Terminal blocks are usually faced with a variety of different environmental factors, for example: in the transportation and storage process, in the manufacturing process, installation, repair and terminal customers use the process. These environmental factors can be understood as the established state, concrete can be subdivided into temperature, humidity, corrosion, pollution, external and internal conditions and human factors. You must also define, among these environmental factors in exposed to changing circumstances duration.
The influence of environmental factors on terminals, storage and transportation
The first two environmental factors, warehousing and transportation is very easy to understand. They affect all kinds of products, therefore, the majority of procurement, sales, operating personnel and engineers are quite a lot of experience.
Terminal storage environment is different from control, clean, heating or air conditioning, wet warehouse, office or factory, to be the corresponding control environment. In the heat, moisture or corrosion circumstances will seriously affect the terminal service life. In the controlled environment, welding storage life due to oxidation, corrosion, intermetallic effect intensifies greatly reduce; metal device surface and function are due to rust, patina and other forms of corrosion and affected; as insulating material of plastic and also because of flexibility, strength, the shape of the degradation affected by the. Terminal storage period can be short or long, long months or years, while a few short days, weeks, some needs of customers to make long-term planning, while others place an order immediately out of production. Through the use of FIFO inventory strategy, can be traced back date label system, the appropriate package, corrosion prevention method, improved storage conditions as well as the appropriate terminal material and terminal design, can improve the reliability and prolong the storage life of.
Transport environmental factors involved in transport vehicles and other mechanical devices, pavement, | handling hardware tools in the course of the operation the vibration and impact caused problems. And temperature extremes are often combined and vibration, impact of a collision. Ocean shipping terminals are often exposed to salt spray environment. Transportation time is generally predictable, land and air for several days, and the sea is January years or months. Terminal and packaging materials to the transport processes in intact, to prevent decomposition, deformation resistance, corrosion resistance and extrusion. Usually take the following measures will improve the reliability of transportation, so that the smooth arrival of goods to destination: use reputable carrier, using appropriate packaging materials, strong internal and external packing box, suitable lining material or filler, necessary anti-corrosion measures and appropriate terminal material and design.
The influence of environmental factors on Terminal - welding conditions
The welding conditions are significantly different, depending on the connection type and welding process. Suitable for wave soldering, mounted on the PCB board terminal block is a typical punch mounting type. Perforation of the welding pin must be accurate positioning, size, balanced placed, and good weldability, so as to facilitate the insertion and soldering. Throughout the assembly process, must be able to withstand the high temperature and preheating zone through wave soldering is transmitted to the terminal body temperature. The flux may not affect terminal, must be easy to remove, there can be no residue. The entire assembly process must be cleaned with water. Preheating temperature often reaches to 100 degrees C or higher, the temperature reached 280 degrees C peaks are also not uncommon. Come unexpectedly high temperature often make terminal melting, twisted, blistering and deformation. Assembly time is generally divided into, a few minutes exposure in the flux of time, a few minutes warm-up period, a few seconds of the wave period, and a few minutes of washing and drying period.
Select the appropriate metal material, resin can improve the reliability of the welding.
Suitable for reflow, mounted on the PCB board connection terminals for surface mount or through hole mounting. Surface mount solder pin must be positioned correctly, size, and PCB plate completely coplanar or micro to adapt PCB board all tin plate, ensure the welding have sufficient strength, quality and reliability of the circuit ( without breaking, see Exhibit 1 ). Perforation of the welding pin must be accurate positioning, size, balanced placed, and good weldability, so as to facilitate the insertion and soldering. Throughout the assembly process must withstand heat treatment at high temperature to produce impact, in the welding mainly using infrared preheating and convection preheat the heat to the solder pin and tin plate interface to melt the solder paste. Then do not have mandatory clean, but it is generally expected to cleaning. Preheating zone temperature set for general peak at 230 degrees C, a few minutes after the temperature is higher. With wave soldering, come unexpectedly high temperature often make terminal melting, twisted, blistering and deformation. Assembly time is generally divided into a few minutes warm-up period, a few seconds of the peak, and a few minutes of washing and drying period. Of course, choose the appropriate metal material, resin can improve the reliability of the welding.
Penetrating type terminal row, electronic module and the ceramic terminal are often the manual assembly, reliability depends mainly on the operation in the process of human factors, such as: screwdriver strength, tight line when the torque size and mounted on the board of the screw fastening degree. Too large torque or uncontrollable screw fastening strength will seriously affect the connection properties, sometimes performance significantly, sometimes in the field wiring is not easy to be detected, when after a period of time, the use of a few weeks or months after just appeared.
Terminal usage is extremely important, because it is the terminal of the raw materials, assembly configuration and wiring terminal comprehensive cost plays a vital role in. Comprehensive cost includes terminal purchase, repair and maintenance costs. Customer satisfaction and manufacturer's reputation is also part of the cost equation.
The following factors need to be considered:
Application of places, such as internal or external, tropical zone or sea area, fixed or mobile zone ( for example: a vehicle passenger area or engine area)
Temperature and humidity range of normal and extreme conditions
When the circuit is opened or closed, in the using process of the temperature in the casing or near the heat source temperature;
Exposure to pollutants, dust (with conductive or without conducting ), corrosive gas or liquid;
Exposure to vibration, impact, penetration, voltage spike, current overload environment;
Reduced rating principles - when environmental conditions become serious, the Engineer shall reduce the components of the rated value;
Human factors, including regional wiring and torque, installation and repair process intensity and abuse;
The relevant laws and regulations, and some require UL ( American Underwriters Laboratories ), CSA ( Canadian industry standards ) or other certification, the certification involves flame retardancy, clearances and creepage distances, insulation voltage, impulse withstand voltage, the risk of electric shock test and the related standards of performance;
Customer clear or not clear requirements statement
Conclusion
In the storage, transportation, welding, assembly and terminal using the environment, terminal performance excellence is not incidental to, this is the precision design, R & D and fine processing the result of unremitting efforts. In the era of globalization, the cost of the product not only includes the purchase cost, but also must consider the product in a series of application performance.