How Does SMT Work?

Surface mount technology is the widely-used alternative to through-hole printed circuit board designand manufacturing practices. Today an increasing majority of PCB devices are available as SMDs or packages, making the adoption of SMT board designs and manufacturing practical and cost-effective.

In a simplified view of SMT manufacturing, fabrication generally consists of several highly-automated processes:

Board material contains solder pads without holes, to which solder paste is applied with a screen-printing-like process. Solder placement can be controlled through the use of a precise stencil template for the individual PCB being fabricated, to apply the material only where needed.

Automated component picking and placement machines then position the desired SMDs and other components on the boards precisely. Boards then continue to soldering operations which heat the solder pads to the point where the applied solder paste melts and bonds the components to the board.

Where heat-sensitive components are incorporated on the PCB, these may be installed after the automated soldering, either manually or through processes that would not damage the component. Boards are subsequently “washed” to remove excess flux or solder residues that could cause shorting of components due to their extremely close placement tolerance.

After that is the final inspection of quality including missing components, alignment issues, or soldering issues that could generate potential problems. Inspections of SMT boards can also be automated. Equipment is available that retains a visual image of the correct board construction, and compares the boards produced to the reference image. 

Electronic Board Types

The term for an electronic board is a circuit board. There are three main types of circuit boards: printed circuit boards, stripboards and breadboards.

A printed circuit board functions by connecting various electronic parts in an electric device and providing them with mechanical support. It does this through conductive tracks, pads and laminated copper components. The printed circuit board is the most popular type of electronic board, and it can be found in most common electronic devices, including cell phones, radios and televisions.

A stripboard circuit contains a grid of holes bored into a plastic board and aligned copper strips on the other side of the board plastic. Circuit connections created on a stripboard are permanent. To create a system of connections on the board, the engineer therefore needs to manually solder in the copper strips that form the circuit. Stripboards are more ideal for smaller electronic connection needs.

A breadboard is a perforated plastic board with layers of metal alloy clips underneath the perforated plastic. It is quick and simple to construct. Unlike a stripboard, it is reusable, as a breadboard circuit can be adjusted by linking wires and leads to different holes each time a new circuit system is required.

Tips for Cleaning Dust

If you notice that your circuit board is collecting dust or grime that keeps it from functioning normally, you may decide to clean the board when you take into consideration the money and time you will spend on purchasing a new one. 

There are different methods for cleaning printed circuit boards depending on the type of PCB you have and what dirt or buildup exists. Before you begin to clean your PCB, be aware that any time you do so you run the risk of causing damage to the board and components. Therefore, if the board works normally but is just a bit dusty you must decide if attempting to clean the PCB is worth the risk. For PCBs with only light dust, use an old dry toothbrush, dry paintbrush or the upholstery brush from your vacuum to loosen the dust. Then you can use a can of compressed air to blow the remainder of dust off of the board.

The cleaning process becomes a bit trickier if you have grime on your printed circuit boards. Grime is common with monitor chassis boards that deal with higher temperatures and melting wax from components. Be sure to remove any socketed components before applying detergent and scrubbing mildly to loosen whatever is caked onto your PCB. Since this method may not work 100 percent of the time, it is a good idea to consult a PCB expert to see what you can potentially do to clean your circuit board and get it back into working order. If it cannot be fixed, you will need to place an order for a new board. 

Recover Printed Circuit Boards

When an electronic device is recycled, it is broken down into its simplest parts so that printed circuit boards and valuable metals can be recovered. The research found that there are four key techniques used in the UK for the recovery of PCBs: 
Fully manual segregation – segregation of target items from other WEEE streams, followed by manual dismantling of equipment; 
Fully manual segregation, including re-use -– as above but incorporates the recovery of specific PCBs/processor chips for re-use; 
Semi-automated with commercial shredding – Mechanical shredding of WEEE for size reduction and separation of saleable ferrous and non-ferrous metals, with manual downstream picking operations to recover PCBs and other components. This process is best suited for recovering PCBs from items which are not cost effective to manually sort or items where the PCBs are physically attached, e.g. welded, and cannot be manually removed; 
Semi-automated with commercial smashing – manual removal of streams requiring manual recovery. Spinning and smashing of the remaining WEEE into smaller components followed by magnetic separation; and finally manual picking lines.

Test PCBs during Production

It is absolutely important that the printed circuit boards you received are exactly in accordance with the specification you required and work as you expected. After performing the shorts and opens test at EPCB, the in-circuit tester tests each component on a PCB assembly one at a time. This way, you are promised to get your printed circuit boards that are totally ready to be used as you needed. During the testing process, programs will be loaded onto test machines to check for any issues. EPCB tests 100 percent of the networks on your circuit board for continuity and isolation. You can get more information about the production process by talking with an EPCB representative.