First, the fault characteristICs of electronIC components
Although the number of electronic components of printed circuit board is large, but its failure is regular to follow.
1. Characteristics of resistance damage
Resistance is the most numerous component in electrical equipment, but it is not the component with the highest damage rate. Resistance damage is most common in open circuit, and resistance increases are rare and resistance decreases are rare. Common carbon film resistance, metal film resistance, wire wound resistance and safety resistance.
The first two kinds of resistance are the most widely used, the damage characteristics of one is low resistance value (below 100Ω) and high resistance value (above 100 kω) damage rate is high, the middle resistance value (such as hundreds of euros to tens of thousands of euros) rarely damage; Second, when the resistance of low value is damaged, it is often burnt black and easy to find, while when the resistance of high value is damaged, there are few traces.
Wire-wound resistance is generally used as a large current limiting, resistance value is not large. When cylindrical wire wound resistance is burned out, some will be blackened or surface blasting, cracks, and some have no trace. Cement resistance is a kind of wire wound resistance, it may break when burned out, otherwise there is no visible trace. When the resistors burn out, some surface will blow off a piece of skin, others will not have any trace, but will never burn black. According to the above characteristics, when checking the resistance can be focused on, quickly find out the damage of the resistance.
2. Characteristics of electrolytic capacitor damage
The amount of electrolytic capacitors in electrical equipment is large and the failure rate is high. Electrolytic capacitor damage has the following manifestations: one is the complete loss of capacity or capacity becomes SMAller; Second, slight or serious leakage; The third is the loss of capacity or capacity smaller and leakage. The methods to find the damaged electrolytic capacitor are:
(1) Look: some capacitors will leak when damaged, the surface of the circuit board below the capacitor or even the surface of the capacitor will have a layer of oil stains, this capacitor can never be used again; Some capacitance will bulge after damage, this capacitance can not continue to use;
(2) Touch: after the boot, some electrolytic capacitors with serious leakage will heat up, and even hot hands when touching with fingers. This capacitor must be replaced;
(3) There is electrolyte inside the electrolytic capacitor, long time baking will make the electrolyte dry, resulting in reduced capacitance, so it is important to check the capacitor near the heat sink of the printed circuit board and high-power components, the closer to it, the greater the possibility of damage.
3. Two, triode and other semiconductor device damage characteristics
Two, triode damage is generally PN junction breakdown or open circuit, which breakdown short circuit. In addition, there are two kinds of damage performance: one is the thermal stability deteriorates, the performance is normal when the boot, after a period of time, the occurrence of soft breakdown; The other is the PN junction characteristics change, measured by a multimeter R×1k, each PN junction is normal, but can not work normally after the machine, if measured by R×10 or R×1 low range file, it will be found that the PN junction positive resistance value is larger than the normal value.
Measurement two, triode can be measured with a pointer multimeter in the road, the more accurate method is: The multimeter is set to R×10 or R×1 file (generally with R×10 file, not obvious when using R×1 file) in the road test two, transistor PN junction positive, reverse resistance, if the positive resistance is not too large (relative normal value), the reverse resistance is large enough (relative positive value), indicating that the PN junction is normal, on the contrary, it is doubtful, need to be tested after welding. This is because the general circuit of the two, triode peripheral resistance mostly in hundreds, thousands of euros above, with a multimeter low resistance file in the road measurement, you can basically ignore the influence of the peripheral resistance on the PN junction resistance.
Second, what is the list of electronic components
The electronic component distribution list is a complete BOM given by the customer. The BOM contains multiple categories of electronic components, and then it is calLED the electronic component distribution list to help the customer complete the required material number in the list. According to the customer provided models and forms, the need for fast, reasonable, honest, honest for customers to solve the problem of too many varieties can not buy the original genuine products, high prices.
Therefore, electronic component ordering must provide professional, efficient and one-to-one electronic component ordering services to solve the most fundamental needs of customers, reduce production costs and improve effectiveness.
Third, notes for the use of electronic components allocation list
1. After the customer provides a BOM, carefully review the BOM and confirm the specifications. The speed of reply should be fast. We should confirm the specifications and models, check them carefully, and communicate with customers in time if we are not sure.
2. Quote to the customer. When quoting, be sure to ask whether the customer wants to issue invoice, confirm when the customer wants to buy, whether it is an inquiry or an order.
3. Discuss the terms of payment, cash on delivery, cash on delivery or monthly. Next, we need to follow up whether the customer has received the goods and the arrival situation. The whole process of electronic component ordering requires customers to experience professional, efficient, fast and high-quality service.In short, electronic components distribution order is to help customers professional, efficient, fast, high quality to solve the problem of multi-category PCB board electronic components procurement.