Thermal Profiling is a recognized necessity. As mid-to-high volume production continues to dominate in many areas, it is beneficial to understand the available choices in profiling, and which ones will work best under what circumstances. One of the main distinctions to be made is between board profiling and oven profiling. Having said that, it must be clear as to exactly when it is possible to effectively replace board profiling with oven profiling, the benefits of doing so, and the parameters that are required for successful implementation.
The obvious distinction is simple. In board profiling you are placing multiple thermocouples on a populated board to ensure the target thermal profile specified by the OEM or solder paste manufacturer is met during reflow. That process is then repeated with each subsequent run to provide both verification and documentation that it is in spec, meeting that same target profile. There is, however, wear and tear on any populated board that is repeatedly profiled, resulting in occasional product loss. In addition, there is a certain amount of time required for whatever method (soldering or tape) is used to attach thermocouples, and there is always downtime involved as you switch from product to product (changeover), which often require different target profiles or oven recipes. In high-volume production, the addition of more lines to handle large orders means an additional profile for each line.
We will be making a distinction here between profiling the product, i.e. making sure it meets a specific target profile, and profiling the oven. In profiling the oven, as we are using the term, we are trying to establish that the oven is replicating an already established product profile during each product run without actually profiling a populated board. Data must be obtained, however, to show that the subsequent oven profiles produce the original target. Anecdotal evidence will not suffice, as the need for documentation and verification has increased.
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