Electrostatic discharge protection device for semiconductor chip packages

Abstract: An electrostatic discharge (hereafter referred to as "ESD") protection device is disclosed for use with semiconductor chip packaging (hereafter referred to as "SCP". The electrostatic protection device comprises electrically conductive shorting devices (186) that may be removably connected to the SCP during the manufacture to short selected pins (22') from the SCP. The ESD protection devices remain in place to provide ESD protection during all phases of handling and shipping and may be manually removed during final assembly when the SCP is installed in its end product.

Description: This invention relates to an electrostatic discharge (hereafter referred to as "ESD") protection device for various semiconductor chip packages (hereinafter referred to as "SCP") of the type having a plurality of connector pins which are either (a) continuously shorted and then, upon insertion of the connector pins into complementary receptacles, automatically unshorted or (b) continuously shorted until the physical removal of the ESD protection device from the SCP. For a plurality of connector pins of a SCP which mates with a corresponding plurality of receptacles in a connector, typically, a printed circuit board, it is frequently necessary to short together the connector pins of the SCP until they are inserted into complementary receptacles in the connector in order to protect the semiconductor's circuity from ESD. Present ESD protection devices consist primarily of ESD packaging of the SCP in electrically conductive strips, pellets, boxes and plastic tubing which provides effective ESD protection until the user is about to insert the connector pins of the SCP into the complementary receptacles in the connector. At that point, however, the user must remove this ESD packaging from the SCP, thus rendering the SCP vulnerable to ESD, in order to position and insert the connector pins into the receptacles. Accordingly, as the user inserts the connector pins of the SCP into the receptacles, the semiconductor dies housed within these SCP's could be destroyed by ESD and would have to be replaced. Moreover, certain types of SCPs typically EPROMs, UVPROMS, and DRAMs, are plug-in devices which have connector pins which are repeatedly inserted into and then removed from the receptacles. These types of SCPs require ESD protection during the repeated insertions into and removals from the receptacles. Specifically, the connector pins of these SCPs require ESD protection from the moment that their connector pins are removed from the receptacles till their connector pins are again inserted therein. Consequently, a need still exists within the semiconductor chip packaging industry for a true ESD protection device, rather than ESD packaging, which effectively protects the semiconductor die from ESD until the connector pins of the SCP are inserted into the receptacles of the connector and then protects the semiconductor die from ESD again when the connector pins are removed form their respective receptacles. DE-OS-2348630 describes a method and device for protecting devices from damage due to electrostatic charges by shorting the connectors with individual electrically conducting members. JP-A-59-13353 describes an annular conductor slidable across a package to maintain the electrical connection. In accordance with the present invention, an electrostatic discharge protection device in combination with a semiconductor chip package of the type having a top surface and opposite bottom surface and a pair of interface surfaces disposed between the top and bottom surfaces, each interface surface having a plurality of connector pins disposed thereon in a substantially parallel and spaced apart relationship with respect to each other, each connector pin having a portion extending outward from the interface surface and downward at its distal end so as to extend beyond the bottom surface includes: a) a base section having a planar surface overlaid on and secured to the top surface of the semiconductor chip package; and b) a plurality of shorting arms integral to the base section and extending outward therefrom in spaced apart relationship with respect to each other, each shorting arm being in electrical engagement with a connector pin for shorting between the plurality of connector pins via the shorting arms and the base section, each shorting arm having at least a first portion integral to the base section and extending outwardly and downwardly therefrom to define a transverse edge portion at its distal end, the edge portion being moveable into engagement with respect to a respective connector pin; and is characterised in that slots bifurcate select shorting arms so as to separate a pair of lateral edge portions within each select shorting arm from each other, thereby providing each adjacent transverse edge portion with the ability to move independently of the other so as to independently engage the first portion of the connector pin. In one example, an adhesive is provided for securely mounting the base section to the semiconductor chip package. In another example, end portions extend from opposite ends of the base section and integral therewith, each end portion defining a clip which can be removably secured around the top and bottom surfaces of the semiconductor chip package so that the base section is securely mounted to the semiconductor chip package. The present invention thus provides an ESD protection device for use on a SCP which operates in a simple, economical, and effective manner to automatically short a plurality of connector pins together while the SCP is disconnected from a connector. The invention provides an ESD protection device for use on a SCP which may operate to automatically short a plurality of connector pins until the ESD protection device is physically removed from the SCP. The SCPs are of the type that have a top surface, a bottom surface, and, disposed between the top and bottom surfaces, a plurality of interface surfaces each having a plurality of substantially parallel and evenly spaced apart connector pins disposed thereon. Each connector pin comprises a first portion extending outward from the interface surface, a second portion of substantially the same width as the first portion extending in a downward direction, a bent portion interconnecting the first and second portions, a third portion extending downward to its distal end, and an interface portion interconnecting the second and third portions. The ESD protection device comprises a base section which is overlaid on and secured to the top surface of the SCP and a plurality of shorting arms which are integral to the base section. The plurality of shorting arms extend outwardly from the base section in spaced apart relationship with respect to each other. Each shorting arm has a first portion which is integral to the base section and which extends outwardly and downwardly from the base section to define at least one transverse edge portion which is moveable into engagement with the first portion of at least one respective connector pin. Each shorting arm further comprises means for yieldably biasing the respective shorting arm so as to urge the transverse edge portions of adjacent pairs of shorting arms against the first portion of respective ones of the connector pins thereby creating an electrical connection therebetween. Bifurcated shorting arms are used where slots physically separate adjacent transverse edge portions and these slots provide each adjacent transverse edge portion with the ability to move independently of the other so as to independently engage the first portion of their respective connector pin. A pair of clips may be disposed on the ends of the base section or an adhesive may provide this ESD protection device with a secure attachment to the SCP. Preferably, a stiffening rib disposed integrally within the base section provides stiffness to the base section while pull tabs disposed on the ends of the stiffening rib provides for the quick and easy removal of the ESD protection device from the SCP. In the accompanying drawings: Figure 1A is an exploded perspective view of an example of an ESD protection device of this invention disposed above a SCP; and Figure 1B is a perspective view of the ESD protection device shown in Figure 1A mated to the top surface of the SCP shown in Figure 1A. Referring now to Figures 1A and 1B, there is shown generally a SCP-ESD protection device combination comprising an ESD protection device 182 and a SCP 12'. The SCP 12' in one embodiment may comprise a top surface 14', a bottom surface 16', and, between the top and bottom surfaces, a pair of interface surfaces 18' and 20'. A plurality of connector pins 22' and 24', respectively, are disposed on each interface surface 18' and 20', respectively, in a substantially parallel and spaced apart relationship with respect to each other. Each of the plurality of connector pins 22',24' further comprises a first portion 26' extending outwardly from the corresponding interface surface 18',20', a second portion 28' of substantially the same width as the first portion 26' extending in a downward direction, a bent portion 30' interconnecting the first portion 26' and the second portion 28', a third portion 32' narrower than the first portion 26' and extending downward to its distal end 34', and an interface portion 36' which interconnects the second portion 28' and the third portion 32'. As will be readily understood, the SCP 12' may house either a VSLI, LSI, or MSI semiconductor die or dies. The plurality of the connector pins 22',24' are adapted for physical and electrical connection to a connector (not shown), typically a printed circuit board, having a substantially planar surface on one selected side thereof. The connector includes a plurality of elongated receptacles extending inwardly from the planar surface in a substantially parallel spaced apart insulated relationship and in a complementary relationship with respect to the connector pins 22',24' so as to accommodate the ready insertion of the third portion 32' of the connector pins 22',24' into the respective ones of the receptacles. In order to ensure that the connector pins 22',24' are shorted until they are secured in the complementary receptacles, the ESD protection device 182 is provided. The ESD protection device 182 comprises a base section 184 secured to the top surface 14' of the SCP 12' and a plurality of shorting arms 186 which are integral to the base section 184. A pair of clips 188,190 are disposed on the ends of the base section 184 of the ESD protection device 182 which grip the top surface 14' and the bottom surface 16' of the SCP 12' and secure the base section 184 of the ESD protection device 182 to the top surface 14' of the SCP 12'. Alternatively, an adhesive (not shown) disposed on either base section 184 or the top surface 14' of the SCP 12' can also provide the ESD protection device 182 with a secure attachment to the SCP 12'. A stiffening rib 192 is also disposed integrally within the base section 184 and provides stiffness to the base section 184 so as to prevent lateral movement from occurring in the base section 184. Cantilevered end portions of the stiffening rib 192 also extend beyond the corresponding end portions of the base section 184 and define a pair of pull tabs 194,196 which provide for the quick and easy removal of the ESD protection device 182 from the SCP 12'. The plurality of shorting arms 186 extend outwardly from the base section 184 in a spaced apart relationship with respect to each other and in a spaced apart alignment with respect to the plurality of connector pins 22',24'. Each of the plurality of shorting arms 186 has a first portion 198 extending outwardly and downwardly from the base section 184 to define at least one transverse edge portion 200 which is moveable into engagement with the first portion 26' of at least one respective connector pin 22'. As can be seen from Figures 1A and 1B, the shorting arms 186 at the end of the base section 184 define only one transverse edge portion 200 while the intermediate shorting arms 186 each define two transverse edges 200 that engage respectively adjacent connector pins 22',24'. In this manner, each connector pin 22',24' is shorted by being engaged by two transverse edge portions 200 from two adjacent shorting arms 186. This redundancy, as should be readily apparent, operates to substantially improve the reliability of the ESD protection device 182. In Figures 1A and 1B, there are shown bifurcated shorting arms 186 where slots 202 physically separate adjacent transverse edge portions 200. These slots 202 provide each adjacent transverse edge portion 200 with the ability to move independently of the other so as to independently engage the first portion 26' of their respective connector pin 22',24'. The transverse edge portions 200 always electrically interconnect the shorting arms 186 to the plurality of connector pins 22',24', regardless of whether or not the connector pins 22',24' are inserted into the complementary receptacles (not shown) of a connector (not shown) because this embodiment lacks the means for urging the transverse edge portions 200 away from their respective first portions 26'. Thus, only the physical removal of this ESD protection device from the top surface 14' of the SCP 12' by grasping and pulling the pull tabs 194,196 will electrically disconnect the shorting arms 186 from the connector pins 22',24'. The number of connector pins 22',24' on either surface 18',20' to be shorted together by the ESD protection device embodiment 182 need not include all the connector pins 22',24' but may also be limited to any subset of all the connector pins. Moveover, only a subset of all the connector pins 22',24' on just one interface surface 18',20' may be shorted together by this ESD protection device 182 while all the other connector pins 22',24' remain unshorted.

Claims: An electrostatic discharge protection device (182) in combination with a semiconductor chip package (12') of the type having a top surface (14') and opposite bottom surface (16') and a pair of interface surfaces (18', 20') disposed between the top and bottom surfaces, each interface surface having a plurality of connector pins (22') disposed thereon in a substantially parallel and spaced apart relationship with respect to each other, each connector pin having a portion extending outward from the interface surface and downward at its distal end so as to extend beyond the bottom surface, the electrostatic discharge protection device including: a) a base section (184) having a planar surface overlaid on and secured to the top surface of the semiconductor chip package; b) a plurality of shorting arms (186) integral to the base section and extending outward therefrom in spaced apart relationship with respect to each other, each shorting arm being in electrical engagement with a connector pin for shorting between the plurality of connector pins via the shorting arms and the base section, each shorting arm having at least a first portion (198) integral to the base section and extending outwardly and downwardly therefrom to define a transverse edge portion (200) at its distal end, the edge portion being moveable into engagement with respect to a respective connector pin; characterised in that slots (202) bifurcate select shorting arms so as to separate a pair of lateral edge portions within each select shorting arm from each other, thereby providing each adjacent transverse edge portion (200) with the ability to move independently of the other so as to independently engage the first portion (198) of the connector pin (22'). A device according to claim 1, characterised in that the base section further comprises a stiffening rib disposed integrally within the base section, the stiffening rib (192) having end portions which extend beyond the opposite end portions of the base section, each end portion of the stiffening rib defining a tab (194,196) which can be gripped so that the electrostatic discharge protection device can be easily removed from the top surface. A device according to claim 1 or claim 2, characterised by an adhesive for securely mounting the base section to the semiconductor chip package. A device according to claim 1 or claim 2, characterised by end portions extending from opposite ends of the base section and integral therewith, each end portion defining a clip (188,190) which can be removably secured around the top and bottom surfaces of the semiconductor chip package so that the base section is securely mounted to the semiconductor chip package.

Inventors: CRONIN DAVID V, CRONIN, DAVID V.
Applicants: POLAROID CORP, POLAROID CORPORATION
Application year: 1992
Main classification: H01L23
IPC codes: H05F3, H01L23