JP2001274198A - Mounting method of electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a conductive adhesive agent, transferred onto a protuberant electrode, to be increased in amount independently of its shape in a part mounting method, through which an electronic part is mounted on a board through the intermediary of a conductive adhesive agent after a conductive adhesive agent is transferred onto a protuberant electrode formed on one surface of an electronic component. SOLUTION: A mold member 20 that is provided with a hole 21, in which the protuberant electrode 11 of an electronic component 10 is inserted and adheres to the conductive adhesive agent 3 with capability lower than the protuberant electrode 11 is prepared as a case which houses a conductive adhesive agent 30, the hole 21 is filled up with the conductive adhesive agent 30, and continuingly, the tip of the protuberant electrode 11 is inserted into the hole 21 and then pulled out, by which the conductive adhesive agent 30 is transferred to the protuberant electrode 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for transferring a conductive adhesive to a protruding electrode formed on one surface of an electronic component.
The present invention relates to a method of mounting an electronic component on a substrate via the conductive adhesive, and a mold member suitable for transferring the conductive adhesive to a protruding electrode.

[0002]

2. Description of the Related Art Conventionally, as a mounting method of this kind of electronic component, there is, for example, a flip chip mounting method. In this method, a protruding electrode is formed on one surface of an IC chip as an electronic component, a solder paste is printed on the surface of the substrate to be mounted, and then the IC chip is placed with the protruding electrode down (face down). It is mounted on top, heated to melt the solder, and connected.

In recent years, a connection method using a conductive adhesive has been adopted as an alternative to the connection using solder in flip-chip mounting. Connection using a conductive adhesive has advantages over solder connection in that Pb (lead) is not used, so that environmental problems can be addressed, cleaning can be eliminated, and costs can be reduced.

[0004] However, the conductive adhesive does not melt when heated, unlike solder, and does not have the property of being wetted by a specific metal. Therefore, the printing accuracy in flip-chip mounting is lower than that of solder connection. Also requires high precision. Therefore, when the pitch of the protruding electrodes becomes narrow, it becomes difficult to secure the printing accuracy of the conductive adhesive on the substrate, and the method of printing and supplying the conductive adhesive on the substrate side is no longer employed. become unable.

In such a case, a method of transferring the conductive adhesive to the protruding electrode side instead of supplying the conductive adhesive to the substrate side is adopted. FIG. 6 is a schematic cross-sectional view showing a conventional general mounting method employing this transfer. First, the conductive adhesive J1 is put in a container or the like, and the surface is leveled. Then, the flip chip J2 is lowered onto the horizontal surface of the conductive adhesive J1 with the protruding electrode J3 facing downward, and the tip side of the protruding electrode J3 is embedded in the conductive adhesive J1 (FIGS. 6A and 6B). )).

Subsequently, by pulling up the flip chip J2, the conductive adhesive J1 is transferred and adhered to the protruding electrode J3 (FIG. 6C). Thereafter, the tip side of the protruding electrode J3 to which the conductive adhesive J1 is attached is lowered onto the land (conductor portion) J5 of the substrate J4 (FIG. 6D), and the protruding electrode J3 and the land J5 are separated. The bonding is performed via the conductive adhesive J1. Thus, the chip J2 and the land J5 of the substrate J4 are electrically connected.

[0007]

However, according to the study of the present inventors, it has been found that the following problems occur in the mounting method by transfer as shown in FIG. That is, for example, when the adhesiveness between the protruding electrode J3 and the conductive adhesive J1 is low, or when the conductive adhesive J1 has a low viscosity, the conductive adhesive adhering to the protruding electrode J3 is used. The amount of the adhesive J1 becomes small.

As shown in FIG. 7 (a), when the substrate J4 has a variation in height due to warpage or the like, the electric contact is reduced in a portion where the contact area between the land J5 and the conductive adhesive J1 is small. Connection may be insufficient. To solve these problems, as shown in FIG. 7B, it is considered that the shape of the protruding electrode J3 is devised so that the conductive adhesive J1 is easily scooped at the time of transfer, and the transfer amount is increased. But
An extra step is required to make the shape of the projecting electrode J3 desired.

In view of the above problems, the present invention transfers a conductive adhesive to a protruding electrode formed on one side of an electronic component, and then places the electronic component on a substrate via the conductive adhesive. In a mounting method of an electronic component to be mounted, it is an object to increase an amount of a conductive adhesive transferred to a protruding electrode without depending on a shape of the protruding electrode.

[0010]

In order to achieve the above object, according to the first aspect of the present invention, a conductive adhesive (3
As a container for accommodating the protruding electrode (11) of the electronic component (10), a hole (21) into which the protruding electrode can be inserted is formed, and the inner surface of the hole has a protrusion. Mold member (2) having lower adhesion to the conductive adhesive than the electrode.
0) is prepared, the hole is filled with a conductive adhesive, and then the tip of the protruding electrode is inserted into the hole and then pulled out to transfer the conductive adhesive. I have.

According to this, when the protruding electrode is inserted into the hole filled with the conductive adhesive and then the protruding electrode is pulled out from the hole, the inner surface of the hole is more protruded than the protruding electrode. Also, since the adhesiveness with the conductive adhesive is low, most of the conductive adhesive is separated from the hole in a state of being in close contact with the protruding electrode.

Conventionally, when the protruding electrode is pulled up from the conductive adhesive, a part of the conductive adhesive in contact with the protruding electrode is torn off from the same conductive adhesive. Attaches to electrodes. In contrast, according to the present invention, the force of the conductive adhesive to stay in the hole becomes extremely weak.

Therefore, according to the present invention, it is possible to increase the transfer amount of the conductive adhesive to the protruding electrodes without depending on the shape of the protruding electrodes. As such a mold member (20), a member made of a fluorine-based resin having lower adhesion to the conductive adhesive (30) than the protruding electrode (11) is used, as in the invention of claim 2. Can be.

According to the invention of claim 3, the electronic component (1)
0) A mold member for transferring and attaching a conductive adhesive (30) to the front end side of the protruding electrode (11) formed on one surface side, the protrusion being provided at a position corresponding to the protruding electrode. The present invention is to provide a mold member in which a hole (21) into which a shape electrode can be inserted is formed, and the inner surface of the hole has lower adhesion to the conductive adhesive than the protruding electrode.

According to this, in the mounting method of the first aspect, it is possible to provide a mold member suitable for transferring the conductive adhesive to the protruding electrodes. It should be noted that reference numerals in parentheses of the above-described units are examples showing the correspondence with specific units described in the embodiments described later.

[0016]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention. FIG. 1 is a process diagram (schematic sectional view) showing a method for mounting an electronic component according to an embodiment of the present invention.
Hereinafter, this mounting method will be described in the order of steps with reference to FIG.

First, as shown in FIG.
0 and a mold member 20 are prepared. As the electronic component 10,
IC chips, flip chips and the like can be adopted. On one surface 10a side of the electronic component 10, a protruding electrode 11 made of a gold bump or the like formed by using a ball bonding method or the like.
Are formed. The protruding electrode 11 in the illustrated example has a shape having a constricted portion so that the conductive adhesive 30 is easily scooped.

The mold member 20 serves as a container for accommodating the conductive adhesive 30. The surface of the electronic component 10 facing the one surface 10a at the time of transfer is provided with the electronic component 10.
In the position corresponding to the protruding electrode 11 of FIG.
Are formed. The inner diameter of the hole 21 is larger than the outer diameter of the tip of the projecting electrode 11, and the tip of the projecting electrode 11 can be inserted into the hole 21.

The hole 21 may have a bottom (that is, a concave portion) as shown in FIG. 1 or may not have a bottom (that is, a through hole), and may be an opening into which the tip side of the protruding electrode 11 can be inserted. I just need. The surface of the mold member 20 including the inner surface of the hole 21 is covered with a release material layer 22 having lower adhesion to the conductive adhesive 30 than the protruding electrodes 11. The hole 21 is filled with a conductive adhesive 30.

Here, for example, the main body of the mold member 20 is made of a resin, a metal or the like, and the release material layer 22 is made of a fluorine-based resin or the like. Further, the conductive adhesive 30 may be made of, for example, Ag, Ag / Pd, Ag / Pt, or the like in a thermosetting resin such as epoxy.
An adhesive in which Au, Cu, Ni, or the like is mixed as a conductive filler so as to obtain conductivity by physical contact with these.

The mold member 20 forms a mold release material layer 22 by forming a hole portion 21 by, for example, cutting or drilling a body, and then applying a fluorine-based resin or the like. Thus, it can be manufactured. The conductive adhesive 30 is filled in the hole 21 of the mold member 20 manufactured as described above by a printing method using a mask or the like.

In the case where the hole 21 has a bottom, as shown in FIG. 1 (a), the hole 21 is exposed from the inner surface to the outside air in order to easily fill the conductive adhesive 30. The communicating air vent hole 23 may be formed by drilling or the like.
The air vent hole 23 is unnecessary when the conductive adhesive 30 is made of a material that is relatively easy to fill (such as a low-viscosity adhesive). In FIGS. 1B and 1C, the air vent holes 2
3 is omitted.

The release material layer 22 may be formed entirely or partially on at least the inner surface of the hole 21 on the surface of the mold member 20. Further, the main body of the mold member 20 is made of a resin (hereinafter, referred to as a resin) having the same performance as the release material layer 22.
(Referred to as a release resin). in this case,
The release material layer 22 becomes unnecessary and need not be formed.

As described above, the electronic component 10 having the protruding electrodes 11 and the mold member 20 having the holes 21 are prepared, and the holes 21 are filled with the conductive adhesive 30.
The transfer step shown in (b) and (c) is performed. That is, with the hole forming surface of the mold member 20 and one surface (projection electrode formation surface) 10 a of the electronic component 10 facing each other, the electronic component 10 is brought close to the mold member 20, and the tip side of the projection electrode 11 is Hole 21
And embedded in the conductive adhesive 30. At this time, in order to prevent the conductive adhesive 30 from adhering to the one surface 10a of the electronic component 10, the one surface 10a and the mold member 20 do not come into contact with each other.

Then, the protruding electrode 11 is pulled out from the hole 21 by separating the electronic component 10 from the mold member 20. At the time of this drawing, since the inner surface of the hole 21 has lower adhesion to the conductive adhesive 30 than the protruding electrode 11, most of the conductive adhesive 30 adheres to the protruding electrode.
Move away from the hole 21. Thus, the transfer of the conductive adhesive 30 to the protruding electrodes 11 is completed.

Next, as shown in FIG.
The one surface 10a of the substrate 0 faces the one surface 40a of the prepared substrate (circuit board) 40. Here, as the substrate 40, a ceramic substrate, a printed substrate, or the like can be employed. On one surface 40 a of the substrate 40, lands (conductor portions) 41 for connecting electronic components made of copper, silver, or the like are formed corresponding to the protruding electrodes 11 of the electronic component 10.

Then, as shown in FIG. 1E, the tip side of the protruding electrode 11 to which the conductive adhesive 30 has adhered is
0 is brought into contact with the land 41 formed on the one surface 40a side. Next, by performing a heat treatment or the like while maintaining this contact state, the conductive adhesive 30 is cured, and the protruding electrode 11 and the land 41 are bonded. Thus, the electronic component 10 is electrically connected to the land 41 of the substrate 40 via the protruding electrode 11 and the conductive adhesive 30. The above is the mounting method of the electronic component of the present embodiment.

FIG. 2 is an explanatory diagram showing the effect of the present embodiment. In FIG. 2, (a) shows the present embodiment,
(B) shows a conventional transfer state as a comparative example. Conventionally, when the protruding electrode J3 is pulled up from the conductive adhesive J1, a part of the conductive adhesive J1 in contact with the protruding electrode J3 is torn off from the same conductive adhesive J1 to form the protruding electrode J3. It adheres to the electrode J3. Therefore, the portion where the conductive adhesive J1 is torn off tends to be near the protruding electrode J3.

In contrast, in the present embodiment, the hole 21
By forming a mold release material layer 22 on the inner surface of the mold, or by forming the mold member 20 itself with the above-described mold release resin, the conductive adhesive 3
Since the force of the conductive adhesive 30 in the hole 21 is extremely weak compared to the conventional art, most of the conductive adhesive 30 in the hole 21 adheres to the protruding electrode 11 and Move away from

Therefore, according to the present embodiment, the shape of the projecting electrode 11 is a conventional general bump shape, or a shape having a wire loop as formed by a ball bonding method. Alternatively, the amount of the conductive adhesive 30 transferred to the protruding electrode 11 can be increased without depending on the shape of the protruding electrode 11.

If the volume of the hole 21 is too large and the amount of the filled conductive adhesive 30 is too large, the protruding electrode is drawn out in a manner similar to the conventional transfer. Becomes For this reason, since the above-mentioned releasing effect is not exhibited, the size of the hole 21 and the filling amount of the conductive adhesive 30 in the hole 21 are of course appropriately adjusted.

In FIG. 1B, the electronic component 10 is located on the upper side, and the mold member 20 is located on the lower side.
The positional relationship between the 0 and the mold member 20 in the upper and lower directions does not matter. Rather, contrary to FIG. 1B, when the electronic component 10 is on the lower side, more conductive adhesive 30 is supplied to the protruding electrodes 11 by the weight of the conductive adhesive 30. Can be. In this case, the conductive adhesive 30 does not fall from the hole 21 due to the adhesive force.

Further, the amount of the conductive adhesive 30 adhering to the protruding electrodes 11 needs to be determined in consideration of each parameter shown in FIG. In FIG. 3A, H is the height of the protruding electrode 11 (electrode height), D is the thickness of the land 41 (land thickness), and L is the height after the conductive adhesive 30 is attached (adhesion). Agent height) and d are the warpage of the substrate 40.

Here, the variation in electrode height H is σ1, the variation in land thickness D is σ2, the variation in adhesive height L is σ3, and the variation in substrate warp d is σ4. When the maximum value of the crush amount of the protruding electrode 11 and the conductive adhesive 30 due to the load of h is h, the adhesive height L
Needs to satisfy the following expression (1).

[0035]

(Equation 1)

Here, the last item of 20 μm is for securing a sufficient connection area between the conductive adhesive 30 and the land 41 after the electronic component 10 is mounted. At a minimum, an adhesive height L that satisfies Equation 1 is given by
The amount of the conductive adhesive 30 is adjusted. Equation 1 is derived for the following reason.

That is, as shown in FIG.
At the time of mounting 0, before the protruding electrode 11 is crushed, the gap (electrode-land gap) between the tip of the protruding electrode 11 and the land 41 which are separated by the warpage of the substrate 40 is d. Here, as shown in FIG. 3 (c), when the protruding electrode 11 is crushed by h, the electrode-land gap becomes (dh).

However, since there is the above-mentioned variation σ1 of each structure, the actual maximum value of the electrode-land gap is further increased by σ1 with respect to (dh) as shown on the right side of the above equation (1). It is the value to which the term of the route including etc is added. It is necessary to fill the electrode-land gap with the conductive adhesive 30. Therefore, the height L is determined so as to satisfy Equation 1.

Next, this embodiment will be described more specifically with reference to FIG. FIGS. 4A, 4B, and 4C are diagrams showing the cross-sectional dimensions of each member in the present embodiment. In this example, the electronic component 10 has a chip size S1 of 4 mm.
□ land 4 having a land width S3 of 0.3 mm using an IC chip having a pitch S2 of the projection-like electrodes 11 of 0.4 mm.
1 (see FIG. 4A).

The protruding electrode 11 is formed in the first stage by a normal wire bonding method using a gold wire, and is further subjected to wire bonding under the same conditions to form a two-stage having a constricted portion. The shape of the protruding electrode of the mold was used. As shown in FIG. 4B, the electrode height H at this time is 1
50 ± 15 μm, and the diameter S4 of the root portion is 100
μm, the height S5 from the root to the constriction is 70 to 90 μm
m.

Next, as shown in FIG. 4C, a mold member 20 having a plate-shaped main body and a hole 21 as a through hole formed therein was used. The material is a conductive adhesive 30
And a fluororesin having good mold release properties. Here, the hole 21
Was prepared by making a hole from the printing / injection surface side using a needle material on a resin plate. The pitch S6 of the holes 21 was 400 μm corresponding to the pitch S2 of the protruding electrodes 11.

As described above, if the amount of the conductive adhesive 30 filled is too large, the releasing effect is lost. When the maximum diameter of the portion of the protruding electrode 11 to be inserted into the hole 21 was 120 μm, the hole 2
It was found that when the inner diameter S7 of No. 1 was larger than 220 μm, the above-mentioned releasing effect was lost, and when it was smaller than 150 μm, a sufficient amount of the conductive adhesive 30 was not transferred. In addition,
The viscosity of the conductive adhesive 30 used is 1200 Pa · s
(1 rotation viscosity). Therefore, in this example, the inner diameter S7
Was set to 150 μm.

The depth S8 of the hole 21 (the plate thickness of the mold member 20 in this example) must be longer than the maximum length of the protruding electrode 11 (the maximum value of the electrode height H) by at least 30 μm. Particularly, a sufficient amount of the conductive adhesive 30 cannot be secured in the vertical direction. Therefore, in this example, the depth S8 of the hole 21 is set to 1 mm
And Further, in this example, since the hole 21 is a through hole, air can be easily removed, and the conductive adhesive 30 can be prevented from being unfilled during printing. In FIG. 4C,
50 is a saucer.

After preparing an IC chip (electronic component) 10, a substrate 40 and a mold member 20 as shown in FIG. 4, a conductive adhesive 30 is printed and injected into the hole 21 of the mold member 20. Filled. FIG. 5 is an explanatory diagram (schematic sectional view) of this filling step. The used conductive adhesive 30 used was an epoxy resin in which an Ag filler was dispersed. The conductive adhesive 30 was moved on the mold member 20 by the metal squeegee 60 and was filled in the hole 21.

Next, a component mounting machine (not shown) uses the
The surface of the C chip 10 opposite to the surface on which the projecting electrodes 11 are formed is attracted, and the projecting electrodes 11 of the IC chip 10 are
Was inserted into the hole 21. This insertion is performed by the IC chip 10
The test was performed with a predetermined appropriate insertion load (insertion distance) and insertion time so that the die itself did not come into contact with the mold member 20.

Next, the conductive adhesive 30 is applied to the protruding electrode 11.
Was mounted on the land 41 of the substrate 40 by the above-mentioned component mounting machine. In this example, the mounting load (pressurization during mounting) was 1N. And
The substrate 40 on which the IC chip 10 was mounted was placed in an oven, and the conductive adhesive 30 was cured at 150 ° C. for 10 minutes. The height L of the adhesive after the transfer in this example was 60 μm, and the connection with the land 41 of the substrate 40 was good.

[Brief description of the drawings]

FIG. 1 is a process chart showing a method for mounting an electronic component according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram for explaining an effect of increasing a transfer amount in the embodiment.

3A is a diagram showing parameters relating to the amount of conductive adhesive adhering to a protruding electrode, and FIG. 3B is a view showing the state of an electrode-land gap before the protruding electrode is crushed when an electronic component is mounted. FIG. 3C is a diagram showing a state of an electrode-land gap after a protruding electrode is crushed when an electronic component is mounted.

FIG. 4 is a diagram showing a cross-sectional dimension of each member in the embodiment.

FIG. 5 is an explanatory diagram for explaining a step of filling a hole of a mold member with a conductive adhesive.

FIG. 6 is a process diagram showing a conventional general mounting method employing a method of transferring a conductive adhesive.

FIG. 7A is a schematic cross-sectional view illustrating a state in which a variation in height due to warpage or the like has occurred in a substrate. (B) is a schematic sectional view showing a protruding electrode shape in which a conductive adhesive is easily scooped.

[Explanation of symbols]

10 electronic components (IC chip), 11 projecting electrodes, 2
0: mold member, 21: hole, 30: conductive adhesive, 40:
Substrate, 41 ... land (conductor part).

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takashi Nagasaka 1-1-1, Showa-cho, Kariya-shi, Aichi F-term in DENSO Corporation (reference) 5E319 AA03 AB05 BB11 CC03 CC61 CD25 GG01 5F044 KK01 LL07 QQ01

Claims (3)

[Claims] 1. A step of preparing an electronic component (10) having a protruding electrode (11) formed on one surface side, and attaching a conductive adhesive (30) to the tip side of the protruding electrode by transfer. Then, one surface of the electronic component is opposed to one surface of the substrate (40), and the tip side of the protruding electrode to which the conductive adhesive is attached is connected to the conductor portion ( 4
1) A method of mounting an electronic component, the method comprising: a step of electrically connecting the electronic component to the electronic component, wherein a hole (21) into which the projecting electrode can be inserted is formed at a position corresponding to the projecting electrode; A mold member (20) having an inner surface of a portion having lower adhesion to the conductive adhesive than the protruding electrode is prepared, and the conductive adhesive is filled in the hole; A method of mounting the electronic component, wherein the conductive adhesive is transferred by inserting the leading end of the conductive adhesive into the hole and then pulling out the conductive adhesive. 2. The method according to claim 1, wherein the mold member is made of a fluorine resin. 3. A mold member used for transferring and attaching a conductive adhesive (30) to a tip end of a protruding electrode (11) formed on one surface of an electronic component (10). A hole (21) into which the projecting electrode can be inserted at a position corresponding to the projecting electrode;
A mold member having lower adhesion to the conductive adhesive than the protruding electrode.