PCB News - PCB problem What is process capability

PCB problem What is process capability

Process capability is the product quality (quality) capability of a process under fixed production conditions and under stable control. Process capability index refers to the degree to which the process capability meets the product quality standard requirements (specification range, etc.), or the process within a certain period of time Here, the actual SMT processing capacity under the control state (steady state). Therefore, before evaluating a process capability, at least the following two requirements should be done:

The capability of a manufacturing process is composed of many factors. Starting from the design of the product, it includes raw materials (Material), machines (Machine), equipment (Equipemnt), operating methods (Method), operator skills, and inspection equipment (Measurement). Equipment), inspection methods, inspection and inspection skills... and other factors. Any changes in these factors can more or less affect its process capability. Therefore, before discussing process capability, it is necessary to fix these that may affect its process. All factors of ability. Therefore, the so-called Standard Operation Procedure (SOP) must be formulated to standardize all steps in the process, and even the amount of material added in each link must be specified.

When all the above factors are standardized and implemented, and the measured values of the process are in a stable state of control, the process capability at this time can be called the engineering capability of the process.

In addition, the process capability usually needs to be measured by measuring its pros and cons, so the steps in the process must be quantified. For example, the printing process can be quantified into pressure, speed, temperature, printing position... etc. And these values can be measured and controlled with numerical values.

When the PCB manufacturer completes the process capability through the above two methods, it usually allows us to understand the process capability that may be achieved in a certain project under a certain combination, and can even be used for the following purposes:

Provide data to facilitate the design of new products or the quality improvement of existing products.

Check whether the process capability of a new or repaired equipment can be accepted.

Help us choose different raw materials, appoint new operators or adopt new operating methods.

For a production batch, adjust various production factors to make an experimental plan, and select the best combination of process parameters.

When the process capacity exceeds the specification tolerance, an appropriate central value can be set to make it the most economical production.

However, in most of the circuit board production processes, the quality of each process tends to vary with the changes in production factors, so that the ideal process capability we expect cannot be achieved. Therefore, we must periodically or irregularly adjust the quality of each process. The quality of the products is measured and evaluated. Generally, we will use control charts or Cpk control methods to achieve this goal.