The reliable performance requirements of DC-DC converter to the production environment

2012-6-11 19:35:02  clicks:2905

                         The reliable performance requirements of DC/DC converter to the production environment
   In the modern  high technology times,for DC-DC power converter reliability requirements are higher, but the AC-DC conversion , DC-DC conversion has become module or integrated chip industry , has gradually become an important part of a variety of electronic equipment, industrial automatic control equipment,so the quality and reliability of AC-DC and DC-DC converter Largely affected the overall equipment reliability,failure rate and maintenance rate .
    Design, technology, management, testing and tools, raw materials and other factors affect the reliability of converter,user and manufacturers should pay attention to these key pionts. 
In fact, the reliability of the converter not only to ensure to optimize the performance indicators,but also to ensure the production environment of converter is clean and orderly with good static protection,appropriate temperature and humidity,converter only under such a production conditions  can really be called a high-reliability converter.
   With society progressing,the electronic equipment in industrial production,transportation, communication and other fields are playing an increasingly important role,the reliability of electronic equipment to some extent determines the effective operation of economic activities,Although the power modules share a very low cost, but can be called a "heart" of
electronic device ,the module failure could directly lead to an electronic device paralysis and cause irreparable damage.
    Static electricity protection:
    Components in the  manufacture,storage, transport and assembly process, due to the mutual motion bteween equipment, materials and the the operator due to the friction generated electrostatic voltage, when devices contact with those electrical body, which will discharge through the devices, causing devices failure.
    Most modern integrated circuits adopt MOS circuits,and converter are also mostly used MOS transistor and integrated circuit chips. static electricity in the converter production will lead to higher component damage rate. Even after testing qualified products, may also due to static electricity in the manufacturing process to  minor injury MOS transistor and integrated circuit chip,thus affecting the lifetime and reliability of the converter.after introducing in a static electricity protection system in the production environment(adopting human anti-static grounding ,floor anti-static grounding and operating device , instrument anti-static grounding , etc. )can effectively avoid the damage to the MOS transistor and integrated circuit chips. electronic components static electricity protection damage is a complicated systematic project,which throughout the entire process of system or equipment development and production.From components procurement, packaging, transportation , storage, installation, commissioning , testing until to the user , the whole process , all the staff should follow a series of anti-static related measures. Protection is a systematic project , there must be investment in equipment、personnel、 effective management and rules Thus, an electrostatic protection system will directly reflect the quality of an enterprise management level,which shows an enterprise strength.
    Second, humidity :
    Moisture penetrate into the porous material causing leakage path between the conductors to generate oxygen, moisture absorption components lower the insulation resistance ,isolation voltage ability decreased. However,excessive drying also cause some materials become brittle、rough surface and even generate static electricity. Therefore, the production environment of converter will have some impact to reliability.
    Most of the converters are soldered the small components in the PCB (printed circuit board),and then potting the PCB board into the housing with resin.
In the production process,if the production environment is too damp, especially in the southern rainy season,the moisture in the air will condense in the PCB board and components , even potting with resin, removed air bubble by a vacuum defoaming process, but can not  remove moisture on the PCB and components. When the converter operates in high temperatures,the moisture of the PCB board and component vapor expansion,causing cracks in the converter, Pull off the internal transformer lines or introducing external moisture lead to corrose converter internal components or internal short circuits. For  high requiring isolation voltage applications ,the moisture in the PCB board and components will reduce the isolation capability of converter,and even cause the breakdown between the initial level,lead to serious consequences.
Low humidity will cause too much dust floating in the air and affecting the quality of the converter. Also will generate static electricity charge for the personnel move,even if protected by electrostatic protection system , can also cause static electricity damage components or soft breakdown, resulting the same consequences described earlier.
Introducing air conditioning systems and dehumidifiers system in a production environment to enables the production environment to maintain an appropriate level of humidity to avoid condensation of moisture or the too dry air causing bad effecte to the reliability of the converter.
Humidity affect the product
    Immersed in the resin moisture in the air in
Heating the initial , small amounts of water vapor pressure stratification of a synthetic resin interface
     As the vapor pressure of the welding temperature, the expansion of the resin
     Water vapor is discharged through a package cracks , creating products undesirable phenomena.
     Moisture of the product
     Moisture in the air immersed in the resin,small amounts of water vapor pressure causes stratification of resin interface in the initial heating water vapor pressure with the welding temperature elevating,the resin expand. 
     Water vapor is exhausted through a package cracks causing products undesirable phenomena.
     Third,temperature:
Production envirenment temperature also requires strict control.High and low temperature for the components are there different degrees of impact.
3.1 High temperature
     The high temperature environment will cause the converter internal resistors, inductors, capacitors and power etc.electrical parameters change.which leading to the insulators soften to cause insulation failure ; active components may get stuck due to expansion causing structural failure,Coated surface blistering, accelerated oxidation and other chemical reactions, the lubricant viscosity lower and evaporation causing loss of lubricity;due to physical expansion increase the wear of moving parts and fall the structural streng.
   
3.2 Low temperature
    Low temperature environment causes plastic and rubber of converter lossing flexible turns brittle , icing occurs when there is moisture , lubricants becomes gelatinous and sticky and lose lubrication
; coated surface cracking ; leaving due to the physical structure of contraction failure to change the electrical and mechanical functions.
    3.3 Temperature Control
    Especially small volume converter such as 1W, 2W , usually adopting magnetic ring winding transformer, its diameter less than 5mm , such transformer just use handmake, when in the higher
production temperatures,the production staff will remain sweat from hands on  winding transformer,
Where moisture and salt will damage the patent leather of transformer,reducing transformer insulation capability, will potentially affected the reliability of converter.
 Installation of air conditioning thermostat system in the workshop to ensure that the room temperature maintained at 26 degrees, so that the production staff has a cool and comfortable environment in order to produce quality and reliable products.
Fourth,dust :
    Multiple dust may scratch converter, wearing surface , resulting in clogging, contaminate lubricant, contamination insulation ,corona passage and falling electric performance.
Such as the production environment dirty, floating dust  in the air falls on the PCB, components Weld, false welding situation will be greatly increased, not only for the production pass rate cause some impact, but also cause product reliability and product lifetime question.Focus on clean production environment , improve 5S management to ensure the production of qualified and reliable.
    The northern weather  dust serious  than  south, so need to pay more attention to control ,such as adopt  air filtration, sealing, exhaust systems and other methods to solve them.
 Fifth , storage and safekeeping
    Improper storage and safekeeping is another important reason for resulting in components reduced reliability or failure,so must pay attention and take appropriate action.
such as the warehouse temperature and humidity should be controlled within prescribed limits,using moistureproof cabinets, pay attention to moistureproof, anti-static, prohibit harmful gases presence  and regularly reviewed.
    container for storage components  should use anti-static and unlikely to cause a chemical reaction  made ??of a material , regular check sensitive components.
Electronic raw materials should be gently transporting、 take and put , the raw materials  ceramic capacitors, magnetic materials  are easily cracked, especially when using and handling should be noted.
    In summary, the production environment management is an important guarantee to the converter reliability, these management needs enterprise human, material resources, the management measures need to be implemented, not just write on paper, speaking at the meeting, paste on the wall.Production environment management level epitomizes a Manufacturing enterprises production capabilities,only rely  on the quality survival is a real Everlasting Enterprises
    People increasingly rely on modern technology, as an electronic equipment energy source- converter has become a very important even the most critical components in electronic systems, converter reliability is also increasingly attracted the attention of electronic equipment manufacturers, which also requires more to the converter manufacturers,the production environment and production management assessment is also listed as an important supplier assessment.
     
DC-DC converter picture: