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July, 2020

Improving Throughput and Yields with the Right Hand Soldering System

By Curtis Yamauchi, Product Manager, Metcal T

he excellence of a solder joint, and ultimate- ly, the success of the final product, relies heavily on the skills and experience of the

operator. This is true for delicate individual com- ponents or when manually reworking boards once they are flagged by QA. Getting the most out of an operator’s skills

and experience — joint after joint, board after board, and shift after shift — requires providing each operator with the most effective and efficient soldering system possible for the specific needs of the operation. Although one single type of technology

accounts for most of the soldering systems in use today, this category is diverse. There are several alternatives and a number of strategic decisions that can be made to improve throughput and yields. The current range of soldering systems on the

market consists of inductive or resistive heating technologies, with temperature set points either fixed or adjustable. While resistive adjustable technology is the

most commonly offered, and therefore often the default choice, two other types — fixed inductive and new adjustable inductive technology — have many potential benefits. Add to that a slew of other choices, including

cartridges or tips, relative device size, numbers of ports, and so on, and it is easy to see how investing a little time considering the options up front can pay huge dividends for years to come.

Key Factors For most operations, throughput and yield

are the key criteria for soldering performance. GT90 inductive-heating

adjustable-temperature soldering system. Overall, the soldering system’s ability to drive

the tip to quickly reach and maintain the desired temperature, between 482 to 842°F (250 to 450°C), and do so throughout the entire soldering process, is critical. There are a number of points to consider.

Time to Temperature. This is how fast the cold tip initially heats up to the full desired tempera- ture, so operators are not forced to wait long peri- ods for soldering stations to warm up.

These are measured by how many components or PCBs can be completed in a given time, without the need for further rework or scrap. With a nod to the real estate mantra of “loca-

tion, location and location,” the three key deter- mining factors in soldering performance can be said to be “temperature, temperature and temper- ature.” Temperature shows up in the soldering workflow in several important ways.

Dwell Time (Temperature Stability). Once the operator places the hot tip to the joint, the heat flows from the tip to the joint and melts it. This creates a “wettable” condition, with the solder flowing to create the permanent electrical bond. How quickly this occurs depends on the thick-

ness of the board, the amount of copper and other variables. As this heat is exchanged, the soldering system must maintain the tip’s temperature as it is pressed into the joint to melt the solder quickly and consistently. If the system does not have the necessary power, the operator must wait as the tip fights to regain temperature and complete the joint. The larger the joint, the more important this factor is, since the time to complete the joint will be proportionally larger and increases exponentially if the tip keeps fighting to maintain temperature. Further, it is important to note that excessive

exposure to high temperatures can damage adjacent components and the board itself, making minimizing contact between the tip and the board critical.

Recovery Time. Once the joint is completed and the operator can lift the tip from the joint, the tip needs to recover its heat in order to begin the next solder joint as quickly as possible. Soldering sys- tems with insufficient power cannot sustain a high duty cycle and will cause the operator to pause for several seconds to get rolling again. Over the course of a shift, this pause can continue to length- en as the unit gets overworked. Taken together, these soldering system char-

acteristics — time to temperature, dwell time and recovery time to temperature — are the key drivers of performance and will in a large part determine soldering throughput.

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