Electrical contact, method for attaching the electrical contact to a circuit board, and method for removing the electrical contact from a circuit board.

Abstract

Regarding electrical contacts used to electrically measure IC chips on a wafer, these contacts, which connect to the side of the IC chip terminals by sandwiching the side of the IC chip terminals between multiple conductive pillars connected to a base, can make electrical contact with densely arranged IC chip terminals without damaging the top surface of the IC chip terminals. However, replacing damaged electrical contacts is difficult. [Solution] The base region, surrounded by multiple conductive pillars connected to the base, has an Au layer. By closely attaching a probe with its tip coated with Au or the like to the Au layer of a damaged electrical contact, an Au solid-phase bond is formed, allowing for easy removal.

Description

Technical Field

[0001] The present invention relates to an electrical contact.

Background Art

[0002] During the electrical measurement inspection of an IC chip formed on a semiconductor wafer, an electrical contact contacts the IC chip terminal and electrical measurement is performed. The IC chip terminals contacted by the electrical contact include, for example, a columnar Cu post or a Cu post with a solder layer formed hemispherically at the tip. During electrical measurement, it is desired that the electrical contact does not damage the upper surface of the IC chip terminal (Cu post or solder layer formed at the tip of the Cu post) for improving the reliability of subsequent processes. Patent Document 1 and Patent Document 2 satisfy this requirement and can contact and electrically connect only on the side surface without damaging the upper surface of these IC chip terminals during electrical measurement.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0004]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

[0005] The electrical contacts described in Patent Documents 1 and 2 have a structure comprising a base and multiple conductive pillars connected to the base, allowing for electrical contact only on the sides without damaging the top surface of densely arranged IC chip terminals. However, damage to the electrical contacts can occur due to foreign matter adhering to the IC chip terminals during contact or overcurrent during electrical measurement. When the electrical contacts described in Patent Documents 1 and 2 are mounted at high density, it is difficult to remove and replace damaged electrical contacts.

[0006] This invention was proposed in consideration of these circumstances, and relates to an electrical contact that electrically connects to an IC chip terminal by sandwiching the side surface of the IC chip terminal with multiple conductive pillars connected to a base. The objective is to provide an electrical contact that allows for easy removal of damaged electrical contacts from among electrical contacts densely mounted on a circuit board and replacement with normal electrical contacts. [Means for solving the problem]

[0007] The present invention relates to an electrical contact that electrically connects to an IC chip terminal by sandwiching the side surface of the IC chip terminal between multiple conductive pillars connected to a base, and has an Au layer formed in the region surrounded by the multiple conductive pillars of the base.

[0008] With respect to an electrical contact that electrically connects to an IC chip terminal by sandwiching the side surface of the IC chip terminal with multiple conductive pillars connected to a base, the method is characterized in that a probe with its tip coated with Au or the like is brought into close contact with the Au layer formed on the base of a damaged electrical contact on a circuit board, thereby solid-phase bonding with the Au layer formed on the base of the electrical contact and removing it from the circuit board. [Effects of the Invention]

[0009] The present invention relates to an electrical contact that electrically connects to an IC chip terminal by sandwiching the side surface of the IC chip terminal between multiple conductive pillars connected to a base. When the electrical contact is damaged during electrical measurement and inspection of a semiconductor IC due to foreign matter abnormally adhering to the IC chip terminal or abnormal overcurrent during electrical measurement, the damaged electrical contact can be easily removed and replaced with a new, normal electrical contact without affecting surrounding normal electrical contacts. [Brief explanation of the drawing]

[0010] [Figure 1] This is a perspective view showing an electrical contact according to a first embodiment of the present invention. [Figure 2] This is a conceptual diagram showing the electrical contact of the present invention electrically connected to an IC chip terminal. [Figure 3] This is a conceptual diagram showing the electrical contacts of the present invention mounted on IC chip terminals arranged at high density. [Figure 4] This is a simplified conceptual diagram of the arrangement of electrical contacts according to the present invention. [Figure 5] This is a simplified conceptual diagram of the arrangement of electrical contacts of the present invention, including a damaged electrical contact. [Figure 6] This is a simplified conceptual diagram showing a probe being inserted into a damaged electrical contact in the arrangement of electrical contacts of the present invention. [Figure 7] This is a simplified conceptual diagram showing how to remove a damaged electrical contact from the arrangement of electrical contacts of the present invention by connecting a probe to it. [Figure 8] This is a simplified conceptual diagram showing an embodiment of bonding the electrical contact of the present invention to a circuit board. [Figure 9] This is a perspective view showing an electrical contact according to a second embodiment of the present invention. [Figure 10] This is a perspective view showing an electrical contact according to a third embodiment of the present invention. [Modes for carrying out the invention]

[0011] The first embodiment of the present invention is shown in FIG. 1. The electrical contact 1 is composed of a pedestal 2 and two conductive pillars 3 connected to the pedestal 2, and has an Au layer 4 (FIG. 1b) formed in a region A (FIG. 1a) of the pedestal 2 surrounded by the two conductive pillars 3. Further, the position of the region A when the electrical contact 1 is viewed from below is shown in FIG. 1a (bottom). The conductive pillar 3 contacts and electrically connects to, for example, a columnar Cu post or an IC chip terminal having a solder layer formed in a hemispherical shape at the tip of the Cu post so as to sandwich the side surface of the IC chip terminal.

[0012] FIG. 2 shows a conceptual diagram of a state where the electrical contact 1 contacts and electrically connects to an IC chip terminal 5 on an IC chip 6. The conductive pillar 3 contacts and electrically connects to sandwich the side surface of the IC chip terminal 5.

[0013] FIG. 3 shows an embodiment in which the electrical contacts 1 are arranged corresponding to the grid-like arrangement (area array type) of the IC chip terminals 5. The electrical contacts 1 are adhered to predetermined positions on a circuit board 7 formed corresponding to the grid-like arrangement of the IC chip terminals 5 and are electrically connected to the IC chip terminals 5 (not shown).

[0014] The arrangement of the electrical contacts 1 in FIG. 3 is briefly shown in FIG. 4. Usually, the electrical contacts 1 are adhered to predetermined positions on the circuit board 7 via a conductive adhesive layer 8. The conductive adhesive layer 8 can use a conductive low-melting-point metal such as solder.

[0015] When the electrical contact 1 contacts the corresponding IC chip terminal 5 in the arrangement of the electrical contact 1 shown in FIG. 4 and an electrical measurement is performed, if it is damaged due to foreign matter abnormally adhering to the IC chip terminal 5 or abnormal overcurrent during the electrical measurement, as shown in FIG. 5, a damaged electrical contact 1' is generated, and the electrical measurement of the IC chip becomes impossible.

[0016] To separate the damaged electrical contact 1' from the circuit board 7, a removal probe 9 is inserted into the damaged electrical contact 1' as shown in Figure 6. The tip 10 of the removal probe 9 has a coating (not shown) that easily forms solid-state bonds with an Au layer 4, such as Au, and it adheres closely to and forms solid-state bonds with the Au layer 4 formed in region A of the base 2 of the damaged electrical contact 1'.

[0017] The history of solid-phase bonding between Au and Au is ancient, as can be seen from gold ornaments found as grave goods in ancient sites (for example, the Shinzawa Senzuka Tumulus Cluster).

[0018] Non-patent document 1 shows that solid-state bonding between Au-Au materials is easily achieved even at room temperature in air. Non-patent document 2 shows that solid-state bonding is further improved by applying ultrasound (output 160 μW) with heating to 190°C and a load of 0.58 N during Au-Au bonding.

[0019] If the Au film thickness of Au layer 4 is too thin, the Au-Au junction strength deteriorates. The Au-Au junction strength improves when the Au film thickness of Au layer 4 reaches 500 Å or higher. Therefore, it is desirable for the Au film thickness of Au layer 4 to be 500 Å or higher, and even 1000 Å or higher.

[0020] After bringing the tip 10 of the removal probe 9, which has an Au coating, into close contact with the Au layer 4 of the damaged electrical contact 1', the tip 10 of the removal probe 9 is heated to melt the conductive adhesive layer 8, and when the damaged electrical contact 1' is separated from the circuit board 7, the solid-state bond between the Au coating of the tip 10 of the removal probe 9 and the Au layer 4 is simultaneously heated and strengthened, and as shown in Figure 7, the damaged electrical contact 1' can be easily separated from the circuit board 7.

[0021] Ultrasound can be applied to further strengthen the solid-phase bonding between the Au coating on the tip 10 of the removal probe 9 and the Au layer 4.

[0022] Figure 8(a, b, c) shows examples of a method for bonding a new electrical contact 1 to a circuit board 7 after removing a damaged electrical contact 1', and a method for bonding a new electrical contact 1 to a new circuit board 7. An adhesive probe 11 having a tip that is difficult to solid-state bond with Au, such as stainless steel or W, is used to hold the new electrical contact 1 so that the conductive column 3 sandwiches the tip 12 of the adhesive probe 11 (Figure 8a). The new electrical contact 1 is bonded to the circuit board 7 via a conductive adhesive layer 8 by heating or applying ultrasonic waves to the tip 12 of the adhesive probe 11 (Figure 8b). After the electrical contact 1 is bonded and the conductive adhesive layer 8 is solidified, only the adhesive probe 11 is removed (Figure 8c).

[0023] The removal probe 9 and the bonding probe 11 are inserted into densely arranged electrical contacts 1, so their tip diameters are constrained. To compensate for the mechanical strength lost due to the thinning of the tip diameter, the removal probe 9 and the bonding probe 11 are preferably made of high-hardness metals such as Fe, Cr, Ni, W, Co, Mo, Pd, Ro, and their alloys.

[0024] To solid-state bonding the tip 10 of the removal probe 9 to the Au layer 4 of the damaged electrical contact 1', an Ag coating or an Al coating can also be used instead of the Au coating formed on the tip 10 of the removal probe 9.

[0025] If the base 2 is made of a material with a high diffusion coefficient with Au, the Au layer 4 may diffuse into the base 2 and disappear. In this case, the wear of the Au layer can be suppressed by interposing a metal layer between the Au layer 4 and the base 2 to inhibit diffusion. For example, if the material of the base 2 is Si, a Ni layer can be interposed on the base 2, and further, a Ti layer or Cr layer can be interposed to improve the adhesion of the Ni layer to the base 2.

[0026] Non-patent document 3 suggests that Al, Ag, Cu, etc., are candidates to replace the Au layer 4, but because these metals have oxide films growing on their surfaces, ultrasonic application, high-temperature heating, high-pressure, etc., are necessary for stable solid-state bonding.

[0027] A second embodiment of the present invention is shown in Figure 9. The electrical contact 1 consists of a base 2 and three conductive pillars 3 connected to the base 2, and has an Au layer 4 (Figure 9b) in region A (Figure 9a) of the base 2 surrounded by the three conductive pillars 3. Furthermore, the position of region A when the electrical contact 1 is viewed from below is shown in Figure 9a (bottom). The three conductive pillars 3 contact, for example, a cylindrical Cu post or an IC chip terminal with a hemispherical solder layer formed at the tip of the Cu post, by sandwiching the side of the IC chip terminal and making an electrical connection (not shown). Compared to the first embodiment, the IC chip terminal can be reliably electrically connected.

[0028] The method for removing the damaged electrical contact 1' and replacing it with a new, normal electrical contact 1, and the method for bonding the new electrical contact 1 to the new circuit board 7, can be carried out in the same manner as in the first embodiment, so the explanation and illustration of the method are omitted.

[0029] A third embodiment of the present invention is shown in Figure 10. The electrical contact 1 consists of a base 2 and four conductive pillars 3 connected to the base 2, and has an Au layer 4 (Figure 10b) in region A (Figure 10a) of the base 2 surrounded by the four conductive pillars 3. Furthermore, the position of region A when the electrical contact 1 is viewed from below is shown in Figure 10a (bottom). The four conductive pillars 3 contact, for example, a cylindrical Cu post or an IC chip terminal with a hemispherical solder layer formed at the tip of the Cu post, by sandwiching the side of the IC chip terminal and making an electrical connection (not shown). Compared to the second embodiment, the IC chip terminal can be electrically connected even more reliably.

[0030] The method for removing the damaged electrical contact 1' and replacing it with a new, normal electrical contact 1, and the method for bonding the new electrical contact 1 to the new circuit board 7, can be carried out in the same manner as in the first embodiment, so a description and illustration of the method are omitted.

[0031] While preferred embodiments illustrating the principles of the present invention have been shown above, the present invention is not limited to the configuration and operation as illustrated and described. Rather, those skilled in the art will understand that a variety of modifications and alterations to the present invention are possible without departing from the spirit and scope of the claims. Therefore, all such appropriate modifications and alterations should also be considered to fall within the scope of the present invention. [Explanation of symbols]

[0032] 1 Electrical contact 1' Damaged electrical contact 2 bases A pedestal area surrounded by multiple conductive pillars 3 Conductive Columns 4 Au layer 5 IC chip terminals 6 IC chips 7 Circuit board 8 Conductive adhesive layer 9. Removal probe 10 Tip of the removal probe 11. Adhesive probe 12. Tip of the adhesive probe

Claims

1. An electrical contact comprising a base and conductive pillars connected to the base, wherein, in order to contact the side surface of an IC chip terminal during electrical measurement and inspection of an IC chip, the electrical contact electrically connects the IC chip by sandwiching the side surface of the IC chip terminal with a plurality of conductive pillars, and the region of the base surrounded by the plurality of conductive pillars has an Au layer.

2. A method for bonding an electrical contact to a circuit board according to claim 1, wherein the electrical contact can electrically connect to an IC chip terminal by contacting the side surface of the IC chip terminal with a plurality of conductive pillars connected to a base, the method comprising the steps of: holding the electrical contact by sandwiching the tip of a probe between the plurality of conductive pillars of the electrical contact; bonding the electrical contact to the circuit board via a conductive adhesive layer using the probe that holds the electrical contact; and removing the probe after bonding the electrical contact to the circuit board.

3. A method for removing an electrical contact from a circuit board according to claim 1, wherein the electrical contact, which can electrically connect to an IC chip terminal by contacting the side surface of the IC chip terminal with a plurality of conductive pillars connected to a base, is adhered to the circuit board via a conductive adhesive layer, and the method for removing the electrical contact from the circuit board is characterized by comprising the steps of: solid-bonding the tip of a probe having a tip made of a material capable of solid-phase bonding with Au to the Au layer in the region of the base of the electrical contact surrounded by the plurality of conductive pillars; debonding the conductive adhesive layer that adheres the circuit board and the electrical contact; and separating the electrical contact, which has been bonded to the probe by solid-phase bonding with the Au layer of the base, from the circuit board together with the probe.

4. An electrical contact according to claim 1, characterized in that it has a metal layer between the base and the Au layer that suppresses Au diffusion.

5. An electrical contact according to claim 1, characterized in that the thickness of the Au layer is 500 Å or more.

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