FIELD OF THE INVENTION

The present invention relates in general to semiconductor devices and, more particularly, to methods and devices for reducing metal burrs when sawing semiconductor packages.

BACKGROUND OF THE INVENTION

Semiconductor devices are commonly found in modern electronic products. Semiconductor devices perform a wide range of functions such as signal processing, high-speed calculations, transmitting and receiving electromagnetic signals, controlling electronic devices, transforming sunlight to electricity, and creating visual images for television displays. Semiconductor devices are found in the fields of communications, power conversion, networks, computers, entertainment, and consumer products. Semiconductor devices are also found in military applications, aviation, automotive, industrial controllers, and office equipment.

Semiconductor devices commonly include semiconductor packages with shielding layers to block electromagnetic interference (EMI).FIG. 1illustrates one topology of a semiconductor package100having a conformal shielding layer. The package is based on a unit substrate110having conductive layers112,114,116, and118interleaved between insulating layers120. Conductive layers112,114,116, and118include contact pads and conductive traces as necessary to implement the desired signal routing. Conductive vias122are formed between any of the conductive layers112-118to provide vertical signal routing.

Package100is formed on unit substrate110by mounting any desired electrical components, e.g., semiconductor die124, onto the substrate. Semiconductor die124includes an active surface130with contact pads132. Contact pads132are electrically and mechanically connected to conductive layer118of unit substrate110by solder bumps134. An encapsulant or molding compound138is deposited over unit substrate110and semiconductor die124for physical support and environmental protection. Solder bumps144are formed on conductive layer112for subsequent integration of package100into a larger electrical system.

An EMI shielding layer150is formed over unit substrate110and encapsulant138. Conductive layer112extends from one or more bumps144to the edge of unit substrate110. EMI shield150contacts the outside ends of conductive layer112, which connects the EMI shield to ground through bumps144. Conductive layer112includes a ground plane in some embodiments with openings in the ground plane for signal contact pads.

FIGS. 2a-2dillustrate a method of forming semiconductor package100.FIG. 2ashows a partial cross-section of substrate strip160with several semiconductor die124mounted on the substrate strip and separated by saw streets166. Conductive layer112includes ground plane112a, bridges112b, and contact pads112c.FIG. 2bis a simplified view of the bottom of substrate strip160showing ground plane112aand bridges112b. Contact pads112cfor electrical interconnect are formed in openings of, or outside the footprint of, ground plane112ato electrically isolate the signal paths from ground.

Conductive layer112is made continuous across each unit by having bridges112bconnecting adjacent ground planes112ato each other. That way, when the panel is singulated as shown inFIGS. 2cand 2d, bridges112bare exposed at side surfaces of unit substrates110for connection to EMI shield150. However, the physical movement of saw blade170against the material of conductive layer112causes some of the material to move out of the saw's kerf without being physically separated from the conductive layer, forming burrs174.

Burrs174are caused by the mechanical load of saw170moving metal from conductive layer112, due to ductility of the material, without fully removing the metal from the unit substrates110. Burrs174can extend to nearby conductors and cause a short circuit to ground, potentially resulting in part failure. There are also many other potential reliability problems when burrs174are present. Moreover, some of the material of conductive layer112is pushed laterally out of saw streets166, resulting in a thickening of the conductive layer around the edges of the device.

Many reliability issues exist for substrates that have ground conductors exposed at saw streets for connection to EMI shielding. Therefore, a need exists for improvements to EMI shielding.

