Workmanship standards

NDT has a very important formal status. Requirements for performanee of NDT, acceptance criteria and requirements for personnel qualification are implemented in codes and standards. The NDT procedure is part of the contract. During the many years that NDT methods have been used in industry a well-established situation has evolved, enabling the use of NDT for the evaluation of welds against Good Workmanship Criteria on a routine basis, thus maintaining workmanship standards and minimising the risks of component failure. 

Define the process specifications and workmanship standards to be achieved. 

Process control—Requires procedures to ensure that production processes are carried out under controlled conditions. This includes the documentation, monitoring, and control of suitable process characteristics use of approved equipment and workmanship standards. 

VI.36. The reference flaw of 6 1 aspect ratio should have an area, normal to the direction of maximum stress, greater than typical pre-service inspection indications that might be cause of rejection or repair of a fabricated packaging containment wall. However, since the reference flaw is a crack-like surface defect, rather than a more typical real defect (e.g. subsurface porosity cloud or slag inclusion), the selection of this flaw size is extremely conservative relative to workmanship standards. 

The most widely used workmanship standard, IPC-A-610, has been rewritten to accommodate the inspection of Pb-free soldered assemblies. The changes were introduced with version D of that document. Inspection personnel require retraining to give proper attention to the... 

FIGURE 46.2 A BGA solder joint rife with voids from flux-derived gases and improper soldering profile. These voids can detract from the reliability of the solder joint. The IPC-A-610 workmanship standard for printed circuit assemblies (PCAs) should be consulted on void acceptability. (Courtesy of Hewlett-Packard.)... 

A good rule of thumb for scratch criteria that some companies have adopted as a workmanship standard includes the following ... 

Many standards cover printed circuit board assemblies. Most major electronics manufacturers have their own internally developed workmanship standards. Several industry and military standards also exist. However, the joint industry standard IPC-A-610D, Acceptability of Electronic Assemblies, is the standard most often referenced for criteria defining reliable solder connections. This standard was developed by the Institute for Interconnecting and Packaging Electronic Circuits (IPC) (www.ipc.org). 

Workmanship standards are essential to the smooth and successful operation of any quality control system. They are considered the best means of achieving quality workmanship. 

Some of the most obvious advantages of such workmanship standards are a lower reject rate, elimination of unnecessary rework, early detection of defects, and reduced risk of rejecting good parts. Proper implementation of workmanship... 

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