How does double-sided SMT assembly work

What SMT assembly is

SMT assembly stands for Surface Mount Technology assembly and it is classified as a type of soldering technology that employs the use of the reflow soldering technology or any other defined process to mount electronic components on a printed circuit board. Unlike traditional through-hole technology, SMT does not require drilling holes into the PCB. Instead, components are mounted directly onto the surface of the board, enabling more compact and efficient designs. This method is highly favored in modern electronics due to its ability to support high-density component placement and automated production.

SMT assembly by PCBAStore

As the most popular PCB manufacturing and assembly company based in China, we have been offering full spec electronic manufacturing solutions for 16 years to meeting the needs of our customers from different industries in terms of cost-effectiveness, quality , delivery and any other requests. PCBAStore provides comprehensive services including PCB design, layout, prototyping, mass fabrication, and box-build assembly. Their advanced SMT workshop features Panasonic high-speed placement machines and reflow ovens capable of handling both single-sided and double-sided SMT assemblies with precision.

Defining double-sided SMT

This is a process that makes use of double-sided PCBs. One side of the board will have a major IC chip while the other side will be composed of IC components. The design process is somehow complex since it also involves the use of complex components. A double-sided PCB includes conductive layers on both top and bottom surfaces, allowing for more circuitry in a smaller footprint. This makes it ideal for applications where space is limited but functionality needs are high.

SMT Assembly Process

Dispensing

Since the type of board that is generally used in this process is the double-sided printed circuit board, to prevent the components that were soldered on the input side of the board from undergoing melting and re-sold off because of remelting of the solder mask, it is advised that a dispenser is installed at the input surface. A water droplet at the input of the printed circuit board is employed to fix the electronic components to the board.

Component placement

The purpose of this process is to make sure that the surface mount components are accurately fixed at the exact required position on the printed circuit board. A Pick&Place machine is used to ensure that the process is achieved.

Curing

This one is used to aid in melting the patch glue and this helps to ensure that the components and the printed circuit board are strongly bonded together. The curing oven is the special equipment used in the process and it is located behind the machine for placement in the surface mount technology assembly line.

Reflow soldering

This does the melting of the solder paste so that to ensure that the SMT components and the printed circuit boards are bonded together. The reflow soldering furnace is the equipment that makes this possible and you will find it behind the placement machine in the production line.

Cleaning

This is the process where the harmful soldering residues such as flux are removed from SMT assembled printed circuit boards.

Inspection

Here, welded board assembly quality is put to test to ensure that whatever was done is correct and of great quality. Tools like AOI (Automated Optical Inspection), microscopes, flying probe testers, or online testers are employed.

Rework

Here, we involve PCBs that have a failure detected. The PCB is reworked to remove failure. The tools involved are soldering irons and it is configured along production line at desired position.

Double-sided SMT Assembly

The double-sided SMT assembly process is almost similar to general assembly process but only a few steps will be added. The following steps are involved.

Incoming Inspection

Here inspection of assembly files is done to ensure they are to standards of designer.

Screen solder paste printing on PCB side A

Side A is first side to be printed. The process on side A is done similarly to what’s done while doing single-sided SMT assembly.

Surface Mounting

Standard pick-and-place machines mount all designated components onto Side A.

Drying

Drying solidifies adhesives or paste before heat treatment.

Reflow soldering on Side A

Reflow oven melts solder paste securing all Side A components permanently.

Clean out

Residue from flux or contaminants removed using specialized washing systems.

Plate turnover

The turnover is special to allow printing of side B of double-sided PCB.

Dispensing adhesive on Side B

Surface mount adhesive applied precisely where needed before placing parts.

Surface mounting

Components placed onto adhesive-coated areas using pick-and-place systems.

Drying

Adhesives cured again before final heat treatment step.

Wave soldering Side B

Here wave soldering preferred as compared to reflow soldering because it will protect printed side A from remelting.

Cleaning out

Thorough cleaning ensures removal of flux residues post-soldering.

VI & AOI

This is where inspection for quality done to make sure design has no defects.

Reworking

Defective units undergo manual correction using precision tools.

Summary

Double-sided SMT assembly is a very necessary process when it comes to assembling PCBs with more than one layer. Mostly used when top and bottom layers of PCB are to be printed. The process and machines used in process have been highlighted. The additional complexity allows engineers greater freedom in design while optimizing space utilization — critical for advanced electronics applications such as IoT devices, automotive modules, telecommunications hardware, and medical instruments.

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