Front end structure and contact pin

Abstract

The invention relates to a front end structure and a contact pin. The contact pin comprises the front end structure. The tip structure according to the present invention has an apex for conduction confirmation, the conduction confirmation is performed by contact with the apex, and the tip structure comprises: a base material which is made of an iron alloy having a Cr content of 3 mass% or more and has an edge; and a conductive layer covering the base material, wherein the minimum radius of curvature of the apex is 5 [mu] m or less.

Description

Technical Field

[0001] The invention relates to a front end structure and a contact pin comprising the front end structure. Background Art

[0002] When inspecting electrical components such as IC packages, quality control is performed by checking continuity. For example, Patent Document 1 discloses an electrical connection inspection device for making electrical contact with an inspection object to check electrical connection.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent No. 4045084 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] A contact pin is a component used in inspection devices for checking continuity. The contact pin has a tip that is brought into contact with the object being inspected to check continuity. Specifically, the tip of the contact pin has a vertex that contacts the solder ball of an IC chip to check continuity.

[0008] In the past, beryllium copper (BeCu) and carbon tool steel were used as the base material for the front end of the contact needle. When using these BeCu and carbon tool steel materials as the base material, an edge is formed on the BeCu and carbon tool steel materials, and the area containing the edge is first nickel-plated and then gold-plated to form a vertex. At this time, since BeCu and carbon tool steel materials are not corrosion-resistant materials, oxidation may develop inside. Therefore, as a pretreatment for electroplating, a strong chemical polishing is required to remove the part where oxidation has progressed. However, if a strong chemical polishing is performed, the base material will be corroded and the curvature radius of the edge will increase to about 10μm. If the curvature radius of the edge becomes larger, it becomes difficult for the edge covered by the electroplating, that is, the vertex of the front end, to be deeply embedded in the solder ball, and a stable conduction test cannot be performed.

[0009] In addition, palladium alloys are also known as the base material for the front end of the contact pin. When a palladium alloy is used as the base material, there is no need to implement electroplating or chemical polishing. Therefore, when a palladium alloy is used as the base material, since the edge formed on the base material can be directly used as the vertex for contact, the radius of curvature of the vertex can be reduced. However, palladium easily forms an alloy with the tin in the solder ball and wears out. Therefore, if the vertex of the contact pin made of palladium alloy is repeatedly brought into contact with the solder ball, the radius of curvature of the vertex becomes large, and it is impossible to stably perform a continuity test.

[0010] An object of the present invention is to provide a tip structure having a small curvature radius at the apex and capable of maintaining the small curvature radius at the apex, and a contact pin having the tip structure.

[0011] Solutions to the Problem

[0012] The present invention relates to the following front end structure and a contact pin having the front end structure.

[0013] [1] A front end structure having a vertex for conducting confirmation, wherein the conducting confirmation is performed by contacting the vertex, the front end structure comprising: a base material made of an iron alloy having a Cr content of 3% by mass or more and having an edge; and a conductive layer covering the base material, wherein the minimum curvature radius of the vertex is 5 μm or less.

[0014] [2] The front-end structure as described in [1], wherein the conductive layer contains at least one metal selected from gold, silver, tin and platinum group metals.

[0015] [3] The front-end structure as described in [1] or [2], wherein the conductive layer includes two or more layers.

[0016] [4] The front-end structure according to [2] or [3], wherein the conductive layer further comprises at least one metal selected from palladium, cobalt, and nickel,

[0017] [5] The front end structure according to any one of [1] to [4], further comprising a nickel layer between the base material and the conductive layer.

[0018] [6] The front end structure as described in any one of [1] to [5], wherein the Vickers hardness of the base material is 400 HV or higher.

[0019] [7] The front end structure according to any one of [1] to [6], wherein the Vickers hardness of the conductive layer is 1000 HV or less.

[0020] [8] A contact pin having the front end structure described in any one of [1] to [7].

[0021] Effects of the Invention

[0022] According to the present invention, it is possible to provide a tip structure having a small curvature radius at the apex and capable of maintaining the small curvature radius at the apex, and a contact pin having the tip structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 FIG. 1 is a diagram showing a contact pin.

[0024] Figure 2 This is a partial cross-sectional view of the tip structure of the contact pin.

[0025] Figure 3A : is a graph showing the results of the wear resistance test of the embodiment, Figure 3B It is a graph showing the results of a wear resistance test of a comparative example.

[0026] Description of Reference Numerals

[0027] 1: IC chip;

[0028] 2: Solder balls;

[0029] 10: contact pin;

[0030] 11: front-end structure;

[0031] 12: parent material;

[0032] 12a: edge;

[0033] 13: conductive layer;

[0034] 14: Vertex;

[0035] 15: Force-applying component (spring). DETAILED DESCRIPTION

[0036] [Contact pin]

[0037] Figure 1 1 is a diagram showing a contact pin 10. Figure 1 As shown, the contact pin 10 has a front end structure 11 . Figure 2 1 is a partial cross-sectional view of the front end structure 11. Figure 2 As shown, the front end structure 11 has a vertex 14 for conducting confirmation. The front end structure 11 has a base material 12 made of an iron alloy (e.g., stainless steel) having a Cr content of 3% by mass or more and a conductive layer 13 covering the base material 12 (edge ​​12a). Here, the minimum curvature radius of the vertex 14 is 5 μm or less, and more preferably, the minimum curvature radius of the vertex 14 is 4 μm or less. If the minimum curvature radius of the vertex 14 is 5 μm or less, the vertex 14 will easily be deeply nested in the solder ball 2, and the conduction confirmation can be performed stably. The minimum curvature radius of the vertex 14 can be measured by a laser microscope.

[0038] It should be noted that the term "apex" herein includes not only a configuration formed by the conductive layer 13 but also a configuration in which, for example, the conductive layer 13 is worn away and the base material 12 (edge ​​12a) is exposed from the conductive layer 13. In other words, the "apex" refers to the portion of the contact pin that contacts the solder ball 2 of the IC chip 1.

[0039] The number of vertices 14 may be one or more. In this embodiment, the tip structure 11 and the contact pin 10 have a plurality of vertices 14 .

[0040] like Figure 1 As shown, a contact pin 10 having a tip structure 11 as described above can easily be embedded deeply into the solder ball 2 of an IC chip 1, for example, enabling stable continuity verification. It should be noted that the contact pin 10 has the tip structure 11 as one end and another end located on the opposite side. The two ends are electrically connected, and the length between the two ends is changed by the expansion and contraction of a biasing member (spring) 15. The contact pin 10 can be supported by a support (socket) for use.

[0041] Next, the base material 12 and the conductive layer 13 included in the tip structure 11 of the contact pin 10 will be described in detail.

[0042] (Base Material)

[0043] The base material 12 is made of an iron alloy having a Cr content of 3% by mass or more, and is preferably made of stainless steel, for example. In this embodiment, the base material 12 has an edge 12 a and forms a vertex 14 together with the conductive layer 13 .

[0044] The stainless steel in this specification refers to the stainless steel defined in Japanese Industrial Standard JIS G0203 4.3.8, that is, stainless steel is steel having a Cr (chromium) content of 10.5% by mass or more and a carbon content of 1.2% by mass or less.

[0045] In the present invention, the type of stainless steel is not particularly limited, and examples of the type of stainless steel include austenitic stainless steel and martensitic stainless steel.

[0046] The iron alloy of the base material 12 may have a Cr content of 3% by mass or greater, preferably 10.5% by mass or greater, and more preferably 13 to 15% by mass. Furthermore, the iron alloy of the base material 12 may have a carbon content of 1.2% by mass or less, and preferably 0.1% by mass or greater.

[0047] The base material 12, made of an iron alloy having a Cr content of 3% by mass or greater, has a passivation film on its surface, and oxidation does not progress into the interior of the base material 12. Therefore, when the surface of the base material 12 is coated with the conductive layer 13 by, for example, electroplating, there is no need for strong chemical polishing as a pretreatment. Therefore, by using the base material 12 made of an iron alloy having a Cr content of 3% by mass or greater, the radius of curvature of the edge 12a can be made smaller, and even when coated with the conductive layer 13, the radius of curvature of the vertex 14 can be kept small.

[0048] After the conductive layer 13 is formed on the surface, in order to make the conduction of the base material 12 made of the iron alloy with a Cr content of 3% by mass or more good, it is preferred that there is no passivation film on the surface of the base material. The passivation film is thinly present on the surface of the untreated base material 12 made of the iron alloy with a Cr content of 3% by mass or more. Therefore, as a pretreatment when covering with the conductive layer 13, it is not necessary to perform a surface treatment such as a strong chemical polishing, but it is preferred to perform a surface treatment such as a weaker chemical polishing to the extent that the passivation film can be removed. It should be noted that the surface treatment (such as chemical polishing) can be performed as needed, or no surface treatment is required.

[0049] The radius of curvature of edge 12a formed on base material 12 can be appropriately adjusted so that, when edge 12a is covered by conductive layer 13, the minimum radius of curvature of vertex 14 (conductive layer 13 covering edge 12a) is 5 μm or less. Therefore, the minimum radius of curvature of edge 12a is preferably less than 5 μm, and more preferably less than 4 μm. The minimum radius of curvature of edge 12a can be measured using a laser microscope.

[0050] The number of edges 12a included in the base material 12 may be one or more. In the present embodiment, the number of edges 12a included in the base material 12 is more than one.

[0051] The base material 12 made of an iron alloy containing 3% by mass or more Cr preferably has a Vickers hardness of 400 HV or more, more preferably 500 HV or more. A Vickers hardness of 400 HV or more can suppress wear of the edge 12a of the base material 12.

[0052] The base material 12 made of an iron alloy having a Cr content of 3% by mass or more may or may not be quenched. Quenching can be used to achieve a desired Vickers hardness for the base material 12 made of an iron alloy having a Cr content of 3% by mass or more. In the case of quenching the base material 12, the above-mentioned Vickers hardness of the base material 12 (400 HV or more) refers to the Vickers hardness after quenching. Therefore, the Vickers hardness of the base material 12 before quenching may also be lower than 400 HV. The Vickers hardness of the base material 12 can be measured in accordance with Japanese Industrial Standard JIS Z 2244: 2009.

[0053] Iron alloys with a Cr content of 3% by mass or greater, if containing silicon, become hard and difficult to work, making it difficult to form the edge 12a. Therefore, iron alloys with a Cr content of 3% by mass or greater preferably do not contain silicon. Specifically, the silicon content of an iron alloy with a Cr content of 3% by mass or greater is preferably 1% by mass or less.

[0054] (Conductive layer)

[0055] The conductive layer 13 is a layer covering the base material 12 (edge ​​12a). The conductive layer 13 plays the role of reducing the resistance of the front end structure 11 (contact needle 10). Preferably, the conductive layer 13 covers at least the edge 12a. In this embodiment, the conductive layer 13 covers the entire base material 12 having the edge 12a. The minimum radius of curvature of the conductive layer 13 (vertex 14) covering the edge 12a is 5 μm or less, and more preferably 4 μm or less. As a result, the conductive layer 13 (vertex 14) covering the edge 12a can be easily deeply nested into the solder ball 2, and the conduction can be stably confirmed. The minimum radius of curvature of the conductive layer 13 (vertex 14) can be measured by a laser microscope.

[0056] The material constituting the conductive layer 13 is not particularly limited as long as it has conductivity to function as an electrical contact. Specifically, examples of the conductive layer 13 include a layer comprising at least one metal selected from gold (Au), silver (Ag), tin (Sn), platinum group metals (platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru), osmium (Os)), cobalt (Co), nickel (Ni), and bismuth (Bi).

[0057] The conductive layer 13 may also be an alloy layer containing two or more of the above elements. For example, it may be an alloy layer selected from Au-Co, Au-Ni, Au-Ag, Au-Sn, Pd-Co, Pd-Ni, Pd-Ag, Rh-Ru, Pt-Ir, Pt-Rh, Sn-Ag, Sn-Cu, and Sn-Bi.

[0058] Preferably, the conductive layer 13 is a layer containing a metal selected from gold (Au), silver (Ag), tin (Sn) and platinum group metals (platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru), osmium (Os)), a layer containing an alloy of palladium and cobalt (PdCo) or a layer containing an alloy of palladium and nickel (PdNi).

[0059] In addition, the conductive layer 13 can also be formed by stacking multiple layers and can include two or more layers. In the case of a laminate, the layer on the vertex 14 side that contacts the electrical component is the surface conductive layer, and the layer on the base material 12 side is the intermediate conductive layer. As the surface conductive layer, the layers described above as the conductive layer can be cited. In addition, as the intermediate conductive layer, a layer containing at least one metal selected from gold and palladium can be cited.

[0060] The conductive layer 13 can directly cover or indirectly cover the edge 12a of the base material 12 made of an iron alloy with a Cr content of 3% by mass or more. In the case where the conductive layer 13 indirectly covers the edge 12a of the base material 12 made of an iron alloy with a Cr content of 3% by mass or more, preferably, a nickel layer is present between the edge 12a of the base material 12 and the conductive layer 13. The nickel layer can be used to suppress the conductive layer 13 from peeling off from the base material 12. More specifically, the nickel layer is formed by performing electroplating while removing the passivation film of the iron alloy with a Cr content of 3% by mass or more (nickel plating while decomposing the passivation film by nickel primer (Wood's Nickel Strike)). Moreover, by providing the nickel layer, electroplating can be performed more easily than, for example, electroplating the conductive layer directly on the iron alloy.

[0061] The conductive layer 13 can be applied to the base material 12 (edge ​​12a) by, for example, electroplating, vapor deposition, sputtering, etc. Preferably, the base material 12 (edge ​​12a) is applied by electroplating. The electroplating method is not particularly limited. Examples of electroplating include electrolytic plating and electroless plating. When the base material 12 (edge ​​12a) is covered with the conductive layer 13 by electroplating, the base material 12 having the edge 12a does not need to be subjected to chemical polishing as a pretreatment.

[0062] The Vickers hardness of the conductive layer 13 is preferably 1000 HV or less. A Vickers hardness of 1000 HV or less prevents the conductive layer 13 from becoming brittle, and prevents the conductive layer 13 from cracking and peeling off from the base material 12 due to slight deformation of the base material 12. The Vickers hardness of the conductive layer 13 can be measured in accordance with Japanese Industrial Standard JIS Z2244:2009.

[0063] The thickness of the conductive layer 13 is preferably 0.01 μm or more from the viewpoint of ensuring sufficient conductivity, and is preferably 5 μm or less from the viewpoint of not increasing the curvature radius.

[0064] (Effect)

[0065] According to the tip structure 11 of this embodiment, the base material 12, made of an iron alloy containing 3% by mass or more Cr, has an edge 12a covered by a conductive layer 13. This reduces the radius of curvature of the vertex 14 to 5 μm or less, thereby stabilizing the contact resistance. Furthermore, since iron alloys containing 3% by mass or more Cr are less expensive than, for example, palladium alloys, the manufacturing costs of the tip structure 11 and the contact pin 10 having the tip structure 11 can be reduced.

[0066] Example

[0067] [Wear resistance test]

[0068] Wear resistance tests were conducted on the apex of contact pins from Examples and Comparative Examples. The Example contact pins used a stainless steel base material with a tip structure in which the base material, having an edge, was directly plated with gold. The minimum radius of curvature of the gold plating layer (apex) was 5 μm or less.

[0069] On the other hand, a contact pin used as a comparative example had a BeCu base material and a tip structure in which the base material having an edge was first chemically polished, then electroplated with nickel, and finally electroplated with gold. The minimum curvature radius of the gold plating layer (apex) was 10 μm.

[0070] The resistance value of each contact pin tip structure was measured when it was brought into contact with a solder ball 5,000 times. It should be noted that a new solder ball was used in each contact pin tip structure. Figure 3A The graphs show the measurement results of the examples. Figure 3B The measurement results of the comparative example are shown in the graph.

[0071] Depend on Figure 3A 、 Figure 3B As can be seen, the resistance value is lower in the Example, while the resistance value is higher in the Comparative Example. Furthermore, the fluctuation in the resistance value is smaller in the Example, while it is larger in the Comparative Example. This is presumably because the minimum radius of curvature of the gold layer (apex) in the Example is smaller than that in the Comparative Example, allowing the apex to nest more deeply into the solder ball.

[0072] In addition, by Figure 3A As can be seen, even after 5000 contacts in this example, the resistance value remained low. This is believed to indicate that the apex remains intact, the minimum radius of curvature remains small, and wear resistance is high. Specifically, it is believed that the alloying between the tin in the solder ball and the gold-coated stainless steel base material is minimal, thus suppressing wear. Furthermore, it is believed that the stainless steel base material is not worn by mechanical forces.

[0073] Industrial Applicability

[0074] According to the present invention, the increase in the curvature radius of the vertex can be suppressed, and stable continuity confirmation can be performed over a long period of time. Therefore, it is expected that the yield of the electrical components to be inspected can be improved.

Claims

1. A front-end structure having a vertex for conducting confirmation, wherein the conducting confirmation is performed by contacting the vertex, wherein the front-end structure is characterized by comprising: a base material made of an iron alloy having a Cr content of 3% by mass or more and having an edge; as well as a conductive layer covering the base material, The minimum curvature radius of the apex is 5 μm or less.

2. The front-end structure according to claim 1, wherein: The conductive layer includes at least one metal selected from gold, silver, tin and platinum group metals.

3. The front-end structure according to claim 1, wherein: The conductive layer includes two or more layers.

4. The front-end structure according to claim 2, wherein: The conductive layer further includes at least one metal selected from palladium, cobalt, and nickel.

5. The front-end structure according to claim 1, wherein: A nickel layer is further provided between the base material and the conductive layer.

6. The front-end structure according to claim 1, wherein: The Vickers hardness of the base material is 400 HV or higher.

7. The front-end structure according to claim 1, wherein: The conductive layer has a Vickers hardness of 1000 HV or less.

8. A contact pin, characterized in that: A front end structure according to any one of claims 1 to 7.

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