JP3264146B2 - Electronic component soldering 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 soldering electronic components having bumps.

[0002]

2. Description of the Related Art A method of soldering an electronic component having a plurality of solder bumps projecting from a lower surface, such as a BGA (ball grid array), to a substrate has been performed. Hereinafter, problems of this conventional method will be described with reference to FIG.

FIGS. 4 (a) to 4 (c) are views for explaining steps of a conventional method for soldering electronic components. In FIG. 4, reference numeral 1 denotes a substrate, 2 denotes an electrode formed on the surface of the substrate 1, and 3 denotes an electronic component having a plurality of solder bumps 4 on a lower surface.

In this method, first, as shown in FIG. 4A, after the solder bumps 4 are aligned with the electrodes 2 of the substrate 1 which has been positioned, the solder bumps 4 of the electronic component 3 are connected to the electrodes 2.
Mounted on top.

The solder bumps 4 are melted and solidified by heating once by a heating means such as a reflow device (not shown) or the like at a temperature equal to or higher than the melting temperature of the solder, and then solidified on the substrate 1 by the solder bumps 4. The electronic component 3 is soldered.

[0006]

However, in the conventional soldering method, as shown in FIG. 4 (b), the solidified solder bumps 4 often have a Tyco-shaped fillet shape. When this Tyco-shaped fillet shape is obtained, the electrode 2
In the vicinity of the boundary between the solder bump 4 and the solder bump 4, the cross-sectional shape changes discontinuously and rapidly, and stress tends to concentrate near this.
Further, since the thermal expansion coefficients of the electronic component 3 and the substrate 1 are greatly different from each other, when heating is performed in a subsequent step, as shown in FIG. In addition, there is a problem that cracks 5 are generated and reliability of soldering is reduced.

It is an object of the present invention to provide a highly reliable method for soldering electronic components.

[0008]

According to a method of soldering an electronic component of the present invention, a through hole is formed in a substrate so as to be continuous with an electrode and penetrate the substrate. and between the substrate, it is interposed the height regulating member which defines the height of the electronic component to the substrate, solvent
The molten solder bumps flow into the through holes
The height of the electronic component is reduced
Stop and part of the molten solder bumps
To reduce the volume of solder bumps.
So it shall be the hourglass shape of the fillet shape of the solder bumps.

[0009]

According to the above configuration, after the solder bumps of the electronic component are mounted on the electrodes of the substrate, the solder bumps are melted and then solidified. When the solder bumps are melted, the solder bumps are placed in the through holes. Part of the solder bumps flow, and the substantial volume of the solder bumps decreases as much as the flow.

Therefore, the electronic component sinks slightly downward, and the electronic component comes into contact with the height defining member and cannot be lowered below a certain height. On the other hand, the molten solder bump flows into the through hole regardless of the height of the electronic component. As a result, the volume of the substantial solder bump existing between the electronic component and the electrode is further reduced, and the solder bump has a fillet shape of a knob shape when the volume is smaller, instead of a Tyco shape.

When this knob-shaped fillet shape is obtained,
Stress concentration is less likely to occur when heated in a later step, so that cracks can be suppressed and soldering reliability can be improved.

[0012]

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

FIGS. 1 (a) to 1 (c) are views for explaining steps of a method for soldering electronic components according to an embodiment of the present invention.
In this embodiment, the same components as those in FIG. 4 showing the conventional configuration are denoted by the same reference numerals, and the description is omitted.

First, as shown in FIG. 1, in this embodiment, a through-hole 6 which is continuous with the electrode 2 and penetrates the substrate 1 is formed. This through hole 6 is formed coaxially with the center of the electrode 2.

Reference numeral 7 denotes a spacer as a height defining member. As the height regulating member, in addition to the spacer 7,
A projection may be projected downward from the electronic component 3 itself, an upward projection may be provided on the substrate 1 itself, or a tape or the like may be attached to the substrate 1. In short, what is necessary is just to be able to hold the electronic component 3 with respect to the substrate 1 at a certain height lower than the solder bumps 4 when the electronic component 3 sinks as described later.

The electronic component 3 having the solder bumps 4 is mounted on the substrate 1 in the same manner as the conventional method of soldering electronic components.
Is placed on the substrate 1.

Next, as shown in FIG. 1B, the solder bumps 4 of the electronic component 3 are mounted on the electrodes 2. At this time, assuming that the height from the surface of the substrate 1 to the lower surface of the electronic component 3 is the original height H2, the height of the spacer 7 is slightly lower than the original height H2 as described above. It is like that. That is, when the solder bumps 4 are mounted on the electrodes 2, the lower surface of the electronic component 3 is slightly floating from the upper surface of the spacer 7.

Next, the substrate 1 is put into a reflow device (not shown) or the like, and the solder bumps 4 are melted. Then, as shown in FIG. 1C, a part of the melted solder bump 4 flows into the through hole 6, and the substantial volume of the solder bump 4 existing between the electronic component 3 and the electrode 2 is reduced. . As a result, the electronic component 3 sinks from the original height H2 and reaches the specified height H1. However, since the spacer 7 is interposed between the electronic component 3 and the substrate 1, the electronic component 3 reaches the specified height H1, and
I can't sink further. On the other hand, the molten solder bumps 4 flow into the through holes 6 regardless of the height of the electronic component 3. As a result, the substantial volume of the solder bump 4 existing between the electronic component 3 and the electrode 2 is considerably reduced, and as shown in FIG.
Has a knob-shaped fillet shape. Then, the substrate 1 is cooled, and the solder bumps 4 are solidified while keeping the knob-shaped fillet shape.

After that, the solder bump 4
Since it is in the shape of a fillet in the shape of a pin, stress concentration is unlikely to occur, cracks can be suppressed, and the reliability of soldering can be improved.

The shape of the solder bumps 4 formed on the lower surface of the electronic component 3 is not always uniform. That is, when the solder bumps 4 are formed, variations in height may occur. As a result, soldering failure of some solder bumps 4 may occur. Next, a method of inspecting a soldering state for this purpose will be described with reference to FIGS. Note that this inspection is usually performed using the solder bump 4
The cleaning is performed after the flux existing around is removed by washing.

In FIG. 2, reference numeral 10 denotes an elongated needle-shaped first conductor, and an insulating layer 11 is provided around the first conductor 10.
And only the upper end of the first conductor 10 is exposed to the outside. The outer periphery of the insulating layer 11 is formed in a cylindrical shape,
A second conductor 12 whose upper portion is obliquely cut is provided. Of course, the first conductor 10 and the second conductor 12 are electrically insulated. 13 is the first conductor 10 and the second conductor 10
This is a resistance meter that measures a resistance value between the conductor 12 and the conductor 12.

Then, the first conductor 10 is brought into contact with the lower part of the solder bump through the through hole 6 from the back side of the substrate 1, and the second conductor 12 is brought into contact with the electrode 2.
Here, in the example of FIG. 2, the solder bump 8 on the left side of FIG. 2 has good soldering, and the solder bump 9 on the right side has insufficient height, resulting in poor soldering.

In an electronic component having a solder bump such as a BGA, the solder bump is sandwiched between the electronic component and the substrate and cannot be observed from the outside. It is extremely difficult to visually judge that the soldering is defective.

Now, the inspection method of this embodiment is applied to the solder bump 8
Then, the first conductor 10 contacts the lower part of the solder bump 8 and the second conductor 12 contacts the electrode 2. Since the solder bump 8 is firmly soldered to the electrode 2, the resistance value indicated by the resistance meter 13 at this time is almost zero, and the first conductor 10 and the second conductor 12
Are in contact with each other. Based on this contact, the soldering state of the solder bump 8 is determined to be good.

On the other hand, as shown by the dashed line in FIG. 2, when the first conductor 10 is brought into contact with the lower part of the solder bump 9 and the second conductor 12 is brought into contact with the electrode 2, as indicated by the chain line in FIG. The resistance value indicated by the resistance meter 13 becomes almost infinite, and it can be confirmed that there is no contact. Thus, the solder bump 9 is determined to be defective in soldering.

In addition, a repairing method when it is determined that the soldering is defective will be described with reference to FIG. FIG.
In the example, the soldering of the solder bumps 9 is determined to be defective as described above. At this time, the conductive paste 15 is injected from the nozzle 14 through the through holes 6, and the conductive paste 15 reaches the electrodes 2 and the solder bumps 9. As the conductive paste 15, a paste that is thermoset at about 150 ° C., which is slightly lower than the melting temperature of the solder, is preferable. Further, molten solder may be used instead of conductive paste 15. In this way, it is possible to repair the solder bump 9 determined to be defective. After that, if the thermosetting conductive paste 15 is used, it is heated to a curing temperature to be cured.

[0027]

According to the method of soldering an electronic component of the present invention, a through hole is provided on a substrate, which is continuous with an electrode and penetrates the substrate.
A height defining member for defining the height of the electronic component with respect to the substrate is interposed between the electronic component and the substrate, and the molten solder bump is provided.
Electrons generated by the pump flowing into the through hole
Submersion of parts is prevented by the height regulating member, and melting
Part of the solder bumps
By reducing the volume of the solder bumps,
Since the so that to the fillet of the clutch type, and can be reliably perform soldering to form a fillet of the clutch type, by suppressing the generation of cracks due to stress concentration, highly reliable soldering It can be carried out.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is an explanatory view of a process of a method of soldering an electronic component according to an embodiment of the present invention. FIG. 1B is an explanatory view of a process of a soldering method of an electronic component according to an embodiment of the invention. Process explanatory drawing of the soldering method of the electronic component in one Example

FIG. 2 is a process explanatory view of an inspection method of a soldering state according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram showing steps of a repair method according to an embodiment of the present invention.

FIG. 4A is a process explanatory view of a conventional electronic component soldering method. FIG. 4B is a process explanatory view of a conventional electronic component soldering method. FIG. 4C is a process explanatory view of a conventional electronic component soldering method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Electrode 3 Electronic component 4 Solder bump 6 Through hole 7 Spacer

Claims (3)

(57) [Claims] An electronic component is mounted by mounting a solder bump protruding from a lower surface of an electronic component on an electrode formed on a surface of a substrate, and melting and solidifying the solder bump. A method of soldering an electronic component to the substrate, wherein the substrate is provided with a through hole that is continuous with the electrodes and penetrates the substrate, and when melting at least the solder bumps, A height defining member for defining the height of the electronic component with respect to the substrate is interposed between the component and the substrate, and the molten solder bump flows through the through hole.
Sinking of electronic components caused by
Prevent some solder bumps from being blocked by the specified members.
The solder bumps
Fillet-shaped solder bumps are reduced by reducing the volume
Soldering method of the electronic component, wherein Jo and to Rukoto. 2. The method according to claim 1, wherein the height defining member is a spacer mounted on an upper surface of the substrate. Wherein said contacting the solder bump from the rear side of the front Stories substrate with respect to the first conductor through the through hole, said second conductor being insulated from said first conductor The method according to claim 1, wherein the first conductor and the second conductor are contacted with an electrode, and the contact between the first conductor and the second conductor is inspected .
Soldering only way of electronic components.