When designing precision electronics or performing detailed analysis of worst-case scenarios, we need to consider parameters that may not be important in other applications. One of them is the consideration of the tolerance of the resistor. In fact, no matter whether the resistance value of the resistor you use is large or small, tolerance must exist. But it does not limit the maximum and minimum values of resistance in your circuit.Today qihe smt pick and place machine sharing resistance issues to consider in PCB circuit design .
Tolerance: Defines the range of differences between a resistor’s actual resistance and its nominal resistance at the time of manufacture. A resistor with a nominal value of 1000Ω and a tolerance of ±5% has a value in the range of 950Ω to 1050Ω. We want this value to be fixed and not change over time. But this is not the case. Engineers must consider tolerances in the design and ensure that the designed circuit works within the operating time limit.
Temperature coefficient: This coefficient describes the phenomenon that the resistance of the resistor changes with the change of temperature. Its unit is ppm/K (i.e. 10^-6/K); of course, the same is true if K is replaced by °C as the unit; usually The temperature coefficient values are 5, 10, 20, and 100. For example, there is a 1000Ω resistor with a temperature coefficient of 100ppm/K. When it experiences a temperature change of ±60K (assuming the initial temperature is 300K and the change range is 240-360K), its resistance value will change by ±6Ω. Of course, the smaller the temperature coefficient of the resistor, the higher the price.
Calculation of resistance change and temperature change
The resistor heats itself: For high-precision circuits, sometimes the power consumption of the resistor must also be considered. Resistors have specific thermal resistance, whose unit is °C/W. Engineers should be aware of power losses within a resistor; this will cause the resistor’s temperature to rise and ultimately affect the resistor’s resistance.
When determining the maximum and minimum values for the resistors you use, you must consider tolerances, temperature coefficients, and the effects of resistor self-heating. When conducting analysis, you may notice that some parameters can be ignored or not considered accurately, but you must first have a certain understanding of them before you can determine whether they are important.
For some precision circuits (such as gain stages in amplifiers), it is necessary to match the resistors and ensure that their resistances are within the required range and have the same temperature coefficient.
On some circuits, it is also critical to ensure that certain key resistors are positioned so that the temperature is the same on both ends of the resistor. Otherwise, the Seebeck effect also needs to be considered. When using forced air flow, it is necessary to ensure that the resistor is perpendicular to the air flow so that heat from one end is not transferred to the other end and the temperature of the component is equalized.Read more: Resistance issues to consider in PCB circuit design
Best seller SMT Machine ：Qihe smt line products
Q6 SMT pick and place machine 6heads 50slots With PCB Rail Servo Pick&Place Machine
Q4 SMT pick and place machine 4heads 50slots With PCB Rail Servo Pick&Place Machine
TVM802B Plus SMT pick and place machine 2heads 58slots desktop pick&place deluxe edition
QM10 SMT pick and place machine 10heads 80slots Fully Automatic Chip mounter SMT Assembly
TVM802BX SMT pick and place machine 2heads 46slots desktop pnp mounter deluxe edition
QL41 SMT pick and place machine 4heads 8slots LED for 1.2meters led strip pick&place machine
QM81 SMT pick and place machine 8heads 80slots Fully Automatic Chip mounter SMT Assembly
TVM802AX SMT pick and place machine 2heads 29slots desktop deluxe edition SMT Pick&Place Machine
QM61 SMT pick and place machine 6heads 63slots Fully Automatic Pick&place machine SMT Assembly chip mounter
What is SMT in engineering?
Surface mount technology is a part of the electronic assembly that deals with the mounting of electronic components to the surface of a PCB. Electronic components mounted this way are called surface-mounted devices (SMD). SMT was developed to minimize manufacturing costs while making efficient use of board space.Qihe SMT company develops and produces all kinds of SMT equipment suitable for world wide market, including pnp machine,reflow oven,stencil printer,pcb handling machines,and other products.
Small desktop pick and place machine TVM802A,TVM802B,TVM802AX,TVM802BX series suitable for beginners, for hobbiest or low vol usag.
Advanced level 4-head LED strip placement QL41 led machines and with rail universal series Q4,TVM925S,TVM926S,pick and place
Fully automatic 6-10-head placement pick and place machine QM61,QM62,QM81,QM10,machines, which are suitable for high volume mass production in factories.
What is SMT in programming?
Offline Automated Programming vs Inline SMT Programming
Qihe pick and place machine can be programmed directly on the SMT equipment .
Or Coordinates can also be imported csv file through programming software.
Currently supported software such as protel,DXP,Altium Designer,Pads,Candes,proteus,DXP.
Inline SMT programming is a solution to consider for narrow segments of device programming requiring short programming times, with medium to high volume, for just one device type smt pick and place.
WHAT IS SMT pick and place machine？
SMT (Surface Mounted Technology) is a comprehensive system engineering technology, which covers substrates, design, equipment, components, assembly processes, production accessories and management. When it comes to SMT pick and place machines, the automatic SMT production line requires automatic loading and unloading machine, automatic solder paste printing machine, placement machine, reflow soldering machine, AOI inspection equipment, conveyor,connecting table, etc. For these SMT assembly line equipment, Qihe SMT can offer you machines in prototype SMT line, small SMT production line, mass production SMT line at low SMT line cost. Contact us now if you are interested.smt pick and place
WHAT IS SMT ASSEMBLY LINE？
With the development of technology, future electronic products will be lighter, smaller and thinner. Traditional assembly technology can no longer meet the requirements of high-precision and high-density assembly. A new type of PCB assembly technology-SMT (Surface Mount Technology) has emerged. SMT Assembly is the use of automated machines to assemble electronic components on the surface of the circuit board. Its density, high speed, standardization and other characteristics occupies an absolute advantage in the field of circuit assembly technology. In addition, SMT assembly has a wide range of uses.