JP2009038075A - Electronic component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an electronic component which suppresses the large growth of a whisker 15 from a plating layer 13 formed on the surface of a base material while employing a Pb-free plating material. <P>SOLUTION: The plating layer 13 is formed of the Pb-free plating material on the surface of the base material as a terminal 12. The surface is coated with a resin coating layer 14 for moisture proofing. At this time, the spring hardness of the resin coating layer 14 is 80 to 85°. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electronic component, particularly an electronic component having a resin coating layer for moisture prevention.

  In recent years, for example, electronic components such as a semiconductor device in which an IC chip is mounted on a lead frame have been required to be further reduced in size, and as a result, the distance between the terminals has been reduced to about several hundred μm. In an electronic component such as a semiconductor device, brass, copper alloy, 42 alloy, or the like is used as the base material of the terminal. However, if the base is left as it is, the terminal surface is oxidized to cause poor conduction (due to poor soldering or the like). Since there is a fear, a protective film is usually formed on the terminal surface by plating or the like. As a material for the plating layer, pure Sn or Sn alloy is mainly used.

  An alloy containing Pb has been conventionally used as a material for the plating layer. However, in recent years, Pb-free materials have been demanded from the viewpoint of reducing the environmental load. For example, Sn and Sn- It is required to use a material that does not contain Pb, such as Cu, Sn—Ag, and Sn—Bi. However, it is known that when a terminal surface of an electronic component is plated with a Pb-free material, whiskers are generated. As described above, when the distance between the terminals is as narrow as several hundred μm, the generated whisker is generated. May cause short circuit between terminals. In order to avoid this, the proposal to elucidate the cause of whisker generation and control the whisker generation itself, the whisker generated on the premise of whisker generation grows to a size that causes a short between terminals Many proposals have been made, such as proposals to suppress this.

  As an example of the latter, Patent Document 1 describes that in an electronic component that has been subjected to electrolytic plating with pure Sn or an Sn-based alloy, a resin film layer made of epoxy resin or the like is formed in the plated region. ing. Patent Document 2 describes that the surface of a Pb-free plating layer formed on a panel terminal in a liquid crystal panel is coated with an insulating resin such as an acrylic photo-curing resin. As described in Patent Documents 1 and 2, a plating layer is formed by forming a Pb-free plating layer using pure Sn or a Sn-based alloy on an appropriate base material surface and forming an appropriate resin layer on the surface. It can be expected that whisker generated from the inside can be suppressed inside the resin layer, and the whisker can be prevented from growing outward to such a size as to cause a short circuit between terminals.

JP 2005-302575 A JP-A-2005-300824

  In the conventional technology that suppresses whisker generated from the plating layer to the inside of the resin layer and suppresses outward growth, a special resin film is plated as described in Patent Documents 1 and 2 above. The number of manufacturing steps of the electronic component is increased.

  An object of the present invention is to provide an electronic component provided with a resin film on the surface of a plating layer, which can be manufactured without particularly increasing the number of manufacturing steps, and suppresses whisker growth.

  In a conventional electronic component, the entire electronic component or at least a terminal portion is coated with an insulating resin for the purpose of moisture prevention (corrosion resistance). The present inventors have found that by utilizing the resin coating layer, a resin film capable of suppressing the growth of whiskers can be formed on the surface of the plating layer without increasing the number of manufacturing steps of the electronic component. It came to make.

  That is, an electronic component according to the present invention is an electronic component having a Sn-based and / or Zn-based Pb-free plating layer on the surface of a base material and having a resin coating layer formed so as to cover the plating layer, The resin coating layer has a spring hardness of 80 ° to 85 °.

  As shown in the following examples, by setting the spring hardness of the resin coating layer to 80 ° or more, it is possible to prevent whiskers generated from the plating layer from growing through the resin coating layer to the outside. it can. However, when the spring hardness exceeds 85 °, the resin coating layer may crack depending on the shape of the electronic component. If the crack occurs, the original waterproof function that the resin coating layer should have is lost, which is not preferable. Therefore, in the present invention, the resin coating layer has a spring hardness of 80 ° to 85 °.

  In the present invention, examples of the Sn-based and / or Zn-based Pb-free material forming the plating layer include Sn-based alloys and Zn-based alloys. Pure Sn or pure Zn may be used. Sn-based alloys are preferable, and examples thereof include Sn-Cu, Sn-Ag, Sn-Bi, Sn-Zn, and Sn-In alloys. As a base material, a metal material that has been used in a conventional electronic component can be used as it is, and examples thereof include brass, a copper alloy, and 42 alloy. It selects suitably according to the kind of electronic component.

  In the present invention, the thickness of the resin coating layer is not limited for moisture prevention. It may be the same as the thickness of the resin coating layer for moisture prevention in the conventional electronic component, for example, in the range of 10 μm to 300 μm. If it is the resin coating layer of the thickness of this range, the whisker generated from the plating layer can be suppressed inside the resin coating layer.

  In the present invention, the target electronic component is also arbitrary, and examples include an electronic component including a semiconductor device, a resistor chip, a capacitor, and the like installed in the ECU. Furthermore, lead frames such as those semiconductor devices are raised. The whole of these electronic components may be covered with a resin coating layer for moisture prevention, and at least the region where the Sn-based and / or Zn-based Pb-free plating layer is formed on the surface of the base material is covered. Good. More specifically, examples of the portion covered with the resin coating layer for moisture prevention include a lead frame of an electronic component or a terminal portion thereof.

  In the present invention, as the resin for forming the resin coating layer, the resin can be used as it is for moisture prevention used in conventional electronic components, provided that the above-mentioned hardness condition is satisfied. Examples include thermosetting resins such as epoxy resins, polyolefin resins, poly-resin end resins, acrylic resins, etc. For example, the hardness of those resin coatings can be adjusted by adjusting the amount of crosslinking agent added. can do.

  In the present invention, the spring hardness is a value measured using a spring hardness (Hs) A type durometer according to JIS K6253 (ISO48).

  According to the present invention, it is possible to obtain an electronic component that can prevent whiskers from growing to the outside while adopting a Pb-free material for the plating layer without increasing the number of manufacturing steps.

  An example of the embodiment of the present invention will be described with reference to FIG. FIG. 1 shows a part of a semiconductor device 10 which is an example of an electronic component according to the present invention.

  In FIG. 1, reference numeral 11 denotes an IC package, which is mounted on a lead frame having terminals 12. The lead frame is usually a copper alloy and has a thickness of about 100 μm to 500 μm. A plating layer 13 which is a Pb-free material is formed on the surface of the base material of the terminal 15, and the plating layer is made of pure Sn or 1 to 5% of Sn—Cu, Sn—Bi, Sn—Ag alloy or the like. The plating layer 13 is usually about 5 μm to 15 μm thick.

  The entire surface of the semiconductor device 10 including the IC package 11 and the terminals 12 is covered with a resin coating layer 14 for moisture prevention having a thickness of about 10 μm to 300 μm. In the figure, for the sake of clarity, a gap is drawn between the surface of the semiconductor device 10 and the resin coating layer 14, but the two are in close contact with each other in an actual product. The resin coating layer 14 can be formed by means such as applying and drying a coating agent diluted with an organic solvent on the surface of the semiconductor device 10. The resin coating layer 14 may be formed on the entire surface of the front and back surfaces, and in some cases, it may be formed only in the region of the terminal 12 of the lead frame on which the plating layer 13 is formed.

  As described above, the hardness of the resin coating layer 14 ranges from 80 ° to 85 ° when measured using a spring hardness (Hs) A type durometer according to JIS K6253 (ISO48). . With this hardness, the whisker 15 generated from the Pb-free plating layer 13 does not penetrate through the plating layer 13 and does not jump to the outside, and is restrained inside the resin coating layer 14 as shown in the figure. Further, the resin coating layer 14 is not cracked at a location where stress is concentrated like the corner portion of the terminal 12. Therefore, the resin coating layer 14 can maintain the original moisture-proof function as it is.

  Hereinafter, the present invention will be described by way of examples.

[Example 1]
[Create sample]
Plating of 40 μm × 15 mm × 1 mm (thickness) 42 alloy (Ni 42 wt% -Fe), which is used as an IC lead frame material, with a thickness of 10 μm made of Sn-3 wt% Cu material by electrolytic plating A layer was formed as a test piece. A polyolefin-based coating agent (HumiSeal IB51 (manufactured by Chase Corp.)) is used as a coating resin for moisture prevention, diluted with an organic solvent, and the amount of crosslinking agent (triethylenetetramine) is changed as shown in Table 1. Five coating agents were prepared. The test piece was immersed in each coating agent and allowed to stand at room temperature (25 ° C.) for 3 seconds, and then the coating agent was dried at 100 ° C. Thereby, five types of samples having an average 30 μm resin coating layer on the plating layer surface were prepared. About each sample, spring hardness was measured using the spring hardness (Hs) A type durometer. The results are shown in Table 1.

[Whisker test]
The above five types of samples are considered to be one of the conditions where whiskers are most likely to occur, and a thermal cycle test in which a cycle of leaving for 30 minutes each at −40 ° C. and 80 ° C. is repeated 2000 times is performed. It was visually observed whether or not the whiskers were growing. The results are shown in Table 1.

[Example 2]
[Crack test]
The lead frame of an actual IC having a terminal portion shaped as shown in FIG. 1 (42 alloy (Ni 42 wt% -Fe) with a thickness of 0.15 mm), two 90 ° widths with a terminal width of 0.4 mm. In the same manner as in Example 1, a plating layer having a thickness of 10 μm made of Sn-3 wt% Cu material was formed by electrolytic plating in the same manner as in Example 1 to obtain a test piece. It was immersed in the same five coating agents as in Example 1, left at room temperature (25 ° C.) for 3 seconds, then pulled up, left at room temperature (25 ° C.) for 1 hour, and dried. After drying, whether the resin coating layer formed on the plating layer surface was cracked was visually observed. As shown in Table 1, no cracking was observed in samples with a spring hardness of 85 ° or less (samples 1 to 5), but in sample 5 with a spring hardness of 88 °, the terminal was bent mainly. Cracks were observed in the vicinity of the part.

[Discussion]
As shown in Table 1, whiskers penetrating the resin coating layer are generated when the spring hardness is 75 ° or less, and the spring hardness of the resin coating layer is preferably 80 ° or more from the viewpoint of whisker suppression. On the other hand, if the spring hardness exceeds 85 °, the resin coating layer of the product close to the actual machine is cracked, which is not preferable because the original function of the resin coating layer is impaired. From this, it can be seen that the condition for achieving both suppression of whisker growth and prevention of cracking of the resin coating layer is that the spring hardness is in the range of 80 ° to 85 °.

The figure which shows the semiconductor device which is an example of the electronic component by this invention in a cross section.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Semiconductor device which is an example of the electronic component by this invention, 11 ... IC package, 12 ... Lead frame terminal, 13 ... Sn system and / or Zn system Pb free plating layer, 14 ... Resin coating layer for moisture prevention, 15 ... whisker

Claims (3)

  An electronic component having a Sn-based and / or Zn-based Pb-free plating layer on a surface of a base material and having a resin coating layer formed so as to cover at least the plating layer, the resin coating layer having a spring hardness An electronic component characterized by an angle of 80 ° to 85 °.   The electronic component according to claim 1, wherein a thickness of the resin coating layer is in a range of 10 μm to 300 μm.   The electronic component according to claim 1, wherein the electronic component is a lead freeme such as a semiconductor device.

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