JP4376262B2 - Manufacturing method of mounting body of semiconductor device and wiring board - Google Patents

Description

  The present invention relates to a mounting body of a semiconductor device and a wiring board in which a semiconductor device such as a semiconductor package is mounted on the wiring board.

  In recent years, a BGA (Ball Grid Array) structure using solder balls as external connection terminals has been attracting attention in order to reduce the size and increase the number of pins of a semiconductor package. In a semiconductor package having a BGA structure, solder balls are mounted on the back surface of the insulating substrate for mounting the semiconductor chip (the surface opposite to the main surface on which the semiconductor chip is mounted). In general, an alloy containing Sn and Pb (lead) is used as a material for solder balls. When the semiconductor package is mounted on the wiring board, the solder balls are soldered to the connection terminals of the wiring board to ensure electrical connection between the semiconductor chip and the wiring board.

  By the way, when the semiconductor chip generates heat during operation, stress may be applied to the solder ball due to a difference in thermal expansion between the semiconductor package and the wiring board, and the solder ball may be damaged. Damage to the solder balls leads to poor connection on the mounted wiring board. Therefore, a countermeasure for suppressing the occurrence of such defects is desired. In addition, in recent years, from the viewpoint of environmental protection, it is also required not to use Pb.

  Accordingly, an object of the present invention is to provide a mounting body of a semiconductor device and a wiring board that can eliminate Pb and reduce the occurrence of defects.

  In order to achieve the above object, a mounting body of a semiconductor device and a wiring board according to the present invention includes a semiconductor chip, a mounting portion electrically connected to an electrode pad of the semiconductor chip, and an external mounted on the mounting portion. A semiconductor device having a connection terminal; and a wiring substrate having an insulating substrate and a connection terminal portion formed on the insulating substrate, and the external connection terminal of the semiconductor device is connected to the connection terminal portion of the wiring substrate. In the mounted body, the external connection terminal contains Sn (tin), Ag (silver), Cu (copper), and Au (gold).

  Moreover, in this invention, it is preferable that the connection terminal part of the said wiring board has a layer containing Au.

  Furthermore, in the present invention, it is preferable that the mounting portion of the semiconductor device has a layer containing Au.

  Furthermore, in the present invention, the layer containing Au is preferably formed on the layer containing Ni.

  In addition, the Au content in the external connection terminal is preferably 0.1 wt% or more and 12.0 wt% or less.

  In the present invention, the content of Ag in the external connection terminal is preferably 1.0 wt% or more and 3.5 wt% or less.

  Further, the Cu content in the external connection terminal is preferably 0.5 wt% or more and 1.0 wt% or less.

  In addition, it is preferable that the conductive paste used when mounting the semiconductor device on the wiring board contains Sn, Ag, and Cu.

  As described above, according to the present invention, the conductive ball uses a conductive ball containing Sn, Ag, and Cu, and Au is used for at least one of the conductive ball, the mounting portion of the semiconductor device, and the connection terminal of the wiring board. Because it is included, the conductive ball after the mounting process can be made to contain Au, the bonding strength of the conductive ball is improved, the fatigue life is improved, the conductive ball is damaged, etc. The accompanying defects can be reduced.

  Hereinafter, the present invention will be described in detail based on the illustrated embodiment. FIG. 1 is a partially cutaway perspective view showing the entire structure of a semiconductor package to which the present invention is applied. As shown in FIG. 1, in the semiconductor package (semiconductor device) 100 in this embodiment, the semiconductor chip 102 is fixed to the main surface of the insulating substrate 104 using a die paste 106 and sealed with a sealing material 108. It is a thing. The semiconductor chip 102 is obtained by forming an integrated circuit (not shown) on one surface (upper surface in the drawing) of a silicon substrate. A large number of electrode pads 110 drawn from the integrated circuit are arranged on the outer periphery of the surface of the semiconductor chip 102 on the integrated circuit side.

  The insulating substrate 104 is a substrate made of polyimide or ceramics. A conductive pattern 112 made of Cu is formed on the main surface of the insulating substrate 104, and solder balls (conductive balls) 114 that are external connection terminals are provided on the back surface of the insulating substrate 104. The conductor pattern 112 is connected to the electrode pad 110 of the semiconductor chip 102 via the conductor wire 116 and also connected to the solder ball 114 via the via hole 118 drilled in the insulating substrate 104.

  The solder ball 114 has a spherical shape with a diameter of about 0.25 mm, is made of an alloy containing Sn, Ag, and Cu, and the Ag content is 1.0 to 3.5 wt%. The content of Cu is 0.5 to 1.0% by weight. The solder balls 114 are connected to the connection terminals 208 on the wiring board side when the semiconductor package 100 is mounted on the wiring board 200 (FIG. 2) such as a wiring board.

  FIG. 2 is an enlarged cross-sectional view showing a state where the semiconductor package 100 is mounted on the wiring board 200. In the wiring substrate 200, a conductive layer 204 made of Cu is formed on the surface of an insulating substrate 202 made of resin, and the surface of the conductive layer 204 is covered with an insulating layer 206. The insulating layer 206 is formed so as to expose only a portion to be the connection terminal 208 in the conductive layer 204. The thickness of the insulating substrate 202 is 0.4 mm to 3.0 mm, and the thickness of the conductive layer 204 is 10 μm to 50 μm. The insulating layer 206 has a thickness of 3 μm to 50 μm.

  A Ni layer 210 is formed on the surface of the conductive layer 204 in the connection terminal 208 by Ni (nickel) plating. An Au layer 212 is formed on the surface of the Ni layer 210 by Au plating. The thickness of the Ni layer 210 is 1 μm to 10 μm. The Au layer 212 is formed in such a thickness that the Au content in the solder ball 114 is 0.1 to 12% by weight when the Au atoms diffuse into the solder ball 114 as described later.

  The solder balls 114 described above are fixed to the surface of the Au layer 212 of the connection terminal 208 via a solder paste (conductive paste) 214. The solder paste 214 preferably has the same composition as that of the solder balls 114, but may have another composition (for example, an alloy composed of Sn and Pb).

  The above-described via hole 118 is formed in the insulating substrate 104 of the semiconductor package 100. In this via hole 118, a Ni layer 220 is formed on the lower surface of the conductor pattern 112 in the drawing, and an Au layer 222 is formed on the lower surface of the Ni layer 220 in the drawing. The thickness of the insulating substrate 104 is 75 μm to 100 μm. The Ni layer 220 has a thickness of 1 μm to 10 μm, and the Au layer 222 has a thickness of 0.1 μm to 2.0 μm. The via hole 118, the Ni layer 220, and the Au layer 220 serve as a mounting portion for mounting the solder ball 114 via a solder paste (not shown).

  In the present embodiment, the Au layers 212 and 222 are provided at positions in contact with the solder balls 114 because the Au atoms of the Au layers 212 and 222 are soldered when the solder balls 114 are heated and connected to the connection terminals 208. This is for diffusion into the ball 114. This is because when Au diffuses into the solder ball 114, the solder ball 114 has a composition containing Sn, Ag, Cu, and Au, and can increase the connection strength and improve the fatigue life.

  The reason why the solder ball 114 contains Ag and Cu in addition to the main component Sn is that the strength can be secured and the creep resistance can be improved without using Pb.

  Next, a mounting method for mounting the semiconductor package 100 on the wiring board 200 will be described. FIG. 3 shows an outline of a method for manufacturing the semiconductor package 100. First, as shown in FIG. 3A, a via hole 118 is formed in the insulating substrate 104 by photolithography or punching. Next, as shown in FIG. 3B, a conductor pattern 112 is formed on the main surface of the insulating substrate 104 in which the via hole 118 is formed by using a photolithography method. Subsequently, as shown in FIG. 3C, a die paste 106 made of epoxy resin is dropped on the chip mounting region on the insulating substrate 104. Further, as shown in FIG. 3D, the semiconductor chip 102 manufactured in another process is pressed against the die paste 106, the ambient temperature is raised by a heater or the like, the die paste 106 is cured, and the semiconductor is formed on the insulating substrate 104. The chip 102 is fixed.

  After fixing the semiconductor chip 102 to the insulating substrate 104, the electrode pads 110 and the wire connection lands 120 of the semiconductor chip 102 are bonded with the conductor wires 116 as shown in FIG. After the bonding is completed, the semiconductor chip 102 is sealed with a sealing material 108 made of mold resin. Subsequently, as shown in FIG. 3F, a Ni layer 220 and an Au layer 222 are sequentially formed on the conductor pattern 112 in the via hole 118 of the insulating substrate 102, and then solder paste using a squeegee or the like. And solder balls 114 are attached through the solder paste. The semiconductor package 100 is completed through the above steps.

  4A and 4B show an outline of the manufacturing process of the wiring board 200. FIG. First, as shown in FIG. 4A, a conductive layer 204 made of Cu is formed on the surface of the insulating substrate 202. Next, as shown in FIG. 4B, an Ni layer 210 and an Au layer 212 are sequentially formed on the surface of the conductive layer 204 by plating, and the insulating layer 206 is removed except for portions corresponding to the connection terminals 208. Cover with.

  Subsequently, as illustrated in FIG. 4C, the semiconductor package 100 is mounted on the wiring substrate 200. That is, a solder paste (not shown in FIG. 4) is applied in advance to the surface of the Au layer 212 of the connection terminal 208 of the wiring board 200, the solder balls 114 of the semiconductor package 100 are brought into contact, and a heat treatment at about 220 ° C. to 250 ° C. is performed. Do. As a result, the solder balls 114 of the semiconductor package 100 and the connection terminals 208 of the wiring board 200 are connected. As a result, a mounting wiring board (wiring board on which a semiconductor is mounted) obtained by mounting the semiconductor package 100 on the wiring board 200 is obtained. When the solder ball 114 is fixed to the connection terminal 208, the Au atoms of the Au layers 212 and 222 diffuse into the solder ball 114, so that the solder ball 114 contains Au in addition to Sn, Ag, and Cu. Connection strength and fatigue life can be obtained.

  As described above, in the present embodiment, the solder ball 114 having a composition containing Sn, Ag, and Cu is used, and Au is diffused into the solder ball 114 when the semiconductor package 100 is mounted on the wiring board 200. Thus, the fatigue strength is improved by increasing the connection strength. Accordingly, it is possible to eliminate Pb and reduce the occurrence of defects due to breakage of the solder balls 114 or the like.

  In particular, the high tensile strength and shear strength of the solder ball 114 can be obtained by making the Au content in the solder ball 114 0.1 to 12% by weight.

  Furthermore, in the composition of the solder balls 114, the creep resistance can be improved by setting the Ag content to 1 to 3.5% by weight and the Cu content to 0.5 to 1.0% by weight. it can.

  Instead of forming the Au layers 212 and 222 on the connection terminals 208 of the wiring board 200, the solder balls 114 may contain Au from the beginning. In this case, the solder ball 114 is made of an alloy containing Sn, Ag, Cu, and Au. The content of Au is 0.1 to 12% by weight. Moreover, the content rate of Ag is 1.0 to 3.5 weight% similarly to embodiment mentioned above, The content rate of Cu is 0.5 to 1.0 weight%. Even in this case, since the solder ball 114 contains Au, the bonding strength and fatigue life are improved, and the occurrence of defects due to breakage of the solder ball 114 or the like can be reduced.

  Next, the effects of the above-described embodiment will be described based on specific numerical examples. First, the test results on the viscoelasticity of the solder material will be described. Here, each test piece was made of a solder material having two compositions of Sn, Ag, and Cu. Composition 1 contains 3.5 wt% Ag and 0.75 wt% Cu, and composition 2 contains 1.0 wt% Ag and 0.5 wt% Cu. As shown in FIG. 5A, the test piece is a cylinder having a length L1 of 140 mm and an outer diameter D1 of 15 mm, and has a shape in which the outer diameter of the central region in the length direction is reduced. The portion with a thin outer diameter has a length L2 of 50 mm and an outer diameter D2 of 10 mm. Each test piece was subjected to a tensile test at three different temperatures (−25 ° C., + 25 ° C., and + 125 ° C.), and the relationship between strain rate and yield stress was examined. The results are shown in FIGS. 5B and 5C, respectively. FIG. 6 shows the result of a similar test performed on a conventional solder material containing Pb (that is, a solder material containing 63 wt% Sn and 37 wt% Pb). 5 and 6, the vertical axis represents the strain rate, and the horizontal axis represents the stress.

  From FIGS. 5 and 6, it was found that compositions 1 and 2 have a property that they are less susceptible to strain rate, especially under low stress, that is, excellent in creep resistance as compared with conventional solder materials. .

  Next, the test results regarding the bonding strength of the solder material will be described. As shown in FIG. 7A, the end surfaces of the two copper plates 600 were joined to each other using the solder materials 602 having compositions 1 and 2. Each copper plate 600 has a length L of 59 mm, a width W of 15 mm, and a thickness t of 0.9 mm. At this time, the joint end face is pre-plated with Ni (thickness 3 μm), the Ni plating (thickness 3 μm) is further plated with Au (thickness 0.6 μm), and completely plated A tensile test was carried out for each of those that were not. FIG. 7B shows the test results for composition 1, and FIG. 7C shows the test results for composition 2. From FIG. 7B and FIG. 7C, it can be seen that, for both Composition 1 and Composition 2, Au plating on Ni plating shows the highest bonding strength. This is presumably because Au diffused into the solder material during soldering.

  Next, the test results on the relationship between the Au content and strength in the composition composed of Sn, Ag, Cu, and Au will be described. Here, Ag was fixed at 1.0 wt% and Cu was fixed at 0.5 wt%, and the test piece was prepared by changing the Au content, and the tensile strength and shear strength were measured for each test piece. . FIG. 8 shows the measurement results. From FIG. 8, particularly high tensile strength is obtained when the Au content is 0.1 to 12.0% by weight, and particularly high when the Au content is 0.1 to 9.0% by weight. It was found that shear strength can be obtained.

  Next, a result of a temperature cycle test performed by mounting the semiconductor package 100 described above on the wiring board 200 will be described. Here, as an example, a semiconductor package 100 having a size of 9 mm × 6 mm and having 103 balls (arrangement pitch 0.5 mm) was used. The size of the semiconductor chip 102 was 5 mm × 3 mm × 0.28 mm. The diameter of the solder ball 114 was 0.25 mm, and the composition was composition 1 described above. The composition of the solder paste 214 was the composition 2 described above. The thickness of the wiring board 200 was 0.8 mm, and the inner diameter of the connection terminal 208 was 0.3 mm. The connection terminal 208 was formed with a Ni layer 210 having a thickness of 3 μm and an Au layer 212 having a thickness of 0.6 μm. In addition, the Au content was 6.9% by weight in a state where Au was diffused into the solder balls 114.

  In the temperature cycle test, the temperature was alternately changed between −40 ° C. and 125 ° C., and the duration of each temperature was 10 minutes. The time required for temperature increase / decrease was 5 minutes. In such a temperature cycle test, it was examined whether or not a crack occurred in the solder joint. Further, as a comparative example, a test was performed in the same manner on a case where the mounting was performed without forming the Au layers 212 and 222 and the Ni layers 210 and 220. The test results are shown in FIG. In FIG. 9, the horizontal axis represents the number of cycles, and the vertical axis represents the defect occurrence rate.

  From FIG. 9, the initial failure appeared in 900 cycles in the comparative example, whereas the initial failure did not appear until 1000 cycles in the present example, and the effect of suppressing the occurrence of failure was observed. That is, it has been found that the occurrence of defects can be reduced by providing the Au layers 212 and 222 and the Ni layers 210 and 220 to improve the bonding strength and fatigue life of the solder balls 114.

  Although illustration is omitted, the composition of the solder paste 214 is SnPb (Sn is 63% by weight, Pb is 37% by weight), and the composition of the solder ball 114 is SnAgCu (Ag is 1.0% by weight; When mounting was performed with Cu being 0.5% by weight, and the above-described temperature cycle test was performed on the mounted wiring board, initial defects appeared at 900 cycles. On the other hand, the composition of the solder paste 214 and the solder ball 114 is both SnPb (Sn is 63 wt%, Pb is 37 wt%), and the above-described temperature cycle test is performed on the mounted wiring board. Initial defects appeared after 500 cycles. From this, it was found that the occurrence of defects can be reduced by diffusing Au into solder balls having the SnAgCu composition regardless of the composition of the solder paste.

  The embodiments of the present invention have been described with reference to the drawings. However, the present invention is not limited to the matters shown in the above-described embodiments, and it is obvious that changes, improvements, etc. can be made based on the description of the scope of claims. For example, although solder balls are shown as external connection terminals of a semiconductor device in the above-described embodiments, it will be apparent to those skilled in the art that solder lands or the like may be used instead of solder balls.

1 is a partially cutaway perspective view showing a structure of a semiconductor package according to an embodiment of the present invention. It is sectional drawing which shows the state which mounted the semiconductor package shown in FIG. 1 on the wiring board. FIG. 3 is a cross-sectional view for each process showing a manufacturing process of the semiconductor package shown in FIG. 1. FIG. 3 is a cross-sectional view for each process showing a process of mounting the semiconductor package shown in FIG. 1 on a wiring board. It is a figure which shows the viscoelasticity of the solder material in this Embodiment. It is a figure which shows the viscoelasticity of the conventional solder material. It is a figure which shows the relationship between the presence or absence of Ni layer and Au layer, and joining strength. It is a figure which shows the relationship between the content rate of Au, tensile strength, and shear strength. It is a figure which shows the result of having mounted the semiconductor package 100 on the wiring board 200, and having performed the temperature cycle test.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100: Semiconductor device 102: Semiconductor chip 104: Insulating substrate 106: Die paste 108: Sealing material 112: Conductive pattern 114: Solder ball 118: Via hole 200: Wiring board 202: Conductive layer 208: Connection terminal 210, 221: Ni layer 212, 222: Au layer 214: Solder paste

Claims (5)

A semiconductor device having a semiconductor chip, a mounting portion electrically connected to an electrode pad of the semiconductor chip, and an external connection terminal mounted on the mounting portion, an insulating substrate, and a connection terminal portion formed on the insulating substrate A mounting body in which an external connection terminal of the semiconductor device is connected to a connection terminal portion of the wiring board,
The external connection terminal contains Sn (tin) as a main component and contains Ag (silver), Cu (copper), and Au (gold), and the Ag content is 1.0 wt% or more and 3.5 wt%. The Cu content is 0.5 wt% or more and 1.0 wt% or less, the Au content is 0.1 wt% or more and 12.0 wt% or less,
Due to the heat treatment when connecting the external connection terminals, Au diffuses from the layer containing Au provided in the connection terminal portion of the wiring board or the mounting portion of the semiconductor device to the external connection terminals, thereby containing the Au Become a rate,
Manufacturing method of mounting body of semiconductor device and wiring board. The manufacturing method of the mounting body of the semiconductor device and wiring board of Claim 1 whose content rate of the said Au is 0.1 weight% or more and 9.0 weight% or less. The manufacturing method of the mounting body of the semiconductor device and wiring board of Claim 1 or 2 with which the connection terminal part of the said wiring board and the mounting part of the said semiconductor device each have a layer containing Au. The manufacturing method of the mounting body of the semiconductor device and wiring board of Claim 1, 2, or 3 with which the layer containing said Au is formed on the layer containing Ni. The manufacturing method of the mounting body of the semiconductor device and wiring board of Claim 1, 2, 3 or 4 with which the electrically conductive paste used at the time of mounting to the said wiring board of the said semiconductor device contains Sn, Ag, and Cu. .