Ball grid array package

Abstract

A ball grid array package according to an embodiment of the present invention comprises: a first circuit board; the second circuit board is arranged above the first circuit board; a first solder ball and a second solder ball disposed between the first circuit board and the second circuit board so as to be spaced apart from each other; a first adhesive disposed between the first circuit board and the second circuit board so as to extend from an upper surface of the first circuit board to a lower surface of the second circuit board along a first side surface of the first solder ball; and a second adhesive disposed between the first circuit board and the second circuit board so as to extend from an upper surface of the first circuit board to a lower surface of the second circuit board along a second side surface of the second solder ball. A first side surface of the first solder ball and a second side surface of the second solder ball are disposed to face each other. The first binder and the second binder form a channel region between the first circuit board and the second circuit board. An area of the channel region corresponds to 30%-70% of an area of a gap between a first side surface of the first solder ball and a second side surface of the second solder ball.

Description

Technical Field

[0001] Embodiments of the present invention relate to ball grid array packaging, and more specifically, to filled ball grid array packaging. Background Technology

[0002] Ball Grid Array (BGA) packaging is a surface-mount package for integrated circuits and is used in various fields such as vehicles, communications, and cameras.

[0003] Ball grid array (BGA) packages can have high density and high thermal conductivity, and excellent electrical performance due to low inductance.

[0004] A typical ball grid array (BGA) package consists of solder balls that bond a BGA chip to a circuit board. When BGA packages are used in automotive or communication equipment, cracks may occur around the solder balls due to thermal shock caused by temperature changes or impact caused by vibration.

[0005] To address these issues, an SMT process can be performed sequentially, in which the BGA chip is mounted on the board pads and then reflowed, and an underfill process is performed after cleaning.

[0006] However, due to the miniaturization and high integration of integrated circuit (IC) chips and the outgassing of the underfill material, small and uneven gaps may form between the solder balls, which may affect the reliability of ball grid array packages.

[0007] Furthermore, when performing a reflow process taking into account the melting point of the solder balls, warpage may occur due to the difference in thermal stress between the circuit board and the BGA chip, which could lead to cracks in the solder balls.

[0008] In addition, there are issues with increased manufacturing time and costs due to the bottom filling process. Summary of the Invention

[0009] Technical issues

[0010] The technical objective achieved by this invention is to provide a highly reliable ball grid array package.

[0011] Technical solution

[0012] According to an embodiment of the present invention, a ball grid array package includes a first circuit board, a second circuit board disposed on the first circuit board, a first solder ball and a second solder ball spaced apart from each other between the first circuit board and the second circuit board, a first adhesive disposed between the first circuit board and the second circuit board from the upper surface of the first circuit board along a first side surface of the first solder ball to the lower surface of the second circuit board, and a second adhesive disposed between the first circuit board and the second circuit board from the upper surface of the first circuit board along a second side surface of the second solder ball to the lower surface of the second circuit board, wherein the first side surface of the first solder ball and the second side surface of the second solder ball are configured to face each other, the first adhesive and the second adhesive form a channel region between the first circuit board and the second circuit board, and the area of ​​the channel region is in the range of 30% to 70% of the area of ​​the separation region between the first side surface of the first solder ball and the second side surface of the second solder ball.

[0013] The area of ​​the channel region can be in the range of 50% to 70% of the area of ​​the partition region between the first side surface of the first solder ball and the second side surface of the second solder ball.

[0014] The maximum width of the channel area between the first adhesive and the second adhesive may be 50% or greater than the diameter of at least one of the first and second solder balls.

[0015] At least one of the horizontal thickness of the first adhesive on the first side surface of the first solder ball and the horizontal thickness of the second adhesive on the second side surface of the second solder ball on the center line between the first circuit board and the second circuit board may be in the range of 10% to 50% of the diameter of the first solder ball and the diameter of the second solder ball.

[0016] At least one of the horizontal thickness of the first adhesive on the first side surface of the first solder ball and the horizontal thickness of the second adhesive on the second side surface of the second solder ball on the center line between the first circuit board and the second circuit board can be in the range of 5 μm to 20 μm.

[0017] The first adhesive and the second adhesive may meet each other on at least one of the upper surface of the first circuit board and the lower surface of the second circuit board.

[0018] At least one of the first adhesive and the second adhesive may include a region in which the thickness decreases in a direction parallel to the first circuit board or the second circuit board, and then increases again in a direction from the first circuit board to the second circuit board.

[0019] The first and second adhesives may include epoxy resin, a curing agent with flux function, and inorganic fillers, and the curing agent with flux function may include acid anhydride and rosin acid.

[0020] Curing agents with fluxing properties may include hexahydromethyl phthalic anhydride and rosin.

[0021] Epoxy resins may include naphthyl epoxy resins.

[0022] Inorganic fillers may include silica and carbon black.

[0023] A ball grid array package according to another embodiment of the present invention includes a first circuit board, a second circuit board disposed on the first circuit board, a plurality of solder balls spaced apart from each other between the first circuit board and the second circuit board, and an adhesive disposed between the first circuit board and the second circuit board from the upper surface of the first circuit board along the side surfaces of the plurality of solder balls to the lower surface of the second circuit board, wherein a channel surrounded by the adhesive is formed between the first circuit board and the second circuit board, and the area of ​​the channel is in the range of 30% to 70% of the area of ​​the separation region between the plurality of solder balls.

[0024] According to another embodiment of the present invention, a ball grid array package includes a first circuit board, a second circuit board disposed on the first circuit board, a plurality of solder balls spaced apart from each other between the first circuit board and the second circuit board, and a filler member disposed on the first circuit board along the edge of the second circuit board, wherein the surface of the filler member has a raised shape relative to an extension line from the edge of the filler member disposed on the upper surface of the first circuit board to the edge of the lower surface of the second circuit board.

[0025] At least a portion of the infill member may be located on the extension line.

[0026] The extension line can have an angle of 45° to 90° relative to the upper surface of the first circuit board.

[0027] The ball grid array package may include a section in which the angle between the surface of the filling member and the upper surface of the first circuit board decreases in the direction from the first circuit board to the second circuit board.

[0028] At least a portion of the filling member may be disposed on the side surface of the second circuit board.

[0029] The maximum height of the filling member relative to the upper surface of the first circuit board can be greater than the maximum height of the lower surface of the second circuit board.

[0030] The ball grid array package may further include an adhesive disposed between a first circuit board and a second circuit board from the upper surface of the first circuit board along the side surfaces of a plurality of solder balls, and a channel surrounded by at least some of the upper surface of the first circuit board, the adhesive, the side surfaces of the plurality of solder balls, and the lower surface of the second circuit board may be formed between the first circuit board and the second circuit board, and the area of ​​the channel may be in the range of 30% to 70% of the area of ​​the separation region between the plurality of solder balls.

[0031] The adhesive can be configured to extend along the side surfaces of the plurality of solder balls to the lower surface of the second circuit board, and the area of ​​the adhesive in contact with the upper surface of the first circuit board can be greater than or equal to the area of ​​the adhesive in contact with the lower surface of the second circuit board.

[0032] The thickness of the adhesive in the direction parallel to the first circuit board can be reduced in the direction from the upper surface of the first circuit board to the side surface of the solder ball.

[0033] The adhesive may include epoxy resin, a curing agent with flux function and inorganic filler, and the curing agent with flux function may include acid anhydride and rosin acid.

[0034] According to another embodiment of the present invention, a ball grid array package includes a first circuit board in which metal pads are disposed on its upper surface, a second circuit board disposed on the first circuit board, solder balls disposed between the first circuit board and the second circuit board, and a first layer and a second layer disposed sequentially between the metal pads and solder balls of the first circuit board in a direction from the metal pads to the solder balls, wherein the ball grid array package includes a section in which the content of bismuth (Bi) increases and then decreases and the content of copper (Cu) decreases and then increases from the interface between the first layer and the second layer to the interface between the second layer and the solder balls.

[0035] The segment containing the highest Bi content in the second layer can overlap with the segment containing the lowest Cu content.

[0036] The metal pads may include Cu, the first layer may include tin (Sn) and Cu, the second layer may include Sn, silver (Ag), Cu and Bi, and the solder balls may include Sn, Ag and Cu.

[0037] The thickness of the first layer can be in the range of 0.1 μm to 2 μm.

[0038] The second layer can be configured to extend from the lower surface of the solder ball along the side surface of the solder ball toward the second circuit board.

[0039] The second layer can be configured to extend from the lower surface of the solder ball along the side surface of the solder ball to the lower surface of the second circuit board.

[0040] According to another embodiment of the present invention, a ball grid array package includes a first circuit board on which a plurality of metal pads spaced apart from each other are disposed on its upper surface, a second circuit board disposed on the first circuit board, a plurality of solder balls spaced apart from each other between the first circuit board and the second circuit board, and a plurality of first layers and a plurality of second layers sequentially disposed between the plurality of metal pads and the plurality of solder balls on the first circuit board in a direction from the plurality of metal pads to the plurality of solder balls, wherein the ball grid array package includes a section in which the content of Bi increases and then decreases and the content of Cu decreases and then increases from the interface between each first layer and each second layer to the interface between each second layer and each solder ball.

[0041] Each of the second layers can extend from the lower surface of each of the solder balls along the side surface of each of the solder balls toward the second circuit board.

[0042] Multiple second layers can be disposed on the side surfaces of multiple solder balls and spaced apart from each other.

[0043] Each of the second layers can be configured to extend from the lower surface of each of the solder balls along the side surface of each of the solder balls to the lower surface of the second circuit board.

[0044] Beneficial effects

[0045] According to embodiments of the present invention, a ball grid array package with improved reliability against external shocks can be obtained. Furthermore, according to embodiments of the present invention, the amount of material required to fill the space between the solder balls can be reduced, and the manufacturing process of the ball grid array package can be simplified. Additionally, according to embodiments of the present invention, the problem of cracks in the solder balls can be minimized. Attached Figure Description

[0046] Figure 1 This is a top view of a ball grid array package according to an embodiment of the present invention.

[0047] Figure 2 This is a cross-sectional view of a ball grid array package according to an embodiment of the present invention.

[0048] Figure 3 This is a flowchart illustrating the process of manufacturing a ball grid array package according to an embodiment of the present invention.

[0049] Figure 4 shows a cross-sectional view of the ball grid array package according to the comparative example and embodiment.

[0050] Figure 5 shows a cross-sectional view of the ball grid array package according to the comparative example and embodiment.

[0051] Figure 6 and Figure 7 This is a cross-sectional view of a ball grid array package according to another embodiment of the present invention.

[0052] Figure 8 This is a flowchart illustrating the process of manufacturing a ball grid array package according to another embodiment of the present invention.

[0053] Figure 9 This is a cross-sectional view of a ball grid array package according to another embodiment of the present invention.

[0054] Figure 10 This is a graph showing the compositional variation of each layer in a ball grid array package according to yet another embodiment of the present invention.

[0055] Figure 11 This is a cross-sectional view of a ball grid array package according to another embodiment of the present invention.

[0056] Figure 12 This is a cross-sectional view of a ball grid array package according to another embodiment of the present invention.

[0057] Figure 13 This is a flowchart illustrating the process of manufacturing a ball grid array package according to an embodiment of the present invention.

[0058] Figure 14 (a) is a cross-sectional view of the ball grid array package manufactured according to Comparative Example 11, and Figure 14 (b) is a cross-sectional view of the ball grid array package manufactured according to Example 11. Detailed Implementation

[0059] In the following description, exemplary embodiments of the invention will be described with reference to the accompanying drawings.

[0060] However, the spirit of the present invention is not limited to the embodiments described, and can be implemented using various other embodiments, and at least one component of an embodiment may be selectively coupled to, replaced with, and used to implement the spirit of the present invention.

[0061] Furthermore, unless the context explicitly and specifically defines otherwise, all terms used herein (including technical and scientific terms) may be interpreted as having the conventional meaning of those skilled in the art, and the meaning of commonly used terms, such as those defined in common dictionaries, will be interpreted by taking into account the contextual meaning of the relevant art.

[0062] Furthermore, the terminology used in the embodiments of the present invention is for the purpose of describing the embodiments and is not intended to limit the present invention.

[0063] In this specification, unless the context clearly indicates otherwise, the singular form includes its plural form, and in the case of describing "at least one (or one or more) of A, B and C", this may include at least one of all combinations that can be made of A, B and C.

[0064] Furthermore, in the description of the components of the present invention, terms such as "first", "second", "A", "B", "(a)" and "(b)" may be used.

[0065] These terms are used only to distinguish one element from another, and the nature, order, etc., of the elements are not limited by these terms.

[0066] Furthermore, it should be understood that when an element is referred to as being “connected” or “coupled” to another element, such a description may include situations where the element is directly connected or coupled to another element, and situations where the element is connected or coupled to another element and another element is disposed therebetween.

[0067] Additionally, when any element is described as being formed or disposed "above or below" another element, this description includes both cases where the two elements are formed or disposed in direct contact with each other, and cases where one or more other elements are inserted between the two elements. Furthermore, when an element is described as being disposed "above or below" another element, this description can include cases where the one element is disposed on the upper or lower side relative to the other element.

[0068] In the following description, embodiments will be described in detail with reference to the accompanying drawings, wherein the same reference numerals refer to the same or corresponding parts, and redundant descriptions will be omitted regardless of the reference numerals.

[0069] Figure 1 This is a top view of a ball grid array package according to an embodiment of the present invention. Figure 2 This is a cross-sectional view of a ball grid array package according to an embodiment of the present invention.

[0070] refer to Figure 1 and Figure 2 The ball grid array package 100 includes a first circuit board 110, a second circuit board 120 disposed on the first circuit board 110, and a plurality of solder balls 130 disposed between the first circuit board 110 and the second circuit board 120 and spaced apart from each other.

[0071] The first circuit board 110 may be a single-layer or multi-layer printed circuit board. The first circuit board 110 may include pads 112 disposed on its upper surface. The pads 112 may include a conductive material, such as metal, and multiple pads 112 may be spaced apart from each other at predetermined intervals and may be connected to a line pattern on the first circuit board 110. Figure 2 In the diagram, the first pad 112 is shown as being etched into the upper surface of the first circuit board 110, but the invention is not limited thereto. The first pad 112 may also be embossed onto the upper surface of the first circuit board 110.

[0072] The second circuit board 120 includes a first surface 121 and a second surface 122, which is the surface opposite to the first surface 121. The first surface 121 of the second circuit board 120 may be the surface facing the first circuit board 110, and an integrated circuit (IC) chip 140 may be disposed on the second surface 122 of the second circuit board 120.

[0073] In this specification, for ease of description, the surface of the first circuit board 110 facing the second circuit board 120 may be the upper surface 111 of the first circuit board 110, and the surface of the second circuit board 120 facing the first circuit board 110 may be the lower surface 121 of the second circuit board 120.

[0074] The second circuit board 120 may be a printed circuit board. The second circuit board 120 may be an interposer. Therefore, the second circuit board 120 may include an insulating body, metal wire layers disposed on two surfaces of the insulating body, and through-holes through the insulating body to electrically connect the metal wire layers.

[0075] The second circuit board 120 can be electrically connected to the IC chip 140, supply power to the IC chip 140, input signals to the IC chip 140, and transmit signals output from the IC chip 140 to the first circuit board 110.

[0076] The second circuit board 120 may include pads 124 disposed on its lower surface. The pads 124 may include a conductive material, such as metal, and multiple pads 124 may be spaced apart from each other by a predetermined interval, and may be electrically connected to the IC chip 140 through internal pads or vias (not shown) of the second circuit board 120. Figure 2 In the diagram, the second pad 124 is shown as being etched into the lower surface of the second circuit board 120, but the invention is not limited thereto. The second pad 124 may also be embossed onto the lower surface of the second circuit board 120.

[0077] The pads 112 of the first circuit board 110 and the pads 124 of the second circuit board 120 can be connected by solder balls 130.

[0078] In the ball grid array package 100 according to an embodiment of the present invention, a plurality of solder balls 130 are spaced apart from each other, and an adhesive 150 is disposed between a first circuit board 110 and a second circuit board 120 from the upper surface 111 of the first circuit board 110 along the side surfaces of the plurality of solder balls 130 to the lower surface 121 of the second circuit board 120. Therefore, the adhesive 150 can stably bond the upper surface 111 of the first circuit board 110 to the solder balls 130 and the lower surface 121 of the second circuit board 120 to the solder balls 130. Furthermore, the adhesive 150 can reinforce the portion between the upper surface 111 of the first circuit board 110 and the solder balls 130, the portion between the lower surface 121 of the second circuit board 120 and the solder balls 130, and the side surfaces of the solder balls 130, thereby reducing the possibility of cracks occurring in the solder balls 130.

[0079] According to an embodiment of the invention, a channel 160 surrounded by adhesive 150 is formed between the first circuit board 110 and the second circuit board 120, and the area of ​​the channel 160 is in the range of 30% to 70%, or preferably 50% to 70%, of the area of ​​the partition region 130D between the plurality of solder balls 130. Here, the channel 160 can be an empty space surrounded by adhesive 150 between the first circuit board 110 and the second circuit board 120. In this way, when the channel 160 surrounded by adhesive 150 is formed between the first circuit board 110 and the second circuit board 120, the gas generated by the first circuit board 110, the second circuit board 120 and the adhesive 150 during the reflow process can be discharged to the outside through the channel 160. Therefore, the small and uneven voids formed in the adhesive 150 can be minimized. In this case, when the area of ​​channel 160 is less than 30% of the area of ​​the separation region 130D between the multiple solder balls 130, insufficient outgassing occurs through channel 160, which may result in fine and uneven voids in the adhesive 150. Furthermore, when the area of ​​channel 160 exceeds 70% of the area of ​​the separation region 130D between the multiple solder balls 130, the reinforcing effect of adhesive 150 is reduced, which may result in cracks in the solder balls 130.

[0080] In the following text, reference will be made to Figure 2The cross-sectional view illustrates the ball grid array package 100 according to an embodiment of the present invention in more detail. According to an embodiment of the present invention, a first solder ball 131 and a second solder ball 132 are spaced apart from each other between a first circuit board 110 and a second circuit board 120. A first adhesive 151 is disposed between the first circuit board 110 and the second circuit board 120 from the upper surface 111 of the first circuit board 110 along the first side surface 131-1 of the first solder ball 131 to the lower surface 121 of the second circuit board 120, and a second adhesive 152 is disposed between the first circuit board 110 and the second circuit board 120 from the upper surface 111 of the first circuit board 110 along the second side surface 132-1 of the second solder ball 132 to the lower surface 121 of the second circuit board 120. Therefore, the first adhesive 151 stably bonds the upper surface 111 of the first circuit board 110 to the first solder ball 131, and the lower surface 121 of the second circuit board 120 to the first solder ball 131, and strengthens the first side surface 131-1 of the first solder ball 131. The second adhesive 152 stably bonds the upper surface 111 of the first circuit board 110 to the second solder ball 132, and the lower surface 121 of the second circuit board 120 to the second solder ball 132, and strengthens the second side surface 132-1 of the second solder ball 132, thereby reducing the possibility of cracks occurring in the first solder ball 131 and the second solder ball 132.

[0081] Here, the first side surface 131-1 of the first solder ball 131 and the second side surface 132-1 of the second solder ball 132 face each other, and the first adhesive 151 and the second adhesive 152 form a channel 160. The first adhesive 151 is disposed between the first circuit board 110 and the second circuit board 120 from the upper surface 111 of the first circuit board 110 along the first side surface 131-1 of the first solder ball 131 to the lower surface 121 of the second circuit board 120, and the second adhesive 152 is disposed between the first circuit board 110 and the second circuit board 120 from the upper surface 111 of the first circuit board 110 along the second side surface 132-1 of the second solder ball 132 to the lower surface 121 of the second circuit board 120. In this case, the area of ​​the channel 160 between the first adhesive 151 and the second adhesive 152 is in the range of 30% to 70%, or preferably 50% to 70%, of the area of ​​the separation region 130D between the side surfaces of the first solder ball 131 and the second solder ball 132. Here, the area of ​​channel 160 and the area of ​​dividing region 130D are... Figure 2The cross-sectional area between the first circuit board 110 and the second circuit board 120 on the cross-section. In this way, when the first adhesive 151 and the second adhesive 152 form a channel 160 between the first side surface 131-1 of the first solder ball 131 and the second side surface 132-1 of the second solder ball 132, the gas generated by the first circuit board 110, the second circuit board 120, the first adhesive 151 and the second adhesive 152 during the reflow process can be discharged to the outside through the channel 160 between the first adhesive 151 and the second adhesive 152. Therefore, the small and uneven voids formed in the first adhesive 151 and the second adhesive 152 can be minimized. In this case, when the ratio between the area of ​​the channel 160 between the first adhesive 151 and the second adhesive 152 and the area of ​​the separation region 130D between the first side surface 131-1 of the first solder ball 131 and the second side surface 132-1 of the second solder ball 132 meets this numerical range, both the outgassing effect and the strengthening effect of the adhesive 150 can be obtained.

[0082] According to an embodiment of the present invention, the maximum separation distance D1 between the first adhesive 151 and the second adhesive 152 forming the channel 160 may be 50% or greater of the diameter D2 of at least one of the first solder ball 131 and the second solder ball 132, preferably in the range of 50% to 300%, or more preferably in the range of 50% to 200%. Here, the maximum separation distance D1 between the first adhesive 151 and the second adhesive 152 may be a distance in a direction parallel to the first circuit board 110 or the second circuit board 120. The maximum separation distance D1 between the first adhesive 151 and the second adhesive 152 may be the maximum width of the channel 160 in a direction parallel to the first circuit board 110 or the second circuit board 120. Therefore, since the gas generated during the reflow process can be released to the outside through the channel 160 between the first adhesive 151 and the second adhesive 152, the small and uneven voids formed in the first adhesive 151 and the second adhesive 152 can be minimized, and since the first solder ball 131 and the second solder ball 132 are reinforced by the first adhesive 151 and the second adhesive 152, the problem of cracks in the first solder ball 131 and the second solder ball 132 can be prevented.

[0083] According to an embodiment of the present invention, at least one of the horizontal thickness T of the first adhesive 151 on the first side surface 131-1 of the first solder ball 131 and the horizontal thickness T of the second adhesive 152 on the second side surface 132-1 of the second solder ball 132 on the center line CL between the first circuit board 110 and the second circuit board 120 can be in the range of 10% to 50% or less, preferably 10% to 40%, or more preferably 10% to 30% of the diameter D2 of the first solder ball 131 or the diameter D2 of the second solder ball 132. When at least one of the horizontal thickness T of the first adhesive 151 on the first side surface 131-1 of the first solder ball 131 and the horizontal thickness T of the second adhesive 152 on the second side surface 132-1 of the second solder ball 132 is less than this range, cracks may appear in the first solder ball 131 and the second solder ball 132 due to the reduced reinforcing effect of the adhesive. When at least one of the horizontal thickness T of the first adhesive 151 on the first side surface 131-1 of the first solder ball 131 and the horizontal thickness T of the second adhesive 152 on the second side surface 132-1 of the second solder ball 132 exceeds this value range, fine and uneven voids may form in the first adhesive 151 and the second adhesive 152 because gas release will not occur sufficiently. Here, the horizontal direction can be parallel to the first circuit board 110 or parallel to the second circuit board 120.

[0084] According to an embodiment of the present invention, at least one of the horizontal thickness T of the first adhesive 151 on the first side surface 131-1 of the first solder ball 131 and the horizontal thickness T of the second adhesive 152 on the second side surface 132-1 of the second solder ball 132 on the center line CL between the first circuit board 110 and the second circuit board 120 can be in the range of 5 μm to 20 μm. When at least one of the horizontal thickness T of the first adhesive 151 on the first side surface 131-1 of the first solder ball 131 and the horizontal thickness T of the second adhesive 152 on the second side surface 132-1 of the second solder ball 132 is less than this range, cracks may appear in the first solder ball 131 and the second solder ball 132 due to the reduced reinforcing effect of the adhesive. When at least one of the horizontal thickness T of the first adhesive 151 on the first side surface 131-1 of the first solder ball 131 and the horizontal thickness T of the second adhesive 152 on the second side surface 132-1 of the second solder ball 132 exceeds this value range, fine and uneven voids may form in the first adhesive 151 and the second adhesive 152 because gas release will not occur sufficiently.

[0085] According to an embodiment of the present invention, the first adhesive 151 and the second adhesive 152 may meet each other on at least one of the upper surface 111 of the first circuit board 110 and the lower surface 121 of the second circuit board 120. Therefore, the first adhesive 151 and the second adhesive 152 can reinforce the upper surface 111 of the first circuit board 110 and the lower surface 121 of the second circuit board 120 to prevent damage to the ball grid array package 100 due to external impact.

[0086] According to an embodiment of the present invention, the contact area between the first adhesive 151 and the second adhesive 152 and the upper surface 111 of the first circuit board 110 can be greater than the contact area between the first adhesive 151 and the second adhesive 152 and the lower surface 121 of the second circuit board 120. Alternatively, in the region perpendicularly overlapping with the channel 160, the vertical thickness of the first adhesive 151 and the second adhesive 152 disposed on the upper surface 111 of the first circuit board 110 can be greater than the vertical thickness of the first adhesive 151 and the second adhesive 152 disposed on the lower surface 121 of the second circuit board 120. For example, as Figure 2As shown, the first adhesive 151 and the second adhesive 152 can be configured to meet each other on the upper surface 111 of the first circuit board 110 in the region perpendicularly overlapping with the channel 160, but the first adhesive 151 and the second adhesive 152 can be configured not to meet each other on the lower surface 121 of the second circuit board 120. That is, the first adhesive 151 and the second adhesive 152 can be disposed on the entire upper surface 111 of the first circuit board 110 in the region perpendicularly overlapping with the channel 160, but the first adhesive 151 and the second adhesive 152 can be disposed only on a portion of the lower surface 121 of the second circuit board 120. In this case, there may be a region in which the thickness of the first adhesive 151 and the second adhesive 152 on the upper surface 111 of the first circuit board 110 in the region perpendicularly overlapping with the channel 160 gradually decreases in the horizontal direction toward the center of the channel 160. There may be a region in which the thickness of the first adhesive 151 and the second adhesive 152 on the lower surface 121 of the second circuit board 120 gradually decreases in the horizontal direction toward the center of the channel 160 in the region perpendicularly overlapping with the channel 160, and there may also be a region in which the thickness of the first adhesive 151 and the second adhesive 152 is 0, because the first adhesive 151 and the second adhesive 152 are not provided. In the region not perpendicularly overlapping with the channel 160, the first adhesive 151 and the second adhesive 152 may each fill the space from the upper surface 111 of the first circuit board 110 to the lower surface 121 of the second circuit board 120. That is, in the region not perpendicularly overlapping with the channel 160, the thickness of the first adhesive 151 and the thickness of the second adhesive 152 may each be equal to the vertical distance from the upper surface 111 of the first circuit board 110 to the lower surface 121 of the second circuit board 120. Here, the vertical direction may be the direction from the first circuit board 110 to the second circuit board 120. Therefore, the lower surface of the solder ball 130 can be strengthened more effectively, as it is more susceptible to thermal shock than the upper surface of the solder ball 130.

[0087] According to embodiments of the present invention, at least one of the first adhesive 151 and the second adhesive 152 may include a region in which the horizontal thickness in a direction parallel to the first circuit board 110 or the second circuit board 120 decreases and then increases again in a vertical direction from the first circuit board 110 to the second circuit board 120. That is, the thickness of at least one of the first adhesive 151 and the second adhesive 152 in a direction parallel to the first circuit board 110 or the second circuit board 120 may gradually decrease from the upper surface 111 of the first circuit board 110 to the center line CL between the first circuit board 110 and the second circuit board 120, and then gradually increase from the center line CL between the first circuit board 110 and the second circuit board 120 to the lower surface 121 of the second circuit board 120. Therefore, the bonding strength between the upper surface 111 of the first circuit board 110 and the lower portion of the solder ball 130 can be improved, and cracking in the lower portion of the solder ball 130 (which may be more susceptible to thermal shock than the center of the solder ball 130) can be prevented. Similarly, the bonding strength between the lower surface 121 of the second circuit board 120 and the upper surface of the solder ball 130 can be improved, and cracks in the upper part of the solder ball 130 (which may be more susceptible to thermal shock than the center of the solder ball 130) can be prevented.

[0088] According to an embodiment of the present invention, the first adhesive 151 and the second adhesive 152 may include epoxy resin, curing agent and inorganic filler.

[0089] Here, the epoxy resin may possess chemical resistance, reactivity, toughness, adhesion, and heat resistance. The epoxy resin may include at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, and naphthalene type epoxy resin. For example, the bisphenol A type epoxy resin may include bisphenol A diglycidyl ether, the bisphenol F type epoxy resin may include at least one of bisphenol F epichlorohydrin resin and bisphenol F diglycidyl ether, and the naphthalene type epoxy resin may include 1,6-naphthalene diglycidyl ether. When the epoxy resin includes a naphthalene type epoxy resin, the strength of the adhesive 150 can be improved.

[0090] The curing agent can be a curing agent with flux functionality. A curing agent with flux functionality can be a curing agent that removes the oxide film on the surface of the solder ball 130 and then reacts with the oxirane groups of the epoxy resin. Therefore, in this specification, the adhesive 150 can be referred to as an epoxy flux. According to embodiments of the present invention, the curing agent with flux functionality is activated at a temperature of 130°C or higher to remove the oxide film on the surface of the solder ball 130 at a temperature of 130°C to 200°C and to prevent carbonization at a temperature of 250°C or higher. Therefore, the curing agent with flux functionality can react with the epoxy resin at high temperatures to delay curing and can have the function of preventing carbonization at high temperatures.

[0091] For example, a curing agent with flux functionality may include anhydrides and acids. For example, a curing agent with flux functionality may include anhydrides and rosin acids. For example, a curing agent with flux functionality may include hexahydromethyl phthalic anhydride and rosin. A curing agent with flux functionality may further include pentanedioic acid. Therefore, a curing agent with flux functionality can remove the oxide film on the surface of the solder ball 130 to reduce the surface tension of the solder ball surface. The curing agent that has performed the function of removing the oxide film on the surface of the solder ball 130 can react with the epoxy resin to remove acid activity. Therefore, since it is not necessary to clean the flux separately, the manufacturing process of the ball grid array package 100 can be simplified, and the formation of fine and uneven voids in the adhesive 150 can be minimized. Furthermore, since the curing of the epoxy resin is delayed due to the reaction between the acid in the curing agent and the epoxy resin, the degassing efficiency can be improved.

[0092] Inorganic fillers may include at least one of silica and carbon black. This can improve the coefficient of thermal expansion and modulus of the binder 150. However, inorganic fillers may be included in an amount that does not interfere with the bonding with the solder balls 130.

[0093] Figure 3 This is a flowchart illustrating the process of manufacturing a ball grid array package according to an embodiment of the present invention.

[0094] refer to Figure 3 A first circuit board 110 is provided (S300). As described above, the first circuit board 110 may be a single-layer or multi-layer printed circuit board including pads 112 disposed on the upper surface 111.

[0095] Next, the first circuit board 110 is coated with a paste for use as an adhesive (S310). The paste for use as an adhesive may include an epoxy resin, a curing agent, and an inorganic filler, and the curing agent may be a curing agent with flux function. For example, the epoxy resin may include bisphenol A type epoxy resin, bisphenol F type epoxy resin, and naphthalene type epoxy resin, the curing agent may include hexahydromethyl phthalic anhydride and rosin, and the inorganic filler may include silica and carbon black. At least one of the dispensing, printing, and dipping processes may be used to coat the first circuit board 110 with the paste for use as an adhesive.

[0096] Next, a second circuit board 120, in which the solder ball array 130 is disposed on the lower surface 121, is disposed on the first circuit board 110 (S320). In this case, the solder ball array 130 can be disposed on the pads 112 of the first circuit board 110. The IC chip 140 can be pre-disposed on the upper surface 122 of the second circuit board 120.

[0097] Next, a reflow process (S330) is performed. Therefore, the paste for bonding can move along the side surface of the solder ball 130 to the lower surface 121 of the second circuit board 120, bonding the pads 112 of the first circuit board 110 and the solder ball 130 to each other, and strengthening the portion between the upper surface of the first circuit board 110 and the solder ball 130, the side surface of the solder ball 130, and the portion between the lower surface of the second circuit board 120 and the solder ball 130. According to an embodiment of the invention, when a paste for bonding is used that includes a curing agent with flux function, after the curing agent with flux function removes the oxide film on the surface of the solder ball 130 during the reflow process, the epoxy resin can be cured to extend along the side surface of the solder ball 130 to the lower surface 121 of the second circuit board 120. Therefore, a separate flux cleaning process is not required after reflow, and the reflow and solder ball strengthening processes can be performed simultaneously.

[0098] Figure 4 shows a cross-sectional view of the ball grid array package according to the comparative example and the embodiment. Table 1 shows the reliability test results during thermal shock according to the comparative example and the embodiment. Figure 5 shows a cross-sectional view of the ball grid array package according to the comparative example and the embodiment.

[0099] according to Figure 4a In Comparative Example 1, in a structure including a first circuit board 110, a second circuit board 120 disposed on the first circuit board 110, and a first solder ball 131 and a second solder ball 132 disposed between the first circuit board 110 and the second circuit board 120, the entire space between the first solder ball 131 and the second solder ball 132 is filled with epoxy flux.

[0100] according to Figure 4bIn Comparative Example 2, in a structure including a first circuit board 110, a second circuit board 120 disposed on the first circuit board 110, and first solder balls 131 and second solder balls 132 spaced apart from each other between the first circuit board 110 and the second circuit board 120, epoxy resin flux is only disposed below the first solder balls 131 and second solder balls 132. Here, the lower portion of the first solder balls 131 and second solder balls 132 may be a region closer to the first circuit board 110 relative to a region corresponding to the maximum width of the first solder balls 131 and second solder balls 132, and the upper portion of the first solder balls 131 and second solder balls 132 may be a region closer to the second circuit board 120 relative to a region corresponding to the maximum width of the first solder balls 131 and second solder balls 132. Here, the width of the first solder balls 131 and second solder balls 132 may be the width in a horizontal direction parallel to the first circuit board 110 and the second circuit board 120, and the maximum width of the first solder balls 131 and second solder balls 132 may be the maximum width of the first solder balls 131 and second solder balls 132 in the horizontal direction. In other words, as shown in the figure, epoxy resin flux fills the space from the upper surface of the pad 112 to a height of 16 μm along the side surfaces of the first solder ball 131 and the second solder ball 132, and is not disposed on the upper part of the first solder ball 131 and the second solder ball 132. On the upper surface of the pad 112, the epoxy resin flux is horizontally disposed at a distance of 10 μm from a point on the upper surface of the pad 112 corresponding to the maximum width of the first solder ball 131 and the second solder ball 132.

[0101] according to Figure 4c In one embodiment, in a structure including a first circuit board 110, a second circuit board 120 disposed on the first circuit board 110, and first solder balls 131 and second solder balls 132 spaced apart from each other between the first circuit board 110 and the second circuit board 120, epoxy resin flux is disposed along the side surface of the first solder ball 131 from the upper surface 111 of the first circuit board 110 to the lower surface 121 of the second circuit board 120, and along the side surface of the second solder ball 132 from the upper surface 111 of the first circuit board 110 to the lower surface 121 of the second circuit board 120. In this case, the side surfaces of the first solder ball 131 and the second solder ball 132 are positioned facing each other, and the epoxy resin flux forms a channel region between the side surfaces of the first solder ball 131 and the second solder ball 132. In this case, the epoxy resin flux is horizontally disposed at a distance of 10 μm from the side surface of the first solder ball 131 and the second solder ball 132 at the maximum width.

[0102] [Table 1]

[0103]

[0104] In Table 1, in the structure of the reference example including a first circuit board 110, a second circuit board 120 disposed on the first circuit board 110, and a first solder ball 131 and a second solder ball 132 disposed between the first circuit board 110 and the second circuit board 120, no epoxy resin flux is provided.

[0105] In the thermal shock test performed under the condition that the temperature changes from -40°C to 80°C and the residence time is 10 minutes, it can be seen that the structure according to the embodiment obtains significantly higher reliability results compared with the structures according to the reference example, comparative example 1 and comparative example 2.

[0106] Figure 5a This is a cross-sectional view of the ball grid array according to an embodiment. Figure 5b This is a cross-sectional view of the solder balls of the ball grid array according to an embodiment, and Figure 5c This is a cross-sectional view of the ball grid array according to the reference example after a thermal shock test. (Reference) Figure 5c As can be seen, cracks appeared in the solder balls after the thermal shock test.

[0107] According to embodiments of the present invention, the amount of epoxy flux used can be reduced compared to Comparative Example 1, in which epoxy flux fills the entire space between solder balls. Furthermore, according to embodiments of the present invention, since the reflow process is performed after the application of epoxy flux, the bonding between the pads 112 of the first circuit board 110 and the solder balls 131 and 132, as well as the reinforcement of the side surfaces of the solder balls 131 and 132, can be performed simultaneously. Therefore, compared to Comparative Example 1, in which epoxy flux fills the entire space between solder balls after the reflow process, the manufacturing process and manufacturing time can be significantly reduced.

[0108] In addition, when the entire space between the first solder ball 131 and the second solder ball 132 is filled with epoxy resin flux as in Comparative Example 1, fine and uneven voids are formed inside the adhesive because degassing from the epoxy resin flux, the first circuit board 110 and the second circuit board 120 cannot be effectively performed, which may lead to reduced reliability due to thermal shock.

[0109] On the other hand, compared with Comparative Example 1, according to Comparative Example 2 and the embodiment, degassing from epoxy resin flux, first circuit board 110 and second circuit board 120 can be effectively performed, thereby obtaining high reliability.

[0110] However, in Comparative Example 2, in which the epoxy flux is only disposed below the first solder ball 131 and the second solder ball 132, cracks may occur in the upper part of the first solder ball 131 and the second solder ball 132 compared to the embodiment, since the upper part of the first solder ball 131 and the second solder ball 132 cannot be reinforced, resulting in lower reliability.

[0111] Figure 6 and Figure 7 This is a cross-sectional view of a ball grid array package according to another embodiment of the present invention. (The reference numerals are omitted.) Figure 1 Redundant descriptions of content identical to that described in Figure 5.

[0112] refer to Figure 6 and Figure 7 The ball grid array package 100 includes a first circuit board 110, a second circuit board 120 disposed on the first circuit board 110, and a plurality of solder balls 130 disposed between the first circuit board 110 and the second circuit board 120 and spaced apart from each other.

[0113] The ball grid array package 100 according to another embodiment of the present invention further includes a filler 170 disposed on the first circuit board 110 along the edge of the second circuit board 120. Since the filler 170 according to the embodiment of the present invention fills the space between the upper surface 111 of the first circuit board 110 and the lower surface 121 of the second circuit board 120 along the edge of the second circuit board 120, the filler 170 may be referred to as a side filler.

[0114] The filling member 170 according to an embodiment of the present invention may be an epoxy resin composition comprising epoxy resin, curing agent and inorganic filler.

[0115] Here, the epoxy resin may possess chemical resistance, reactivity, toughness, adhesion, and heat resistance. The epoxy resin may include at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, and naphthalene type epoxy resin.

[0116] The curing agent may include at least one of amine-based curing agents, phenol-based curing agents, anhydride-based curing agents, polythiol-based curing agents, polyaminoamide-based curing agents, isocyanate-based curing agents, and end-capped isocyanate-based curing agents, and two or more types of curing agents may be mixed and used. According to embodiments of the invention, the curing agent may be a curing agent with flux functionality. A curing agent with flux functionality may be a curing agent that removes the oxide film on the surface of the solder ball 130 and then reacts with the epoxy resin.

[0117] Inorganic fillers may include at least one of alumina, boron nitride, aluminum nitride, silicon dioxide, carbon black, silicon carbide, and graphite.

[0118] However, the composition of the filler 170 is not limited thereto, and the filler 170 according to embodiments of the present invention may include known underfill materials used in ball grid array packages.

[0119] According to an embodiment of the present invention, the surface of the filler member 170 has a shape that protrudes outward from a virtual extension line EL, which extends from the edge of the filler member 170 disposed on the upper surface 111 of the first circuit board 110 to the edge of the lower surface 121 of the second circuit board 120. Here, the edge of the filler member 170 disposed on the upper surface 111 of the first circuit board 110 may be the edge of the filler member 170 disposed near the outer edge 111S of the upper surface 111 of the first circuit board 110. The edge of the lower surface 121 of the second circuit board 120 may be the outer edge 121S of the lower surface 121 of the second circuit board 120. The virtual extension line EL from the edge of the filler member 170 disposed on the upper surface 111 of the first circuit board 110 to the edge of the lower surface 121 of the second circuit board 120 may be a line that virtually connects the edge of the filler member 170 disposed on the upper surface 111 of the first circuit board 110 to the edge of the lower surface 121 of the second circuit board 120. The fact that the surface of the filler member 170 has a raised shape relative to the virtual extension line EL can mean that the surface of the filler member 170 is positioned at a higher level than the virtual extension line EL. That is, it can mean that the filler member 170 is disposed on the virtual extension line EL.

[0120] Therefore, since a sufficient amount of filling member 170 is provided between the first circuit board 110 and the second circuit board 120, the portion between the first circuit board 110 and the second circuit board 120 can be stably supported, and the space between the first circuit board 110 and the second circuit board 120 can be protected from external foreign objects, thermal shock or vibration.

[0121] According to an embodiment of the present invention, a virtual extension line EL from the edge of the filling member 170 disposed on the upper surface 111 of the first circuit board 110 to the edge of the lower surface 121 of the second circuit board 120 can have an angle θ of 45° to 90° relative to the upper surface 111 of the first circuit board 110. When the angle between the virtual extension line EL and the upper surface 111 of the first circuit board 110 is less than 45°, the filling member 170 is widely spread on the upper surface 111 of the first circuit board 110 close to the edge 111S of the upper surface 111 of the first circuit board 110, which may mean that the filling member 170 is wasted more than necessary. And when the angle between the virtual extension line EL and the upper surface 111 of the first circuit board 110 exceeds 90°, the filling member 170 is positioned on the upper surface 111 of the first circuit board 110 inside the edge 121S of the lower surface 121 of the second circuit board 120, which may mean that a sufficient amount of filling member 170 is not provided to stably support the portion between the first circuit board 110 and the second circuit board 120.

[0122] According to embodiments of the present invention, a section may be included in which the angle between the surface of the filler member 170 and the upper surface 111 of the first circuit board 110 decreases in the direction from the first circuit board 110 to the second circuit board 120. For example, the angle θ1 between the edge of the filler member 170 disposed on the upper surface 111 of the first circuit board 110 and the upper surface 111 of the first circuit board 110 may be greater than the angle θ2 between the surface of the filler member 170 and the upper surface 111 of the first circuit board 110 on the virtual center line CL between the first circuit board 110 and the second circuit board 120. Therefore, since a sufficient amount of filler member 170 is disposed between the first circuit board 110 and the second circuit board 120, the portion between the first circuit board 110 and the second circuit board 120 can be stably supported, and the space between the first circuit board 110 and the second circuit board 120 can be protected from external foreign objects, thermal shock, or vibration.

[0123] According to an embodiment of the present invention, at least a portion of the filling member 170 may be disposed on the side surface of the second circuit board 120. For example, at least a portion of the filling member 170 may be disposed on the edge of the lower surface 121 of the second circuit board 120, and may also be disposed on the side surface 123 of the second circuit board 120. Therefore, the filling member 170 can not only support the lower surface 121 of the second circuit board 120, but also support the side surface 123, seal the space between the upper surface 111 of the first circuit board 110 and the lower surface 121 of the second circuit board 120, and protect the space between the first circuit board 110 and the second circuit board 120 from the effects of external foreign objects, thermal shock, or vibration.

[0124] According to an embodiment of the present invention, the maximum height H1 of the filling member 170 relative to the upper surface 111 of the first circuit board 110 can be greater than the height H2 of the lower surface 121 of the second circuit board 120. Therefore, the filling member 170 can not only support the lower surface 121 of the second circuit board 120, but also support the side surface 123, seal the space between the upper surface 111 of the first circuit board 110 and the lower surface 121 of the second circuit board 120, and protect the space between the first circuit board 110 and the second circuit board 120 from the effects of external foreign objects, thermal shock, or vibration.

[0125] In a ball grid array package 100 according to another embodiment of the present invention, such as Figure 6As shown, a plurality of solder balls 130 are spaced apart from each other, and adhesive 150 is disposed between the first circuit board 110 and the second circuit board 120 from the upper surface 111 of the first circuit board 110 along the side surfaces of the plurality of solder balls 130. Therefore, adhesive 150 can stably bond the upper surface 111 of the first circuit board 110 to the solder balls 130, and adhesive 150 can reinforce the portion between the upper surface 111 of the first circuit board 110 and the solder balls 130, as well as the side surfaces of the solder balls 130, thereby reducing the possibility of cracks occurring in the solder balls 130.

[0126] like Figure 7 As shown, a plurality of solder balls 130 are spaced apart from each other, and an adhesive 150 is disposed between the first circuit board 110 and the second circuit board 120 from the upper surface 111 of the first circuit board 110 along the side surfaces of the plurality of solder balls 130 to the lower surface 121 of the second circuit board 120. Therefore, the adhesive 150 can stably bond the upper surface 111 of the first circuit board 110 to the solder balls 130 and the lower surface 121 of the second circuit board 120 to the solder balls 130, and the adhesive 150 can reinforce the portion between the upper surface 111 of the first circuit board 110 and the solder balls 130, the portion between the lower surface 121 of the second circuit board 120 and the solder balls 130, and the side surfaces of the solder balls 130, thereby reducing the possibility of cracks occurring in the solder balls 130.

[0127] For the adhesive 150 between the first circuit board 110 and the second circuit board 120, and the channel 160 surrounded by at least some of the upper surface 111 of the first circuit board 110, the adhesive 150, the side surfaces of the solder balls 130, and the lower surface 121 of the second circuit board 120, the reference is omitted. Figure 1 Redundant descriptions of content identical to that described in Figure 5.

[0128] Figure 8 This is a flowchart illustrating the process of manufacturing a ball grid array package according to another embodiment of the present invention.

[0129] refer to Figure 8 A first circuit board 110 is provided (S1300). As described above, the first circuit board 110 may be a single-layer or multi-layer printed circuit board including pads 112 disposed on the upper surface 111.

[0130] Next, a paste for use as an adhesive is applied to the first circuit board 110 (S1310). The paste for use as an adhesive may include an epoxy resin, a curing agent, and an inorganic filler, and the curing agent may be a curing agent with flux function. For example, the epoxy resin may include bisphenol A type epoxy resin, bisphenol F type epoxy resin, and naphthalene type epoxy resin; the curing agent may include hexahydromethyl phthalic anhydride and rosin; and the inorganic filler may include silica and carbon black. At least one of the dispensing, printing, and dipping processes may be used to apply the paste for use as an adhesive to the first circuit board 110. The pads 112 of the first circuit board 110 may be coated with the paste for use as an adhesive.

[0131] Next, a filler paste is applied to the first circuit board 110 (S1320). The filler paste may include an epoxy resin, a curing agent, and an inorganic filler. For example, the epoxy resin may include at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, and naphthalene type epoxy resin; the curing agent may include at least one of anamine curing agent, phenol curing agent, anhydride curing agent, polythiol curing agent, polyaminoamide curing agent, isocyanate curing agent, and end-capped isocyanate curing agent; and the inorganic filler may include at least one of alumina, boron nitride, aluminum nitride, silica, carbon black, silicon carbide, and graphite. The filler paste may be applied so as not to overlap with the pads 112 of the first circuit board 110. For example, the filler paste may be applied spaced apart from and surrounding the paste for the adhesive. The filler paste may be applied taking into account the dimensions of the second circuit board 120. For example, the filler paste may be applied such that the edges of the lower surface of the second circuit board 120 are positioned on the filler paste. The filler slurry and the slurry for the binder can have the same composition. When the filler slurry and the slurry for the binder have the same composition, the formation of the binder 150 and the formation of the filler member 170 can be performed simultaneously under the same conditions, and thus the reflow process can be simplified.

[0132] Next, a second circuit board 120, in which the solder ball array 130 is disposed on the lower surface 121, is disposed on the first circuit board 110 (S1330). In this case, the solder ball array 130 can be disposed on the pads 112 of the first circuit board 110, and the edge of the lower surface 121 of the second circuit board 120 can be disposed on the upper surface of the filler member 170. The IC chip 140 can be pre-disposed on the upper surface 122 of the second circuit board 120.

[0133] Next, a reflow process (S1340) is performed. Therefore, the paste for the adhesive can move along the side surface of the solder ball 130 to the lower surface 121 of the second circuit board 120, bonding the pads 112 of the first circuit board 110 and the solder ball 130 together, and reinforcing the portion between the upper surface of the first circuit board 110 and the solder ball 130, the side surface of the solder ball 130, and the portion between the lower surface of the second circuit board 120 and the solder ball 130. According to an embodiment of the invention, when a paste for the adhesive including a curing agent with flux function is used, after the curing agent with flux function removes the oxide film on the surface of the solder ball 130 during the reflow process, the epoxy resin can be cured to extend along the side surface of the solder ball 130 to the lower surface 121 of the second circuit board 120. Additionally, due to the pressing of the second circuit board 120 during the reflow process, the filling paste can be cured into a raised shape along the edge of the lower surface 121 of the second circuit board 120. Therefore, no separate flux cleaning process is required after reflow, and the reflow and solder ball strengthening processes can be performed simultaneously.

[0134] Figure 9 This is a cross-sectional view of a ball grid array package according to another embodiment of the present invention. Figure 10 This is a graph illustrating the compositional variations of each layer in a ball grid array package according to yet another embodiment of the present invention. (The reference numerals are omitted.) Figures 1 to 8 Redundant descriptions of content that is identical to the content described.

[0135] refer to Figure 9 The ball grid array package 100 includes a first circuit board 110, a second circuit board 120 disposed on the first circuit board 110, and a plurality of solder balls 130 disposed between the first circuit board 110 and the second circuit board 120 and spaced apart from each other.

[0136] According to an embodiment of the present invention, a first layer 180 and a second layer 190 are sequentially disposed between the pad 112 and the solder ball 130 of the first circuit board 110 in a direction from the pad 112 to the solder ball 130. That is, the first layer 180 is disposed on the pad 112 between the pad 112 and the solder ball 130 of the first circuit board 110, and the second layer 190 is disposed on the first layer 180 between the first layer 180 and the solder ball 130.

[0137] In this case, pad 112, first layer 180, second layer 190 and solder ball 130 have different compositions.

[0138] As described above, pad 112 comprises a conductive metal. Therefore, in this specification, pad 112 may be referred to as a metal pad. For example, pad 112 may comprise copper (Cu).

[0139] The second layer 190 and solder balls 130 include tin (Sn).

[0140] Therefore, the first layer 180 is an alloy layer comprising the metal included in the pad 112 and tin (Sn) included in the second layer 190. When the pad 112 comprises Cu, the first layer 180 may be an alloy layer comprising Cu and Sn. An example of the pad 112 comprising Cu will be described below.

[0141] The first layer 180 is a layer formed when the pads 112 of the first circuit board 110 and the second layer 190 melt during the reflow process of bonding the pads 112 and solder balls 130 of the first circuit board 110, and may be referred to as an intermetallic compound (IMC) layer.

[0142] According to embodiments of the present invention, the thickness of the first layer 180 can be in the range of 0.1 μm to 2 μm, preferably 0.2 μm to 1.8 μm, or more preferably 0.3 μm to 1.6 μm. The strength of the first layer 180 is lower than that of the second layer 190 and the solder ball 130. Therefore, the thicker the first layer 180, the greater the possibility of cracks occurring within the first layer 180 and at its interface. In particular, when the thickness of the first layer 180 exceeds 2 μm, the possibility of cracks occurring in the first layer 180 due to external impacts such as thermal shock or vibration increases.

[0143] According to an embodiment of the present invention, the pad 112 may include Cu, and the solder ball 130 may be a SnAgCu-based solder ball comprising tin (Sn), silver (Ag), and Cu. For example, the solder ball 130 may include Sn 3.0 Ag 0.5 When the solder balls 130 are based on SnAgCu solder, they can exhibit higher solderability and thermal fatigue resistance than SnPb-based solder. However, SnAgCu-based solder is more expensive than SnPb-based solder. Due to the higher melting point (40°C) of SnAgCu-based solder, the IMC layer can grow rapidly and become thicker. Consequently, the ball grid array package may degrade, and its reliability may decrease.

[0144] According to an embodiment of the present invention, a SnBi-based solder material with a melting point lower than that of the solder ball 130 is applied between the pad 112 and the solder ball 130, which is a SnAgCu-based solder, and then a reflow process is performed.

[0145] Therefore, the thickness of the first layer 180, which serves as the IMC layer, can be adjusted to be in the range of 0.1 μm to 2 μm, and the solder ball 130, which is a SnAgCu-based solder, reacts with a SnBi-based solder material to generate a second layer 190 comprising Sn, Ag, Cu, and Bi. Compared to brittle SnBi-based solder materials, the second layer 190, comprising Sn, Ag, Cu, and Bi, can readily absorb or mitigate impacts and thus can exhibit high reliability.

[0146] When pad 112 includes Cu and solder ball 130 includes Sn 3.0 Ag 0.5 When Cu is used, solder balls 130 are coated with Sn58Bi solder material, and then a reflow process is performed to form a first layer 180 with Cu6Sn5 composition and a Sn... 30 Bi2Ag 0.2 The second layer of Cu composition, 190.

[0147] refer to Figure 10 (a) and Figure 10 (b) According to an embodiment of the invention, the second layer 190 includes a section in which the content of Bi increases and then decreases from the interface between the first layer 180 and the second layer 190 to the interface between the second layer 190 and the solder ball 130, and the content of Cu decreases and then increases. In this way, when the first layer 180 and the second layer 190 are formed by the reaction between the solder material of pad 112, SnBi, and the solder ball 130, the content of Bi and the content of Cu in the second layer 190 can be gradually changed. Therefore, since the interface between the first layer 180 and the second layer 190 and the interface between the second layer 160 and the solder ball 130 are not clearly distinguished, and the coefficients of thermal expansion in the pad 112, the first layer 180, the second layer 190, and the solder ball 130 gradually change, warping of the ball grid array package due to thermal shock can be prevented, and the possibility of cracking along the interface can also be reduced.

[0148] According to an embodiment of the present invention, the segment comprising the highest point P1 of Bi content in the second layer 190 may coincide with the segment comprising the lowest point P2 of Cu content in the second layer 190. Here, the coincidence between the segment comprising the highest point P1 of Bi content and the segment comprising the lowest point P2 of Cu content can mean that the distance between the highest point P1 of Bi content and the lowest point P2 of Cu content is within 20% of the thickness of the second layer 190, preferably within 10%, or more preferably within 5%. Here, the distance between the highest point P1 of Bi content and the lowest point P2 of Cu content can be the distance in the direction from the first circuit board 110 to the second circuit board 120. Therefore, the second layer 190 can have a stable composition to exhibit excellent brittleness and be resistant to external impacts.

[0149] Figure 11 This is a cross-sectional view of a ball grid array package according to another embodiment of the present invention. Figure 12 This is a cross-sectional view of a ball grid array package according to another embodiment of the present invention. (The reference numerals are omitted.) Figures 9 to 11 Redundant descriptions of content that is identical to the content described.

[0150] refer to Figure 11 and Figure 12 The first layer 180 and the second layer 190 are sequentially disposed between the pad 112 and the solder ball 130 of the first circuit board 110 in the direction from the pad 112 to the solder ball 130. That is, the first layer 180 is disposed on the pad 112 between the pad 112 and the solder ball 130 of the first circuit board 110, and the second layer 190 is disposed on the first layer 180 between the first layer 180 and the solder ball 130.

[0151] In this case, such as Figure 11 As shown, a second layer 190 can be disposed between the first layer 180 and the solder ball 130, and can extend from the lower surface of the solder ball 130 along the side surface of the solder ball 130 toward the second circuit board 120. That is, the solder ball 130, which is a SnAgCu-based solder, can react with a SnBi-based solder material, such that the second layer 190, comprising Sn, Ag, Cu, and Bi, can extend from the lower surface of the solder ball 130 along the side surface of the solder ball 130 toward the second circuit board 120. Therefore, the second layer 190 can not only improve the bonding strength between the solder ball 130 and the pad 112, but also strengthen the side surface of the solder ball 130, thereby minimizing the problem of cracking in the solder ball 130 even under frequent thermal shocks or external impacts.

[0152] Alternatively, such as Figure 12 As shown, a second layer 190 can be disposed between the first layer 180 and the solder ball 130, and can be configured to extend from the lower surface of the solder ball 130 along the side surface of the solder ball 130 to the lower surface 121 of the second circuit board 120. That is, the solder ball 130, as a SnAgCu-based solder, can react with a SnBi-based solder material, such that the second layer 190, comprising Sn, Ag, Cu, and Bi, can be configured to extend from the lower surface of the solder ball 130 along the side surface of the solder ball 130 to the lower surface 121 of the second circuit board 120. Therefore, the second layer 190 can improve the bonding strength between the solder ball 130 and the pad 112, strengthen the side surface of the solder ball 130, and also improve the bonding strength between the solder ball 130 and the lower surface 121 of the second circuit board 120, thereby minimizing the problem of cracking in the solder ball 130 even under frequent thermal shocks or external impacts.

[0153] In this configuration, the second layer 190 disposed on the side surface of each solder ball 130 can be spaced apart from the second layer 190 disposed on the side surface of another adjacent solder ball 130. That is, a gap can exist between the second layer 190 disposed on the side surface of each solder ball 130 and the second layer 190 disposed on the side surface of another adjacent solder ball 130. Therefore, due to the superior brittleness of the second layer 190 compared to SnBi-based solder materials, the second layer 190 can protect each solder ball 130 from thermal shock or external physical impact without completely filling the space between the multiple solder balls 130 that are spaced apart from each other.

[0154] Although not shown, adhesive may be further applied in at least some areas between a plurality of solder balls 130 spaced apart from each other between the first circuit board 110 and the second circuit board 120.

[0155] Although not shown, a filler member may be further provided on the first circuit board 110 along the edge of the second circuit board 120.

[0156] Descriptions of adhesives and filler components can be found in references. Figures 1 to 8 The adhesive 150 and the filler member 170 are applied in the same manner as described above.

[0157] Figure 13 This is a flowchart illustrating the process of manufacturing a ball grid array package according to an embodiment of the present invention.

[0158] refer to Figure 13 (a) A second circuit board 120, wherein a plurality of solder balls 130 are attached to its lower surface, and references Figure 13 (b) A first circuit board 110 is provided in which pads 112 are disposed on its upper surface. As described above, although not shown, IC chip 140 may be disposed on the upper surface of second circuit board 120, and the first circuit board 110 may be a single-layer or multi-layer printed circuit board including pads 112 disposed on the upper surface 111.

[0159] refer to Figure 13(c) The pads 112 of the first circuit board 110 are coated with a SnBi-based solder material. Here, the SnBi-based solder material may be Sn58Bi. The SnBi-based solder material may have a melting point lower than that of the solder ball 130. For example, when the solder ball 130 is based on SnAgCu solder, the melting point of the solder ball 130 may be about 220°C, and the melting point of the SnBi-based solder material may be about 139°C. The pads 112 of the first circuit board 110 may be coated with the SnBi-based solder material by screen printing, but the invention is not limited thereto. The pads 112 of the first circuit board 110 may also be coated with the SnBi-based solder material by dispensing.

[0160] refer to Figure 13 (d) A second circuit board 120, on which a plurality of solder balls 130 are disposed on the lower surface 121, is disposed on the first circuit board 110. In this case, the plurality of solder balls 130 may be disposed on the pads 112 of the first circuit board 110. Although not shown, the IC chip 140 may be pre-disposed on the upper surface 122 of the second circuit board 120.

[0161] refer to Figure 13 (e) Perform a reflow process. The reflow process can be performed at a temperature higher than the melting point of the SnBi-based solder material and the solder ball 130. For example, the reflow process can be performed at a temperature lower than the melting point of the SnBiAgCu-based solder, which has a novel composition formed by the reaction between the SnBi-based solder material and the SnAgCu-based solder ball 130. For example, the reflow process can be performed at a temperature higher than 139°C and lower than 175°C. Therefore, a second layer 190 comprising a SnBiAgCu-based solder with a novel composition can be formed by the reaction between the SnBi-based solder material and the SnAgCu-based solder ball 130. Furthermore, a first layer 180, which is an IMC layer comprising Cu and Sn, can also be formed by the reaction between the pad 112 and the SnBi-based solder material.

[0162] Table 2 shows the reliability test results based on the comparative examples and embodiments. Figure 14 A cross-sectional view of a ball grid array package according to comparative examples and embodiments is shown.

[0163] According to Comparative Example 11, the pads 112 of the first circuit board 110 made of Cu and the pads of the Sn3Ag-made circuit board 110 were tested at a temperature of 220°C. 0.5 The solder balls made of Cu are reflowed.

[0164] According to Comparative Example 12, the pads 112 of the first circuit board 110 made of Cu and the solder balls made of Sn58Bi were reflowed at a temperature of 139°C.

[0165] According to Example 11, on the pads 112 of the first circuit board 110 made of Cu and Sn3Ag... 0.5 The solder balls made of Cu are coated with Sn58Bi solder material, and then reflowed at a peak temperature of 175°C.

[0166] [Table 2]

[0167]

[0168] Figure 14 (a) is a cross-sectional view of the ball grid array package manufactured according to Comparative Example 11, and Figure 14 (b) is a cross-sectional view of the ball grid array package manufactured according to Example 11.

[0169] Refer to Table 2 and Figure 14 (a) Comparative Example 11, when the pads 112 of the first circuit board 110 made of Cu and the pads of Sn3Ag made of Sn3Ag are subjected to a temperature of 220°C. 0.5 When Cu-made solder balls are reflowed, it can be seen that the thickness of the Cu6Sn5 IMC layer exceeds 2μm, specifically in the range of 2.35μm to 4.25μm. When the thickness of the Cu6Sn5 IMC layer exceeds 2μm, the possibility of cracking occurring within the IMC layer, along the interface between the solder pad 112 and the IMC layer, or along the interface between the IMC layer and the solder ball 130 is high.

[0170] On the other hand, refer to Table 2 and Figure 14 Example 11 of (b) involves bonding pads 112 of a first circuit board 110 made of Cu with Sn3Ag. 0.5 When a Sn58Bi-based solder material is applied between Cu solder balls and then reflowed at a peak temperature of 175°C, it can be seen that the thickness of the Cu6Sn5 IMC layer is 2 μm or less, specifically in the range of 0.3 μm to 1.56 μm. When the thickness of the Cu6Sn5 IMC layer is 2 μm or less, the possibility of cracking within the IMC layer, along the interface between the pad 112 and the IMC layer, or along the interface between the IMC layer and the solder ball 130 can be reduced.

[0171] Meanwhile, when comparing Comparative Example 12 with Example 11, it can be seen that the shear strength of Comparative Example 12 is higher than that of Example 11, but the drop strength of Comparative Example 12 is very weak. This is because SnBi-based solder is brittle and therefore cannot buffer or absorb impact.

[0172] In other words, according to Example 11, it can be seen that Example 11 has higher shear strength and higher drop strength than Comparative Example 11, and has significantly higher drop strength than Comparative Example 12.

[0173] Furthermore, in the thermal shock test performed under the condition of temperature changing from -40°C to 80°C and the dwell time being 10 minutes, it can be seen that the structure according to Example 11 obtains higher reliability results than the structures according to Comparative Examples 11 and 12.

[0174] According to an embodiment of the present invention, since the solder ball 130 comprises SnAuCu-based solder and has excellent solderability and high thermal fatigue resistance, a low-temperature reflow process is possible, thereby preventing warping caused by a high-temperature reflow process.

[0175] Furthermore, according to embodiments of the present invention, the thickness of the IMC layer between the pad 112 and the solder ball 130 can be minimized, thereby preventing cracks within the IMC layer, at the interface between the pad and the IMC layer, or at the interface between the IMC layer and the solder ball.

[0176] Furthermore, according to embodiments of the present invention, since the surface of the solder ball 130 is surrounded by a solder layer based on SnBiAgCu, a ball grid array package with high shear strength, high drop strength and improved thermal shock resistance reliability can be obtained.

[0177] Furthermore, according to embodiments of the present invention, reliability due to thermal shock can be improved without performing a bottom filling process for filling the space between multiple solder balls, thereby reducing manufacturing processes and time.

[0178] Although the invention has been described with reference to exemplary embodiments, those skilled in the art will understand that various modifications and changes can be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A ball grid array package, comprising: First circuit board; A second circuit board disposed on the first circuit board; The first and second solder balls are configured to be spaced apart from each other between the first circuit board and the second circuit board. A first adhesive is disposed between the first circuit board and the second circuit board, extending from the upper surface of the first circuit board along the first side surface of the first solder ball to the lower surface of the second circuit board; and A second adhesive is disposed between the first circuit board and the second circuit board, extending from the upper surface of the first circuit board along the second side surface of the second solder ball to the lower surface of the second circuit board. In this configuration, the first side surface of the first solder ball and the second side surface of the second solder ball are positioned to face each other. The first adhesive and the second adhesive form a channel region between the first circuit board and the second circuit board, and The area of ​​the channel region is in the range of 30% to 70% of the area of ​​the partition region between the first side surface of the first solder ball and the second side surface of the second solder ball.

2. The ball grid array package according to claim 1, wherein, The area of ​​the channel region is in the range of 50% to 70% of the area of ​​the partition region between the first side surface of the first solder ball and the second side surface of the second solder ball.

3. The ball grid array package according to claim 1, wherein, The maximum width of the channel region between the first adhesive and the second adhesive is 50% or greater than the diameter of at least one of the first solder ball and the second solder ball.

4. The ball grid array package according to claim 3, wherein, At least one of the horizontal thickness of the first adhesive on the first side surface of the first solder ball and the horizontal thickness of the second adhesive on the second side surface of the second solder ball on the centerline between the first circuit board and the second circuit board is in the range of 10% to 50% of the diameter of at least one of the first solder ball and the diameter of the second solder ball.

5. The ball grid array package according to claim 1, wherein, At least one of the horizontal thickness of the first adhesive on the first side surface of the first solder ball and the horizontal thickness of the second adhesive on the second side surface of the second solder ball is in the range of 5 μm to 20 μm along the center line between the first circuit board and the second circuit board.

6. The ball grid array package according to claim 1, wherein, The first adhesive and the second adhesive meet each other on at least one of the upper surface of the first circuit board and the lower surface of the second circuit board.

7. The ball grid array package according to claim 1, wherein, At least one of the first adhesive and the second adhesive includes a region in which the thickness decreases in a direction parallel to the first circuit board or the second circuit board, and then increases again in a direction from the first circuit board to the second circuit board.

8. The ball grid array package according to claim 1, wherein, The first and second adhesives comprise epoxy resin, a curing agent with fluxing properties, and inorganic fillers, and The curing agent with flux function includes acid anhydride and rosin acid.

9. The ball grid array package according to claim 8, wherein, The curing agent with flux function includes hexahydromethyl phthalic anhydride and rosin.

10. The ball grid array package according to claim 8, wherein, The epoxy resin includes naphthyl epoxy resin.

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