Adhesive die attachment method for a semiconductor die and arrangement for carrying out the method

#This invention relates to a method and a device for attaching a semiconductor die to a substrate in a manner that an electrical short to the PN junction of the semiconductor die is prevented.

#Die attaching forms an integral part of a semiconductor chip packaging process. Die attaching or die bonding is the process of mounting a semiconductor die or chip onto a substrate and this process is well established in the field of semiconductor device manufacturing.

#One purpose of the die attaching process is to create a strong physical bond between the die and the substrate of the package. However, it also serves to provide either an electrical conducting or insulating contact between the die and the substrate. There are different known die attaching methods, such as eutectic die attachment, soldering die attachment and adhesive die attachment. The choice among the different die attaching methods in a particular case depends on factors like the size of the semiconductor die, the substrate material and the operating conditions of the final device.

#FIG. 1 shows the excess adhesive forming a fillet around a die, wherein a die attaching method according to the prior of the art is used;

#FIG. 2 shows the excess adhesive causing an electrical short circuit to a die with a low PN junction, wherein a die attaching method according to the prior of the art is used;

#FIG. 3a shows the deposition of conductive adhesive on a substrate according to a preferred embodiment of the invention;

#Preferred embodiments of the adhesive attaching method for attaching a semiconductor die to a substrate according to the invention is shown in, and described in the following with reference to FIG. 3a to FIG. 3h.

#A drop of adhesive 200 is deposited onto a substrate 201 such as a leadframe, a ceramic, glass or flexible circuit board, or a plastic or printed circuit board (PCB), using a dotting, stamping or dispensing process as shown in FIG. 3a. The adhesive may also be deposited on the substrate 201 using a silk-screening, stencilling or ink-jet process.

#According to the preferred embodiment of the invention, the adhesive 200 is formulated from epoxy thermoset resins, thermoplastic resins or silicone. The epoxy is either a one-component or a two-component epoxy formulation consisting of resin as the first component and a catalyst hardener as the second component. The epoxy is also mixed with a metallic filler material to enable the adhesive to be electrically conductive. In this preferred embodiment of the invention, the metallic filler material used is silver.