JP2009032865A - Electronic device, and method for manufacturing electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic device and a mounting method thereof, capable of preventing a drop of components mounted on the surface reflowed in advance at the time of mounting the surface-mount component on the both sides of a substrate by reflow. <P>SOLUTION: The mounting method includes the steps of: soldering some terminals of the surface-mount components (3, 7) on an A surface of the substrate (1) by reflow; coating a conductive adhesive agent (6) to the terminals without being soldered by reflow; reversing the substrate; and hardening the conductive adhesive agent (6) coated on the A surface of the substrate by using a preliminary heating temperature of the temperature profile of reflow before the solder (5) is melted at the time of soldering all terminals of the surface-mount components (3, 7) on a B surface of the substrate (1) by reflow. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electronic device and a method for manufacturing the same, and more particularly to an electronic device including a surface-mounted component mounted on both surfaces of a substrate using solder reflow and a method for mounting the same.

  In recent years, electronic devices have been miniaturized, and the board incorporated in the electronic equipment has been designed to increase the density and miniaturization of the mounted components. As one way to achieve these, components have been mounted on both sides of the substrate. It was.

As a method for mounting components on both sides of the substrate, there are the following methods. First, solder is supplied to the land on one substrate surface A by printing or the like, and a surface-mounted component is mounted on the upper surface. Then, the solder is melted by a reflow furnace using infrared rays or hot air to connect the land of the substrate and the terminal of the component. (First reflow process) Next, the substrate is turned over, solder is supplied to the lands on the other substrate surface B by printing or the like, and a surface-mounted component is mounted on the upper surface. Then, the solder is melted by a reflow furnace to connect the land of the substrate and the terminal of the component. (Second reflow process)
However, in such a process, the substrate surface A is in the downward direction during the second reflow process, and the solder is remelted in a state where the previously mounted component is in the downward direction. Larger components sometimes fall off the board. Naturally, this drop is more likely to be established with heavy mounted components.

  Therefore, the following methods are known as methods for solving the above problems. That is, in Japanese Patent Application Laid-Open No. 8-78837 (Patent Document 1), a hole is provided in a substrate corresponding to the bottom surface of a surface-mounted component mounted on the substrate surface B, the component is mounted on the substrate surface B, and the substrate is reflowed. , And apply the thermosetting adhesive in an amount sufficient to adhere the side wall of the hole and the bottom of the mounted component to the hole described above, mount the component on it, and the temperature curve for reflow heating in the reflow process A method is described in which properties are used to bond and fix a component and a substrate with a thermosetting adhesive before reaching the melting temperature of the solder.

  In JP-A-6-85452 (Patent Document 2), after soldering a substrate and a surface mount component (QFP), a thermosetting adhesive is applied across the surface mount component and the substrate. A method for preventing the parts from falling is described.

  Japanese Patent Laid-Open No. 4-245495 (Patent Document 3) uses a solder having a high melting point that is used for a substrate surface on which a component is first mounted, and uses a solder having a low melting point that is used later on a substrate surface on which the component is mounted. The method of preventing the fall of components by not melting the previously soldered solder is described.

  Furthermore, Japanese Patent Laid-Open No. 2005-166903 (Patent Document 4) provides a dummy lead that does not have a circuit function on a surface-mounted component, and the dummy lead and a substrate are bonded and fixed with a heat-resistant adhesive. A method for preventing the parts from falling is described.

JP-A-8-78837 JP-A-6-85452 JP-A-4-245495 JP 2005-166903 A

  However, in the method of Patent Document 1, since a hole is formed in the substrate, the wiring layout of the substrate is restricted, which is not suitable for high-density mounting, and the mold resin of the mounting component contains a release agent. The back of the component does not fit well with the adhesive, and the component may fall during reflow.

  Further, in the method of Patent Document 2, the familiarity between the mold resin and the adhesive is poor due to the release agent contained in the mold resin, and the part may fall during reflow.

  Further, in the method of Patent Document 3, since two types of solder are used, two types of temperature profiles for reflow are required, and the setting is switched, so that the process becomes complicated.

  Furthermore, in the method of Patent Document 4, a dummy lead having no circuit function is necessary, and it is difficult to apply this technique to a commercially available surface mount component.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems of the prior art and provide an electronic device having a mounting structure that prevents a component from dropping when a surface-mounted component is mounted on both surfaces of a substrate by reflow, and a method for manufacturing the same. There is.

  In order to achieve the above object, according to the present invention, in an electronic device in which surface-mounted components are mounted on both surfaces of a substrate, a plurality of lands provided on the substrate on at least one surface of both surfaces of the substrate, In combination with a plurality of terminals of a surface mount component, the combination includes a combination that is electrically connected and fixed using solder and a combination that is electrically connected and fixed using a conductive adhesive .

  According to the present invention, in the electronic device, there are a plurality of combinations of the land and the terminal that are connected and fixed using the conductive adhesive.

  In the electronic device, the plurality of sets that are electrically connected and fixed using the conductive adhesive are arranged at at least one diagonal position of the surface mount component. It includes two combinations of a land and the terminal.

  In the electronic device, the plurality of sets to be electrically connected and fixed using the conductive adhesive may include the land and the terminal located at least at an end portion of the surface mount component. These two combinations are included.

  According to the present invention, in the electronic device, the land for connecting and fixing the terminal using the solder is different from the land for connecting and fixing the terminal using the conductive adhesive. It is characterized by being.

  In the electronic device, the surface area of the land for connecting and fixing the terminal using the solder is the surface area of the land for connecting and fixing the terminal using the conductive adhesive. It is characterized by being smaller than.

  In the electronic device, a ground layer is built in an inner layer of the substrate, a ground terminal of the surface mount component is connected to the ground layer by wiring, and a common signal terminal of the surface mount component is It is connected by other wiring.

  The present invention is also directed to an electronic device having surface-mounted components mounted on both sides of a substrate, wherein one surface A of the substrate is a combination of a plurality of lands provided on the substrate and a plurality of terminals of the surface-mounted component. And the other surface B of the substrate is provided on the substrate. The combination of the substrate is electrically connected and fixed using a solder, and the combination is electrically connected and fixed using a conductive adhesive. In the combination of the plurality of lands formed and the plurality of terminals of the surface mount component, they are electrically connected and fixed using solder.

  According to the present invention, in the manufacturing method in which the surface mounting components are mounted on both surfaces of the substrate by reflow, a first terminal of the surface mounting components is soldered to the one surface A of the substrate by reflow. A second step of applying a conductive adhesive to a terminal of a surface-mounted component that has not been soldered to one surface A of the substrate by reflowing in the first step, and the other step of the substrate A third step of soldering the terminals of the surface-mounted component to the surface B by reflow, and in the third step, the terminals of the surface-mounted component are connected to the other surface B of the substrate. When soldering by reflow, before the solder is melted by using the preheating temperature of the reflow temperature profile, the conductive adhesive applied to the one surface A is cured by the second step. Characterized in that for electrically connecting.

Further, the present invention provides a method for mounting surface-mounted components on both surfaces of a substrate by reflow, supplying solder to one surface A of the substrate excluding some terminals of the surface-mounted components, and remaining terminals A fourth step of applying a conductive adhesive to the surface and soldering by reflow, and a fifth step of soldering the terminals of the surface-mounted component to the other surface B of the substrate by reflow,
In the fourth step, when soldering the terminal of the surface-mounted component to one surface A of the substrate by reflow, before the solder is melted using the preheating temperature of the reflow temperature profile, The conductive adhesive applied to the one surface A in the fourth step is cured and electrically connected.

  According to the present invention, when a surface mount component is mounted on both sides of a substrate, a terminal (for example, a lead or an electrode) of the surface mount component is used by using a combination of solder and a conductive adhesive. ) Is electrically connected, and is bonded and fixed, so that it is possible to effectively prevent the surface-mounted component mounted on the lower surface side of the board from dropping at the time of the second reflow of the solder.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a perspective view showing an external appearance of an A surface of a substrate of Example 1 of an electronic device constituted by mounting a semiconductor device (surface mount component) on both surfaces of a substrate according to the present invention. In FIG. 1, 1 is a substrate, 2a and 2b are a plurality of lands disposed on the substrate, and 3 is a semiconductor device (surface mount component) incorporating semiconductor elements (not shown) mounted on both sides of the substrate 1. 4 is a plurality of leads (terminals) formed on each semiconductor device 3 mounted on both sides of the substrate 1, and 5 is a combination of a plurality of lands 2 b and a plurality of leads 4 formed on both sides of the substrate 1. Each of the solders 6 for connection is a conductive adhesive for connecting a combination of a plurality of lands 2 a and a plurality of leads (terminals) 4 formed on the A surface of the substrate 1. As shown in FIGS. 1 and 2, for example, two sets of lands 2a and leads (terminals) 4 arranged (provided) at least at one diagonal position of a semiconductor device (surface mount component) 3 are respectively provided. The other land 2b and the lead (terminal) 4 are connected and fixed using solder, respectively, using the conductive adhesive 6. That is, on the surface A side of the substrate 1, a plurality of sets of lands 2a and leads (terminals) 4 are connected and fixed using a conductive adhesive 6, and the other lands 2b and leads (terminals) 4 are fixed. Are connected and fixed using solder. On the other hand, on the B surface side of the substrate 1, all the lands 2b and the leads (terminals) 4 are connected and fixed using solder.

  FIG. 2 is a plan view showing the A surface of the substrate according to the first embodiment of the present invention. In FIG. 2, an AA line showing the position of a cross section for explaining the process of the embodiment 1 described in FIG. 3 is described. This position is a position passing through the center between the lead (terminal) 4 connected by the solder 5 and the lead 4 connected by the conductive adhesive 6 located at the end of the semiconductor device (surface mount component) 3. It is.

  FIG. 3 is a cross-sectional view showing a process of the mounting method (manufacturing method) of the first embodiment of the present invention. In the sectional view, inner leads, gold wires, and semiconductor elements in the semiconductor device 3 are omitted. In FIG. 3A, the solder 5 is printed on the land 2 b arranged on the A surface of the substrate 1. In FIG. 3B, the semiconductor device (surface mount component) 3 is mounted on the A surface of the substrate 1. In FIG. 3C, the solder 5 is melted by the reflow furnace, and the land 2b on the A surface of the substrate 1 and the lead 4 of the semiconductor device 3 mounted on the A surface of the substrate 1 are electrically connected and bonded. Fixed. In FIG. 3D, the conductive adhesive 6 is applied on, for example, two sets of lands 2 a that are not connected to the leads 4. As a method of applying, since a part is already mounted on the A surface of the substrate 1 and a printing method is difficult, a method using a dispenser is generally used. In FIG. 3E, first, the substrate 1 is turned upside down. And the solder 5 is printed on the land 2b arrange | positioned at the B surface of the board | substrate 1, and the semiconductor device 3 is mounted on it. In FIG. 3F, the conductive adhesive 6 applied to the A surface of the substrate 1 in the preheating process of the temperature profile of the reflow furnace is cured and mounted on the land 2a on the A surface of the substrate 1 and the A surface of the substrate 1. The lead 4 of the semiconductor device 3 is electrically connected to be bonded and fixed. Then, the solder 5 printed on the B surface of the substrate 1 in the main heating step of the temperature profile of the reflow furnace is melted, and the lands 2b and the leads 4 are electrically connected and bonded and fixed.

  FIG. 4 shows an image diagram of the temperature profile of the substrate placed in the reflow furnace. The horizontal axis represents the elapsed time since the substrate 1 on which the surface mount component 3 was mounted was put into the reflow furnace, and the vertical axis represents the substrate temperature. The symbols described in FIG. 4 are T0 representing the melting point of the solder, preheating temperature T1, maximum temperature T2 during main heating, preheating step time S1, and main heating step time S2. The conductive adhesive 6 is cured at a temperature of T1 for a time of S1. Even when the temperature becomes T0 or higher and the solder starts to remelt, the surface-mounted component can be prevented from falling from the substrate 1 because it is fixed to the substrate with the conductive adhesive.

  By configuring and mounting as described above, the solder 5 on the A surface on the lower surface of the substrate is also melted at the same time by the second reflow, but the lead 4 and the land 2a of the semiconductor device 3 are bonded by the conductive adhesive 6. Since it is fixed, it is possible to effectively prevent parts from falling.

  FIG. 10 is a cross-sectional view illustrating a cross-sectional structure of the first embodiment. A ground layer 9 is built in the inner layer of the substrate 1, and a semiconductor device (surface mount component) 3 is mounted on both surfaces of the substrate 1. The ground terminal of the semiconductor device 3 is connected to the ground layer 9 by the wiring 10a through the land, and the common signal terminal is connected by the wiring 10b through the land.

  With the above structure, the wiring can be shortened and the noise can be reduced. Further, since the degree of freedom of wiring is increased, there is an effect that the wiring layout becomes easy.

  Here, points to be considered when determining the location where the conductive adhesive is used and the connection area will be described. FIG. 11 is a cross-sectional view showing a configuration for conducting strength evaluation (shear test) of a conductive adhesive. A Cu block 11 simulating a chip component (surface mounted component) is connected to the land 2a of the substrate 1 via a conductive adhesive 6, and the Cu block 11 is pushed by moving the tool 12 in the direction of the arrow. The shear strength at the time of destruction was measured.

FIG. 12 shows the result of the shear strength measured in FIG. The evaluated conductive adhesive is sold as a substitute for solder. Resin A is H9626 manufactured by NAMICS, and resin B is CE-3920 manufactured by Emerson & Cumming. From this result, it was found that the shear strength was 1 kgf / mm ² or more. What is necessary is just to determine the location and connection area which use a conductive adhesive using this value.

  However, it goes without saying that when the rigidity of the leads 4 of the semiconductor device 3 is small, it is necessary to fix two or more leads at opposite positions using a conductive adhesive. Needless to say, when a new conductive adhesive is employed, it is necessary to perform a similar test and measure a reference value.

  The adhesive as the main component of the conductive adhesive used in the embodiment described above is based on the premise that it does not melt during secondary reflow, and a thermoplastic resin or a thermosetting resin whose resoftening temperature is higher than the reflow temperature. Needless to say, it is used. In addition, since the conductive adhesive is applied by a dispenser or the like, the process time can be shortened when there are few places to apply. Therefore, it goes without saying that the number of terminals (number of electrodes) connected by solder is equal to or more than the number of terminals (number of electrodes) connected using a conductive adhesive.

  Therefore, in Example 1, there are two places connected by the conductive adhesive 6, but it may be more than that. However, as described above, since the conductive adhesive is applied by a dispenser or the like, the process time can be shortened when the number of places to be applied is small. For this reason, since it is better that the number of portions to be applied is smaller, it is not necessary to use this structure for a semiconductor device that is not likely to fall, and it is important to minimize the semiconductor device that prevents dropping. Although the description has been given with respect to the 8-pin SOP, it is needless to say that the present invention can be applied to a multi-pin SOP and a semiconductor device such as SOJ or QFP having different shapes.

  FIG. 5 is a perspective view showing the external appearance of the A surface of the substrate of Example 2 of the electronic device configured by mounting chip components (surface mounted components) on both surfaces of the substrate according to the present invention. The substrate 1 is provided with lands 2a and 2b. The land 2a is connected to the conductive adhesive 6 and the land 2b is connected to the electrodes (terminals) 8 of the chip component (surface mounted component) 7 via the solder 5. Electrically connected.

  FIG. 6 is a plan view showing the A surface of the substrate according to the second embodiment of the present invention. In the drawing, a BB line representing the position of the cross section for explaining the process of the embodiment 2 described in FIG. 7 is described. This position is a position passing through the center of one electrode (terminal) 8 connected by the solder 5 and the center of the other electrode (terminal) 8 connected by the conductive adhesive 6.

  FIG. 7 is a cross-sectional view showing a process of the mounting method (manufacturing method) of the second embodiment of the present invention. In FIG. 7A, the solder 5 is printed on the land 2b arranged on the A surface of the substrate 1, and the conductive adhesive 6 is applied on the land 2a. In FIG. 7B, a chip component (surface mounted component) 7 is mounted on the A surface of the substrate 1. In FIG. 7C, the conductive adhesive 6 applied to the A surface of the substrate 1 in the preheating step of the temperature profile of the reflow furnace is cured, and the land 2 a and the electrode (terminal) 8 are bonded by the conductive adhesive 6. It is electrically connected and bonded and fixed. Then, the solder 5 printed on the A surface of the substrate 1 in the main heating process of the temperature profile of the reflow furnace is melted, and the land 2b and the electrode (terminal) 8 are electrically connected and bonded and fixed by the solder 5. The In FIG. 7D, the substrate 1 is first turned upside down. And the solder 5 is printed on the land 2b arrange | positioned at the B surface of the board | substrate 1, and the chip component 7 is mounted on it. In FIG. 7 (e), the solder 5 printed on the B surface of the substrate 1 in the main heating step of the temperature profile of the reflow furnace is melted, and the land 2 b and the electrode (terminal) 8 are electrically connected by the solder 5. Glued and fixed.

  By configuring and mounting as described above, the solder 5 on the A side of the lower surface of the substrate is also melted at the same time by the second reflow, but the electrode (terminal) 8 of the chip component 7 and the land 2a are electrically conductive adhesive. Since it is bonded and fixed by 6, it is possible to effectively prevent parts from falling.

  Although the second embodiment has been described with a chip component having two electrodes, it is an effective method for a surface mount component having a small number of terminals such as leads and electrodes, and a semiconductor device, electrolytic capacitor, and coil having a small number of terminals (number of leads). Needless to say, it can also be applied. Other configurations and effects are the same as those of the first embodiment, and thus description thereof is omitted.

  FIG. 8 is a perspective view showing the external appearance of the A surface of the substrate of Example 3 of the electronic device configured by mounting the semiconductor device (surface mount component) on both surfaces of the substrate according to the present invention. The feature of the third embodiment is that the land of the substrate to which the solder is connected and the land of the substrate to which the conductive adhesive is connected are formed in different shapes. In the configuration of FIG. 8, the land 2 a to which the conductive adhesive 6 is applied has, for example, a shape having a larger surface area than the land 2 b on which the solder 5 is printed.

  With such a structure, there is an effect that the application of the conductive adhesive 6 becomes easy. Moreover, since the application amount of the conductive adhesive 6 can be increased, the number of places where the conductive adhesive is applied can be reduced even in a heavy part, and the application time can be shortened. Other configurations and effects are the same as those of the first embodiment, and thus description thereof is omitted.

  FIG. 9 is a perspective view showing the external appearance of the A surface of the substrate of Example 4 of the electronic device configured by mounting the semiconductor device (surface mount component) on both surfaces of the substrate according to the present invention. The feature of the fourth embodiment is that the lead (terminal) 4 provided at the end (corner) of the semiconductor device 3 is electrically connected and fixed to the land 2 a by the conductive adhesive 6. is there. That is, of the leads (terminals) 4 provided in the semiconductor device 3, four of the outermost ends (corners) are electrically connected by the conductive adhesive 6 and fixed to the land 2a. The other leads 4 are electrically connected and fixed to the land 2b by the solder 5.

  By adopting such a structure, the maximum stress is generated at the outermost end (corner) connection portion when temperature cycle reliability is considered. By using a conductive adhesive having a smaller Young's modulus (softer) than solder in such places, stress can be relieved and the connection life can be extended. Other configurations and effects are the same as those of the first embodiment, and thus description thereof is omitted.

It is a perspective view which shows the external appearance in the board | substrate A surface of Example 1 of the electronic device which concerns on this invention. It is a top view in the board | substrate A surface of Example 1 of the electronic device which concerns on this invention shown in FIG. It is sectional drawing showing the process of the mounting method (manufacturing method) of Example 1 of the electronic device which concerns on this invention. It is an image figure showing the temperature profile of the board | substrate thrown in in the reflow furnace which concerns on this invention. It is a perspective view which shows the external appearance in the board | substrate A surface of Example 2 of the electronic device which concerns on this invention. It is a top view in the board | substrate A surface of Example 2 of the electronic device which concerns on this invention shown in FIG. It is sectional drawing showing the process of the mounting method (manufacturing method) of Example 2 of the electronic device which concerns on this invention. It is a perspective view which shows the external appearance in the board | substrate A surface of Example 3 of the electronic device which concerns on this invention. It is a perspective view which shows the external appearance in the board | substrate A surface of Example 4 of the electronic device which concerns on this invention. It is sectional drawing showing the cross-section of the Example of the electronic device which concerns on this invention. It is sectional drawing showing the structure for performing the strength evaluation (shear test) of the conductive adhesive which concerns on this invention. It is a figure showing the result of the shear strength which measured the intensity | strength of the conductive adhesive which concerns on this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Board | substrate, 2a, 2b ... Land, 3 ... Semiconductor device (surface mount component), 4 ... Lead (terminal), 5 ... Solder, 6 ... Conductive adhesive, 7 ... Chip component (surface mount component), 8 ... Electrode (terminal), 9 ... ground layer, 10a, 10b ... wiring, 11 ... Cu block, 12 ... tool.

Claims (10)

In electronic devices with surface-mounted components on both sides of the board,
In a combination of a plurality of lands provided on the substrate and a plurality of terminals of the surface mount component on at least one surface of both surfaces of the substrate, a combination electrically connected and fixed using solder An electronic device comprising: a combination electrically connected and fixed using a conductive adhesive. The electronic device according to claim 1,
An electronic device comprising a plurality of combinations of the land and the terminal connected and fixed using the conductive adhesive. The electronic device according to claim 2.
The plurality of sets that are electrically connected and fixed using the conductive adhesive include two sets of combinations of the land and the terminal arranged at at least one diagonal position of the surface mount component. An electronic device comprising: The electronic device according to claim 2.
The plurality of sets electrically connected and fixed using the conductive adhesive include a combination of two sets of the land and the terminal located at at least an end of the surface mount component. Electronic device to play. The electronic device according to claim 1,
The electronic device according to claim 1, wherein the land for connecting and fixing the terminal using the solder and the land for connecting and fixing the terminal using the conductive adhesive have different shapes. The electronic device according to claim 5.
An electronic device, wherein a surface area of the land for connecting and fixing the terminal using the solder is smaller than a surface area of the land for connecting and fixing the terminal using the conductive adhesive. The electronic device according to claim 1,
A ground layer is built in the inner layer of the substrate, ground terminals of the surface mount component are connected to the ground layer by wiring, and common signal terminals of the surface mount component are connected by other wiring. An electronic device. In electronic devices with surface-mounted components on both sides of the board,
One surface A of the substrate is a combination of a plurality of lands provided on the substrate and a plurality of terminals of the surface mount component, and a combination electrically connected and fixed using solder and a conductive adhesive A combination that is electrically connected and fixed using
The other surface B of the board is electrically connected and fixed using solder in a combination of a plurality of lands provided on the board and a plurality of terminals of the surface mount component. apparatus. In the manufacturing method of mounting surface mount components on both sides of the board by reflow,
A first step of soldering some of the terminals of the surface-mounted component to one surface A of the substrate by reflow;
A second step of applying a conductive adhesive to the terminals of the surface-mounted component that has not been soldered by reflow to the one surface A of the substrate in the first step;
A third step of soldering the terminals of the surface mount component to the other surface B of the substrate by reflowing,
In the third step, when soldering the terminals of the surface mount component to the other surface B of the substrate by reflow, before the solder is melted using the preheating temperature of the reflow temperature profile, A method of manufacturing an electronic device, comprising: curing and electrically connecting the conductive adhesive applied to the one surface A in the second step. In the manufacturing method of mounting surface mount components on both sides of the board by reflow,
A fourth step of supplying solder to one surface A of the substrate except for some terminals of the surface mount component, applying a conductive adhesive to the remaining terminals, and soldering by reflow;
A fifth step of soldering the terminals of the surface mount component to the other surface B of the substrate by reflowing,
In the fourth step, when soldering the terminal of the surface-mounted component to one surface A of the substrate by reflow, before the solder is melted using the preheating temperature of the reflow temperature profile, A method for manufacturing an electronic device, comprising: curing and electrically connecting the conductive adhesive applied to the one surface A in the fourth step.

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