RF pin grid array

• US 6,028,497 A
• Filed: 01/28/1998
• Issued: 02/22/2000
• Est. Priority Date: 01/28/1998
• Status: Expired due to Term

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: TRW Inc. (Northrop Grumman Corporation)
• Inventors: Dair, Edwin D., Allen, Barry R., Duprey, Randy J.
• Primary Examiner(s): GENSLER, PAUL L
• Application Number:
  US09/014,556
• Time in Patent Office: 755 Days
• Field of Search: 333/26, 333/246, 333/247, 333/260, 257/664, 257/698, 257/699, 257/728, 439/63
• US Class Current: 333/246
• CPC Class Codes: H01L 23/66 High-frequency adaptations
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2924/3011 Impedance

Abstract

A hermetic RF pin grid array package methodology is described that obviates the need for glass to metal feedthroughs, simplifying construction, improving reliability and reducing the cost of RF multi-chip modules. An array of cylindrical passages (13, 15) through the module'"'"'s base plate (3) are aligned with and receive respective associated conductor pins (7, 9) depending from the module substrate (1). Cylindrical metal shrouds (11) are positioned within some passages (15) combine with associated pins (9) to define coaxial RF transmission lines and support for an external RF coax coupling. Unshrouded pins (7) serve to connect DC to the integrated circuit chips in the module. Waveguide interfaces, if required, are provided by conductive coupling structures patterned on the substrate, suspended over a waveguide (17) formed in or about the baseplate. The compartmentalized seal ring (5) attached to the top surface of the substrate provides a metal framework that divides the interior area, providing individual compartment for the distinct RF circuits in the module, including the integrated circuit chips associated with each such RF circuit.

Claims

1. A multi-chip module, comprising:

a substrate for supporting a plurality of RF electronic circuits;

said substrate comprising a dielectric material, a rigid physical characteristic, and a flat geometry;

said substrate including a first ground plane conductor on an upper surface and a second ground plane conductor on a bottom surface, said second ground plane conductor being connected to said first ground plane conductor to place said ground plane conductors electrically in common;

said substrate further including a first plurality of electrical vias extending through said substrate;

a metal seal ring;

said metal seal ring being attached to an upper surface of said substrate in contact with said first ground plane conductor;

said metal seal ring providing a peripheral wall about an upper surface of said substrate for walling in a predefined region of said substrate'"'"'s upper surface, said seal ring further providing a plurality of subsidiary walls connected to said peripheral wall and located in said predefined region for dividing said predefined region into a plurality of separate compartments;

said first plurality of electrical vias being spacially distributed about said substrate to define a first spacial array of vias, and wherein at least one of said plurality of separate compartments contains at least one of said plurality of electrical vias;

said substrate further including a plurality of electrical transmission lines, said transmission lines being distributed amongst said separate compartments;

at least one of said plurality of transmission lines being electrically connected to respective ones of a first portion of said plurality of electrical vias, each of said transmission lines having a characteristic impedance Z₀ ;

a first plurality of conductive pins of a first predetermined length;

said first plurality of pins having a first end attached to respective ones of said first portion of said plurality of electrical vias, leaving a second end thereof extending from said substrate;

a second plurality of conductive pins of a second predetermined length;

said second plurality of conductive pins having a first end attached to respective ones of a second portion of said plurality of electrical vias, leaving a second end thereof extending from said substrate;

a metal base plate, said metal base plate being positioned in abutment with an underside surface of said substrate in contact with said second ground plane conductor to place said metal base plate, said second ground plane conductor, said first ground plane conductor and said seal ring electrically in common;

said metal base plate including a plurality of passages there through, said passages in said metal base plate being spatially distributed about said base plate in said spacial array, wherein said passages are in alignment with said electrical vias;

said passages in said metal base plate being of a third predetermined length, said third predetermined length being greater than said first and second predetermined lengths, wherein said first and second plurality of conductive pins are received within respective ones of said passages in said metal base plate and said second end of said first plurality of conductive pins is positioned within an associated one of said passages in said metal base plate;

a plurality of metal shrouds, each comprising a hollow cylindrical portion, and a washer shaped end to said cylindrical portion, defining a central circular opening; and

said plurality of metal shrouds being positioned within those of said passages in said metal base plate containing conductive pins from said first plurality of conductive pins for surrounding said conductive pins without physical contact therebetween;

each said shroud and associated conductive pin defining a coaxial transmission line having a characteristic impedance of said Z₀.

2. The invention as defined in claim 1, wherein said metal base plate includes a plurality of waveguide passages for conducting RF energy;

wherein said plurality of compartments defined by said seal ring includes a second plurality of compartments, corresponding in number to said plurality of waveguide passages;

said second plurality of compartments overlying respective ones of said waveguide passages in said base plate;

wherein said substrate that is sandwiched between said seal ring and said base plate includes patterned metal conductors on said top surface of said substrate overlying respective waveguide passages, said patterned metal conductors covering a predetermined area smaller in size than the cross-sectional area of said waveguide passage, leaving a passage through said dielectric substrate for coupling microwave energy through said substrate into a respective waveguide, whereby said patterned metal conductors, said substrate and said respective compartment defines a microstrip line to waveguide transition.

3. The invention as defined in claim 1, wherein each of said first plurality of conductive pins comprise:

a nailhead pin shaped geometry, including;

a nailhead disk shaped portion of a first predetermined diameter and a first predetermined thickness; and

a second cylinder shaped portion of a second predetermined diameter, smaller than said first predetermined diameter, and of a second predetermined length;

said second cylinder portion being continuous with and oriented coaxial with said first disk portion.

4. The invention as defined in claim 3, further comprising:

a plurality of pin attach pads attached to said bottom surface of said substrate, each of said plurality of attach pads being associated with a respective one of said electrical vias;

said attach pads being of a disk shaped geometry;

each said attach pad being oriented coaxial with and in electrical contact with a bottom end of a respective one of said first and second portions of electrical vias;

each said attach pad being of a third predetermined diameter and third predetermined thickness;

said third predetermined diameter being greater than said second predetermined diameter; and

wherein said conductive pins are attached to said electrical vias indirectly through said attach pads.

5. The invention as defined in claim 4, wherein said metal base plate includes a plurality of waveguide passages for conducting RF energy;

wherein said plurality of compartments defined by said seal ring includes a second plurality of compartments, corresponding in number to said plurality of waveguide passages;

said second plurality of compartments overlying respective ones of said waveguide passages in said base plate;

wherein said substrate that is sandwiched between said seal ring and said base plate includes patterned metal conductors on said top surface of said substrate overlying respective waveguide passages, said patterned metal conductors covering a predetermined area smaller in size than the cross-sectional area of said waveguide passage, leaving a passage through said dielectric substrate for coupling microwave energy through said substrate into a respective waveguide, whereby said patterned metal conductors, said substrate and said compartment defines a microstrip line to waveguide transition.

6. A multi-chip module, comprising:

a substrate for supporting a plurality of RF electronic circuits;

said substrate comprising a dielectric material;

said substrate further including a first plurality of electrical vias extending through said substrate;

a metal seal ring;

said metal seal ring being attached to an upper surface of said substrate;

said metal seal ring providing a peripheral wall about an upper surface of said substrate for walling in a predefined region of said substrate'"'"'s upper surface, said seal ring further providing a plurality of subsidiary walls connected to said peripheral wall and located in said predefined region for dividing said predefined region into a plurality of separate compartments;

said first plurality of electrical vias being spacially distributed about said substrate to define a first spacial array of vias, and wherein each of said plurality of separate compartments contains at least one of said plurality of electrical vias;

said substrate further including a plurality of electrical transmission lines, said transmission lines being distributed amongst said separate compartments;

each of said plurality of transmission lines being electrically connected to respective ones of a first portion of said plurality of electrical vias, each of said transmission lines having a characteristic impedance Z₀ ;

a first plurality of conductive pins of a first predetermined length;

said first plurality of pins having a first end attached to respective ones of said first portion of said plurality of electrical vias, leaving a second end thereof extending from said substrate;

a second plurality of conductive pins of a second predetermined length;

said second plurality of conductive pins having a first end attached to respective ones of a second portion of said plurality of electrical vias, leaving a second end thereof extending from said substrate;

a metal base plate, said metal base plate being positioned in abutment with an underside surface of said substrate;

said metal base plate including a plurality of passages therethrough, said passages in said metal base plate being spacially distributed about said base plate in said spacial array, wherein said passages are in alignment with said electrical vias;

said passages in said metal base plate being of a third predetermined length, said third predetermined length being greater than said first and second predetermined lengths, wherein said first and second plurality of conductive pins are received within respective ones of said passages in said metal base plate and said second end of said first plurality of conductive pins is positioned within an associated one of said passages in said metal base plate;

a plurality of metal shrouds, each comprising a hollow cylindrical portion, and a washer shaped end to said cylindrical portion, defining a central circular opening; and

said plurality of metal shrouds being positioned within those of said passages in said metal base plate containing conductive pins from said first plurality of conductive pins for surrounding said conductive pins without physical contact there between;

said metal base plate including a plurality of waveguide passages for conducting RF energy;

said plurality of compartments defined by said seal ring including a second plurality of compartments, corresponding in number to said plurality of waveguide passages;

said second plurality of compartments overlying respective ones of said waveguide passages in said base plate;

said substrate sandwiched between said seal ring and said base plate includes patterned metal conductors on said top surface of said substrate overlying respective waveguide passages, said patterned metal conductors covering a predetermined area smaller in size than the cross-sectional area of said waveguide passage, leaving a passage through said dielectric substrate for coupling microwave energy through said substrate into a respective waveguide, whereby said patterned metal conductors, said substrate and said compartment defines a microstrip line to waveguide transition.