JPH05102339A - Method of bonding metallic heat radiation board to board for loading electronic part - Google Patents

Abstract

PURPOSE:To put the height from the surface of an outer lead to the surface of a heat radiation plate to the specified value accurately even if the accuracy of the depth of the heat radiation plate storing recess made in a multilayer board and the thickness of the heat radiation plate is bad by applying die paste on the adhesive plate of the heat radiation plate thicker than that necessary for bonding. CONSTITUTION:Die paste 12 is applied approximately 100mum on the adhesive face with a multilayer board 1 of a heat sink 6. Next, the heat sink 6 is stored in the metallic heat radiation plate storing recess 9 made in the board 1 in the condition that the adhesive face side is opposed to the bottom 9a, and then the board 1 is placed on the fixing stage 13 of a heat welding machine. Next, in the condition that a mobile stage 14 is heated to the setting temperature of die paste 12, is lowered to the position where the distance H from the surface 8 of an outer lead 8 to the distance 6a of a heat sink 6 may be a specified value, and then it is stopped for a certain time. Accordingly, the heat of the mobile stage 14 conducts to the heat sink 6 and the die paste 12 sets by heat, and the heat sink 6 is bonded to the board 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is connected to a multilayer substrate having a plurality of conductor circuits connected to an electronic component mounted on an electronic component mounting portion and a part of the conductor circuit through a through hole. The present invention relates to a method for adhering a metal radiator plate to an electronic component mounting board in which inner leads are inserted.

[0002]

2. Description of the Related Art Conventionally, electronic component mounting apparatuses using various types of electronic component mounting substrates have been proposed. In order to reduce the size of electronic devices, higher density mounting of electronic components is required, and in order to meet the demand, the electronic components are mounted on a multilayer board having a plurality of conductor circuits with inner leads inserted, There has been proposed an electronic component mounting apparatus in which a part of a circuit and the inner lead are connected via a through hole.

A device shown in FIG. 4 has been proposed as a device for efficiently dissipating heat generated from electronic components during operation. In this electronic component mounting apparatus, an electronic component 3 is mounted on an electronic component mounting portion 2 formed on a multilayer substrate 1 on which a plurality of conductor circuits (not shown) are formed, and a thin metal wire (not shown) is mounted.
A part of the conductor circuit connected to the electronic component and the inner lead 4 inserted in the multilayer substrate 1 are connected to each other through the through hole 5.
Connected through. Further, a metal heat dissipation plate (hereinafter referred to as a heat sink) 6 is disposed on the bottom of the electronic component mounting portion 2, and a surface 6a of the heat sink 6 is exposed to the outside of a sealing resin 7 that seals the whole by heat transfer molding.

As shown in FIGS. 5 and 6, a number of outer leads 8 continuous with the inner leads 4 extend from the four side surfaces of the multilayer substrate 1. Also, the multilayer substrate 1
In the central part of the metal heat sink housing recess 9 and the electronic component mounting portion 2
And the through-holes 10 constituting the above are respectively formed in a square shape.

When the heat sink 6 is bonded to the multilayer substrate 1, as shown in FIG. 7, the metal radiator plate accommodating recess 9 formed in the multilayer substrate 1 has a bottom 9a having substantially the same shape as the bottom 9a. The adhesive sheet 11 formed on is placed. Then, the heat sink 6 is placed on the upper surface of the adhesive sheet 11, and in that state, a predetermined temperature and pressure are applied to the heat sink 6 and the multilayer substrate 1 to attach the heat sink 6 to the adhesive sheet 11.
It is thermocompression bonded to the multilayer substrate 1 via.

[0006]

When the multi-layer substrate 1 is used by resin molding by transfer molding, the accuracy of the height H from the surface 8a of the outer lead 8 to the surface 6a of the heat sink 6 is important. Become. Since the thickness of the adhesive sheet 11 after thermocompression bonding is substantially constant (several tens of μm), the accuracy of the depth of the metal heat sink plate accommodating recess 9 and the thickness of the heat sink 6 formed on the multilayer substrate 1 is high. Is a major factor that influences the accuracy of H. Since the depth accuracy of the cutting process for forming the bottom portion 9a is about σ = 30 μm, the conventional bonding method has a problem that the yield decreases when the accuracy of the height H is increased.

The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to solve the problems that the depth of the metal heat sink plate accommodating recess formed in the multilayer substrate and the height of the metal heat sink plate vary. Provided is a method for adhering a metal heat sink to a board for mounting electronic parts, which can accurately set a height from an outer lead surface to a surface of the metal heat sink to a predetermined value when the metal heat sink is adhered to a multilayer board. Especially.

[0008]

In order to achieve the above object, according to the present invention, a part of a conductor circuit is provided in a multilayer board having a plurality of conductor circuits connected to electronic parts mounted in an electronic part mounting portion. In the method of bonding the metal heat sink to the electronic component mounting board in which the inner leads that are connected via the through holes are inserted, after applying the die paste to the bonding surface of the metal heat sink in a thickness greater than that required for bonding. , The bottom surface of the metal heat sink containing recess formed in the multi-layer substrate is placed on the fixing base of the pressure bonding machine with the adhesive surface of the metal heat dissipation plate coated with the die paste facing each other, The movable table is moved to a position where the distance between the surface opposite to the adhesive surface of the metal heat dissipation plate and the surface of the outer lead becomes a predetermined value, and then the die paste is thermally cured to form the metal on the multilayer substrate. Heat sink adhered Was to so that.

[0009]

Operation: First, the die paste is applied to the adhesive surface of the metal heat sink in a thickness greater than the required thickness. Next, both are placed on the fixing stand of the crimping machine with the bonding surface of the metal heat sink plate coated with the die paste facing the bottom surface of the metal heat sink plate recess formed in the multilayer substrate. Then, the movable table of the crimping machine is moved to a position where the distance between the surface of the metal heat dissipation plate opposite to the bonding surface and the surface of the outer lead becomes a predetermined value, and finally the die paste is heat-cured to form a multilayer. A metal heat sink is bonded to the substrate.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of the present invention will be described below with reference to FIGS. The same parts as those described in the related art are designated by the same reference numerals, and detailed description thereof will be omitted.

First, on the back surface of the heat sink 6, that is, on the adhesive surface side to the multi-layer substrate 1, the bottom surface 9a of the metal heat sink housing recess 9 is formed.
The die paste 12 is applied to a predetermined thickness (100 μm) by screen printing in substantially the same shape as. The thickness of the metal mask (not shown) used for the screen printing is changed according to the coating thickness of the die paste 12, and when the coating thickness of the die paste 12 is 100 μm, the thickness is 100 μm.
Use a metal mask of thickness. As the die paste 12, a solventless silver paste containing few impurities used when the electronic component 3 is bonded to the heat sink 6 is used.

The minimum thickness of the die paste 12 required for bonding the heat sink 6 and the multilayer substrate 1 is about 5 μm.
However, the thickness is set to 100 μm in consideration of the depth accuracy σ = ± 30 μm and the thickness accuracy σ = ± 10 μm of the heat sink 6 when forming the metal heat sink accommodation recess 9.

Next, the heat sink 6 coated with the die paste 12 is housed in the metal heat sink housing recess 9 formed in the multilayer substrate 1 with the adhesive surface side facing the bottom portion 9a. Then, as shown in FIG. 1, the multilayer substrate 1 in which the heat sink 6 is housed is placed on the fixing base 13 of the thermocompression bonding machine. In the thermocompression bonding machine, the stop position of the movable base 14 can be set on the basis of the surface 8a of the outer lead 8 provided on the multilayer substrate 1. The movable table 14 can be heated by a built-in heater (not shown).

Then, the movable table 14 is lowered while being heated to the curing temperature (about 180 ° C.) of the die paste 12. While the movable table 14 is descending, the lower surface of the movable table 14 contacts the surface 6a of the heat sink 6, and the movable table 14 continues to descend in this state, so that the heat sink 6 moves toward the bottom surface 9a side of the metal heat sink housing recess 9. Moving. At this time,
The heat sink 6 and the bottom surface 9a of the metal heat sink housing recess 9
The die paste 12 having a thickness of 100 μm interposed between and is crushed by the bottom surface 9a and the back surface of the heat sink 6 as the movable table 14 descends, and excess die paste 12 flows out from a position corresponding to the bottom surface 9a.

From the surface 8a of the outer lead 8 to the movable table 1
When the movable table 14 descends to a position where the distance to the lower surface of the surface 4, that is, the surface 6a of the heat sink 6, reaches a predetermined set value, the movable table 14 is stopped at that position and further stopped at that position for a certain period of time. As a result, the heat of the movable table 14 is transferred to the heat sink 6. Therefore, the die paste 12 is thermoset and the heat sink 6 is bonded to the multilayer substrate 1. Then, after a certain period of time has passed, the heat sink 6 to the multilayer substrate 1 is raised by raising the movable table 14.
Bonding is completed.

Therefore, even if the precision of the depth of the metal heat sink plate accommodating recess 9 and the thickness of the heat sink 6 is not increased, the thickness of the die paste 12 is changed to change the surface 8a of the outer lead 8 to the heat sink 6. It is possible to accurately form the height H to the surface 6a to a predetermined value A, and it is possible to improve the yield even when high accuracy is required.

Further, since the die paste 12 is formed thicker than the thickness required for bonding, when the movable table 14 is lowered to a predetermined position, excess die paste 12 is removed from the back surface of the heat sink 6 or the electronic component insertion hole 2. Adhere to the side. However, since the die paste 12 is the same as that used to bond the electronic component 3, it does not adversely affect.

Further, since the solventless die paste 12 is used, unlike the case where the conventional solvent-based adhesive sheet 11 is used, voids do not occur during heat curing. Further, since the movable base 14 that comes into contact with the heat sink 6 having good thermal conductivity is heated during thermocompression bonding, heat is applied to both the heat sink 6 and the multilayer substrate 1 so that the multilayer substrate is compared with the conventional method. 1 deterioration is prevented.

(Second Embodiment) Next, a second embodiment will be described with reference to FIG. In this embodiment, the fixing base 1 of the thermocompression bonding machine
3 side is configured to be heatable, and the heat sink 6 is the fixed base 1
3 is different from the above-described embodiment in that the pressurization and heating are performed in the state of being in contact with 3, and the positioning method of the stop position of the movable table 14.

That is, as shown in FIG.
2 so that the surface coated with 2 is on the upper side.
Also, with the multilayer substrate 1 placed on the fixed base 13, the movable base 14 is lowered to a predetermined position. The thermocompression bonding machine has a sensor for measuring the distance from the upper surface of the fixed base 13 to the surface 8a of the outer lead 8, and the movable base 14 is stopped when the distance measured by the sensor reaches a predetermined value A. It

Therefore, also in this embodiment, the multi-layer substrate 1 is designed so that the height H becomes the predetermined value A irrespective of the variation of the depth of the metal heat sink containing recess 9 and the thickness of the heat sink 6.
The heat sink 6 is accurately bonded.

The present invention is not limited to the above embodiment, and for example, a die paste 12 other than the silver paste 12 may be used, or the die paste 12 may be applied by a method other than screen printing. Further, instead of thermocompression bonding with a thermocompression bonding machine until the thermosetting of the die paste 12 is completed, the die paste 12 is removed from the thermocompression bonding machine in a semi-cured state, and the die paste 12 is heated with another heating device.
May be completely cured.

Further, in the second embodiment, the metal radiator plate accommodating recess 9 may be formed larger than the heat sink 6, and the die paste 12 flowing out may enter the gap between the metal radiator plate accommodating recess 9 and the heat sink 6.

[0024]

As described above in detail, according to the bonding method of the present invention, even if the depth of the metal heat sink containing recess formed in the multilayer substrate and the thickness of the metal heat sink are poor, When a metal heat sink is bonded to a specified position on the board via an adhesive,
It has an excellent effect that the height from the surface of the outer lead to the surface of the metal heat dissipation plate can be accurately set to a predetermined value.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a first embodiment embodying the present invention and showing a state in which a multi-layer substrate and a heat sink are mounted on a fixed base.

FIG. 2 is a side sectional view showing a state where the movable table is lowered and the heat sink is pressed from the state of FIG.

FIG. 3 is a side sectional view showing a second embodiment and showing a state in which a heat sink and a multilayer substrate are mounted on a fixed base.

FIG. 4 is a side sectional view of a transfer-molded electronic component mounting apparatus.

FIG. 5 is a plan view of a multilayer substrate.

FIG. 6 is a side sectional view of a multilayer substrate.

FIG. 7 is a side sectional view showing a state in which a heat sink is bonded to a multilayer substrate using a conventional adhesive sheet.

[Explanation of symbols]

1 ... Multilayer substrate, 6 ... Heat sink as metal heat sink,
8 ... Outer leads, 8a ... Surface as surface, 9 ... Metal heat sink containing recess, 9a ... Bottom, 12 ... Die paste, 1
3 ... Fixed base, 14 ... Movable base

Claims (1)

[Claims] 1. A multi-layer substrate (1) having a plurality of conductor circuits connected to electronic components mounted on an electronic component mounting portion (2).
In the method for adhering a metal heat dissipation plate to an electronic component mounting substrate having an inner lead (4) connected to a part of the conductor circuit through a through hole, the metal heat dissipation plate (6) is adhered. Die paste on the surface (12)
After applying a thickness greater than that required for bonding, the metal heat dissipation plate in which the die paste (12) is applied to the bottom surface (9a) of the metal heat dissipation plate accommodating recess (9) formed in the multilayer substrate (1). Both of them are installed on the fixed stand (13) of the crimping machine with the adhesive surfaces of (6) facing each other, and the movable stand (14) of the crimping machine
Is moved to a position where the distance between the surface of the metal heat dissipation plate (6) opposite to the bonding surface and the surface of the outer lead (8a) becomes a predetermined value, and then the die paste (12) is thermally cured. A method for adhering a metal heat dissipation plate to an electronic component mounting board, comprising adhering the metal heat dissipation plate (6) to the multilayer substrate (1).