Table of Contents
An equipped PCB laboratory is essential to design, analyze, test a printed circuit board and assure its reliability in terms of adherence to standard requirements of the industries. PCB lab also tends to minimize wastes by detecting faults during initial stages of production.
So, how to build a professional PCB laboratory? And how does it work? Let’s get started with ELEPCB!
How to Build a Professional PCB Laboratory?
1 Construction Qualification Requirements
The Standard of PCB Lab
CNAS Accreditation
- The PCB laboratory needs to have CNAS (China National Accreditation Service for Conformity Assessment) accreditation qualification, including the laboratory in the technical ability, equipment management, quality of personnel and other aspects to meet the strict requirements.
ISO9001 Certification
- ISO9001 quality management system certification proves the standardization and effectiveness of the laboratory in quality management. This certification requires laboratories to establish a comprehensive quality management system, covering all aspects from experimental process design, equipment maintenance to personnel training.
Professional Qualifications
- PCB laboratory personnel need to have relevant professional knowledge and skills, and be able to skillfully operate testing equipment and tools.
Product Traceability System
- The establishment of a comprehensive product traceability system, which is particularly important for PCB laboratories, because PCB in electronic equipment in the key role, once the problem occurs, can quickly locate the source of raw materials, production processes, test links, in order to take effective corrective measures.
Equipment Qualification
- PCB laboratory equipment needs to comply with relevant standards and specifications, regular maintenance and calibration.
2 Functional Partitioning of PCB Lab
Production Equipment Placement Area
Centralized placement of large-scale equipment required for PCB production, such as high-precision printing machines, cutting and drilling equipment, etc. requires a special space for placement.
And the spacing between the equipment should be taken into account in order to facilitate operation, maintenance and heat dissipation.
Row Material Storage Area
All these must be stored according to specific safety and environmental needs, such as categorical storage of the chemicals, preventing mutual reactions while keeping adequate considerations for ventilation and fire prevention.
Manual Operation Area
Set up a manual operation area for those small, fine or needing to be manually operated links such as the initial installation of components, simple line connection and so on.
It needs adequate lighting and proper height of the workbench in order to ensure the comfort of the operator and the accuracy of the operation.
Chemical Experiment Area
Etching, plating and other chemical experimental operations, equipped with etching equipment, plating equipment, chemical analysis instruments, etc., storage of etching solution, plating solution and other chemical reagents, all with the appropriate safety and environmental protection facilities.
PCB Test Partition
In addition, there is a need for the above four production areas according to their respective functions of the board division, so that the layout of the PCB laboratory dynamic line is reasonable, in line with the logic of PCB production, especially PCB testing. Mainly divided into the following three boards:
- Electrical performance test area
- Reliability test area
- Functional Test Area
Microstructure Analysis Area
If PCB is found to have problems in the previous test process, or the microstructure of the PCB needs to be studied, the PCB will be sent to the microstructure analysis area.
Equipped with microscopes and other equipment to check the microscopic connection of the line, the quality of the solder joints and so on. This area requires a clean environment to avoid dust and other impurities affecting the observation results.
Failure Analysis Area
When the PCB fails, where fault troubleshooting and analysis.
Need to be equipped with a variety of fault diagnostic tools, such as logic analyzers, short-circuit testers, etc., and to facilitate the technicians to dismantle and inspect the faulty PCB.
3 PCB Laboratory Process
After reading the above functional partitions, our mind will have a rough image of the layout of the PCB laboratory.
Now, let’s run through the operation process of the PCB laboratory again. You can find the corresponding process according to the image just in your mind.
Step 1:
Raw Material Preparation
First, take out the required copper-clad boards, copper foils and other materials from the raw material storage area.
If chemical experiments are involved, chemical reagents are also taken out to place the appropriate basic materials on the workbench in the fabrication area, ready for subsequent processing. During the preparation of raw materials, check whether the specifications and models of the materials meet the design requirements.
Step 2:
Line Printing
Step 3:
Cutting and Drilling
Before printing, technicians carry out equipment debugging operations, such as adjusting the position of the printing head, pressure and other parameters, and then use high-precision printing machines to print the designed line patterns onto the copper-clad board.
According to design requirements, there are cutting and drilling equipment in the process line that cut or drill the printed circuit boards, and the debris from the aforementioned process falls directly into a collecting device for an easy cleaning thereof.
Step 4:
Chemical Experiment Operation
Step 5:
Manual Component Mounting
After printing, cutting and drilling, chemical experiments are performed.
After completing chemical experiments, small components are mounted manually in the manual operation area. When needed, PCBs are quickly transferred between the nearby fabrication equipment placement area and the chemical experiment area.
PCB Laboratory Analysis
I. Electrical Performance Analysis
Testing Continuity of Circuitry
The test probes make contact with the test points on a circuit board. A small voltage signal is thereafter passed through it to check whether there are intact circuit paths or not. In doing this, it becomes crucial for multi-layer PCBs, since any break or short in internal connections can be a problem.
II. Component Parameter Analysis
PCB Resistance Analysis
Resistance Measurement: The application of a multimeter or any other dedicated device to resistance measurement helps to disclose the resistance value of components in the PCBs.
1. PCB Resistance Range
- Normal discrete resistors have very wide resistance ranges, like carbon film resistors and metal film resistors. In ordinary electronic circuits, a few ohms to several MΩ could be normal. For example, the resistance takes about 100 Ω in the current-limiting circuit. While voltage-dividing circuit is used, the resistor should be some thousand ohms or even ten kΩ at least. In digital circuits pull-up resistors or pull-down resistors are generally in the range of 1 – 10 kOhm.
- In some power circuits, the resistor values depend on the power level. Such as a current-limiting resistor used in some high-power devices may be a fraction of an ohm whereas a bias resistor used for small-signal processing may be several megohms.
2. Pre-Processing Program for Resistance Anomaly
- When the value of the resistance measured is much less compared to the nominal value, then the resistor is probably shorted.
- This could be because of damage to the internal film layer of the resistor, such as destruction of the carbon film in a carbon film resistor, or an overvoltage or overcurrent shock in the circuit. In this case, if it is a discrete resistor, you can solder it off the board and again measure it to confirm whether it is really shorted. It can be directly replaced with a resistor of the same resistance value and a power specification only when it is confirmed to be short-circuited and is a common low-power resistor. The measure resistance is much larger when compared with nominal value. Resistor maybe has an open-circuit problem in such a situation, possibly due to resistor pin solder or internal fracture.
- The resistor should again be removed from the board for measurement to confirm that. If it is an open circuit, a normal resistor in a simple circuit will do for a direct replacement. If it’s on a multi-layer circuit board, which would be difficult to remove, this can be painstakingly removed with the help of a tool and replaced.
PCB Capacitance Analysis
Capacitance Measurement: Capacitance testers are the meters used for measuring values like capacitance.
1. PCB Capacitance Range
- Ceramic capacitors are available over a very wide range of capacitance values, from a few pF up to several microfarads. Very common ceramic capacitors that can be used within the range of 10-1000pF in high-frequency circuits for filtering, coupling, among other uses. 0.1-10μF ceramic capacitor can also work in some applications of low frequency decoupling.
- Electrolytic capacitors are available in large capacitances, a few microfarads upwards to several thousand microfarads. In power supply filtering circuits, common electrolytic capacitors may have a capacity of 100-10000 μF. Different application scenarios have requirements for the voltage withstand value of electrolytic capacitors. For example, the filtering electrolytic capacitors in the 5V power supply circuit only require a voltage withstand value of 10-16V, while those in the 220V mains rectifier filtering circuit must have a voltage withstand value of at least 400V.
2. Capacitance Anomaly of the Pretreatment Program
- If the actual capacitance measurement is far less than the nominal value, this may be due to either leakage or damage to the internal electrode in the capacitor.
- In the case of ceramic capacitors, it would be because of the effect of too much voltage or temperature. For electrolytic capacitors, leakage may be the result of dried-up electrolyte or damaged insulation inside the component. If so, the capacitor should be replaced. About electrolytic capacitors, polarity installation should be rightly considered.
- If the value measured is far larger compared to the nominal one, then the measurement error or internal short circuit of the capacitor probably occurred. If it is a measurement error, re-measure using a more precise capacitance tester. If an internal short circuit is determined, the replacement of both ceramic and electrolytic capacitors should be done with the same capacity and withstand voltage value.
PCB Inductance Analysis
Inductance Measurement: Inductive meters are utilized to find the inductive value.
1. PCB Inductance Range
- Small inductors, such as those in RF circuits, can be only a few nano-henries (nH) to several tens of microhenries (μH). For instance, in the RF circuit of a cell phone, the inductance used for matching networks can be 1-10nH; in some low frequency oscillation circuits, inductors of 1-100μH can be applied.
- Large inductors, used for filtering power supplies, may range from several hundred microhenries to a few henries. Power inductors within hundreds of microhenries could be used for filtering circuits in some switching power supplies, whereas in the case of low-frequency, high current filtering circuits, inductors may go up to a few henries.
2. Inductance Anomaly Pre-Processing Program
- If the measured value of inductance is far less than the nominal one, the coil of an inductor may be shorted, or its core may be damaged. In the case of a coil that is short-circuited, if a wire-wound inductor does exist, it might be that the insulating enamel protecting it got some scratches, which can lead to unexpected contact and hence a short circuit between a few turns. Depending on the case where the core might be damaged either due to extreme mechanical stress or high temperature, the inductor should be replaced.
- When the measured value of inductance is so much greater as compared to a nominal value; there might be a measurement mistake or an open circuit inside.
- If it’s a measurement error, the inductance can be remeasured by replacing it with an even more accurate inductor tester. For an open-circuit situation, involving a pin that had broken either on the inductor or inside the wire of the coil, the inductor has to be replaced.
III. Physical Property Analysis
Dimensional Precision Measurement
Calipers and micrometers are the best tools for measuring dimensions in the PCB, such as the outermost dimensions of the PCB and hole sizes including line widths of the circuits in it.
Physical Property Detection
Hardness Testing: A hardness-testing device measures the hardness of the PCB material. Hardness will determine the manner of treatment of the board during manufacturing and how it will be used without deforming.
Thickness Measurement: The overall thickness of the PCB and the thickness of each layer can be measured. Normally, the design and functionality determine the required thickness of a PCB for various types of electronic devices.
IV. Chemical Composition Analysis
Metal Component Analysis
Atomic absorption spectrometers or X-ray fluorescence spectrometers analyze metallic composition in the PCB material. These analyses will indicate how pure the metal is and what impurities it contains, as it can lead to malfunctions in conductivity and the performance of the PCB altogether.
Solder Material Composition Detection
Chemical methods such as titration or energy-dispersive spectroscopy are performed to identify the composition of solder materials. Inadequate composition of solder material leads to welding defects, primarily weaker joints or poor electrical contact.
V. Methods of Testing on PCB
Non-Destructive Testing
Visual Inspection
It usually starts with 5 to 10 times magnification by visual inspection with magnifiers, which is fast enough to scan the surface of a PCB for obvious defects. A microscope can also be used to make detailed checks at 100 to 1000 times magnification. Another one could be an automatic visual check that can rapidly and precisely complete the job, mainly for defects that are surface-based.
The next one is X-ray Detection. X-ray detection equipment sends X-rays through the PCB. This allows for looking at internal circuit connections, which is particularly valuable for multi-layer PCBs and for finding problems in components like BGA packages that cannot be seen from the surface.
In-Circuit Testing
The test signals are applied by ICT systems to the PCB while measuring the resultant responses.
Destructive Testing
Cross-section Analysis
First, one part of the PCB is cut into very thin slices. Further, these slices are prepared for microscopic examination. With such processing, internal structures such as layer structure and solder joint quality may be observed and help in identifying hidden defects.
Tensile Testing of Solder Joints
The solder joints are subjected to tension in a tensile testing machine until they fail. This can give some indication of the force which may break the joint; thus an indication of mechanical strength, important for assuring long-term reliability.
The Most Used PCB Lab Equipment
Inspection and Testing Instruments
The most elementary measurements of voltage, current, and resistance using multimeters give a very basic idea of circuit performance.
The signal waveforms could be observed and analyzed with the oscilloscopes; however, that is really crucial in diagnosis timing problems as well as for ensuring signal integrity.
Logic analyzers, while important for diagnosis digital circuit problems, help one to have deep insight into logical states and transitions in complex systems.
Such advanced tools in the form of an X-ray and AOI allow minute flaws to be detected accurately, such as solder voids, and misaligned components.
Also, the thermal imaging camera further complements the procedure by helping identify inefficiency or potential hotspot conditions by highlighting the heat diffusion through the entire PCB.
Environmental and Reliability Testing Tools
Environmental rooms exhibit extreme environments, including temperature, humidity, and corrosive environmental exposure. Salt spray testers assess corrosion resistance, whereas vibration tables examine durability in conditions of mechanical stress.
Burn-in racks accelerate aging to identify long-term performance characteristics.
Conclusion
PCB laboratory plays a very key role in manufacturing and innovation processes of electronic products. As complexity in electronic design increases, it is only here that controlled laboratory environments can test new materials for designs, check designs, and perfect manufacturing. They are more like quality hubs that ensure technical specifications and compliance with environmental conditions.
ELEPCB has professional testing experience and complete set of production line and laboratory configuration, you can check our service quality through the PCB fabrication page. Contact ELEPCB for further information or just get a quote!
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