Defects must be found and their causes corrected so that the EMS can deliver high-quality assemblies on time — a key focus at LIAD Electronics, a privately owned contract manufacturer in Breda, The Netherlands. The company has been at the forefront of manufacturing and quality assurance for its customers since the company was founded in 1988 — specializing in high end electronic assemblies.
Eric Meesterburrie, LIAD's Managing Director, described the challenge facing his company: "With ever-decreasing component sizes, including their leads and solder joints, LIAD decided to look into 3D measurement in addition to the traditional 2D AOI that we were used to, for the end-of-line quality control. During the evaluation process, it became clear to us that the overwhelming advantages of the new 3D measurement technology would be the answer to all of our needs."
The company had already invested in a 3D SPI system from Koh Young Technology, which allowed optimizing the printing process, ensuring that the volume of solder paste was precisely deposited onto the PCB land patterns. 3D AOI, a post-reflow operation that is more accurately termed automated an "optical measurement technique", could now be employed to measure the solder joints downstream. Working in synch with the SPI machine further back in the line, it provides the highest assurance of quality for the company's customers.
Meesterburrie adds that LIAD's investment in AOI does not only consist of the AOI System hardware and corresponding repair station, but also the AOI programmer and the rework operator. Hence the programming time, programming consistency and ergonomics are key to ensuring the best utilization of LIAD's resources.
"It is our mission to have in-line measurements of solder-paste (SPI), and solder joints and component placement measurement (AOI), all working together, to eliminate defects in the process. We want to have no manufacturing defects to be found during functional test. It's a tall order, but it is our goal," Meesterburrie says. LIAD's decision to acquire the Koh Young 3D Measurement System was mutually made by all departments, after an exhaustive evaluation process.
So LIAD was again achieving a "first" by purchasing the first Koh Young 3D AOI System in the BeNeLux countries. The Koh Young Zenith System has now been installed for 8 months and has proven itself to have been the right choice.
"Since we're an EMS with a high product mix environment, fast program ramp-up and maintaining measurement capability was highly important to us in our evaluation process," says Fridus Draaijer, Technical and Quality Manager. "Small-to-medium lot sizes and 5 changeovers per day is the norm here. Many years of experience with our existing AOI system had taught us that fast changeover was not always possible with most AOI systems, and setup time is not productive time."
Since there are approximately 300 different boards in production at LIAD at any one time, programming of the AOI system has to keep up with it. The library-based setup of the Koh Young systems allows fast program setup, by conveniently re-using the previously saved parameters and thresholds for a component type, and the system is based on measuring all aspects of the component such as location, solder joints, polarity etc. In 3D, there is no light or color-dependent setting required. 3D height measurement also means that there is no light dependency, which in turn means that there is no shadowing.
Establishing the thresholds and tolerances for LIAD's quality requirements in the new 3D AOI System was a very straightforward task. For example, the need to find lifted leads on multi-leaded devices; a height threshold value of typically 100µm is used to detect lifted leads. As the system returns the measurement value for each lead, it is very easy to determine if a different value is required to detect lifted leads or to decrease the sensitivity. The convenient ability to set up these thresholds at an off-line programming station was another reason to choose the Koh Young System. Since all measurement results are displayed and recorded for previously inspected boards, it enables the programmer to base the thresholds on thousands of data points.
Finding all process defects is the primary task of any AOI system; but "false calls", typical of 2D-based inspection, can be a real problem, holding up production and damaging the credibility of the inspection system. How can one trust the machine 100 percent of the time if it isn't right 100 percent of the time? But with 3D AOI, this problem has been eliminated, and after weeks and even months of use, no defects have slipped through to the functional test stage. This was important because now, the operator at the repair station was not distracted by a large number of false calls made by the AOI machine. Instead, actual defects were (and are) clearly displayed as both 2D and 3D images for ease of recognition and displacement. The result has been better quality products for customers, shorter cycle time, and total IPC-A-610 compliance.
Contact: Koh Young (Europe) Ltd., Unit 1B, Bracken Business Park, Bracken Road, Sandyford Industrial Estate, Dublin 18, Ireland +353 1 293 0180 fax: +353 1 297 3123 E-mail: firstname.lastname@example.org Web: http://www.kohyoung.com