MicroTEC (Germany)

ABSTRACT Optimising raw material use in the sawing process requires understanding variations in quality indicators. Cracks are defects that significantly reduce product value and can lead to the downgrading of the product. This study aimed to characterise heart crack variability in softwood stems before sawing and improve wood inspection. 1026 Norway spruce (Picea abies (L.) H. Karst.) and silver fir (Abies alba Mill.) stems were scanned using an industrial CT Log X-ray scanner. Among these, 250 stems exhibited heart cracks longer than 50 cm: 37% in silver fir and 18% in Norway spruce. Radial and longitudinal variability of crack metrics were analysed. Results confirm that internal cracks are present in approximately 25% of stems before sawing, with heart cracks length averaging 32% of total stem length. A significant positive linear relationship (R2 ≈ 0.28) was identified between heart crack length, stem diameter and taper. This suggests that factors associated with larger stem dimensions may contribute to increased crack length. These findings are crucial for the wood industry, enabling better crack management, minimising defects in end products and optimising yield and value. Further research on the relationship between silvicultural treatments and the formation of internal cracks is recommended.

Compared with classic solder flip chip technologies, the use of isotropic conductive adhesive for bumping and assembling results in a number of advantages such as a simple yet versatile process, lower temperatures and environmental friendliness. The polymer flip chip (PFC/sup TM/) technology requires suitable bond pads. The commonly used aluminum alloys result in unstable contacts for the conductive adhesives and hence there is an urgent need for an additional under-bump metallization for the PFC/sup TM/ technology. KSW Microtec has developed a technology which is based on electroless deposition of palladium. The metallization is executed as a back end process. The bond pads are deposited with a homogeneous and pin-hole free Pd thin film with a thickness of about 1 /spl mu/m without significant reduction of the Al bond pad metallization. The deposited film surface does not require flash gold metallization because of the noble characteristics of palladium. This simplifies the process in comparison to the well known Ni/Au process. The contact resistance between conductive adhesives and palladium metallization are equal to or better than gold/adhesive interconnections. As an example of the versatility of the PFC/sub TM/ technology, products manufactured by KSW Microtec include chip on dycostrate, chip on flex with screen printed polymer tracks, and smart cards. Experiences with the set-up and qualification of PFC/sup TM/ technology at KSW Microtec are also discussed.