Bruce Butkus Product Line Manager Edmund Optics Courtesy of Edmund Optics.

As designers continue to propose ever-smaller, ever-more-complex circuits, the demands on inspection equipment push the limits of what today's cameras can provide. Bruce Butkus, product line engineer for Edmund Optics, offered his observations on the resulting challenges.

Q: What do you regard as the most significant issue facing the inspection industry?

A: Being able to see all of the circuit's features in enough detail despite higher production volumes. Manufacturers of mobile phones and automotive electronics, for example, don't want any defects. Yet, as the components get smaller, the defects get smaller as well. You end up pushing the limits of camera performance.

If you raise the resolution, you necessarily reduce the field of view. At twice the resolution, you can only cover a quarter as much area, so you need four times the number of images.

A: You can add more cameras to the inspection system or you can make the same number of cameras work faster. But for one camera to capture more images in a period of time, you have to reduce the exposure time, reducing the time during which light gets through the lens.

That, in turn, requires rethinking lighting schemes. In fact, proper lighting becomes one of the critical issues. The lights have to be brighter to start with.

In addition, a board featuring highly complex geometry that includes components of different sizes and heights, different shapes of solder paste, and other irregularities poses a complicated environment to achieve adequate lighting. You can use software to enhance the images and thereby increase the level of detail, but generally not fast enough to do it on the fly.

Q: Is resolution the limiting factor?

A: We're definitely approaching the fuzzy edge of what camera designs can deliver. We can specify adequate performance on paper, but manufacturing real cameras that can achieve that level of performance is becoming more and more difficult.

The technology of television-class resolution hung around for 50 years. The newest tools have increased that resolution by a factor of 20 in barely eight years. We can't increase resolution by another order of magnitude without making major compromises in other performance parameters, and certainly in cost.

Q: Are customers who are looking for this optimum performance still so cost-conscious?

A: Part of the problem is perception. There is a vast price difference between a consumer-grade camera and an industrial-grade camera that delivers the same specifications. You can walk into any electronics retailer and get a certain specification camera for, say $150. But the consumer product is designed for casual photography and occasional light use.

A comparable industrial-grade camera designed to work reliably and unattended in a manufacturing line would be priced more than an order of magnitude higher. Like the consumer models, these cameras have also undergone substantial price erosion in recent years. A few years ago, that camera might have cost $80,000. Industry experiences the same price erosion as the consumer world, but from a much higher starting point.