PCBNet.com – PCB Assembly 101

PCB AssemblyIn a PCB assembly and production process, there are various stages that you need to follow. It’s necessary for all these stages to work together to establish an integrated operation. Each stage must correspond with the next, and a feedback from output to input must be observed to maintain optimal quality all throughout the process. This way, problems can be detected promptly and the process can be amended accordingly.

As your most reliable source of top quality and on-time PCBs, PCBNet.com uses equipment of the highest caliber to assemble the boards. We use unique tools and special applications to accommodate today’s more challenging board requirements, and feature a Full TurnKey online system so that our customers can get their PCB quotes quickly, typically within the same day.

PCB Assembly Overview

The process of PCB assembly involves several stages including solder application, pick and place, soldering, inspection/QA and testing. Each of these processes is required and needs to be closely monitored to guarantee that the finished products are of the highest quality.

Solder Paste Application

Before attaching the components to the board, solder paste should be added to the areas where soldering is needed. These areas are usually the pads of the components. Solder paste application is accomplished with the aid of a soldering screen.

The solder paste is a mixture of tiny grains and flux. This paste can be dispensed onto the proper areas using a method similar to a printing process. Place the screen directly on the board and position it in its proper place. Move the runner across the soldering screen while squeezing small amounts of paste through its holes and onto the PCB.

Since the screen has been created from the PCB files, it already has built-in holes on the locations of the pads. By depositing the paste through the holes, you can, thus, deposit it onto the solder pads.

At PCBNet.com, we use a special tool to apply the solder paste. Instead of using a standard screen in printing or dispensing, we use a jetting technology, which allows the buildup of paste by small single dots to attain the correct amount for each pad.

Pick and Place

After applying the solder, the board is then transferred to the pick and place station. This area has a machine filled with component reels. This machine picks up the components and places them on their proper position on the PCB. The tension of the paste holds the components in place once they are placed on the board.

If the board needs to be wave-soldered, the pick and place equipment adds a small amount of glue to fasten the components on its surface. Since glue is present in this type of method, it is more difficult to repair, in case it’s necessary.


After the components are attached to the PCB, the next step is to pass the board through a wave-soldering machine. If wave-soldering is used, the application of solder paste is not necessary since the wave-soldering machine already provides the paste. This process, however, is not commonly used for SMT components but rather, reflow soldering methods are used by most PCB manufacturers these days.

Inspection / QA

After accomplishing the soldering process, the boards are then subjected for inspection. SMT boards with hundreds of components are not manually inspected. Instead, they are inspected by means of an automatic optical inspection machine, which provides a more practical resolution.

PCBNet.com uses state-of-the-art inspection machines that can thoroughly inspect each PCB and detect flaws, such as poor joints and wrong or misplaced components.


pcbnetIt is always necessary for the PCBs to go through the testing stage before taking them out to the factory for delivery. There are various methods that you can use in testing the boards. This usually includes a functional test wherein signals and power are delivered to simulate the operation of the electronic device where the board is to be used.

This test will measure the board’s electrical characteristics including current, voltage and signal output that are compared with a reasonable range to decide whether it passes or not. Once the PCB passes the functional test, it is either packaged for shipment or assembled into the finished product.


To ensure that the assembly/production process operates satisfactorily, the outputs should be minutely monitored. Any detected failure must be investigated immediately as soon as the boards are in the inspection stage which comes right after the soldering process. Through this, flaws and defects are detected instantly and amended before many other boards are produced with the same issue.


The PCB assembly process is largely optimized to reduce the occurrence of board defects. This way, the highest quality is ensured for each product. We, at PCBNet.com, understand that there are more challenges and demands in today’s PCB products, and that the assembly/production process is crucial to the success of the overall operation. Thus, we always employ the most reliable tools, equipment and staff to ensure we deliver quality and on-time products to all our customers.