Technical Library | 2021-11-16 22:17:27.0
Ultrasonics, coupled with an aqueous detergent process that cleans at below 43ºC, may be best suited for fine-pitch SMT screens and stencils. Aqueous detergents clean more effectively than solvents, with little or no environmental impact. Because of the environmental concerns driving today's technology decisions, the once simple decision of selecting a stencil cleaning process is now clouded with different chemicals, different cleaning machines and various types of solder paste, all with specific environmental, health and safety related issues and regulations.
Technical Library | 2013-03-12 13:25:18.0
High density and miniaturized circuit assemblies challenge the solder paste printing process. The use of small components such as 0201, 01005 and μBGA devices require good paste release to prevent solder paste bridging and misalignment. When placing these miniaturized components, taller paste deposits are often required. To improve solder paste deposition, a nano-coating is applied to laser cut stencils to improve transfer efficiency. One concern is the compatibility of the nano-coating with cleaning agents used in understencil wipe and stencil cleaning. The purpose of this research is to test the chemical compatibility of common cleaning agents used in understencil wipe and stencil cleaning processes.Compatibility of Cleaning Agents With Nano-Coated Stencils
Technical Library | 1999-05-07 10:47:00.0
White residue remaining after cleaning circuit board assemblies can be caused by a variety of chemicals and reactions. Rosin and water-soluble fluxes, circuit board resins and epoxies, component materials and other contamination all contribute to this complex chemistry. This paper discusses many of the sources of the residues that seem to be an ever-increasing occurrence.
Technical Library | 2012-11-15 23:38:50.0
First published in the 2012 IPC APEX EXPO technical conference proceedings. As we progress in the 21st century, electronics manufacturing will need more and more precision. Parts will get more complex since more components have to be assembled in smaller spaces. Circuit boards and other electronic assemblies will become more densely populated; spacings between components will be shorter. This will require precision manufacturing and efficient cleaning during and post manufacturing. In addition, with population and technology progressing, larger amount of greenhouse gases will be emitted resulting in higher global warming. Intense research effort is going on to develop new generation of chemicals to address both cleaning and global warming issues. Low global warming solutions in refrigeration and as insulating agents are already in the marketplace.
Technical Library | 1999-05-07 11:44:26.0
In 1990 the United States Environmental Protection Agency Issued the Clean Air Act. The Clean Air Act and subsequent amendments are designed to limit the use of chemicals that contain volatile organic compounds (VOCs). The document goes into great detail setting limits for allowable VOC emissions for different industries.
Technical Library | 2022-10-11 17:27:08.0
Lead-free flux technology for electronic industry is mainly driven by high soldering temperature, high alloy surface tension, miniaturization, air soldering due to low cost consideration, and environmental concern. Accordingly, the flux features desired included high thermal stability, high resistance against burn-off, high oxidation resistance, high oxygen barrier capability, low surface tension, high fluxing capacity, slow wetting, low moisture pickup, high hot viscosity, and halogen-free. For each of the features listed above, corresponding desired chemical structures can be deduced, and the impact of those structures on flux residue cleanability can be speculated. Overall, lead-free flux technology results in a greater difficulty in cleaning. Cleaner with a better matching solvency for the residue as well as a higher cleaning temperature or agitation are needed. Alkaline and polar cleaner are often needed to deal with the larger quantity of fluxing products. Reactive cleaner is also desired to address the side reaction products such as crosslinked residue.
Technical Library | 2016-12-29 15:37:51.0
The reliabilities of the flux residue of electronic assemblies and semiconductor packages are attracting more and more attention with the adoption of no-clean fluxes by majority of the industry. In recent years, the concern of "partially activated" flux residue and their influence on reliability have been significantly raised due to the miniaturization along with high density design trend, selective soldering process adoption, and the expanded use of pallets in wave soldering process. When flux residue becomes trapped under low stand-off devices, pallets or unsoldered areas (e.g. selective process), it may contain unevaporated solvent, "live" activators and metal complex intermediates with different chemical composition and concentration levels depending on the thermal profiles. These partially-activated residues can directly impact the corrosion, surface insulation and electrochemical migration of the final assembly. In this study, a few application tests were developed internally to understand this issue. Two traditional liquid flux and two newly developed fluxes were selected to build up the basic models. The preliminary results also provide a scientific approach to design highly reliable products with the goal to minimize the reliability risk for the complex PCB designs and assembly processes. This paper was originally published by SMTA in the Proceedings of SMTA International
Technical Library | 2017-12-11 22:31:06.0
Typical printed circuit board assemblies (PCBAs) processed by reflow, wave, or selective wave soldering were analysed for typical levels of process related residues, resulting from a specific or combination of soldering process. Typical solder flux residue distribution pattern, composition, and concentration are profiled and reported. Presence of localized flux residues were visualized using a commercial Residue RAT gel test and chemical structure was identified by FT-IR, while the concentration was measured using ion chromatography, and the electrical properties of the extracts were determined by measuring the leak current using a twin platinum electrode setup. Localized extraction of residue was carried out using a commercial C3 extraction system. Results clearly show that the amount and distribution of flux residues are a function of the soldering process, and the level can be reduced by an appropriate cleaning. Selective soldering process generates significantly higher levels of residues compared to the wave and reflow process. For conformal coated PCBAs, the contamination levels generated from the tested wave and selective soldering process are found to be enough to generate blisters under exposure to high humidity levels.
Technical Library | 2019-11-17 22:46:45.0
Overview of walk-in temperature and humidity chamber: It also belongs to environmental test equipment, it tests whether the product can resist high temperature, low temperature, humidity, or the physical and chemical changes produced under extreme conditions, the walk-in temperature and humidity chamber volume is large, the product is placed, or a large object can be placed, such as automobile, new energy, television and liquid crystal screen, etc. How to do the routine maintenance of the walk-in temperature and humidity chamber: 1. The wet gauze basically, if there is no special case, s/b usually changed once in 3 months 2. The water channel shall be regularly cleaned, including water cup, water tank, etc., so as to prevent the water from being blocked,affect the humidity test. 3. It is forbidden to test the flammable and explosive products inside working room. 4. Clean the chamber on a regular basis 2. How to operate walk-in temperature and humidity chamber: The operation method is same as standard temperature humidity test chamber,the controller is 7-inch LCD programmable color screen, you only need to setthe temperature point---test time--how many cycles need to be tested, This can be done automatically, and the machine will stop automatically when it is complete. If there is any problem during the operation, the corresponding problem point will be displayed on the machine control screen. Walk-in temperature and humidity chamber is a must equipment for reliability test of Automobile,Aerospace,Electronic parts,etc,the operation and maintenance are easy,it is teh tear down mahcine,Climatest engineers will be dispatched to do on-site support,for instance,we will finish commissioning,train customers how to operate,maintain,welcome to follow our company facebook page:https://www.facebook.com/Climatechambers
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