Apparatus to perform a non-contact test of a semiconductor package

An apparatus to test a semiconductor package includes a vertical illuminator to supply vertical illumination in the same axial direction as a measurement target and a vertical image unit to capture a vertical image of the measurement target so that a testing apparatus may 2-dimensionally determine information on the shape, size, or position of a solder ball. An inclined illuminator may supply inclined illumination in a different axial direction from the measurement target, and an inclined image capture unit may capture a side image of the measurement target so that the testing apparatus may 3-dimensionally determine information on a state of contact of the solder ball with the ball land. The inclined image capture unit may include a color camera using color information, thereby markedly increasing test reliability and yield.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 to Korean Patent Application No. 10-2008-0124144, filed Dec. 8, 2008, the contents of which are incorporated herein by reference in their entirety.

BACKGROUND

1. Field of the Invention

Example embodiments relate to a semiconductor package testing apparatus, and more particularly, to an apparatus to test a stacked semiconductor package, or multi-stack package (MSP), which provides vertical and inclined images from various angles to obtain a stereoscopic effect and employs color information from a color camera to improve test reliability and shorten a test time.

2. Description of the Related Art

With an increase in integration density of electronic/information apparatuses, demands for high-pin-count semiconductor packages have increased. Thus, a vast amount of research is being conducted on Array Type semiconductor packages, such as ball-grid-array (BGA) packages, which satisfy the demands for the high-pin-count semiconductor packages and reduce chip sizes and fabrication costs. In recent years, a fine-pitch BGA package, which is a kind of chip scale package, has been developed.

In addition, brisk development of stacked semiconductor packages (MSP) in which chips are stacked, packages are stacked, or chips and packages are stacked together has progressed to increase the capacity and integration density of semiconductor devices.

In general, a semiconductor device is an essential component for computers and household electrical appliances. The semiconductor device necessarily undergoes a precise test after production and before shipment. A semiconductor device requires a far higher degree of precision than other components. Therefore, a very small defect in an internal element or external appearance of the semiconductor device may be detrimental to its performance.

A defect in lead or ball, which occurs during the assembly of a printed circuit board (PCB), affects an external appearance of a semiconductor device. Accordingly, a process of testing the state of a lead or ball of a semiconductor device including a PCB on which a ball grid array (BGA) is mounted is being regarded as very important among semiconductor-device testing processes.

SUMMARY

Example embodiments provide a semiconductor package testing apparatus, which obtains an image of a multi-stack package (MSP) in a vertical direction to determine information on size, shape, or position of a solder ball, information on generation of particles, and information on cracks or other losses in the solder ball.

Example embodiments also provide a semiconductor package testing apparatus, which obtains an image of an MSP in a lateral direction to determine 3-dimensional information on a contact portion between a solder ball and a ball land when a non-wet defect between the solder ball and the ball land is tested.

Example embodiments further provide a semiconductor package testing apparatus, which employs color information to improve test reliability when a contact of a solder ball with a ball land is tested in a noncontact manner.

Features and/or utilities of the present general inventive concept may be realized by a semiconductor package testing apparatus including a vertical illuminator to supply vertical illumination in the same axial direction as a measurement target, an inclined illuminator to supply inclined illumination in a different axial direction from the measurement target, a vertical image capture unit to capture a vertical image of the measurement target, and an inclined image capture unit to capture an inclined image of the measurement target.

The vertical illumination to illuminate the measurement target may travel along the same light path as the light reflected by the measurement target, and the inclined illumination may travel along a light path to the measurement target that is different than the light path of light reflected by the measurement target.

The measurement target may be a stacked semiconductor package. Each of the vertical and inclined illuminators may illuminate both sides of the measurement target, and each of the vertical and inclined image capture units may capture inclined images of the measurement target.

The vertical image of the measurement target may contain information on the sizes, shapes, and positions of a solder ball and a ball land that are connected to each other to electrically connect a plurality of packages constituting the stacked semiconductor package. The inclined image of the measurement target may contain information on a bonding state between a solder ball and a ball land that are connected to each other to electrically connect a plurality of packages constituting the stacked semiconductor package.

The vertical illuminator may be a plate including a plurality of light emitting diodes (LEDs). The plate may be installed parallel to a light path of irradiation light emitted toward the measurement target and a light path of reflection light reflected by the measurement target, and a half mirror functioning as a beam splitter may be installed at a predetermined tilt angle in front of the plate. The half mirror may change a light path of irradiation light emitted by the LEDs in a vertical direction and allow the reflection light to pass therethrough and be incident to the vertical image unit.

The tilting illuminator may have a hemispheric dome shape having an inner surface on which a plurality of LEDs is mounted. Also, the tilting illuminator may have a central opening to allow irradiation light incident to the measurement target and reflection light reflected by the measurement target to pass therethrough.

The vertical image capture unit may determine self-information on the shape, size, or position of a solder ball, peripheral information on generation of particles, and information on a bonding state between the solder ball and a ball land.

The inclined image capture unit may be installed at an inclined angle with respect to the measurement target to capture an image of a contact portion between a solder ball and a ball land. A reflection mirror may be further disposed on one side of the inclined image capture unit to allow the reflection light reflected by the measurement target to be incident to the inclined image capture unit. The inclined image capture unit may be installed at an inclined angle with respect to an optical axis of reflection light re-reflected by the reflection mirror.

The semiconductor package testing apparatus may further include a condensing lens and an optical angle shifter. The condensing lens may be disposed in front of the inclined image capture unit and condense the incident reflection light. The optical angle shifter may be disposed between the inclined image capture unit and the condensing lens and may shift a direction of the reflection light re-reflected by the reflection mirror such that the light path of the reflection light is consistent with the inclined image capture unit. When reflection light reflected at two spots of the measurement target is re-reflected by the reflection mirror and incident to the inclined image capture unit, the optical angle shifter may compensate for a difference in length between two light paths starting from the two spots.

The inclined image capture unit may include a color camera using color information to determine whether or not a solder ball is bonded to a ball land. The inclined image capture unit may extract colors from the color information and determine whether or not the solder ball is bonded to the ball land based on the extracted colors. The solder ball may be formed of lead (Pb) that takes on a blue color, and the ball land may be formed of copper (Cu) that takes on a red color. When the lead melts during a reflow process, the lead may be attached to the copper and the copper may be concealed so that only the blue color may be detected. Conversely, when the lead does not melt during the reflow process, the lead may not be attached to the copper and the copper may be exposed so that both the red and blue colors may be detected.

The color camera may obtain light reflected from the surface of the measurement target as color information and extract a red (R) value, a blue (B) value, and a green (G) value from the obtained color information. Thus, when subtracting the B value from the R value gives a value higher than a critical value, the color camera may determine that the solder ball and the ball land are in a non-wet state. Also, when subtracting the B value from the R value gives a critical value or lower, the color camera may determine that the solder ball and the ball land is in a wet state.

The vertical and inclined illuminators and the vertical and inclined image capture units may be mounted in a case, and a portion of a bottom surface of the case corresponding to the measurement target may be opened to allow irradiation light emitted toward the measurement target and reflection light reflected by the measurement target to pass therethrough. The case may further include an illumination mount on which the vertical and inclined illuminators are mounted. The illumination mount may be disposed on the opened bottom surface and have an opening formed in the center of each of top and bottom surfaces thereof to allow illumination to pass therethrough. The vertical illuminator may be vertically mounted on an outer top surface of the illumination mount, and the inclined illuminator may be installed inside the illumination mount. The case may include a camera mount having at least an opened portion of a bottom surface through which the irradiation light and the reflection light pass. Also, the vertical image capture unit and the inclined image capture unit may be installed at a ceiling of the camera mount not to interrupt light paths of the irradiation light and the reflection light.

Features and/or utilities of the present general inventive concept may also be realized by a semiconductor package testing apparatus including an inclined illuminator installed above a measurement target and having a hemispheric shape, the inclined illuminator having a plurality of LEDs disposed on a portion other than an opening formed in the center thereof to supply illumination to the measurement target, an inclined image capture unit configured to receive reflection light reflected by the measurement target and capture a side image of the measurement target, a reflection mirror installed at an inclined angle on one side of the inclined image capture unit to guide the reflection light reflected by the measurement target into the inclined image capture unit, and a condensing lens installed in front of the inclined image capture unit and configured to condense incident reflection light.

The measurement target may be a stacked semiconductor package in which a ball land to which a solder ball is attachable is formed on a first surface of a printed circuit board (PCB), and the solder ball is bonded to the ball land during a reflow process and functions as an input/output terminal of the PCB. The inclined image capture unit may be installed at a predetermined angle with respect to an optical axis of reflection light re-reflected by the reflection mirror to capture an image of a contact portion between the solder ball and the ball land.

The semiconductor package testing apparatus may further include an optical angle shifter disposed between the inclined image capture unit and the condensing lens. The optical angle shifter may shift a direction of the reflection light. When reflection light reflected at two spots of the measurement target is re-reflected by the reflection mirror and incident to the inclined image capture unit, the optical angle shifter may compensate for a difference in length between two light paths starting from the two spots.

The inclined image capture unit may obtain light reflected from the surface of the measurement target as color information, extract a red (R) value and a blue (B) value from the color information, and determine whether or not the solder ball is bonded to the ball land based on the color information. When the solder ball and the ball land are in a wet state, the solder ball formed of lead (Pb) may melt during a reflow process and be bonded to the ball land formed of copper (Cu) and the ball land formed of the copper may be concealed so that subtracting the B value from the R value gives a critical value or lower. Conversely, when the solder ball and the ball land are in a non-wet state, the solder ball formed of lead may not melt during the reflow process and the ball land formed of the copper may be exposed so that subtracting the B value from the R value gives a value higher than a critical value. In this case, the critical value may range from 0 to 255 on condition of 8 bits.

Features and/or utilities of the present general inventive concept may also be realized by a testing apparatus including a first illumination device to illuminate a target area of a tested device, the first illumination device providing illumination to the target area such that light from the first illumination device contacts the target area along an axis parallel to a center length axis of the tested device, a second illumination device to illuminate a target area of a tested device, the second illumination device providing illumination to the target area such that light from the second illumination device contacts the target area along an axis that is not parallel to a center length axis of the tested device, a first image capture device to receive light from the first illumination device reflected off of the target area, and a second image capture device to receive light from the second illumination device reflected off of the target area. The center length axis of the tested device may define a first direction.

The second image capture device may include a color-receptive image capture device.

The first illumination device may include a substantially flat plate and a plurality of light emitting diodes mounted to the plate.

The second illumination device may include a substantially dome-shaped structure having a hole at a peak of the dome to permit light to pass through the hole and a plurality of light emitting diodes mounted to an inside surface of the dome-shaped structure.

The testing apparatus may further include a beam-splitting mirror positioned along a light path between the first illumination device and the target area, to reflect light from the first illumination device toward the target area, and to pass light from the target area toward the first image capture device. The beam-splitting mirror may be positioned at a 45° angle with respect to the first direction.

The testing apparatus may further include a mirror to reflect light that has been reflected off of the target area from an inclined angle to be parallel with respect to the first direction, and the mirror may reflect the light from the tested device toward the second image capture device.

The testing apparatus may further include a condensing lens to receive and condense the light from the mirror and an optical angle shifter to receive the condensed light from the condensing lens and to adjust the light to provide a focused image to an image-reception end of the second image capture device.

The second image-capture unit may be positioned to have a center length axis that is not parallel to the first direction.

The testing apparatus may further include a case, and the first and second illumination devices and first and second image capture devices may be mounted to be located on an inside of the case to be fixed with respect to the case.

The testing apparatus may further include a camera mounting structure having a height less than a height of the case, and the first and second image capture devices may be mounted to an inner surface of a top side of the camera mounting structure.

The testing apparatus may further include an illumination unit mounting structure mounted to an inside surface of a lower portion of the case, and the first and second illumination devices may be mounted to the illumination unit mounting structure.

Features and/or utilities of the present general inventive concept may also be realized by a method of testing a tested device, the method including positioning the tested device to have a length axis parallel to a first direction, emitting a first light to travel in the first direction to contact a test area of the tested device, capturing a first image of the test area generated by the first light reflected off of the test area of the tested device at a 180° angle with respect to the first direction, emitting a second light to travel in a second direction that is not parallel to the first direction, and capturing a second image of the test area generated by the second light reflected off of the test area at a second angle that is not parallel to the first direction.

The method may further include capturing color data of the second image. The color data may correspond to red, green, and blue color of the test area.

Capturing the second image may include capturing light that travels parallel to the first direction.

A light path of the light that travels parallel to the first direction may be adjusted to enter an image-receiving surface of an image-capture device at an angle that is not parallel to the first direction.

Emitting the first light may include emitting the first light in a second direction perpendicular to the first direction and reflecting the first light off of a beam-splitting mirror to travel parallel to the first direction toward the target area.

Capturing the first image may include capturing light reflected off of the target area and passed through the beam-splitting mirror.

Capturing the second image may include capturing the second light reflected off of the test area at an angle that is not parallel to the first direction and reflected off of a mirror to travel in a direction parallel to the first direction.

The method may include providing a first illumination device to emit the first light, a second illumination device to emit the second light, a first image-capture device to capture the first image, and a second image capture device to capture the second image, mounting the first illumination device, the second illumination device, the first image-capture device, and the second image capture device to a case having a hole in a bottom of the case to pass light, and positioning the tested device outside the case adjacent to the hole.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1is a cross-sectional view of a stacked semiconductor package that may be analyzed by a testing device according to an example embodiment.

Referring toFIG. 1, a stacked semiconductor package, or multi-stack package (MSP),100may include a first semiconductor package110and a second semiconductor package120stacked on the first semiconductor package110.

The first semiconductor package110may include a single first chip114adhered onto a first printed circuit board (PCB)112. The single first chip114may be electrically connected to the first PCB112by first bonding wires116and encapsulated using a first molding resin118. The second semiconductor package120may include a plurality of second chips124adhered to and stacked on a second PCB122. The plurality of second chips124may be electrically connected to the second PCB122by second bonding wires126and encapsulated using a second molding resin128.

A plurality of first ball lands132may be located on a bottom surface of the first PCB112, and a plurality of second ball lands134may be located on a bottom surface of the second PCB122. First solder balls136functioning as external terminals may be bonded to the first ball lands132, respectively, and second solder balls138functioning as external terminals may be bonded to the second ball lands134.

Meanwhile, third ball lands140may be disposed on a top surface of the first PCB110. When the second semiconductor package120is stacked on the first semiconductor package110, the second solder balls138may be bonded onto the third ball lands140. Specifically, a predetermined flux may be coated on the third ball lands140, and the first and second semiconductor packages110and120may be thermally bonded to each other under pressure such that the second solder balls138of the second PCB122are positioned on the third ball lands140, respectively. Thus, the second semiconductor package120may be stacked on the first semiconductor package110and, simultaneously, the first and second semiconductor packages110and120may be electrically connected to each other by the second solder balls138.

However, the stacked semiconductor package100may suffer a non-wet defect between the second solder ball138, which electrically connects the first and second semiconductor packages110and120, and the third ball land140of the first semiconductor package110.

For example, a non-wet defect may occur due to negligent management of a flux with a predetermined viscosity to be coated on the third ball land140to bond the second solder ball138to the third ball land140. Alternatively, an excessively small amount of the flux coated on the third ball land140may result in a non-wet defect.

Since it is impossible to detect these non-wet defects by means of current equipment, an operator should perform a total inspection. Therefore, it is absolutely necessary to develop an apparatus to test a stacked semiconductor package in a non-contact manner to detect whether or not the stacked semiconductor package has a non-wet defect.

As shown inFIGS. 2,3A,3B,4A, and4B, a semiconductor package testing apparatus200according to the present general inventive concept may include a vertical illuminator210, an inclined illuminator220, a vertical image capture unit230, and an inclined image capture unit240.

In the description to follow, the term “vertical” is used to describe a relationship between various elements of the general inventive concept including the package testing apparatus200and the stacked semiconductor package100. However, the package testing apparatus200and the stacked semiconductor package100may be arranged in any direction, such as horizontally, upside-down, or at any other predetermined angle. As illustrated inFIG. 9, the “vertical” direction in this description corresponds to a first direction301parallel to a length axis A1of the stacked semiconductor package100.

As illustrated inFIG. 3A, the vertical illuminator210emits light in a horizontal direction302toward a beam-splitting mirror212. The beam-splitting mirror212reflects the light to travel in a vertical direction301onto the measurement target or target area P, which may be a portion of the stacked semiconductor package100. For example, the measurement target, or target area, P may be a connection comprising a second ball land134, a second solder ball138, and a third ball land140. The stacked semiconductor package100may be positioned vertically, or may be positioned to expose the measurement target P to light traveling along an axis parallel to the vertical direction301.

As illustrated inFIG. 3B, the light transmitted from the beam-splitting mirror212to the measurement target P may then be reflected off the measurement target P in the vertical direction301towards the vertical image capture unit230. The light may pass through the beam-splitting mirror212and to the vertical image capture unit230for analysis.

As illustrated inFIG. 4A, the inclined illuminator220may emit illumination to the measurement target P at an angle that is inclined with respect to the direction301. Light from the inclined illuminator220may reflect off a surface of the measurement target P at an angle so that the reflected light travels in a direction that is not parallel to vertical301. The light may travel parallel to a center axis a3of the inclined image capture unit240at an image-receiving end241of the inclined image capture unit240

The vertical illuminator210, the inclined illuminator220, the vertical image capture unit230, and the inclined image capture unit240may be mounted in a case260to provide illumination and to capture an image at a predetermined distance and angle. The case260may have a rectangular shape with an inner space in which the vertical illuminator210, the inclined illuminator220, the vertical image capture unit230, and the inclined image capture unit240are mounted. A portion of a bottom surface of the case260corresponding to a position of the measurement target P may be opened to allow light emitted from the illuminators210,220and reflected from the measurement target P to pass therethrough.

The measurement target P may be located below the case260. The stacked semiconductor package100may be mounted in a holder290that may be moved horizontally302or vertically301with respect to the testing apparatus200. Alternatively, the testing apparatus200may be moved with respect to the holder290.

Sizes, shapes, or positions of a solder ball138and a ball land140of the measurement target P may be measured by illuminating the measurement target P with the vertical and inclined illuminators210,220and analyzing the light reflected from the measurement target100with the vertical and inclined image capture units230,240. The vertical illuminator210and the inclined illuminator220may illuminate one or multiple sides of the measurement target P.

The testing apparatus according to the present inventive concept may measure not only the shape of a ball-grid-array (BGA) ball or defects in a ball-grid-array ball but also the shape of lead used to bond a semiconductor chip to a PCB substrate and a defect in the lead. However, for brevity, the present example embodiment is limited to the measurement target P including the solder ball138and ball land140of the stacked semiconductor package100.

An illumination mount270on which the vertical illuminator210and the inclined illuminator230are mounted may be provided on the opened bottom surface of the case260. The illumination mount270may include an opening to allow light to pass therethrough.

The vertical illuminator210may be vertically mounted on a top surface of the illumination mount270. Alternatively, the vertical illuminator210may be mounted directly on an inner sidewall of the case260. The vertical illuminator210is offset from a straight line between the measurement target P and the vertical image unit230so as to avoid blocking light paths between the measurement target P and the vertical image unit230. The vertical illuminator210may be a plate having a surface on which a plurality of light emitting diodes (LEDs) is mounted.

Since the vertical illuminator210is positioned to the side of the measurement target P, the beam-splitting mirror212is positioned in the vertical direction301above the measurement target P to reflect a path of light from the vertical illuminator210to travel toward the measurement target P and to allow reflected light from the measurement target P to pass through the beam-splitting mirror212to travel toward the vertical image capture unit230. The beam-splitting mirror212may be installed at an angle of about 45° with respect to vertical301. Furthermore, an inter-mirror214may be further provided between the beam-splitting mirror212and the vertical illuminator210to prevent irradiation light emitted from the vertical illuminator210from being totally reflected by the half mirror212. In this case, since light passing through the inter-mirror214or a coating mirror may be emitted in all directions, total reflection of light may be prevented.

The inclined illuminator220may be mounted in the illumination mount270. The inclined illuminator220may have a hemispheric dome shape having an inner surface on which a plurality of LEDs is mounted. An opening through which irradiation light and reflection light pass may be formed in the center of the dome-shaped inclined illuminator220. Since the LEDs are disposed and irradiate light in a hemispheric shape, the inclined illuminator220may provide illumination to the measurement target P from various angles.

A camera mount280may be further provided in the case260. At least a portion of a bottom surface of the camera mount280may be open to facilitate mounting the camera mount280to the illumination mount270. The vertical image capture unit230and the inclined image capture unit240may be installed on a ceiling of the camera mount280such that the vertical image capture unit230and the inclined image capture unit240may perform respective specific functions without interrupting the irradiation light path from the illuminators210,220to the measurement target P and the reflection light path from the measurement target P to the image capture units230,240. Using the camera mount280, the vertical image capture unit230and the inclined image capture unit240may be efficiently installed in a minimum space without affecting or being affected by other components.

The vertical image capture unit230may be installed toward a lower portion of the case260or the camera mount280. More specifically, the vertical image capture unit230may be installed closer to the measurement target P than the upper side of the case260or the camera mount280. For example, the vertical image capture unit230may be installed on an upper side of the camera mount280that may separated from an upper side of the case260by a predetermined distance d1. The vertical image capture unit230may obtain information on the measurement target P based on light that is irradiated by the vertical illuminator210. For example, the vertical image capture unit230may determine information on the shape, size, or position of the solder ball138or information on a bonding state between the solder ball138and the ball land140based on light reflected from the measurement target P.

The vertical image capture unit230may also determine whether or not the solder ball138suffers a crack, deformation, or another loss based on information on the shape of the solder ball138. Furthermore, after a reflow process, the vertical image capture unit230may determine whether the solder ball138is bonded to the ball land140based on the shape of the solder ball138.

FIG. 5illustrates an image of the measurement target P captured by the vertical image capture unit230. InFIG. 5, the vertical image capture unit230determines that two different kinds of solder balls138exist in the measurement target P. The first solder ball138ahas a jar shape, in which the solder covers each of the second ball land134and the third ball land140. The second solder ball138bhas a spherical shape. The vertical image capture unit230is able to determine that, since the solder ball138bhas a spherical shape, the solder ball138bis not properly bonded to the ball land140. In contrast, since solder ball138ahas a jar shape as a result of an annealing process, the solder ball138ais bonded to the ball land140. In addition, the vertical image unit230may determine whether or not the solder ball138or the ball land140has particles that cause an electrical short. Accordingly, it can be determined whether or not the solder ball138is defective based on the position, height, or shape of the solder ball138.

Meanwhile, since a semiconductor packaging process is carried out at a high temperature, thermal stress may be applied to the PCBs and semiconductor chips. A warping defect may occur due to a difference in the coefficient of thermal expansion between a PCB and a semiconductor chip. Thus, a solder ball138attached to a predetermined region of a first PCB may not be bonded to a ball land140of a second PCB due to the warping of the first PCB. In addition, even if one side of a solder ball138is bonded to a ball land140, the other side of the solder ball130may be shifted so that the solder ball138cannot function as an input/output terminal.

As described above, information on the shape of the solder ball138and information on a bonding state between the solder ball138and the ball land140may be analyzed using the vertical image capture unit230. However, most non-wet defects cannot be detected by the vertical image capture unit230. For example, when one side of the solder ball138is bonded to the ball land140and the other side of the solder ball138is shifted, even if the stacked semiconductor package100has a substantial non-wet defect, the vertical image capture unit230cannot detect the shifted side of the solder ball138. To overcome this restriction, the semiconductor package testing apparatus200may further include the inclined image capture unit230capable of capturing an image from various angles.

The inclined image capture unit240may be installed on one side of the vertical image capture unit230and may capture an angled image of the measurement target P. As described above, the vertical image unit230may detect only the side of the measurement target P and cannot easily detect a region including the ball land140disposed on a plane surface of a PCB. In other words, the vertical image capture unit230may capture a 2-dimensional image but not a 3-dimensional image. Since non-wet defects are mainly detected at a contact portion between the solder ball138and the ball land140, the testing apparatus200may detect the non-wet defect by capturing an image at a predetermined tilt angle.

In addition, the inclined image capture unit240may detect more objectively whether or not the solder ball138is bonded to the ball land140based on color information of a captured image. This is due to the fact that information on the shape of the solder ball138always has a measurement error. Thus, when a non-wet defect between the solder ball138and the ball land140is detected based on the side image of the measurement target P, the inclined image capture unit240may employ the color information of the captured image.

Typically, the solder ball138is a ball-shaped material that connects PCBs and transmits an electrical signal. The solder ball138may melt during a reflow process, thus deforming its ball shape. For example, a typical solder ball138may be formed of eutectic tin-lead obtained by mixing tin (Sn) and lead (Pb) in a ratio of 63% to 37%. Thus, the lead takes on a bluish gray color. The ball land140may be formed of conductive copper (Cu), which takes on a reddish yellow color. When the lead melts during the reflow process, the shape of the solder ball138may be deformed so that the lead may be attached to the surface of the ball land140formed of copper. Accordingly, when the lead efficiently melts and the solder ball138is normally bonded to the ball land140, the reddish yellow color of the ball land140cannot be detected, but only the bluish gray color of the solder ball138may be detected.

Accordingly, the inclined image capture unit240may include a color camera, which may obtain light reflected from the surface of the measurement target P as color information and extract red (R), blue (B), and green (G) values from the color information.

When subtracting a B value from the extracted R value gives a positive (+) value, the testing apparatus200may determine that the stacked semiconductor package100is defective. This is because when the solder ball138is not annealed at a required temperature, the solder ball138cannot be bonded to the ball land140. In other words, when the solder ball138does not melt and cover the ball land140, the ball land140may not turn gray but still remain yellow. When subtracting the B value from the extracted R value gives a value other than a positive (+) value, the testing apparatus200may determine that the stacked semiconductor package100is normal. For example, when the R value is equal to the B value or subtracting the B value from the R value gives a negative (−) value, it may be determined that the stacked semiconductor package100is normal.

Here, neither a positive (+) value nor a negative (−) value refers to an absolute value. For example, since the intensity of each of an R value, a B value, and a G value ranges from 0 to 255 on condition of 8 bits, a user may determine a desired critical value within the given range. In the present general inventive concept, a defective stacked semiconductor package may be distinguished from a normal multi-stack package. Thus, when an stacked semiconductor package has a value higher than a critical value, it is determined that the solder ball138and the ball land140are in a non-wet state, and when the stacked semiconductor package has the critical value or lower, it is determined that the solder ball138and the ball land140are in a wet state.

FIG. 6illustrates an image of the measurement target P captured by the inclined image capture device240. InFIG. 6, the solder ball138bis in a non-wet state with the ball land140. Specifically, the solder ball138bformed of lead (Pb) does not cover the ball land140formed of copper (Cu) so that the ball land140is exposed. As illustrated in the chart ofFIG. 7, the right image may have an R value of 139, a G value of 92, and a B value of 31. Thus, the R value is greater than the B value.

Referring again toFIG. 6, the solder ball138ais in a wet state with a corresponding ball land (not shown). Specifically, the solder ball138aformed of lead covers the ball land formed of copper. As illustrated in the chart ofFIG. 7, the left image may have an R value of 96, a G value of 86, and a B value of 96. Thus, the R value is equal to the B value.

Referring again toFIG. 4A, a reflection mirror242may be positioned within the case260to reflect light from the measurement target P toward the inclined image capture unit240. A condensing lens244may be positioned in front of the inclined image capture unit240to condense light reflected off the measurement target P and to direct the condensed light toward the inclined image capture unit240.

An optical angle shifter246may be positioned between the inclined image capture unit240and the condensing lens244to adjust a light path of reflection light condensed by the condensing lens244. The optical angle shifter246may be a beam shaping prism, which functions to shift a direction of reflection light condensed by the condensing lens244at a predetermined angle and to collimate the reflection light. Since an optical axis of light reflected from the measurement target P is inclined at a predetermined angle with respect to vertical301, when the inclined image capture unit240is positioned in a vertical direction, the tilting image unit240may be out of focus. The optical angle shifter246adjusts the light path of the reflected light to bring the image received by the inclined image capture unit into focus.

That is, as shown inFIG. 8, since the space in an image corresponding to the measurement target P has a predetermined volume, when reflection light reflected at two points of the measurement target P is re-reflected by the reflection mirror242and incident to the inclined image capture unit240, the length of a light path from a first point of the measurement target P to the camera may be different from that of a light path from a second point of the measurement target P to the inclined image capture unit240. That is, a light path A-B-C may be longer than a light path A′-B′-C′ (a light path A-B-C>a light path A′-B′-C′). When the inclined image capture unit240is installed along an optical axis of reflection light, the inclined image capture unit240may capture a distorted image different from an original shape of the measurement target P due to the difference in length between the two light paths. Accordingly, the inclined image capture unit240should be installed at an angle with respect to the optical axis of the reflection light to capture an image reflecting the original shape of the measurement target P. In this case, the optical angle shifter246may be required to compensate for a difference in length between the two light paths (a light path D<a light path D′) and collimate reflection light (a light path A-B-C-D=a light path A′-B′-C′-D′).

FIG. 4Billustrates the inclined image capture unit240being mounted on a side wall of the camera mount280. The image capture unit240may be mounted at an angle with respect to vertical301or may be mounted such that a center axis of the image capture unit240is parallel to a vertical301axis. An optical angle shifter246may adjust the reflected light to prevent image distortion into the inclined image capture unit240.

FIGS. 9,10A, and10B illustrate center length axes of the stacked semiconductor chip package100and the image capture devices230,240.

As illustrated inFIG. 9, a stacked semiconductor chip package100has a length direction L corresponding to a length of a semiconductor chip and a height direction H corresponding to a height of the first semiconductor package110, the second semiconductor package120, and the second solder balls138between the first and second semiconductor packages. Details of the stacked semiconductor package100are described above with respect toFIG. 1and are omitted from the description ofFIG. 9.

A center length axis is defined as an axis A travelling in a length direction of the stacked semiconductor package100at a location that is substantially half the height H of the semiconductor package100. The center length axis A may also correspond to half of a width (not shown) of the semiconductor chip package100. When a stacked semiconductor package includes more than first and second semiconductor packages, the center length axis A corresponds to half the height of all of the semiconductor packages and the intervening solder balls, connections, and/or filling of the stacked semiconductor package. As illustrated inFIG. 9, the center length axis A of the stacked semiconductor package100is substantially parallel to the flat surfaces of the semiconductor chips in the semiconductor package100.

When the stacked semiconductor package100is positioned beneath a testing unit200, it may be positioned vertically, as shown inFIG. 9, so that the center axis A may correspond to a vertical direction301and an end solder ball138may be illuminated and imaged.

FIG. 10Aillustrates an image capture device230,240having substantially rectangular sides. The image capture device230,240has a length L corresponding to a distance between a rear side and an image-capture side. The image capture device230,240has a width W corresponding to an edge of the rear side or the image-capture side. A length axis B1of the image capture device230,240is defined as an axis that is substantially at a center of each opposite side and each opposite corner. The length axis B1travels in a length L direction of the image capture device230,240and intersects each of the rear side and the image-capture side. When the rear side and image capture side are flat, the axis B1intersects the sides at a right angle.

Since the image capture device230,240may have any shape, and may not have flat sides, the length axis B1may be defined as travelling in a length direction of the image capture device230,240an intersecting the image-capture side at a right angle, if flat, and at a tangent at its apex, if curved.

FIG. 10Billustrates an image capture device230,240having a substantially cylindrical shape. The length L of the image capture device230,240may be defined as a distance from the rear side to the image-capture side231,241, and a diameter D1or width of the cylinder may be defined as a diameter of either end of the image capture device230,240. The center axis B1of the image capture device230,240may be defined as a line travelling from a rear of the image capture device230,240to the image-capture side231,241of the image capture device230,240being substantially equidistant from the curved cylindrical sides. When the image-capture side231,241is flat, the length axis B1may be perpendicular to the image-capture side231,241, and when the image-capture side231,241is curved, the length axis B1may be tangential to an apex of the image-capture side231,241.

As discussed above with respect toFIGS. 3A and 3B, the stacked semiconductor package100may be positioned vertically, so that its length axis A1is parallel to the length axis B1of the vertical image-capture unit230. In addition, the length axis A1of the stacked semiconductor package may be co-linear with the length axis B1of the vertical image-capture unit230.

Hereinafter, a process of testing a semiconductor package according to an example embodiment will be described.

The vertical illuminator210and the inclined illuminator220may be simultaneously driven or they may be driven one-at-a-time.

When the vertical illuminator210is driven, light emitted by the vertical illuminator210may pass through the inter-mirror214, be reflected by the beam-splitting mirror212at a right angle, and be transmitted to the measurement target P. The light may be reflected by the measurement target P and the reflected light may pass through the beam-splitting mirror212to be captured by an image capturing unit (not shown) of the vertical image capture unit230, which includes a camera. The captured image may be converted into a digital image signal and transmitted to a controller, which may analyze the digital image signal and determine whether or not the corresponding measurement target P is defective.

That is, the vertical image unit230may process light re-reflected by the measurement target P and produce an image, and may determine the size, shape, and position of the solder ball138based on the image.

When the inclined illuminator220is driven, light emitted by the inclined illuminator220may be irradiated toward the measurement target P from various angles. Part of reflection light that is irradiated to the measurement target P at a predetermined tilt angle may be reflected off of the measurement target P and re-reflected by the reflection mirror242toward the image capturing unit of the inclined image capture unit240. The condensing lens244may condense the light re-reflected by the reflection mirror242, and the optical angle shifter246may compensate for a light path of the condensed light. Thus, the inclined image capture unit240may receive collimated light and may capture an image of the measurement target P.

Accordingly, an image of the measurement target P may be captured at a predetermined tilt angle so that a contact portion between the solder ball138and the ball land140may be tested based on the angled image. Also, it may be determined more accurately whether the solder ball138is bonded to the ball land140using the color camera as the inclined image capture unit240. In other words, a degree of reflow between the solder ball138and the ball land140may be measured based on color information.

As explained thus far, a semiconductor package may suffer a non-wet defect between a solder ball and a ball land due to warping or inclination of the solder ball with respect to the ball land. In this case, the non-wet defect may be detected in a noncontact manner, and an image of the semiconductor package may be captured from various angles, thereby obtaining a substantial stereoscopic image. In particular, semiconductor packages may be tested using color information, thereby enhancing test reliability and simplifying a testing process.

As described above, a semiconductor package testing apparatus according to the present inventive concept may have the following effects.

First, since irradiation light emitted by a vertical illuminator is at a right angle to reflection light reflected by a measurement target, a wider range of information including not only on the shape or position of a solder ball but also peripheral information on generation of particles may be obtained. In particular, information on a bonding state between the solder ball and a ball land, such as a solder joint crack, may be detected based on a vertical image of the measurement target.

Second, an image of a contact portion between the solder ball and the ball land may be captured from various angles so that substantial stereoscopic information on the measurement target may be obtained.

Third, an angled image of the measurement target may be employed to obtain stereoscopic information that cannot be obtained using a vertical image. In this case, information on color reflected from the surface of the measurement target may be extracted, and it may be determined whether or not the solder ball is reliably bonded to the ball land based on the extracted information. As a result, measurement errors may be minimized, and test reliability may be markedly improved.