • Increase reliability

 

Disadvantages:

  • Can reduce the lifespan
  • Reduces overall production
  • Time taking

 

Applications:

  • Apply where failure is not bearable, e.g. security or military equipment
  • Or in extreme environments

 

 

X-Ray PCB Test Equipment for Sale


 

As PCB are made of various electrical parts, it is important to test the PCB with any faults or errors without destruction. Here comes the most effective testing method: PCB X-Ray testing. We, UNI X-Ray, provide the most advanced and quality PCB X-Ray machine for customers like you all over the world.