Circuit board processing weldability is bad, will produce a virtual welding defects, the components in the circuit parameters, lead to a multilayer components and inner line conduction is not stable, caused the entire circuit function failure.
The so-called weldability is the nature of the metal surface is molten solder wetting, namely the solder in the metal surface to form a layer of relatively homogeneous continuous smooth adhesive film.
Circuit board processing factors, which affect the printed circuit board solderability mainly include: the nature of the composition of the solder and solder.
Solder is an important part of the welding in the process of chemical treatment, it is composed of containing flux of chemical materials, commonly used low melting eutectic melting metal for Sn, Pb and Sn Pb - Ag.
The impurity content should have certain points than control, to prevent dissolve impurities generated oxide by flux.
Is the function of flux by passing heat, remove rust to help solder wetting by welding plate surface of the circuit.
Generally USES white rosin and isopropyl alcohol solvent.
Circuit board processing temperature and degree of metal plate surface clean will also affect the solderability.
Temperature is too high, the solder diffusion speed, has the very high activity at this time, can make the circuit board and solder melt oxidation surface rapidly, produce welding defects, circuit board surface pollution can also affect the weldability to produce defects, these defects including tin beads, tin ball, open circuit, glossiness is bad, etc.
In order to ensure the board face and appearance quickly and lead solder moist very effectively, it is necessary to apply flux.
Usually choose relative density of 0.
87 rosin flux or water-soluble flux.
For coating the flux of the circuit board for preheating, usually should operate in 90 ~ 110 ℃.
Hold good temperature can reduce or avoid the icicles and circle lack of solder joints.
In the process of welding, soldering temperature should normally operate within the scale of 250 ℃ + 5 ℃, the temperature is appropriate directly affect the welding quality.
Should adjust welding jig into wave mouth Angle is 6.
Welding beat linear velocity should be grasp in 1 ~ 1.
6 n /分钟;
About lOmm tin solder groove surface wave height, peak usually operate in 1/2 ~ 213 of PCB thickness, will lead to molten solder flow to the PCB appearance, form a 'bridge'.
Circuit board welding quality planning is tied with circuit board itself, in all, the scale of the circuit board cannot too big, but don't plan is too small.
If said the scale of the circuit board is very big, although in the process of welding provided convenience for the workers, circuit board size is big, welding is easy to control, but there are advantages and disadvantages, welding simple manipulation, but, because of the large scale direct cause printing lines long, impedance also added subsequently, capital follow up, the noise became big;
The scale of the circuit board is too small, that when welding must not simple manipulation, manipulation of the owe good, just simple present adjacent lines after the electricity disturb each other attacks.
So, in order to deal with the above questions, it is necessary to reasonable planning and printed circuit board.