What Is a PCB? A Comprehensive Guide to Printed Circuit Boards
A PCB (Printed Circuit Board) is the foundation of modern electronics, providing mechanical support
In the realm of PCB assembly and electronics design, resistors are fundamental components that regulate current flow and ensure circuit functionality. To quickly identify their resistance values and tolerances, manufacturers employ a standardized resistor color code system. This guide delves into understanding and interpreting resistor color codes, with a focus on commonly used values like 1k ohm and 1.2k ohm—knowledge crucial for OEM engineers and procurement teams to maintain circuit accuracy.
A resistor color code utilizes colored bands to convey three essential pieces of information:
1.Significant Digits: The first one or two digits of the resistance value.
2.Multiplier: The power of ten by which the significant digits are multiplied.
3.Tolerance: The permissible deviation from the specified resistance value.
The number of bands on a resistor (typically 4 or 5) indicates its precision:
4-band resistors: Standard resistors used in general applications with moderate precision.
5-band resistors: High-precision resistors used in applications requiring tight tolerance, such as medical devices and AI hardware.
| Color | Significant Digit | Multiplier (10ⁿ) | Tolerance |
|---|---|---|---|
| Black | 0 | 10⁰ (1) | — |
| Brown | 1 | 10¹ (10) | ±1% |
| Red | 2 | 10² (100) | ±2% |
| Orange | 3 | 10³ (1,000) | — |
| Yellow | 4 | 10⁴ (10,000) | — |
| Green | 5 | 10⁵ (100,000) | ±0.5% |
| Blue | 6 | 10⁶ (1,000,000) | ±0.25% |
| Violet | 7 | 10⁷ (10,000,000) | ±0.1% |
| Gray | 8 | — | ±0.05% |
| White | 9 | — | — |
| Gold | — | 10⁻¹ (0.1) | ±5% |
| Silver | — | 10⁻² (0.01) | ±10% |
4-band resistors are prevalent in PCB manufacturing. To decode their values:
1.Identify the first two bands: These represent the first two significant digits.
2.Locate the third band: This indicates the multiplier (10ⁿ).
3.Check the fourth band: This denotes the tolerance (e.g., gold = ±5%).
For a 1k ohm (1000 Ω) resistor with ±10% tolerance:
1st band: Brown (1)
2nd band: Black (0)
3rd band: Red (10² = 100)
4th band: Silver (±10%)
Calculation: (1 × 10) + (0 × 1) = 10; 10 × 100 = 1000 Ω (1k ohm).
5-band resistors offer higher precision by adding a third significant digit. To decode their values:
1.First three bands: Represent the first three significant digits.
2.Fourth band: Indicates the multiplier (10ⁿ).
3.Fifth band: Denotes the tolerance (e.g., brown = ±1%).
For a 1.2k ohm (1200 Ω) resistor with ±1% tolerance:
1st band: Brown (1)
2nd band: Red (2)
3rd band: Black (0)
4th band: Brown (10¹ = 10)
5th band: Brown (±1%)
Calculation: (1 × 100) + (2 × 10) + (0 × 1) = 120; 120 × 10 = 1200 Ω (1.2k ohm).
Determine direction: Tolerance bands (gold/silver) are usually at the end, or look for a wider gap between the last band and the others.
Use lighting: Poor lighting can distort color perception—use a magnifying glass if needed.
Verify with tools: For critical PCBA applications, cross-check with a multimeter to confirm values.
Q1: What does the silver band mean in resistor color code?
A1: Silver indicates a tolerance of ±10% in 4-band resistors and is never used as a significant digit.
Q2: How is a 1k ohm resistor different from a 1.2k ohm resistor in color code?
A2: A 4-band 1k ohm resistor uses brown-black-red-silver, while a 5-band 1.2k ohm resistor uses brown-red-black-brown-brown.
Q3: Why is resistor color code important for PCB assembly?
A3: Incorrect resistor values can cause circuit failures, overheating, or device malfunctions—critical in industries like medical electronics and AI hardware.
Mastering the resistor color code is essential for ensuring precision in PCB assembly. Whether decoding a 4-band 1k ohm resistor or a 5-band 1.2k ohm resistor, this guide equips engineers and procurement teams with the tools to verify component accuracy.
For reliable PCB assembly services that prioritize precision, contact HCJMPCBA today.
To learn more about PCBA services, contact Guangzhou Huachuang Precision Technology.
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