JPH09260828A - Electronic part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the solder bridging of an electronic component, etc., by forming such slope portions, etc., near its outer peripheral portions present in at least front and rear directions relative to the progressing direction for its dip soldring that each slope portion is made thin-walled toward its outer peripheral side. SOLUTION: Dipping the plane of the mounting surface side of a printed circuit board 18 whereto an electronic component 30 is fastened into a jet wave surface 16, the printed circuit board 18 is moved in a horizontal direction (A) to perform dip soldering of the electronic component 30. In the course of this soldering, a fused solder 12 jetted from each nozzle 14 to hit the electronic component 30 flows smoothly along an slope portion 46 continuing obliquely from the end portion of the slope portion 46 which is close to the surface of the printed circuit board 18 to the top plane of a thick-walled portion 44 of the middle of the electronic component 30. Thereby, no turbulent flow is generated in the closed flow of the fused solder 12 to the electronic component 30. Therefore, no solder bridging is generated to make the adequate soldering of the electronic component 30 possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic component such as an IC mounted and mounted on a wiring board by soldering.

[0002]

2. Description of the Related Art Generally, a printed wiring board used for electric equipment is widely soldered by a solder dipping method. When soldering a multi-legged electronic component to a printed wiring board having a high mounting density by this solder dip method, for example, as shown in FIG. 4, a solder jet bath is used for soldering. That is, the impeller 10 mounted in the solder bath is rotated, and the molten solder 12 in the solder bath is jetted from the nozzle 14 onto the liquid surface, and the jet wave surface 16 that is one step higher than the general liquid surface of the solder bath is generated. When the printed wiring board 18 passes across the jet wave front 16 in this state, the surface portion of the printed wiring board 18 is dipped in the molten solder 12 for soldering. As a result, the electronic component 20 fixed on the printed wiring board 18
Solders each foot 22 to the corresponding wiring circuit conductor (land) of the printed wiring board 18.

The electronic component 20 thus soldered and mounted on the printed wiring board 18 is, for example, a quad flap package (QFP) which is a surface mount type IC package and has a rectangular box-shaped thick wall. Large IC
There is also. When the printed wiring board 18 on which such a large electronic component 20 is mounted is soldered using a jet solder bath, the jet wave front 1 on which the molten solder 12 is being jetted
When the printed wiring board 18 passes through 6, the molten solder 12 hits the upper-side corner portion 20A of the large-sized electronic component 20 to generate a turbulent flow. Further, if there is another electric component 24 near the electronic component 20, the flow of the molten solder 12 is further disturbed.

Therefore, when the electronic component 20 separates from the jet wave front 16 according to the movement of the printed wiring board 18, the flow of the molten solder 12 pulling backward in the traveling direction is disturbed, and the surface tension of the molten solder 12 also acts. Then, as shown in FIG. 5, legs 22 which are a plurality of electrodes of the electronic component 20 are short-circuited by solder, so-called solder bridge 26 (interconductor bridge by solder) occurs, or solder corners occur. There is. Further, the molten solder 12 hits a corner portion 20A of the large electronic component 20 to generate a turbulent flow, and the surface tension and the viscosity of the molten solder 12 act so that the solder is not attached to the foot 22 which is an electrode of the electronic component 20. A portion 28 may be generated.

Therefore, in order to prevent the solder bridge 26 or the solder non-bonding portion 28 from being produced even when soldering is performed by the solder dip method, the printed wiring board 18 passes through the jet wave front 16 as shown in FIG. A means for reducing the turbulent flow by immersing it in the molten solder 12 so that the ridgelines of the corners 20A of the rectangular box-shaped electronic component 20 are inclined with respect to the traveling direction A has been put into practical use.

[0006]

As described above, with respect to the traveling direction A of the printed wiring board 18, the ridgeline of the corner portion 20A is inclined so that the electronic component 20 is melted by the solder 12.
(See FIG. 4).
Is large and thick, the turbulent flow generated by hitting the corner portion 20A cannot be sufficiently reduced, and the solder bridge 26 or the solder non-bonding portion 28 shown in FIG. 5 may occur. was there. In the solder dip method,
The temperature of the molten solder and the dipping time are controlled so as to be within a predetermined condition range so that the electronic component 20 and the like are not damaged by heat. Further, the jet velocity of the molten solder 12 hitting the printed wiring board 18 is also controlled to fall within a predetermined condition range from the viewpoint of the wettability of the solder and the prevention of the electronic component 20 being washed away by the molten solder 12 and missing. I have to do it. Therefore, it is impossible to change the conditions of the molten solder bath to prevent the formation of the solder bridge 26 or the solder non-bonding portion 28, and there is no effective means for this.

In view of the above facts, the present invention is an electronic device configured to be soldered well by using a solder dip method so as not to cause a solder bridge or a solder non-bonding portion even when the electronic component is soldered to a printed wiring board. The purpose is to provide new parts.

[0008]

An electronic component according to claim 1 of the present invention is an electronic component which is mounted by soldering on a printed wiring board by a solder dip method, the solder dip on the upper plane of the electronic component. Characterized in that a sloped portion, a chamfered portion, or a streamlined curved surface is formed so as to be thin toward the outer peripheral side near the outer peripheral portion located at least in the front-rear direction with respect to the traveling direction for soldering by the method. To do.

With the above structure, when the electronic component is immersed in the molten solder bath for connecting the printed circuit board by the solder dip method, the molten solder is at least in the front-back direction with respect to the traveling direction of the electronic component. It is possible to prevent turbulent flow, and to prevent a solder bridge, a solder non-bonding portion, or the like.

An electronic component according to a second aspect of the present invention is the electronic component according to the first aspect, in which the upper plane is protected by sealing at least an integrated circuit chip and the like, and is sucked by a suction cup of an electronic component automatic mounting apparatus. It is characterized in that it is formed in a shape with a possible size.

With the above-mentioned structure, the integrated circuit chip or the like to be protected in the electronic component is sealed under the thick central flat portion so as to be sufficiently protected, and the flat portion is sucked by the suction plate. The electronic component is gripped and can be automatically mounted on the printed wiring board by the electronic component automatic mounting device.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an electronic component of the present invention will be described below with reference to FIGS. 1, 2 and 3. In addition,
1 to 3, parts corresponding to those shown in FIGS. 4 to 6 are given the same reference numerals for convenience of explanation.

FIG. 1 is an explanatory view showing a cross section of a state where soldering is performed by the solder dip method of FIG.
Reference numeral 2 is molten solder, 14 is a nozzle, 16 is a jet wave front, 18 is a printed wiring board, and 30 is an electronic component.

In this electronic component 30, as shown in FIG. 2, an integrated circuit chip 36 is arranged on a die pad 34 at the center of a square plate-shaped lead frame 32. Further, on the lead frame 32, a plurality of leads 38 extending on the four sides are arranged, and the inner lead tips of the leads 38 and the pads of the integrated circuit chip 36 corresponding thereto are connected by metal wires. Connect at 40. Further, what is on the lead frame 32 including the integrated circuit chip 36, the metal wires 40, and the inner lead portions of the leads 38 is sealed with a resin cover portion 42, and external moisture, mechanical shock, light, heat or heat is applied. Try to protect from such energy.

The cover portion 42 is formed by the integrated circuit chip 3
6, and, if necessary, the central thick portion 44 in which a predetermined range (a small square portion in the present embodiment) of the central portion including the position of the metal wire 40 or the like that needs to be sufficiently protected is thick.
And a slanted portion 46 that is formed in a slanted shape and has a large chamfer from the thick portion 44 at the center to the four sides of the outer peripheral portion of the upper plane, and is substantially formed in a quadrangular pyramid shape. .

The upper plane portion of the thick portion 44 has a size and a plane shape that can be sucked by the suction plate of the electronic component automatic mounting apparatus, and the printed wiring board 18 (see FIG. 1).
The electronic component 30 can be mounted on the electronic component automatic mounting apparatus. Electronic component 30 configured as described above
Is fixed to a predetermined position on the printed wiring board 18, and the leads 38 that are the respective electrodes thereof are set so as to be placed on the wiring circuit conductors (lands) of the corresponding printed wiring board 18, respectively.

Next, in this state, as shown in FIG. 1, soldering by a solder dip method is performed. In the jet solder bath of the solder dip method, the molten solder 12 heated and melted at a predetermined temperature in a bath (not shown) is jetted from the nozzle 14 onto the liquid surface by the rotating impeller 10 to generate the jet wave front 16.

Then, the printed wiring board 18 is moved in the horizontal direction A so that the plane on the surface mounting side of the printed wiring board 18 to which the electronic component 30 is fixed is immersed in the jet wave front 16, and the solder dip type solder is used. Make a mark.

During this soldering, the printed wiring board 18
The molten solder 12 ejected from the nozzle 14 onto the upper electronic component 30 hits the electronic component 3 from the end of the inclined portion 46 near the surface of the printed wiring board 18 on the outer peripheral side of the electronic component 30.
A smooth flow with low resistance flows along an inclined surface portion 46 that extends obliquely to the upper plane of the thick portion 44 at the center. Therefore, it is possible to prevent turbulence in the flow of the molten solder 12 near the electronic component 30 on the printed wiring board 18.
Therefore, when the electronic component 30 separates from the jet wave front 16, the molten solder 12 smoothly pulls backward in the traveling direction and flows away, so that proper soldering can be performed without forming a solder bridge. Further, in the vicinity of the electronic component 30, the molten solder 1
Since the turbulent flow of 2 can be prevented, the molten solder 12 is evenly distributed between the lead 38 which is an electrode and the wiring circuit conductor (land), and the solder is properly soldered without causing a solder non-bonding portion. To be done.

In the above-described embodiment, the structure in which the slope portion 46 is formed on the cover portion 42 of the electronic component 30 has been described, but the present invention is not limited to this, and the electronic component 30 is not limited thereto. Molten solder 1 near the outer periphery of the upper plane
In order to prevent turbulent flow from colliding with the flow of 2, the streamlined curved surface (the cross-sectional shape is an arc, a part of an ellipse, etc.) is thinned toward the outer peripheral side so that turbulent flow does not easily occur It may be formed, and even with this configuration, the same effect as that of the slope portion 46 can be obtained.

Further, the sloped portion 46 or the portion forming the streamlined curved surface on the electronic component 30 is not limited to the entire circumference of the electronic component 30, and the electronic component 30 can be soldered by the solder dip method. It may be only forward and backward in the traveling direction. Even in the case of this configuration, turbulent flow can be prevented from occurring in the outer peripheral portion where the flow of the molten solder 12 hits strongly, so that proper soldering can be performed.

[0022]

As described above in detail, according to the electronic component of the present invention, the oblique side or the chamfered portion is formed near the outer peripheral portion of the upper plane of the electronic component so as to become thinner toward the outer peripheral side,
Or, since a streamlined curved surface is formed, when this electronic component is connected to the printed wiring board by the solder dip method, molten solder is prevented from generating turbulent flow in the vicinity of this electronic component, and solder bridge or solder non-attachment There is an effect that good soldering can be performed so that a portion or the like is not generated. Further, when the central upper flat portion of the electronic component is formed to have a sufficient size and shape, the electronic upper component is sucked by the suction plate of the electronic component automatic mounting apparatus to print the electronic component. The effect is that it can be mounted on a wiring board.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing, in a partial cross-section, a state of soldering by a solder dip method in an embodiment of an electronic component of the present invention.

FIG. 2 is a partial cross-sectional perspective view showing an embodiment of an electronic component of the present invention.

FIG. 3 is a plan view showing an embodiment of an electronic component of the present invention.

FIG. 4 is an explanatory view showing a partial cross-section of a soldering state of a conventional electronic component by a solder dipping method.

FIG. 5 is a main part perspective view illustrating the state of an electronic component mounted on a conventional printed wiring board.

FIG. 6 is a perspective view of a main part showing another example of a soldering state of a conventional electronic component by a solder dipping method.

[Explanation of symbols]

 30 electronic parts 32 lead frame 36 integrated circuit chip 38 lead 40 metal wire 42 cover part 44 thick part 46 sloped part

Claims (2)

[Claims] 1. An electronic component to be mounted by soldering on a printed wiring board by a solder dip method, the electronic component being at least a front-back direction with respect to a traveling direction for soldering by the solder dip method on an upper plane of the electronic component. An electronic component, characterized in that a slanted portion, a chamfered portion, or a streamlined curved surface is formed near the outer peripheral portion located at the outer peripheral portion so as to be thin toward the outer peripheral side. 2. The electronic component according to claim 1, wherein the upper plane is formed to have a size capable of encapsulating and protecting at least an integrated circuit chip or the like and being sucked by a suction cup of an electronic component automatic mounting apparatus. An electronic component characterized by.