JP3726782B2 - Electronic device mounting method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electronic component mounting method in which an electronic component is bonded onto one surface of a substrate through a bonding material that is used for bonding by being solidified from a paste state such as solder or conductive adhesive.
[0002]
[Prior art]
As this type of electronic component, a flip chip, a CSP (chip size package), a ceramic component, a molded component, or the like is used. And such an electronic component is mounted on one surface of a board | substrate via joining materials, such as a solder and a conductive adhesive, and an electronic component and a board | substrate are joined by solidifying this joining material from a paste state.
[0003]
FIG. 5 is a diagram showing a conventional general electronic component mounting method. 5, (a), (b), (c), and (e) are plan views seen from above the substrate, and (d) and (f) are along the direction perpendicular to the paper surface of (c) and (e), respectively. It is a schematic sectional drawing.
[0004]
In this conventional mounting method, first, the bonding material 30 is supplied to the electrode land 21 formed on one surface of the substrate 20 (FIGS. 5A and 5B). Subsequently, the electronic component 10 is mounted on one surface of the substrate 20, and the component electrode 11 of the electronic component 10 and the electrode land 21 of the substrate 20 are brought into contact via the bonding material 30 (FIGS. 5C and 5D). ).
[0005]
After that, when the bonding material 30 is solder, it is solidified after reflowing, and when it is a conductive adhesive, it is cured, so that the component electrode 11 of the electronic component 10 and the electrode land 21 of the substrate 20 are electrically and mechanically connected. (FIGS. 5E and 5F). Thus, the electronic component mounting structure is completed.
[0006]
As described above, in both the case of solder and the conductive adhesive, the bonding material 30 is used for bonding by being solidified from the paste state once. In addition, the paste state in the case of solder is a molten state by reflow.
[0007]
[Problems to be solved by the invention]
However, in the conventional mounting method described above, the thickness of the bonding material 30 under the component electrode 11 is reduced. This is because when the bonding material 30 is solder, the solder gets wet above the component electrode 11 during reflow, and accordingly, the amount of solder under the component electrode 11 is reduced accordingly. In the case of a conductive adhesive, This is because the conductive adhesive is pressed when the component 10 is mounted.
[0008]
Under a temperature cycle environment, a stress is generated in the connection portion by the bonding material 30 due to the difference in thermal expansion coefficient between the substrate 20 and the electronic component 10. At this time, if the bonding material 30 is thin, there is a problem that it is difficult to alleviate this difference in thermal expansion coefficient, and the stress increases and the connection reliability is significantly deteriorated.
[0009]
In order to solve such problems, conventionally, an insulating layer is interposed under an electronic component as described in JP-A-4-171790, or described in JP-A-5-67858. Thus, a method has been proposed in which a double-sided tape is interposed under the electronic component to support the electronic component and ensure the thickness of the bonding material.
[0010]
However, in this conventional method, another member such as an insulating layer or a double-sided tape is disposed between the electronic component and the substrate. For this reason, depending on the material of this separate member, the adhesion decreases due to the deterioration of the separate member in a temperature cycle environment, the adverse effect on the component connection caused by the difference in thermal expansion coefficient between the substrate and the electronic component, There are concerns about various inappropriate problems such as deterioration of electrical insulation due to corrosion.
[0011]
In addition, when the durability cannot be satisfied only by the connecting portion made of the bonding material, a structure is adopted in which an underfill (reinforcing resin) is filled between the electronic component and the substrate to reinforce the connection strength. Even if such a structure is adopted, since the distance between the electronic component and the substrate becomes narrower as the bonding material becomes thinner, problems such as a decrease in underfill injection and generation of voids occur.
[0012]
In view of the above problems, the present invention can increase the thickness of the bonding material and appropriately connect it when mounting the electronic component on one surface of the substrate through the bonding material used for bonding by solidifying from the paste state. The purpose is to do.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, in the inventions according to claims 1 to 4 , the electronic component (10) is attached to the substrate (20) via the bonding material (30) that is used for bonding by solidifying from the paste state. In the electronic component mounting method for joining on one surface, a joining material is disposed on one surface of the substrate, and spacers (40, 50 ) are disposed on a portion of the substrate other than the placement portion of the joining material. In the state where the electronic component is mounted on one surface of the substrate via the spacer and the bonding material, the bonding material is solidified from the paste state so that the space between the electronic component and the substrate is secured by the spacer. And after that, the spacer is removed.
[0014]
According to this, in the state where the electronic component is mounted on the substrate via the paste-like bonding material, the electronic component is supported by the spacer even if the electronic component sinks, so that the distance between the electronic component and the substrate, The height of the electronic component is secured.
[0015]
In addition, since the spacer is removed after joining with the joining material, various problems caused by the separate members such as the insulating layer and the double-sided tape are eliminated. Therefore, according to the present invention, the thickness of the bonding material can be increased, and the connection by the bonding material can be appropriately made possible.
[0016]
Further, in the invention according to claim 1, as a spacer, a substrate (20) resin film formed by curing was applied onto one surface of (40), the resin film supports the electronic component The part has a projecting part (42) facing under the electronic component, and the projecting parts facing each other are not connected to each other, and the spacer is removed by peeling the resin film. Features.
[0017]
The invention according to claim 4 is characterized in that a jig (50) made of a material having a thermal expansion coefficient larger than that of the electronic component (10) is used as the spacer.
[0020]
In addition, the code | symbol in the bracket | parenthesis of each said means is an example which shows a corresponding relationship with the specific means as described in embodiment mentioned later.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments shown in the drawings will be described below. FIG. 1 is a schematic sectional view showing a mounting structure of an electronic component according to the first embodiment of the present invention. The electronic component 10 is mounted and mounted on one surface of the substrate 20.
[0022]
As the electronic component 10 of the present embodiment, a flip chip, a CSP (chip size package), a ceramic component, a molded component, or the like can be used. In the illustrated example, the electronic component 10 is shown as a diode molded with a resin such as an epoxy resin, and component electrodes 11 are provided at both ends of the resin molded portion 10a.
[0023]
The component electrode 11 extends from both ends of the resin mold portion 10a toward the substrate 20, and the tip thereof is bent so as to have a surface 11a facing an electrode land 21 of the substrate 20 described later. . As the material of the component electrode 11, a material obtained by performing Sn plating or solder plating on the surface of a base material such as 42 alloy or Cu can be used.
[0024]
The substrate 20 may be a ceramic substrate such as alumina or aluminum nitride, a wiring substrate such as a printed circuit board, or a lead frame. In this example, an alumina substrate is employed.
[0025]
An electrode land 21 corresponding to the component electrode 11 of the electronic component 10 is formed on one surface of the substrate 20. The electrode land 11 is made of Au, Ag, Cu or the like using a plating method, a thick film printing method, or the like.
[0026]
The electronic component 10 is mounted on one surface of the substrate 20, and the component electrode 11 of the electronic component 10 and the electrode land 21 of the substrate 20 are electrically connected via a bonding material 30 made of solder or a conductive adhesive. • Mechanically connected. Thus, the electronic component 10 and the substrate 20 are electrically connected via the component electrode 11, the bonding material 30, and the electrode land 21.
[0027]
Here, as the solder, Pb-free solder such as Sn—Ag solder, Sn—Ag—Cu solder, or Pb-containing eutectic solder such as Sn—Pd solder can be used. The conductive adhesive is a resin in which a conductive filler is contained.
[0028]
As is well known, solder is reflowed once to a paste (molten state) and then solidified, and the conductive adhesive is cured from the paste state and solidified to be joined. Is what you do.
[0029]
Next, an electronic component mounting method for forming the electronic component mounting structure shown in FIG. 1 will be described. FIG. 2 is a process diagram showing the present mounting method. 2, (a), (b), (c), and (e) are plan views viewed from one surface of the substrate 20, and (d) and (f) are directions perpendicular to the paper surface of (c) and (e), respectively. FIG. 2 is a schematic cross-sectional view taken along a line, that is, a cross-sectional view corresponding to FIG.
[0030]
FIGS. 2A and 2B also show a set of electrode lands 21 ′ adjacent to the set of electrode lands 21 on which the electronic component 10 shown in FIG. 1 is mounted. Each electrode land 21, 21 'has a planar rectangular shape.
[0031]
First, as shown in FIG. 2A, a substrate 20 having electrode lands 21 and 21 ′ formed on one surface is prepared. 2B, the bonding material 30 is arranged on the electrode lands 21 and 21 ′ on one surface of the substrate 20, and the resin film 40 as a spacer is arranged on the arrangement portion of the bonding material 30, that is, the electrode. It arrange | positions in parts other than land 21 and 21 '. In FIG. 2, the resin film 40 is hatched for identification.
[0032]
Here, the solder or conductive adhesive used as the bonding material 30 can be supplied by a printing method, and the supply thickness can be set to, for example, about 50 to 300 μm.
[0033]
The resin film 40 is formed by applying the resin film 40 on one surface of the substrate 20 and then curing it. This resin film 40 can be easily peeled off from one surface of the substrate 20 using tweezers or the like, and is actually peeled off and removed from the substrate 20 after connecting components described later.
[0034]
Specifically, the resin film 40 can be made of vinyl resin, silicon resin, fluorine resin, epoxy resin, acrylic resin, polyamide resin or the like, and the application method to the substrate 20 includes printing, dispensing, stamping, spraying, and the like. The method can be adopted.
[0035]
Further, the thickness of the resin film 40, that is, the height from one surface of the substrate 20 to the surface of the resin film 40 is preferably lower than the height of the supplied bonding material 30. Accordingly, the component electrode 11 and the bonding material 30 can be reliably brought into contact with each other when the electronic component 10 is mounted as a post process. The thickness of the resin film 40 can be set to about 30 to 200 μm, for example.
[0036]
Also, the pattern of the resin film 40 is preferably formed by connecting all the target electronic components in the substrate 20 so that it can be peeled off once when peeling off later. For example, in FIG. 2B, the resin film 40 is connected between the adjacent electrode lands 21 and 21 ′.
[0037]
After arranging the bonding material 30 and the resin film (spacer) 40 in this way, as shown in FIGS. 2C and 2D, electrons are placed on one surface of the substrate 20 via the resin film 40 and the bonding material 30. The component 10 is mounted. That is, the electronic component 10 is aligned and mounted on one surface of the substrate 20, and the component electrode 11 of the electronic component 10 and the bonding material 30 on the electrode land 21 of the substrate 20 are brought into contact with each other.
[0038]
Here, as shown in FIG. 2C, the resin film 40 includes a component peripheral portion 41 located around the electronic component 10, and a protruding portion 42 that protrudes from the component peripheral portion 41 and enters under the electronic component 10. It is composed of The protrusion 42 is a part that supports the electronic component 10.
[0039]
And the protrusion part 42 of this resin film 40 becomes a shape which is cut | disconnected when it peels later and does not remain | survive on the board | substrate 20, an arc-shaped gentle shape in this example. For example, if the projecting portions 42 facing each other under the electronic component 10 are connected to each other, or projecting in an angular shape like a triangle, they are likely to be cut off and remain on the substrate 20.
[0040]
Further, the width W of the protruding portion 42 shown in FIG. 2C is widened to such an extent that the electronic component 10 can be properly supported without being tilted and can be secured so as not to be cut off at the time of peeling. Further, the entry length L of the protrusion 42 is so long that the electronic component 10 can be sufficiently floated, and is short enough to be pulled out from below the electronic component 10 during peeling.
[0041]
Next, as shown in FIGS. 2 (e) and 2 (f), the bonding material with the resin film (spacer) 40 and the bonding material 30 interposed between the substrate 20 and the electronic component 10 mounted thereon. 30 is solidified from the paste state. That is, when the bonding material 30 is solder, the solder is cooled and solidified by reflowing, and when it is a conductive adhesive, it is cured by heat treatment or the like.
[0042]
Here, when the bonding material 30 is solder, the solder becomes a paste at the time of reflow and wets above the component electrode 11 and the electronic component 10 tends to sink, but is supported by the resin film 40. The electronic component 10 can maintain the height. In the case of the conductive adhesive, the electronic component 10 tends to sink when the electronic component 10 is mounted on the paste-like conductive adhesive. However, the electronic component 10 is still supported by the support of the resin film 40. The height can be maintained.
[0043]
As described above, in this mounting method, the bonding with the bonding material 30 can be performed while the interval between the electronic component 10 and the substrate 20 is secured by the resin film 40 as the spacer.
[0044]
Thus, after the electronic component 10 and the substrate 20 are electrically and mechanically bonded via the bonding material 30, the resin film 40 is peeled off from the substrate 20 using tweezers or the like and removed from the substrate 20. Thus, the electronic component mounting structure shown in FIG. 1 is formed.
[0045]
As described above, according to the mounting method of the present embodiment, in a state where the electronic component 10 is mounted on the substrate 20 via the paste bonding material 30, the electronic component 10 is used as a spacer even if the electronic component 10 sinks. Therefore, the distance between the electronic component 10 and the substrate 20, that is, the height of the electronic component 10 is secured.
[0046]
In addition, since the resin film 40 is removed after the bonding with the bonding material 30, various problems that are caused by another member such as the insulating layer and the double-sided tape are eliminated. Therefore, according to this mounting method, the thickness of the bonding material 30 can be increased, and the connection by the bonding material 30 can be appropriately performed.
[0047]
Incidentally, in the above example, an alumina substrate having a thermal expansion coefficient of about 7.5 ppm is used as the substrate 20, and a molded diode having a thermal expansion coefficient of about 18 ppm is used as the electronic component 10. Thus, when the thermal expansion coefficient difference of both 10 and 20 is large, in the conventional mounting method, a joining material will become thin and a crack will generate | occur | produce in a connection part in a temperature cycle environment.
[0048]
In this embodiment, when the resin film 40 is formed, if the wire bonding land on one surface of the substrate 20 is also covered with the resin film 40, the wire bonding land is oxidized, contaminated, and solder is scattered during reflow. It is also possible to prevent this.
[0049]
(Second Embodiment)
FIG. 3 is a diagram showing a method for mounting an electronic component according to the second embodiment of the present invention. In this embodiment, a jig 50 made of a material having a thermal expansion coefficient larger than that of the electronic component 10 is used as the spacer instead of the above-described resin film.
[0050]
The mounting method of this embodiment prepares the board | substrate 20 with which electrode land 21 and 21 'was formed in the whole surface similarly to the said 1st Embodiment. 3A, the bonding material 30 is disposed on the electrode lands 21 and 21 ′ on one surface of the substrate 20, and the jig 50 serving as a spacer is disposed on the arrangement portion of the bonding material 30, that is, the electrode. It arrange | positions in parts other than land 21 and 21 '.
[0051]
As the material of the jig 50, as described above, the coefficient of thermal expansion is larger than that of the electronic component 10, the reflow temperature is used when the bonding material 30 is solder, and the curing temperature is used when the bonding adhesive is used. It is desirable that the material be able to withstand solder, and that the solder does not wet.
[0052]
Examples of the material of the jig 50 include an electronic component 10 (in this example, about 18 ppm) such as aluminum or a metal having a thermal expansion coefficient of 23 ppm, a metal such as lead or a resin having a thermal expansion coefficient of 29 ppm, or a resin. A material larger than the mold diode) can be used.
[0053]
Then, as shown in FIG. 3B, the electronic component 10 is mounted on one surface of the substrate 20 via a jig 50 as a spacer and a bonding material 30. In this state, the bonding material 30 is solidified from a paste state. Let As a result, the jig 50 is used to perform bonding with the bonding material 30 while ensuring the distance between the electronic component 10 and the substrate 20. Thereafter, the jig 50 is extracted and removed.
[0054]
For example, in the case of solder connection, the jig 50 expands due to the reflow temperature, and shrinks when the solder adheres and the temperature decreases after reflow. At this time, since the jig 50 has a larger thermal expansion coefficient than the electronic component 10, a gap is formed between the electronic component 10 and the jig 50, and the jig 50 can be easily removed.
[0055]
Thus, also by the mounting method using the jig 50 of the present embodiment, the thickness of the bonding material 30 can be increased, and the connection by the bonding material 30 can be appropriately performed.
[0056]
(Third embodiment)
FIG. 4 is a diagram showing a method for mounting an electronic component according to the third embodiment of the present invention. In the present embodiment, instead of the resin film or jig described above, a paste-like resin 60 is used as the spacer, and the removal is performed by cleaning.
[0057]
The mounting method of this embodiment prepares the board | substrate 20 with which electrode land 21 and 21 'was formed in the whole surface similarly to the said 1st Embodiment. Then, as shown in FIG. 4, the bonding material 30 is disposed on the electrode lands 21 and 21 ′ on one surface of the substrate 20, and the paste-like resin 60 as a spacer is disposed on the bonding material 30, that is, the electrode land. It arrange | positions in parts other than 21 and 21 '.
[0058]
As the paste-like resin 60, a flux made of a resin such as pinewood can be used. In particular, it can be arranged by applying a flux containing a filler made of resin or ceramic of a size to be raised or a high viscosity flux on the substrate 20. Here, in FIG. 4, a filler 60 a is shown in the resin 60.
[0059]
Then, the bonding material 30 is solidified from the paste state in a state where the electronic component 10 is mounted on one surface of the substrate 20 via the paste-like resin 60 as a spacer and the bonding material 30. Thereby, the bonding with the bonding material 30 is performed while the interval between the electronic component 10 and the substrate 20 is secured by the resin 60.
[0060]
Thereafter, the paste-like resin 60 can be removed using a cleaning liquid such as a glycol ether-based cleaning agent. Here, when the bonding material 30 is solder, the paste-like resin 60 can also be removed in the cleaning after the solder connection.
[0061]
Thus, also by the mounting method using the paste-like resin 60 of the present embodiment, the thickness of the bonding material 30 can be increased, and connection by the bonding material 30 can be appropriately performed.
[0062]
(Other embodiments)
In the above embodiment, an underfill may be filled between the electronic component 10 and the substrate 20. The increase in the thickness of the bonding material 30 also increases the distance between the electronic component 10 and the substrate 20 and facilitates filling with underfill.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a mounting structure for an electronic component according to a first embodiment of the present invention.
FIG. 2 is a process diagram showing a mounting method for making the mounting structure shown in FIG. 1;
FIG. 3 is a diagram showing a method for mounting an electronic component according to a second embodiment of the present invention.
FIG. 4 is a diagram illustrating a method for mounting an electronic component according to a third embodiment of the present invention.
FIG. 5 is a diagram showing a conventional general electronic component mounting method;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Electronic component, 20 ... Board | substrate, 30 ... Bonding material, 40 ... Resin film, 50 ... Jig,
60: Paste-like resin.

Claims (4)

In the electronic component mounting method in which the electronic component (10) is bonded onto one surface of the substrate (20) via the bonding material (30) that is used for bonding by solidifying from the paste state.
The bonding material is arranged on one surface of the substrate, and a spacer ( 40 ) is arranged on a portion of the one surface of the substrate other than the arrangement portion of the bonding material,
In a state where the electronic component is mounted on one surface of the substrate via the spacer and the bonding material, the bonding material is solidified from a paste state, thereby ensuring a space between the electronic component and the substrate by the spacer. While joining with the joining material,
Thereafter, the electronic component mounting method for removing the spacer ,
As the spacer, a resin film (40) formed by applying and curing on one surface of the substrate (20) is used, and the resin film has a portion that supports the electronic component under the electronic component. It has a projecting part (42) facing each other, and the projecting parts facing each other are not connected to each other.
A method of mounting an electronic component, wherein the spacer is removed by peeling off the resin film . The method of mounting an electronic component according to claim 1, wherein the protrusion has an arcuate shape. The electronic component according to claim 1, wherein a wire bonding land is formed on one surface of the substrate, and the wire bonding land is covered with the resin film when the resin film is formed. How to implement In the electronic component mounting method in which the electronic component (10) is bonded onto one surface of the substrate (20) via the bonding material (30) that is used for bonding by solidifying from the paste state.
The bonding material is disposed on one surface of the substrate, and the spacer (50) is disposed on a portion of the one surface of the substrate other than the placement portion of the bonding material,
In a state where the electronic component is mounted on one surface of the substrate via the spacer and the bonding material, the bonding material is solidified from a paste state, thereby ensuring a space between the electronic component and the substrate by the spacer. While joining with the joining material,
Thereafter, the electronic component mounting method for removing the spacer,
Examples spacers, mounting method of the electronic component you characterized by using a jig coefficient of thermal expansion is from the larger material than the electronic components (10) (50).

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