On all electrical appliances, there are positive and negative poles, and SMT peripheral equipment is no exception. We know that SMT peripheral equipment is used on PCB substrate production lines, limited to surface mount use. Therefore, it is crucial to distinguish its positive and negative poles. Let's take a look at how its positive and negative poles are divided?

The positive and negative poles of surface mount aluminum electrolytic capacitors are distinguished and measured. The black block marked on the capacitor is the negative pole. There are two semicircles at the capacitor position on the PCB, and the pin corresponding to the colored semicircle is the negative terminal. The length of the pins can also be used to distinguish between positive and negative poles, with the long pin being positive and the short pin being negative.

When we don't know the positive and negative poles of a capacitor, we can use a multimeter to measure it. The medium between the two poles of a capacitor is not an absolute insulator, and its resistance is not infinite, but a finite value, generally above 1000 megaohms. The resistance between the two poles of a capacitor is called insulation resistance or leakage resistance. Only when the positive terminal of the electrolytic capacitor is connected to the positive terminal of the power supply (black probe in resistance mode) and the negative terminal is connected to the negative terminal of the power supply (red probe in resistance mode), the leakage current of the electrolytic capacitor is small (leakage resistance is large). On the contrary, the leakage current of the electrolytic capacitor increases (leakage resistance decreases). In this way, we first assume that a certain pole is the "+" pole, and the multimeter uses R * 100 or R * 1K gear. Then, connect the assumed "+" pole to the black probe of the multimeter and the other electrode to the red probe of the multimeter. Record the scale at which the pointer stops (the resistance value is higher on the left side of the pointer), and for a digital multimeter, the reading can be directly read. Then discharge the capacitor (touch the two leads), and swap the two probes to measure again. In the two measurements, the black probe was connected to the positive terminal of the electrolytic capacitor when the needle stayed to the left (or had a high resistance). Additionally, there is a common type of tantalum capacitor with positive and negative regions, which is rectangular in shape and has a positive end marked with a "-" symbol;

There is also a silver surface mount capacitor, which is believed to be aluminum electrolysis. The top is circular and the bottom is square, which is very common on optical drive circuit boards. This type of capacitor has a negative end marked with a "-". LEDs: available in red, yellow, green, and blue colors, with brightness levels of generally bright, high bright, and super bright. Commonly used packaging forms include 0805, 1206, and 1210. LEDs: can be roughly divided into two types of packaging forms based on the current limit they can withstand. The low current type (such as 1N4148) is packaged in 1206, while the high current type (such as IN4007) does not have a specific packaging form and can only provide specific dimensions: 5.5 X 3 X 0.5. Capacitors: can be divided into two types: non-polar and polar. The non-polar capacitors are most commonly packaged in the following two types, namely 0805 and 0603; Polarized capacitors, also known as electrolytic capacitors, are commonly used. Aluminum electrolytic capacitors are commonly used, but due to their electrolyte being aluminum, their temperature stability and accuracy are not very high. On the other hand, surface mount components require high temperature stability because they are closely attached to the circuit board. Therefore, tantalum capacitors are the most common type of surface mount capacitors, which can be divided into four series: A, B, C, and D according to their voltage resistance.

The packaging of surface mount tantalum capacitors is divided into A type (3216), B type (3528), C type (6032), D type (7343), and E type (7845). The ones with oblique angles represent the positive electrode, while the ones with small triangles represent the positive electrode? I don't know! DIP switches, crystal oscillators, etc. can be found in different specifications of surface mount packages in the market, and their performance and price will be related to their pin coating, nominal frequency, and segment. You can judge from your feet that the long one is the positive pole and the short one is the negative pole The statement that there is half of the color coating on the capacitor refers to the material used for the negative electrode of the solid-state electrolysis or liquid capacitor. The advantage of using electrolyte as a cathode is that it can achieve a large capacitance. However, electrolytes are prone to volatilization and leakage in high-temperature environments, which greatly affects their lifespan and stability. Solid state capacitors use functional conductive polymers as dielectric materials, which will not cause plasma explosion when powered on for a long time without use. And it will not fail to achieve its expected characteristics and functions due to slow movement of electrolyte ions at low temperatures. Compared with liquid electrolytes, solid-state capacitors have superior characteristics such as environmental protection, low impedance, high and low temperature stability, high ripple resistance, and high reliability.