JP2010103167A - Method for soldering semiconductor device and mounting structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a defect in joining, etc., due to non-fusion of solder on a lower surface of a semiconductor device when a leadless type semiconductor device is soldered without contacting. <P>SOLUTION: Groove portions 3 and 6 are provided adjacently to a plurality of terminal electrodes 4 on a side surface of the leadless type semiconductor device 1 and a terminal electrode 4 of an outermost portion. The terminal electrodes 4 of the semiconductor device 1 extend from the side surface to the bottom surface (lower surface) of the semiconductor device 1 and solder 5 supplied to a land 12 of a printed wiring board 11 is heated to join the respective terminal electrodes 4 to the land 12. The groove portions 3 and 6 adjacent to the terminal electrodes 4 are irradiated with laser beam 8 heating the solder 5 to preheat solder paste on the lower surface of the semiconductor device 1, thereby preventing a joining defect. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a soldering method and mounting structure for a semiconductor device in which a leadless semiconductor device is soldered to a printed wiring board by non-contact local heating.

  Conventionally, when soldering a semiconductor device (electronic component), such as a solid-state image sensor mounted on a digital camera, which has low heat resistance and cannot be soldered by reflow, A mounting method is used in which the solder is melted and joined.

  However, soldering with a soldering iron is a process that is unsuitable for mass production because the quality varies greatly depending on the skill level of the operator, and time is required for soldering.

  In addition, with the recent lead-free soldering, the soldering iron tip is severely damaged, and its replacement cycle is shorter than conventional lead-containing solder, causing a problem of increased production cost and cost. .

  Furthermore, along with miniaturization of electronic devices, electronic components to be mounted have also been miniaturized, and fine portions have to be soldered, and the difficulty of soldering with a soldering iron has been increasing year by year.

  Therefore, in recent years, as an alternative to soldering iron work, a method has been introduced in which a joint is locally heated in a non-contact manner with laser light, hot air, etc., and the solder is melted to join.

  In particular, soldering with a laser beam is a widely used technique because it can be heated more locally, has less exhaust heat, and is easy to automate.

  Laser soldering includes a method in which an electronic component is mounted after printing a solder paste on a printed wiring board, and the joint is locally heated by laser irradiation.

  There is also a method in which electronic components are mounted on a printed wiring board, thread solder is brought into contact with a joint by an automatic feeder, and soldering is performed by irradiating laser light.

  If this process is used, since soldering can be performed automatically, it is possible to avoid a problem that the quality depends on the skill level of the operator.

  In addition, the time required for soldering is shortened, and the production tact can be improved.

  Conventionally, a solid-state image pickup device package mounted on a digital camera has a form having a Small Outline Package (SOP) type lead.

  However, in recent years, there has been a demand for further miniaturization, and ceramic leadless package (CLCC), which is a ceramic leadless package, has begun to be used.

  In a general laser soldering method, first, a peripheral portion of a solder joint portion is preheated with a laser, and then the laser is scanned to the joint portion to melt the solder and join.

  Since the temperature of the joint is raised in advance by performing preheating, solder unmelting can be prevented even if the time during which the laser is directly applied to the solder is short. In addition, by applying preheating, the laser output is set low, and thermal damage to the substrate and the semiconductor device is prevented.

  As a method of applying such preheating, as disclosed in Patent Document 1, a solder paste is printed on a printed wiring board, and laser light is continuously irradiated to the solder paste, and the component is removed while the solder is melted. The method of mounting is known.

  As another method, in Patent Document 2, laser light is irradiated from the back surface of the printed wiring board directly below the bonding portion, and the solder is melted by separately irradiating the surface bonding portion while preheating the bonding portion. A method of making it happen has also been proposed.

Japanese Patent Laid-Open No. 10-335806 JP-A-9-199846

  However, when a leadless semiconductor device is mounted by laser irradiation, the terminal electrode 104 extends from the side surface to the lower surface of the semiconductor device 101 as shown in FIG. Laser light is not directly irradiated.

  Therefore, since preheating cannot be performed, as shown in FIG. 7, the land 112 of the printed wiring board 111, the solder 105, or the side surface of the semiconductor device 101 is irradiated with laser light 108, and the lower side of the semiconductor device 101 is transferred by heat transfer It is necessary to melt the solder.

  However, when the land and solder are irradiated with laser light to melt the solder on the lower surface of the semiconductor device by heat transfer, the heat is taken away by the semiconductor device, so that the solder on the lower surface is not melted, resulting in poor bonding.

  To prevent this defect, measures such as irradiating with laser light for a long time or increasing the output of the laser light are necessary. However, the method of increasing the intensity of the laser light is a thermal damage that burns the printed wiring board. Problems occur. In addition, if laser irradiation is performed for a long time, the time required for production becomes long, which causes a reduction in production tact.

  In the method of directly irradiating the semiconductor device with laser light and melting the solder on the lower surface of the semiconductor device, the temperature of the semiconductor device other than the joint portion rises, causing a problem that the semiconductor device is thermally damaged.

  Furthermore, with the recent lead-free solder, the melting point of conventional Sn-Ag-Cu-based lead-free solder is about 220 ° C., whereas the melting point of conventional solder containing lead is 183 ° C. ing.

  Therefore, it is necessary to set the output of the laser higher, and the possibility of further thermal damage is increased.

  In order to solve this problem, there is a measure of reducing the amount of solder paste in order to melt the solder under the semiconductor device in a short time.

  However, if the amount of solder paste is reduced, the volume of solder after joining becomes small, which causes a problem that joint reliability is lowered.

  Furthermore, in the method disclosed in Patent Document 1, when a large number of terminal electrodes are arranged like CLCC, it is necessary to irradiate lasers at multiple points, and the size of the apparatus needs to be increased.

  In addition, it is necessary to incorporate a device for mounting components in the laser soldering device, which increases the cost of the device.

  Similarly, the method disclosed in Patent Document 2 irradiates laser light from above and below, so that it is necessary to enlarge the apparatus. In addition, since the parts cannot be arranged on the back surface of the portion to be soldered with a laser, there are cases where the board design is limited.

  The present invention relates to a method of soldering a semiconductor device capable of preventing a bonding failure due to unmelted solder on the lower surface of the semiconductor device, which occurs when soldering a leadless semiconductor device, and thermal damage between the semiconductor device and a printed wiring board, and The object is to provide a mounting structure.

  According to another aspect of the present invention, there is provided a method for soldering a semiconductor device in which a semiconductor device having a plurality of terminal electrodes disposed on a side surface is soldered to a land provided on the printed wiring board. Supplying solder to the land, positioning the terminal electrode of the semiconductor device on the land of the printed wiring board supplied with solder, and heating the solder on the land of the printed wiring board And a solder bonding step for bonding the terminal electrodes of the semiconductor device, and a groove is formed on a side surface of the semiconductor device so as to be adjacent to each terminal electrode, and the solder bonding step The solder is preheated by heat supplied to the groove of the semiconductor device.

  By supplying heat from a groove formed on the side surface of the leadless semiconductor device with laser light or the like, the solder on the lower surface of the semiconductor device can be stably heated and melted to prevent poor solder bonding. . In addition, by shortening the irradiation time of the laser light, thermal damage between the semiconductor device and the printed wiring board can be prevented.

  It is possible to perform soldering in a shorter time, and further, it is not necessary to increase the size of the soldering apparatus, and the apparatus cost and the mounting cost can be reduced.

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

  1A and 1B show a method of soldering a semiconductor device according to an embodiment, wherein FIG. 1A is a plan view showing the semiconductor device in a soldering process, and FIG. 1B is an enlarged view showing a part of FIG. It is a fragmentary perspective view. The semiconductor device 1 has a plurality of dents 2 on its side surface. A groove 3 is formed between the recesses 2 so as to be adjacent to each recess 2, and a terminal electrode 4 is disposed in each recess 2. The printed wiring board 11 includes lands 12 connected to the terminal electrodes 4 of the semiconductor device 1 by solder 5.

  As shown in FIG. 2, the terminal electrode 4 extends from the side surface of the semiconductor device 1 to the bottom surface (lower surface).

  Further, a groove portion 6 similar to the groove portion 3 is formed in an adjacent portion of the outermost terminal electrode 4 of the semiconductor device 1.

  In the solder joining process in which the terminal electrode 4 of the semiconductor device 1 is soldered to the land 12 of the printed wiring board 11, solder (solder paste) 5 is supplied to the land 12 of the printed wiring board 11, and the semiconductor device 1 is supplied to each land 12. The terminal electrode 4 is positioned. Then, the solder 5 on the land is heated and melted to perform soldering.

  A heat source for heating the solder 5 is laser light 8 generated from the laser light source 7, scans the laser light irradiation spot 9 through the grooves 6 and 3, and supplies heat to the solder 5.

  3 and 4 show the mounting structure of the soldered semiconductor device 1. In this mounting structure, the terminal electrode 4 of the semiconductor device 1 extends from the side surface to the lower surface of the semiconductor device 1, and a part of the solder 5 that connects the terminal electrode 4 to the land 12 of the printed wiring board 11 is part of the semiconductor device 1. It wraps around from the side to the bottom.

  The mounting structure of the present invention is different from the conventional example shown in FIGS. 6 and 7 in that the groove portion 3 formed in a region sandwiched between a plurality of terminal electrodes 4 arranged in the semiconductor device 1 and the outermost terminal. The groove portion 6 is formed so as to be adjacent to the electrode 4. By irradiating the groove portions 3 and 6 with the laser beam 8, the solder paste applied to the lower surface of the semiconductor device 1 and the peripheral portion of the land 12 can be easily heated.

  Here, the shape of the grooves 3 and 6 is not limited to a semicircular shape as shown in FIG. 1, and may be an oval shape, a square shape, or a triangular shape.

  Further, the angles of the grooves 3 and 6 are not limited to being vertical, but may be tapered.

  The number of the groove portions 3 is not limited to one between the terminals, and a plurality of grooves may be provided.

  Further, the non-contact heating method is not limited to laser light as long as the solder is melted by locally heating such as hot air or a halogen heater.

  The soldering process will be described in detail below.

  First, the solder (solder paste) 5 is supplied onto the land 12 by screen printing or dispensing.

  As a method other than supplying the solder paste to the lands 12, a solder alloy may be formed in advance like a solder precoat.

  Next, the semiconductor device 1 is mounted on the solder 5. At this time, the lands 12 to be joined to the terminal electrodes 4 of the semiconductor device 1 are mounted so as to coincide with each other.

  Thereafter, laser light 8 is first irradiated from the outermost groove 6 to preheat the peripheral portion of the outermost terminal electrode 4 and the solder 5.

  Subsequently, the laser beam 8 is scanned, the solder 5 that joins the outermost terminal electrode 4 and the land 12 is heated and melted, and soldering is performed.

  Further, the laser beam 8 is scanned, preheating is applied from the groove 3 provided between the terminal electrodes, and the adjacent terminal electrodes 4 are soldered together.

  By scanning the laser beam 8 and sequentially soldering the terminal electrodes 4 on the side surfaces, all the terminal electrodes 4 arranged in the semiconductor device 1 can be soldered to the printed wiring board 11.

  By making the land 12 wider than the terminal electrode 4 of the semiconductor device 1 and exposing the land 12 to the groove portion 3, when the laser beam 8 is irradiated, the laser irradiation spot 9 can easily hit the land 12 on the lower surface of the semiconductor device. The melting of the paste is promoted.

  Through the above soldering process, a CLCC type leadless semiconductor device packaged with a solid-state imaging device used in a digital camera was soldered, and the temperature measurement of the lower surface of the semiconductor device and the molten state of the solder were confirmed.

  The CLCC terminal electrode width and terminal electrode distance are each 0.2 mm.

  The groove portions were provided in a semicircular shape with a diameter of 0.2 mm between the terminal electrodes and adjacent to the outermost terminal electrodes.

  The material of the printed wiring board was a glass epoxy base material with a thickness of 1.0 mm. Further, the width of the land of the printed wiring board is wider than the terminal electrode of the semiconductor device joined to 0.3 mm.

  The solder paste alloy is an Sn-Ag-Cu alloy, and the composition ratio of each of the lead-free solders is 96.5 wt% Sn, 3.0 wt% Ag, and 0.5 wt% Cu. used.

  The local heating method is by laser light irradiation. The wavelength of the laser beam is 980 nm and the output is 5 W.

  First, for comparison, soldering is performed by the method of the conventional example shown in FIG. 7, and the temperature of the portion sandwiched between the terminal electrode and the land on the lower surface of the semiconductor device is measured. It rose only to 350 ° C. In contrast, in the soldering method of the present embodiment shown in FIG. 1, the temperature of the joint portion on the lower surface of the semiconductor device increased to 450 ° C. The graph of FIG. 5 shows the temperature measurement results of the conventional example and this example.

  Also, when the solder joints after soldering were observed, in the conventional example, the solder paste was partially unmelted and remained granular, but in this example, the solder paste was melted and the semiconductor device It was confirmed that the electrode on the lower surface was in a good bonding state with the printed wiring board.

  Furthermore, in this example, the time to reach the peak temperature after the laser light irradiation was shortened, and the solder on the lower surface of the semiconductor device could be melted in a short time.

BRIEF DESCRIPTION OF THE DRAWINGS The soldering method of the semiconductor device by one Embodiment is demonstrated, (a) is a top view which shows the process of mounting a semiconductor device on a printed wiring board and fuse | melting solder, (b) is a part of (a). It is an expansion partial perspective view expanded and shown. It is a top view which shows the bottom face of the semiconductor device of FIG. It is a top view which shows the mounting structure of FIG. It is a perspective view which shows the mounting structure of FIG. It is a graph which shows the result of having measured the temperature of the lower surface of a semiconductor device in an example and a conventional example. It is a top view which shows the bottom face of the semiconductor device by a prior art example. It is a top view explaining the soldering method by a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor device 2 Depression 3, 6 Groove part 4 Terminal electrode 5 Solder 7 Laser light source 8 Laser light 9 Laser irradiation spot 11 Printed wiring board 12 Land

Claims (6)

In a method of soldering a semiconductor device in which a semiconductor device in which a plurality of terminal electrodes are arranged on a side surface is soldered to a land provided on a printed wiring board,
Supplying solder to the lands of the printed wiring board;
Positioning the terminal electrode of the semiconductor device on the land of the printed wiring board supplied with solder;
A solder bonding step of heating and melting the solder on the land of the printed wiring board and bonding the terminal electrode of the semiconductor device;
On the side surface of the semiconductor device, a groove is formed so as to be adjacent to each terminal electrode,
A soldering method for a semiconductor device, wherein, in the soldering step, the solder is preheated by heat supplied to the groove portion of the semiconductor device.   2. The method of soldering a semiconductor device according to claim 1, wherein a heat source that heats the solder in a non-contact manner is used in the solder joining step.   3. The method of soldering a semiconductor device according to claim 2, wherein a laser beam is used as the heat source. In a semiconductor device provided with a plurality of terminal electrodes on the side surface for soldering to a land of a printed wiring board,
A semiconductor device, wherein a groove for supplying heat to the solder on the land is provided on a side surface of the semiconductor device so as to be adjacent to each terminal electrode. A semiconductor device in which a plurality of terminal electrodes are arranged on a side surface;
A printed wiring board provided with lands for connecting each terminal electrode of the semiconductor device;
In a mounting structure having a solder joint for connecting the terminal electrode of the semiconductor device to the land of the printed wiring board,
A groove structure is formed on a side surface of the semiconductor device so as to be adjacent to each terminal electrode, and the solder of the solder joint is preheated by heat supplied to the groove.   The mounting structure according to claim 5, wherein the land is exposed in the groove.

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