SMT (surface mount technology) component placement systems, commonly called pick-and-place machines or P&Ps, are robotic machines which are used to place surface-mount devices (SMDs) onto a printed circuit board (PCB). They are used for high speed, high precision placing of broad range of electronic components, like capacitors, resistors, integrated circuits onto the PCBs which are in turn used in computers, consumer electronics as well as industrial, medical, automotive, military and telecommunications equipment.(Wikipedia)
The placement equipment is part of a larger overall machine that carries out specific programmed steps to create a PCB Assembly. Several sub-systems work together to pick up and correctly place the components onto the PCB. These systems normally use pneumatic suction cups, attached to a plotter-like device to allow the cup to be accurately manipulated in three dimensions. Additionally, each nozzle can be rotated independently. .(Wikipedia)
Surface mount components are placed along the front (and often back) faces of the machine. Most components are supplied on paper or plastic tape, in tape reels that are loaded onto feeders mounted to the machine. Larger integrated circuits (ICs) are sometimes supplied arranged in trays which are stacked in a compartment. More commonly ICs will be provided in tapes rather than trays or sticks. Improvements in feeder technology mean that tape format is becoming the preferred method of presenting parts on an SMT machine. .(Wikipedia)
Through the middle of the machine there is a conveyor belt, along which blank PCBs travel, and a PCB clamp in the center of the machine. The PCB is clamped, and the nozzles pick up individual components from the feeders/trays, rotate them to the correct orientation and then place them on the appropriate pads on the PCB with high precision.High end machines can have multiple conveyors to produce multiple same or different kind of products simultaneously. .(Wikipedia)
As the part is carried from the part feeders on either side of the conveyor belt to the PCB, it is photographed from below. Its silhouette is inspected to see if it is damaged or missing (was not picked up), and the inevitable registration errors in pickup are measured and compensated for when the part is placed. For example, if the part was shifted 0.25 mm and rotated 10° when picked up, the pickup head will adjust the placement position to place the part in the correct location. Some machines have these optical systems on the robot arm and can carry out the optical calculations without losing time, thereby achieving a lower derating factor. The high end optical systems mounted on the heads can also be used to capture details of the non-standard type components and save them to a database for future use. In addition to this, advanced software is available for monitoring the production and interconnect database — of the production floor to that of supply chain — in real time.
A separate camera on the pick-and-place head photographs fiducial marks on the PCB to measure its position on the conveyor belt accurately. Two fiducial marks, measured in two dimensions each, usually placed diagonally, let the PCB’s orientation and thermal expansion be measured and compensated for as well. Some machines are also able to measure the PCB shear by measuring a third fiducial mark on the PCB. .(Wikipedia)
To minimize the distance the pickup gantry must travel, it is common to have multiple nozzles with separate vertical motion on a single gantry. This can pick up multiple parts with one trip to the feeders. Also, advanced software in the newer generation machines allows different robotic heads to work independently of each other to further increase the throughput. .(Wikipedia)
The components may be temporarily adhered to the PCB using the wet solder paste itself, or by using small blobs of a separate adhesive, applied by a glue-dispensing machine. (Wikipedia)
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Best things about qualified PCB board assembly
In case you are planning on undertaking the PCB board assembly in-house at a professional level you’re easily going to see the first investment cost is really large. You will require not less than: one pick and place equipment, one stencil printing machine and one reflow oven. Maybe you likewise want other relevant equipment for examination work and hand soldering tools. You’ll need labourforce and expertise that can elevate the investment cost significantly. And lastly when you consider there is little ROI from this kind of financial commitment you will definitely swiftly choose to delegate the PCB board assembly service. Almost always outsourcing the PCB board assembly work to an outward corporation ought to be more cost effective.
Then there is the element of quality; a corporation focused on PCB board assembly services should have the knowledge and manpower to provide excellent quality. They will also spend money on their development by continually having the latest technology making sure that the purchaser gets all the advantages of the new assembly technologies. It’s likely that you’ll hit a equipment related issue doing in-house assembly if you can’t up-grade the devices often, as an example, you might end-up in a situation in which you are not able to effectively assembly the latest BGA package for a emerging processor.
Another possibility is the element of quality control. An established PCB board assembly plant can also get a very good founded quality control service that you can gain from by not being forced to do the quality control in-house. Obviously, you would like to do a supplementary quality control step in-house but it is great to know at any rate the pcb’s are all functioning properly when they get away from the assembly plant.
Disadvantages of specialized PCB board assembly
One good reason you wouldn’t want to outsource the assembly of your project is to provide protection to intellectual property. If you’re doing some mystery project or the most up-to-date concept that will revolutionize something, you have to keep that as confidential as possible so in that case you may do the PCB board assembly in house.
Also, there are cases when the turnaround time of a prototype is critical so you may not afford to wait one week for your PCB board to send back from a specialized assembly line. Well then it might be preferable to do the assembly in house.
Expenditure is furthermore an essential cause you will possibly not wish to go with a professional PCB board assembly plant, particularly for small establishments or amateurs. Prices for PCB board assembly services have dropped substantially during the past several years and so it’s less of an issue these days but nonetheless you’ll not see tons of people sending their one-time hobby projects to a PCB board assembly plant.