Электронная промышленность и полупроводниковые материалы
Технология измерения в электронной промышленности: печатные платы, компоненты поверхностного монтажа и полупроводники.
For most electronics applications it is prohibited to use solders that contain lead (RoHS and WEEE directives). However, the so-called tin whiskers that sometimes grow from the surface of unleaded solder can cause short circuits – posing an unacceptable risk for high reliability (“hi-rel”) applications in aerospace and military use. To prevent this defect, a minimum lead content of 3 wt% is specified for solder used in hi-rel applications. Because the consequences of failure could be so dangerous, these specifications must be verified through measurement of the lead content.
As the electronics industry makes use of ever thinner coatings, manufacturers increase their demands on measuring technologies to provide reliable parameters for product monitoring and control. The coating system Au/Pd/Ni is frequently used in the electroplating of leadframes, with CuFe2 (CDA 195) as substrate material. Typical coating thicknesses are between 3-10 nm Au and 10-100 nm Pd. For monitoring the quality of these coating systems, X-ray fluorescence instruments have established themselves as the measurement method of choice.
Bronze foils/strips are used for a huge variety of industrial applications, ranging from electrical contacts and membranes to spring elements and switches. The processing industry requires CuSn6 foils with more and more specific characteristics, e.g. significantly higher mechanical load-carrying capacity. To guarantee consistent quality, the mechanical characteristics of the foils must be determined.
Because EU directives like EU2002/95/EC and EU2002/96/EC prohibit lead and other heavy metals, the solderable coating systems used on printed circuit boards must now be lead free. However, immersion tin carries the risk that, due to diffusion processes, the usable tin remaining in the plating can be insufficient to guarantee the success of solder processes and the quality of solder joints. Therefore the thickness of the pure tin in the coating must be checked before soldering.
Due to growing restrictions on the use of lead in electronic products, efforts have been made to find appropriate substitutes. In the advanced IC packaging industry, the formerly ubiquitous, high-quality – but hazardous – eutectic SnPb solder bumps are now gradually being replaced by lead-free technology, such as SnAgCu alloy solder bumps. Because these new alloys require a certain composition in order to assure solderability and other mechanical properties, they must be measured precisely.
It is critical for manufacturers and distributors of many products to be able to detect harmful substances. Various regulations, such as RoHS (Restriction of Hazardous Substances), DIN EN 71 (Safety of Toys Standard) and CPSIA (Consumer Product Safety Improvement Act), specify maximum permissible values, particularly for heavy metals.
Modern printed circuit boards (PCBs) are furnished with a huge number of contact points for electrical connections, all of which are coated with metal. The metrological monitoring of these coated areas is imperative for precise process control. But especially for large-scale boards, manual positioning on these tiny measuring spots is simply unfeasible.
Determining the coating thickness of standard PCB applications must be fast, precise, non-destructive and cost effective. Ever-higher volumes of standard PCBs are being produced with ever-thinner coatings, often using precious metals and requiring testing on ever-smaller structures. Plus, to be suitable for this purpose any instrument must cope with further sample handling challenges such as flexible or oversized PCBs.
To prevent solder from bridging conductive traces and causing short-circuits, while undergoing the soldering process printed circuit boards (PCBs) are coated with a non-conductive lacquer to which solder will not adhere. This ‘solder mask’ also safeguards the board’s circuitry against environmental influences and improves electric strength. With so much depending on this important layer, it is obvious that its quality should be monitored during manufacture.
As electronic devices get smaller and smaller, conducting paths must be positioned even more closely together on printed circuit boards(PCBs). This is why, today, most PCBs are multilayered.In order to transfer electronic signals through to all the layers, these are connected byplated through-holes, also called vias (verticalinterconnect access), which are electroplated withan electrically conductive material such as copper.To ensure proper function, the hole lining must be uniform.
Conformal coating material is applied to electronic circuitry to act as protection against moisture, dust, chemicals, and temperature extremes. Coatings on assemblies which are too thin or totally uncoated and therefore non-protected board parts could result in damage or malfunction of the electronics.
As the electronics industry makes use of ever thinner coatings, manufacturers increase their demands on measuring technologies to provide reliable parameters for product monitoring. One example is the Au/Pd/Ni/Cu/printed circuit board system with coating thicknesses for Au and Pd of just a few nm. For monitoring the quality of these coating systems, X-ray fluorescence instruments have established themselves as the measurement method of choice.