Key Considerations for Selecting Solder Paste for Rigid-Flex PCBs

Selecting Solder Paste for Rigid-Flex PCBs

The solder paste used to connect metal parts on a circuit board is made from a melted alloy of Sn (tin), Ag (silver), and Cu (copper). The solder wetting ability of the molten alloy can affect the quality of the PCB. A good wetting action allows the molten metal to bond with the surface of the copper pads on a PCB. It also prevents the formation of high edges around the deposits, known as “dog ears”.

Solder paste can be purchased in large quantities for industrial production. However, it is also available in more minor qualities, such as tubs and syringes, which are useful for pcb rigid flex rework or limited production runs such as a prototype assembly. Solder paste must be stored correctly to prevent oxidation, which will reduce its wetting ability and lead to poor connections. It should be kept at a temperature between 25 and 35°C, in a sealed container to protect it from moisture. It must also be protected from shocks, vibrations, and extreme temperatures.

A Printed Circuit Board’s assembly process can have a major impact on its cost and manufacturability. The number and size of drilled holes, the complexity of routing, and the amount of via plugging can all increase manufacturing costs. The choice of materials, such as FR4 or polyimide, also influences cost and can affect the board’s mechanical durability.

Key Considerations for Selecting Solder Paste for Rigid-Flex PCBs

To control manufacturing costs, a designer can minimize the use of tight traces and spaces and choose more common panel sizes. This can save money as the board will require less labor and specialized tools. A designer can also use a padstack tool to optimize the placement of components. This can avoid excessively overlapping pads, which will cause shorting between them and increase assembly time and defects.

The choice of materials for the rigid and flex sections of a PCB is also an important consideration. These must be compatible to ensure a good connection between the two sections and avoid stress from mechanical bending or flexing. It is also critical to ensure that the rigid and flex sections have similar coefficients of thermal expansion, to avoid warping or delamination during fabrication.

Rigid-flex PCBs are used in a wide range of applications, including consumer electronics and automotive components. They are found in electronic control units, TVs remote controllers, washing machines, solar power systems, and lighting systems. They are also used in telecommunications equipment, such as base stations, handheld units, wireless communication systems, and signal processing systems.

They are also used in medical and military equipment. Rigid flex is also an excellent choice for vehicles, such as electric scooters and wheelchairs, laptop computers, tablets, mobile phones, and navigation systems. Rigid flex is especially important in the automotive industry, where it is used to control power transmission and to monitor air conditioning, entertainment, music, and navigation systems.