Current test probe having a solder guide portion, and related probe assembly and production method

A probe for current test is provided. The probe includes a probe body having a plate-like connection portion whose end face becomes a connection face to a probe board, a solder layer formed on at least one side face of said connection portion, and a guide portion formed on the connection portion. The guide portion penetrates the connection portion in its thickness direction from the one side face with the solder layer formed to the other side face. When the solder layer is melted, the guide portion guides a portion of the melted solder to the other side face.

TECHNICAL FIELD

The present invention relates to a probe, a probe assembly suitable for a current test of semiconductor devices such as semiconductor integrated circuits and a method for producing them.

BACKGROUND

Semiconductor devices such as multiple semiconductor integrated circuits formed on each chip region of a semiconductor wafer undergo a current test to determine whether or not each of them is produced according to its specification. In this type of current test is used a probe assembly generally called probe card. When the plural probes (contacts) provided on a probe board of this probe assembly are pressed against their corresponding electrodes of a device under test, the device under test is connected to a tester through the probe assembly.

In this probe assembly, the probe is connected to each attaching land portion provided at a wiring circuit of the probe board.

In a conventional production of a probe assembly, lead-free cream solder containing multiple solder balls having a particle diameter of, e.g., 15-25 μm are generally used to adhere each probe to each corresponding attaching land portion of the probe board. The cream solder is supplied to connecting end portions of the probes by spraying. The probes to which the cream solder adhered are held at a predetermined attitude such that their connecting end faces abut the land portion of a probe board. In this held state, a laser beam is applied to the connecting end portion of the probe, melting the solder by its thermal energy, and solidification of the melted solder makes each probe fixed on the corresponding land portion.

It is, however, very difficult to apply a proper amount of cream solder to the connecting end portion of each probe by spraying. As shown inFIG. 4(b), if the amount of the solder3is short in combining the probe1and the wiring land portion2, connection strength becomes too low to obtain a desired connection strength. On the other hand, as shown inFIG. 4(c), excessive solder3sticking out largely from the wiring land portion2causes a short-circuit between the adjacent probes, and the excessive solder scattering around causes a contamination problem to probe handling instruments. Thus, the supply of the excessive solder brings about various inconveniences.

It is, therefore, proposed to plate the connection end face of the probe with tin as the solder, and to fix the probe on the probe board by a metal compound formed by melting together with a gilded layer formed on a contact mounting face of the probe board (see Patent Document 1).

According to this, since the solder is supplied beforehand to the connecting end face of each probe as tinned layer of the probe, the solder is not supplied excessively between the probe and the probe board. This can dissolve the problem of excessive supply of the solder.

However, since the tin to be formed on the probe connecting end face is formed by plating, the thickness of the layer is under severe restrictions. Furthermore, since the area of the connecting end face is small, the connecting end face cannot be enlarged without large-sizing the probe. Therefore, since it is not possible, by the technique described in the Patent Document 1, to hold a proper amount of solder enough to pass around behind both its side portions of the end face of the probe connection portion, an amount of solder sufficient to obtain a desired connecting strength cannot be supplied to the connection portion of the probe between the probe and the probe board.

DISCLOSURE OF THE INVENTION

Problem to be Solved

It is, therefore, an object of the present invention to enable to supply the solder to the connecting end portions in just proportion, thereby obtaining a sufficient connection strength without short-circuiting.

Means to Solve Problem

The probe for current test according to the present invention is characterized to comprise: a probe body which has a plate-like connection portion whose end face constitutes a connection face to a probe board; a solder layer formed on at least one side face of the connection portion; and a guide portion which is formed at the connection portion and penetrates from the one side face with the solder layer formed to the other side face in its plate thickness direction and which, when the solder layer is melted, can guide a portion of the melted solder layer to the other side face.

In the probe according to the present invention, the solder is preformed at least on one side face of the connection portion in a layer state. The connection portion being plate-like, the side face thereof with the solder layer formed has a sufficiently larger area than its end face. Since the solder layer is formed on the side face of the connection portion availing of this side face which has the large area, the present invention enables to reserve beforehand a just amount of solder in the probe body.

Effect pf the Invention

Also, since an adequate amount of solder can be supplied, it does not happen that an excess portion scatters around as heretofore, and it is possible to save the scattered excess portion which would have been discarded heretofore. It is also possible to prevent such environmental pollution as before caused by scattering the excess solder, which dispenses with a particular washing process of machines or instruments to handle the probes and simplifies a production process.

Further, a portion of the solder melted, for example, by heating can be surely passed around behind the other side face of the probe body through the guide portion. Thus, since the amounts of the melted solder can be approximately uniform by the melted solder flow through the guide portion on both sides of the connection portion, a proper amount of solder can be supplied to the probe connection portion so as to make the amounts of solder approximately uniform on both its sides without causing excess or shortage in supply of the solder. As a result, solder contamination of a probe handling device and probe short circuit due to excessive supply can be prevented, and strength poverty due to shortage in solder can be surely prevented. Also, if the area of the solder layer is selected properly, substantially uniform and proper fillets can be formed on both side faces of the connection portion of the probe body by hardening of the melted solder.

A solder layer can be provided on each side face of the connection portion of the probe body. In such a case, the thickness of the solder layer or its area can be reduced substantially to half as much as when a solder layer is provided on one side face. For equalization of the solder, it is desirable to provide the solder layers on both side faces of the connection portion. For simplification of the production process of the probes, however, it is desirable to provide the solder layer on one side face of the probe body.

The solder layer can be formed by a conductive adhesive layer made of a meltable metal material such as simple tin or a tin alloy containing any one or more of gold, silver, cupper and bismuth.

Also, for the solder layer can be used a plated layer formed by a plating method, for example, by electroforming. Since the thickness of the plating layer can be accurately controlled, the amount of solder to be supplied can be more accurately controlled by forming the solder layer from a plating layer. Thus, since this plating layer can prevent more surely the solder from sticking out, it is particularly effective for the probes arranged at narrow pitches.

The guide portion can be formed by a concave groove opening in the end face of the connection portion.

Also, the concave groove can be formed on the end face by a sinuous curved surface continuous in an extending direction that is orthogonal to the thickness direction of the connection portion.

The probe body can be made of nickel, its alloy or phosphor bronze. In such a case, adhesion of the solder to the probe body can be enhanced by disposing a gold plating layer between the one side face of the probe body and the solder layer.

A probe assembly can be made, using the probe for current test according to the present invention. This probe assembly is characterized by comprising a probe board having a wiring path with a plurality of attachment land portions formed and a plurality of probes to be adhered to the land portions of the probe board, each probe having a probe body including a plate-like connection portion whose end face is disposed opposite to the land portion; a solder layer formed on at least one side face of the connection portion; and a guide portion which is formed in the connection portion, penetrating the connection portion from the one side face with the solder layer formed to the other side face in the thickness direction of the connection portion, and which is capable of guiding a portion of the solder, when melted, toward the other side face, and characterized in that the end face of the connection portion is adhered to the corresponding land portion after the melted adhesive layer solidifies.

The production method of the current test probes according to the present invention is characterized by including: a step for forming by photolithography a probe body having a plate-like connection portion and a guide portion provided on the end face of the connection portion, the guide portion penetrating the connection portion in its thickness direction from one side face thereof to the other side face; and a step for forming a solder layer capable of melting at least on the one side face of the connection portion of the probe body and having the guiding portion guide a portion thereof to the other side, when melted.

According to the production method of the probe in the present invention, the probe body can be formed by using photolithography, so that the guide portion can be formed simultaneously with the formation of the probe body and that the probe can be produced efficiently.

The production method according to the present invention can be applied to the production of the probe assembly for current test. According to this method, the probe assembly of the present invention can be efficiently produced by irradiating the end portion with a laser for melting the solder layer, making the end face of the connection portion of the probe body of the probe abut the land portion.

Also, as in the case of the connection portion of the probe, it is possible to preform the solder layer on the land portion, thereby obtaining more sure coupling of the probe and the land portion.

According to the present invention, as described above, the solder is placed beforehand in a layer state at least on one side face of the connection portion, thereby enabling to reserve beforehand an adequate amount of solder on the probe body, and besides, a portion of the melted solder can be passed around surely behind the other side face of the probe body through the guide portion, so that, without causing excess or shortage in supplying the solder, an adequate amount of solder can be supplied approximately uniform on both sides of the connection portion of the probe.

BEST MODE TO CARRY OUT THE INVENTION

The probe10according to the present invention is, as shown inFIG. 1, provided with a generally plate-like probe body12. The probe body12has: a flat rectangular end face12awhich is used as a connection face to a wiring path described later; a plate-like connection portion14rising angularly from the end face; and an arm portion16extending at an obtuse angle θ in a direction approximately parallel to the longitudinal direction of the end face12afrom the front end of the connection portion14on a plane including the connection plane to a wiring path to be described later. The front end portion of the arm portion16rises in a direction to be away from the end face12aof the connection portion14, and a tip18is formed at the front end face.

The probe body12except the tip18is made of a highly tough metal material such as, for example, nickel, its alloy or phosphor bronze. In the illustration, in order to enhance the flexibility of the arm portion16, a long hole20penetrating in the thickness direction of the arm and extending along the longitudinal direction of the arm portion16is formed.

The tip18can be made of the same metal material as that of the probe body12integrally therewith. From the viewpoint of raising durability, however, the pyramidal tip18, as shown in the illustration, is preferably made of a hard metal material such as cobalt, rhodium or their alloys and embedded in the front end portion of the arm portion16.

For coupling the probe body12with the wiring path, a plating layer22made of solder is formed in the neighboring portion of the end face12aof the connection portion14, and a concave groove24opening in the end face is formed on the end face12a. A part of the connection portion14including the solder plating layer22and the concave groove24of the probe10is schematically shown in an enlarged state inFIGS. 2 and 3.

Each concave groove24is formed across the end face12ain its width direction, penetrating from one side face14aof the connection portion14to the other side face14b. In the illustration, three concave grooves24each having a flat bottom face are formed at intervals in the longitudinal direction of the end face12a.

In the examples shown inFIGS. 2 and 3, the solder plating layer22is formed on one side face14aof the connection portion14through the gold plating layer26. The gold plating layer26is formed, as clearly shown inFIG. 3, covering the end face12aof the probe10, and the neighboring portion of the end face12ain both side faces14aand14bof the connection portion14, and the solder plating layer22is formed, overlapping a portion covering one side face14aof the gold plating layer26.

The width dimension W of the solder plating layer22is approximately 600 μm, and the height dimension H thereof is approximately 250 μm. Thus, the area S of the solder plating layer22is approximately 600×250 μm2. Also, the thickness dimension t of the solder plating layer22is 30 μm±2 μm. In this case, the amount of solder held at the connection portion14of each probe10by the solder plating layer22is within a weight range of 30 to 35 mg.

The solder plating layer22can be formed by a conductive adhesive layer made of a metal material, such as a tin alloy containing one or more of a simple substance of tin or gold, silver, copper and bismuth, capable of melting by heating.

To combine the probe10with a wiring land portion2similar to the conventional one, as shown inFIG. 4(a), when the plating layer22formed on one side face14aof the connection portion14, as shown inFIG. 3, with the end face12mounted on the wiring land portion2is heated and melted, a portion of the liquid solder22is guided to the other side face14b, as shown inFIG. 4(a), through a path24aformed by a space of the concave groove24and is spread over the gold plating layer26.

The liquid solder22on the gold plating layer26is affected by gravity to cause a downward hanging and, as the temperature falls, is solidified into fillets as shown inFIG. 4(a). Since the liquid solder22is fixed on the connection portion14and the wiring land portion2due to its solidification, the probe10is fixedly coupled with the wiring land portion2through the solder.

As explained above alongFIGS. 4(b) and (c) concerning the conventional art, if excess or shortage in solder3occurs, a strong connection cannot be surely obtained, but it is possible to surely obtain a strong coupling of the probe10and the wiring land portion2by realizing the fillets without excess or shortage as shown inFIG. 4(a).

Such ideal fillets uniform on both side faces14aand14bof the connection portion14without excess and shortage can be achieved by holding a proper amount of solder as the plating layer22of the connection portion14and properly selecting the size of the guiding portion which is formed by the concave groove24.

To achieve ideal fillets, it is possible to preform a solder layer like the solder plating layer22on the wiring land portion2in case the amount of solder may be short by the solder plating layer22.

It is also possible to form the solder plating layer22on the gold plating layer26on both side faces14a,14bof the connection portion14.

It is possible to dispense with the gold plating layer26and form the solder plating layer22directly on the probe body12. It is desirable, however, to use the gold plating layer26in order to obtain a strong coupling between the solder22and the probe body12without using flux.

In place of the concave groove24formed on the end face12aof the probe10, it is possible, as shown inFIG. 5(a), to make a part of the end face12aa sinuous curved surface24-1. Each of the bottom parts of the sinuous curved surface24-1, when formed continuously in the longitudinal direction, that is, the extending direction, of the end face12ain a region excluding both ends thereof, can serve as a guide portion of the liquid solder22like the concave groove24.

The guide portion of the liquid solder22is not necessarily provided on the end face12a. For instance, as shown inFIG. 5(b), it is possible to form a guide portion as mentioned above by a plurality of through holes24-2opening in both side faces14a,14b, each penetrating the connection portion14in its thickness direction. The respective through holes24-2are arranged at a distance from the end face in the neighborhood of the end face12aof the connection portion14so as to be provided at a height position to enable to guide the melted liquid solder22to both side faces14a,14b.

The production method of the probe10according to the present invention is explained in the following with reference toFIGS. 6 and 7.

As shown inFIG. 6(a), when a liquid sensitive material is applied to a working plate30made of, for example, a stainless plate member having a flat surface30aand a photoresist film32is formed, an exposure mask (not shown) shaped to correspond to a planar pattern of the probe10is used on the photoresist film32, and the photoresist film32undergoes selective exposure. After this selective exposure, the photoresist film32undergoes film processing.

By this film processing, a recess34to expose the flat surface30aof the working plate30is formed on the photoresist film32, as shown inFIG. 6(b). This recess34corresponds to the planar configuration of the probe10including the arm portion16and also includes parts having a configuration corresponding to the concave groove24.

As shown inFIG. 6(c), when a gold plating layer36which has a thickness leaving the recess34is formed in a desired region of the recess34according to need, a layer38made of a conductive metal material such as the above-mentioned nickel, its alloy or phosphor bronze, is deposited in the recess34by use of heretofore well-known electroforming technique, as shown inFIG. 6(d). In case the gold plating layer36is formed under the conductive metal material layer38, the conductive metal material layer38is integrally formed with the underlying gold plating layer36.

After the deposition of the conductive metal material layer38, as shown inFIG. 6(e), the photoresist film32is removed, and then, as shown inFIG. 7(a), the conductive metal material layer38undergoes surface grinding so as to have a predetermined thickness.

After the surface grinding of the conductive metal material layer38, a sensitive material such as mentioned above is applied again to the working plate30and the conductive meal material layer38, and then, the sensitive material is subjected to the selective exposure and film processing using the same exposure mask as the one mentioned above. Thus, as shown inFIG. 7(b), a photoresist film40to fringe the conductive metal material layer38is formed so as to expose the conductive metal material layer38. This photoresist film40forms a recess42which exposes the conductive metal material layer38. The depth of the recess up to the surface of the conductive metal material layer is shallow. The recess42has a planar shape corresponding to that of the probe10.

By using the recess42of the photoresist film40, as shown inFIG. 7(c), a gold plating layer44similar to the gold plating layer36is formed in a desired region. This gold plating layer44continues to the aforementioned gold plating layer36integrally therewith at a portion covering the end face12aof the probe body12not shown inFIG. 7(c).

After the formation of the gold plating layer44, the photoresist film40is removed and the sensitive material is applied to cover the gold plating layer44, and subsequently, by using an exposure mask corresponding to the planar shape of the solder plating layer22, the sensitive material is selectively exposed. By the film processing after the sensitive exposure, as shown inFIG. 7(d), the depth of the recess48formed by this photoresist film46, that is, the depth up to the surface of the gold plating layer44is approximately equal to the desired thickness dimension t of the solder plating layer22.

Within the recess48, a conductive adhesive layer50made of a metal material which can melt by heating such as a tin alloy containing either one or more of the foregoing single tin substance or gold, silver, copper and bismuth is deposited by using the same electroforming is deposited on so as to be integral with the conductive adhesive layer44by using an electroforming technique similar to one mentioned above. Thereafter, the surface of the conductive adhesive layer50undergoes surface grinding according to need, the photoresist film46is removed from the working plate30, and the laminated body (36,38,44and50) is removed from the working plate30. Thus, the probe body12is formed as shown inFIG. 7(e), and the tip18is attached to the body to complete the probe10.

By a photolithography technique using the photoresist films32,40and46, the concave groove24or the sinuous curved surface24-1is formed on the end face12aduring the formation process of the probe body12, or a through hole24-2can be formed in the connection portion14of the probe body12, so that the probe12can be made efficiently.

Also, since the deposit area S and the deposit thickness5of the conductive adhesive layer50, that is, the plating layer22can be controlled at high accuracy by use of the photolithography, an adequate and accurate amount of solder without excess or shortage can be kept in the connection portion14.

The above-mentioned probe10can be used in a probe assembly60shown inFIGS. 8-10.

This probe assembly60is applicable to a current test of semiconductor integrated circuits such as plural semiconductor chips arranged in a matrix state on a semiconductor wafer not shown. The probe assembly60comprises, as shown inFIGS. 8 and 9, a circular wiring board62and a rectangular probe board64disposed on the underside of the wiring board. As shown inFIG. 8, a plurality of tester lands62ato be connected to a tester (not shown) for current test are formed on the upside of the wiring board62.

The probe board64is provided with, as shown inFIG. 10, an electrical insulating plate64asuch as ceramic, for example, and a plurality of wiring paths64bare formed on the underside of the insulating plate. Each wiring path64breaches the upside of the electrical insulating plate64awhich is not shown but well known heretofore, and the probe board64is secured to the wiring board so that each wiring path64bis connected electrically to the corresponding tester land62a, such that the upside of the probe board64, that is, the electrical insulating plate64aopposes to the underside of the wiring board62.

In the example shown inFIG. 10, the probe10and a probe10′ similar to the probe is used. A difference between the probe10and the probe10′ is that an angle θ between the connection portion14of the probe10and the arm portion16is an obtuse angle, while in the probe10′, the angle between the connection portion14and the arm portion56is an acute angle θ′. Otherwise, other constitutions are the same as those of the probe10.

Each wiring path64bis formed on both sides of a perpendicular plane which includes an imaginary straight line L and orthogonal to the electrical insulating plate64a. Each wiring path64bextends towards the perpendicular plate with the extending direction of the imaginary line L as a width direction. Also, the wiring paths64bare arranged such that those whose distal end positions are near the imaginary line L and those whose distal ends are far therefrom become alternate. Further, there is a gap between the arrangements of the wiring paths64bon both sides of the imaginary line L so that the extension line of each wiring path64bon one side of the imaginary line L may extend between those on the other side.

At each distal end position the land portion66(66a,66b) is formed, and on each side of the imaginary line L, the probe10′ is disposed on the attachment land portion66aprovided at a relatively remote position from the imaginary line. Also, the probe10′ is disposed on the attachment land portion66bwhich is provided nearer the imaginary line L than the attachment land portion66ais.

The respective probes10and10′ are alternately aligned along the imaginary straight line L with their tips18aligning on the imaginary straight line L. With each end faces12amounted on the corresponding attachment land portion66(66a,66b), the solder plating layer22of each probe10,10′ is scanned by a laser beam to heat and melt the solder plating layer22efficiently, and by the solidification due to the lowering of temperature, thereby securing each probe10,10′ firmly to the corresponding land portion66without excess or shortage of solder.

Also, adopting such an arrangement form of the respective probes10,10′ and wiring paths64bas shown inFIG. 10surely prevents adjoining probes10,10′ from being damaged and enables to arrange the tips18of the plural probes10,10′ closely.

INDUSTRIAL APPLICABILITY

The present invention is not limited to the above embodiments but can be variously modified without departing from its purport.