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Advantages of reverse-mount low-ohmic resistors(r_what13)
Current Sense Resistor
＜Advantages of Reverse-Mount Low-Ohmic Resistors＞
What is the Current Trend With Low-Ohmic Resistors?
Besides exhibiting the correct resistance value, Current Sense Resistors (Low-Ohmic Resistors) that are compact but support high power and feature superior heat dissipation are increasingly required. To provide greater power handling capability and improved heat dissipation characteristics, products with larger chip sizes and units configured with wider electrodes are typically used.
Larger size → Increased power
Wide terminal type → Improved heat dissipation
However, increasing the chip size will require a larger mounting area, decreasing strength against temperature cycling.
Maintaining or Improving Power Handling Capability While Decreasing Chip Size
Wide terminal types can fit the need for higher rated power in a compact form factor. However, although increasing the width of the terminal improves heat dissipation and rated power, one drawback is higher costs due to increased electrode material compared with conventional products.
| Advantages | Disadvantages | |
|---|---|---|
| Conventional High Power Type |
|
|
| Wide Terminal Type |
|
|
To that point, as shown below, ROHM's UCR series provides an ideal balance between material costs and specifications.
Why Does the UCR Series Feature Higher Rated Power Than Conventional Types?
The UCR Series adopts a rear-mount configuration. This shortens the distance between the substrate and heat-generating elements, improving heat dissipation performance. In addition, materials and structure are optimized, ensuring higher rated power over conventional resistors and contributing to greater end-product miniaturization.
Rated Power Comparison
| Size (mm) | Top Mount Type (Conventional MCR Series) | Rear Mount Type (UCR Series) | Wide Terminal Type (LTR Series) |
|---|---|---|---|
| 0603 | 0.05W | 0.1W | - |
| 1005 | 0.063W | 0.125W | - |
| 1608 | 0.1W | 0.25W (Partial 0.2W) | - |
| 2012 | 0.25W | 0.33W | 0.5W |
| 3216 | 0.25W | 0.5W | 1W |
Adopting a rear-mount structure also minimizes the effects of additional resistance components from the top and sides of the electrodes, reducing resistance changes due to temperature (TCR).
Resistance Change Rate Comparison
Temperature Characteristics Comparison
| Parameter | Top Mount Type(MCR10) | Rear Mount Type(UCR10) |
|---|---|---|
| Temperature Characteristics (ppm/℃) | 500±300 | 0 to 250 |
Key Features
UCR Series (Rear-Mount Type):
- Compact, high-power design
- Superior temperature characteristics vs conventional top mount types
- Lower material costs compared with wide terminal types
Lineup
| Part No. | Size (mm) | Rated Power (at 70℃) | Resistance Tolerance | Temperature Coefficient of Resistance (ppm/℃) | Resistance Range | Operating Temperature Range (℃) | Automotive Grade (AEC-Q200) |
|---|---|---|---|---|---|---|---|
| UCR006NEW | 0603 | 1/10W (0.1W) | J (±5%) | 0 to 300 | 100mΩ to 910mΩ (E24 Series) | －55 to ＋155 | Pending |
| F (±1%) | |||||||
| UCR01 | 1005 | 1/8W (0.125W) | J (±5%) | 0 to 300 0 to 250 0 to 200 | 68mΩ to 91mΩ (E24 Series) 100mΩ to 200mΩ (E24 Series) 220mΩ to 910mΩ (E24 Series) | YES | |
| F (±1%) | |||||||
| UCR03 | 1608 | 1/4W (0.25W) | J (±5%) | 0 to 250 0 to 200 0 to 150 | 20mΩ to 47mΩ (E24 Series) 51mΩ to 91mΩ (E24 Series) 100mΩ to 200mΩ (E24 Series) | YES (100mΩ and higher) | |
| F (±1%) | |||||||
| 1/5W (0.2W) | J (±5%) | 0 to 150 | |||||
| F (±1%) | |||||||
| UCR10 | 2012 | 1/3W (0.33W) | J (±5%) | 250±100 0 to 250 0 to 150 | 11mΩ to 15mΩ (E24 Series) 20mΩ to 47mΩ (E24 Series) 51mΩ to 100mΩ (E24 Series) | YES | |
| F (±1%) | 0 to 250 0 to 150 | 11mΩ to 47mΩ (E24 Series) 51mΩ to 100mΩ (E24 Series) | |||||
| UCR18 | 3216 | 1/2W (0.5W) | J (±5%) | 0 to 350 0 to 200 0 to 150 | 11mΩ to 18mΩ (E24 Series) 20mΩ to 39mΩ (E24 Series) 43mΩ to 100mΩ (E24 Series) | YES | |
| F (±1%) |
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