JP2010086987A - Electronic component module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic component module in which peeling of an external terminal pad, i.e., peeling of an external terminal pad from a substrate owing to impact such as dropping, and solder peeling, i.e., peeling of a solder from the external terminal pad, are prevented or suppressed. <P>SOLUTION: The electronic component module 2 includes: an electronic component 4; and a substrate 10 where the electronic component 4 is mounted on the first main surface 3 and a plurality of external terminal pads 8 to which an electronic circuit device 6 consisting of the electronic components 4 is electrically connected are formed on the second main surface 9. Some or all of a plurality of external terminal pads 8 are reinforced external terminal pads 8 including: a first metal layer where a peripheral end part is partially covered with a resist 20 protecting the second main surface 9; and a second metal layer formed on the exposed surface of the first metal layer including a side surface. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electronic component module, and more particularly to an electronic component module having external terminal pads for mounting on a motherboard.

  Many electronic component modules (transmission modules and the like) are mounted on a mother board of a mobile communication device such as a mobile phone.

  A wiring is provided on a main surface of a main wiring board on which a mother board, that is, an electronic device is formed, and a pad to which an electronic component module and terminals of the electronic component are soldered is provided at an end of the wiring.

  Such an electronic component module is formed using a printed circuit board as a base. Electronic components such as integrated circuit devices and chip components are mounted on the upper surface of a printed wiring board (hereinafter referred to as a substrate) that forms the electronic component module, and external terminal pads are provided on the lower surface. By soldering the external terminal pads to the pads provided on the mother board, the electronic component module is electrically connected to the mother board and mechanically fixed.

  By the way, mobile communication devices are carried and used. For this reason, mobile communication devices sometimes fall and receive an impact. At this time, a large force is applied to the external terminal pads that support the electronic component module.

  Many electronic components are mounted on the electronic component module. For this reason, the mass of the electronic component module is significantly larger than that of each electronic component. On the other hand, the external terminal pads for fixing the electronic component module to the motherboard are primarily used for signal input / output and power supply, so the number of external terminal pads provided in the electronic component module is not so much. not many. For this reason, a small number of external terminal pads must support a large impact force generated in the electronic component module when the mobile communication device is dropped. Therefore, the impact force acting on each external terminal pad is enormous.

  This large impact force causes external terminal pad peeling that causes the external terminal pad to peel from the substrate, and solder peeling that causes the solder to peel from the external terminal pad. Such a peeling phenomenon is one of the causes of failure of mobile communication devices and should be prevented as much as possible.

  By the way, the peeling of pads (land peeling) and the peeling of solder (solder peeling) provided on a printed wiring board are phenomena that became a problem even when lead-free solder with a high melting temperature began to be used instead of lead solder. is there.

  In order to solve this problem, a technique has been proposed in which a solder mask (which protects the surface of the printed wiring board) is extended to cover the outer periphery of the pad to prevent land peeling or solder peeling (Patent Document 1). ). However, the phenomenon that became a problem at this time was not the peeling of the external terminal pad or the solder formed thereon, but the peeling of the pad to which an electronic component such as a resistor or a capacitor was soldered or the pad was formed. It is peeling of solder. In addition, such peeling does not occur due to the fall of the printed wiring board, but is another phenomenon caused by contraction when the melted solder cools and solidifies.

Therefore, even if this technique is applied to the external terminal pads of the electronic component module as they are, it is not always possible to prevent peeling of the external terminal pads and peeling of the solder at the external terminal pads.
JP 2001-332851 A JP 2004-71661 A

  As described above, external terminal pad peeling and solder peeling that occur in an electronic component module are phenomena that must be avoided in order to ensure the reliability of mobile communication devices. However, as far as the present inventor is aware, techniques for that purpose have never been studied.

  Therefore, an object of the present invention is to provide an electronic component module that can prevent or suppress external terminal pad peeling from which the external terminal pad peels off the substrate or solder peeling from which the solder peels from the external terminal pad due to an impact such as dropping. Is to provide.

  In order to achieve the above object, an electronic component module of the present invention includes an electronic component and the electronic component mounted on the first main surface, and an electronic circuit device including the electronic component is electrically connected. A plurality of external terminal pads have a substrate formed on the second main surface.

  In the electronic component module according to the present invention, a part or all of the plurality of external terminal pads includes a first metal layer in which a peripheral end portion is partially covered with a resist protecting the second main surface. A reinforced external terminal pad comprising a second metal layer formed on the exposed surface of the first metal layer including side surfaces.

  According to the present electronic component module, it is possible to prevent or suppress external terminal pad peeling from which the external terminal pad is peeled off the substrate or solder peeling from which the solder is peeled off from the external terminal pad due to an impact such as dropping.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the technical scope of the present invention is not limited to these embodiments, but extends to the matters described in the claims and equivalents thereof.

  FIG. 1 is a side view of the electronic component module 2 of the present embodiment. In the drawings that will be described hereinafter, the same parts are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 1, the electronic component module 2 has an electronic component 4 (an integrated circuit device, a resistor, a capacitor, a coil, a transmitter, etc.). The electronic component module 2 has a substrate 10 on which the electronic component 4 is mounted on the first main surface 3. A plurality of external terminal pads 8 to which an electronic circuit device 6 composed of electronic components 4 is electrically connected are formed on the second main surface 9 of the substrate 10 facing the first main surface 3. Yes.

  In FIG. 1, only the pads 5 and the external terminal pads 8 to which the electronic components 4 are connected are shown. However, the electronic components 4 are connected to each other on the surface or inside of the substrate 10 so that the electronic circuit device 6 is connected. A wiring to be formed is formed. These wirings are connected to the pads 5 or the external terminal pads 8 (or electronic components directly formed on the substrate 10).

  FIG. 2 is an enlarged plan view of a region A surrounded by a broken line in FIG. FIG. 3 is a cross-sectional view taken along the line AA of FIG. 2 as seen from the direction of the arrow.

  As shown in FIGS. 2 and 3, the external terminal pad 8 of the present embodiment has a peripheral end 18 (outer peripheral portion) along the upper side 12, the left side 14, and the right side 16 of the second main surface 9. A first metal layer 22 covered with a resist 20 to be protected is provided. The first metal layer 22 is not formed with openings such as through holes. That is, the first metal layer 22 fills up the entire inside of the peripheral end 18.

  Furthermore, the external terminal pad 8 of the present embodiment includes a second metal layer 35 formed on the exposed surface of the first metal layer 22 including the side surface 33.

  FIG. 4 is a plan view of the external terminal pad 24 that the inventor has provided in the electronic component module before the present invention. FIG. 5 is a cross-sectional view taken along the line AA of FIG. 4 as seen from the direction of the arrow.

  As shown in FIGS. 4 and 5, the resist 20 is separated from the external terminal pads 24. Thus, since the previous external terminal pad 24 was only bonded to the substrate 10, it was weak against impact at the time of dropping and easily peeled off from the substrate 10.

  Such external terminal pad isolation first occurs at the peripheral edge of the external terminal pad 8 and then spreads over the entire external terminal pad 8. Therefore, in the present embodiment, the external terminal pad peeling is prevented by covering and reinforcing the peripheral end portion 18 of the external terminal pad 8 that becomes the starting point of peeling with a resist 20 (see FIGS. 2 and 3). .

  By the way, if it is only to prevent external terminal pad peeling, the method proposed for preventing the above-mentioned land peeling (pad peeling due to cooling and solidification of solder) is applied, and the peripheral edge of the external terminal pad is applied. The entire part may be covered with a resist. However, if it does in this way, it will become easy to generate | occur | produce the solder peeling which solder will peel from an external terminal pad by dropping.

  The electronic component module 2 is fixed to the motherboard by soldering the external terminal pads 8 to pads provided on the motherboard (not shown). The external terminal pad 8 is usually formed from a plurality of layers.

  For example, the conventional external terminal pad 24 shown in FIG. 5 is formed by a first metal layer 22 in close contact with the substrate 10 and a second metal layer 35 formed on the surface of the first metal layer 22. (In the example shown in FIG. 3, a third metal layer 32 and a fourth metal layer 34 are interposed between the first metal layer 22 and the substrate 10. For these metal layers, (It will be described later.)

  The first metal layer 22 is an external terminal pad body made of, for example, copper (Cu). On the other hand, the second metal layer 35 is a metal layer for soldering which is more easily bonded to the solder than the first metal layer and is formed of a metal such as gold (Au). That is, the second metal layer 35 is a metal layer that is bonded to a pad formed on a mother board (another substrate) with solder.

  As described above, in the electronic component module, the external terminal pads are soldered to the motherboard. Therefore, when the device including the mother board falls, a large impact force acts on the solder bonding the external terminal pad 24 to the mother board. At this time, since the second metal layer 35 and the solder are firmly bonded, peeling occurs at the interface between the first metal layer 22 and the second metal layer 35, and the solder together with the second metal 35 is Peel from the terminal pad 24.

  If the peripheral edge of the external terminal pad is covered with a resist, the external terminal pad peeling is suppressed, but such solder peeling tends to occur.

  As a result of various studies by the present inventors, the cause of solder peeling is that the peripheral edge of the first metal layer 22 is covered with a resist, and the second metal layer 35 becomes the side surface 33 of the first metal layer 22. It became clear that it was impossible to coat.

  The second metal layer 35 is usually formed by electroless plating after the resist 20 is formed on the surface of the substrate 10. Therefore, when the peripheral end of the first metal layer 22 is covered with the resist 20, the side surface 33 of the first metal layer 22 is not covered with the second metal layer 35.

  When the second metal layer 35 covers the side surface of the first metal layer 22, the second metal layer 35 is applied to the side surface 33 of the first metal layer 22 even when a force for peeling off the second metal layer 35 is applied. The second metal layer 35 is not easily peeled off because the second metal layer 35 is caught.

  Therefore, in the present embodiment, as shown in FIG. 2, by partially covering the peripheral end portion 18 of the first metal layer 22 with the resist 20, a part of the side surface 33 of the first metal layer is the first. It is covered with the second metal layer 35 so that the solder peeling hardly occurs. If it does in this way, external terminal pad peeling and solder peeling can be prevented or suppressed simultaneously.

  Incidentally, in the example shown in FIG. 1, the peripheral end portions of all the external terminal pads 8 provided in the electronic component module 2 are partially covered with the resist 20. However, the impact due to dropping is not applied equally to all the external terminal pads 8.

  Therefore, it is not always necessary to partially cover the peripheral end portion of the external terminal pad 8 with the resist, and only the peripheral end portion of a part of the external terminal pad that receives a greater impact may be covered with the resist to be reinforced. (Hereinafter, the external terminal pad reinforced with the resist in this way is referred to as a reinforced external terminal pad).

  As is clear from the above description, in the electronic component module 2, a part or all of the plurality of external terminal pads 8 are peripheral end portions (outer peripheral portions) by the resist 20 that protects the second main surface 9 of the substrate 10. Is provided with a reinforced external terminal pad 26 including a first metal layer 22 partially covered with a second metal layer 35 formed on an exposed surface of the first metal layer 22 including a side surface 33. . The exposed surface of the first metal layer 22 is a surface that is not covered with the resist 20.

  As described above, the electronic component module 2 of the present embodiment includes the reinforced external terminal pad 26 to prevent or suppress both external terminal pad peeling and solder peeling.

  By the way, the external terminal pads that receive the greatest impact when dropped are the external terminal pads arranged at the four corners of the substrate 10. Therefore, it is preferable to arrange the reinforced external terminal pads 26 as described above at the four corners of the substrate. The external terminal pad 8 that receives the next largest impact force is an external terminal pad arranged along the outer periphery of the substrate 10. Therefore, it is more preferable that the reinforced external terminal pads 26 are arranged along the outer periphery of the substrate. The external terminal pads are often arranged only on the outer peripheral portion of the substrate 10, but may be arranged inside the outer peripheral portion in addition to the outer peripheral portion of the substrate 10.

  In the example described with reference to FIG. 2, the reinforced external terminal pad 26 has a quadrangular shape, and the peripheral end 18 of the first metal layer 22 along the three sides is covered with the resist 20.

  As a result of various studies by the present inventor, as shown in FIG. 2, when the external terminal pad is square, the case where the peripheral end portion of the first metal layer 22 along the three sides of the square is covered with a resist, External terminal pad peeling and resist peeling hardly occurred. That is, in order to prevent or suppress both the external terminal pad peeling and the solder peeling, it is preferable to cover the peripheral end portion of the first metal layer 22 along the three sides of the external terminal pad with a resist.

  However, even if the peripheral edge along one or two sides of the quadrangle is only covered with the resist, there is an effect of preventing or suppressing external terminal pad peeling and solder peeling.

  FIG. 6 is a plan view of the reinforced external terminal pad 26 in which one side of the square is covered with the resist 20. FIG. 7 is a plan view of the reinforced external terminal pad 26 in which two opposite sides of the square are covered with the resist 20. FIG. 8 is a plan view of the reinforced external terminal pad 26 in which two adjacent sides of the quadrangle are covered with the resist 20.

  As described above, only the peripheral end portion of the first metal layer 22 along one side may be covered with the resist, or the periphery of the first metal layer 22 along two opposing sides or two adjacent sides. Only the end portion may be covered with the resist.

  Incidentally, the reinforced external terminal pad 26 shown in FIG. 3 is further reinforced by the third metal layer 32 formed in the through hole 28.

  In the example shown in FIG. 3, the electronic component module 2 has a through hole 28 that penetrates the substrate 10 and has an opening opened on the second main surface 9 closed by the first metal layer 22. Yes. The reinforced external terminal pad 26 has a fourth metal layer 30 bonded to the second main surface 9 and a third metal layer 32 formed on the fourth metal layer 30. . The second metal layer 22 and the first metal layer 35 described above are formed on the third metal layer 32 (that is, the third metal layer 32 is composed of the first metal layer 22 and the substrate). 10).

  The third metal layer 32 described above further extends and adheres to the inner wall of the through hole 28 and is firmly bonded to the substrate 10.

  For this reason, in the electronic component module 2 having the reinforced external terminal pad 26 shown in FIG. 3, the reinforced external terminal pad 26 including the third metal layer 32 and the substrate 10 are firmly bonded, and the external terminal pad peeling is less likely to occur. It has become.

  By the way, although it is not a technique for directly preventing land peeling, a technique for covering only four corners of a square land (pad) with a resist has been proposed (Patent Document 2). Even if the four corners of the external terminal pad 8 are covered with a resist in accordance with this proposal, it is considered possible to suppress the external terminal pad peeling.

  However, in order to carry out the method disclosed in Patent Document 2, it is necessary to cover the four corners of the pad obliquely with a resist, so that the number of steps required for designing the resist pattern increases.

  The resist is formed by spraying or printing using a predetermined mask. Regardless of which method is used, a resist forming mask must be designed by CAD (Computer Aided Design).

  If an attempt is made to cover the four corners of the external terminal pad obliquely with a resist in accordance with Patent Document 2, the number of steps required to design the resist increases. On the other hand, the resist according to the present embodiment covers an area along the side of the quadrangle, and therefore can be easily designed by CAD.

  Since the method disclosed in the method disclosed in Patent Document 2 is based on the premise that the lead of the mounting component is inserted into the through hole and soldered, the opening of the through hole is not blocked. In this method, the second metal layer 35 covering the side surface of the first metal layer 22 is not particularly required.

(1) Configuration FIG. 9 is a cross-sectional view of the electronic component module 39 of the present embodiment.

  As shown in FIG. 9, the electronic component module 39 includes the electronic component 4 and the electronic component 4 mounted on the first main surface 3, and the electronic circuit device 6 including the electronic component 4 is electrically connected. A plurality of external terminal pads (reinforced external terminal pads 26) have a substrate 37 formed on the second main surface 9 that faces the first main surface 3.

  The substrate 37 is a build-up substrate including a base substrate 38 and resin layers 40 and 41 formed on both sides thereof. As shown in FIG. 9, wirings 36 are formed on both surfaces of the base substrate 38, and pads 5 to which the electronic component 4 is soldered are attached to the surface (first main surface 3) of the resin layer 40 on the electronic component side. A wiring (not shown) having the pad 5 as an end is formed. On the other hand, a reinforced external terminal pad 26 is formed on the surface (second main surface 9) of the resin layer 41 on the side opposite to the electronic component 4.

  Here, resists 20 mainly composed of an epoxy resin are formed on the surfaces of the resin layers 40 and 41 to protect the surface of the substrate 37 (including wiring). The resist 20 prevents oxidation of, for example, Cu wiring, and further prevents solder from being attached to the wiring when the electronic component 4 is soldered.

  A via hole is formed in the base substrate 38, and a metal layer 42 is plated on the inner wall thereof. The metal layer 42 connects the wirings 36 formed on both surfaces of the base substrate 38. Furthermore, the inside of the metal layer 42 is filled with an epoxy resin.

  Vias (laser vias) are formed in the resin layers 40 and 41 by laser. The laser via is filled with a metal 46. The metal 46 connects the wiring 36 formed on the base substrate 38 to the pads 5 or the reinforced external terminal pads 26 formed on the surfaces of the resin layers 40 and 41.

  Furthermore, the electronic circuit 6 composed of the electronic component 4 is covered with a metal shield case 48. However, the electronic circuit 6 may be sealed with a mold resin.

  As is clear from the above description, the substrate 37 is a build-up substrate having four wiring layers. The thickness of the substrate 37 is 0.37 mm, and the first and second main surfaces are squares having a side of 8.8 mm.

  FIG. 10 is a perspective view of the electronic component module 39 as seen from the second main surface 9 side on which the reinforced external terminal pads 26 are formed. As shown in FIG. 10, the reinforced external terminal pads 26 are arranged along the outer periphery of the substrate 37. Except for the region where the reinforced external terminal pad 26 is formed, the second main surface 9 is covered with the resist 20.

  FIG. 11 is an enlarged plan view of a region A surrounded by a broken line in FIG. 12 is a cross-sectional view taken along line AA in FIG. 11 as viewed from the direction of the arrow.

  The reinforced external terminal pad 26 is formed on the exposed surface of the first metal layer 22 including the first metal layer 22 made of Cu in which the peripheral end portion 18 is partially covered by the resist 20 and the side surface 33. The second metal layer 35 is made of Au.

  The planar shape of the first metal layer 22 (the shape projected onto the substrate 37) is a rectangle having long and short sides of 0.850 mm and 0.600 mm, respectively (see FIG. 11). On the other hand, the planar shape of the second metal layer 35 is a rectangle having a long side and a short side of 0.650 mm and 0.400 mm, respectively. The resist 20 extends 0.100 mm inside the left and right sides of the first metal layer 22. Further, the resist 20 extends 0.200 mm inside the upper side of the first metal layer 22.

  As will be described later, the resist 20 is formed by a spraying method or printing using a predetermined mask. The accuracy of these resist forming methods is about 0.050 mm. Therefore, the resist 20 is formed to extend from the outer periphery of the first metal layer 22 to the inside of 0.10 mm or 0.200 mm so that the peripheral end portion of the first metal layer 22 is surely covered with the resist 20. Has been.

  As shown in FIG. 11, the planar shape of the reinforced external terminal pad 26 is a quadrangle, and the peripheral end 18 of the first metal layer 22 along the three sides of the quadrangle is covered with a resist 20. As described above, since the peripheral edge (rectangular side) that is the starting point of the external terminal pad peeling is reinforced by the resist 20, the reinforced external terminal pad 26 is unlikely to cause the external terminal pad peeling.

  In the reinforced external terminal pad 26, the surface (exposed surface) of the first metal layer 22 that is not covered with the resist 20 is covered with the second metal layer 35 including the side surface 33. Therefore, even if a large force is applied to the solder layer fixed to the second metal layer 35, the second metal layer 35 is easily caught from the side surface 33 of the first metal layer 22, so that the second metal layer 35 can be easily removed from the first metal layer 22. Will not peel off. Therefore, in the reinforced external terminal pad 26, solder peeling hardly occurs.

  Therefore, according to the electronic component module 39 of the present embodiment, it is possible to suppress or prevent external terminal pad peeling and solder peeling due to impact such as dropping.

(2) Manufacturing Method Next, a manufacturing method of the electronic component module 39 will be described.

  First, after forming via holes, wirings 36 and the like in the base substrate 38, resin layers 40 and 41 are formed on both surfaces of the base substrate 38.

  Next, the resin layers 40 and 41 are irradiated with a laser beam to form vias (laser vias). A Cu layer is formed by electroless plating inside the laser via and on the surfaces of the resin layers 40 and 41.

  Next, after forming a predetermined etching mask on the surface, this Cu layer is etched to form a Cu layer (hereinafter referred to as a pad lower layer) that becomes the pad 5 on the surface (first main surface 3) of the resin layer 40. ) And the first metal layer 26 is formed on the surface of the resin layer 41 (second main surface 9).

  Next, an epoxy resin is sprayed (or printed) on the first main surface 3 and the second main surface 9 using a mask corresponding to the shape of the resist 20. At this time, a resist 20 that opens in the region where the pad 5 is formed is formed on the first main surface 3. On the other hand, the second main surface 9 is formed with a resist 20 that extends in a region along the three sides of the first metal layer 26.

  Next, an Au layer is formed on the surface of the lower layer of the pad formed on the first main surface 3 and the exposed surface of the first metal layer 22 formed on the second main surface 9 by electroless plating. Form. This Au layer is also formed on the side surface 33 of the first metal layer 22.

  The build-up substrate 37 is completed through the steps so far.

  Next, cream solder is applied to the surface of the pad 5 formed on the first main surface 3, and then the electronic component 4 is placed on the substrate 37 so that the terminals of the electronic component 4 are in contact with the predetermined pad 5. . Thereafter, the substrate 37 is heat-treated in a reflow furnace, and the electronic component 4 is fixed to the substrate 37 with solder 56.

  Finally, the shield case 48 is fixed around the first main surface 3 to complete the electronic component module 39.

(3) Mounting Method The electronic component module 39 of this embodiment is mounted on a mother board of a mobile communication device such as a mobile phone.

  FIG. 13 is a side view of the mother board 50 on which the electronic component module 39 is mounted. On the main surface of the mother board 50, wiring (not shown) having pads 52 at the ends is formed. The external component pads of the electronic component module 39 of this embodiment and the electronic component 54 are connected to the pads 52 by solder 56.

  Soldering is performed in the following procedure. First, cream solder is printed on the pad 52 on the mother board 50. Next, the electronic component module 39 and the like are placed so that the reinforced external terminal pads corresponding to the pads 52 are in contact with each other. Thereafter, the mother board 50 is heated in a reflow furnace, and the electronic component module 39 and the electronic component 54 are soldered to the mother board 50.

  As described above, the external terminal pads of the electronic component module 39 are reinforced by the resist 20 and the second metal layer 35 covers the side surfaces of the first metal layer 22, so that even if the device comprising the mother board 50 falls. External terminal pad peeling and solder peeling are difficult to occur.

(4) Strength Test Next, the result of the strength test performed on the electronic component module 39 will be described.

  14 and 15 are diagrams for explaining the strength test method.

  The strength test is performed by placing the mother board 50 on which the electronic component module 39 is mounted on the pillars 58 arranged at the four corners of a square having a side of 60 cm (see FIG. 14). At this time, the mother board 50 is placed upside down so that the surface on which the electronic component module 39 is mounted faces downward. Further, the position of the mother board 50 is adjusted so that the electronic component module 39 comes to substantially the center of the column 58.

  Next, the iron ball 60 is dropped toward the mother board 50 (see FIG. 14). When the iron ball 60 collides with the mother board 50, the mother board 50 is bent downward (see FIG. 15).

  When the mobile communication device or the like falls, a similar curve is generated on the mother board, which causes external terminal pad peeling or solder peeling.

  Therefore, the relationship between the distortion rate and the peeling occurrence rate that quantified the degree of curvature was examined. Here, the distortion rate D is defined by the following formula (1). The peeling occurrence rate is the ratio of external terminal pads that have caused either or both of external terminal pad peeling and solder peeling.

D = d / L (1)
Here, d is the depth at which the mother board 50 is recessed below the support 58 due to the collision with the iron ball 60. L is the distance between the columns 58.

  In the strength test, the relationship between the iron ball drop position (drop height) and the distortion rate is measured in advance, and the distortion rate is changed by changing the iron ball drop position (drop height). Measure the rate of exfoliation against the rate.

  A sample used for measurement (hereinafter referred to as a measurement sample) is the electronic component module 39 described above. A plurality of the electronic component modules 39 having 59 reinforced external terminal pads were prepared, and the above-described strength test was performed on each electronic component module. Strength measurement was performed on a plurality of strain rates while changing the drop position (drop height) of the iron ball, and the peel occurrence rate of a 6-piece measurement sample was measured for one strain rate.

  For comparison, a strength test was also performed on an electronic component module having a conventional external terminal pad. The structure of the electronic component module for comparison is the same as the electronic component module 39 of the present embodiment except for the structure of the external terminal pads.

  FIG. 16 is a plan view of the external terminal pad 8 formed on the comparative sample. 17 is a cross-sectional view taken along line AA in FIG. 16 as viewed from the direction of the arrow.

  The external terminal pad 8 of the comparative sample is made of Au formed on the exposed surface of the first metal layer 22 including the first metal layer 22 made of Cu surrounded by the resist 20 and the side surface 33. It is formed by the second metal layer 35 (see FIG. 17). Here, the distance between the resist 20 and the second metal layer 35 is 0.075 mm (see FIG. 16).

  The planar shape of the second metal layer 35 of the comparative sample is a rectangle with long sides and short sides of 0.650 mm and 0.400 mm, respectively (see FIG. 16). This shape is the same including the planar shape and dimensions of the second metal layer 35 of the measurement sample. That is, the shape and dimensions of the second metal layer 35 to which the solder adheres are the same for the measurement sample and the comparison sample.

  The number of samples measured is 5 pieces for each distortion rate.

  Table 1 lists the results of the strength test for the measurement sample. On the other hand, Table 2 lists the results of the strength test for the comparative sample.

  The first column of each table represents the distortion rate. The second column represents the number of pads measured. The third column and the fourth column represent the number of pads and the occurrence rate of peeling, respectively. Here, the peeling occurrence rate is the ratio of the number of pads peeled off (third row) to the number of pads tested (second row). The “number of pads with peeling” is the number of external terminal pads in which one or both of external terminal pad peeling and solder peeling have occurred.

  FIG. 18 is a diagram illustrating the relationship between the distortion rate and the peeling occurrence rate described in Tables 1 and 2. The horizontal axis is the distortion rate, and the vertical axis is the peeling occurrence rate. The solid line shown in FIG. 18 represents the result for the measurement sample. On the other hand, the broken line represents the result for the comparative sample.

  As shown in FIG. 18, when the distortion rate exceeds 0.6%, the occurrence rate of peeling with respect to the comparative sample increases rapidly (see broken line). On the other hand, the peeling rate (see solid line) for the measurement sample is only about 1/20 of the comparative sample. Note that the peeling rate of the comparative sample decreased at a distortion rate of 0.9%, which is considered to be due to a measurement error.

  The above results indicate that the electronic component module 39 of the present embodiment is less likely to cause external terminal pad peeling and solder peeling than the conventional electronic component module 8.

(1) Configuration FIG. 19 is a cross-sectional view of the electronic component module 62 of this embodiment.

  The electronic component module 62 of the present embodiment is different from the electronic component module 39 of the first embodiment in the configuration of the reinforced external terminal pads and the configuration of the substrate. Hereinafter, differences from the electronic component module according to the first embodiment will be described.

  The electronic component module 62 of the present embodiment is formed using a multilayer substrate 68 on which a plurality of copper clad laminates 64 and 65 (Copper Clad Laminate) are laminated via a resin layer 66 as a base. Furthermore, the multilayer substrate 68 of the present embodiment has a resin layer 70 formed on the back side.

  Wirings 36 or pads 5 are formed on both surfaces of the copper clad laminate 64. Further, the reinforced external terminal pads 72 of the present embodiment are formed on the surface of the resin layer 70, that is, the second main surface 9 which is the mother board side. That is, the multilayer board 68 is a printed board having five wiring layers.

  FIG. 20 is a plan view of the reinforced external terminal pad 72. As shown in FIG. 20, the planar structure of the reinforced external terminal pad 72 of this embodiment is basically the same as that of the reinforced external terminal pad 26 of the first embodiment. However, the dimensions of the first metal layer 22 and the second metal layer 35 are different from those of the first embodiment.

  The planar shape of the first metal layer 22 of the present embodiment is a rectangle having long sides and short sides of 1.050 mm and 0.975 mm, respectively (see FIG. 20). On the other hand, the planar shape of the second metal layer 35 is a square having a side of 0.900 mm. The resist 20 extends 0.075 mm inside the left and right sides of the first metal layer 22. The resist 20 also extends 0.075 mm inside the upper side of the first metal layer 22.

  The structure of the cross section taken along the line AA in FIG. 20 as viewed from the direction of the arrow is the same as the cross sectional structure described with reference to FIG. That is, the third metal layer 32 and the fourth metal layer 30 are formed below the first metal layer 22 and the second metal layer 35. The third metal layer 32 extends on the inner wall of the through hole 28 that penetrates the multilayer substrate 68.

  As shown in FIG. 3, the opening of the through hole 28 opened on the second main surface 9 of the substrate 68 is closed by the first metal layer 22, and the inside thereof is filled with the epoxy resin 34. .

  The planar shape of the multilayer substrate 68 is a rectangle having a long side and a short side of 9.2 mm and 7.1 mm, respectively, and is a quadrangle having substantially the same size as the build-up substrate 37 of the first embodiment.

  On the other hand, the thickness of the multilayer board 68 of the present embodiment is 1.31 mm, which is much thicker than the build-up board (0.37 mm) of the first embodiment.

  When the substrate becomes thick, the electronic component module is less likely to be deformed by an external force. Therefore, when the substrate becomes thicker, a greater force acts on the external terminal pads even if the distortion rate of the mother board deformed by the impact is the same. For this reason, external terminal pad peeling cannot be sufficiently suppressed with an external terminal pad in which the peripheral end is simply reinforced with a resist as in the first embodiment.

  Therefore, in this embodiment, a through hole 28 penetrating the substrate is formed below the external terminal pad, and the third metal layer 32 extends on the inner wall of the through hole 28 to reinforce the external terminal pad. ing.

  As shown in FIG. 12, the first metal layer 22 of Example 1 also includes a metal 46 extending into the laser via hole. However, since the laser via hole is much shallower than the through hole, the effect of reinforcing the external terminal pad is limited.

  By the way, the electronic component module 62 of the present embodiment is used by being mounted on a motherboard in the same manner as the electronic component module 39 of the first embodiment. Therefore, the description of the mounting method of the electronic component module 62 is omitted so as not to duplicate the description (the same applies to Example 3 below).

(2) Manufacturing Method Next, a manufacturing method of the electronic component module 62 of this embodiment will be described.

  First, the copper-clad laminates 64 and 65 on which the wirings 36 are formed are bonded via the first resin layer 66, and further the second resin layer 70 is formed on the surface on the mother board side. However, wiring (including pads) is not formed on the surface of the copper-clad laminate 64 serving as the first main surface 3, and the entire surface is left as a Cu layer.

  Next, copper (Cu) is plated (electroless plating) on the surface of the second resin layer 70. The Cu layer plated at this time becomes the fourth metal layer 30 later.

  The second resin layer 70 is for forming a fifth wiring layer. Therefore, when there are four wiring layers, it is not necessary to form the second resin layer 70. In that case, the surface of the copper-clad laminate 65 on the motherboard side is left as a single Cu layer.

  Next, a through hole is formed by drilling a through hole at the center of the position where the reinforced external terminal pad 72 is to be formed.

  Next, Cu is plated (electroless plating) on the Cu layer covering the inner wall of the through hole and the first main surface 3 and the second main surface 9. At this time, the Cu layer plated on the second main surface 9 later becomes the third metal layer 32.

  Next, an epoxy resin 34 is filled into the through hole 28 whose inner wall is plated with Cu.

  Next, the substrate 68 being processed is plated again (electroless plating), and a Cu layer is laminated on the first main surface 3 and the second main surface 9. At this time, the Cu layer formed on the second main surface 9 extends on the through hole 28 and becomes the first metal layer 22.

  Next, the Cu laminated film formed on the first main surface 3 and the second main surface 9 is etched into a predetermined shape. By this etching, a wiring including the pad 5 is formed on the first main surface 3, and a rectangular Cu laminated film serving as the reinforced external terminal pad 72 is formed on the second main surface 9.

  Next, a resist 20 is formed on the first main surface 3 and the second main surface 9 by a spraying method or printing using a predetermined mask. At this time, the region 18 along the three sides of the first metal layer 22 is covered with the resist 20 (see FIGS. 3 and 20).

  Next, an Au layer is formed by electroless plating on the surface of the pad 5 formed on the first main surface 3 and the exposed surface (including the side surface 33) of the first metal layer 22 not covered with the resist 20. . At this time, the Au layer formed on the first metal layer 22 becomes the second metal layer 35.

  The multilayer substrate 68 is completed through the steps so far.

  Next, cream solder is applied to the surface of the pad 5, and the electronic component is placed on the substrate 68 so that the terminals of the electronic component 4 are in contact with the predetermined pad 5. Thereafter, the substrate 68 is heat-treated in a reflow furnace, and the electronic component 4 is soldered to the substrate 68.

  Finally, the shield case 48 is fixed around the first main surface 3 to complete the electronic component module 62.

(3) Strength Test Next, the result of the strength test performed on the electronic component module 62 will be described.

  The strength test method is the same as the strength test method described in Example 1.

  On the back surface of the test electronic component module 62, 24 reinforced external terminal pads 72 are provided along the outer periphery. The configuration of the multilayer substrate 68 and the shape / dimensions of the reinforced external terminal pads 72 are as described with reference to FIGS. 3, 19, and 20. In addition, the strength measurement was performed on 6 pieces of the sample every time the position where the iron ball dropped was changed.

  FIG. 21 is a plan view of the external terminal pad 8 provided on the comparative sample. FIG. 22 is a view of the cross section taken along the line AA of FIG. 21 as viewed from the direction of the arrow.

  The external terminal pad 8 provided in the comparative sample is made of Au formed on the exposed surface of the first metal layer 22 including the first metal layer 22 made of Cu and the side surface 33 surrounded by the resist 20. The second metal layer 35 is formed. Here, the distance between the resist 20 and the first metal layer 22 is 0.075 mm.

  The planar shape of the second metal layer 35 is a rectangle with long sides and short sides of 1.050 mm and 0.900 mm, respectively (see FIG. 21). This shape, including the dimensions, is the same as the planar shape of the second metal layer 35 that forms the measurement sample. That is, the shape and dimensions of the second metal layer 35, which is the metal layer to which the solder adheres, are the same for the measurement sample and the comparison sample.

  The structure of the electronic component module for comparison is the same as the structure of the measurement sample except for the structure of the external terminal pad. The number of samples measured is 6 pieces for each distortion rate.

  The results of the strength test on the measurement sample are listed in Table 3. On the other hand, Table 4 lists the results of the strength test for the comparative sample.

  The items described in Tables 3 and 4 are the same as those in Tables 1 and 2.

  FIG. 23 is a diagram for explaining the relationship between the distortion rate and the peeling occurrence rate described in Tables 3 and 4. The horizontal axis is the distortion rate, and the vertical axis is the peeling occurrence rate. The solid line shown in the figure represents the result for the measurement sample. On the other hand, the broken line represents the result for the comparative sample.

  As shown in FIG. 23, when the distortion rate is 0.6% or more, the peeling rate with respect to the comparative sample increases rapidly (see the broken line). On the other hand, the peeling occurrence rate of the measurement sample is suppressed to about 1/9 to 1/5 of the comparative sample (however, the peeling occurrence rate is 2 to 3 times higher than that of Example 1. ing.).

  The above results show that the reinforced external terminal pad 72 of the present embodiment hardly causes a peeling phenomenon such as peeling of the external terminal pad with respect to the impact at the time of dropping.

  In the electronic component modules according to the first and second embodiments, the land (pad) provided on the back surface (second main surface 9) of the substrate is soldered to the land provided on the motherboard. ) Type electronic component module.

  When such an LGA type electronic component module is mounted on a motherboard, first, cream solder is printed on a land provided on the motherboard, the land of the electronic component module is brought into contact therewith, and then soldered by a reflow furnace. To do.

  On the other hand, the electronic component module of the present embodiment has a BGA (Ball Grid Array) in which ball-shaped solder (solder balls) is fixed in advance to a circular pad formed on the back surface (second main surface 9) of the substrate. ) Type electronic component module.

  The configuration of the electronic component module of the present embodiment is substantially the same as the electronic component module of the first embodiment except for the configuration of the reinforced external terminal pad. Therefore, the description regarding the part common to both electronic component modules is abbreviate | omitted.

  FIG. 24 is a perspective view of the electronic component module 73 of this embodiment as viewed from the back side. As shown in FIG. 24, the reinforced external terminal pads 78 to which the solder balls 74 are fixed are arranged along the outer periphery of the substrate 76.

  Here, the substrate 76 may be a build-up substrate as in the first embodiment, or may be a multilayer wiring substrate as in the second embodiment. Further, the reinforced external terminal pads 78 may be arranged in a two-dimensional array not only on the outer periphery of the substrate 76 but also on the entire back surface (second main surface 9) of the substrate 76, for example.

  FIG. 25 is an enlarged plan view of a region surrounded by a broken line in FIG. However, the solder balls 74 are omitted so that the configuration of the reinforced external terminal pads 78 is clear. FIG. 26 is a cross-sectional view taken along the line AA in FIG. 25 as seen from the direction of the arrow. FIG. 27 is a view of a cross section taken along line BB in FIG. 25 as seen from the direction of the arrow.

  As shown in FIG. 25, the shape of the reinforced external terminal pad 78 of this embodiment is a circle. Then, the peripheral end portion 18 of the first metal layer 22 made of Cu along the first and second strings 80 and 82 facing each other of the circle is covered with the resist 20 (FIGS. 25 and 25). 26).

  The exposed surface 33 including the side surface of the first metal layer 22 is covered with a second metal layer 35 made of Au (see FIGS. 25 and 27). Further, solder balls (not shown) are fixed to the second metal layer 35.

  When the electronic component module 73 is soldered to the motherboard, the electronic component module 73 is placed on the motherboard so that the solder balls are in contact with pads formed on the main surface of the motherboard, and then soldered using a reflow furnace. I do.

  FIG. 28 is a plan view of external terminal pads provided in a BGA type conventional electronic component module. As shown in FIG. 28, the conventional external terminal pad 8 and the resist 20 are separated. On the other hand, since the peripheral end portion 18 of the reinforced external terminal pad 78 of this embodiment is covered with the resist 20, the external terminal pad is hardly peeled off. Further, since the second metal layer 35 covers the side surface of the first metal layer 22 at a part of the peripheral end portion, solder peeling hardly occurs.

  The manufacturing method of the electronic component module of the present embodiment is substantially the same as the manufacturing method of the electronic component module of the first or second embodiment. However, after the formation of the second metal layer 35, a process of placing the solder ball on the external terminal pad and fixing the solder ball to the external terminal pad by heat treatment is added.

  29 and 30 show reinforced external terminal pads having shapes different from those in FIG.

  In the example shown in FIG. 29, in addition to the first string 80 and the second string 82, the peripheral end portion of the first metal layer 22 along the opposing third string 84 and fourth string 86 is the resist 20. And the peripheral ends along the first to fourth strings are separated from each other.

  In this way, the second metal layer 35 is evenly hooked on the side surface 33 of the first metal layer 22, so that the solder peeling is less likely to occur.

  Alternatively, as shown in FIG. 30, the opening of the resist 20 may be an ellipse, and may cover the peripheral end portion along the two opposing strings of the first metal layer 22.

  The substrate 76 described in this embodiment is the same buildup substrate as that in the first embodiment. However, the substrate 76 may be the same multilayer substrate as in the second embodiment. In this case, the reinforced external terminal pad is also reinforced by the through hole, so that the peeling phenomenon is less likely to occur.

  In the above example, the first, third, and fourth metal layers are made of Cu. However, these metal layers may be formed of other metals (for example, Ag) or the like. The second metal layer may also be formed of a metal other than Au (for example, Pt).

It is a side view of the electronic component module of an embodiment It is the top view to which the area | region A enclosed with the broken line in FIG. 1 was expanded. It is sectional drawing which looked at the cross section in the AA line of FIG. 2 from the direction of the arrow. It is a top view of the external terminal pad which this inventor provided in the electronic component module before this invention. It is the figure which looked at the cross section in the AA of FIG. 4 from the direction of the arrow. FIG. 6 is a plan view of a reinforced external terminal pad in which one side of a square is covered with a resist. It is a top view of the reinforcement | strengthening external terminal pad with which 2 sides which a square opposes were covered with the resist. It is a top view of the reinforcement | strengthening external terminal pad with which two adjacent sides of the rectangle were covered with the resist. 1 is a cross-sectional view of an electronic component module of Example 1. FIG. It is the perspective view which looked at the electronic component module of Example 1 from the 2nd main surface side in which the reinforcement | strengthening external terminal pad was formed. It is the top view to which the area | region A covered with the broken line in FIG. 10 was expanded. It is the figure which looked at the cross section in the AA of FIG. 11 from the direction of the arrow. It is a side view of the mother board in the state where the electronic component module of Example 1 was mounted. It is a figure explaining the method of the strength test with respect to an electronic component module (the 1). It is a figure explaining the method of the strength test with respect to an electronic component module (the 2). 3 is a plan view of an external terminal pad of a comparative sample of Example 1. FIG. It is the figure which looked at the cross section in the AA of FIG. 16 from the direction of the arrow. (Example 1) which is a figure explaining the relationship between a distortion rate and peeling incidence. It is sectional drawing of the electronic component module of Example 2. FIG. 6 is a plan view of a reinforced external terminal pad of Example 2. FIG. 3 is a plan view of an external terminal pad of a comparative sample of Example 1. FIG. It is the figure which looked at the cross section in the AA of FIG. 22 from the direction of the arrow. (Example 2) which is a figure explaining the relationship between a distortion rate and peeling incidence. It is the perspective view which looked at the electronic component module of Example 3 from the back side. It is the top view to which the area | region A enclosed with the broken line in FIG. 24 was expanded. It is the figure which looked at the cross section along the AA line of FIG. 25 from the direction of the arrow. It is the figure which looked at the cross section along the BB line of FIG. 25 from the direction of the arrow. It is a top view of the external terminal pad of the conventional electronic component module of a BGA type. It is a top view of the other reinforcement | strengthening external terminal pad of Example 3 (the 1). It is a top view of the other reinforcement | strengthening external terminal pad of Example 3 (the 2).

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 ... Electronic component module 3 ... 1st main surface 4 ... Electronic component 5 ... Pad 6 ... Electronic circuit apparatus 8 ... External terminal pad 9 ... 2nd main surface DESCRIPTION OF SYMBOLS 10 ... Board | substrate 12 ... Upper side 14 ... Left side 16 ... Right side 18 ... Peripheral edge part 20 (resistor terminal pad) ... Resist 22 ... 1st metal layer 24 ... External terminal pad (related technology) 26: Reinforced external terminal pad 28: Through hole 30 ... Fourth metal layer 32 ... Third metal layer 33 ... Side surface 34 ... Epoxy Resin 35... Second metal layer 36... Wiring 37... Substrate 38... Base substrate 39... (Embodiment 1) electronic component modules 40, 41. · Resin layer 42 ··· Metal layer 44 (plated on the inner wall of the via hole) · · · Epoxy resin 46 · ·・ Metal 48 (filled in laser via) ... Shield case 50 ... Motherboard 52 ... (Motherboard) pad 54 ... Electronic component 56 ... Solder 58 ... Post 60 ... Iron Sphere 62 ... (Embodiment 2) electronic component modules 64, 65 ... copper clad laminate 66 ... first resin layer 68 ... multilayer substrate 70 ... second resin layer 72 .... (Exemplary example 2) Strengthened external terminal pads 73 (Embodiment 3) electronic component module 74 ... Solder ball 76 ... (Embodiment 3) board 78 ... (Embodiment 3) Strengthening external terminal pad 80 ... 1st string 82 ... 2nd string 84 ... 3rd string 86 ... 4th string

Claims (13)

Electronic components,
The electronic component is mounted on the first main surface, and a plurality of external terminal pads to which the electronic circuit device composed of the electronic component is electrically connected are formed on the second main surface,
The first metal layer including a first metal layer in which a part or all of the plurality of external terminal pads is partially covered with a resist that protects the second main surface, and a side surface A reinforced external terminal pad made of a second metal layer formed on the exposed surface of
A featured electronic component module. The second metal layer is a metal layer bonded to a pad formed on another substrate by solder;
The electronic component module according to claim 1, wherein The reinforced external terminal pads are disposed at the four corners of the substrate,
The electronic component module according to claim 1, wherein the electronic component module is characterized in that: The reinforced external terminal pads are disposed along the outer periphery of the substrate;
The electronic component module according to any one of claims 1 to 3, wherein the electronic component module is characterized in that: An opening that penetrates through the substrate and is open on the second main surface has a through hole that is blocked by the first metal layer;
The reinforced external terminal pad has a third metal layer formed between the first metal layer and the substrate and extending to the inner wall of the through hole.
The electronic component module according to claim 1, wherein the electronic component module is characterized in that: The shape of the reinforced external terminal pad is a square,
The electronic component module according to claim 1, wherein the electronic component module is any one of claims 1 to 5. The peripheral edge of the first metal layer along a part of the side of the quadrangle is covered with the resist.
The electronic component module according to claim 6. That the sides are two opposite sides of the square,
8. The electronic component module according to claim 7, wherein That the sides are two adjacent sides of the square,
8. The electronic component module according to claim 7, wherein That the sides are the three sides of the square;
8. The electronic component module according to claim 7, wherein The shape of the reinforced external terminal pad is a circle,
The electronic component module according to claim 1, wherein the electronic component module is any one of claims 1 to 5. The peripheral edge of the first metal layer along the opposing first and second strings of the circle is covered with the resist.
The electronic component module according to claim 11, wherein The peripheral end portions of the first metal layer along the third and fourth strings facing each other of the circle are covered with the resist, and the peripheral end portions along the first to fourth strings are separated. What you are doing
The electronic component module according to claim 12, characterized in that:

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