news

The common failure modes of thick-film heater are mainly breakdown, burning of thick-film circuit, burning of electrical connection contact, etc., while the burning of thick-film circuit is * the main failure mode, and also the major failure mode. Through consulting with the manufacturer of flat thick film heater, the effective mechanism of thick film heater is summarized as follows.

Withstand voltage breakdown mainly occurs in the production cycle of thick film components. The main reasons for the breakdown of thick film components are as follows:

The influence of substrate material, the metallographic structure, composition and surface roughness of the substrate have an important impact on the insulation effect of the insulating medium. The metallographic structure and chemical composition affect the corrosion resistance of stainless steel, while the composition of stainless steel determines its expansion coefficient. If the expansion coefficient of the slurry and the substrate is inconsistent, the medium slurry may crack or even delaminate during the high-temperature sintering process. The surface roughness will also directly affect the adhesive effect of the medium. Selecting the appropriate roughness can improve the adhesive effect. At the same time, the cleanliness of the substrate surface will also affect the insulation performance. Therefore, the substrate materials must be strictly controlled, and the chemical composition, surface roughness, surface cleanliness, etc. need to be consistent.

Influence of sintering process and sintering equipment. Each slurry has a specific sintering curve, and the sintering temperature and time are usually determined by the properties of the slurry. On the one hand, it requires high precision of sintering equipment; on the other hand, it requires that the sintering process must meet the sintering curve, whether there will be voids and other phenomena, which will affect the insulation performance.

Impact of production environment. Environmental temperature, humidity and air dryness will affect the insulation performance of the product. The production process must strictly control environmental factors.

During the use of the product, the insufficient creepage distance caused by liquid leakage or moisture adhering to the surface of the heating body will also lead to breakdown.

The burning of thick film circuit mainly occurs in the use stage of the product. The main reasons for this phenomenon are as follows:

The thickness of heating resistance is uneven. Both the screen printing and sintering process will affect the thickness uniformity of the thick film resistance. When the thick film is uneven, the weak link will have large resistance and heat, which is easy to form a hot spot, and will eventually burn out.

The temperature field on the surface of the heating body is uneven. Generally, the wiring mode on the surface of the thick monkey heating body and the structure of the product have a great impact on the distribution of the temperature field when the temperature field is uneven

It is easy to cause circuit damage due to different expansion coefficients of each part of the substrate and heating wire. The uniformity of temperature field is one of the important indexes in the design of thick waist heater.

Temperature controller protection is not timely. When the appliance is under dry burning or other conditions that lead to abnormal temperature rise, the heating body will be protected at 100 ℃ per second or even in time, * which will eventually lead to the damage of the heating resistance. Therefore, the selection of protector is crucial to the service life of thick film heat exchanger.

High power density or current density. Generally, the power or current density of the thick-die heater should have enough margin. The margin is insufficient, which will lead to the failure of the thick resistor in the case of time accumulation or other abnormal conditions.

Substrate deformation. If the substrate material or structural design is unreasonable, or the substrate is deformed due to other structural reasons, the thermal resistance attached to it will also be damaged due to phase change.

Due to the large working current of the thick film heater, the electrical contact point is also a weak part of the heater. Under the influence of the hot and cold alternation of the working environment of the heating element, the wet environment and other factors, it is easy to cause the contact to oxidize, heat and burn. Generally, the thickness and area of the thick film conductor material should be reserved during the design, and the contact thickness and silver content should meet the actual use requirements. In addition, the contact and the thick film conductor should be elastically connected with the elastic sheet material, which is generally better to use beryllium bronze, because beryllium bronze has good elasticity and electrical properties.