Positive retention chip carrier

Abstract: A carrier for an integrated circuit (IC) can (10) has a plurality of low profile symmetrically distributed flexible arms (30) projecting from the carrier base (21) for engaging a flange (16) on the perimeter of the can (10). The low profile of the flexible arms (30) enables information to be printed on the side of the can (10) while it is in the carrier. The symmetrical distribution of the flexible arms (30) imparts an even load upon the can (10) to prevent bending of the leads (12). The carrier base (21) has round holes (38) for receiving electrical leads (12) projecting from the can (10) to minimize the scraping of the leads (12) during insertion and removal of the can (10) from the carrier.

Description: This invention relates to a carrier for retaining an integrated circuit (IC) chip in place during final manufacturing and testing of the chip. More particularly, it relates to a carrier for an IC chip having a cylindrical can body with a number of electrical leads projecting from the bottom of the can in a circular pattern. Carrier devices are known for integrated circuit (IC) chip cans wherein the electrical leads projecting from the bottom of the can extend through D-shaped holes in the base of the carrier. These holes retain the leads in place. However, the use of such D-shaped holes results in bending or scraping of the soft solder electrical leads during manual or machine insertion and removal of the can from the carrier. Other carrier devices are known in which a single arm extending from the carrier is snapped over a flange on the lower perimeter of the can to keep it in place. FIG. 1 is a cross-sectional view of a typical prior art carrier for a can-type IC chip having such a single arm. In FIG. 1 an IC can 10 has electrical leads 12 extending from its lower end 14, a stand-off 15 projecting from its lower end, and a flange 16 on the perimeter of lower end 14. Can 10 is retained in the carrier by a single flexible arm 30 having a hook 19 on its arm end 20 projecting therefrom that engages flange 16. Leads 12 are received by holes 13 in a tapered section 18 and in a base 21. A tapered first section 18 projects from base 21 and has a flat top end 22 upon which stand-off 15 of can 10 sits. Base 21 has an upper cylindrical base section 24 and a lower cylindrical base section 26. A platform 28 attached to base 21 at the junction of upper base section 24 and lower base section 26 is used to stabilize the carrier during manufacturing and testing procedures. A major disadvantage with carriers like the one depicted in FIG. 1 is that single flexible arm 18 places an unbalanced load on can 10, causing the soft solder leads 12 to bend. Leads 12 normally are in a circular pattern that is concentric to the circumference of cylindrical can 10. Prior art devices bend these leads and thus disrupt this concentricity. After the can has been removed from the carrier, the leads typically must be laboriously, manually straightened to reestablish this concentricity before the can may be used in other operations. A second disadvantage of such prior art devices like the one depicted in FIG. 1 is that flexible arm 18 extends too far above the upper surface 17 of flange 16 and thereby obscures a portion of the can body so that identifying information cannot be printed on the side of can 10 while it is in the carrier. Other IC chip carriers are known for flat pack or DIP chips. In U.S. Patent No. 4,379,505 issued April 12, 1983 to Alemanni, and U.S. Patent No. 4,591,053 issued May 27, 1986 to Alemanni, four resilient retaining fingers are used to retain the flat pack by contacting its outermost leads. The disadvantage of this approach is that it may bend or otherwise harm the soft leads. U.S. Patent No. 3,746,157 issued July 17, 1973 to L'Anson discloses a carrier for retaining a flat pack using a snap-in retaining clip, the underside of which is plated with a conductor material such as aluminum. When the retaining clip is in place, this undersurface bridges the conductors of the flat pack, shorting them to one and other. Of course, this approach is not suitable for operations where the leads should not be shorted. Other carriers are known for retaining flat packs and DIPs. See U.S. Patent No. 4,556,145 issued December 3, 1985 to Putnam; U.S. Patent No. 3,892,312 issued July 1, 1975 to Tems; and U.S. Patent No. 3,652,974 issued March 28, 1972 also to Tems. However, none of these carriers is suitable for retaining a can-type body. United States patent US-A-3,516,044 discloses a carrier for a transistor outline semiconductor device with a carrier base structure supporting funnel-like lead entrances adjacent the several openings extending through the base structure, in such a way that the device may be manipulated and operated upon by standard equipment for handling integrated circuit devices. United States patent US-A-3,163,393 discloses a component holder means mountable upon a mounting board and comprising: receptacle means having a cylindrically shaped side wall and closed at one end and open at the other end; said cylindrically shaped side wall of said receptacle means comprised of arcuate segments separated one from the other by slots cut through said cylindrically shaped side wall and running axially along the length of said side wall and extending through the closed end of said receptacle means; the outside surface of said closed end of said receptacle means being generally concave in shape; and fastening means extending outwardly from said closed end and substantially along the axis of said receptacle means and constructed to secure said component holder means to said mounting board. It is a feature of the present invention to provided an IC chip carrier for a cylindrical can that eliminates the scraping of the soft solder leads of the chip during insertion and removal of the chip from the carrier. It is another feature of the present invention to provide an IC chip carrier for a can that eliminates the bending of the soft solder electrical leads of the chip while the chip is retained in the carrier and retains the concentricity of the circular lead pattern with the circumference of the can. It is yet another feature of the present invention to provide an IC chip carrier which allows information to be printed on the side of the can while it is retained in the carrier. It is yet another feature of the present invention to provide an IC chip carrier that securely retains the chip during manufacturing and testing operations. According to the present invention there is provided a carrier for an integrated circuit (IC) can, said can having a lower end, a plurality of electrical leads extending from the lower end, a stand-off projecting from the lower end, a flange around the perimeter of the lower end, said flange having an upper surface, and a surrounding wall extending upward from the flange, the carrier comprising: a base having a plurality of openings to receive said plurality of leads; a support section projecting from the base. the support section having a top end for supporting the stand-off to limit the inward position of a can when it is inserted into the carrier, and a plurality of openings to receive said plurality of leads; and at least three flexible arms projecting from the base and arranged in a symmetrical configuration around the support section to flex in opposition to each other and to retain an IC can inserted therebetween; wherein the arms are for releasably retaining an IC can by virtue of the end of each arm having an inward projection with a lower surface which is arranged to abut against the upper flange surface of an IC can when inserted between the arms to prevent upward movement of the can, said projections extending inwardly from their respective arms by about 0.12 - 0.25mm (0.005 - 0.010 inch), said projections being tapered so that said arms terminate not more than 0.08mm (0.003 inch) above said lower projection surfaces, whereby substantially the entire surface of said surrounding wall is exposed for printing and said arms avoid substantial obstruction to the placement of printed information on said surrounding wall while the can is retained in the carrier, said projections bearing against the flange of an IC can when the can is inserted between or removed from said arms to flex said arms backward to permit the IC can to be admitted or released. These and other features and advantages of the invention will be apparent to those skilled in the art from the following detailed description of preferred embodiments, taken together with the accompanying drawings, in which: FIG. 1 is a cross-section of a typical prior art carrier for an IC can-type chip. FIG. 2 is a perspective view of a carrier according to the present invention. FIG. 3 is a top view of a carrier according to the present invention. FIG. 4 is a cross-section of the carrier depicted in FIG. 3, taken along line 4-4. FIG. 5 is an exploded view of the flexible arm according to the present invention. FIG. 2 is a perspective view of an integrated chip (IC) carrier according to the present invention. In FIG. 2, an IC can 10 has electrical leads 12 extending from its lower end 14 in a circular arrangement that is concentric with the circumference of cylindrical can 10. Can 10 also has a flange 16 on the circumference or perimeter of its lower end 14. Can 10 is retained in the carrier by a plurality of flexible arms 30, each of which has an arm end 32 and a hook 34 projecting from arm end 32 for engaging flange 16. Hook 34 engages flange 16 to retain the can in the carrier. Flexible arms 30 are symmetrically arranged around the circumference of can 10 to impart an even load upon can 10 when the can is retained in the carrier. Three or more arms 30 may be used to engage flange 16, as long as they are symmetrically distributed around the circumference of the can. This symmetrical distribution of the forces imparted on the can by arms 30 minimizes the bending of electrical leads 12 while the can is in the carrier. The concentricity between the circular lead pattern and the outer circumference of the can is thereby retained, obviating the laborious manual process of straightening the bent leads after the can is removed from a prior art IC chip carrier that imparts an uneven load upon the can, like the carrier depicted in FIG. 1. Referring again to FIG. 2, leads 12 are received by holes 38 (not shown) in a tapered first section 18 and in a base 21. Tapered section 18 projects from base 21 and has a flat top end 22 (not shown) upon which rests a stand-off 15 (not shown) attached to lower end 14 of can 10. Base 21 has an upper cylindrical base section 24 and a lower cylindrical base section 26. A flat platform 28 attached to base 21 at the junction of upper base section 24 and lower base section 26 is used to stabilize the carrier during manufacturing and testing procedures. FIG. 3 depicts a top view of an IC chip carrier according to the present invention. In FIG. 3 four arms 30 project from the base and are symmetrically arranged to impart an even load upon the can (not shown). For a typical IC can held in place by 4 arms, the opposing arms 30 are about 8.89 - 9.14mm (0.350 - 0.360 inches) apart, with 9.14mm (0.360 inches) being a preferred distance. Tapered first section 18 has a flat top end 22. Tapered section 18 has a plurality of round holes 38 distributed in a circular pattern for receiving the electrical leads projecting from the lower end of the can. Holes 38 are round, unlike the D-shaped holes in prior art devices, to minimize the bending and scraping of the soft solder leads during insertion and removal of the can from the carrier. FIG. 4 is a cross-sectional view of the carrier depicted in FIG. 3, taken along line 4-4. In FIG. 4, electrical leads 12 projecting from the lower end 14 of can 10 are received by a plurality of holes 38 in tapered first section 18, upper cylindrical base section 24, and lower cylindrical base section 26. Stand-off 15 projecting from the lower end 14 of can 10 sits upon the flat top end 22 of tapered section 18 when can 10 is retained in the carrier. First section 18 may be of a variety of shapes, including a cone or a pyramid. FIG. 4 depicts another important feature of the present invention, namely that arms 30 are designed to have a low profile so that their arm ends 32 do not extend substantially above upper surface 17 of flange 16. In a preferred embodiment, arm end 32 extends between 0.08 and 0.53mm (0.003 - 0.021 inches) above the upper surface of flange 16, with 0.08mm (0.003 inches) being the preferred distance. The amount of this extension depends upon the height of stand-off 15, which varies between about 0.43 - 0.89mm (0.017 - 0.035 inches) from can to can. The purpose of this low profile is to permit information to be printed on the side of a can while the can is retained in the carrier. The high profile of arm end 20 in the prior art device depicted in FIG. 1 prevents information from being printed on the side of the can while the can is in the carrier. The shape of flexible arms 30 is more clearly shown in the exploded view depicted in FIG. 5. In FIG. 5 a flexible arm 30 engages flange 16 of can 10 by means of arm end 32 having a hook 34 projecting therefrom. Hook 34 may have a variety of shapes as long as it has a low profile as discussed above. In a preferred embodiment, hook 34 has the shape of an isosceles triangle, with the angle of the vertex farthest away from arm end 32 being about 30°. Hook 34 projects from arm end 32 between 0.12 - 0.25mm (0.005 - 0.010 inches). The preferred length of the projection is 0.12mm (0.005 inches). FIG. 5 also depicts the low profile design of arm 38 as discussed in connection with FIG. 4 above. While particular embodiments of the invention have been shown and described, numerous modifications and alternate embodiments will occur to those skilled in the art. Accordingly, it is intended that the invention be limited only by the following claims.

Claims: A carrier for an integrated circuit (IC) can (10), said can having a lower end (14), a plurality of electrical leads (12) extending from the lower end (14), a stand-off (15) projecting from the lower end (14), a flange (16) around the perimeter of the lower end (14), said flange having an upper surface (17), and a surrounding wall extending upward from the flange, the carrier comprising: a base (21) having a plurality of openings (38) to receive said plurality of leads (12); a support section (18) projecting from the base (21), the support section having a top end (22) for supporting the stand-off (15) to limit the inward position of a can when it is inserted into the carrier, and a plurality of openings (38) to receive said plurality of leads (12); characterised by at least three flexible arms (30) projecting from the base (21) and arranged in a symmetrical configuration around the support section (18) to flex in opposition to each other and to retain an IC can (10) inserted therebetween; wherein the arms are for releasably retaining an IC can by virtue of the end (32) of each arm (30) having an inward projection (34) with a lower surface which is arranged to abut against the upper flange surface of an IC can when inserted between the arms (30) to prevent upward movement of the can, said projections (34) extending inwardly from their respective arms (30) by about 0.12 - 0.25mm (0.005 - 0.010 inch), said projections (34) being tapered so that said arms (30) terminate not more than 0.08mm (0.003 inch) above said lower projection surfaces, whereby substantially the entire surface of said surrounding wall is exposed for printing and said arms (30) avoid substantial obstruction to the placement of printed information on said surrounding wall while the can is retained in the carrier, said projections (34) bearing against the flange (16) of an IC can when the can is inserted between or removed from said arms to flex said arms backward to permit the IC can to be admitted or released. The carrier of claim 1, wherein said holes (38) are arranged in said base (21) and in said support section (18) in matching substantially circular patterns. The carrier of claims 1 or 2, wherein said holes (38) are substantially round. The carrier of claims 1, 2 or 3, wherein said support section (18) is substantially conical in shape. The carrier of claim 1, 2 or 3, wherein said support section (18) is a pyramid. The carrier of any of the preceding claims, wherein said base (21) is substantially cylindrical. The carrier of any of the preceding claims, further comprising: a platform (28) connected to the base (21) and projecting therefrom. The carrier of any of the preceding claims, wherein said arms (30) and the portion of the base (21) from which they extend conform to a cylinder when retaining an IC can (10). The carrier of claim 8, wherein the width of each of said arms (30) is such that the total width of all arms occupies a minor portion of the circumference of said cylinder. The carrier of any of the preceding claims, wherein said arms (30) have uniform thicknesses below said projections (34). The carrier of any of the preceding claims, wherein both the upper and lower surfaces of said projections (34) are tapered.

Inventors: MORTON WILLIAM D JR, MORTON WILLIAM D. JR.
Applicants: PRECISION MONOLITHICS INC, PRECISION MONOLITHICS INC.
Application year: 1989
Main classification: H05K7
IPC codes: H05K7, H01L21, G01R31