Laser Diode Driver Circuit Design A laser diode converts current into light with a threshold below which it behaves as a light emitting diode and above which it lases. It is also the most fragile component in most optical products, and almost every failure is caused by an electrical event…

No Clean Flux Residue And Its Acceptance A no clean process is named for what it does not require, not for what it leaves behind. There is always a residue, and the distinction is that the residue has been formulated to be non corrosive and non conductive at the levels…

PCB Test Coupon Design and What It Proves A test coupon is a small structure built on the same panel as the product, with the same materials and the same process, so that it can be measured destructively without destroying a board. Why the Coupon Exists The coupon answers the…

Heatsink And Stiffener Bonding To A PCB A stiffener or a heatsink is a second material attached to the board after fabrication, and the joint between them is an adhesive rather than a solder. The joint has to carry a mechanical load, survive the thermal excursions of assembly and of…

Package on Package Assembly and Solder Ball Attach A package on package assembly stacks one package on another through a row of solder balls around the edge of the lower package. Both joints are made at the same time, and the upper package decides whether the lower one can be…

Component Sourcing: Authorised Distribution and Open Market Where a part is bought decides how much is known about it. The same part number from an authorised distributor and from an open market broker is not the same level of confidence, and the difference is invisible until it matters. The Channels…

AOI False Calls And Program Tuning Automated optical inspection, usually shortened to AOI, is a measurement system that uses cameras and algorithms to compare what is on the board with what the program expects. Its usefulness depends less on the hardware than on the program, because a program that flags…

Thermal Via Array Design Under Power Devices A power device mounted on a copper pad dissipates most of its heat through the board. The vias under the pad are the path, and their number, size and arrangement decide the junction temperature more than the pad area does. The Path Through…

Preventing Board Handling Damage in SMT Production Most assembly defects have a process signature that can be traced to a machine setting. Handling damage is different. It is caused by a person or a mechanism touching a board in a way that leaves no mark at the time, and it…

Press Fit Connector: Press-Fit Connector Assembly in Production A press fit connector is held in the board by an interference fit between a compliant pin and a plated hole. There is no solder in the joint, so the whole connection depends on the geometry of the pin, the diameter of…