Hot air solder working principle and advantages and disadvantages:

HASL is one of the main lead surface treatment processes used in the industry. The process consists of immersing the circuit board in lead-tin alloy and removing the excess solder with a "wind knife", which is the hot air blowing on the surface of the board. For the PCA process, HASL has many advantages: it is the cheapest PCB, and the surface layer can be welded after multiple reflows, cleaning, and storage. For ICT, HASL also provides a process for automatic solder cover test pads and through holes. However, HASL surfaces are very flat or homogenous compared to existing alternatives. There are some lead-free HASL substitution processes that are becoming more and more popular due to their natural substitution characteristics. HASL has worked well for years, but with the advent of "green" technology, its days are numbered. In addition to the lead-free problem, the increasing complexity of the boards and the finer spacing have exposed many of the limitations of the HASL process.
Advantages: lowest cost PCB surface process, maintain weldability throughout the manufacturing process, no negative impact on ICT.

Disadvantages: lead-based processes, which are commonly used, are now limited and will eventually be eliminated by 2007. In the case of fine pin spacing (<0.64mm), this can lead to solder bridging and thickness problems. Uneven surfaces can lead to homogeneity problems in assembly processes.

Hot air solder function advantage:

(1) after the hot air leveling, the composition of the solder coating always remains the same, so that the consistency of the solder coating is good, good weldability. The composition of lead - tin alloy coating changed with the change of the composition of plating solution.
(2) neither the infrared hot melt process nor the hot oil hot melt process can fully protect the side edge of the wire. The hot air leveling solder coating can completely cover the wire side edge, avoid the corrosion on the printed board broken wire, extend the printed board storage and use time, improve the reliability of the electronic products of the whole machine. Hot air leveling is now widely used in the SMT process.
(3) by adjusting the process parameters such as the Angle of the air cutter and the rate of rise of the printed plate, the coating thickness can be controlled to obtain the required solder coating thickness, which is more convenient and flexible than hot melting.
(4) printed plates produced by etching with graphic electroplating are easily bridged due to lead and tin alloy on the wire during wave soldering. In the same way, the flow of lead - tin alloy causes the resistance welding film to wrinkle and become warped. And with the hot air leveling process produced out of the printed plate, wire without solder, that is, the elimination of solder bridge, film wrinkle and fall off the phenomenon.

Hot air solder working principle:

Hot air leveling process is relatively simple, mainly: put the board (affixed with gold-plated plug protection tape) - hot air leveling before treatment - hot air leveling - hot air leveling after cleaning - inspection. Although the hot air leveling process is simple, but, in order to hot air leveling out a good quality PCB there are a lot of process conditions need to master, such as: solder temperature, air temperature, air blade pressure, dip time, speed, and so on. These conditions have set values, but work according to the printed circuit board external conditions and the requirements of the processing sheet phase change, such as: plate thickness, plate length. Different one - sided, two - sided, multi - layered boards. The conditions used by them are different, only familiar with the various process parameters, according to the printed circuit board of different types, different requirements, patience, careful, reasonable adjustment of the machine, hot air leveling out the qualified printed circuit board.

Hot air solder operation in the process of attention:

One, hot air flat suction tuyere drops residual liquid, this phenomenon is from the hot air level of the outlet downward flow of yellow liquid, this liquid is the main at ordinary times by the outlet suction flux. Over time within the convulsions pipeline, detoxify, shun convulsions around mouth dripping, dripping where all have, like a hot air pipe, the wind blade, wind drip edge protection cover most, sometimes, will also drop in work, the head of the operator work clothes, after closing work convulsions drop the most residual liquid, such as hot melt, the liquid on the equipment, the residual corrosion of the equipment over time. Can refer to the structure of the machine of the lampblack that take off, a funnel type wire on lot drainage residual liquid, can reduce or solve this kind of circumstance, can in the introduction of gutter or funnel net end into the liquid tank, ready to do so, the residual liquid in the process of flow down from lot, flows through the wire, there will be a large proportion of residual fluid flow along the wire. And do more than a few spare if the corrosion can be replaced.
Second, the hot air whole usually wear gloves, in the air the whole at ordinary times is usually USES the canvas gloves, a pair of mittens into another pay glove on the hand, slightly long flux went into gloves inside, and then gloves heat insulation ability is greatly reduced, and flux leaching opponents also has certain harm to the hand. The immersed in the flux of the gloves still can use it again after washing, but the result is bad, because the canvas soft, flux in very fast and the quantity is big, recommended jinsu gloves inside in a thin canvas gloves, the key issue is: the size of the rubber gloves to fit, better heat insulation, and good flexibility.
Three, flexible plate and finish milling shape rework PCB how hot air leveling, as a result of plank soft, flexible plate in the air the whole problems produced easily at ordinary times, need to be cautious, hot air leveling should milling with flexible board before the border around the edge is consistent, then in each frame and flexible plate edge several relative aperture, typically on each side frame to play three hole, edge width, length, can play a few more flexible plate hole to prevent hot air at ordinary times, due to low hole, fixed rickety and the flexible panel fold. Will bore frame with flexible plate edge one-to-one correspondence, with a fine copper wire through the hole to tie, tie after strong hot air leveling, should be paid attention to the usual will dip soldering time shorten, air knife pressure decreases, and milling rework on the shape of the board, milling of the borders, well put the board in a border, and then use leveling adhesive tape, adhesive tape with roller press flat surface, it can be hot air leveling after processing.

Iv. Reasons for clamping plates between guide rails:
1. The distance between the guide rail and the board is too close or too far, the adjustment of the guide rail can be solved.
2. Wall hole is not in the printed circuit board edge center, correct wall hole location can be solved.
3. Printed circuit board corner is not neat, add a border can be solved.
4. PCB rework edge hanging tin is too thick, the PCB by hand into the solder tank and then out.
5. Lead tin out of the guide is blocked too much to cause a card plate, can be melted away with hot solder, can be hard material out.
6. Hot air after the printed circuit board is hanging with rail? Top stuck in the middle of the deformation, timely replace the boom shock absorber.