JP2007294188A - Terminal structure and method of manufacturing terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To satisfactorily produce a solder fillet over an edge portion and achieve both of securing of solder strength and prevention of solder bridge in a terminal structure in which the cross section of a tail portion of a terminal is generally rectangular, the edge portion exists between a bottom surface part and a side surface part of the tail portion and production of plating at the edge portion is not satisfactory. <P>SOLUTION: The tail portion 31 of the terminal 3 has the bottom surface part 311 opposed to a circuit board 5, and the side surface part 312 formed generally perpendicular to the bottom surface part 311. A plurality of vertical grooves 316 each having an end connected to the bottom surface part 311 and the other end extending out in such a direction as to get away from the bottom surface part 311 are provided parallel to each other on the side surface part 312. Since molten solder flows into each of the vertical grooves 316 by capillarity and is held by the interfacial force in a portion between every adjacent ones of the vertical grooves 316 in the side surface part 312 of the tail portion 31, it is possible to gain height and width of the fillet 8. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a terminal structure that is mounted on an electronic component and is surface-mounted on a circuit board, and a method for manufacturing the terminal. In particular, when the tail portion of the terminal is surface-mounted on a circuit board, the present invention is robust without causing a solder bridge. The present invention relates to a solderable terminal structure and a terminal manufacturing method.

  Terminals mounted on electronic components such as integrated circuit components and electrical connectors have the incompatible problem of preventing the occurrence of solder bridges and ensuring soldering strength (connection reliability) when the tail part is mounted on a circuit board. I have it.

  In Patent Document 1 (Japanese Patent Application Laid-Open No. 06-140556), as shown in FIG. 5, a lead (terminal 3) protruding from a surface-mounted electronic component 10 with a lead is formed in a waveform. An arc-shaped landing portion 3a that is in contact with the conductor pattern 52 of the circuit board 5 and an arc-shaped floating portion 3b that is formed so as to float with respect to the landing portion 3a are alternately provided at the tip portion. ing. The intent of the present invention is to absorb excess molten solder into the lower space of the floating part 3b by capillarity when a sufficient amount of solder that can prevent the occurrence of open joints is used. Prevents the generation of solder bridges between terminals 3 arranged in parallel with each other, and at the same time improves the soldering strength by the solder solidified in the lower space of the floating part 3b (shown by dots in FIG. 5) It is in point to let you.

  There is certainly a case where the terminal 3 having such a structure can simultaneously prevent the occurrence of solder bridges and ensure the soldering strength. As shown in FIG. 6, when the cross-sectional shape of the terminal 3 is circular and the plating 9 for ensuring solder wettability is formed on the surface thereof in a substantially uniform and desired thickness. It is.

  On the other hand, since many of the terminals 3 incorporated in the connector are formed by punching a thin metal plate, the cross-sectional shape of the tail portion 31 for soldering the terminals 3 to the circuit board 5 as shown in FIG. Is a substantially rectangular shape having edge portions 36 at the four corners. After the tail portion 31 is plated 9 to ensure solder wettability, it is further used for the purpose of whisker countermeasures, alloying of the base material / plating material, and the like. When heat treatment is performed, it is difficult to ensure the soldering strength.

  The reason for this is that the plating 9 generated on the surface of the tail portion 31 shown in FIG. 7 is melted by the heat of the heat treatment, and the molten plating layer in the edge portion 36 is attracted to the central portion by surface tension or the like, and the edge portion 36 When the plating is thinned and the plating layer is thinned, the wettability of the solder is impaired, and the molten solder on the bottom surface portion 311 of the tail portion 31 climbs over the edge portion 36, climbs up the side surface portion 312 and grows the fillet 8. This is because the process cannot be performed.

  The presence of the fillet 8 determines the soldering strength of the terminal 3 to the circuit board 5. Therefore, for a connector or the like that receives stress on the fillet 8 every time the flexible board is inserted and removed or the socket and the plug are fitted and detached, the generation (height and width) of the fillet 8 is an important issue.

Japanese Patent Laid-Open No. 06-140556

  The present invention has been made in view of the above circumstances, and an object of the present invention is to make the cross-sectional shape of the tail portion 31 of the terminal 3 substantially rectangular, and between the bottom surface portion 311 and the side surface portion 312 of the tail portion 31. In the terminal structure in which the edge portion 36 is present and the plating 9 is not satisfactorily generated at the edge portion 36, the solder fillet 8 can be satisfactorily generated by overcoming the edge portion 36. An object of the present invention is to provide a terminal structure and a terminal manufacturing method capable of achieving both generation prevention.

  To achieve the above object, the invention according to claim 1 is a structure of a terminal to be mounted on an electronic component, the terminal having a tail portion that is surface-mounted on a circuit board, and the tail portion includes: A bottom surface portion facing the circuit board; and a side surface portion formed substantially at right angles to the bottom surface portion. One end of the side surface portion is connected to the bottom surface portion, and the other end is separated from the bottom surface portion. A plurality of longitudinal grooves extending in the direction to be arranged.

  According to a second aspect of the present invention, a recess is formed in the bottom surface, and the longitudinal groove is connected to the recess.

  According to a third aspect of the present invention, when the terminal is manufactured by punching, the vertical groove is formed by a stamping convex mold provided on a die surface and a punch surface of the processing apparatus.

  According to the present invention, the terminal structure in which the cross-sectional shape of the tail portion of the terminal is substantially rectangular, the edge portion exists between the bottom surface portion and the side surface portion of the tail portion, and the plating at the edge portion is not good. In this case, the solder fillet can be satisfactorily generated over the edge portion, and both the securing of the soldering strength and the prevention of the occurrence of solder bridges can be achieved.

  Preferred embodiments of the present invention will be described with reference to the accompanying drawings.

  In FIG. 1, reference numeral 1 denotes a connector for a flexible substrate such as an FPC (flexible printed circuit) or FFC (flexible flat cable) (corresponding to an electronic component in the claims). The connector 1 includes a synthetic resin housing 2, a large number of terminals 3 made of a conductive material implanted in the housing 2, an actuator 4 rotatably supported on the housing 2, and the like. A flexible board (not shown) is inserted into the board insertion / extraction opening 21, and then the actuator 4 is tilted as shown in FIG. 2, and the flexible board inserted into the board insertion / extraction opening 21 is pressed against the terminal 3 by the pressing portion 41. And the connector 1 can be connected.

  Reference numeral 7 denotes a lock member formed by pressing a metal plate or the like. The lock member 7 is incorporated in the housing 2, and the actuator 4 rotated in a locking hole 71 provided in the lock member 7. The protrusions 42 are engaged so that the actuator 4 can be maintained in the lateral state (the state in which the flexible substrate is sandwiched). As will be described in detail later, the connector 1 is mounted on a circuit board. In this embodiment, in order to improve the mounting strength, a fixing metal 6 to be soldered to the circuit board is attached to the end surface 23 of the housing 2. It is attached.

  The connector 1 is mounted on a circuit board 5 as shown in FIG. Specifically, the positioning boss 22 provided in the housing 2 is inserted into the positioning hole 51 provided in the circuit board 5, and the tail portion 31 of the terminal 3 is soldered to the conductor pattern 52 provided in the circuit board 5.

  In this embodiment, the terminal 3 is formed by punching a metal plate made of phosphor bronze having a thickness of 0.2 mm. As shown in FIG. 2, the tail 3 is surface-mounted on the conductor pattern 52 of the circuit board 2. Part 31, upper arm 32 disposed facing substrate insertion opening 21, contact portion 33 formed on upper arm 32 and connected to a flexible substrate inserted into substrate insertion opening 21, and below upper arm 32 It has two insertion pieces 34, 35 arranged. This terminal 3 is press-fitted into the housing 2 from the left in FIG.

  Since the terminal 3 is manufactured by punching the metal plate, the tail portion 31 is formed in a substantially rectangular parallelepiped shape, and the bottom surface portion facing the circuit board 5 as shown in FIGS. 3 (a) and 3 (b). 311, a pair of side surface portions 312 formed substantially perpendicular to the bottom surface portion 311, a front surface portion 313 located on the outer side in the width direction of the terminal 3 (left side of FIG. 3A), and the inner side in the width direction (FIG. 3A ) On the right side) of the rear portion 314 and the top surface portion 315.

  A plurality of vertical grooves 316 formed in the vertical direction on the side surface 312 of the tail portion 31 are spaced apart in the width direction of the terminal 3 (the horizontal direction in FIG. 3A) (three in the present embodiment). Book) is formed. The vertical groove 316 has one end connected to the bottom surface portion 311 and the other end extending in a direction away from the bottom surface portion 311. In the present embodiment, the vertical groove 316 extends in a direction orthogonal to the bottom surface portion 311, but may extend obliquely with respect to the bottom surface portion 311.

  As shown in FIGS. 3A and 3B, the longitudinal groove 316 in the present embodiment has a height h = 0.2 mm, which is substantially half of the height H = 0.4 mm of the tail portion 31. Are formed in a V-shaped cross section having a width L = 0.05 mm, and are engraved on the side surface portion 312 with three stripes at a pitch P of 0.1 mm and a depth F = 0.03 mm.

  The longitudinal groove 316 is stamped by stamping with a stamping die provided on the die surface and punch surface of the processing device when the terminal 3 is punched, or punched with a stamping die separately prepared after the terminal 3 is punched. To be molded. Note that the longitudinal groove 316 is not limited to a V-shaped cross section, and may be U-shaped, W-shaped, trapezoidal, or the like, and its forming means is limited to stamping by the punch, press, or the like. is not.

  A concave portion 317 that functions as a solder pool is formed in the bottom surface portion 311 of the tail portion 31. The depth T of the recess 317 is 0.02 mm, and the lower end of the vertical groove 316 is connected to the recess 317.

  Moreover, the lower end of the front part 313 and the lower end of the back part 314 of the tail part 31 are rounded parts 318 and 319 formed in a rounded shape when viewed from the side, as shown in FIG. The radius R of the round portions 318 and 319 is 0.1 mm, and a concave portion 317 is formed between the round portions 318 and 319. And the above-mentioned vertical groove 316 is arranged in parallel in the side part 312 where it is difficult to form such a round shape. Further, the thickness G of the terminal 3 is 0.2 mm.

  In addition, the said each dimension and the number of strips of the vertical groove 316 are illustrations, and are not limited to this numerical value.

  Now, as described above, the terminal 3 according to the present embodiment in which the longitudinal groove 316 is arranged in parallel on the side surface portion 312 of the tail portion 31 also has an electrical property in order to ensure solder wettability after punching. A plating layer of tin or the like is generated by plating, and then heat treatment is performed for the purpose of whisker countermeasures, alloying of the base material / plating material, and the like.

  During this heat treatment, the plating layer around each edge portion of the tail portion 31 is melted and dissipated by the heat of the heat treatment. As a result, the molten plating collects in the vertical groove 316 by an action such as a capillary phenomenon, The thickness of the plating layer increases. In addition, during the heat treatment, the lower end of the vertical groove 316 connected to the concave portion 317 of the bottom surface portion 311 is an edge, and the plating layer generated here melts and dissipates, but the vertical groove 316 Inflowing peripheral plating prevents this and prevents the plating layer from becoming thin. Therefore, the thickness of the plating layer in the vertical groove 316 can be made sufficient to ensure a predetermined solder wettability from the lower end to the upper end of the vertical groove 316.

  Thereafter, the terminal 3 is incorporated into the housing 2 of the connector 1 shown in FIGS. 1 and 2, and the tail portion 31 is soldered to the conductor pattern 52 of the circuit board 5. During this soldering, the molten solder crawls up in the longitudinal grooves 316, and fillets 8 (indicated by dots in the figure) are formed as shown in FIGS. 4 (a), 4 (b) and 4 (c). The vertical groove 316 is generated from the lower end to the upper end. This is because the plating layer for improving the solder wettability from the lower end to the upper end of the vertical groove 316 is secured with a sufficient thickness, and the vertical groove 316 acts like a capillary phenomenon to cause the molten solder to flow into the vertical groove. This is because 316 is sucked from the lower end to the upper end. Further, the lower end of the vertical groove 316 is connected to a concave portion 317 formed in the bottom surface portion 311, and the concave portion 317 serves as a solder pool for molten solder.

  The molten solder sucked up in each vertical groove 316 of the side surface portion 312 of the tail portion 31 in this manner is pulled up by the surface tension in the portion between one vertical groove 316 and the adjacent vertical groove 316 in the side surface portion 312. And fillet 8 is generated there. As a result, a wide fillet 8 is generated on the side surface portion 312 of the tail portion 31 to the vicinity of the upper end of the vertical groove 316 and according to the three parallel widths of the vertical grooves 316, and the soldering strength is increased. be able to.

  In addition, since the fillet 8 is high and widely generated as described above, the volume of the fillet 8 is larger than that of the type without the longitudinal groove 316. Therefore, even if soldering is performed using a sufficient amount of solder to reliably avoid the open joint, the molten solder is absorbed as the fillet 8 described above, and the occurrence of solder bridges is prevented. .

  Note that the lower ends of the front portion 313 and the back portion 314 of the tail portion 31 of the terminal 3 are round portions 318 and 319 formed in a round shape when viewed from the side, so that there is no need to provide a longitudinal groove 316 or the like. There is no problem in the generation of the fillet 8, but a higher fillet 8 may be generated by providing a longitudinal groove 316 on one or both of the front surface 313 and the back surface 314.

  Further, in the present embodiment, the thickness of the plating layer at the edge portion of the tail portion 31 of the terminal 3 has been described as being thinned by the heat treatment. However, the reason may be other causes or the thickness of the plating layer. It is possible to enjoy the effect (both ensuring the soldering strength and preventing the occurrence of solder bridges) due to the above-described vertical groove 316. This is because the molten solder flows into each vertical groove 316 by capillary action, and the molten solder is held in the portion between the vertical grooves 316 of the side surface portion 312 of the tail portion 31 by surface tension.

  The present invention can also be applied as a terminal structure of an electronic component such as an integrated circuit other than the connector 1.

It is a perspective view of the connector in which the terminal concerning one embodiment of the present invention was built. FIG. 2 is a cross-sectional view in which the connector shown in FIG. 1 is mounted on a circuit board and the actuator is closed. 3A is a side view of the tail portion of the terminal shown in FIGS. 1 and 2, and FIG. 3B is a bottom view of the tail portion. 4A is a plan view when the tail portion of the terminal shown in FIG. 3 is soldered to the circuit board, and FIG. 4B is a cross-sectional view taken along line bb in FIG. 4A. 4 (c) is a cross-sectional view taken along the line cc of FIG. 4 (a). It is explanatory drawing which shows the terminal as a prior art example. It is sectional drawing of what gave plating and heat processing to the terminal of circular section. It is sectional drawing of what plated and heat-processed the terminal of a rectangular cross section.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Connector as electronic component 3 Terminal 31 Tail part 311 Bottom part 312 Side part 316 Vertical groove 317 Recessed part

Claims (3)

A structure of a terminal mounted on an electronic component,
The terminal has a tail portion that is surface-mounted on a circuit board,
The tail portion has a bottom surface portion facing the circuit board, and a side surface portion formed substantially at right angles to the bottom surface portion,
A terminal structure characterized in that a plurality of vertical grooves, one end of which is connected to the bottom surface portion and the other end of which extends in a direction away from the bottom surface portion, are arranged in parallel on the side surface portion. A recess is formed on the bottom surface,
The terminal structure according to claim 1, wherein the longitudinal groove is connected to the recess. 3. The terminal according to claim 1, wherein, when the terminal is manufactured by punching, the vertical groove is formed by a stamping convex mold provided on a die surface and a punch surface of the processing apparatus. Manufacturing method.

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