Introduce the differences between the CRH and CUH series resistors from the Tian Er brand

I will provide you with a detailed introduction to the differences between the CRH and CUH series resistors from the Tian Er brand. The main content is as follows:
Product positioning and core differences: Introduce the basic positioning and core differences of two series, including power density and applicable scenarios.
Power capability and heat dissipation design: Compare the power parameters and heat dissipation technologies of two series, and use specific data to illustrate the differences.
Process technology and material evolution: analyzing the impact of manufacturing process differences and material innovation on performance.
Accuracy and temperature characteristics: Compare the accuracy levels and temperature coefficients of two series to demonstrate their performance in different environments.
Application scenarios and typical use cases: List two series of typical application scenarios and industry cases respectively. 
Selection decision points: Summarize the key considerations for selecting two series and provide guidance on the decision-making process.
Next, let's start the main text: 
In the field of electronic components, although resistors are basic components, they play key roles in circuit design such as current control, voltage division, and signal conditioning. As an old resistance manufacturer in Taiwan, China, EverOhms has formed a clear technical distinction in performance boundaries and application scenarios, although its CRH and CUH thick film patch resistance series are of the same origin. Understanding the differences between the two is of great significance for optimizing circuit design, balancing cost and reliability.   
1. Product positioning and core differences
The CRH series is positioned as a universal thick film resistor, with "balance" as its core label, covering a wide range of needs from consumer electronics to industrial equipment. Its design follows industry standards, providing 2W power in a 2512 package (6.4mm × 3.2mm), with a resistance range covering 0.5m Ω to 30M Ω, and an accuracy of ± 5% (J range), while also considering ± 1% (F range) options.   
The CUH series focuses on breakthroughs in high power density, increasing the power carrying capacity of resistors of the same size by 30% to 100% through structural innovation. For example, in the 2512 package, the CUH power can reach 3W; even in the 0603 micro package (1.6mm × 0.8mm), a power of 0.33W can be achieved (such as CUH0603J2K20P05Z), far exceeding the 0.1W upper limit of the standard 0603 resistor. The "U" in its name implies "Upgraded Power", designed specifically for scenarios with limited space but strict power requirements.   
Core difference: CRH is a universal choice that is "sufficient and economical", while CUH is a power density expert who "beats small for big". The relationship between the two is similar to that of a family sedan and a high-performance off-road vehicle - the infrastructure is similar, but the latter has been deeply strengthened for special road conditions.
2. Power capability and heat dissipation design
The power difference stems from the innovation of heat dissipation technology:
CRH: Relying on conventional PCB copper foil heat dissipation, the nominal power value is based on an ambient temperature of 70 ℃. In high-temperature scenarios, a significant derating is required, for example, at 100 ℃, the actual available power of a 2W resistor is only about 0.8W
CUH: Adopting triple heat dissipation optimization:
1. End electrode structure: Thickened coating (such as nickel chromium alloy) enhances thermal conductivity efficiency;   
 
2. Substrate material: high thermal conductivity alumina ceramic (thermal conductivity ≥ 5W/mK), accelerates heat transfer to PCB;   
3. Resistance paste formula: Adding metal oxides to enhance high temperature resistance and support continuous operation at 155 ℃.   
Actual measurements have shown that the surface temperature of CUH is 15 ℃~20 ℃ lower than that of CRH at 3W full load, significantly delaying the slope of the derating curve. This means that in enclosed power modules or high-temperature environments, CUH can maintain higher effective power, reduce the number of parallel resistors, and simplify the layout.   
 
3. Process technology and material evolution
Both series use thick film technology (screen printing+high-temperature sintering), but CUH has been upgraded in key areas:
 
|Process Link | CRH Series | CUH Series|
|Thickness of resistance layer | Conventional thickness (about 50 μ m) | Thickened to 100 μ m|
|Slurry composition | Conventional ruthenium based oxide | Doped tungsten/silver particles to enhance current carrying capacity|
|Sintering process | Standard 850 ℃ sintering | Step temperature controlled sintering to reduce porosity|
 
These improvements have increased the power density of CUH to 70W/cm ² (CRH is approximately 40W/cm ²), while also improving its anti pulse capability, which can withstand 100A surge current within 5ms (such as at the moment of motor start-up). But the cost is an increase in cost - the unit price of CUH is about 20% to 30% higher than CRH under the same size.   
4. Accuracy and temperature characteristics
In terms of electrical parameters, there is a subtle balance between the two series:
Accuracy: Both offer a ± 1% (F-level) option, but the ± 5% (J-level) version of CRH is more common and economical, suitable for non precision scenarios such as power filtering.   
Temperature coefficient (TCR): The typical TCR for CRH is ± 100ppm/℃, while for CUH, due to slurry modification, the TCR for some models has been expanded to ± 400ppm/℃ (such as CUH2010F2R20E04Z). This is because high-power design requires priority optimization of heat dissipation, sacrificing some temperature drift performance.   
Design trade-off: If the circuit needs to meet both high power and low temperature drift requirements (such as precision current detection), the power advantage of CUH and the disadvantage of TCR need to be balanced. At this point, metal film resistors (such as the Tian'er TGL series) can be considered, but their cost is higher and their power is lower than CUH.
5. Application scenarios and typical use cases
Applicable scenarios of CRH series:
Consumer electronics: current limiting resistors for mobile phone chargers, LED driver substrates, utilizing their cost advantages;   
Industrial control: PLC module I/O port pull-up resistor, mild environment and power requirement ≤ 1W
Universal power supply: AC/DC converter feedback resistor, used in conjunction with ± 1% precision version.   
CUH series irreplaceable scenes:
High density power module: In the brick power supply of 5G base stations, CUH0603 saves 60% space for board layout at 0.33W power;   
Automotive Electronics: Engine Control Unit (ECU) pre driver, capable of withstanding high cabin temperatures (125 ℃) without the need for additional cooling fins;   
Surge resistant circuit: such as the buffer resistor of the frequency converter, capable of withstanding the motor's anti peak voltage (such as CUH2512F4R70P05Z, with a surge resistance of up to 2000V).   
6. Key points of selection decision
 
Choosing CRH or CUH requires a comprehensive consideration of four core factors: