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Solders, Metallizations, and Conductive Inks
December 14, 2009 |Estimated reading time: 3 minutes
— These new solders, metallization formulas, and other conductive materials meet current SMT industry needs for finer-pitch paste print, and lead- and halogen-free PCB assembly.Zero Halogen Solder Paste
Multicore HF108 is a lead-free, halogen-free solder paste with zero deliberately added halogens. It has reflow and stability characteristics normally associated with halogen-containing materials. Benefits include high-speed print capability, a stable shelf-life of up to six months when refrigerated or four weeks at room temperature and a wide process window. Henkel Corporation, www.henkel.com/electronics
Halogen-free, Fine-pitch Solder Pastes
These two solder pastes are developed by Koki Company Ltd. (Tokyo, Japan). S3X58-M650 is an ICT-testable, halogen-free product that uses the SAC 305 alloy. Properties include low voiding, high print speeds, and fine-pitch (micro-BGA, 0.4-mm pitch) capability. S3X70-M407 is a lead-free no-clean solder paste for ultra-fine-pitch applications. Using a Type 5 powder, S3X70-M407 solder paste has been formulated for 0.2-mm-pitch micro-BGA devices, as well as 0402 (01005) components. Features include excellent wetting in air environments and low voiding. Christopher Associates, www.christopherweb.com
Fine-pitch Printable Solder Paste
Multicore LF730 is a lead-free solder paste based on the Multicore DAP Plus Type 4 solder powder and an innovative flux medium that allows for greater process range. Multicore LF730 enables robust high-speed printing even for extremely fine parts, printing thorough apertures as small as 160 µm in diameter and stencils as thin as 80 µm. The proprietary particle size distribution of the paste delivers more solder per aperture, but with less risk of aperture clogging as compared to traditional Type 4 pastes. The improved packing efficiency ensures greater volume through the aperture and consistent volume release of over 90%. Multicore LF730 provides excellent wetting ability to a wide range of surface finishes. The paste has shown consistent performance in environments as warm as 30°C at 84% relative humidity (RH). Benefits include good open and abandon time, allowing two to three hours on 225-µm apertures, standard refrigeration storage, a six-month shelf life, and good hot slump resistance, printing very narrow geometries without any bridging. Coalescence is good, producing smooth, shiny finish on solder joints. Henkel, www.henkel.com/electronics
Lead-free No-clean Solder Paste
NL930 is a lead-free, no-clean solder paste that is designed for ease of print and reflow. It offers good solderability in difficult wetting requirements. It also improves stencil life and cosmetics, particularly when using SN100C. Post-reflow flux residues are penetrable for pin testability. NL930 is compatible with SN100C and SAC alloys with Type 3, 4 and 5 solder meshes. It suits boards with OSP, ENIG, Immersion Silver, and Immersion Tin finishes. Results include IPC 7095 Class III resistance to voiding using straight ramp or soak reflow profiles, higher reliability properties, halide-free material graded RELO, and a reduction in random solder balling levels. It has more than eight hours of print life. The paste also features high-volume repeatability with 16 mm pitch QFP pads and 12 mm circles, as well as excellent response to one-hour pause, after two knead strokes at 35-65% RH. FCT Assembly, www.fctassembly.com.
Flexible High-temperature Electrically Conductive Ink
Based on the 102-32 silver-filled conductive silicone adhesive, 125-19 is a screen-printable silicone conductive ink. With lower viscosity and smaller particle size, the ink can be used in a wide variety of production modes and expanded range of applications. Due to its silicone properties, 125-19 is flexible, resistant to high temperatures, and can be used with such substrates as Kapton, Teflon, and rubber surfaces. Formulated to be screen printed, 125-19 can also be syringe-dispensed, dipped, and sprayed and suits use with ceramic, glass, and silicone substrates. The ink offers an overall balance of peel strength, cohesion, lap shear strength, and high-temperature holding-power. Applications include EMI/RFID shielding, polymer thick film circuitry, and electrical attachments for stress-sensitive devices. It is reportedly fast-curing, highly conductive, tough, and environmentally friendly. Produced as a smooth paste, silicone products enable complete fill-in around complicated contours and provide electrical conductivity and resistance to stress. Creative Materials, Inc., www.creativematerials.com
Metallization Pastes for Solar Assemblies
These three metallization pastes for photovoltaic cell manufacturing are from Giga Solar Materials Corporation (Hsinchu, Taiwan, R.O.C.). The three pastes include A-108, A-568, and A-368. The A-108 aluminum paste is printed as a back electrode on single or polycrystalline silicon solar cells, while the A-568 lead-free silver front-side paste is used for back contact on silicon solar cells. The A-368 high conductivity back surface paste offers excellent adhesion to aluminum. All three pastes have been formulated for adhesion and electrical performance. Christopher Associates, www.christopherweb.com