Technical Library | 2017-10-26 01:18:49.0
Nano-coatings have been introduced by various manufacturers, with the promise of addressing some of the challenges relative to solder paste printing. Stated benefits include: Reduced underside cleaning, reduced bridging, improved solder paste release and improvements in yield. With several nano technologies already on the market and more likely to be introduced, how can the performance be quantified? How robust are these coatings? How can an assembler approach the ROI of these coatings? What hidden benefits or negative impacts should be considered? This paper will present a rigorous method for evaluating the performance and economic benefits of solder paste stencil nano-coatings.
Technical Library | 2023-05-22 16:49:42.0
Our customers' issues • Apertures are getting smaller • Paste does not release as well • Contaminates the bottom of the stencil • Increases defects / reduces yield Insufficient solder Bridging Solder balls on surface of PCB Flux residue • Requires more frequent cleaning • Reduced efficiency (wasted time) • Increased use of consumables (cost) USC fabric (use "cheap" fabric to reduce cost) Lint creates more defects Cleaning chemistries (use IPA to reduce cost) IPA breaks down flux and can create more defects
Technical Library | 2022-01-26 15:26:56.0
In this work an attempt is made to improve the fracture toughness and electrical conductivity of epoxy/glass fiber based laminates by the inclusion of carbon nanotube (CNT) fillers. The fiber orientation of the epoxy/ glass fiber (GF) fabric laminates was optimized based on estimation of mechanical properties. The carboxylic acid functionalized CNTs were incorporated into epoxy matrix by ultra-sonication method. The nano filled epoxy resin was used to prepare laminates with 30/45 GF fabric orientation. The CNT content was varied and its effect on the tensile properties was determined. The fracture toughness of multiphase composites was estimated using single edge notch bend (SENB) test. The presence of CNTs improved the fracture toughness by a crack bridging mechanism. The volume resistivity of multiphase composites was found to be superior to the conventional epoxy/CNT composite. The presence of glass fabric reduces the number of inter-tube contacts contributing to the reduction in volume resistivity.
Technical Library | 2021-09-29 13:35:21.0
In PCB circuit assemblies the trend is moving to more SMD components with finer pitch connections. The majority of the assemblies still have a small amount of through hole (THT) components. Some of them can't withstand high reflow temperatures, while others are there because of their mechanical robustness. In automotive applications these THT components are also present. Many products for cars, including steering units, radio and navigation, and air compressors also use THT technology to connect board-to-board, PCB's to metal shields or housings out of plastic or even aluminium. This is not a simple 2D plain soldering technology, as it requires handling, efficient thermal heating and handling of heavy (up to 10 kg) parts. Soldering technology becomes more 3D where connections have to be made on different levels. For this technology robots using solder wire fail because of the spattering of the flux in the wires and the long cycle time. In wave soldering using pallets the wave height is limited and pin in paste reflow is only a 2D application with space limitations. Selective soldering using dedicated plates with nozzles on the solder area is the preferred way to make these connections. All joints can be soldered in one dip resulting in short cycle times. Additional soldering on a small select nozzle can make the system even more flexible. The soldering can only be successful when there is enough thermal heat in the assembly before the solder touches the board. A forced convection preheat is a must for many applications to bring enough heat into the metal and board materials. The challenge in a dip soldering process is to get a sufficient hole fill without bridging and minimize the number of solder balls. A new cover was designed to improve the nitrogen environment. Reducing oxygen levels benefits the wetting, but increases the risk for solder balling. Previous investigations showed that solder balling can be minimized by selecting proper materials for solder resist and flux.
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