Technical Library | 2023-09-23 22:31:52.0
Dry boxes can be implemented at various points within the Mfg. environment; for med-long term inventory, or for short term handling on the production floor, and in some cases (with certain conditions) as a process replacement for baking. Bare boards, raw components and partially assembled PCB's can benefit from ultra-low humidity storage.
Technical Library | 2019-12-30 02:09:39.0
How to choose the material of PCB ? The choice of PCB material must meet the design requirements, the quality of production and cost need to achieve a balance. The design requirements include electrical and institutional parts. This material problem is usually important when designing very high speed PCB boards (frequencies greater than GHz). For example, the commonly used FR-4 material may not be used when dielectric loss at several GHz frequencies, which can have a significant effect on signal attenuation . In the case of electrical, it is important to note whether the dielectric constant and the dielectric loss are combined at the designed frequency
Technical Library | 2008-12-11 01:15:56.0
Flame retardants have been around since the Egyptians and Romans used alum to reduce the flammability of wood. Brominated flame retardants (BFRs) first experienced use after World War II as the substitution of wood and metal for plastics and foams resulted in materials that were much more flammable. The widespread use of BFRs initiated in the 1970s with the explosion of electronics and electrical equipment and housings. For the US market, all of these products must conform to the UL 94 flammability testing specifications. In fact, the most common printed circuit board (PCB) in the electronics industry, FR-4, is defined by its structure (glass fiber in an epoxy matrix) and its compliance to UL 94 V0 standard.
Technical Library | 2013-05-16 15:52:00.0
In response to a growing concern within the Electronic Industry to the transition to Halogen-Free laminates (HFR-Free) within the Client Market space (Desktop and Notebook computers) iNEMI initiated a HFR-Free Leadership Workgroup to evaluate the readiness of the Industry to make this transition. The HFR-Free Leadership WG concluded that the electronic industry is ready for the transition and that the key electrical and thermo-mechanical properties of the new HFR-Free laminates can meet the required criteria. The HFR-Free Leadership WG verified that the laminate suppliers can meet the capacity demands for these new HFR-Free laminates and developed a "Test Suite Methodology" (TSM) that can facilitate the comparison and choice of the right laminate to replace brominated FR4 in the Client space... First published in the 2012 IPC APEX EXPO technical conference proceedings.
Technical Library | 2018-09-21 10:12:53.0
Moisture accumulates during storage and industry practice recommends specific levels of baking to avoid delamination. This paper will discuss the use of capacitance measurements to follow the absorption and desorption behaviour of moisture. The PCB design used in this work, focused on the issue of baking out moisture trapped between copper planes. The PCB was designed with different densities of plated through holes and drilled holes in external copper planes, with capacitance sensors located on the inner layers. For trapped volumes between copper planes, the distance between holes proved to be critical in affecting the desorption rate. For fully saturated PCBs, the desorption time at elevated temperatures was observed to be in the order of hundreds of hours. Finite difference diffusion modelling was carried out for moisture desorption behaviour for plated through holes and drilled holes in copper planes. A meshed copper plane was also modelled evaluating its effectiveness for assisting moisture removal and decreasing bake times. Results also showed, that in certain circumstances, regions of the PCB under copper planes initially increase in moisture during baking.
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