Hand Soldering of Components with High Thermal Mass.
Hand soldering remains an indispensable technique in electronic manufacturing, despite the dominance of mass soldering processes such as convection oven reflow, vapor phase, and wave soldering. While these methods are highly efficient for high-volume production, they might not be suitable for all scenarios. A particular challenge arises when soldering components with a significantly larger thermal mass compared to others on the same substrate. In these instances, at PICA, we recommend a distinct approach, potentially involving a separate reflow process or hand soldering.
Hand soldering, though seemingly straightforward, demands meticulous control over the same critical elements as mass soldering to ensure the reliability of solder joints. At PICA, we emphasize the importance of the following elements:
1. Heat Source
- Reservoir soldering irons
- Constant tip temperature soldering irons
2. Heat Transfer Media
- The size and configuration of the soldering iron tip are crucial for effective heat transfer.
3. Cleaning Material (Flux)
- Options include: No Clean, RMA, OA, etc.
- The quantity of flux used is also vital.
4. Time to Achieve Soldering
- This is dependent on the operator and the point of contact between solder and iron tip.
At PICA, we advise that when hand soldering is necessitated by the large thermal mass of certain components, several key considerations and techniques must be considered:
Soldering Iron Selection: Components with high thermal mass require significant energy transfer to reach soldering temperatures. Irons with a large thermal mass may not be able to deliver the required amount of energy or might have inadequate recovery time during repeated uses. Conversely, irons that maintain a constant tip temperature can provide consistent heat regardless of the component size, making them more suitable for these tasks.
Tip Selection: The choice of tip is critical for efficient heat transfer. It should maximize contact area with the material for effective heat transfer while minimizing non-contact areas to reduce heat loss. An incorrect tip size can lead to inefficient heat transfer or increased soldering time, risking unreliable solder connections.
Cleaning Material Selection (Flux): The choice of flux is a balance between avoiding post-soldering cleaning and ensuring effective pre-soldering component cleaning. Flux serves to facilitate heat transfer and oxide removal, with the amount being determined by the flux channel size within the solder core. Insufficient flux can impair heat transfer and cleanliness.
Time to Achieve Soldering: Ensuring sufficient heating time is crucial, especially for components with high thermal mass. Unlike mass soldering processes, hand soldering time control is operator-dependent, introducing variability. The proper technique involves applying the soldering iron tip directly to the components and allowing the heat from the components themselves to melt the solder, ensuring accurate temperature attainment without "Transfer Soldering."
At PICA, we stress that understanding and controlling these aspects are crucial for successful hand soldering, especially when dealing with components of varying thermal masses.