Development of ultra-thin surface mounting IC package (0.8 mm thick TQFP)

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Abstract
A TQFP (thin quad flat package) with a package size of 10*10 mm and a maximum package thickness of 0.8 mm has been developed to meet the need for lower profiles in surface-mounting packages. For a package thickness of 1.0 mm, the conventional lead-frame thickness and chip thickness are sufficient. However, when the package thickness is reduced to 0.8 mm, a reduction in at least one of the conventional thicknesses is absolutely essential. Therefore, by reducing the thickness of only part of the die-pad portion of the lead frame through the use of chemical etching to approximately 1/2 to 2/3, the resin thickness above the chip and below the die pad is ensured. A low-loop wire bond with a maximum of 0.14 mm was achieved by optimizing the wire material and wire-bond conditions. Ultrathin molding was achieved by improving the fluid characteristics of the resin and by ensuring the resin-fluid balance within the cavity. Package cracking and degraded moisture resistance were evaluated using a 4-Mbit mask ROM. After subjecting it to 85 degrees C and 75% RH for 72 h, no problems were noticed while soldering at 240 degrees C maximum with infrared reflow.<>

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