JP2003218508A - Adhesive for electronic component mounting and electronic component mounting structure - Google Patents

Abstract

An object of the present invention is to provide an electronic component mounting adhesive and an electronic component mounting structure capable of temporarily fixing an electronic component without deteriorating solder jointability. SOLUTION: In an electronic component mounting in which a bump 4 provided on an electronic component 3 is soldered to an electrode 2 of a substrate 1, a resin component constituting a main agent is provided outside the vicinity of the electrode 2 of the substrate 1;
An adhesive 6 containing a curing agent containing a liquid acid anhydride and curing the main agent, and an additive containing water or alcohol.
Is applied, and the electronic component 3 is temporarily fixed to the substrate 1 with the adhesive 6 until the reflow process. Even when the adhesive 6 enters the solder joint interface between the outer electrode 2 * and the bump 4 * due to heating during reflow, the liquid acid anhydride provides an active action to the adhesive 6 so that the solder 6 has a solder joint property. Is not hindered, and good solder bonding can be performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic component mounting adhesive for adhering an electronic component to a work, and an electronic component mounting structure using the adhesive.

[0002]

2. Description of the Related Art As a method of mounting an electronic component on a work such as a substrate, a method by soldering is widely used. As a method of supplying a solder material for soldering the electronic component to the work, a paste is applied to the work. There is known a method in which a striped cream solder is applied in advance by printing.
In this method, from the mounting process of mounting the electronic component on the work on which the cream solder is printed to the reflow process of heating the work to melt the solder, the electronic component is prevented from falling off or being displaced. In some cases, temporary fixing of electronic parts may be required. Conventionally, as a method for this temporary fixing, a method has been used in which a resin adhesive is spot-applied at the electronic component mounting position and the electronic component is temporarily fixed to a work by the adhesive force of this resin adhesive.

[0003]

However, the conventional resin adhesive used for the above-mentioned temporary fixing has the following problems. The first function of the resin adhesive for temporary fixing is to hold the electronic component on the work until the reflow process. Then, the resin adhesive for temporary fixing is hardened by the heating in the reflow, and after the mounting process is completed, the electronic component is fixed to the work by the hardened resin adhesive to fulfill the second function of supplementing the strength of the solder joint portion. . Therefore, it is desirable that the resin adhesive used here be supplied to a position apart from the electrode for solder bonding so as not to enter the solder bonding interface between the electronic component and the work and hinder the bondability.

However, due to the miniaturization of electronic components in recent years, it has become difficult to apply a resin adhesive only to a portion which does not enter the electrodes for solder joining when applied to a work. Therefore, there is a problem in that the resin adhesive applied for temporary fixing spreads on the surface of the work and enters the solder joint interface to deteriorate the solder joint property.

Therefore, an object of the present invention is to provide an electronic component mounting adhesive and an electronic component mounting structure which can temporarily fix an electronic component without deteriorating the solder bondability.

[0006]

An adhesive for mounting an electronic component according to claim 1 solders a connecting electrode provided on the electronic component to an electrode of a work and bonds the electronic component to the work. An adhesive for electronic component mounting used in an electronic component mounting method for mounting by
It contains a resin component that constitutes the main component of the adhesive, a curing agent that contains an acid anhydride and cures the main component, and an additive that contains water or alcohol.

According to a second aspect of the present invention, there is provided an electronic component mounting structure in which a connecting electrode provided on the electronic component is soldered to an electrode of a work and the electronic component is adhered to the work with an adhesive. That is, as the adhesive, an adhesive containing a resin component constituting the main component of the adhesive, a curing agent containing an acid anhydride for curing the main component, and an additive containing water or alcohol was used. .

According to the present invention, as an adhesive for temporarily fixing an electronic component to a work, a resin component that constitutes the main component of the adhesive, a curing agent that contains an acid anhydride and cures the main component, and water or alcohol are included. By using an adhesive containing an additive, it is possible to impart an activating effect to the adhesive and prevent a decrease in solder bondability.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. 1 is a process explanatory view of an electronic component mounting method according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of a solder joining process in the electronic component mounting method according to an embodiment of the present invention,
FIG. 3 is a process explanatory diagram of an electronic component mounting method according to an embodiment of the present invention.

In FIG. 1A, a plurality of electrodes 2 are provided on the upper surface of a substrate 1 as a work. Board 1
An adhesive 6 for temporarily fixing electronic components is applied by a dispenser 5 to both outer sides of the upper electrode 2. The adhesive 6 for temporary fixing is applied as a temporary fixing for the purpose of preventing the electronic component from falling off or being displaced during the period from the mounting of the electronic component on the substrate 1 to the solder joining in the reflow process. To be done.

The adhesive 6 comprises a resin component which constitutes the main component,
It contains a curing agent containing an acid anhydride to cure the main component, and an additive containing water or alcohol. An epoxy resin is used as the type of the resin component, and the content rate of the main agent in the adhesive 6 is set in the range of 30 to 60 wt%. A solid or liquid acid anhydride is used, and the content of the curing agent in the adhesive 6 is 30 to 6
It is in the range of 0 wt%. The additive content is 0.
It is selected in the range of 01 to 5%.

Epoxy resins include phenol novolac type, cresol novolac type and bisphenol A.
Type, bisphenol F type, glycidyl amine type, alicyclic type, halogenated, naphthalene aralkyl type epoxy resin and urethane modified epoxy resin.

Solid acid anhydrides include phthalic anhydride, maleic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, 4-methyltetrahydrophthalic anhydride, hymic acid anhydride, hettic anhydride, tetrabromophthalic anhydride, Trimellitic anhydride, pyromellitic dianhydride, and benzophenonetetracarboxylic acid anhydride are preferable, and at least one kind is used. Further, it is more preferable to use a liquid acid anhydride as the acid anhydride because the viscosity can be reduced and it becomes difficult to prevent the molten solder from spreading wet on the surface of the electrode 2.

Examples of the liquid acid anhydride include methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylhymic anhydride, trialkyltetrahydrophthalic anhydride, dodecenylsuccinic anhydride, methylbutenyltetrahydrophthalic anhydride and methyl. Endomethylenetetrahydrophthalic anhydride is preferred and at least one is used.

By using a liquid acid anhydride as a curing agent as in the above-mentioned constitution, the viscosity of the adhesive 6 can be reduced as compared with the case where a curing agent in the form of solid particles is mixed, and the adhesion can be improved. It has an effect of giving activity to the agent 6 and imparting an oxide film removing ability. Further, by adding an additive such as water, the viscosity of the adhesive 6 can be further lowered and the activating effect can be further enhanced. The initial viscosity of this adhesive 6 at 25 ° C. is 50 pas.
The following is desirable.

Next, the electronic component 3 is mounted on the substrate 1 coated with the adhesive 6. As shown in FIG. 1B, bumps 4 serving as connecting electrodes are formed on the lower surface of the electronic component 3 by soldering. The flux 7 is applied to the lower surface side of the bump 4 in advance. In the mounting operation of the electronic component 3, the electronic component 3 is not correctly aligned with the substrate 1, and the bump 4 is in a position deviated from the electrode 2 in the horizontal direction by a displacement amount d.

Then, the electronic component 3 is kept in this misaligned state.
Is lowered with respect to the substrate 1, the bumps 4 land on the electrodes 2 via the flux 7, and the vicinity of both ends of the main body of the electronic component 3 contacts the upper portion of the adhesive 6.
At this time, the electronic component 3 is mounted in a position displaced from the substrate 1, and the bump 4 is displaced from the electrode 2 by an amount d.
Only horizontally offset.

After that, the substrate 1 is sent to a reflow furnace, and as shown in FIG.
It is heated as shown in (d). As a result, the bumps 4 are melted and solder-bonded to the electrodes 2 to form solder-bonded portions 4 '. This solder joining process will be described with reference to FIG. FIG. 2 shows a process of solder-bonding the outer electrode 2 * and the bump 4 *, which are closest to the adhesive 6, among the combinations of the bump 4 and the electrode 2 to be solder-bonded (FIG. 1 (c)).

Generally, an oxide film is formed on the surface of the solder bump by exposure to the atmosphere, and when the electronic component 3 is mounted on the substrate 1, it is covered with the oxide film 4a as shown in FIG. 2 (a). The bump 4 * of the state is flux 7 on the electrode 2 *.
Landing through. At this time, the adhesive 6 applied to the outside tends to flow inward on the substrate 1, and the adhesive 6 enters the contact interface between the surface of the bump 4 * and the adhered flux 7 by this flow. In some cases (see arrow a). Then, the flow of the adhesive 6 is further promoted along with a temporary decrease in viscosity in the process of the thermosetting reaction of the adhesive 6 being heated, and as shown in FIG. 4 * Separated from the oxide film 4a on the surface.

Generally, the flux 7 is applied from the surface of the bump 4.
Is separated, the oxide film 4a remains in the solder joining process and hinders the solder joining. However, in the present embodiment, even if such a state occurs, the following description will be made. As a result, good solder joining results can be obtained. That is, the adhesive 6 has an active action because it is configured to contain a hardening agent containing a liquid acid anhydride and additives such as water and alcohol.
As shown in (c), the oxide film 4a of the bump 4 * is removed by this activating action. Then, by further heating, the bumps 4 * are melted and soldered well to the surface of the electrodes 2 * covered with the flux 7.

At this time, due to the self-alignment effect derived from the surface tension of the molten solder, the molten bump 4 *
Are attracted to the upper surface of the electrode 2 *, the positional displacement state before reflow is eliminated, and the positions of the electrode 2 * and the bump 4 * substantially coincide with each other (see FIGS. 1C and 1D). Further, variations in bump height in the height direction are also absorbed by the sinking of the solder, and the bondability is improved. Then, as the molten solder is cooled and solidified, the electronic component 3 is mounted on the substrate 1 in a state where the solder joint portion 4 ′ * is located at the correct position on the electrode 2 *, as shown in FIG. 2 (d). (See FIG. 1 (d)).

At the time of melting the solder, the adhesive 6 contains a liquid acid anhydride as a curing agent, and further contains an additive such as water or alcohol having a function of decreasing the viscosity. The viscosity of No. 6 is significantly lower than that before heating, and does not hinder the self-alignment effect. Then, after the solder joining process is completed, the adhesive 6 is completely cured by heat and the outer edge portion of the electronic component 3 is fixed to the substrate 1 to reinforce the solder joint portion 4 '* on the upper surface of the electrode 2. Functions as a resin reinforcement.

As described above, the adhesive 6 for mounting electronic components according to the present embodiment has a temporary fixing function after mounting electronic components until the reflow process, and also reinforces solder joints between the bumps 4 and the electrodes 2. Has a function of improving reliability. Further, in the solder joining process at the time of reflow, even if the adhesive 6 enters the joining interface between the electrode 2 and the bump 4, the solder joining property is not hindered and excellent solder joining can be performed. There is.

Therefore, even in the case where it is difficult to apply the adhesive to only the portion which does not enter the solder joint interface on the upper surface of the electrode like the fine pitch substrate, the adhesive 6 does not impair the solder joint property and the adhesive bond is achieved. It is possible to expand the applicable range in which the agent 6 can be used for temporary fixing.

The adhesive 6 shown in this embodiment is not limited to the purpose of temporarily fixing the electronic component 3, but may be used for the purpose of making the adhesive also serve as a sealing resin as shown in FIG. Can also be applied. That is, in this case, in FIG.
As shown in (a), the adhesive 6 is applied to the entire upper surface of the substrate 11 on which the electrode 12 is formed so as to cover the electrode 12 and face the electronic component 3. Then, similarly to the example shown in FIG. 1, the electronic component 3 having the bumps 4 formed on the lower surface is mounted on the substrate 11.

At the time of this mounting, some of the bumps 4 of the electronic component 3 land on the electrodes 12 with the adhesive 6 interposed therebetween. Then, in this state, the substrate 11 is sent to the reflow process and heated. At the time of this heating, since the adhesive 6 has an activating effect as described above, the bump 4 and the electrode 1
The bump 4 is well soldered to the electrode 12 without the need for a separate flux in soldering with 2. After the solder bonding, a sealing resin in which the adhesive 6 is thermoset is formed between the substrate 11 and the electronic component 3, and the electronic component 3 is fixed to the substrate 11 and the solder joint is sealed and protected. .

In this case, the solder (bump 4) melted by the adhesive 6 which gradually hardens due to the curing reaction.
May be prevented from spreading on the electrode 2, resulting in defective bonding. As measures against this, the following (1) to (3)
May be implemented singly or in combination with this embodiment. (1) A liquid acid anhydride is used. (2) The surface of the substrate 1 is plasma-treated before the adhesive 6 is applied to the substrate 1. (3) 1 reflow process
It is performed in an oxygen concentration atmosphere of 000 ppm or less. In particular, with respect to (2) and (3), the time for the molten solder to spread on the surface of the electrode 2 is shortened, that is, it spreads before the solder 6 is prevented from spreading by the curing reaction of the adhesive 6. Can be soldered.

[0028]

According to the present invention, as an adhesive for temporarily fixing an electronic component to a work, a resin component constituting the main component of the adhesive, a curing agent containing an acid anhydride for curing the main component, and water or alcohol. Since the adhesive containing the additive containing is used, it is possible to give an activating effect to the adhesive and inhibit the solder joint even when the adhesive enters the solder joint interface during the solder joint process. It is possible to prevent deterioration of solder joint property.

[Brief description of drawings]

FIG. 1 is a process explanatory diagram of an electronic component mounting method according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a solder joining process in the electronic component mounting method according to the embodiment of the present invention.

FIG. 3 is a process explanatory diagram of an electronic component mounting method according to an embodiment of the present invention.

[Explanation of symbols]

1 substrate 2 electrodes 3 electronic components 4 bumps 6 adhesive

Continued front page    (72) Inventor Toshikazu Matsuo             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Ken Maeda             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Mitsuru Ozono             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F-term (reference) 4J040 EC051 EC061 EC071 EC121                       EC151 EC261 EC401 HA126                       HB09 HB47 KA16 KA23 LA06                       NA19 PA20                 5E319 AA03 BB04 BB20 CC33 CD27                       GG03 GG09                 5F044 LL01 LL04

Claims (2)

[Claims] 1. An adhesive for mounting an electronic component used in an electronic component mounting method, wherein a connecting electrode provided on an electronic component is soldered to an electrode of a work, and the electronic component is mounted on the work by bonding. Which is characterized in that it contains a resin component that constitutes the main component of the adhesive, a curing agent that cures the main component containing an acid anhydride, and an additive that contains water or alcohol, for mounting electronic components. Glue. 2. An electronic component mounting structure in which a connecting electrode provided on an electronic component is soldered to an electrode of a work and the electronic component is adhered to the work with an adhesive, wherein the adhesive is A resin component that constitutes the main component of the adhesive, and a curing agent that cures the main component containing an acid anhydride,
An electronic component mounting structure, wherein an adhesive containing an additive containing water or alcohol is used.