Raspberry Pi boards incorporate both surface-mount devices (SMDs) and through-hole bits, making soldering a unique challenge for enthusiasts. The combination of tiny chips, resistors, and larger components requires a dual-approach, with SMDs attached via pins, flat contacts, or solder balls, and bigger parts requiring through-hole soldering.
For components subject to rough handling, like those in ports like Ethernet and USB, robust solder joints are necessary. Initially, Raspberry Pi boards relied on manual or robotic placement of these larger components, followed by wave soldering. However, with the introduction of reflow soldering, both tiny SMDs and bigger parts are now soldered simultaneously.
This process involves adjusting component placement, solder stencil design, and connectors before placing all components in a single stage. By partnering with Sony for UK manufacturing, Raspberry Pi has streamlined this complex process, ensuring efficient production of its popular boards.
Source: https://arstechnica.com/gadgets/2025/04/raspberry-pi-cuts-product-returns-by-50-by-changing-up-its-pin-soldering