surface mounting machines
Sixth, transport
Circuit board components are usually placed in high-speed mobile machine, the component has to do by the adhesion of the adhesive flux, if the board's move, start or pause Dongzuoguoda, the shift component is likely to cause further confusion, so transportation system in the process of conveying the circuit board, in three different regions must have an individual speed control unit.
In the first area, the system will be as much as possible to high-speed board transport to a predetermined location (usually in this part of the components previously stained by the solder paste to provide sufficient viscosity to meet the high-speed mobile) This area is mainly to flip (flip chip) to switch into the circuit board.
The second area (often referred to as assembly areas) will have to move at a slower speed, because flip-chip (flip chip) at this stage has been completed pcb assembly.
The third area (often referred to as out of area) is the circuit board component placement machine sent. Flux plays a very important role in this increased amount of flux will provide flip-chip (flip chip) greater adhesion, higher speeds can be transported on board, so can increase productivity, but also faced the some problems, which if not combined with cleaning system, the residual flux will cause flip-chip (flip chip) poor welding.
Seven board alignment
As the flip-chip (flip chip) used by the different substrate sizes, aligned on the circuit board can cause problems of varying degrees, some of the component placement machine of the substrate is vacuum (vacuum clamping) approach to fixed, This is the use of thinner substrate is quite questionable, thin substrates in the flatness requirement is more difficult to reach, though, while operating in a vacuum system, the substrate is quite flat, but after removal of the vacuum, the substrate will Reply original bent, the other, if the flux of the viscous component alone being fixed component, then the substrate will be very prone to moving components of the shift, although the board can add a hard way to strengthen the substrate, but As a vacuum system no longer has effect. Part of the vacuum system with a special system with each other, the relative price relative increase.
Eight adjustable pressure set pieces
Downward pressure on set pieces of the nozzle component placement machine is a very important parameter, in terms of need for the components under a sufficient pressure so that it can accurately placed in the solder pads, but not too large to make component solder pad from sliding open. General downward pressure on each bump(bump) 3 to 10g.
Nine, the visual system
Visual system components in flip chip placement machine in one of the most important element, in addition to the visual system to identify solder joints, but also the size of the component with the view to confirm the lessons of the component suction nozzle function correctly. Affect the quality of the vision system parameters magnification (gain), deviation (offset) and the critical value (threshold) and visual tools, with the most effective treatment will be small pitch components. When narrowing the distance between the components, the solder joints are forced to reduce the relative, for example, the spacing of 0.004 "component of the solder joints height of about 0.002", when the solder joints is reduced to very close to the chip, even if will magnify the image, identified as still quite difficult, because the chip surface protective layer (passivation) of the color and the color of solder joints is very close.
There is also a problem occurs in the substrate on the reference point (fiducial), due to flip-chip (flip chip) size is quite small, in some cases, some of the standard reference point than the chip actually big, to solve this problem , the visual system must control the search area (search).
Ten, the flux method
Flux in the assembly process in this very important and we hope that it will have sufficient viscosity, excellent wetting ability, and as much as possible to reduce residues, especially residues of the problem will be good or bad for welding impact, because if the flux residue in the primer filler (underfill) of the flow path, we would be detrimental to their attachment, so to compensate for CTE mismatch effect on the greatly reduced.
Usually in flip chip (flip chip) technology in flux on a number of approaches, including useful spraying (spray), using drip (drip), as well as with the dipping (dip).
In the assembly of components Qianjiang spray liquid flux to the nozzle atomizer spray the area you want to place the component.
Is the liquid flux drip drip components to be placed in the center of the area.
Dipping is the flux of liquid drops on the turntable, and then use blade control the thickness and flatness, followed by a suction nozzle from the component on the disc, dipping flux. In the low-speed component placement machine may consider this system, this turntable to make use of a fixed thickness of the flux system must pay special attention to pollution problems.
If the action is on the flux is separated into a process rather than another component placement machine with the same mechanism, such as the printing press to do this step, will greatly improve productivity.
XI component processing
The industry is how to deal with die (bare-die) there is no special standard components, generally used with waffle paks, gel paks, expended wafer systems, and surf tape and other methods. gel paks and expended wafer systems need to use an automated vacuum processing system, and waffle paks or waffle-paks trays is no need to use to vacuum, but rather the other way is more complicated. In addition, surf-tape system to use is called a fin-shaped feeding device (flipper feeder) equipment, this feed system and the traditional SMT process used to tape-and-reel feeder in appearance and function on a similar disadvantage in the component into the surf-tape is very difficult; if better designed pocket-size, in the future, a standard tape-and-reel will be more widely used.
All pcb assembly manufacturers have to provide basic material supply device (feeder), but the fin-like material supply device (flipper feeder) and the wafer material supply unit (expended wafer feeder) is part of choice with, expended wafer feeder is a kind of high / low compatibility components approach, this can be understood, because the complete disposal of the wafer is very difficult.
XII Conclusion
As the standard SMT process and flip chip (flip chip) assembly technology, and some shortcomings, mainly in the accuracy requirements, flip-chip (flip chip) technology is characterized by its size and spacing are quite small, in traditional SMT process component placement machine used may not Kanyong, precisely because of this, but also pushing the industry needs to further develop new technologies to extend the device's capabilities and features. In addition, the flux of process and materials are still many places not entirely perfect, it also depends on the industry to develop new methods and technologies to be in order with the flip-chip (flip chip) technology match. In this context we need equipment engineers developed the first step of the newer, more convenient facilities to promote the new type of process.