Bob Willis

Get agreement on what constitutes “rework” – and a capable operator.

This month we look at etching defects and their removal – or presence, as in the case of FIGURE 1. A customer was surprised to find a batch of bare boards with this level of rework.





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Figure 1. Example of poor etching.

First, it’s important for customers and their suppliers to define what is considered rework. Excess copper is clearly present under the solder mask and should have been noticed during final inspection, but also long before, during AOI. At that stage, depending on the specification and level of rework required, it may have been better to scrap the panels. If it were a double-sided board, I would scrap the panels. If it were a multilayer board, I would ask the customer if I could rework the boards to reduce delays.

Many skilled operators could have performed this rework much better. Notice the lighter green color in the mask window. This would not be acceptable at any level of international bare board standards.

We have presented live process defect clinics at exhibitions all over the world. Many of our Defect of the Month videos are available online at Find out how you can share our new series of Defect of the Month videos to explain some of the dos and don’ts with your customers via CIRCUITS ASSEMBLY:

Bob Willis is a process engineering consultant; This email address is being protected from spambots. You need JavaScript enabled to view it.. His column appears monthly.

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