Steps in a mixed assembly

PCB mixed assembly is a long process, involving several automatic and manual steps. Each of these steps must be performed correctly by paying maximum attention to detail. Small errors in any step of the mixed assembly process will lead to the failure of the final assembly. Before the actual assembly process, the manufacturer should thoroughly check the PCB design file to check its function and manufacturability. This phase called DFM, checks the PCB assembly design specifications while analyzing any missing, redundant, or potentially problematic features. This phase helps to detect design errors and allows designers to remove all defects immediately, leading to successful production.

Here are seven steps of the PCB mixed assembly process: application of solder paste, placement of components, counter-flow, inspection, through hole element insertion, final inspection, cleaning.

Step 1: First, solder paste (a small particle of solder paste mixed with flux) is applied to the board. For this application, most PCB manufacturers use templates (there are several sizes, shapes, and specifications that match the specifications), which can only correctly apply the correct amount of solder paste to certain parts of the board.

Step 2: Unlike in the past, the PCB assembly process at this stage is now fully automated. Picking and placing of parts (such as surface mount components) used to be done manually, but now is performed by robot picking and placing machine. These machines place components accurately in the preplanned area of the circuit board.

Step 3: Now, solder paste and all surface mounting components are in place. What are you going to do next? Curing solder paste to the correct specification is essential for the correct adhesion of PCB components to it. This is a related part of PCB assembly - reflow welding. To do this, pass the assembly with solder paste and the components on it through the conveyor belt through the industrial reflux furnace. The heater in the oven melts the solder in the solder paste. Once melting is complete, the components will move again in the conveyor belt and exposed to a series of cooler heaters. The purpose of these coolers is to cool the molten solder and solidify it.

Step 4: After the reflow process, the PCB should be checked to check its function. This stage helps to identify poor quality connections, misplaced components and short circuits due to the continuous movement of the circuit board during the reflow process.

Step 5: Some types of PCBs need to insert through-hole components together with conventional SMT components. This phase is dedicated to the insertion of such components. For this purpose, which PCB components are used to transmit signals from one side of the board to the other side to create plated through holes. PCB through-hole insertion is usually achieved by manual or wave soldering.

Step 6: It's time for the second level of inspection. Here, function test the assembled board, or thoroughly inspect the PCB to monitor its electrical characteristics, including voltage, current or signal output. Today's manufacturers use a variety of advanced testing equipment to help determine the success or failure of the finished board.

Step 7: Since the soldering process leaves a large amount of flux residue in the PCB, it is essential to thoroughly clean the components before delivering the final circuit board to the customer. For this purpose, PCBs are cleaned in deionized water.

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