Printed circuit board

Abstract

A printed circuit board according to an embodiment is disclosed, which includes a base substrate, a metal layer including pads and metal lines formed on the base substrate, a solder resist layer formed on the base substrate with the metal layer and having openings through which surfaces of the metal lines are exposed, and an underfill formed between the solder resist layer and a semiconductor chip electrically connected to the pads, the underfill including a blocking region formed in the openings.

Description

Technical Field

[0001] The embodiment relates to a printed circuit board in which a structure for preventing solder ball detachment is formed.

Background Art

[0002] Generally, when manufacturing a PCB (Printed Circuit Board), a solder resist (SR) is applied to the outermost layer. The solder resist is one of the insulating permanent coating substances that covers the wiring circuit and prevents unintentional connections from occurring during soldering when components are mounted.

[0003] FIG. 1 is a diagram for explaining the problems during reflow of a conventional printed circuit board.

[0004] Referring to FIG. 1, a conventional printed circuit board may be configured to include a substrate 10, a metal layer 20, a solder resist layer 30, a solder ball 40, a semiconductor chip 50, and an underfill 60.

[0005] During reflow of such a printed circuit board, due to the increased pressure caused by the internal humidity of the underfill, the adhesive force between the metal layer 20 and the solder resist layer 30 during heating of the solder ball is weak, the solder resist layer 30 separates and floats up, and solder is extruded out through this space.

[0006] When the printed circuit board is in a moisture-absorbed state, solder loss further increases, which may cause product defects. Therefore, a method for preventing solder loss in underfill-applied products is required.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

[0008] The embodiment may provide a printed circuit board having a structure formed to prevent solder balls from detaching. [Means for solving the problem]

[0009] A printed circuit board according to an embodiment may include a base substrate, a metal layer formed on the base substrate including pads and metal lines, a solder resist layer formed on the upper part of the base substrate on which the metal layer is formed, with openings formed therein that expose the surfaces of the metal lines, and an underfill formed between the solder resist layer and a semiconductor chip electrically connected to the pads, with a blocking region formed in the openings.

[0010] The blocking region may be formed along the edge of the semiconductor chip so as to surround the entire semiconductor chip.

[0011] The blocking region may be formed along the edge of the semiconductor chip so as to surround a portion of the semiconductor chip.

[0012] The blocking region may be formed in the area of ​​the overall edge of the semiconductor chip where a metal line is formed.

[0013] The opening may be formed within a predetermined distance from the pad.

[0014] The printed circuit board may further include solder balls formed on the upper part of the pads of the metal layer.

[0015] The opening includes a plurality of openings formed side by side, and the blocking region may include a plurality of blocking regions formed in each of the plurality of openings.

[0016] The width of the opening may be 0.2 mm to 0.3 mm.

Advantages of the Invention

[0017] According to an embodiment, among the solder resist layers formed on the upper portion of the base substrate, the solder resist surrounding at least a part of the semiconductor chip is removed, and a blocking region by underfill is formed in the removed portion. Thus, even if the solder resist is deformed due to an increase in the pressure of the underfill during reflow, it is possible to prevent the solder from flowing out to the outside.

[0018] According to an embodiment, since a predetermined blocking region can be formed in the solder resist layer to prevent the solder from flowing out, the defect rate of the underfill-applied product can be lowered.

[0019] According to an embodiment, since it is possible to lower the defect rate of the underfill-applied product, not only can the reliability be improved, but also an increase in sales can be expected thereby.

Brief Description of the Drawings

[0020] [Figure 1] It is a diagram for explaining problems during reflow of a conventional printed circuit board. [Figure 2] It is a perspective view showing a printed circuit board on which a semiconductor chip according to an embodiment of the present invention is mounted. [Figure 3] It is a cross-sectional view for explaining the overall structure of the printed circuit board shown in FIG. 2. [Figure 4] It is a diagram for explaining the formation process of a blocking region according to an embodiment. [Figure 5] It is a diagram for explaining the principle of preventing solder from flowing out in a blocking region according to an embodiment. [Figure 6a] This is a diagram for explaining the shape of a blocking region according to an embodiment. [Figure 6b] This is a diagram for explaining the shape of a blocking region according to an embodiment. [Figure 6c] This is a diagram for explaining the shape of a blocking region according to an embodiment. **Embodiments for Carrying Out the Invention**

[0021] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0022] However, the technical idea of the present invention is not limited to some of the described embodiments and can be implemented in various forms. Within the scope of the technical idea of the present invention, one or more of the components between the embodiments can be selectively combined and replaced for use.

[0023] Also, the terms (including technical and scientific terms) used in the embodiments of the present invention can be interpreted as meanings generally understood by those with ordinary knowledge in the technical field to which the present invention belongs, unless specifically defined and described clearly. Commonly used terms such as those defined in a dictionary can be interpreted considering their meanings in the context of the related technology.

[0024] Moreover, the terms used in the embodiments of the present invention are for explaining the embodiments and are not intended to limit the present invention.

[0025] In this specification, the singular form may include the plural form unless otherwise specifically mentioned in the text. When described as "at least one (or one or more) of A, B, and C", it may include one or more of all combinations of A, B, and C combined.

[0026] Also, when explaining the components of the embodiments of the present invention, terms such as first, second, A, B, (a), (b), etc. can be used.

[0027] These terms are used to distinguish one component from another, and are not limited by the nature, order, or sequence of the component in question.

[0028] Furthermore, when it is stated that one component is “connected,” “joined,” or “connected” to another component, this may include not only cases where the component is directly connected, joined, or connected to the other component, but also cases where it is “connected,” “joined,” or “connected” by another component that lies between it and the other component.

[0029] Furthermore, when described as being formed or positioned "above or below" each component, "above or below" includes not only cases where two components are in direct contact with each other, but also cases where one or more other components are formed or positioned between two components. Also, when expressed as "above or below," it can include not only an upward direction relative to one component, but also a downward direction.

[0030] In this embodiment, we propose a new printed circuit board structure in which the solder resist surrounding at least a portion of the semiconductor chip is removed from the solder resist layer formed on the upper part of the base substrate, and a blocking region is formed by underfill in the removed portion.

[0031] Figure 2 is a perspective view showing a printed circuit board equipped with a semiconductor chip according to an embodiment of the present invention, and Figure 3 is a cross-sectional view illustrating the overall structure of the printed circuit board shown in Figure 2.

[0032] Referring to Figures 2 and 3, the printed circuit board according to the embodiment may include a base substrate 100, a metal layer 200, a solder resist layer 300, solder balls 400, a semiconductor chip 500, an underfill 600, and a blocking area 300a.

[0033] The base substrate 100 includes a first surface and a second surface, and a semiconductor chip 500 may be placed on the first surface. Such a base substrate 100 may be composed of a single layer, but is not necessarily limited to this, and may be composed of a multilayer, a build-up layer consisting of vias, etc.

[0034] The metal layer 200 may provide electrical connections between components bonded to the base substrate 100. The metal layer 200 is formed on top of the base substrate 100 and may be connected to the semiconductor chip 500. The metal layer 200 may include pads and metal lines formed on the base substrate 100. The metal layer 200 may be formed of a conductive material for electrical connections.

[0035] The solder resist layer 300 may be formed on top of the substrate 100 on which the metal layer 200 is formed. The solder resist layer 300 can prevent short circuits between circuit patterns when solder balls 400 are joined or electronic components are mounted on top of the base substrate 100. The solder resist layer 300 may be formed of an insulating material to ensure electrical stability.

[0036] For example, the solder resist layer 300 can be formed by coating or applying liquid solder resist ink onto the base substrate 100 on which the metal layer 200 is formed. Methods for coating include physical vapor deposition (PVD), chemical vapor deposition (CVD), and atomic layer deposition (ALD).

[0037] The solder resist layer 300 may be formed from solder resist or photosolder resist. Solder resist is a resist that is applied in advance to areas of a substrate where lead must not adhere when soldering components, while photosolder resist is a photosensitive resist used to supplement areas that do not require soldering or solder coating.

[0038] An opening 300a may be formed in the solder resist layer 300 in the region adjacent to the solder balls 400. A blocking region 600a may be formed in the opening 300a of the solder resist layer 300 by underfill 600. In this case, the opening 300a can be designed to have a width W of 0.2 mm to 0.3 mm, but it is most preferable to design it to be 0.2 mm.

[0039] The solder ball 400 can electrically connect the metal layer 200 and the semiconductor chip 500.

[0040] The semiconductor chip 500 is positioned on top of the base substrate 100 and can be electrically connected via solder balls 400. Here, the semiconductor chip 500 may be a BGA (Ball Grid Array) chip.

[0041] The underfill 600 may be formed between the base substrate 100 and the semiconductor chip 500, or between the solder balls 400. The underfill 600 may be formed over an area larger than the size of the semiconductor chip 500.

[0042] Furthermore, the outer casing of the underfill 600 may be formed so that fillets are exposed to the outside.

[0043] The blocking region 600a may be formed in the opening 300a of the solder resist layer 300 by the underfill 600. That is, the blocking region 600a may be a protrusion formed by the underfill 600 in the region where the solder resist is removed from a portion of the solder resist layer 300 and the surface of the metal layer 200 is exposed from the solder resist layer 300.

[0044] The blocking region 600a may be formed within the region where the semiconductor chip 500 is placed, but may also be formed to surround the semiconductor chip 500 along its edge region. Such a blocking region 600a may be formed to surround the entire semiconductor chip 500, or to surround at least a portion of the semiconductor chip 500 but not the entire chip.

[0045] Figure 4 is a diagram illustrating the process of forming a blocking region according to the embodiment, and Figure 5 is a diagram illustrating the principle of preventing solder flow in the blocking region according to the embodiment.

[0046] Referring to Figure 4, a metal layer 200 can be formed on the upper part of the base substrate 100, and an opening 300a can be formed where a portion of the solder resist layer 300 adjacent to the pad is removed, exposing the metal layer.

[0047] A semiconductor chip 500 can be electrically connected to a base substrate 100 having an opening 300a using solder balls 400.

[0048] An underfill 600 can be formed by applying epoxy resin or the like between the base substrate 100, which has an opening 300a, and the semiconductor chip 500, or between the solder balls 400, and a blocking region 600a can be formed in the opening 300a by the underfill 600.

[0049] Since this underfill 600 is designed to exceed the semiconductor chip 500, after the underfill process, a blocking region 300a is generated by the underfill 600 that can sufficiently reinforce the metal layer 200, allowing for improvement without changing the solder resist layer.

[0050] Referring to Figure 5, during reflow soldering of a printed circuit board, the increased pressure due to humidity inside the underfill weakens the adhesion between the metal layer 200 and the solder resist layer 300 during the melting of the solder balls. As a result, the solder resist layer 300 separates and lifts up, and the solder moves through this lifted space.

[0051] Since a blocking region 300a is formed on the path through which the solder moves, the solder can be prevented from moving by the underfill 600 filling the blocking region 300a.

[0052] Therefore, by removing a portion of the solder resist layer 300 to form a blocking region 300a, it becomes possible to prevent the solder from leaking out through the blocking region 300a.

[0053] Figures 6a to 6c are diagrams illustrating the shape of the blocking region according to the embodiment.

[0054] Referring to Figure 6a, a metal layer 200 containing a circuit pattern and pads may be formed on the base substrate 100, and a solder resist layer 300 may be formed on top of the base substrate 100 formed on the metal layer 200.

[0055] Referring to Figure 6b, a blocking region 300a can be formed by removing all of the solder resist in the solder resist layer along the edge of the semiconductor chip placed on top of the base substrate 100.

[0056] Referring to Figure 6c, a blocking region 300a can be formed by partially removing the solder resist of the solder resist layer along the edge of the semiconductor chip placed on top of the base substrate 100.

[0057] Here, only the areas where the metal layer 200 may be exposed can be removed. This is because the solder passes through the space between the metal layer 200 and the solder resist layer 300.

[0058] Here, we explain the case where one blocking region is formed along the edge of a semiconductor chip as an example, but this is not necessarily the only case, and multiple blocking regions may be formed.

[0059] For example, by forming multiple openings in a solder resist layer 300 in a row, multiple blocking regions can be formed in each of the multiple openings by the underfill 600.

[0060] While preferred embodiments of the present invention have been described above with reference to those skilled in the art, a person skilled in the art will understand that the present invention can be modified and altered in various ways without departing from the spirit and scope of the invention as set forth in the following claims. [Explanation of Symbols]

[0061] 100: Base board 200: Metal layer 300: Solder Resist Layer 400: Solderball 500: Semiconductor chips 600: Underfill 600a: Blocking area

Claims

1. Base board and A metal layer formed on the base substrate, including pads and metal lines, Solder balls formed on the pad of the metal layer, A solder resist layer is formed on the upper part of the base substrate on which the metal layer is formed, and an opening is formed in which the surface of the metal line is exposed. The underfill is formed between the solder resist layer and the semiconductor chip electrically connected to the pad, and includes a blocking region formed in the opening, When the solder ball melts, the solder moves through the lifted space in the solder resist layer. The underfill is formed in a printed circuit board in an area larger than the size of the semiconductor chip.

2. The aforementioned blocking region is The printed circuit board according to claim 1, formed along the edge of the semiconductor chip so as to surround the entire semiconductor chip.

3. The aforementioned blocking region is The printed circuit board according to claim 1, formed along the edge of the semiconductor chip so as to surround a part of the semiconductor chip.

4. The aforementioned blocking region is The printed circuit board according to claim 3, formed on the region of the overall edge of the semiconductor chip in which the metal line is formed.

5. The printed circuit board according to claim 1, wherein the opening is formed within a predetermined distance from the pad.

6. The aforementioned opening includes a plurality of openings formed side by side, The aforementioned blocking region is The printed circuit board according to claim 1, comprising a plurality of blocking regions formed in each of the plurality of openings.

7. The printed circuit board according to claim 1, wherein the width of the opening is 0.2 mm to 0.3 mm.

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