Techniques to Control Die Adhesive Paste Overflow for Thin Die-Reservoir
Original Publication Date: 2005-Dec-25
Included in the Prior Art Database: 2005-Dec-25
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The market is demanding for thinner and smaller semiconductor packages yet with higher functionality density per chip. As such, the thickness of the die is inevitable becoming thinner and thinner especially for multiple stacked dice package. To control Die Adhesive Paste overflow problem for thin die of less than 100 μm thickness is a challenge. Die Adhesive Paste overflow or excess of Adhesive reaches the top surface of active device can lead to the contamination of wire bond pads, consequently interfering with subsequent wire bonding operations, i.e. contaminate bonding tool, or even resulting in the loss of the function of the semiconductor die due to non-stick on pad failure (see Fig. 1). Up to now, there are many approaches being tried or under investigation to solve the Die Adhesive Paste overflow problem. One of the basic approaches to address Die Adhesive Paste overflow problem is to control and optimize the dispensing and bonding parameters, the dispensing tip diameters and dispensing paste volumes, the bonding force and time. This is rather difficult to achieve as the rheology of adhesives paste (a property which is critical to proper die attach processes) is time, pressure and temperature dependence. The rheology science of the adhesive paste itself is a difficult property to control needless to say when it is applied in mass production runs. To control the Die Adhesive Paste overflow, some create a physical cavity on the substrate to acts as a reservoir for the excessive Adhesive Paste. However, this solution may be more viable to Cavity-down BGA (Ball Grid Array) module.