Optiprint: Optical 3D measurement of depth and diameter of microvias

Optiprint is a supplier of highly innovative printed circuit boards for use in medical engineering, the automotive and sensor industries, and space engineering. When the company was probing the market for a non-contact, areal surface measurement system, Alicona's 3D measurement systems attracted its attention. Optiprint now relies on InfiniteFocusSL in the quality assurance of printed circuit boards. The solution by Alicona combines dimensional metrology and surface roughness measurement and allows Optiprint to measure complex, miniaturized component surfaces with just one system.

3D measurement of topography and flatness

Today's printed circuit boards are carriers for simple to highly complex circuits. For 30 years now, Optiprint in Berneck (Eastern Switzerland) has been producing highly innovative solutions for circuit boards. New high-performance materials and more efficient ways of assembly, such as the Chip-on-Board technology, are becoming increasingly relevant. In light of these challenges, Optiprint was in need of a system for areal topography and flatness measurement of so-called milled pockets."Alicona's 3D measurement system have allowed us to optimize our processes significantly and take major steps in securing the quality leadership of our products,“ quality manager Simon Hütter explains. The 3D measurment solutions provided by Alicona have made it possible for customers of Optiprint to ensure flawless chip bonding (attaching of the chips) and wire bonding (attaching wires to connect chip and circuit board carrier). 

Microvias: optical 3D measurement of diameter and depth

Optiprint’s quality assurance puts great emphasis on providing printed circuit boards that are well-suited to further processing by customers. In order to ensure proper electrical bonding (interconnecting) of multi-layered circuit boards, it is vital that the so-called microvias have been drilled according to pre-defined depth and diameter parameters. Alicona's measurement systems allow Optiprint to verify diameter and height step of the microvias to confirm that the correct layers have been bonded.

Roughness measurement ensures functionality

Another type of measurement of laser-dilled microvias is checking for traces of powder. Traces of powder form at the outer edge of drill holes when molten material lumps together. With optimized laser parameters for the different materials these bulges are minimized. To identify bulges, the planarity at the transition of the surface to the microvia is carried out with roughness measurements by Alicona systems.Apart from the above-mentioned measurements of depth, diameter, and planarity, microvia bottoms also need to be examined during quality assurance. The most critical fault to check for here is residual insulating material, as this can impede the electrical conductivity of the entire circuit board. It is therefore essential to verify that this area of the microvia is clean before further processing. Optiprint accomplishes this with Alicona's high-resolution true-color 3D visualization systems. 

Chip pockets: Area based measurement of shape and flatness

As the next step of the production process, so-called milled pockets, also referred to as chip pockets, are milled into the circuit board to make room for the chips the end customer will later attach to the circuit board. Attaching the chips to the milled pockets is also called Chip-on-Board technology. In order for the silicone chips to remain in place securely, the milled pockets must have the correct shape and be flat. Thanks to Alicona’s roughness measurement system, Optiprint has managed to gain a better understanding of the interaction between surface properties and assembly process. This in turn has resulted in a much more efficient manufacturing process. In order to ensure proper surface quality and, consequently, flawless attaching, Optiprint measures the height steps as well as shape and flatness of the chip pockets. "Only when we started using areal roughness measurement was it that we mastered the process for milled pockets," says Simon Hütter.

3D profile form measurement of bondpads

Another step in the manufacturing process is the electrical bonding (interconnecting) of the Chips on Board. The electrical interconnecting of chips with the circuit board with using the so-called bond wires is also called wire bonding. Bondpads must be free of faults such as roughness and dirt, as these weaken the bond interconnection. Alicona's 3D profile measurement system enables Optiprint to verify the form and co-planarity of contact pads on the printed circuit board and ensure perfect conditions for wire bonding.