JP5402410B2 - Manufacturing method of electronic device - Google Patents

Description

  The present invention relates to an electronic device manufacturing method and an electronic device in which electronic components are joined to a printed circuit board by solder.

  As is well known, electronic components such as a CPU (Central Processing Unit) are joined to a printed circuit board by soldering, and an aircraft engine electronic control unit (ECU) is printed by a similar method even in an aircraft. Bonded to the substrate. However, among electronic components, a component whose main body is ceramic and a printed circuit board made of polyimide have greatly different coefficients of thermal expansion, so that stress is generated in the solder joint between the two components according to temperature changes. And since the stress is repeatedly generated, it cannot withstand fatigue deterioration, and the solder joint is broken.

  And as invention which eliminates the fracture | rupture of the solder by such a temperature change, following patent document 1 is a power semiconductor module which used the resin insulating layer for the insulated substrate, Comprising: The thermal distortion of a solder joint part is suppressed. A power semiconductor module is disclosed. This semiconductor module is a power semiconductor module using a resin insulating layer as an insulating substrate between a conductive layer and a heat sink, and the power semiconductor element is soldered to the conductive layer via a stress buffer plate sandwiched between solder layers. The stress buffer plate has a linear expansion coefficient between the conductive layer and the power semiconductor element, and the stress buffer plate is thinner than the conductive layer.

JP 2002-231883 A

  By the way, in patent document 1 of the said prior art, the thermal distortion of solder is suppressed by providing between the solder layers the stress buffer plate which is a value between the conductive layer and the linear expansion coefficient of a power semiconductor element. However, in Patent Document 1 of the above-mentioned prior art, it is assumed that the solder breaks due to heat generated from the power semiconductor element, and the temperature environment is wide from −55 to 125 ° C. and changes rapidly like an aircraft. In such an environment, a large stress is generated at the solder joint.

  The present invention has been made in view of the above-described circumstances, and provides an electronic device manufacturing method and an electronic device capable of reducing stress generated in a solder joint under an environment where temperature change is severe. Objective.

  In order to achieve the above object, according to the present invention, as a first solving means related to an electronic device manufacturing method, an electronic device manufacturing method in which an electronic component is soldered to a printed circuit board, A means is provided that includes a solder thickness generation step of creating a thickness of the solder by placing a base material between the printed board and soldering.

  In the present invention, as a second solving means relating to a method of manufacturing an electronic device, in the first solving means, in the solder thickness generation step, the base material has solder wettability and does not melt by reflow soldering. The base material is disposed on the cream solder applied on the printed circuit board, and the lead wire of the electronic component is disposed on the base material and reflow soldering is employed.

  In the present invention, as a third solving means relating to the method of manufacturing an electronic device, in the second solving means, in the solder thickness generating step, a means is adopted in which the base material is high-temperature molded solder. The high temperature molded solder here refers to solder obtained by previously molding a solder having a melting point (generally 260 ° C. or higher) higher than the reflow soldering temperature.

  In the present invention, as a fourth solving means relating to the method of manufacturing an electronic device, in the first solving means, in the solder thickness generation step, a base material is provided between a predetermined lead wire of the electronic component and a printed board. Means for lifting the whole electronic component by arranging the solder, soldering the lead wire on which the base material is not arranged, removing the base material, and soldering the lead wire on which the base material is arranged Is adopted.

  In the present invention, as a first solving means related to the electronic device, the electronic device is an electronic device soldered to a printed circuit board, and a base material is disposed between the electronic component and the printed circuit board. Adopting the means of soldering.

  In the present invention, as a second solution means for the electronic device, in the first solution means, the solder for joining the lead wire of the electronic component and the printed board has solder wettability and is soldered. A means is adopted in which the base material that does not melt is disposed.

  In the present invention, as the third solving means relating to the electronic device, in the second solving means, a means is adopted in which the base material is high-temperature molded solder.

According to the present invention, there is provided a method of manufacturing an electronic device in which an electronic component is soldered to a printed circuit board, wherein a solder is disposed by placing a base material between the electronic component and the printed circuit board and soldering. A solder thickness generating step for producing a thickness;
In the present invention, since a thicker solder thickness is created in the above process, stress generated in the solder joint can be reduced under an environment where the temperature change is severe.

It is a schematic diagram which shows the electronic component 11 and the printed circuit board 12 in the solder thickness production | generation process of the manufacturing method of electronic device A1 which concerns on 1st Embodiment of this invention. It is the hierarchy schematic diagram before the soldering of the location where the high temperature molded solder 14 is arrange | positioned in the solder thickness production | generation process of the manufacturing method of electronic device A1 which concerns on 1st Embodiment of this invention, and after soldering. It is explanatory drawing which shows the relationship between the thickness of solder, distortion, and stress. FIG. 4 is a schematic diagram showing an electronic component 21 and a printed circuit board 22 in a solder thickness generation step of a manufacturing method of an electronic device A2 according to a second embodiment of the present invention, and a hierarchical schematic diagram of four corners of the electronic component 21 before soldering.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The present embodiment relates to an electronic device and a method for manufacturing the electronic device.
[First Embodiment]
First, an electronic device A1 according to the first embodiment and a method for manufacturing the electronic device A1 will be described.
The manufacturing method of the electronic device A1 according to the first embodiment is a method of manufacturing the electronic device A1 by soldering an electronic component 11 of a QFP (Quad Flat Package) to the printed circuit board 12, and a solder thickness generation step is performed. Prepare.

FIG. 1 is a schematic diagram showing an electronic component 11 and a printed circuit board 12 in a solder thickness generation step of the method for manufacturing the electronic device A1 according to the first embodiment.
In the solder thickness generation step, cream solder (Sn63 / Pb37, melting point 183 degrees) 13 is printed on the pads 12a on the four sides on the printed board 12 shown in FIG. In addition, the cream solder 13 has a moderate viscosity by adding a flux to the powder of eutectic solder.

  Then, after the cream solder 13 is printed, the high temperature molded solder (Pb95 / Sn5, melting point 300 degrees) 14 is disposed on the cream solder 13. The hatched portion in FIG. 1 indicates the pad 12a on which the high temperature molded solder 14 is disposed. In the solder thickness generation step, the high temperature molded solder 14 is not disposed on all the pads 12a, but is disposed on each central pad 12a among the four sides 12a on which the electronic component 11 is mounted.

And after arrange | positioning the high temperature molding solder 14 on the pad 12a, it arrange | positions so that the lead wire 11a of the center of 4 sides among the lead wires 11a of the electronic component 11 may be mounted on the high temperature molding solder 14, and the electronic component 11 And the printed circuit board 12 are reflow soldered.
FIGS. 2A and 2B are hierarchical schematic diagrams of the place where the high-temperature molded solder 14 is disposed before and after soldering in the solder thickness generation step of the manufacturing method of the electronic device A1 according to the first embodiment. 2A is a hierarchical schematic diagram before soldering, FIG. 2B is a hierarchical schematic diagram after soldering, and FIG. 2C is a high-temperature molded solder 14. It is a hierarchy schematic diagram of the location where is not arrange | positioned.

At the place where the high temperature molded solder 14 is arranged, before reflow soldering, as shown in FIG. 2A, the pads 12a, cream solder 13, high temperature molded solder 14, and lead wires 11a are stacked in this order from the bottom. Yes. When the reflow soldering is performed, the high-temperature molded solder 14 having a high melting point remains in a solid state without being dissolved. Therefore, as shown in FIG. Located in the solidified cream solder 13. And in the location where the high temperature molding solder 14 is not arrange | positioned, it becomes a hierarchy as shown to (c) of FIG. The reason why the high temperature molded solder (Pb95 / Sn5) 14 is selected is that it is higher than the melting point of the eutectic solder (Sn63 / Pb37) that is a component of the cream solder 13 and has solder wettability so that the eutectic solder and the alloy are alloyed. This is because the can be formed.
And the electronic component 11 and the printed circuit board 12 which were soldered in this way are mounted in electronic device A1.

  In the solder thickness generation step, the above-described method is used to obtain a solder thickness obtained by adding the solder components positioned above and below the high-temperature molded solder 14 to the height of the high-temperature molded solder 14 at the central lead wire 11a on the four sides of the electronic component 11. At the same time, the lead wire 11a other than the center of the four sides can also create a solder thickness obtained by adding the solder components positioned above and below the high-temperature molded solder 14 to the height of the high-temperature molded solder 14.

  When the temperature cycle test was carried out, the conventional product had a solder breakage in 32 cycles. However, in the electronic device A1 according to the first embodiment, the solder does not break even after 170 cycles or more have elapsed. That is, in the electronic device A1, the stress generated at the solder joint is reduced.

The stress generated in the solder joint will be described with reference to FIG.
As shown in FIG. 3A, when the material m1 and the material m2 expand due to a temperature rise, the solder is distorted due to the difference between the expanded lengths (thick arrows) of the material m1 and the material m2. This distortion is inversely proportional to the solder thickness Tk. That is, as the thickness of the solder increases, the strain decreases, and as the thickness of the solder decreases, the strain increases. Note that a small distortion indicates that the deformation amount from the original length is small, and a large distortion indicates that the deformation amount from the original length is large.

For example, when the thickness of the solder is thinner than (a) as shown in (b) of FIG. 3, even if the expanded lengths of the material m1 and the material m2 are the same as (a), (a The solder distortion is larger than
Since the strain and the stress are in a proportional relationship (see the following formula (1)), the stress is reduced as the strain is reduced. Therefore, the stress is reduced as the thickness of the solder is increased.
(Stress) = (Strain) × (Young's modulus) (1)

  As described above, in the method of manufacturing the electronic device A1 according to the first embodiment, in the solder thickness generation process, the high temperature molded solder 14 is disposed on the cream solder 13 applied to the pad 12a of the printed circuit board 12, and the high temperature Reflow soldering is performed in a state where the lead wire 11a of the electronic component 11 is disposed on the molded solder 14. Thereby, it is possible to create a solder thickness obtained by adding the solder components positioned above and below the high-temperature molded solder 14 to the height of the high-temperature molded solder. Thus, by increasing the thickness of the solder of the electronic device A1 by the manufacturing method of the electronic device A1, it is possible to reduce the stress generated at the solder joint in an environment where the temperature change is severe.

The first embodiment of the present invention has been described above, but the present invention is not limited to the first embodiment, and for example, the following modifications can be considered.
(1) In the solder thickness generation step of the manufacturing method of the electronic device A1 according to the first embodiment, the high-temperature molded solder 14 is disposed in the solder of the lead wire 11a at the center of the four sides of the QFP electronic component. The invention is not limited to this.
For example, the high temperature molded solder 14 may be disposed in the solder of the pads 12a at both ends of each side. That is, the high temperature molded solder 14 may be disposed at a position where the entire electronic component 11 is lifted stably.

Also, when soldering a dip-type electronic component having lead wires on two sides, the lead wires on both ends of the two sides or a little on both ends so that the entire dip-type electronic component is lifted. You may make it arrange | position high temperature molding solder to two inside lead wires.
However, since a greater stress is generated at the end of each side than at the center of each side of the electronic component, the place where the high-temperature molded solder 14 is disposed is preferably at the center of the four sides of the electronic component 11 or near the center. .

(2) In the solder thickness generation step of the method for manufacturing the electronic device A1 according to the first embodiment, the high-temperature molded solder 14 is “Pb95 / Sn5”, but the present invention is not limited to this.
The high-temperature molded solder 14 used in the solder thickness generation step is higher than the melting point of the eutectic solder (Sn63 / Pb37) that is a component of the cream solder 13 and has solder wettability. For example, Pb90 / Sn10 But the same effect can be expected.

[Second Embodiment]
Next, an electronic device A2 according to the second embodiment and a method for manufacturing the electronic device A2 will be described.
The manufacturing method of the electronic device A2 according to the second embodiment is a method of manufacturing the electronic device A2 by soldering the QFP electronic component 21 to the printed circuit board 22 as in the first embodiment. A process is provided.

  FIG. 4 is a schematic diagram showing the electronic component 21 and the printed circuit board 22 in the solder thickness generation step of the manufacturing method of the electronic device A2 according to the second embodiment, and a hierarchical schematic diagram of the four corners of the electronic component 21 before soldering. . 4A is a schematic diagram showing the printed circuit board 22, and FIG. 4B is a schematic hierarchical diagram of the four corners of the electronic component 21 before soldering.

  In the solder thickness generation step, the cream solder 23 is printed so that the cream solder (Sn63 / Pb37, melting point 183 degrees) 23 is not printed on the pads 22a (8 pads) at the four corners on the printed circuit board 22 shown in FIG. To do. Then, the Kapton sheet 24 is put on the pad 22a at the four corners where the cream solder 23 is not printed, the Kapton sheet 24 is fixed so as not to move, and the electronic component 21 is arranged thereon. At this time, as shown in FIG. 4B, at the four corners of the electronic component 21, the pads 22a, the Kapton sheet 24, and the lead wires 21a are stacked in this order from the bottom.

In this state, the electronic component 21 and the printed circuit board 22 are reflow soldered. After the soldering, the Kapton sheet 24 is removed, and the lead wires 21a at the four corners of the unsoldered electronic component 21 on which the Kapton sheet 24 is disposed are soldered by manual soldering. The reason for selecting the Kapton sheet 24 is that there is almost no change in shape due to heat in reflow soldering.
Then, the electronic component 21 and the printed board 22 soldered in this way are mounted on the electronic device A2.

  When the temperature cycle test was carried out, the conventional product had a solder breakage in 32 cycles. However, even in the electronic device A2 according to the second embodiment, as in the electronic device A1 according to the first embodiment, the solder does not break even after 170 cycles or more. That is, even in the electronic device A2, the stress generated at the solder joint is reduced.

  As described above, in the manufacturing method of the electronic device A2 according to the second embodiment, in the solder thickness generation step, the cream solder 23 is applied to the pads 22a other than the four corners, and the Kapton sheet is placed on the pads 22a at the four corners. By arranging the electronic component 21, the entire electronic component 21 is lifted. Then, reflow soldering is performed in this state. After the soldering, the Kapton sheet 24 is removed, and the lead wires 21a at the four corners of the electronic component 21 and the pads 22a are soldered. Thereby, the solder thickness corresponding to the thickness of the Kapton sheet 24 can be created. As described above, by increasing the thickness of the solder by the manufacturing method of the electronic device A2, it is possible to reduce the stress generated in the solder joint portion in an environment where the temperature change is severe.

The second embodiment of the present invention has been described above, but the present invention is not limited to the second embodiment, and for example, the following modifications can be considered.
(1) In the solder thickness generation step of the manufacturing method of the electronic device A2 according to the second embodiment, the Kapton sheet 24 is disposed under the lead wires 21a at the four corners of the electronic component 21 of the QFP. It is not limited.
For example, the Kapton sheet 24 is disposed at the center of the four-side pad 22a, and the lead wires 21a at the four corners of the electronic component 21 are soldered. Then, the Kapton sheet 24 is removed, and the central leads on the four sides of the electronic component 21 are removed. The wire 21a may be soldered.

  Further, not only the pads 22a on the four sides but also the Kapton sheet 24 is arranged on the printed circuit board 22 located under the package part of the electronic component 21, and all the lead wires 21a on the four sides are soldered at a time. It may be. That is, the kapton sheet 24 may be arranged at a position where the entire electronic component 21 is lifted stably. However, in this case, the Kapton sheet remains after soldering. Further, the Kapton sheet 24 may be disposed at positions that do not overlap the pads 22a at the four corners of the electronic component 21.

  In addition, in the case where lead wires are provided on two sides like a dip type electronic component, a Kapton sheet is arranged on the printed circuit board 22 located under the package of the electronic component, and all the two sides are arranged. The lead wire may be soldered.

(2) In the solder thickness generation step of the method for manufacturing the electronic device A2 according to the second embodiment, the Kapton sheet 24 is disposed under the electronic component 21, but the present invention is not limited to this.
As long as there is almost no shape change due to heat in reflow soldering like the Kapton sheet 24, the same effect can be expected even if another one is used instead of the Kapton sheet 24.

(3) In the solder thickness generation step of the manufacturing method of the electronic device A2 according to the second embodiment, reflow soldering is performed in a state where the Kapton sheet 24 is disposed under the electronic component 21, but the present invention is based on this. It is not limited.
Instead of reflow soldering, the lead wire 21a may be joined by soldering by a method other than reflow soldering even when the Kapton sheet 24 is disposed under the electronic component 21.

  A1, A2 ... Electronic device, 11 ... Electronic component, 11a ... Lead wire, 12 ... Printed circuit board, 12a ... Pad, 13 ... Cream solder, 14 ... High temperature molded solder, 21 ... Electronic component, 21a ... Lead wire, 22 ... Print Board, 22a ... Pad, 23 ... Cream solder, 24 ... Kapton sheet

Claims (1)

An electronic device manufacturing method in which an electronic component is soldered to a printed circuit board,
A solder thickness generating step of creating a thickness of the solder by arranging and soldering a base material between the electronic component and the printed circuit board ;
In the solder thickness generation step, the entire electronic component is lifted by placing a base material between a predetermined lead wire of the electronic component and a printed board, and the lead wire on which the base material is not disposed is soldered, After removing the base material, the lead wire on which the base material is disposed is soldered .

Images