Technical Library | 2019-05-24 09:22:59.0
There is a smaller process window and a much narrower margin of error when creating and using lead-free reflow profiles for surface mount parts on printed circuit boards (PCBs). Solder balls, dewetting, tombstones, voids, and head-on-pillow problems will occur much more frequently because lead-free alloys behave differently than eutectic pastes. Problems are compounded due to the extra heat necessary for some lead-free pastes to reach their melting points.
Technical Library | 2024-04-29 21:39:52.0
In this paper, we develop and put into practice an Automatic Optical Inspection (AOI) system based on machine vision to check the holes on a printed circuit board (PCB). We incorporate the hardware and software. For the hardware part, we combine a PC, the three-axis positioning system, a lighting device and CCD cameras. For the software part, we utilize image registration, image segmentation, drill numbering, drill contrast, and defect displays to achieve this system. Results indicated that an accuracy of 5µm could be achieved in errors of the PCB holes allowing comparisons to be made. This is significant in inspecting the missing, the multi-hole and the incorrect location of the holes. However, previous work only focusses on one or other feature of the holes. Our research is able to assess multiple features: missing holes, incorrectly located holes and excessive holes. Equally, our results could be displayed as a bar chart and target plot. This has not been achieved before. These displays help users analyze the causes of errors and immediately correct the problems. Additionally, this AOI system is valuable for checking a large number of holes and finding out the defective ones on a PCB. Meanwhile, we apply a 0.1mm image resolution which is better than others used in industry. We set a detecting standard based on 2mm diameter of circles to diagnose the quality of the holes within 10 seconds.
Technical Library | 2008-10-29 18:45:53.0
Growing demand for compact, multi-function electronics products has accelerated component miniaturization and high-density placement, creating new challenges for the electronics manufacturing industry. It is no longer adequate to simply place parts accurately per a pre-defined CAD assembly program because solder paste alignment errors are increasing for numerous reasons. The solution to this problem is a system in which the placement machine can automatically detect and compensate for misalignment of the solder paste to produce high-quality boards regardless of the process errors beforehand.
Technical Library | 2009-12-14 20:24:19.0
In the lead-free era, thermal profiling has a critical role in the SMT assembly process. We discuss the profiling, tools, practical issues, and inspection methods of golden boards, and related tools. As the process window narrows, profiling equipment and/or thermocouple (TC) errors must be taken into consideration. In addition, the accuracy and attachment method of the thermocouple will significantly impact critical assemblies.
Technical Library | 2019-08-15 13:31:52.0
Cracks in ceramic chip capacitors can be introduced at any process step during surface mount assembly. Thermal shock has become a "pat" answer for all of these cracks, but about 75 to 80% originate from other sources. These sources include pick and place machine centering jaws, vacuum pick up bit, board depanelization, unwarping boards after soldering, test fixtures, connector insulation, final assembly, as well as defective components. Each source has a unique signature in the type of crack that it develops so that each can be identified as the source of error.
Technical Library | 2024-01-08 21:31:01.0
The aim of this collection and interpretation is to develop an understanding of moisture in materials, especially in printed circuit boards, to know the effects on further processing and to be able to derive targeted corrective actions when moisture-related problems occur. In principle, the considerations are valid for all types of PCBs. Although these basic principles are of particular importance when working with flexible and rigid-flexible printed circuit boards; observing them can mean the difference between success or failure.
Technical Library | 2001-04-24 10:47:02.0
Board-level circuits today routinely run at speeds of 100 MHz or more and are composed of dozens of complex interacting VLSI components. To design such circuits in a timely and correct manner it is necessary to pay close attention to circuit timing early in the design cycle. At fast clock speeds, managing component and interconnect propagation delay becomes a key aspect of circuit design. It is imperative that the critical paths on a circuit and the slack available for interconnect delay consumption be identified early, and drive subsequent stages in the design flow.
Technical Library | 2018-02-22 10:56:36.0
As companies start to implement lead free soldering processes, hand soldering and associated techniques have been identified as key functions in the manufacturing process requiring additional research and development. Hand soldering tends to occur at the end of the process line where the circuit board has a high intrinsic value and so correct process control will have a significant affect on manufacturing costs and productivity.This paper discusses the fundamental aspects of the hand soldering process and discusses process adaptation requirements for successful lead free implementation.
Technical Library | 2009-12-23 16:55:08.0
Leading up to the development of lead-free soldering alloys, Horizontal Convection* was developed for the reflow process. Getting the correct temperature profile, with the narrow process window in lead-free applications, is now more important than ever. In each chamber or zone, air is circulated toward one side of the oven above the PCB and toward the opposite side of the oven below the PCB, forming a cyclone around the board. The forced air circulation results in a uniform temperature profile along the entire circuit board assembly. This technology is ideal for the precise profiles needed for lead free soldering.
Technical Library | 2022-01-05 23:20:33.0
This study aims to present the characterization of five different types of printed circuit boards (PCBs) for use in future recycling processes. PCBs used: motherboards, lead free motherboards, video cards, memory and printer cards. The comminution of the circuit boards was performed using blade mills and hammer mills with 9mm and 6mm meshes, respectively. Throughout the physical processing, analysis was made with stereoscopic optics to ensure that the correct materials had been released. The pre-magnetic separation parts were given a granulometric classification followed by acid digestion and loss on ignition tests.
