Hot air leveling, also known as spray tin, it works by using hot air to remove excess solder on the surface and hole of the printed board, and the remaining solder evenly covered on the solder pad, unblocked solder lines and surface sealing decoration.
The technology of hot air leveling is relatively simple, mainly including: put plate (with gold-plated plug protective tape), pretreatment before hot air leveling, hot air leveling, cleaning after hot air leveling and inspection.Although the process of hot air leveling is simple, there are still a lot of technological conditions to master if you want to make a good and qualified printed board by hot air leveling, such as solder temperature, air knife air temperature, air knife pressure, dip welding time, lifting speed, etc.These conditions have set values, but work according to the external conditions of the printed board and the requirements of the processing sheet phase change, such as: plate thickness, plate length different single side, double side, multi-layer board.The conditions adopted are different. Only by being familiar with various process parameters, patient, careful and reasonable adjustment of the machine according to different types and requirements of the printed boards, can the hot air level out qualified printed boards.The following common problems often occur in hot air leveling and some solutions are proposed based on work experience for reference only.
A.Hot air leveling exhaust vents to drop residual liquid, this phenomenon is from hot air leveling vent downward dripping yellow liquid, this liquid is mainly the welding flux that is inhaled by the vent at ordinary times.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 make a few more backup if corrode bad can replace.
2.Hot air is usually used in the ordinary gloves, during hot air is usually used canvas gloves, one set of gloves into another set of gloves on the hand for work, the time is a little longer the flux is immersed in the gloves, at this time the heat insulation of the gloves is greatly reduced, and, the flux dipped into the hand opponent also has a certain harm.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.
3.Flexible board 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 of flexible plate can play a few more holes.
Four.Reasons for clamping between guide rails:
1.If the distance between the guide and the board is too close or too far, it can be solved by adjusting the guide.
2.The plate hole is not in the center of the plate edge, the correct position of the plate hole can be solved.
3.Printing plate edge Angle not regular, add frame can be solved.
4.Tin is too thick at the edge of the board for reworking. Insert the board into the solder pot by hand and take it out.
5.Lead tin hole of guide is blocked too much cause board, can use hot solder to melt, can use hard object to top out.
6.After hot air leveling the PCB is hung and guide rail?Top stuck in the middle of the deformation, timely replacement of the hanging arm shock absorber.