Chip Resistors or Chip Fixed SMD Resistors, are metal glass glaze resistors. SMD resistors are made by mixing metal powder and glass glaze powder and printing them on the substrate by screen printing. Chip resistors resist humidity and high temperature and have a small temperature coefficient, which can significantly save circuit space costs and realize refined circuit design.
Types of Chip Resistors
Commonly used chip resistors are divided into the following categories: General Thick Film Chip Resistor, High Precision Thick Film Chip Resistor, GeneralThin Film Chip Resistor, Low Resistance Alloy Chip Resistor, chip exclusion, Current Sense Chip Resistor/Shunt Chip Resistor, Anti-surge Resistor, Automotive Resistor, etc.
Characteristics of Chip Resistors
1 Miniature and lightweight
2 Suit for reflow and wave flow solder
3 Stable electrical capability, high reliability
4 Low assembly cost, suit for automatic SMT equipment
5 Superior mechanical and frequency characteristics
6 Compliant with RoHS directive, Halogen-free requirement
Main Parameters of Chip Resistors
Chip Resistor Size and Package
Commonly used resistor packages are 01005, 0201, 0402, 0603, 0805, 1206, 1210, 1812, 2010, and 2512.
The package and dimension table is as follows,
| British (in) | Metric(mm) | L (mm) | W (mm) | t(mm) | a(mm) | b(mm) |
| 01005 | 0402 | 0.40±0.05 | 0.20±0.05 | 0.13±0.05 | 0.10±0.05 | 0.10±0.05 |
| 0201 | 0603 | 0.60±0.05 | 0.30±0.05 | 0.23±0.05 | 0.10±0.05 | 0.15±0.05 |
| 0402 | 1005 | 1.00±0.10 | 0.50±0.10 | 0.30±0.10 | 0.20±0.10 | 0.25±0.10 |
| 0603 | 1608 | 1.60±0.15 | 0.80±0.15 | 0.40±0.10 | 0.30±0.20 | 0.30±0.20 |
| 0805 | 2012 | 2.00±0.20 | 1.25±0.15 | 0.50±0.10 | 0.40±0.20 | 0.40±0.20 |
| 1206 | 3216 | 3.20±0.20 | 1.60±0.15 | 0.55±0.10 | 0.50±0.20 | 0.50±0.20 |
| 1210 | 3225 | 3.20±0.20 | 2.50±0.20 | 0.55±0.10 | 0.50±0.20 | 0.50±0.20 |
| 1812 | 4832 | 4.50±0.20 | 3.20±0.20 | 0.55±0.10 | 0.50±0.20 | 0.50±0.20 |
| 2010 | 5025 | 5.00±0.20 | 2.50±0.20 | 0.55±0.10 | 0.60±0.20 | 0.60±0.20 |
| 2512 | 6432 | 6.40±0.20 | 3.20±0.20 | 0.55±0.10 | 0.60±0.20 | 0.60±0.20 |
Resistance value, silkscreen, and its marking rules
The production process of chip resistors adopts laser trimming, and the resistance film is a highly durable glass glaze material, so the precision of the chip resistor is relatively high. The chip resistor of the ordinary resistance series adopts the E24 series, that is, the deviation of ±5%. The precision chip resistors use the E96 resistance series (± 1% deviation).
The figure below shows conventional thick film chip resistors’ resistance value, silkscreen, and marking rules.
SMD resistor accuracy
chip resistors are generally expressed in letters:
T: ±0.01%
A: ±0.05%
B: ±0.1%
D: ±0.5%
F: ±1%
J: ±5%
K: ±10%
The most commonly used accuracy is the J file ( 5% ) and F file ( 1% ).
Chip Resistor Rating
the chip resistor refers to the maximum power consumption allowed when the durability test is carried out at an ambient temperature of 70℃and the tissue change does not exceed the allowable value of the test. The package mainly determines the rated power of the chip resistor and is also related to the resistor’s process, brand, and resistance value. If the temperature exceeds 70℃, its rated power will drop.
At the same time, we can continuously apply DC or AC voltage across the chip resistor, and the limit voltage depends on the size and manufacturing process of the resistor. The rated value of the chip resistor is shown in the figure below:
Resistance(TCR):
The temperature coefficient of resistance (TCR) indicates the relative change of the resistance value when the temperature changes by 1 degree Celsius. The unit is ppm/℃, and ppm (part per million) is a few parts per million.
Temperature Coefficient = (R-Ra)/Ra ÷(T-Ta) × 1000000
Ra: resistance value under a reference temperature condition
Ta: base temperature 20℃
R: resistance value at any temperature
T: any temperature
The range of commonly used temperature coefficient of resistance is: -200~500ppm/ ℃
Selection principles of chip resistors
As a miniature component, the chip resistor can significantly reduce the size of the PCB and the distance between circuit boards. When designing the circuit, you can make full use of the double-sided PCB to reduce the size of the whole machine, which is also conducive to automated production and assembly.
When choosing the chip resistor, you should pay attention to the following points:
1 You need to pay attention to the resistance value series of chip resistors. The most commonly used ones are E24 and E96 series. To select the resistance value, choose a nominal value close to the calculated value.
2 The power of the chip resistor is generally relatively small. If necessary, you must leave a margin when selecting the power and design for power reduction.
3 The size and power of some chip resistors are compatible. For example, 0603 can achieve 1/10W in some resistance ranges. In this case, you must refer to the manufacturer’s specifications and related technical information.
4 Because the size of the chip resistor is exact when designing the PCB pad, you need to pay attention to whether the tolerance of the pad size is appropriate.
5 Chip resistors are generally assembled by an automatic chip mounter. In some cases, pay attention to adjusting the temperature of the soldering iron during manual soldering;
6 Essentially, the 0Ωresistor is equivalent to a jumper wire, widely used in SMT design, and can bring much convenience.
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