Chip package and manufacturing method thereof

[0001] 1. Field of the Invention

[0002] The present invention relates to a semiconductor device, and more particularly to a chip package.

[0003] 2. Description of Related Art

[0004] Electro-magnetic interference (EMI) is a serious and challenging problem for most electronic devices or systems. As EMI disturbances commonly interrupt, degrade or limit the effective performance of the electronic device or the whole circuit of the electronic system, it is necessary for the electronic devices or systems to have efficient EMI protection to ensure the effective and safe operation.

[0005] EMI protection is particularly important in small-sized, densely packaged or sensitive electronic applications operating at high frequencies. Conventionally, EMI shielding solutions typically involve the use of metal plates and/or conductive gaskets, which are later attached or affixed at higher manufacturing costs.

[0006] In view of the foregoing, the present invention provides a manufacturing method of a chip package, which offers better design flexibility with less effort.

[0007] The present invention is further directed to a chip package with enhanced effectiveness of EMI shielding.

[0008] The present invention provides a chip package including a substrate, at least a chip disposed on the substrate, a molding compound and a shielding layer conformally covering the molding compound. The top edges of the molding compound are blunt or rounded. The shielding layer conformally covers the top edges of the molding compound and a top surface and sidewalls of the molding compound, and the shielding layer is electrically connected to the semiconductor substrate.

[0009] The invention further provides a manufacturing method of a chip package. At least a chip is disposed on one of the substrate units of the matrix substrate, and the chip is electrically connected to the substrate unit. After forming a molding compound over the matrix substrate to encapsulate the chips, portions of the substrate units, a grinding process and a singulation process are performed to the molding compound. Later, a shielding layer is formed over the molding compound to conformally cover the molding compound of each chip packages.

[0010] According to one embodiment of the present invention, the grinding process can be performed before or after the singulation process. Also a half-cutting process may be further performed before or after the grinding process. The grinding process may comprise an oblique disc grinding process or a rounding grinding process.

[0011] According to one embodiment of the present invention, the shielding layer and the connectors are formed from a conductive material by a spraying process, a sputtering process or a plating process.

[0012] According to the embodiments of the present invention, the grinding process makes the top edges of the molding compound blunt or rounded, so that the later formed shielding layer can smoothly covers the top edges or corners of the molding compound of individual chip packages, without the crevices.

[0013] Herein, the crevices often occurring at the orthogonal corners or edges of the shielding layer can be avoided, and the shielding layer can uniformly cover the molding compound of the chip package and provide effective EMI shield of the chip package. According to the present invention, owing to the complete coverage of the shielding layer, the reliability of the package and the shielding efficacy can be improved.

[0014] In order to the make the aforementioned and other objects, features and advantages of the present invention comprehensible, several embodiments accompanied with figures are described in detail below.

[0020] Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.

[0021] The manufacturing methods as described in the present invention can be used for fabricating various package structures and are more suitable for fabricating stacked type packages, multiple-chip packages, or high frequency device packages (including radio frequency device packages).

[0022] FIGS. 1A through 1G are schematic views showing a manufacturing method of the chip package according to the preferred embodiment of the present invention. FIG. 1D′ and 1D″ are exemplary three-dimensional schematic views showing the structure of FIG. 1D having grinding trenches of enlarged view A or B.

[0023] Referring to FIG. 1A, a matrix substrate 100 having a plurality of substrate 102 (defined by the subsequent sawing lines shown as dotted lines) is provided, while each substrate 102 includes a plurality of contacts 104 thereon and at least a ground via 108 therein. The contacts 104 function as bump pads for flip chip connecting technology. The substrate 100 can be a laminate substrate, for example, a printed circuit board (PCB). Currently achievable designs of the ground via 108 within the substrate 102 are considered encompassed within the present invention. For a laminate substrate, the ground via may extend through the whole substrate (i.e. from the top surface to the bottom surface), or extend from the top or bottom surface to an inner layer thereof, or extend between two inner layers of the substrate. The size of the ground via may be adjusted according to electrical properties of the product, the ground via/plug may be formed from the plated through-hole, or slot hole filled with solder materials. Further, the ground via can be replaced by a ground pad with a conductive solder mass disposed on the upper surface of the substrate.

[0024] Referring to FIG. 1B, at least a chip 120 is disposed on the top surface 102a of each substrate 102. Although a chip is provided herein, other surface mount components can be employed, and encompassed within the scope of this invention. The chip 120 is electrically connected to the contacts 104 of the substrate 102 through a plurality of bumps 106 there-between. Although flip chip connecting technology is described herein, it is well encompassed within the scope of this invention to employ wire bonding technology (i.e. through wire connections). The chip 120 preferably is disposed within a central portion of the substrate 102.

[0025] Referring to FIG. 1C, a molding process is carried out to form a molding compound 130 on the matrix substrate 100 to encapsulate the chips 120, the contacts 104, the bumps 106 and at least a portion of the substrate 102. The molding process can be an over-molding process, for example. The material of the molding compound 130 may be epoxy resins or silicon resins, for example.

[0026] Referring to FIG. 1D, a grinding process is performed to form a plurality of grinding streaks (grinding trenches) 135 by removing portions of the molding compound 130. The grinding streaks 135 are arranged surrounding the location of the chip 120. Preferably, the grinding streaks 135 within the molding compound 130 are arranged right above the boundary or perimeter of each substrate 102. FIGS. 1D′ or 1D″ is the 3D schematic view of the structure depicted in FIG. 1D having the grinding trenches of the enlarged view A or B. As shown in FIGS. 1D and 1D′, the individual grinding streaks 135 are arranged right on the boundary lines (the dotted lines) of the substrate 102. In this case, the subsequent sawing process will cut through the grinding streaks 135 arranged at the sawing lines (shown as dotted lines). The grinding process may include an oblique disc grinding process, for example. For the oblique disc grinding process, grinding disc with slanted blade cuts into the molding compound to form sloping trenches. Taking the grinding streaks 135 arranged right above the boundary of each substrate 102 as an example, the grinding process may cause a ring-shaped trench within the molding compound 130, along the boundary of each substrate 102.

[0027] In details, as shown in FIGS. 1D, 1D′ & 1D″, the grinding streak 135 is preferably a loop trench having a reverse-hat cross-section (i.e. the trench being narrower at the bottom portion but wider around the top portion). In other words, the grinding process makes the top edges 130e of the molding compound 130 non-orthogonal or non-right-angular. Preferably, the grinding process makes the top edges 130e of the molding compound 130 blunted. The top edges 130e of the molding compound 130 either have one obtuse angle θ₁ (as shown in the enlarged view A), or two obtuse angles θ₂, θ₃ (as shown in the enlarged view B). For example, the obtuse angle θ₁ (between the beveled surface 135a of the grinding streak 135 and the top surface 130a of the molding compound 130) ranges between about 95-165 degrees, while the obtuse angle θ₂ (between the beveled surface 135a and the beveled surface 135b of the grinding streak 135) or the obtuse angle θ₃ (between the beveled surface 135b of the grinding streak 135 and the top surface 130a of the molding compound 130) ranges between about 100-160 degrees, for the grinding streaks 135. Preferably, the grinding depth d ranges approximately from ⅕ to ⅓ of the thickness D of the molding compound 130. In general, the sizes or the depth of the grinding streaks 135 can be altered depending on the shielding requisites or other electrical properties of the package or even varied in accordance with the processing parameters.

[0028] Referring to FIG. 1E, an optional half-cutting process is performed to remove portions of the molding compound 130, until the top surface 102a of the substrate 102 is partially exposed. In general, the half-cutting process cuts through the grinding streaks 135 arranged on the sawing lines and cuts through the molding compound 130 into the matrix substrate 100 for a pre-determined depth, to form a plurality of trenches 137. Preferably, the cutting width a of the half-cutting process (i.e. the width a of the trenches 137) is smaller than the width A of the grinding streak 135 (i.e. the grinding width A of the grinding process). In this case, even after the half-cutting process, the blunted edges 130e of the molding compound 130 are retained. The location or arrangement of the ground via can be varied according to product requirements. One exemplary location of the ground via is positioned right on the sawing lines, and the half-cutting process or the singulation process may cut through the ground via. In FIG. 1E, the half-cutting process cuts into the ground via 108 arranged on the sawing lines. Although the half-cutting process is performed after the grinding process according to the present embodiment, it is acceptable to perform the half-cutting process prior to the grinding process. When the half-cutting process is performed prior to the grinding process, the subsequent grinding process can still blunt the top edges of the half-cut molding compound.

[0029] Finally, referring to FIG. 1F, a shielding layer 140 is formed over the molding compound 130 to conformally cover the top surface 130a, the sidewalls 130b and the top edges 130e of the molding compound 130. The shielding layer 140 can be formed by depositing a metal material (not shown) to conformally cover the molding compound 130 and the matrix substrate 100 exposed by the trenches 137 using a spray coating method, a plating method, or a sputtering method, for example. The metal material can be, for example, aluminum, copper, chromium, gold, silver, nickel, solder materials, or the combinations thereof.

[0030] In principle, the top edges of the molding compound are neither acute-angled nor right-angled, which is prone to poor coating quality (e.g., formation of crevices). Because the top edges 130e of the molding compound 130 according to the present invention are either obtuse or rounded, either the coverage or the conformity of the shielding layer 140 is greatly improved. As much less or no crevices exist in the shielding layer, owing to the uniform coverage of the shielding layer at the corners or edges, the shielding efficacy of the shielding layer is enhanced and the reliability of the package is improved.

[0031] Referring to FIG. 1G, from a bottom surface 102b of the matrix substrate 100, a singulation process is performed to cut at the sawing lines and cut through the matrix substrate 100, so as obtain the individual chip packages 10. The singulation process may be a blade sawing process or a laser cutting process, for example.

[0032] In accordance with the present invention, the manufacturing methods of the chip package shown in FIGS. 1A through 1G may be further modified and described in the following embodiments. Alternatively, following the process steps of FIGS. 1A-1C, as shown in FIG. 2A, a singulation process is performed to cut through the molding compound 130 and the matrix substrate 100 along the sawing lines, so as obtain the individual chip packages 10. The singulation process also cuts through the ground via 108 within the matrix substrate 100. The singulation process may be a blade sawing process or a laser cutting process, for example. The boundary regions between the top surface 130a and the sidewalls 130b of the molding compound 130 are denoted as the top edges 130e of the molding compound 130 herein. As shown in FIG. 2A, the top edges 130e of the molding compound 130 are substantially right-angled after singulation.

[0033] Later, referring to FIG. 2B, a grinding process is performed to blunt the top edges 130e of the molding compound 130 of the singulated packages 10. As the singulation process cuts through the sawing lines, the grinding process is performed toward the top edges 130e of the molding compound 130 right above the boundary or perimeter of each substrate 102. As described herein, the top edges 130e are substantially right-angled before grinding, and the grinding process turns the top edges 130e of the molding compound 130 to blunt or rounded top edges 130e. The grinding process may include an oblique disc grinding process or a rounding grinding process, for example. As shown in FIG. 2B, the top edges 130e of the molding compound 130 become rounded after the grinding process. However, according to the embodiments of this invention, the top edges 130e of the molding compound 130 can be either blunted (i.e. having at least one obtuse angle as shown in the enlarged views A-B of FIG. 1D), or rounded (i.e. having curved profiles as shown in the enlarged view at the top of FIG. 2B). Also, the angle or curvature of the blunted or rounded top edges can be varied according to the processing parameters.

[0034] Following FIG. 2B, as shown in FIG. 2C, a shielding layer 140 is conformally formed over the molding compound 130 to cover the top surface 130a, the sidewalls 130b and the rounded top edges 130e of the molding compound 130. The shielding layer 140 can be formed by depositing a metal material (not shown) to cover the molding compound 130 and sidewalls of the singulated substrate 102 using a spray coating method, a plating method, or a sputtering method, for example.

[0035] In other words, since the shielding layer 140 conformally covers the obtuse or rounded top edges 130e of the molding compound 130, as shown in the enlarged partial view at the top of FIG. 2C, the resultant shielding layer 140 also has obtuse or rounded top edges 140e (i.e. smooth profiles right above the top edges 130e of the molding compound 130).

[0036] FIG. 3 is a cross-sectional view of a chip package according to a preferred embodiment of the present invention. Referring to FIG. 3, the chip package 30 of the present embodiment includes a substrate 102, a plurality of contacts 104, a plurality of bumps 106, at least a chip 120, a molding compound 130 and a shielding layer 140. The substrate 102 can be a laminated substrate, for example, a two-layered or a four-layered laminated PCB substrate. The chip 120 can be a semiconductor chip, for example, a radio-frequency (RF) chip. The material of the shielding layer 140 may be copper, chromium, gold, silver, nickel, aluminum or alloys thereof or even a solder material, for example. The chip 120 is electrically connected to the substrate 102 through the contacts (bump pads) 104 and the bumps 106. The molding compound 130 encapsulates portions of the substrates 102, the bumps 106, and the chip 120. As shown in FIG. 3, the shielding layer 140 is disposed over the molding compound 130, covering the top surface 130a, the sidewalls 130b and the blunted top edges 130e of the molding compound 130. The boundary regions between the top surface 130a and the sidewalls 130b of the molding compound 130 are denoted as the top edges 130e of the molding compound 130 herein, and the detailed profile of the blunted top edges 130e of the molding compound 130 is similar to the enlarged view B of FIG. 1D. As the half-cutting process cut through the molding compound 130 along the sawing lines before the formation of the shielding layer 140, the molding compound 130 are fully covered by the shielding layer and will not be exposed from the chip package 30. The shielding layer 140 is electrically connected to the substrate 102 through the direct contact with at least a ground vias 108 of the substrate 102, and the shielding layer 140 is electrically grounded through the ground via 108. Hence, taking advantage of the metal traces or vias of the substrate, the shielding layer of the present invention can be grounded within the package structure using the ground plane of the substrate. The shielding layer can establish an electrical ground path within the package structure, devoid of using an extra ground plane.

[0037] FIG. 4 is a cross-sectional view of a chip package according to another preferred embodiment of the present invention. Referring to FIG. 4, the chip package 40 is mostly similar to the package structure of FIG. 3, except the rounded top edges 130e of the molding compound 130. The detailed profile of the rounded top edges 130e of the molding compound 130 is similar to the enlarged view of FIG. 2B. As the singulation process cut through the molding compound 130 and the matrix substrate along the sawing lines before the formation of the shielding layer 140, the sidewalls of the substrate 102 and the molding compound 130 are fully covered by the shielding layer and will not be exposed from the chip package 40. The shielding layer 140 is electrically connected to the substrate 102 through the direct contact with at least a ground plug/solder-filled slot hole 108 of the substrate 102, and the shielding layer 140 is electrically grounded through the ground plug/solder-filled slot hole 108.

[0038] FIG. 5 is a cross-sectional view of a chip package according to another preferred embodiment of the present invention. Referring to FIG. 5, the chip package 50 is mostly similar to the package structure of FIG. 4. However, the detailed profile of the rounded top edges 130e of the molding compound 130 is similar to the enlarged view A of FIG. 1D. The sidewalls of the substrate 102 and the molding compound 130 are fully covered by the shielding layer and will not be exposed from the chip package 50. The shielding layer 140 is electrically connected to the substrate 102 through the direct contact with at least a ground plane 109 of the substrate 102, and is electrically grounded through the ground plane 109.

[0039] In brief, due to the rounding or blunting effect of the grinding process, the top edges and top corners of the molding compound become blunted (having an obtuse angle) or rounded, and the subsequently formed shielding layer can satisfactorily covers the molding compound without crevice. In the chip package structures of the present embodiment, the shielding layer disposed over the molding compound and the substrate function as an EMI shield, protecting the package from the EMI radiation from the surrounding radiation sources. In this case, the uniform coverage of the shielding layer over the molding compound, especially around the top edges and the corners, can effectively enhance the EMI shielding efficacy of the packages. In addition, the reliability of the package can be improved. As the top edges and top corners of the package structures become blunted or rounded, the leakage occurring at the corners can also be alleviated, thus boosting the electrical performances of the package structures. Accordingly, such design is compatible with the packaging of high frequency devices, particularly, radio frequency devices.

[0040] Although the present invention has been disclosed above by the embodiments, they are not intended to limit the present invention. Anyone skilled in the art can make some modifications and alteration without departing from the spirit and scope of the present invention. Therefore, the protecting range of the present invention falls in the appended claims.