Wafer level packaging process of semiconductor

[0002] 1. Field of the Invention

[0003] This invention relates to a packaging process of semiconductor, and more particularly to a wafer level packaging process of semiconductor.

[0004] 2. Description of Related Art

[0005] After completing the manufacturing of semiconductor devices on the wafer, the conventional packaging process is to perform a die sawing step in order to cut the wafer into many dies, then to perform packaging process respectively so as to form various types of IC packages. However, since the semiconductor devices formed on the wafer are very tiny in size, they are subject to damage resulted from die handling, small particles in the air, moisture and airflow etc.

[0006] The foregoing problems are resulted from the process that performs packaging process after the dies are cut from the wafer. A conventional way to resolve the problems is to perform the wafer level process first before performing the die sawing process. Additionally, the package size of the wafer level packaging is closed to that of the die, thereby the size of the package can be greatly reduced which meet the current requirements of “Light, Thin, Short, and Small” in packaging design.

[0007] However, the conventional wafer level packaging processes consisting of processes such as flux coating on the carrier of the wafer, and solder-ball planting etc. are apt to damage the surface of the wafer or contaminate the devices. Moreover, since the flux coated on the carrier is hard to get rid of, thereby, the flux is apt to remain on the wafer. The residual flux on the wafer will affect the electrical performance of the semiconductor products, and consequently will reduce the yield and increase the manufacturing cost.

[0008] Therefore, the present invention provides a wafer level packaging process of semiconductor. The process is described as follows: First of all, it is to provide a substrate, having a first surface and a second surface wherein the substrate is constituted by a plurality of carriers densely disposed is series. And each of the carriers has an opening located at the center portion of the carrier, and a plurality of bonding fingers is disposed on the second surface at the periphery of the opening. Also, a plurality of connecting points is disposed on the outer edges of the bonding fingers that are electrically connected to the connecting points. Next, to provide a wafer constituted by a plurality of dies wherein an active surface of the die has a plurality of bonding pads. Then, to provide an adhesive layer in order to bond the first surface of the substrate to the active surface of the die wherein each of the carriers corresponds to each of the dies, and the bonding pads are corresponding to the openings of the carriers. Thereafter, to perform a wire bonding process in order to form a plurality of bond wires to make electrical connections between the bonding pads of the dies and their corresponding bonding fingers of the carriers. Subsequently, to perform an encapsulating process by using a molding compound to fill the openings and to encase the bond wires, the bonding pads, and the bonding fingers. Finally, to perform a die sawing process in order to form a plurality of complete packages of a wafer level packaging.

[0009] In accordance with a preferred embodiment of the present invention, the process for forming connecting points comprises bumps formed by electroplating and electro-plateless process or solder balls formed by solder-ball planting wherein the bumps are balls or flat plates in shape. Besides, the material of the connecting points comprises a tin-lead alloy having high percentage of content in lead and having relatively high melting point.

[0010] In the process of the present invention, the dies are bonded to the carriers after the bumps are formed on the carriers, thereby, the die are protected from being contaminated and damaged, consequently, the yield can be improved and the manufacturing cost can be lowered.

[0011] The objectives, characteristics, and advantages of the present invention can be more fully understood by reading the following detailed description of the preferred embodiments, with reference made to the accompanying drawings as follows:

[0012] FIG. 1A to FIG. 1E are cross-sectional views illustrating the process flow of a wafer level packaging of a preferred embodiment according to the present invention.

[0013] FIG. 2 is a partial top view of the carrier shown in FIG. 1A of the present invention.

[0014] FIG. 3 is a cross-sectional view of an another bump of the present invention.

[0015] FIG. 1A to FIG. 1E are cross-sectional views illustrating the process flow of a wafer level packaging of a preferred embodiment according to the present invention while FIG. 2 is a partial top view of the carrier. As shown in FIG. 1A and FIG. 2, a substrate 100, which is constituted by a plurality of carriers 104 densely disposed in series, is provided. The substrate 100 has a first surface 120aand a second surface 120b.A scribe line 110 is set up between each of the two adjacent carriers 104, and each of the carriers 104 has an opening 102 at its center portion. A plurality of bonding fingers 109 is disposed at the periphery of the opening 102 on the second surface 120bwhile a plurality of connecting points 108 is disposed on the outer edges of the bonding fingers 109. The bonding fingers 109 and the connecting points 108 are electrically connected by the conductive traces (not shown) respectively. The material used by the substrate 100 can be a soft substrate such as polyimide and a scroll tape type of carrier formed by laminated copper foil or hard substrate such as a common laminated board for example.

[0016] Besides, an adhesive layer 106 is formed on the first surface 120aof the substrate 100. The ways of forming connecting points 108 on the carrier 104 includes using an electroplating method, or an electro-plateless method. These methods are used to form a bump on the carrier 104 or a solder planting method is used to form a solder ball on the carrier 104 wherein the bump and the solder ball are electrically connected to the circuit board in the subsequent process. The shape of the solder ball can be either in ball shape as shown in FIG. 1A or in the shape of a flat plate as shown later in FIG. 3. Moreover, the material of the connecting points 108 has relatively high melting point to prevent the connecting points 108 from being deformed under high temperature in the subsequent wire bonding process. This kind of material comprises a tin-lead alloy having high percentage content in lead. In additions, the package of the present invention can be reworked easily due to the fact that the connecting point has very high melting point.

[0017] The conventional wafer level packaging forms connecting points or performs solder-ball planting on the carrier after the die is bonded to the carrier. However, since these processes for forming, connecting points or planting solder balls includes also a series of cleaning and thermal processes, thereby, the dies are subject to be contaminated or damaged. Consequently, the yield of the products will be lowered and the cost will be relatively high.

[0018] Besides, as mentioned above, since the present invention forms the connecting points on the carrier 104 first, then bonds the dies to the carrier 104 in the subsequent process, it can protect the die from being contaminated or damaged, thereby, can improve the yield and lower the manufacturing cost.

[0019] For the next step as shown in FIG. 1B, the carrier 104 is bonded to the active surface 112aof a wafer 112 through the adhesive layer 106 on the substrate 100. There are electric circuits (not shown) formed on the active surface 112aof the wafer. A bonding pad 112bwhich is disposed at the center of the opening 102 of the carrier 104 is formed also on the active surface 112aof the wafer 112, and the bonding pad 112bis electrically connected to the outside connectors.

[0020] For the next step as shown in FIG. 1C, a wire bonding process is perform by using bond wires 114 to make an electrical connection between the bonding pads 112bon the wafer 112 and the bonding fingers 109 on the carrier 104.

[0021] In the subsequent step as shown in FIG. 1D, an encapsulating process is performed by using a molding compound 116 to encase the bonding pad 112bformed on the active surface 112a,the bonding fingers 109 formed on the carrier 104, and the bond wire 114. The encapsulating process can employs methods such as molding screen printing, or dispensing (also called globe top).

[0022] Finally, a die sawing process as shown in FIG. 1E is performed to cut the wafer 118 along the scribe lines 110 into many packages 118 that complete a wafer level packaging.

[0023] The invention has been described using an exemplary preferred embodiment. However, it is to be understood that the scope of the invention is not limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements. The scope of the claims, therefore, should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.