초록 ▼

In its first aspect the invention provides an electromechanical acoustic transducer (5) which is resistively terminated at the rear with a closely-coupled sound absorber (7) made from an aerogel with good acoustic absorption at low frequencies. The invention also provides an aerogel suitable for thi

In its first aspect the invention provides an electromechanical acoustic transducer (5) which is resistively terminated at the rear with a closely-coupled sound absorber (7) made from an aerogel with good acoustic absorption at low frequencies. The invention also provides an aerogel suitable for this use and which is a conglomerate of small particles packed so that there are spaces left therebetween to allow the passage of sound. Moreover, the invention provides an aerogel suitable for this use and comprised of multiple layers (17a etc.) of materials of graded properties, or comprised of material of continuously varying properties throughout the thickness of the absorbing structure, in the principal direction of sound from the source.

대표청구항 ▼

In its first aspect the invention provides an electromechanical acoustic transducer (5) which is resistively terminated at the rear with a closely-coupled sound absorber (7) made from an aerogel with good acoustic absorption at low frequencies. The invention also provides an aerogel suitable for thi

In its first aspect the invention provides an electromechanical acoustic transducer (5) which is resistively terminated at the rear with a closely-coupled sound absorber (7) made from an aerogel with good acoustic absorption at low frequencies. The invention also provides an aerogel suitable for this use and which is a conglomerate of small particles packed so that there are spaces left therebetween to allow the passage of sound. Moreover, the invention provides an aerogel suitable for this use and comprised of multiple layers (17a etc.) of materials of graded properties, or comprised of material of continuously varying properties throughout the thickness of the absorbing structure, in the principal direction of sound from the source. ttachment, for example, including the original bonding pad on the chip or the bonding pads on the redistribution circuit above the chip. As integrated circuit design progresses and the level of integration continues to increase, the number of output pads in a chip also increases. Yet, surface area of the chip often remains identical or is reduced slightly. Under such circumstances, the conventional solder ball attachment technique can hardly accommodate fine solder balls. Ultimately, small fine pitch solder balls have to be used in the fabrication of WLCSP. Furthermore, the conventional solder ball attachment technique can be roughly classified into the automatic ball attachment method and the manual ball attachment method. The automatic ball attachment method costs more to operate especially for attaching small fine pitch solder ball. Although the manual ball attachment method is less expensive to operate, substantial labor force is required and overall ball attachment efficiency is relatively low. Since it is difficult to attach small fine pitch solder balls to the bonding pad of a chip in a WLCSP, a larger size bump is often attached to the bonding pad of the chip instead of a solder ball. Because lead-tin alloy has a good bonding strength as well as physical and conductive properties, lead-alloy is often used as a solder material for joining devices on a chip with contacts on the printed circuit board in the fabrication of integrated circuit packages. However, lead is a toxic material that often causes health hazards and environmental concerns. Thus, the electronic industry is actively looking for a lead-free substitute for the lead-containing solder material. At present, a number of lead-free solder materials