JP2007258209A - Mounting method of electronic component, soldering device, and mounting substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mounting method capable of mounting an electronic component with high strength without damaging a printed board, a soldering device, and a mounting substrate. <P>SOLUTION: The soldering device is prepared comprising an injection unit 10 for pressing semi-molten solder 11 into a through-hole 3 of the printed board 2 and a heater 16 for keeping the solder heated in a solid and liquid coexistence temperature region (semi-molten state). After the lead 4 of the electronic component is inserted into the through-hole 3 of the printed board 2, the semi-molten solder 11 received from the heater 16 into an injection sleeve 13 is pushed out from a nozzle 12 by advancing a plunger 14 to be pressed into the through-hole 3, thereby preventing a rise in temperature of the printed board 2. The through-hole 3 is sufficiently filled with the solder 11, also a fillet 11' is formed on both front and rear faces of the printed board 2, and the lead 4 is rigidly joined with a land 7 around the through-hole 3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique for mounting an electronic component on a printed circuit board by soldering. More specifically, the present invention relates to a mounting method for soldering an electronic component with leads to a land around a through hole of the printed circuit board. The present invention relates to a soldering apparatus and a mounting board obtained by the mounting method.

  In order to mount electronic components with leads on the printed circuit board, the electronic components are mounted on the printed circuit board with the leads inserted into the through-holes of the printed circuit board, and the printed circuit board is transported on a solder bath. Flow soldering is generally employed in which molten solder is brought into contact with the back surface to join the lead and the land of the printed circuit board.

  By the way, some electronic parts have low heat resistance and are difficult to flow solder, or because of weight and sizing conditions (high weight, large size), the amount of solder is insufficient only by flow soldering. In this case, soldering (increase) is performed manually with a soldering iron after the flow treatment. Moreover, the flow soldering may be incomplete for some reason, and in this case as well, the soldering iron is used for correction (correction) after the flow treatment. In addition, as a measure against the insufficient amount of solder, for example, in the one described in Patent Document 1, an auxiliary member is arranged in advance on the land surface near the through hole, and a solder bridge is generated between the auxiliary member and the lead, The amount of solder attached to the lead is increased.

  FIG. 2 shows an embodiment of soldering with a soldering iron 1, and the soldering iron 1 is placed near the mouth of the through-hole 3 with the electronic component lead 4 inserted into the through-hole 3 of the printed circuit board 2. The wire solder 5 is melted by the heat of the soldering iron 1, the molten solder 6 is injected into the through hole 3, and the lead 4 is joined to the land 7 around the through hole 3.

  However, in recent years, the number of printed circuit boards has increased, and accordingly, the copper wiring density has increased and the heat capacity of the printed circuit board tends to increase. For this reason, in the soldering with the soldering iron 1 described above (soldering with a soldering iron method), it takes time to heat the printed circuit board 2 with the soldering iron 1, and accordingly, the contact time between the soldering iron 1 and the printed circuit board 2 is increased. In addition, there is a risk that the printed circuit board 2 is damaged (disconnected). In recent years, the use of Pb-free solder containing no Pb has been promoted due to environmental problems. However, the melting point of Sn-Ag solder frequently used as Pb-free solder is as high as about 220 degrees. When high melting point Pb-free solder is used, the temperature of the soldering iron is further increased, and the risk of damage to the printed circuit board is further increased. Some Pb-free solder has a relatively low melting point of about 200 ° C. (see, for example, Patent Document 2), but even in this case, the risk of damage to the printed circuit board cannot be avoided.

  Further, in the soldering method using the soldering method, since the molten solder 7 is filled into the through hole 3 only by its wettability, the molten solder 7 is only partway through the through hole 3 as shown in FIG. There was also a problem that the solder was not filled and the solder filling amount was insufficient, so that anxiety remained in terms of bonding strength.

JP 2000-208908 A JP 2003-51671 A

  The present invention has been made in view of various problems of the soldering of the iron method described above, and the problem is that a new electronic component can be mounted with high strength without damaging the printed circuit board. It is to provide a mounting method, a soldering apparatus, and a mounting substrate.

  In order to solve the above-described problem, the electronic component mounting method according to the present invention includes a step of inserting a lead of an electronic component into a through hole of a printed circuit board, and then injecting the molten or semi-molten solder using the injection means. The electronic component is soldered to a printed circuit board by press-fitting into the printed circuit board.

  In the electronic component mounting method performed in this way, the molten or semi-molten solder is press-fitted into the through hole of the printed circuit board by using the injection means, so that the heating of the printed circuit board is suppressed, and further, into the through hole. A sufficient solder filling amount is secured.

  In the mounting method of the present invention, the kind of the solder is arbitrary, and various Pb-free solders having different melting points can be used as well as general-purpose Sn-Pb solder. Moreover, when using Pb free solder, you may select what has a solid-liquid coexistence temperature range, and in this case, a solder can be press-fitted into a through-hole by making it a semi-molten state.

  The soldering apparatus according to the present invention includes a heating unit that heats and holds the solder in a semi-molten state, and an injection unit that receives the solder that has been semi-molten by the heating unit and injects the solder from the nozzle at the tip. Features. In this case, the heating means may include a setting means for automatically setting the heating temperature according to the type of solder.

  The mounting board according to the present invention is a mounting in which a lead of an electronic component is inserted into a through hole of a printed circuit board, and the lead is joined to a land around the through hole via a solder layer filled in the through hole. In the substrate, the solder layer filled in the through hole is formed by press-fitting molten or semi-molten solder into the through hole using an injection unit. In this case, the solder layer is preferably configured to form fillets on both the front and back surfaces of the printed circuit board.

  According to the present invention, when the electronic component is soldered to the printed circuit board, heating of the printed circuit board is suppressed, so that the printed circuit board is not damaged even when the number of layers is increased. Is sufficiently secured, the bonding strength of the electronic component to the printed circuit board is sufficiently increased, and a highly reliable mounting board with high quality can be stably obtained.

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

  FIG. 1 illustrates one embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the part same as the part shown in FIG. In the figure, 10 is an injection device (injection means) for press-fitting semi-molten solder 11 into the through-hole 3 of the printed circuit board 2, and 16 is a solid-liquid coexistence temperature region (half-liquid). It is a heating device (heating means) for heating and holding in a molten state. The injection device 10 and the heating device 16 constitute a soldering device for soldering the lead 4 of the electronic component to the printed circuit board 2.

  The injection device 10 includes an injection sleeve 13 having a nozzle 12 at the tip, a plunger 14 slidably mounted on the injection sleeve 13, one end connected to the plunger 14, and the other end to the outside of the injection sleeve 13. And an extended rod 15. The injection device 10 may be a manual type or an automatic type, and in any case, after receiving the semi-molten solder 11 in the injection sleeve 13, the plunger 14 is pushed through the rod 15. Thus, the solder 11 in the injection sleeve 13 is injected from the nozzle 12. The injection sleeve 13 may be provided with a heater or a built-in heater. In this case, the cooling of the solder 11 can be suppressed. It is also effective to suppress the cooling of the solder 11 by bonding a heat insulating material to the tip of the plunger 15 that contacts the solder 11. On the other hand, the heating device 16 includes a heating furnace 17 incorporating a heater and a controller 18 that controls the temperature of the heating furnace 17. The controller 18 may include a setting unit (not shown) that automatically sets the heating temperature according to the type of solder. In this case, the solder is in a solid-liquid coexistence temperature range according to the switch operation indicating the solder type. And kept at a predetermined temperature.

  In order to mount the electronic component on the printed circuit board 2, the solder is heated and held in a semi-molten state in the heating furnace 17 of the heating device 16 in advance. Then, after inserting the lead 4 of the electronic component into the through hole 3 of the printed circuit board 2, the solder 11 heated to a semi-molten state is supplied from the heating device 16 to the injection sleeve 13 of the injection device 10. The solder 11 is ejected from the nozzle 12 by operating the plunger 14 and is press-fitted into the through hole 3. By this press-fitting, the solder 11 flows in the through hole 3 and moves toward the lower surface side of the printed circuit board 2, so that the through hole 3 is sufficiently filled with the solder 11. Further, the solder 11 that has flowed toward the lower surface side of the printed circuit board 2 flows out from the lower opening of the through-hole 3 and expands onto the flange surface of the land 7, thereby the lower surface side of the printed circuit board 2. Is formed with a fillet 11 '. On the other hand, after filling the through hole 3 with the solder 11, an appropriate amount of the solder 11 is injected from the nozzle 12 of the injection sleeve 13, thereby forming a fillet 11 ′ on the surface side of the printed board 2. In this case, since the solder 11 is in a viscous semi-molten state, the fillet 11 ′ can be easily formed.

  In this way, the lead 4 of the electronic component is joined to the land 7 around the through hole 3 by the solder (solder layer) 11, and the mounting of the electronic component on the printed circuit board 2 is completed. The semi-molten solder 11 is press-fitted into the through hole 3 from the nozzle 12 of the injection cylinder 13, so that the printed circuit board 2 is heated to a high temperature as in the conventional soldering iron 1 (FIG. 2). Therefore, even if the printed circuit board 2 is multilayered and its heat capacity is increased, the printed circuit board 2 is not damaged. Further, since the periphery is not exposed to high heat, even when an electronic component having low heat resistance is mounted, the damage can be prevented in advance. Moreover, since the solder 11 is sufficiently filled in the through-hole 3, the bonding strength between the lead 4 and the land 7 of the electronic component is increased, and even if the electronic component is heavy or large in size, Can be stably mounted on the pulling substrate 2. Particularly in the present embodiment, since the solder fillets 11 ′ are formed on both the front and back surfaces of the printed circuit board 2, the bonding strength is further increased, and it is suitable for mounting high-weight and large-sized electronic components. .

  In the above-described embodiment, the semi-molten solder 11 is press-fitted into the through-hole 3, but the present invention may naturally press-fit the molten solder into the through-hole 3. Also in this case, since the molten solder is pressed into the through hole 3 through the nozzle 12 of the injection cylinder 13 as described above, the printed circuit board 2 is not heated to a high temperature.

  Here, as the solder 11 used for the above-described soldering, it is desirable to use Pb-free solder not containing Pb. On the other hand, when the mounting board is used in, for example, an electronic control unit (ECU) of an automobile, it becomes a use environment of high temperature and high humidity. Therefore, it is desirable to use solder having sufficient resistance to such an environment. . Examples of solder that satisfies these conditions include those shown in Table 1.

  Among the solders shown in Table 1, the Sn-3.0Ag-0.5Cu alloy has a eutectic composition, and this alloy is preferably selected when used in a molten state. Further, in the present invention, since the injection device 10 is used to press-fit into the through hole 3 of the printed circuit board 2, it is not necessary to set the temperature to be in a molten state so high, and the use temperature is plus 10 from the melting point (219 ° C.). It is sufficient to set the temperature to about 0 ° C., ie about 230 ° C.

  On the other hand, Sn-3.0Ag-1.2Cu alloy, Sn-3.5Ag-0.5Bi-3.0In alloy and Sn-10Bi-5Zn alloy in Table 1 all have a solid-liquid coexistence temperature range. These alloys are selected when used in a semi-molten state. The operating temperature of these alloys is an intermediate temperature between the solidus and liquidus, but the Sn-10Bi-5Zn alloy has a temperature difference between the solidus and liquidus that is different from the other two. Since it is wide and the use temperature is low, it is advantageous in terms of workability.

  For example, in Patent Document 2 (Japanese Patent Laid-Open No. 2003-51671), Pb-free solders such as Sn-1Bi-8Zn alloy and Sn-3Bi-8Zn are described (see [Table 1]) The temperature difference between them is 7 ° C. in the former and 10 ° C. in the latter. When such a solder is selected, it is disadvantageous in terms of workability. In addition, these alloys have problems in terms of heat resistance and moisture resistance, and are difficult to apply to the ECU.

It is sectional drawing which shows typically one Embodiment of the mounting method of the electronic component which concerns on this invention. It is a side view which shows typically the mounting method of the conventional electronic component performed using a soldering iron.

Explanation of symbols

2 Printed circuit board 3 Through hole 4 Electronic component lead 10 Injection device (injection means)
11 Solder (solder layer)
11 'fillet 12 nozzle 13 injection sleeve 14 plunger 16 heating device (heating means)
17 Heating furnace 18 Controller

Claims (7)

  After inserting the lead of the electronic component into the through hole of the printed circuit board, the molten or semi-molten solder is press-fitted into the through hole using an injection means, and the electronic component is soldered to the printed circuit board Electronic component mounting method.   2. The electronic component mounting method according to claim 1, wherein Pb-free solder is used as the solder.   The electronic component mounting method according to claim 2, wherein the Pb-free solder has a solid-liquid coexistence temperature range.   A soldering apparatus comprising: a heating unit that heats and holds a solder in a semi-molten state; and an injection unit that receives the solder that has been semi-molten by the heating unit and injects the solder from a nozzle at the tip.   5. The soldering apparatus according to claim 4, wherein the heating means includes setting means for automatically setting the heating temperature according to the type of solder.   An electronic component lead is inserted into a through hole of a printed circuit board, and the lead is filled in the through hole in a mounting board in which the lead is joined to a land around the through hole via a solder layer filled in the through hole. A mounting board, wherein the solder layer is formed by press-fitting molten or semi-molten solder into the through-hole using an injection means. The mounting board according to claim 6, wherein the solder layer forms fillets on both the front and back surfaces of the printed board.

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