Provided certain specifications are followed, surface-mount technology (SMT) is straightforward to use.

The solder lug, solder pad, and solder paste must be properly matched to produce a solder joint that complies with the IPC-A-610 standard. IPC-A-610 has now become the global standard, which is why connector manufacturers are also required to design their products in accordance with it to optimize product quality and reliability. For example, the new Zero8 SMT connector from ept is designed to meet the highest Class 3 requirements according to IPC-A-610 Edition G, taking tolerance chaining into account. IPC Class 3 is reserved for high-performance electronics where failures must be ruled out. Products classified in this category must consistently ensure high performance and operational reliability, as well as enable uninterrupted power delivery.

In conjunction with optimal wetting, only enough solder should be used at the solder joint to ensure that the contours of the component terminals remain visible. The angle between a drop of liquid solder and the base material is called the contact angle; this must not exceed 90°. The solder joint surface must be concave and have a flat, tapered edge at the terminal to be soldered. The maximum tip overhang and side overhang must be selected so that the minimum electrical clearance is not compromised. For side overhangs, care must also be taken to ensure that the overhang does not exceed 25% of the terminal width. The length of the formed foot, the terminal thickness, and the terminal width depend on the component design.

The solder at the heel should extend beyond the thickness of the terminal, reaching at least to the center of the outer bend and at most to the upper terminal bend. The terminal bend should not be filled with solder, and the solder should not touch the component body. The minimum width at the end of the solder joint must be 75% of the terminal width. The minimum length of the solder joint on the side should correspond to the foot length (if foot length < 3 × terminal width), or be equal to or greater than three terminal widths (if foot length > 3 × terminal width). The volume, surface tension of the solder, and size of the wettable area are decisive for the shape of the meniscus.

In addition, the surfaces should be connected to one another in a tangential curve. It is this concave formation that is referred to as the meniscus. With regard to the cleanliness of the solder joint, there must be no solder residue outside the joint, and the joint itself must be clean and uniform.

However, errors can always occur during placement by the placement machine or during the subsequent soldering process. These manifest, for example, as missing or incorrectly placed components.

Other errors can include rotated or misaligned components, unsoldered or inadequately soldered component leads (pins), or short circuits and contaminants between the pins. This is where automatic optical inspection (AOI) comes into play. It is used to inspect blank circuit boards, ceramic substrates, solder paste printing, assembly processes, and to monitor the soldering process.

SMT connectors developed by ept not only feature the optimal contact geometry for reliable soldering but are also suitable for automatic optical inspection.