Surface Mount Technology (SMT) PCB Assembly Services in UK & Europe

At Rush PCB UK, we offer PCB assembly with surface mount technology. We use machines to pick and place the tiny surface-mount devices directly on the surface of the PCB. This way, we can attach and connect many types of electrical components to their respective contact pads using highly advanced reflow soldering technology.

With the shrinking form factor of electronic equipment, PCBs within the equipment must also reduce in size. Using the latest surface mount technology for assembling PCBs not only helps us to improve the component density, but also helps to add more functionality. The high level of automation involved in surface mount technology increases the quality while reducing manufacturing costs.

But surface mount technology comes with its own challenges. The major challenge is in choosing the most suitable production equipment. With our expertise spanning two decades, we, at Rush PCB UK, have set up a completely automated assembly line for producing printed circuit boards with surface mount components. Our experienced technicians have optimized the equipment to allow the entire assembly line to operate at the highest possible efficiencies.

The surface mount soldering process requires all surface mount components to be placed on the surface of the PCB. However, this is not enough, as the components must also be soldered to anchor them to the board. Therefore, the component pads must already have a deposit of solder paste before the components can be placed. For this, we use a solder paste stencil.

1. Solder Paste Stencil:

The solder paste stencil is a vital component in the surface mount soldering process. Its design must be such that it allows a precisely controlled amount of solder paste to be deposited onto the pad each time. We consider this to be a very important step to our quality, and we prepare our stencils from stainless steel. We use highly accurate laser cutting machines to cut and shape our stencils in-house. An additional advantage of handling our stencils in-house is that we can make improvements and modifications on the fly, thereby producing negligible time for delays and waiting. For higher throughput rates, we use an automated process for solder paste printing.

2. Automated Solder Paste Printing:

We use the latest printing machines for high-precision solder paste deposition. We also use automated loading and unloading of PCBs, which not only reduces handling but is also faster. While loading, an automatic camera takes care of the fiducial registration for precise alignment of the board, allowing accurate deposition of solder paste as a 25-micron layer. Between prints, an automatic arrangement cleans the excess solder paste below the stencil. This helps to reduce solder paste cross-contamination, which is a huge contributor to faults. Once the solder paste printing is completed, the board undergoes an automated optical inspection.

3. Automated Optical Inspection:

Before the placement of the surface mount components can begin, the solder paste deposit must undergo an automated optical inspection. A camera captures the 3D image of the solder paste deposition and checks the area covered and the height of each solder paste deposit.

4. Surface Mount Component Placement:

Most surface-mount devices are tiny components that do not possess lead wires or require holes for mounting on PCBs. Rather, they have flat metal pads or legs for facilitating soldering to similarly sized copper pads on the surface of the PCB. However, owing to their tiny size, the SMDs need very accurate placement at the exact centroid of the footprint on the board. This is done by a machine for SMD placement that also takes care of the proper rotation of the component. The machine places the component directly on the solder paste that has been screen printed earlier on the bare PCB.

Our placement machines have interchangeable feeders that allow us to assemble various types of small to medium, to large batches. As the feeders are interchangeable, we can move them rapidly between several machines and the stores, depending on the demands of the production schedules. An added advantage is that we can also set up the feeder carts offline, and not interrupt active SMD machines. This allows us to set matching reels and feeders of components in schedule with the SMD placement program. Once all components are placed, the board undergoes another AOI or automated optical inspection.

We use the latest AOI machines for inspection, and these consist of high-resolution 2D downward-looking cameras. This helps in mapping the surface of the assembly in 3 dimensions. For instance, the AOI machine can detect components with lifted legs, wrong rotation, missed components, and misplaced components.

5. Reflow Soldering:

We use two types of reflow soldering methods — multi-section hot air convection or vapor phase reflow.

Our hot air convection reflow machines use a conveyorized process where the boards with solder paste and components mounted thereon pass sequentially through multiple sections with increasing temperatures until the solder paste melts. The boards then pass through a cooling section, where the molten solder paste cools, bonding and anchoring the components to the board. We use hot air convection reflow machines for soldering medium batch sizes. The machines require careful selection and monitoring of temperature profiles with calibrated monitoring equipment.

Vapor phase reflow is a batch process and is more suitable for some electronic assemblies. The advantage of the process is that it is extremely tolerant of assemblies consisting of components with large thermal masses, such as heat sinks. The process window is wider and more suitable for larger production batch sizes.

6. SMD Inspection:

The reflow soldering process is followed by another round of automated optical inspection. These offline inspection workstations help to detect missing, misaligned, and wrongly placed components, along with solder shorts.

For assemblies consisting of BGAs and other components with solder joints beneath and hidden under their bodies, we inspect the soldering quality using automated high-resolution X-ray machines.

7. Electrical Testing:

We use PCB electrical testing as a critical quality control measure. We conduct a series of tests to verify the electrical functionality and integrity of the PCB assembly. The ultimate aim of the tests is to identify defects such as shorts, opens, and other issues that could compromise the board’s reliability or performance.

If you are looking for high-quality, cost-effective PCB assemblies using surface-mount technology, Rush PCB UK is here to provide full support. Call us today and start converting your designs to the latest printed circuit boards.

Surface mount technology (SMT) and through-hole technology (THT) are two primary PCB assembly methods. SMT allows components to be mounted directly onto the board surface, enabling higher density and compact designs. Through-hole assembly involves inserting component leads into drilled holes, offering stronger mechanical bonding. SMT is ideal for modern, high-speed electronics, while through-hole is preferred for heavy-duty applications. We also support a hybrid PCB populations that combine both methods.

Struggling with PCB assembly quality or rising costs? Rush PCB UK delivers precision, speed, and reliability with advanced SMT technology. From prototypes to high-volume runs, we ensure cost efficiency and unmatched performance. Let’s turn your designs into reality. Request your quote today and bring your PCB designs to life.