Risk Mitigation in Hand Soldering

Robert Roush
OK International/Metcal

Soldering is the bonding of metallic surfaces via an intermetallic compound (IMC). The interaction between thermal energy delivery, flux chemistry, and solder chemistry creates the solder bond or joint. Today, reliability relies on visual inspection, operator experience and skill, control of influencers e.g. tip geometry, tip temperature, and collection and analysis of process data. Each factor involved with the formation of the solder joint is an element of risk and can affect either throughput or repeatability. Mitigating this risk in hand soldering requires the identification of these factors and a means to address them. A new technology, which evaluates the quality of the solder joint by calculating the intermetallic compound formation and provides closed loop feedback to the operator, changes the way solder joints are evaluated in hand soldering.

Validation of the solder joint requires the ability to identify the correct solder geometry, detect the transition of solder from solid to liquid, and calculate the intermetallic compound formation without adversely impacting throughput or repeatability. Additionally, to be effective, this validation of the solder connection provides real time feedback to the operator and prompts action based on the response. Implementation of this new technology represents a paradigm shift in the hand soldering industry changing the reliance on visual inspection to control of the formation of the intermetallic compound. The validation technology requires two components, software and hardware. The software component is an algorithm that executes the three-step process to calculate the intermetallic compound.

The hardware component incorporates a system to store data at the point of use, process the calculations locally and provide feedback to the operator via a visual go/no-go indicator. The validation technology in concert with visual inspection represents a change to the status quo in hand soldering.

Each factor involved with the formation of the solder joint is an element of risk and can affect throughput and repeatability. The industry relies on control of input variables and operator training to minimize risk to varying degrees of success. Intermetallic compound calculation compliments the visual inspection criteria with a tool that introduces repeatability into the process in real time. With the proper software and hardware modifications, IMC calculation provides a repeatable process that minimizes the variables associated with operator skill and individual assessment pertaining to the formation of a successful solder joint.