JP5337520B2 - Press-fit pin, press-fit pin connection structure, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a press-fit pin used for press-fit connection of a connector or the like in a module substrate, the press-fit pin preventing a short-circuit by welding waste scattering under a practical environment. <P>SOLUTION: On a surface of the press-fit pin 1, a first insulating resin 8 with high moisture resistance is coated, and then, a second insulating resin 9 with higher durability (for example, silicon resin) is again coated onto the first insulating resin 8. Thereafter, the press-fit pin 1 is inserted into a through-hole 5 of the circuit board 4. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a press-fit pin, a terminal connection method, and a terminal connection structure for press-fit connection of a board, a module, and a connector.

  In recent years, press-fit connection has attracted attention as a connection method for mounting components or the like on a substrate on which electrical wiring is formed. Conventionally, press-fit connection has been used in large computers as a method of connecting between boards when soldering is difficult, but (1) the connection process is easy and (2) to establish the process. In recent years, it has begun to be applied to in-vehicle modules such as ABS (Electronic Control Device) due to its small capital investment.

  An example of press-fit connection is shown in FIG. As shown in FIG. 1, the press-fit connection is performed by press-fitting a plurality of press-fit pins 1 provided on a press-fit connector 3 of a component into a plurality of through holes 5 provided on a wiring board 4. In this connection method, electrical connection is established by mechanically and metallicly connecting the pin 1 and the wiring in the through hole 5. The connecting portion 2 of the press-fit pin 1 has a spring structure with a thickness t having an outer diameter w larger than the inner diameter of the through hole and a flat portion having a length L. Therefore, after press-fitting the press-fit pin 1 into the through-hole 5, the spring force of the press-fit pin 1 works and is held in the through-hole 5 part. At the same time, the outermost surface of the press-fit pin 1 is generally plated with Sn to ensure the connectivity of the through hole 5 with Cu. Because of this connection method, unlike conventional solder connection, non-heating, normal temperature, and short-time connection is possible.

  On the other hand, when deploying press-fit connections to in-vehicle applications, in the case of ABS installed in engine rooms such as automobiles, severe operating environments such as high ambient temperature, high humidity, and vibration Must be guaranteed to work in an environment where there is a lot of heat. When the press-fit pins are connected, when the press-fit pins are pushed into the through holes, the Sn plating on the outermost surface is peeled off from the pins, and a phenomenon occurs in which plating scraps adhere to the vicinity of the through-hole insertion opening. When the plating scraps are scattered in a vibration environment, there arises a problem that they are attached to other electronic components and short-circuited. Therefore, regarding the application of the press-fit connection to the in-vehicle environment, higher reliability than ever is required, and it is an urgent need to deal with various problems.

  For example, in Patent Document 1, a coating with an adhesive material is provided on the surface of a press-fit pin and connected to a through hole.

JP 2005-216653 A

  However, in the invention described in Patent Document 1, the adhesive material deteriorates due to the severe environment in the engine room of the automobile, and there is a possibility that the plating scraps contained inside due to the vibration of the vehicle-mounted environment are scattered into the engine room. . When the plating scraps 6 scatter and adhere to other circuit parts, for example, lead parts of package parts such as a CPU, a short circuit occurs.

  The object of the present invention is to provide a highly reliable press-fit pin that can be used even in a high-temperature, high-humidity, vibration environment, and that is highly reliable by using the press-fit pin. It is to provide an electronic device.

  In order to achieve the above object, the present invention provides a press-fit pin having a surface plated with a metal, and a coating with a specific insulating resin is applied to at least a portion of the press-fit pin surface that comes into contact with a through hole. It is characterized by that.

  The present invention also relates to a press-fit pin whose surface is metal-plated, wherein a first coating with a first insulating resin is applied to at least a portion of the surface of the press-fit pin that comes into contact with the through-hole, and further on the first coating. A second coating with a second insulating resin is applied.

  In addition, the present invention is a press-fit pin having a metal plating on its surface, and at least a portion of the press-fit pin surface that is in contact with the through hole is coated with three or more types of insulating resins. It is characterized by.

  ADVANTAGE OF THE INVENTION According to this invention, the said subject can be solved and the highly reliable press fit pin and electronic device which can be used also in a real environment can be provided.

It is the schematic diagram which showed the example in the case of connecting a press fit connector to the through hole of a connection board | substrate. (a) is a stereomicrograph in the vicinity of the through hole immediately after the press-fit pin is inserted. (b) is a cross-sectional SEM photograph showing a similar region. (a) is a cross-sectional SEM photograph of a sample subjected to a temperature cycle test of −55 / 150 ° C. × 2000 cyc after press-fit connection. (b) is an enlarged photograph of a portion of (a) where the substrate is cracked. It is the figure which showed an example of preparation of the press fit pin with a double coating, and a connection process. (a) is a schematic diagram of a press-fit pin formed with a double coating. (b) is a schematic view after the press-fit pins of (a) are connected to the wiring board. It is a stereoscopic microscope photograph of the vicinity of a through hole immediately after inserting a press-fit pin with a double coating. It is a cross-sectional SEM photograph of the plating waste generation part near a through hole after a vibration test. 6 is a schematic diagram showing a method for drying the coating resin shown in Example 2. FIG. 6 is a schematic diagram of an in-vehicle module shown in Example 3. FIG.

  Embodiments of the present invention will be described with reference to the drawings.

  First, a first embodiment will be described with reference to FIGS. In the first embodiment, a press-fit pin is used in which the press-fit pin 1 is immersed in a liquid resin bath and heated and cured by hot air or a heating furnace. As the resin, acrylic resin, polyurethane resin, fluorine resin, polyolefin resin, vinyl resin, epoxy resin, polyamide resin, rubber resin, silicone resin, flux and grease are used.

  A press-fit pin according to Example 1 is shown in FIG. The press-fit pin 1 uses a phosphor bronze needle eye shape with Sn plating of 1-2 μm thickness on the outermost surface and Ni plating of 2-3 μm thickness on the base, and the shape of the connecting part 2 shown in FIG. The outer diameter is 1.2 mm (w: separation direction) x 0.65 mm (t: thickness direction), and the length L of the flat portion is 0.75 mm. The press-fit connector 3 includes three rows and 20 press-fit pins 1 in each row. This press-fit connector was immersed in a resin bath and heat-cured to form an insulating resin layer having a thickness of 1 to 100 μm on the Sn-plated press-fit pin. As the wiring substrate, a connection substrate 4 having a substrate thickness of 1.6 mm was used. Naturally, the connecting substrate 4 is provided with through-holes 5 in three rows and 20 in each row, and the diameter thereof is 1.0 mm and the interval between the through-holes is 2.5 mm.

  FIG. 2 (a) shows a stereoscopic micrograph in the vicinity of the through hole after the press-fit pin 1 is inserted, and FIG. 2 (b) is a cross-sectional SEM photograph showing a similar region. As shown in FIGS. 2 (a) and 2 (b), Sn plating scraps 6 are adhered in the vicinity of the through hole 5 on the press-fit pin 1 insertion side. This is because, as described above, in press-fit connection, a pin having an outer diameter larger than the inner diameter of the through-hole is press-fitted, so that the surface of the press-fit pin is scraped off at the through-hole insertion opening. Such plating scraps 6 are not firmly connected in the vicinity of the through-holes, and the possibility of scattering due to vibrations in the vehicle-mounted environment is sufficiently considered. When the plating scraps 6 scatter and adhere to other circuit parts, for example, lead parts of package parts such as a CPU, a short circuit occurs.

  On the other hand, FIG. 3 is a cross-sectional SEM photograph of the press-fit connected substrate 4 between the press foot pins. As shown in FIG. 3, the press-fit pin 1 is connected to the substrate 4 in a state where a large compressive stress is applied, so the glass fiber 4c of the substrate 4 peels off when used in a high temperature environment near the engine room. Then the substrate breaks. When such a substrate crack 7 exists, there is a problem that the substrate 4 absorbs moisture and migration occurs in a humid environment, resulting in a decrease in insulation resistance between the through holes 5. Therefore, it is necessary to take measures against moisture absorption of the circuit board including the press-fit contact portion. Note that migration here refers to a phenomenon in which metal ions migrate from one electrode to the other and deposit metal from the other electrode when a voltage is applied to a printed circuit board or the like under high humidity conditions. .

  The present inventors have studied to solve problems in the actual environment, such as the above-described plating scraps and substrate moisture absorption. As a result, as long as the press-fit pin 1 plated with a softer metal than the metal used for the through-hole is used, the through-hole 5 and the press-fit pin 1 rub against each other regardless of the through-hole diameter and through-hole shape. In addition, the present inventors have found that the plating is peeled off and plating scraps 6 are generated. In general, Cu is often used as the through-hole material, and Sn is often used on the outermost surface of the press-fit pin from the viewpoint of electrical connectivity. An example thereof is a stereomicrograph of the vicinity of the insertion hole of the through hole 5 immediately after the press-fit pin 1 is inserted as shown in FIG.

  FIG. 2 (b) shows that the plating scrap 6 has a length of 200 μm or more. In recent electronic devices, miniaturization and high density have been demanded, and the pitch of Cu wiring and package component leads has been reduced. Therefore, when the plating scrap 6 having such a size is scattered, a short circuit easily occurs. Therefore, even if such plating scrap 6 is generated, a technique that does not scatter is essential.

  Pre-fit connection was performed with a jig using the press-fit pin with a single coating according to this example and the wiring board 4. As a result, it was confirmed that although any of the coatings generated plating scraps 6 near the insertion hole of the through hole 5, the plating scraps 6 were covered with resin. Various reliability tests were performed on this sample. The experiments were conducted at -55 / 150 ° C x 3000cyc temperature cycle test, 150 ° C x 1000h high-temperature standing test, 85 ° C / 85% RH / 50V high-temperature high-humidity bias test, and -40/105 simulating the environment near the vehicle engine room. Four kinds of vibration tests with a temperature cycle of ° C. were performed, and holding force measurement, cross-sectional observation, and contact resistance measurement were performed.

  As a result, acrylic resin, polyurethane resin, fluorine resin, polyolefin resin, vinyl resin, epoxy resin, polyamide resin, and rubber resin are protected by the above resin and are not coated even after various tests. Reliability improved compared to the case. However, it was confirmed that the adhesiveness was lost due to exposure to a high temperature environment on the resin surface, and some cracks were generated. As for the silicone-based resin, the protection structure of the plating scrap 6 was similarly maintained, and it was confirmed that the reliability was improved. However, the silicone resin was inferior in moisture resistance, and there was concern about deterioration of insulation resistance. On the other hand, most of the flux was volatilized in a high temperature environment, and a part of the plating scrap 6 was exposed. Moreover, there was a concern about the corrosion of the connection part due to the residual flux component, and reliability could not be obtained. In addition, the grease could not be stable over a long period of time, for example, the oil component of the grease was separated in a high temperature environment.

  Next, a second embodiment will be described. In the second embodiment, as shown in FIG. 4, the press-fit pin 1 is immersed in a liquid first resin bath, heated and cured by hot air or a heating furnace, and then in the same liquid second resin bath. This is the case of using a press-fit pin that has been dipped in and heat-cured. The first resin 8 is suitably an insulating resin having moisture resistance, initial adhesiveness, low-frequency and short-time curing characteristics, and acrylic, polyurethane, fluorine, polyolefin, vinyl, epoxy, having these characteristics Polyamide type and rubber type resins were used. As the second resin 9, an insulating resin having adhesiveness after durability, heat resistance / cold resistance, and low temperature and short time curing characteristics is suitable, and a silicone resin was used.

  As the press-fit pin 1, the press-fit connector 3, and the wiring board 4, the same ones as in Example 1 were used. By applying the above process to this press-fit connector, the first insulating resin layer 8 having a thickness of 1 to 100 μm on the Sn plating of the press-fit pin, and further having a thickness of 1 to 100 μm on the first insulating resin layer 8 A second insulating resin layer 9 was formed. As the wiring substrate, a connection substrate 4 having a substrate thickness of 1.6 mm was used. Naturally, the connecting wiring board 4 is provided with three rows and 20 through holes 5 in each row, the diameter of which is 1.0 mm, and the interval between the through holes is 2.5 mm.

  As shown in FIG. 5, pre-fit connection was performed with a jig using the press-fit pins 10 with the double coating and the wiring board 4. As a result, as shown in FIG. 6, although the plating scrap 6 is generated near the insertion hole of the through hole 5, the plating scrap 6 is covered with the first resin 8, and the first resin 8 is further coated with the second resin 9. It was confirmed that it was in a form to be coated. Various reliability tests were performed on this sample. The experiments were conducted at -55 / 150 ° C x 3000cyc temperature cycle test, 150 ° C x 1000h high-temperature standing test, 85 ° C / 85% RH / 50V high-temperature high-humidity bias test, and -40/105 simulating the environment near the vehicle engine room. Four kinds of vibration tests with a temperature cycle of ° C. were performed, and holding force measurement, cross-sectional observation, and contact resistance measurement were performed. As an example of the result, the observation result of the sample after the vibration test is shown in FIG. As shown in FIG. 7, in these tests, it was confirmed that Sn plating scraps 6 existing from the beginning were covered with the first resin 8 even after the test and were not scattered around. It was confirmed that the first resin 8 was cracked due to curing, but the second resin 9 around the first resin 8 was not cracked and maintained adhesiveness. Therefore, it is considered that the plating scrap 6 did not scatter around. Moreover, no occurrence of migration was observed in the substrate portion, and it was confirmed that moisture resistance was secured.

  From these results, it was confirmed that the double coating with the first resin 8 and the second resin 9 achieves a short circuit due to the scattering of the Sn plating scraps 6 and the provision of moisture resistance to the substrate 4. The press-fit connection structure can be realized.

  Next, the case where flux and grease are used as the first resin 8 will be described. In this case, similar to Example 1, problems such as flux disappearance and corrosion, and separation of grease oil occurred. However, it was confirmed that the protective curing with the second resin 9 improved the reliability as compared with the case of Example 1.

  In the above experiment, Sn is used for the plating on the outermost surface of the press-fit pin 1. However, if the metal is softer than the through-hole material, plating scraps are always generated. The invention is applicable.

  In the above-described embodiment, a pin with a double coating is used, but multiple layers of multiple layers may be applied. For example, the adhesion strength between the first resin / third resin is improved by inserting an appropriate second resin between the first resin / third resin. Thereby, peeling between the first resin and the third resin at the time of insertion can be suppressed, and the reliability in the vibration environment can be further improved.

  In addition, for example, by using an insulating resin with an appropriate function such as oil resistance and prevention of corrosive gas permeation such as NOx as an intermediate layer, various reliability can be improved in addition to moisture resistance and vibration resistance. It becomes possible.

  In Examples 1 to 3, the resin used is a room temperature or heat curable insulating resin, but other curing methods may be used. FIG. 8 shows an example of the curing method. The insulating resin used may be UV curable. Further, for the second and subsequent resins that do not require moisture proofing, a hygroscopic curing type resin may be used. Using these techniques, the disappearance of Sn due to the compounding reaction of Sn plating and Ni plating on the surface of the press-fit pin could be prevented by not raising the curing temperature to 130 ° C. or higher.

  Finally, taking an in-vehicle module as an example of the electronic apparatus according to the present invention, this embodiment will be described with reference to FIG. As shown in FIG. 9, the in-vehicle module has a plurality of press-fit pins 1 inserted into a plurality of through-holes 5 mounted on a base substrate 11, each of which includes a sub-module 12 (a power module 12a, a coil and a capacitor. The module 12b) or the press-fit connector 3 which is an external connection terminal is electrically connected. Also for the terminal connection of such an in-vehicle module, by using the press-fit pin 10 with double coating shown in the above-mentioned embodiment, to realize an in-vehicle module with high reliability of the press-fit connection part and preventing a decrease in the service life. Can do. In particular, the present invention can be effectively applied to the connection of the submodule 12. This is because the resin coating process after connection, which is a conventional technique for preventing plating dust scattering, is not feasible due to the structure of the submodule 12 because the part to be coated is hidden after connection. An example is shown below.

  When the power module 12a having 10 pins and the LC module 12b having 4 pins were press-fit connected to the base substrate 11 to which the present invention was applied, even after the vibration test, the plating dust 6 was scattered. It was confirmed that no occurred.

  As described above, the present invention can be applied to any form and product as long as the press-fit connection is used, and the reliability can be improved.

  The present invention improves the reliability of the press-fit connection structure in a high temperature, high humidity, and vibration environment due to the effect of preventing plating dust scattering. For this reason, in-vehicle electronic devices, particularly electronic devices installed in harsh environments such as engine rooms, can be applied to any product that uses a press-fit connection between modules / boards or between boards / boards. . Furthermore, application of the press-fit connection is promoted even in a connection portion where the press-fit connection cannot be used so far.

1 Press-fit pin
2 Press-fit pin connection
3 Press-fit connector
4 Wiring board
4a Cu wiring
4b Insulating resin
4c glass fiber
5 Through hole
6 Plating scrap
7 Substrate crack
8 First insulating resin
9 Second insulating resin
10 Press-fit pins with double coating
11 Base board
12 sub-modules
12a power module
12b LC module (module with coil and capacitor)

Claims (2)

A press-fit pin with plating on the surface,
Acrylic in a zone that is in contact with at least the through hole of the press-fit pin surface, polyurethane, fluorine-based, polyolefin, vinyl, epoxy, polyamide, rubber, Ri by a silicone resin, a flux, any grease The first insulating resin coating is applied,
A press-fit pin , wherein a surface of the first insulating resin is coated with a second insulating resin with a silicone resin, and the second insulating resin is an outermost layer . An electronic device having a press-fit pin according to claim 1 Symbol placement,
An electronic device, wherein a connector and a submodule in the electronic device and separated from the wiring board are electrically connected to the wiring board via the press-fit pins.

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