JP3247475B2 - Electronic component joining method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for joining electronic parts, such as a semiconductor element or the like, mounted on a printed circuit board and connected to a predetermined circuit using a low melting point alloy such as solder.

[0002]

2. Description of the Related Art Generally, as shown in FIG. 11, a semiconductor element of an integrated circuit type comprises a plurality of outer lead portions 2, 2,... Each outer lead portion 2 is formed flat. In the case of performing printed wiring using such a semiconductor element, a low melting point alloy layer for bonding is provided in advance on a conductor layer of a printed board by a method such as solder plating, and the outer lead portion 2 is mounted thereon. Pressurization and heating.

[0003]

In this case, as shown in FIG. 12, a portion 5a of the low melting point alloy layer 5 provided on the conductor layer 4 of the printed circuit board 3 is sufficiently covered on the surface of the outer lead portion 2. If it is not spread over a large area, a highly reliable bonding effect cannot be obtained, and it is difficult to visually determine the quality of the bonded state.

[0004]

According to the present invention, an outer lead portion of an electronic component is placed on a low melting point alloy layer provided on a conductor layer of a printed circuit board, and the outer lead portion is pressed by a heating tool. In the method of bonding the electronic component to the printed circuit board by performing, a small hole is formed in each of the plurality of outer lead portions of the electronic component, and a heating tool having a pressing surface formed along the arrangement position of the small hole is used. An electronic component bonding method, wherein a plurality of outer lead portions are pressed at once at positions where these small holes are formed to bond the plurality of outer lead portions onto the conductor layer. .

[0005] The small hole may be an elliptical hole whose major axis is set in the longitudinal direction of the outer lead portion. Further, the outer lead portion may have a wide portion centered on the small hole. Further, it is preferable that the heating tool is a plate-like body made of a good heat conductive metal.

[0006]

According to the present invention, when both the outer lead portion and the low melting point alloy layer below the outer lead portion are heated, the small holes act to suck up a part of the melted low melting point alloy layer by capillary action. A part of the alloy layer not only wraps around the surface through the side surface of the outer lead portion, but also wraps around the surface well through the small hole. Further, the presence of the small holes can increase the bonding area of the low melting point alloy layer to the outer lead portion, so that a highly reliable bonding effect can be obtained, and the quality of the bonded state can be easily determined by visual inspection. Further, since heating and pressing of the plurality of outer lead portions and the corresponding low melting point alloy layer are performed by a common heating tool, the joining of each outer lead portion becomes uniform, resulting in good quality, and at a plurality of locations. Can be achieved all at once and is efficient.

[0007]

Next, an embodiment will be described. As shown in FIG. 1, a semiconductor element 6 of an integrated circuit type has a plurality of outer lead portions 8, 8,... Protruding in at least one direction from at least one side surface of a resin-sealed main body portion 7. The part 8 has a small hole 9 passing through the plate surface.

On the other hand, the printed circuit board 3 has conductor layers 4 arranged corresponding to the plurality of outer lead portions 8, 8,...
Each conductor layer 4 has on its surface a solid solution solder layer (low melting point alloy layer) 5 formed by solder plating or cream solder reflow. The outer lead portions 8 of the semiconductor element 6 are stacked on the low melting point alloy layer 5. Reference numeral 10 denotes a pressing element that sequentially lowers and ascends for evacuation, and 11 denotes a projector that projects a laser beam for heating.

Referring to FIG. 2, when the width W of the outer lead portion 8 is 0.5 mm and the arrangement pitch P of the outer lead portions 8 is 1.2 mm, the diameter φ of the small hole 9 is about 0.3 mm.
mm. The small holes 9 are preferably formed during the manufacturing process of the semiconductor element 6, and the outer lead portions 8 in the illustrated example correspond to the outer frame portions 1 of the lead frame.
2 (portion cut during the semiconductor manufacturing process).

The small holes 9 can be formed by punching using a mold or laser processing. When the etching process is applied, the outer lead portion of the lead frame made of copper or the like is covered with an acid-resistant photoresist film having a pattern with small holes, and the small holes 9 are obtained by dipping in an etching solution containing ferric chloride or the like. Can be. In the embodiment shown in FIG. 3, two small holes 9, 9 are provided for each outer lead portion 8.

Now, in the configuration shown in FIG.
As a result, the outer lead portion 8 is strongly pressed toward the conductor layer 4. Next, the focused laser beam 13 is emitted from the light projector 11 and the low melting point alloy layer 5 is heated. When the low-melting point alloy layer 5 is melted by this heating, a part of the layer passes through the side surface of the outer lead portion 8 and wraps around the surface of the outer lead portion. On the other hand, the small hole 9 raises a part of the melted low melting point alloy layer by suction by capillary action. Then, the raised low melting point alloy spreads well on the surface of the outer lead portion.

As shown in FIGS. 4 and 5, a portion 5a of the low melting point alloy layer 5 covers the surface of the outer lead portion 8 over a wide area. In addition, since the bonding area between the outer lead portion 8 and the low melting point alloy layer 5 can be increased by the small holes 9, the outer lead portion 8 can be firmly bonded to the conductor layer 4 without variation.

In many cases, the outer lead portion 8 has a plating layer such as tin or gold. Since these plating layers can be distinguished from the solder layers by color, it is easy to visually judge the quality. According to this embodiment, as described above, since the low melting point alloy layer is widely spread on the surface of the outer lead portion 8, the surface shape of the region centered on the small hole 9 is observed, and the quality of the bonding state is checked. It can be determined accurately.

FIG. 6 shows another embodiment. The configuration shown here is different from the configuration of the above-described embodiment in that the outer lead portion 8 is pressed toward the conductor layer 4 using the heating tool 14, and the other configurations remain unchanged. In this case, not only the heating and the pressing of the low melting point alloy layer 5 and the periphery thereof can be achieved by a common tool, but also the bonding process at a plurality of locations can be achieved at once.

The portion shown as the heating tool 14 is merely a plate made of a good heat conductive metal such as copper, but this plate is heated by a heater (not shown). Heating tool 1
The pressing surface of the band-shaped tip of No. 4 is formed along the arrangement position of the small holes 9.

The small holes 9 need not be circular. The small hole 9a in the embodiment shown in FIGS.
Is formed in an elliptical shape with its major axis in the longitudinal direction. The major axis L of the oval small hole 9a is 1.0 mm, and the minor axis S is 0.3 mm.
(W = 0.5 mm, P = 1.2 mm). In this case, the laser light reflectance of the low melting point alloy layer 5 mainly composed of solder is larger than the laser light reflectance of the outer lead portion 8, as well as the area of directly projecting the laser light onto the low melting point alloy layer 5 is increased. Since it is low, the low melting point alloy layer 5 can be efficiently melted with a relatively low laser beam output. Further, the risk of exposing the printed circuit board to high temperatures is reduced, so that the damage can be prevented.

The outer lead portion 8 in the embodiment shown in FIG. 10 has a wide portion 15 bulging in the width direction by drawing an arc centered on the small hole 9. The radius R of the arc is, for example, 0.4 mm (W = 0.5 mm, P = 1.
2 mm, φ = 0.3 mm). With such a configuration, the bonding area between the outer lead portion 8 and the low melting point alloy layer is increased, so that the bonding strength can be increased accordingly.

In the embodiment shown in FIG. 4, the small holes 9 or the wide portions 15 are arranged in a zigzag pattern in a staggered manner. For this reason,
Interference between the wide portions 15 adjacent to each other can be eliminated. The arrangement pitch LP of the wide portions 15 based on the projecting direction of the outer lead portions 8 can be set to 1.0 mm as an example.

The arrangement for avoiding the interference is not limited to zigzag. In short, the adjacent outer lead portions 8 and 8 may have their small holes or wide portions positioned on the arrangement line that forms an acute or obtuse angle with respect to the protruding direction.

Although the outer lead portion in the above-described embodiment is of an integrated circuit type semiconductor element, it is not limited to this. In short, it can be read as the outer lead portion of the electronic component.

[0021]

As described above, according to the present invention, a part of the melted low melting point alloy layer is guided on the surface of the outer lead portion by utilizing the capillary phenomenon caused by the small hole provided in the outer lead portion of the electronic component. And a highly reliable bonding effect can be obtained. In addition, it is easy to visually judge the quality of the joint. Further, since heating and pressing of the plurality of outer lead portions and the corresponding low-melting alloy layer are performed by a common heating tool, the joining of each outer lead portion is uniform, resulting in good quality, and at a plurality of locations. Can be achieved all at once and is efficient.

[Brief description of the drawings]

FIG. 1 is a perspective view of a bonding step in one embodiment.

FIG. 2 is a perspective view of an outer lead portion in one embodiment.

FIG. 3 is a perspective view of an outer lead portion according to another embodiment.

FIG. 4 is a perspective view of a main part of the electronic component structure.

FIG. 5 is a sectional view of a main part shown in FIG. 4;

FIG. 6 is a perspective view of a joining step in another embodiment.

FIG. 7 is a perspective view of an outer lead portion according to another embodiment.

FIG. 8 is a perspective view of a main part of a joining step in another embodiment.

FIG. 9 is a perspective view of an outer lead portion according to another embodiment.

FIG. 10 is a perspective view of an outer lead portion according to another embodiment.

FIG. 11 is a perspective view of a conventional integrated circuit type semiconductor device.

FIG. 12 is a perspective view of a part of a conventional electronic component structure.

[Explanation of symbols]

 Reference Signs List 3 printed circuit board 4 conductive layer 5 low melting point alloy layer 6 semiconductor element 7 main body part 8 outer lead part 9, 9a small hole 10 presser 11 light projector 14 heating tool

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-75553 (JP, A) JP-A-62-44406 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 23/50 H01G 4/228 H01R 4/02

Claims (4)

(57) [Claims] An electronic component is placed on a printed circuit board by placing an outer lead portion of the electronic component on a low melting point alloy layer provided on a conductor layer of the printed circuit board and pressing the outer lead portion with a heating tool. In the joining method, a small hole is formed in each of the plurality of outer lead portions of the electronic component, and the plurality of outer lead portions are formed by using a heating tool having a pressing surface formed along the arrangement position of the small holes. An electronic component joining method, wherein the plurality of outer lead portions are joined onto the conductor layer by pressing all at once at a position where the small hole is formed. 2. The electronic component bonding method according to claim 1, wherein the small hole is an elliptical shape having a major axis in a longitudinal direction of the outer lead portion. 3. The electrode according to claim 1, wherein the outer lead portion has a wide portion centered on the small hole.
Child part joining method . 4. The electronic component bonding method according to claim 1, wherein the heating tool is formed of a plate made of a metal having good heat conductivity.