A QFD Example for Improving The Quality of PCB Assembly

2017-08-12 10:30:13 zhengxiaowei 165

A QFD example for improving the quality of a manufacturing process is shown in Figure 1.4. In this case, the PCB assembly, consisting of surface mount technology (SMT) solder processes, was analyzed, The QFD team used the QFD process to identify customer needs for quality and delivery of PCBs and rank their importance, as well as the process characteristics of various dements in SMT manufacturing, such as process steps and suppliers of PCBs. The customers of PCB assembly were the personnel in the next stage of production: final product assembly and test technicians. The output of the QFD chart indicates which process element was the most important in meeting customer needs. This is the element that the team should focus on to reduce process defects or manufacturing variability. In the example given in Figure 1.4, the relationship matrix and their calculations for the weighted requirements are outlined. It shows that the team should work most effectively on improving the quality of the screening process before all others, to increase internal customer satisfaction. 

PCB Assembly

The customer needs were identified in a survey of the appropriate customers that use the PCBs, which are the output of the manufacturing process, divided into primary and secondary needs. The customers also indicated their ratings of importance for each need. This rating is qualitative and is ranked by the team using a scale of 1 to 5, with the larger number being the most important. The process engineers also identified the PCB assembly process characteristics. The team then generated the relationship matrix by matching the customer needs to the process characteristics, in terms of four levels (strong, medium, weak, and none). There should at least one match for each item in the matrix. If an item from the customer needs is not matched by at least one item in the quality characteristics, then the team has to reevaluate the QFD analysis. This is true of the opposite case of a process characteristic not matched by a least one customer need.

The results of the analysis, or the weighted requirements, are determined by multiplying the importance factor by the relationship strength. The screening operation achieved the highest score, indicating that customer needs are best satisfied when that process is improved before the others. This chart represents the analysis by the QFD team at that moment in time, and their collective findings; it does not necessarily reflect a universal solution to improving an SMT process.

 

Refationships

Target

Values


1 mode

xbs

xx

n steps


■ Strong = 9 pts • Medium s 3 pts A Weak = 1 pt

Customer Needs

Product

Characteristics


Installation

modes

Force on Equipment Panel

RF

Shielding

Installalion

steps

...

Importance






Clear picture

Easy to tell when installed



A

Long lifetime


_




Simple to install |




0

Weighted Requirements


327

314

322 |

234


Enhanced Specifications Direction


l

r

r

i


Figure 1.3 Raychem CATV new connector QFD matrix.

QFN

The competitive analysis portion of the QFD chart is used mostly for product design. It outlines the team’s evaluation of the position of the company s current products against the competition as perceived by the customers. The team could decide to counteract a particular deficiency of the current design in meeting one of the customer needs, and therefore add a multiplier to the importance factor. This multiplier forces the design team to focus on reversing this deficiency in the new product. This occurs when the deficient customer need generates a higher score when multiplied by the importance factor.

As was shown by both design and manufacturing examples, QFD can be an excellent tool to improve the design quality and to attain six sigma levels through focusing on customer needs. In the design example, it can be used to show which specifications should be widened and which can be left alone or even reduced. Widened specifications would affect the numerator of the six sigma equation, making the goal of six sigma easier to achieve. In the manufacturing example, it was used as a defect reduction tool by the manufacturing quality team to identify which process should be investigated to reduce defects and hence manufacturing variability. Such processes could undergo a design of experiments (DoE) project to reduce variability, which is the denominator of the six sigma equation.

It is important to note that QFD is a process designed to solicit customer needs from experienced users of established products or processes. In both examples, those directly involved in the use of the product, such as cable installers or the recipients of PCBs, were part of the customer needs assessment. Products and processes using new technology would benefit less from QFD. For example,it would not be beneficial for slide rule users to quantify their experience into customer needs for calculators. In this case, more traditional marketing research methods could substitute for QFD.



TAG:   PCB Assembly