Automated inspection seems the most rapidly growing segment within quality assurance of board assemblies. Researchers expect the worldwide market for imaging systems (optical and X-ray) to grow from Euro 270m in 1999 to about Euro 600m in 2004, whereas the lion’s share is AOI. X-ray technology will probably account for about 25 to 30% of this.
Key drivers for this growth are the continuing miniaturization and the increasing board density, which has rendered manual inspection not longer viable, and exceeds the capabilities of electrical testers. Next QA and SPC (sta-tistical process control) strategies will primarily focus on combinations of AOI, X-ray and electri-cal gear to maximize the procedure, with links to collect data for rework and for process improvement.
Historically, electronics manufacturing has relied on a combination of human inspection and electrical tests to verify product quality. The first AOI and X-ray systems were introduced during the 1980s. Early users were frequently disappointed with speed, effectiveness, ease of use and cost of ownership.The acceptance of these systems was thus very restricted, and only a few years ago, the interest in inspection technologies began to bloom anew.
There are several potential areas where AOI systems can be used on a typical SMT line: post-print, post-placement and post-reflow. AXI systems, how-ever, are focused on the verification of visually hidden parts, solder joints or field-array package (BGA, flip chip, CSP, etc.) I/Os. Their preferred application area is at the line end (post-reflow). Both kinds of inspection methods are only being accepted as complementary technologies, as for the verification of assembly functionality electrical tests are still a high requirement. Moreover, users of electrical testers who are used to carefully debug their programs once, and then working with them on a very solid basis undisturbed for a long time, will experience that AOI is different. All variations of placement positions, shades of color of the PCB or the components, can lead to a continual tuning of an inspection program, meaning that these variations have then to be teached. Only then can the daily-generated bonepile of boards be mastered. Gerhard B. Wolski
Interested readers will find a market survey on currently available AOI and AXI systems from leading suppliers under our homepage (www.epp-online.de). Here we have also put some additional editorial such as: manual 3D inspection; AOI and real-time SPC; package verification with moiré interferometry; automated high-precision 3D AOI; pre-reflow based on laser-scanning; user experience with 2D/3D X-ray system; and verification of polymeric LED displays. For those who are not internet aficionados, we will publish the technology articles on paper regularly in upcoming issues.
Contents
X-ray application issues 2
User experience with AOI 5
Off-axis X-ray inspection 8
Key AOI driving factors 11
AOI used for 6-sigma approach 14
Benefit of color-driven AOI 18
Inspection with endoscope 20
Visual inspection guidance 22
Black&white versus color AOI 24
Scan-based AOI technology 26
Integrated AOI and AXI 28
Case study on AXI application 30
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