JPH0576053U - Surface mount electronic components - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a surface mounting field electronic component in which generation of a solder bridge is reduced in a reflow soldering process such as QFP having a large number of pins and a narrow pitch. A surface mount electronic component with lead terminals for soldering to a conductor portion of a printed circuit board, wherein a flux 12 is provided in an intermediate portion of the lead terminals 11a.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a surface mount electronic component, and more particularly to a lead terminal of a surface mount component that can absorb excess solder.

[0002]

[Prior Art]

 A signal wire, etc., is drawn from each terminal of a chip made of semiconductor material, etc. with a gold wire, connected to multiple lead frames, and provided on a printed circuit board, etc. via the lead frame terminals (lead terminals). The flat package, which is connectable to an external circuit and is fixed by covering the base of the chip, the gold wire and the lead frame with a resin body, is used in many devices such as electronic devices.

FIG. 2 shows a conventional configuration example of a QFP (Quad Flat Package) which is a kind of such flat package. According to the QFP shown in FIG. 2, one end of each of the lead frames 1 is connected to the chip 3 by the gold wire 2, and is covered and fixed by the resin body 4. The leg portion and the lead terminal 1a, which are drawn out of the resin body 4 which is the other end of the lead frame 1, are connected and mounted by soldering or the like to a circuit or the like formed on a printed circuit board or the like.

The above-mentioned soldering is usually performed by reflow soldering. In the reflow soldering, an appropriate amount of cream solder is applied by screen printing on a predetermined land of a printed circuit board, QFP and others are automatically mounted, and then a reflow furnace is used. By heating and melting.

[0005]

[Problems to be solved by the device]

 By the way, recent flat packages such as QFP tend to have a large number of pins and a narrow pitch (1.0, 0.8 mm → 0.65, 0.5 mm pitch). The situation was that a solder bridge was likely to occur, which leads to a solder short by connecting the lead terminals.

This solder bridge is apt to occur when the amount of solder exceeds a predetermined amount, or when the wettability of lands and lead terminals is poor and the solder does not spread, resulting in excess solder.

As a measure for the solder bridge, Japanese Utility Model Laid-Open No. 3-69247 discloses that the bottom portion of the lead terminal 1b on the solder joint side is bent into an arc shape as shown in FIG. A structure is disclosed. 5 is a printed circuit board.

However, even if the above-mentioned lead terminal shape is adopted, it is not possible to prevent the solder bridge which occurs with the recent increase in the number of pins and the pitch reduction.

Further, in Japanese Utility Model Laid-Open No. 3-83954, as shown in FIG. 4, a plurality of types of lead terminals having different lengths (long lead terminal 1c, short lead terminal 1d) are provided, and adjacent leads are provided. A structure in which terminals are arranged in different lengths is disclosed. However, like this technology, it was difficult to prevent the solder bridge that occurs with the recent increase in the number of pins and the narrower pitch.

Therefore, it is an object of the present invention to provide a surface mount electronic component that further reduces the occurrence of solder bridges in a reflow soldering process such as QFP having a large number of pins and a narrow pitch.

[0011]

[Means for Solving the Problems]

 According to the present invention, there is provided a surface mount electronic component with a lead terminal for soldering to a conductor part of a printed circuit board, characterized in that a flux is provided in an intermediate part of the lead terminal. Solved by electronic components.

[0012]

[Advantageous Effects] According to the present invention, since the flux is provided in the middle portion of the lead terminal, the surplus solder rises to the flux during the reflow soldering and is easily absorbed. It is possible to reduce the formation of a solder bridge that joins terminals with excess solder.

[0013]

【Example】

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic view of an essential part showing an embodiment having a lead terminal according to the present invention. In particular, FIG. 1A is a view before soldering, and FIG. 1B is soldering. FIG.

As shown in FIG. 1 (a), the lead terminal 11 a of the present invention has a flux 12 made of pine resin applied and formed at an intermediate portion thereof, and the land of the conductor portion of the printed circuit board 15 to be soldered. Solder paste 18 is provided on 16 and lead terminal 11a ends are arranged thereon. As the solder paste 18, Sn63Pb37 solder was used.

With the arrangement of the lead terminals and the printed circuit board 15 as shown in FIG. 1A, soldering (reflow soldering) is normally performed in the reflow furnace, and as shown in FIG. Has risen to the flux 12 in FIG. 1A and is absorbed.

As described above, since the excess solder is absorbed by the flux 12 provided in advance in the intermediate portion of the lead terminal, the solder bridge can be significantly reduced in the lead terminal gap.

In the present embodiment, Sn63Pb37 was used as the solder, and pine resin was used as the flux 12 to be arranged in the middle of the lead terminal. However, the flux material is chemically more active than the solder material used. Suitable for absorbing excess solder.

[0019]

[Effect of the device]

 As described above, according to the present invention, it is possible to significantly reduce the reflow solder bridge in the reflow soldering of a flat package such as QFP, which reduces the number of touch-up steps and improves the soldering quality. And so on.

[Brief description of drawings]

FIG. 1 is a schematic view of a main part showing an embodiment having a lead terminal shape according to the present invention.

FIG. 2 is a perspective view of a configuration example of a conventional QFP.

FIG. 3 is a side view of an example of a conventional lead terminal shape.

FIG. 4 is a perspective view showing an example of a conventional lead terminal shape.

[Explanation of symbols] 1 lead frame 1a, 11a lead terminal 1c lead terminal (long) 1d lead terminal (short) 2 gold wire 3 chip 4,14 resin body 5,15 printed circuit board 6,16 land 7,17 surplus solder 12 Flux 18 Solder paste

Claims (1)

[Scope of utility model registration request] 1. A surface mount electronic component with lead terminals for soldering to a conductor portion of a printed circuit board, wherein a flux is provided in an intermediate portion of the lead terminals.