Flatpack Burn-in Socket

This invention relates to a socket for interconnecting a semiconductor device package to a circuit and more particularly relates to a burn-in socket for testing flatpack semiconductor component packages.

Semiconductor devices such as integrated circuits must be packaged in some form so that the semiconductor components can be attached in a circuit or electronic apparatus. One common means of packaging a semiconductor device is the so-called flatpack package. A flatpack package employs an insulative base surrounding and encapsulating the semiconductor device. Leads are formed extending from the semiconductor device outwardly of the insulative base. In a flatpack package, these leads extend in a planar array from two or more sides of the base. Generally the leads extend outwardly in two directions with each lead being parallel to the adjacent leads.

As with other semiconductor or integrated circuit packages, flatpack packages must generally undergo some sort of testing procedure to ensure that the packages are performing satisfactorily. This is especially true since the yield of semiconductor components does not approach 100 percent. In many cases, burn-in testing is conducted on a statistical basis in which representative samples are subjected to burn-in testing. In other situations, all flat pack packages would be subjected to burn-in testing before actual use. Burn-in testing is generally conducted in large convective ovens capable of maintaining a prescribed temperature for the devices under test for a prescribed period of time. These burn-in tests generally involve the simultaneous testing of a large number of similar or identical semiconductor components. Conventionally, these semiconductor components, such as flatpack packages, are positioned within a standard carrier which is in turn positioned within a burn-in socket. Conventional burn-in sockets for flatpack packages employ an insulative housing having a plurality of spring biased contacts which are normally attached to a printed circuit board by conventional through hole soldered interconnections. These conventional flatpack sockets have singly reversely formed spring loaded contact portions. Typically, these terminals are formed from beryllium copper or beryllium nickel material. The footprint of the contact leads is in a staggered configuration. In order to maintain this staggered configuration, adjacent terminals in conventional flatpack sockets have leads of differing lengths. The contact portion of the terminals normally has a gold plating, whereas the solder tails are tin plate. The insulative housings can be fabricated from a suitable high-temperature plastic material such a polysulfone. The flatpack semiconductor devices are conventionally held within the sockets by a metal cover and interengaging latch. The matal cover is generally pivotally attached to the insulating housing of the conventional sockets and arcuately swings into the closed position after the flatpack package is positioned within the socket housing.

The instant invention represents an alternative flatpack burn-in socket which is especially suitable for use with robotic techniques which will allow the flatpack packages to be inserted into and removed from the packages automatically and in large volume. Furthermore, this invention permits the respective terminals within the flatpack package to be robotically probed to determine if the sockets themselves are properly interconnected to the printed circuit board. Thus an improperly connected socket will not be interpreted as an indication that the flatpack package is defective. The flatpack socket of the preferred embodiment of this invention also employs a terminal configuration in which a significant wipe is accomplished between the terminal and the flatpack leads, thus increasing the reliability of the spring biased interconnection between the lead contact portion and the lead itself. These and other objects of this invention are obtained by a socket having the following characteristics.

This invention, as disclosed in a preferred embodiment, is in the form of a socket for establishing electrical interconnection to a flatpack semiconductor component having a plurality of leads projecting in a planar array from the flatpack base. The socket is especially adaptable to burn-in testing for flatpack semiconductor components. The socket includes an insulative housing. The flatpack semiconductor component is secured on the upper surface of the socket housing with a plurality of terminals positioned within the housing. These terminals are positioned to be in registry with flatpack leads which may be inserted into the housing on a conventional carrier. Each of the terminals includes a contact portion which is doubly reversely formed. The contact portion is deflected during insertion of the flatpack package, and deflection of the doubly reversely formed contact portion results in lateral movement of the portion of the terminal contact in engagement with the flatpack lelads to laterally wipe the flatpack leads.

FIG. 1 is an exploded perspective view of a flatpack socket, flatpack semiconductor component, and flatpack carrier, in which an individual terminal is also exploded for clarity.

FIG. 2 is a perspective view of a flatpack socket mounted on a printed circuit board with the flatpack positioned within the carrier, showing the manner in which the socket terminals can be probed for electrical continuity.

FIG. 3 is a sectional view taken along Section line 3--3 of FIG. 1, showing the relationship of the socket, the flatpack semiconductor component, and the carrier.

FIGS. 4, 5, and 6 are sectional views showing the sequential manner in which the flatpack, when mounted in the flatpack carrier, is positioned within the socket by movement of the flatpack carrier perpendicular to the upper surface of the socket.

FIG. 7 is a schematic view showing the manner in which the latch members are spring loaded.

FIG. 8 is a sectional view showing the configuration of the socket base.

FIG. 9 is a perspective view of a single terminal showing the angular orientation of the terminal relative to the bottom of a housing channel.

The flatpack socket comprising of preferred embodiment of this invention is especially adapted for robotic assembly. Robotic assembly techniques are best implemented if the assembly movements are limited to translational as opposed to rotational movements. Therefore, the flatpack socket 2 has been especially adapted to permit insertion of a flatpack 6, mounted in a flatpack carrier of conventional construction, by translational movement perpendicular to the upper surface of socket 2.

Flatpack socket 2 comprises an insulative housing 14 containing a plurality of separate contact terminals 4 positioned within channel 16 adjacent opposite ends 24 of the insluative housing. The insulative housing 30 can be fabricated from a high temperature plastic material which can be suitable for use under the high temperature conditions encountered in a burn-in test. In the preferred embodiment of this invention, the housing 14 is fabricated of a suitable high-temperature plastic material. Housing 14 comprises a generally prismatic member having opposite ends 24 with sides 26 extending therebetween. The upper surface 28 has a plurality of barriers 36 located adjacent each end 24 of the housing. These barriers 36 form a plurality of side by side channels 16 extending perpendicular to the ends 24 of the housing and generally parallel to the sides 26. The lower surface of the channel 16 is coincident with the upper surface 53 of the probing area, and the barriers 36 extend upwardly from the upper surface. A like plurality of holes 32 extending from the upper surface 28 to the lower surface 30 are each aligned with a corresponding channel 16. The holes 36 are positioned inwardly of the housing and are positioned in a staggered configuration corresponding to that on a conventional printed circuit board used for burn-in test applications. As shown in FIG. 1, an integral post 20 extends upwardly from the upper surface 28 of the housing along one side 26. A pair of similar posts 22 extend upwardly along the opposite side of the housing. As will be described in greater detail hereafter, the positioning of these three posts serve to properly orient a flatpack carrier 12 during assembly of a flatpack semiconductor component 6 into the socket 2.

A plurality of identical contact terminals 4 can each be inserted into a channel 16. Each terminal 4 comprises a single formed member formed of a resilient material such as beryllium nickel. A first elongate portion 4a, of the terminal 4, has a length greater than the distance between the upper surface 28 and lower surface 30 of socket 2 and comprises means for insertion through hole 32 to establish an interconnection with a printed circuit board and with circuits on the printed circuit board. In the preferred embodiment of this invention, this solder leg or solder tail 4a is suitable for through hole solder interconnection to printecd circuit board traces. In the preferred embodiment invention, the terminal 4 is bent through an angle of greater than 90 degrees intermediate its end. The terminal thus forms a portion extending laterally relative to the solder tail portion 4a. This laterally extending portion is spring biased into contact with the upper surface of the insulative housing 30. The laterally extending portion thus tends to remain in contact with the housing during deflection of the terminals. A first reversely formed section 4b is formed adjacent this angle bend defining the inner end of the solder tail 4a. This reversely formed section 4b is arcuately formed through an angle greater than 90 degrees and in the opposite direction from the bend formed between leg 4a. A second reversely formed section 4c is then formed adjacent the section 4b. In the preferred embodiment depicted herein, reversely formed section 4c is again arcuately formed, but is arcuately formed through an angle greater than the arcuate deformation of the first reversely formed section 4b. Reversely formed sections 4b and 4c are mutually reversely formed such that the terminal 4 extends along a serpentine path laterally away from the solder tail portion 4a. A leg portion 4d, contiguous with the second reversely formed section 4c, is positioned closely adjacent the outer portion of the terminal along the arcuate section forming the first reversely formed section 4b. The opposite end 4e of the terminal 4 is contiguous with the leg portion 4d and extends generally colinearly with the portion of the terminal between the first reversely formed portion 4b and the bend forming the end of the solder leg 4a. Terminals 4 are positioned within channels 16 with the solder leg or solder tail portion 4a extending through holes 32. The first and second mutually reversely formed sections define a contact portion of the terminals. This contact portion is located generally within the channels 16, although the second reversely section 4c extends above the upper most ends of barriers 36. Generally the first reversely formed section 4b is located within the channel, whereas the second reversely formed section 4c is positioned above the channel. In the undeflected configurations shown in FIG. 3, all of the second reversely formed section 4c extends above the barriers 36. The end 4e of the terminals is located along the end 24 of the housing 14 and extends laterally beyond the barriers 36. Although the terminals are positioed in a staggered configuration to conform to staggered holes in a conventional burn-in printed circuit board, each of the terminals is of substantially the same length and shape, although the ends 4e of those terminals located closest to the end of the housing are trimmed prior to insertion in the housing.

The conventional flatpack semiconductor components, with which this socket is used, comprise an insulative base 10 having a plurality of leads 8 projecting therefrom in a planar array. The socket 2 is not only suitable for use in testing conventional flatpack semiconductor components, but is especially adapted to use conventional flatpack carriers commonly used to mount flatpack semiconductor components to conventional burn-in sockets. The flatpack carriers are of insulative construction and have an opening 46 intermediate the ends. The plurality of channels 48 extend outwardly thereform and are oriented to receive the flatpack leads 8 when positioned in registry therewith. A plurality of keying grooves are positioned along the sides of the flatpack carrier. Two similar grooves 50 are located along one side, whereas only a single groove 52 is located along the opposite side.

Socket 2 has a pair of latch members 18 located along the ends 24 for engaging the flatpack carrier 12 in which a flatpack semiconductor device is mounted. These latches 18 secure the flatpack carrier and the flatpack to the upper surface 28 of the socket 2. Latches 18 have an obliquely extending catch 40 at their uppermost ends. An arm 42 extends generally perpendicular to the upright portion of the latch 18 and is adapted for engagement with a coiled spring 44 located along the lower surface 30 of the insulative housing. Engagement of the latch member 18 and the coil spring 44 is illustrated in FIG. 7. Coil springs 44 extend generally parallel to the sides 26 of the socket housing and are located within cavities 34 extending adjacent sides 26. Each of the latch members 18 on opposite ends 24 of the socket housing engage each of the two springs 44 extending along each side 26 of the socket housing 14. Since the spring is biased to exert an outwardly directed force on the lower arm 42 of each latch 18, the upper catch 40 is biased inwardly by the action of coil springs 44. Latch members 18 are conventionally secured to the exterior of the housing 14 along the sides 28 to permit pivotal movement of latch members 18.

The positioning of a flatpack semiconductor device 6 mounted in a conventional flatpack carrier 12 on socket 2 is illustrated in sectional views FIGS. 4 through 6. This insertion is done by simple translational movement perpendicular to the upper surface 28 of the socket housing 14. No rotational movement is necessary. The posts 20 and 22 extend upwardly from the socket upper surface 28 and upwardly from the uppermost ends of the channels 18 and barriers 36. It is these posts, 20 and 22, which the flatpack carrier 12 first engages. The two posts 22 located along one side of the housings are positioned for receipt within grooves 50 also located on one side of the flatpack carrier 12. The opposite post 20 engages a single groove 52 along the opposite side of flatpack carrier 12. Note that the height of the post 22 above the uppermost extend of the barriers 36 and channels 16 is significantly greater than the thickness of the flatpack carrier. FIG. 4 shows that the flatpack carrier has essentially been fully engaged with posts 22. As the translational movement of the flatpack carrier towards the socket 2 continues, the flatpack carrier engages the catches 40 and cams the upper part of latches 18 outwardly against the bias of spring 44. Continued downward movement of carrier 12 brings the leads 8 on the flatpack semiconductor component 10 into engagement with the outer part of the second reversely formed portion 4c of terminals 4. As shown in FIG. 5, the second reversely formed section 4c engages the leads 8 prior to complete insertion of the flatpack carrier into the socket 2. As shown in FIG. 5, the leg portion 4d is spaced from the outer part of the first reversely formed section 4b. Continued downward movement of the flatpack carrier 12 causes relative lateral movement of the second reversely formed section 4c, and results in a lateral wipe along the leads 8. Since the leads 8 are supported by the flatpack carrier, this wipe does not damage the leads, but it is sufficient to remove contaminates and result in a better electrical interconnection. When the flatpack carrier 12 is fully inserted, as shown in FIG. 6, the catches 40 on latches 18 engage the upper surface of the flatpack carrier to secure the carrier to the socket 2. Thus, insertion of the flatpack semiconductor component 6 has been accomplished by translational movement only, with the posts 20 and 22 serving to guide this translation of movement and not just to key the flatpack carrier to the socket housing 14.

Excessive deflection of the terminals 4 is prevented by the engagement of leg 4d with the outer part of the reversely formed section 4b as shown in FIG. 6. As shown in FIG. 9, reversely removed section 4b is coined and thus is thinner, having a moment of inertia differing from the remainder of the terminal. Therefore, initial deflection of the terminal will occur in reversely formed section 4b. Continued deflection will bring leg 4d into engagement with reversely formed section 4b. A stiffer spring resists further deformation and imparts a high contact force to the leads despite the relatively large deflection prior to engagement between the two terminal sections.

When the flatpack carrier is fully inserted in the configuration shown in FIG. 6, the ends 4e of the terminals extend laterally beyond the upright latch members 18. Thus, the terminal ends 4e are exposed such that the terminals can be electrically probed. By probing the socket terminals perpendicular to the housing upper surface 28, in this manner, the continuity of the terminals 4 within the housing and to the printed circuit board can be checked independently of the flatpack circuit integrity and independently of the integrity of the contact integrity between the terminal and the flatpack leads 8. Thus, defects due to the socket itself and not due to a failure of the flatpack semiconductor component can be identified. The leads can also be individually probed to permit dynamic electrical testing of the semiconductor device. Thus, the performance of individual inputs and outputs of the semiconductor device can be tested. The facility to probe from above, in this manner, is especially suitable for robotic techniques. In turn, these robotic techniques are especially suited for simultaneously handling a large number of flatpack semiconductor components.

The socket 2, comprising of preferred embodiment of this invention, is easily adaptable for use with flatpack semiconductor components of different sizes. Although intended for use with robotic assembly techniques, it should be understood that this socket could also be assembled by more conventional means. Furthermore, minor modifications could be made to this socket which would not depart from the scope of this invention and would perform in a similar manner. Therefore, the claims directed to this invention should be interpreted as covering not only the structure of the preferred embodiment of the invention, but of equivalents thereto.