- Core application module of thick-film resistors in food delivery robots: The core workflow of a food delivery robot is “power supply → main control instructions → sensing and detection → motion execution → auxiliary interaction”. Thick-film resistors perform basic electrical functions such as current limiting, voltage division, sampling, pull-up/pull-down, and matching in each module. Different modules require different specifications of thick-film resistors to precisely match their power consumption and accuracy requirements.
- Key requirements for selecting thick-film resistors for food delivery robots: The working characteristics of a food delivery robot are “mobile vibration + indoor multi-temperature zones + commercial high load (8~12 hours per day) + high humidity/oil fumes in restaurants”. Therefore, the selection of thick-film resistors must meet both operational adaptability and electrical performance requirements to avoid robot downtime, misjudgment, and loss of control due to resistor failure:
Packaging and miniaturization: SMD thick film resistors (primarily 0402/0603/0805) are preferred, suitable for high-density layout of robot circuit boards (due to limited internal space, power boards/main control boards are mostly miniaturized PCBs). For high-power modules (power supplies/motors), 2512/1206 power-type SMDs can be selected to replace plug-in resistors, further saving space.
Power and Temperature Resistance: The main control/sensing module should be chosen for low power (1/16~1/8W), while the power supply/drive module should be selected for medium to high power (0.5~3W). The temperature range should meet the requirements of -40℃~+125℃, accommodating the temperature variation environment of restaurant air-conditioned rooms (low temperature) and motor/power supply heating (high temperature).
Accuracy and temperature drift (TCR): For conventional control/current limiting, a precision of 5%/1% is sufficient; the sensing and detection module is the core, requiring a high precision of 0.1% to 0.5% coupled with low TCR (±25/±50ppm/℃) to avoid resistance drift due to temperature/vibration, which could lead to incorrect obstacle avoidance decisions and inaccurate food weight detection.
Vibration resistance and adhesion: Select resistors with high adhesion and thick film technology (where the thick film layer is tightly bonded to the ceramic substrate), meeting the IEC mechanical vibration standards (generally ≥10g acceleration), suitable for bumps and wheelset vibrations during robot travel, to prevent the resistor film from peeling off and sudden changes in resistance value.
Environmental protection: For the high humidity, oil fume, and slightly corrosive environment of restaurants, the resistance needs to meet moisture resistance (above IP40) and salt spray resistance (48 hours). It should be combined with the overall conformal coating treatment of the circuit board to prevent oxidation of the resistance pins and moisture-induced failure of the film layer.
3. Compared to other resistors, thick-film resistors have core advantages that make them suitable for food delivery robots. Food delivery robots are commercial mass-produced equipment with high requirements for “cost + reliability + production efficiency”. Compared to thin-film resistors and carbon film resistors, thick-film resistors are the most suitable choice, with five core advantages:
High cost-effectiveness and suitable for large-scale production: The thick film resistor technology is mature and the production cost is low (far lower than that of thin film resistors), meeting the bulk procurement needs of food delivery robot manufacturers. Each robot requires approximately 50 to 200 resistors, and the low cost can significantly control the overall BOM cost of the robot.
High power density and strong adaptability to miniaturization: Thick-film resistors, with ceramic as their substrate, exhibit excellent heat dissipation. In the same package, their power output significantly surpasses that of carbon-film resistors (for instance, a 0805 thick-film resistor can achieve 1W, whereas a carbon-film resistor can only manage 0.25W). This makes them an ideal fit for the miniaturized layout of robot circuit boards.
High reliability and adaptability to mobile working conditions: The thick film layer is made of high-temperature sintered metal ceramic slurry, featuring high mechanical strength and resistance to vibration/impact. Unlike carbon film resistors, which are prone to wear and resistance drift, this film layer can meet the long-term operational requirements of high-load mobile robots (commercial robots require trouble-free operation for ≥10,000 hours).
Compatible with automated production and enhancing production line efficiency: The chip thick-film resistors are perfectly compatible with the fully automated SMT chip mounting process. The circuit boards of the meal delivery robots are all produced through large-scale SMT, eliminating the need for additional production line adjustments and significantly improving production efficiency.
Stable electrical performance and small temperature/load drift: Compared to carbon film resistors, thick film resistors exhibit smaller drift in resistance with temperature and load, ensuring long-term stability of the circuit and avoiding issues such as power overcurrent, motor stall, and sensor misjudgment caused by resistor drift.
4. Precautions for Practical Applications: High-power modules require enhanced heat dissipation: The 1~3W power-type thick-film resistors on the power board and motor drive board should be kept away from heating components (such as MOSFETs and chips) on the PCB. If necessary, copper sheets can be placed under the resistors to dissipate heat and prevent overheating and burnout of the resistors.
Separate selection and control of sensing modules: High-precision thick-film resistors for obstacle avoidance and weight detection require separate incoming inspection to avoid the inclusion of resistors with unqualified precision, which could lead to the failure of the robot’s core detection functions (such as collisions with people and food falling).
Coordinating with circuit board three-proofing treatment: The oil fumes and water vapor in the restaurant environment are the main causes of resistor failure. The robot’s circuit board needs to be sprayed with three-proofing paint (moisture-proof, salt spray-proof, and mold-proof) to cover the film layer and pins of the thick-film resistor, thereby enhancing the overall protection level.
Avoid exceeding specifications: It is strictly prohibited to use low-power thick-film resistors in high-power circuits of power supplies/drivers. Otherwise, the resistors may instantly heat up and burn out, causing short circuits on the circuit board and robot shutdown.
