Influence of the hottest environmental factors on

2022-10-01
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The influence of environmental factors on terminal blocks

topic: the field of reliability includes the evaluation and optimal selection of a variety of established factors. Terminal blocks are usually faced with a variety of different environmental factors, which can be understood as established conditions, specifically divided into temperature, humidity, corrosion, pollution, internal and external conditions and human factors. In these environments, Levitate running shoes must also be defined as the duration of Brooks' exposure to changing conditions after 7 years of running research

key words: terminal block, use environment

reliability is a very important consideration in business decision-making. In the view of a quality engineer or reliability engineer, reliability should be defined as follows, "the continuous performance or maximum possibility of zero failure operation under given conditions," or "the maximum possibility that something can normally perform its expected function under given conditions and within a specific interval."

the field of reliability includes the evaluation and optimal selection of a variety of established factors, and it is often decided by both parties to adopt some standardized or pioneering methods. Some technical terms such as "derating" and "inefficiency" are often used in the field of reliability. Generally, reliability engineers and quality engineers certified by the American quality association have professional knowledge in this field

wiring terminals usually face many different environmental factors, such as: in the process of transportation and storage, in the process of manufacturing, in the process of installation, maintenance and use by end customers. These environmental factors can be understood as established conditions, which can be divided into temperature, humidity, corrosion, pollution, internal and external conditions and human factors. It is also necessary to define the duration of exposure to changing circumstances in these environmental factors

warehousing and transportation

the first two environmental factors, warehousing and transportation are easy to understand. They affect all kinds of products, so most purchasing, sales, operators and engineers are quite experienced in this

the storage environment of wiring terminals varies from controllable clean, heated or air-conditioned, humid warehouses, offices or factories to uncontrollable corresponding environments. The service life of the terminal will be seriously affected by heating, humidity or corrosion. In these uncontrollable environments, the storage life of weldability will be greatly reduced due to the intensification of oxidation, corrosion and intermetallics; The surface and function of metal devices will be affected by rust, copper green and other forms of corrosion; As an insulating material, plastics will also be affected by the degradation of flexibility, strength and shape. The storage life of terminal blocks can be long or short, ranging from months and years to days and weeks. Some need to make long-term inventory plans for customers, while others order production and then leave the warehouse. By adopting first in first out inventory strategy, traceable date label system, appropriate packaging methods, anti-corrosion methods, improving storage conditions and appropriate terminal materials and design, the reliability of terminal blocks will be improved and the storage life will be extended

transportation environmental factors involve problems caused by the vibration and collision of transportation vehicles and other mechanical devices, roads, loading and unloading tools during operation. Extreme temperatures often combine and intensify the effects of vibration and collision. The terminal blocks are often exposed to salt fog during shipping. The transportation time is generally predictable. The land transportation and air transportation are generally several days, while the sea transportation is as long as one month or several months. The wiring terminals and packaging materials must be resistant to decomposition, deformation, corrosion and extrusion if they want to be intact during transportation. Generally, the following measures will improve the reliability of transportation and make the goods arrive at the destination smoothly: using a reputable carrier, using appropriate packaging materials, solid inner and outer packaging boxes, appropriate linings or fillers, necessary anti-corrosion measures, and appropriate terminal materials and design methods

welding conditions

welding conditions are significantly different, which depends on the type of terminal blocks and the steps of the welding process. The wiring terminal suitable for wave soldering and installed on PCB board is a typical perforated installation type. The perforated welding pin must be accurately positioned, appropriately sized, evenly placed, and have good weldability, which is conducive to insertion and welding. In the whole assembly process, it must withstand the high temperature in the preheating zone and the temperature transmitted to the terminal body through wave soldering. The flux shall not affect the terminal, and must be easy to remove without any residue. The whole assembly process must be able to be cleaned with water. The preheating temperature often reaches 100 ° C or higher, and it is not uncommon for the peak temperature to reach 280 ° C. Sudden high temperature often makes terminals melt, twist, blister and deform. The assembly time is generally divided into a few minutes of exposure to the flux, a few minutes of preheating period, a few seconds of peak period, and a few minutes of cleaning and drying period. Choosing appropriate metal materials and resins can improve the reliability of welding

Figure 1: the cross section of the welding interface

is applicable to reflow soldering. The wiring terminals installed on the PCB board are generally surface mounted or through-hole mounted. The surface mounted solder pin must be correctly positioned, of appropriate size, completely coplanar with the PCB or slightly floating to adapt to all tin plates on the PCB, so as to ensure that the welding has sufficient strength, process quality and circuit reliability (no open circuit, see Figure 1). The perforated welding pin must be accurately positioned, appropriately sized, evenly placed, and have good weldability, which is conducive to insertion and welding. In the whole assembly process, it must withstand the high-temperature impact produced by heat treatment. In welding, infrared preheating and convection preheating are mainly used to transfer heat to the interface between the welding needle and the tin plate to melt the solder paste. Next, there is no need to force cleaning, but people generally expect cleaning. The temperature of the preheating zone is generally set at 230 ° C peak, and the temperature will be higher after a few minutes. Like wave soldering, sudden high temperature often makes terminals melt, twist, blister and deform. The assembly time is generally divided into a few minutes of preheating period, a few seconds of peak value, and a few minutes of cleaning and drying period. Of course, choosing appropriate metal materials and resins to ensure the quality and progress of your work can improve the reliability of welding

through terminal blocks, electronic modules and ceramic terminals are often assembled manually, and the reliability mainly depends on human factors in the operation process, such as the strength of the screwdriver, the torque when tightening the wire, and the tightening degree of the screws installed on the board. Excessive torque or uncontrollable screw tightening will seriously affect the connection performance. Sometimes the performance is obvious, sometimes it is not easy to be detected when wiring on site, and it will appear after a period of time, weeks or months of use

terminal usage

terminal usage is extremely important, because it plays a vital role in the raw material requirements of terminals, assembly configuration and the comprehensive cost of wiring terminals. The comprehensive cost includes the cost of procurement, repair and maintenance of wiring terminals. Customer satisfaction and manufacturer's reputation are also part of the cost equation

the following factors need to be considered:

1 base metals and precious metals are difficult to have turnaround applications, such as internal or external, tropical or marine areas, fixed areas or mobile areas (such as passenger areas or engine areas in motor vehicles)

2 temperature and humidity normal range and extreme conditions

3 when the circuit is opened or closed, the temperature in the housing during use or the temperature close to the heat source

4 exposure to pollutants, dust (with or without conductivity), corrosive gases or liquids

5 exposed to vibration, collision, penetration, voltage sharp pulse, current overload environment

6 principle of reducing the rated value - when the environmental conditions become extremely serious, the engineer should reduce the rated current value of components

7 human factors, including regional wiring and torque, strength and misuse during installation and maintenance

8 relevant laws and regulations, some require UL (Underwriters Laboratories of the United States), CSA (Canadian industry standard) or other certifications, which involve flame retardant performance, electrical clearance and creepage distance, insulation voltage, impulse withstand voltage, shock hazard test and performance of relevant standards

9 customers' clear or unclear requirements

conclusion

in the whole storage, transportation, welding, assembly and terminal use environment, the excellent performance of wiring terminals is not accidental, which is the result of unremitting efforts in precision design, research and development and fine application processing. In the era of globalization, the cost of products not only includes the purchase cost, but also must take into account the performance of products in a series of application environments

terminal application: PCB board, track type, panel of related equipment

Original: famous foreign connector magazine connector specifier December, 2002,

link:

Author: Michel hodak, manager of Quality Department of weco Canada

(weco electrical connectors Inc., e-mail: mhodak@, web site:)

translator: Han Jinxiao, weco China, Marketing Manager of Shenzhen Victor Electric Co., Ltd.

(email: n@, web site:)

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