Technical Library | 2019-10-21 09:58:50.0
An ACI Technologies customer inquired regarding printed circuit board(PCB) failures that were becoming increasingly prevalent after the SMT (surface mount technology) manufacturing process. The failures were detected by electrical testing, but were undetermined as to the location and specific devices causing the failures. The failures were suspected to be caused predominately in the BGA (ball grid array) devices located on specific sites on this 16 layer construction. Information that was provided on the nature of the failures (i.e., opens or shorts) included high resistance shorts that were occurring in those specified areas. The surface finish was a eutectic HASL (hot air solder leveling) and the solder paste used was a water soluble Sn/Pb(tin/lead).
Technical Library | 2012-12-26 20:18:50.0
①Single side The basic flexible printed circuit board is used of substrate of single side pcb materials and coated coverlay after finishing printed. ②Double sided That is made of substrates of double sided printed circuit board with double surface coated coverlays after finishing printed. ③Single copper foil with double coverlays Single copper foil coated different coverlays with double surface after finishing printed. ④Air gap Laminating two single printed circuit board together with no glue and bare design to meet high flexibility requirements. ⑤Multilayer That is designed for three and above circuit layers by laminating single side printed circuit board or double sided printed circuit board. ⑥COF IC chips and electronic components are installed on the flexible circuit board directly. ⑦Rigid-Flexible PCB Combined to rigid PCB with supporting and flexible PCB with high flexibility.
Technical Library | 2021-03-10 23:57:29.0
Latent short circuit failures have been observed during testing of Printed Circuit Boards (PCB) for power distribution of spacecraft of the European Space Agency. Root cause analysis indicates that foreign fibers may have contaminated the PCB laminate. These fibers can provide a pathway for electromigration if they bridge the clearance between nets of different potential in the presence of humidity attracted by the hygroscopic laminate resin. PCB manufacturers report poor yield caused by contamination embedded in laminate. Inspections show ...
Technical Library | 2010-03-18 14:02:03.0
Selecting products that have been qualified by industry standards for use in printed circuit board assembly processes is an accepted best practice. That products which have been qualified, when used in combinations not specifically qualified, may have resultant properties detrimental to assembly function though, is often not adequately understood. Printed circuit boards, solder masks, soldering materials (flux, paste, cored wire, rework flux, paste flux, etc.), adhesives, and inks, when qualified per industry standards, are qualified using very specific test methods which may not adequately mimic the assembly process ultimately used.
Technical Library | 2016-10-27 16:24:23.0
Press-fit technology is a proven and widely used and accepted interconnection method for joining electronics assemblies. Printed Circuit Board Assembly Systems and typical functional subassemblies are connected through press-fit connectors. The Press-Fit Compliant Pin is a proven interconnect termination to reliably provide electrical and mechanical connections from a Printed Circuit Board to an Electrical Connector. Electrical Connectors are then interconnected together providing board to board electrical and mechanical inter-connection. Press-Fit Compliant Pins are housed within Connectors and used on Backplanes, Mid-planes and Daughter Card Printed Circuit Board Assemblies. High reliability OEM (Original Equipment Manufacturer) computer designs continue to use press-fit connections to overcome challenges associated with soldering, rework, thermal cycles, installation and repair. This paper investigates the technical roadmap for press fit technology, putting special attention to main characteristics such, placement and insertion, inspection, repair, pin design trends, challenges and solutions. Critical process control parameters within an assembly manufacturing are highlighted.
Technical Library | 2020-08-27 01:22:45.0
Initially adopted internal specifications for acceptance of printed circuit boards (PCBs) used for wire bonding was that there were no nodules or scratches allowed on the wirebond pads when inspected under 20X magnification. The nodules and scratches were not defined by measurable dimensions and were considered to be unacceptable if there was any sign of a visual blemish on wire-bondable features. Analysis of the yield at a PCB manufacturer monitored monthly for over two years indicated that the target yield could not be achieved, and the main reasons for yield loss were due to nodules and scratches on the wirebonding pads. The PCB manufacturer attempted to eliminate nodules and scratches. First, a light-scrubbing step was added after electroless copper plating to remove any co-deposited fine particles that acted as a seed for nodules at the time of copper plating. Then, the electrolytic copper plating tank was emptied, fully cleaned, and filtered to eliminate the possibility of co-deposited particles in the electroplating process. Both actions greatly reduced the density of the nodules but did not fully eliminate them. Even though there was only one nodule on any wire-bonding pad, the board was still considered a reject. To reduce scratches on wirebonding pads, the PCB manufacturer utilized foam trays after routing the boards so that they did not make direct contact with other boards. This action significantly reduced the scratches on wire-bonding pads, even though some isolated scratches still appeared from time to time, which caused the boards to be rejected. Even with these significant improvements, the target yield remained unachievable. Another approach was then taken to consider if wire bonding could be successfully performed over nodules and scratches and if there was a dimensional threshold where wire bonding could be successful. A gold ball bonding process called either stand-off-stitch bonding (SSB) or ball-stitch-on-ball bonding (BSOB) was used to determine the effects of nodules and scratches on wire bonds. The dimension of nodules, including height, and the size of scratches, including width, were measured before wire bonding. Wire bonding was then performed directly on various sizes of nodules and scratches on the bonding pad, and the evaluation of wire bonds was conducted using wire pull tests before and after reliability testing. Based on the results of the wire-bonding evaluation, the internal specification for nodules and scratches for wirebondable PCBs was modified to allow nodules and scratches with a certain height and a width limitation compared to initially adopted internal specifications of no nodules and no scratches. Such an approach resulted in improved yield at the PCB manufacturer.
Technical Library | 2021-11-26 14:34:07.0
The use of desiccant bags filled with Silica Sand and or Clay beads used in conjunction with a Moisture Barrier Bag to control moisture for storage of printed circuit boards has long been an accepted practice and standard from both JEDEC and IPC organizations. Additionally, the use heated ovens for baking off moisture using the evaporation process has also been a long#2;standing practice from these organizations. This paper on alternative drying methods will be accompanied by completed independent, unbiased tests conducted by Vinny Nguyen, an engineering student (now graduated) from San Jose State University. The accompanied paper will examine the performance levels of different technologies of desiccant bags to control moisture in enclosed spaces. The tests and equipment set were reviewed by an engineer and consultant to the Lockheed Martin Aerospace Division and the IPC - TM-650 2.6.28 test method was review by engineer from pSemi. The tests were designed to mimic performance tests outlined in Mil Spec 3464, which both IPC and JEDEC have adopted for their respective standards. The test examined variables including absorption capacity rates, weight gain and release of moisture back into the enclosed area. The presentation will also address and highlight: • Similarities of PCBs and Heavy Equipment as it applies to Inspections, Causes of Failure, Types of Corrosion and Moisture Collection Points. • Performance Attributes of Different Desiccant Technologies as it applies to shape, texture, change outs, labeling and regeneration. • Venn Diagram of Electromechanical Failure with the circles 1. Current 2. Contamination 3. Humidity Presentation Available
Technical Library | 2010-04-22 14:55:51.0
It is now widely accepted that using designed experiments is the most effective way to optimize surface mount technology (SMT) processes. This situation begs the question "what is an effective strategy in implementing this powerful tool?" This paper will present such a strategy that incorporates Taguchi's approach for screening, full factorial analysis for optimization and central composite design for precise modeling. We will present these techniques using MINITABTM Release 13 statistical software and printed circuit board industry applications.
Technical Library | 2008-04-15 14:43:08.0
The increasing demands for miniaturization and better functionality of electronic components and devices have a significant effect on the requirements facing the printed circuit board (PCB) industry. PCB manufactures are driving for producing high density interconnect (HDI) boards at significantly reduced cost and reduced implementation time. The interconnection complexity of the PCB is still growing and today calls for 50/50 μm or 25/25 μm technology are real. Existing technologies are unable to offer acceptable solution. Recently the Laser Direct Imaging (LDI) technology is considered as an answer for these challenges.
Unipress - Institute of High Pressure Physics of the Polish Academy of Sciences
Technical Library | 2021-11-22 20:32:10.0
The aim of this work is to define a procedure to develop diagnostic systems for Printed Circuit Boards, based on Automated Optical Inspection with low cost and easy adaptability to different features. A complete system to detect mounting defects in the circuits is presented in this paper. A low cost image acquisition system with high accuracy has been designed to fit this application. Afterward, the resulting images are processed using the Wavelet Transform and Neural Networks, for low computational cost and acceptable precision. The wavelet space represents a compact support for efficient feature extraction with the localization property. The proposed solution is demonstrated on several defects in different kind of circuits.
Midwest Circuit Technology provides Carbide Router Bits and End Milling Cuters for use in PCB Depaneling equipment. We have over 35 years of supplying tools and machining experience in drilling, Routing, Test Fixture manufacture.
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