Pin in Paste with Solder Preforms - Intrusive Reflow

Pin in Paste (PiP) with solder preforms, also known as Intrusive Reflow or Intrusive Soldering, is an advanced soldering technique used in electronics manufacturing to join through-hole components to a printed circuit board (PCB) that primarily uses surface mount technology (SMT) components. This method allows for the combination of both through-hole and SMT components on the same PCB while taking advantage of the benefits of reflow soldering. Here's how the process works:
Component Selection: Through-hole components are selected for the PCB assembly, alongside surface-mount components. Through-hole components have leads that are intended to be inserted into holes in the PCB.
Solder Preforms: Instead of using traditional through-hole soldering methods like wave soldering or hand soldering, which involve applying solder flux and heating from below the PCB, solder preforms are used. Solder preforms are small, precisely shaped pieces of solder that are designed to fit around the through-hole component leads. These preforms are placed on the PCB before inserting the through-hole components.
Component Insertion: The through-hole components are inserted into their designated holes on the PCB. The solder preforms surround the leads of these components.
Reflow Soldering: The PCB, with both surface-mount and through-hole components in place, is subjected to a reflow soldering process. The reflow oven heats the entire assembly, causing the solder preforms to melt and flow, creating solder joints around the through-hole component leads. At the same time, the surface-mount components are reflow soldered, if they weren't already soldered earlier in the SMT assembly process.
Cooling and Solidification: After the solder has melted and created reliable solder joints, the PCB is gradually cooled to solidify the solder. This controlled cooling phase is essential to prevent thermal stress and ensure the quality of solder joints.
Inspection and Testing: As with any soldering process, the assembly undergoes visual inspection and testing to check for solder defects, such as insufficient solder, solder bridges, or cold solder joints.
Benefits of Pin in Paste with Solder Preforms (Intrusive Reflow):
Mixed Technology PCBs: This technique allows for the integration of through-hole and SMT components on the same PCB, making it suitable for designs that require both technologies.
Improved Thermal Performance: Intrusive reflow can provide better thermal and electrical performance compared to traditional wave soldering because it reduces the thermal stress on the components.
Reduced Solder Consumption: Solder preforms are precise, so they help minimize solder waste.
Lower Defect Rates: The reflow process offers better control over soldering parameters, leading to fewer defects.
Higher Automation: Intrusive reflow can be more automated and is compatible with modern SMT assembly lines.
However, this technique requires careful design considerations for the size and shape of solder preforms, and the process parameters must be well-controlled to achieve high-quality solder joints for both through-hole and SMT components.