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The role of QC in PCBA processing
Quality is the sum of various element attributes that meet customer needs. In the PCBA process, quality is an important factor that affects the reputation and reputation of a company, and affects whether customers are willing to continue cooperation. Reflects the sum of the characteristics and characteristics of the entity that meets the user's explicit or implicit needs.
The quality requirements in the PCBA process can generally be divided into six categories:
A Performance requirements: physical characteristics, functional inspection, materials and their life cycle;
B. Applicability requirements: customer needs and the applicability of PCBA board functions;
C Reliability requirements: the reliability of PCBA board products;
D Safety requirements: customer use must be reliable and timely, and can not cause injury or accident to the user;
E Economic requirements: applicability, customer's affordability requirements;
F Appearance and aesthetic requirements: the psychological feeling and aesthetic value of customers, the PCBA board should be neat and beautiful.
Production process inspection (IPQC): generally refers to the quality control of the production activities at each stage after the material is placed in the warehouse to before the finished product is placed in the warehouse, that is, Inprocess Quality Control. Compared with the quality inspection at this stage, it is called FQC (Final Quality Control).
The purpose of process inspection is:
A. Before mass production, detect defects in time and take measures,
Can prevent a large number of defective products from occurring
B. In view of the non-opportunistic changes in quality, check during the operation to prevent the occurrence of defective products (process inspection not only inspects the product, but also verifies the main process elements that affect product quality (such as 5MIE). In fact, in In the process of normal production of mature products, any quality problems can be attributed to the variation of one or more elements in 5M1E)
C. Through the implementation of the inspection, the defective products of this process are not allowed to flow into the next process, and the unqualified products are prevented from flowing into the next process to continue processing.
In the PCBA process, QC is very important, and it plays a vital role in the yield of materials and electronic components and finished products. Sometimes we may complain that there are so many QC inspection steps in the processing process, which is troublesome and waste time, and want to omit various procedures, but these are not allowed. Only when we strictly implement each step in the production, can we deliver to the customer. Satisfactory finished product.
The difference and use of chip capacitors and electrolytic capacitors
The chip capacitor is a kind of capacitor that is widely used in SMT chip processing, and people often wonder what is the difference between the chip capacitor and another well-known electrolytic capacitor. Let me answer it for you next.
1. The difference between chip capacitors and electrolytic capacitors
1. The full name of SMD capacitors is multilayer chip ceramic capacitors, which is the general name for most capacitors that can be packaged by SMD, while electrolytic capacitors are a type of capacitance classification.
2. SMD capacitors are divided into non-polar capacitors and polar capacitors. Polar capacitors are generally called electrolytic capacitors. However, some electrolytic capacitors are not suitable for SMD packaging, such as aluminum electrolytic capacitors for energy-saving lamps.
3. SMD capacitors are generally small in size, small in capacity, and relatively high in accuracy, while electrolytic capacitors are relatively large in volume and capacity, and there are many types.
SMD is a processing method in the PCBA processing industry. It refers to the process of applying solder paste or red glue to the components, then mounting them through the placement machine, and then performing reflow soldering. Generally, the volume of the chip capacitor is smaller than that of the plug-in, and it is more suitable for the development of the times.
2. Purpose
1. The chip capacitor has a considerable effect in the middle and high frequency, its small size, high withstand voltage, and very low ESR of the high frequency resonance point (several mΩ), usually used for filtering in the middle and high frequency (100k-hundreds of M). It is best to use each resonant frequency band, such as 102, 103, 104 (ie 1nF, 10nF, 100nF) ceramic capacitors in parallel. In order to filter the low and intermediate frequencies, the electrolytic capacitor must be considered first. It should be noted that most electrolytic capacitors have polarity, that is, the positive and negative poles must not be reversed. Even if the polarity is accidentally reversed when measuring with an ordinary multimeter, the capacitor must be discarded.
2. The disadvantage of ceramic capacitors is that their performance changes greatly with temperature changes (except for type I media, but the capacity of type I media is not large), such as X7R, X5R within the rated temperature range, the content changes ±15%, as for Z5U, Y5V media The capacity change can reach -82%. Electrolytic capacitors usually have good temperature characteristics (except for liquid aluminum electrolysis, but solid aluminum electrolysis has greatly improved in this respect, but the withstand voltage is rarely more than 100V at present), wide frequency range, DC bias Excellent characteristics, stable equivalent series resistance (ESR), and high ripple current resistance.
3. Ceramic capacitors will change in capacity with the DC bias applied to it. At the same time, ESR also has severe jitter in the rated frequency range. In this regard, ceramic capacitors, tantalum capacitors and solid aluminum electrolysis are incomparable. . Electrolytic capacitors (it should be noted that as long as the capacitors that use electrolyte as the cathode are electrolytic capacitors, the most widely used ones are aluminum electrolysis, tantalum electrolysis, niobium electrolysis, and super capacitors, etc.) have a huge capacity, even farad, With a capacity of the order of hundreds to thousands of farads, it is very suitable for energy storage.
In a circuit composed of a circuit board, it is often necessary to consider the factors of price and performance. Different types of capacitors have different performance advantages. It is best to choose the capacitors of the patch or plug-in that are suitable for you.
