Method of attaching printed circuit boards within an electronic module housing

• US 20040093723A1
• Filed: 11/07/2003
• Published: 05/20/2004
• Est. Priority Date: 10/15/2001
• Status: Active Grant

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Charles G. Turner, Mark Kintis
• Inventors: Kintis, Mark, Turner, Charles G.
• Granted Patent: US 7,162,793 B2
• Time in Patent Office: Days
• US Class Current: 29/830
• CPC Class Codes: H05K 1/0237 High frequency adaptations H05K1/0216 takes precedence
• CPC Class Codes: H05K 2201/10371 Shields or metal cases
• CPC Class Codes: H05K 2203/0173 Template for holding a PCB having mounted components thereon
• CPC Class Codes: H05K 2203/0278 Flat pressure, e.g. for connecting terminals with anisotropic conductive adhesive
• CPC Class Codes: H05K 3/0061 onto a metallic substrate, e.g. a heat sink heat sinks for electric apparatus H05K7/20
• CPC Class Codes: H05K 3/303 Surface mounted components, e.g. affixing before soldering, aligning means, spacing means H05K3/32 takes precedence
• CPC Class Codes: H05K 3/341 Surface mounted components
• CPC Class Codes: Y10T 29/49117 Conductor or circuit manufacturing
• CPC Class Codes: Y10T 29/49126 Assembling bases
• CPC Class Codes: Y10T 29/49128 Assembling formed circuit to base
• CPC Class Codes: Y10T 29/4913 Assembling to base an electrical component, e.g., capacitor, etc.
• CPC Class Codes: Y10T 29/49133 with component orienting
• CPC Class Codes: Y10T 29/49135 and shaping, e.g., cutting or bending, etc.
• CPC Class Codes: Y10T 29/49144 by metal fusion
• CPC Class Codes: Y10T 29/5313 Means to assemble electrical device
• CPC Class Codes: Y10T 29/53252 Means to simultaneously fasten three or more parts
• CPC Class Codes: Y10T 29/53961 with work-holder for assembly

Abstract

Reflow soldering of a variety of circuit boards (9, 11, 15) in a variety of sizes and shapes to assigned locations on the base or carrier (13) of the electronic module housing (3) is simplified by eliminating custom made metal blocks previously used to clamp the circuit boards against the carrier metal. Instead, the solder-backed circuit boards are placed in assigned positions in the module housing and the inside volume of that housing is filled (22) with particulate, such as small beads (17), covering the circuit boards, but leaving the edges of the upstanding metal shields (5 and 7) visible. A plate (21) backed foam sheet (19) is placed over the module housing (24) and clamped down (26), pressing against the beads. The clamped assembly is then heated (28) to reflow the solder, soldering the circuit boards in place.

Claims

1. A method of assembling a circuit board to the carrier wall of the housing for an electronic module, said circuit board containing a bottom layer of a solder material, comprising the steps of:

placing the circuit board onto a predetermined location on the carrier wall with said bottom layer of said circuit board resting on said carrier wall;

depositing particulate on the circuit board and distributing said particulate over at least the upper surface of said circuit board;

applying a force against said particulate, wherein at least some particles of said particulate press said circuit board against said carrier wall; and

reflowing said solder while applying said force against said particulate to attach said circuit board to said carrier wall;

removing said force from said spheres to release pressure on said particulate and said circuit board; and

removing said particulate.

2. The method of assembling a circuit board to the carrier wall of an electronic module as defined in claim 1, wherein said step of applying a force against said particulate includes the steps of:

placing a layer of foam material over said particulate;

placing a layer of rigid metal over said layer of foam material;

applying a clamping force between said layer of rigid metal and said carrier wall of said housing to press said foam material against said particulate.

3. The method of assembling a circuit board to the carrier wall of the housing of an electronic module as defined in claim 1, wherein said step of reflowing said solder includes the steps of:

placing said particulate, said circuit board and said housing into a vapor soldering chamber, and, while maintaining said applied force against said particulate, heating said vapor soldering chamber to raise the temperature of said solder to the eutectic temperature of said solder; and

then terminating said heating.

4. The method of assembling a circuit board to the carrier wall of the housing of an electronic module as defined in claim 1, wherein said housing includes side walls, said side walls together with said carrier wall defining a cavity;

and wherein said step of depositing particulate on the circuit board includes depositing said particulate in a quantity sufficient to fill said cavity.

5. The method of assembling a circuit board to the carrier wall of the housing of an electronic module as defined in claim 1, wherein said particulate comprises material having poor thermal conductivity.

6. The method of assembling a circuit board to the carrier wall of the housing of an electronic module as defined in claim 1, wherein said material having poor thermal conductivity comprises glass.

7. The method of assembling a circuit board to the carrier wall of the housing of an electronic module as defined in claim 1, wherein the particles of said particulate comprise spheres.

8. The method of assembling a circuit board to the carrier wall of the housing of an electronic module as defined in claim 1, wherein the size of the particles of said particulate is substantially less than the length or width of said circuit board.

9. The method of assembling a circuit board to the carrier wall of an electronic module as defined in claim 2, wherein said foam material is compressible, whereby said foam material may compress in locations that press against edges of any upstanding walls in said cavity while also pressing against said particulate.

10. The method of assembling a circuit board to the carrier wall of an electronic module as defined in claim 1, wherein said step of removing said particulate comprises:

applying a vacuum nozzle to said cavity to suck said particulate into a canister.

11. A method of assembling individual circuit boards to the housing of an. electronic module, said circuit boards containing a bottom layer of a solder material and being variegated in size and shape, and said housing of said electronic module containing a bottom wall defining a cavity and containing upstanding internal walls defining a variety of compartments within said cavity, said individual circuit boards being of a size and shape within respective ones of said compartments, comprising the steps of:

placing said circuit boards within respective compartments inside said cavity with said bottom layer of said circuit boards resting on said bottom wall of said module;

filling said cavity with particulate, wherein said circuit boards are covered by said particulate;

pressing against said particulate, wherein at least some portion of said particulate presses said circuit boards against said bottom wall of said module; and

reflowing said solder while maintaining said particulate pressed against said circuit boards to attach said circuit boards to said bottom wall of said module.

12. The method of assembling circuit boards to the bottom wall of an electronic module as defined in claim 11, wherein said particles of said particulate comprise spheres.

13. The method of assembling circuit boards to the bottom wall of an electronic module as defined in claim 11, wherein said step of pressing includes the steps of:

placing a layer of foam material over said particulate;

placing a layer of rigid metal over said layer of foam material;

applying a clamp between said layer of rigid metal and said electronic module to squeeze said layer of foam material against said particulate.

14. The method of assembling circuit boards to the bottom wall of an electronic module as defined in claim 13, wherein said foam material comprises a compressibility characteristic whereby said foam material yields in locations where pressed against the edges of said compartment walls while sufficiently stiff enough to concurrently press against said particulate.

15. The method of assembling circuit boards to the bottom wall of an electronic module as defined in claim 13, wherein said foam material is relatively stiff, and wherein one side of said layer of foam material includes grooves for receiving the edges of said compartment walls to permit portions of said layer to press against said glass balls without interference of said compartment walls.

16. A method of assembling a circuit board to the carrier wall of the housing for an electronic module, said housing including side walls with said side walls together with said carrier wall defining a cavity, and said circuit board containing a bottom layer of a solder material, comprising the steps of:

placing the circuit board onto a predetermined location on the carrier wall with said bottom layer of said circuit board resting on said carrier wall;

depositing glass balls of borosilicate glass in said cavity in a quantity sufficient to fill said cavity and cover said upper surface of said circuit board;

applying a force against said glass balls, wherein at least some glass balls press said circuit board against said carrier wall, said step of applying a force against said glass balls including the steps of;

placing a layer of foam material over said glass balls, said foam material comprising an expanded silicon elastomer;

placing a layer of rigid metal over said layer of foam material;

applying a clamping force between said layer of rigid metal and said carrier wall of said housing to press said foam material against said glass balls; and

reflowing said solder while applying said force against said glass balls to attach said circuit board to said carrier wall, said step of reflowing said solder including the steps of;

placing said glass balls, said circuit board and said housing into a vapor soldering chamber, and, while maintaining said applied force against said glass balls, heating said vapor soldering chamber to raise the temperature of said solder to the eutectic temperature of said solder; and

then terminating said heating;

removing said force from said glass balls release pressure on said glass balls and said circuit board; and

removing said glass balls.

17. Clamping apparatus for clamping circuit boards to the carrier wall of the housing of an electronic module during reflow solder processing to attach said circuit boards to said carrier wall, comprising:

a particulate, said particulate being sufficient in number to fill said housing;

a sheet of foam material, said sheet being sufficient in size to cover an open end of said housing;

a rigid plate, said rigid plate being sufficient in size to cover said sheet of foam material.

18. The clamping apparatus as defined in claim 17, wherein said spheres comprise wherein the particles of said particulate comprise spheres.

19. The clamping apparatus as defined in claim 18, wherein said spheres comprise:

glass balls.

20. The clamping apparatus as defined in claim 19, wherein said glass of said glass balls comprises borosilicate glass and wherein said foam material comprises an expanded silicon elastomer.

21. The clamping apparatus as defined in claim 17, wherein said sheet of foam material includes a surface containing grooves.