BGA Features
BGA Features :
1 pin is more spherical, and the ceramic BGA has a cylindrical shape; 2 pin spacing is 1.0mm, 1.27mm, 1.5 mm, pin number is 169 ~ 480 feet ( Figure 2-2-14 ); 3 pin count up to 800 feet; 4CSP predecessor; 5 higher than QFP assembly density; 6. Thin; 7 Good electrical performance; 8 pins are stronger; 9 solder joints are not visible; 1 rework equipment and process demand is relatively high; 1 process specification is very difficult; the reliability is not as good as the pin element.
5. Crystal oscillator is a kind of electronic components that generate fixed frequency through a certain voltage excitation, which is widely used in household appliances and computers ( Figure 2-2-18 ) . Types are divided into : passive crystal, active crystal. The 135C961 Passive Crystal Oscillator generally has only two pins; 2 active crystal oscillator is generally Figure 2-2-18 crystal four pins, and in the plug on the corresponding foot position has strict requirements, if the plug in the opposite direction will be crystal loss bad. ( at the same time, the diaphragm of the SMD crystal is very thin, take it gently when you take it ). The identification of the crystal oscillator on the PCB is shown in Figure 2-2-19.
Basic function of resistance
1 : limit the current in the circuit. Unit and symbol : ohm ( 2 ). 3 on the PCB code : R. 4 categories : PTH resistance; sMD resistor. 5 conversion formula : 1MQ = 1000kQ; 1 kQ = 1000 yuan. 6 Spray code read : the first two valid figures; the number of zeros in the third place ( Figure 2-2, one 20 )
2. The capacitance of the capacitor is shown in Figure 2-2-21, and the capacitor has the following characteristics. 1 Basic function : storage charge, DC blocking, and communication. 2 Units and Symbols : Farah ( F ). 3 on the PCB code : C. 4 categories : PTH capacitor and SMD capacitor. 5 conversion formula : 1F = 1000mF; 1 mF = 1000F; 1 F = 1000 nF; 1nF = 1000pF.6 DC operating voltage : 6.3V, 10V, 25V, 50V, 63V, 100V, 200V.
Slsl usually has no aging characteristics and is the most stable capacitor. The most common is COG ( NPO ).
Clas2 has a large capacitance and temperature stability. The most common ones are X7R and Y5V. Difference : the temperature range of X7R is between 55 and 125C, which provides a medium capacity of only 15 % variation. The temperature range of Y5V is between 30 and 85C, and the capacitance change is 2 % ~ 82 %, and the maximum capacitance can be provided.
3. The inductance is shown in Figure 2-22 as the difference between the inductor and the magnetic bead. 1 basic functions : the magnetic field in the storage circuit, resistance to AC, DC. 2 Units and Symbols; henry ( H ). 3 on the PCB code : L. 4 categories : PTH inductors and SMD inductors. 5 Conversion formula : 1H = 1000mH; 1 mH = 1000 uH.
