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Any metal in the air environment
its surface will be subject to different degrees of the oxygen or other oxygen-containing gas, such as chemical etching, the surface state of the nature of metal is not a pure single metal state. Therefore, whether to take protective measures, its surface performance welding performance will not be idealized, only by the characteristics of the metal itself and not need to rely on the help of other substances (such as flux) to achieve the idealized welding effect is almost is impossible. Even in the presence of such a possibility, it is also in pay after the results of the high cost price, which is obviously not.
Bad state of the metal surface, the key factors induced Weld phenomenon. The soft brazing process using flux (liquid or gas) can be by means of the role of the flux to obtain the desired clean surface. The degree of cleanliness of the surfaces being soldered function is used in a flux activity. Military electronic products in China until the early 1960s, the commonly used rosin alcohol for flux inherent in such flux with many metal reaction chemical activity is weak, thus Weld phenomenon is particularly serious product has almost become a public hazard. China imported from the former Soviet Union XX missile terminal guidance radar production line in the early 1960s, the Soviet side also specifically provides for the weapon system with a "secret" level flux formula. Many military units in military production would rather stick with activated rosin flux + cleaning process, while the activity is weak no-clean flux is disabled, its purpose is to avoid Weld hidden to the reliability of the weapon system serious eventualities consequences of hazards.
(2) metallized holes through holes adverse
Weldability when the PCB and components meet the requirements (zero-crossing time <1s), and is also suitable for wave soldering process parameters metalized hole through the hole undesirable phenomenon, the main influencing factors should be considered as flowability and activity of the flux due to the mean difference. Hole penetration flux is metallized hole through hole adverse reasons. Therefore, in case of the use the same kind of flux, the flux foam peak coating method less prone to undesirable phenomena of the metallized hole through hole, while the use of the flux spray coating method metallized hole through hole undesirable phenomena probability will be much higher. This phenomenon occurs because the spray coating method is susceptible to blocking and appear through the holes caused by poor.
? bridging and pull tip
The flux performance advantages and disadvantages of the the wave soldering bridging icicling phenomenon has a greater impact. The excellent flux not only has the desired activity of the welding but also has excellent protection is located in the release region liquid brazing material are not oxidized capacity, which is reduced during peeling of the PCB and solder inhibit bridging and icicling important One of the measures.
In the sense we give a discussion of questions: C line the welders number: ZXA10-ADS2-CORZ (010 502), adjacent gap between the substrate capacitance C415, C542, C413 and C540 are 0.63mm (<1.27mm, improper belongs design), the new nozzle dual wave shown in Figure 2, A and B two hundred percent bridging that occurs only open the second wave of the single wave soldering, but bridgingThe rate is very small. In fact, the problem lies in flux, mainly due to nothing more than:
? flux wave soldering process used in PCB stripped the region has unprotected;
? After the first crest scouring the PCB surface flux has been depleted.
? PCB board surface cleanliness adverse
The flux in the wave soldering process, the chemical composition and the amount sprayed with post-weld residual ion concentration, surface insulation resistance, poor cleanliness and reliability of products in the future use of the process has a direct relationship.
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