Threaded Structures with Solder Control Features

Abstract

Threaded standoff structures may be provided with features that control the flow of solder. A base structure for a standoff may be formed from a solderphobic material such as brass. A through hole may be formed in the base structure. The base structure may be coated with a solderphilic material such as an inner layer of nickel and an outer layer of tin. A tapping tool may be used to remove the solderphilic material from the opening by tapping threads into the opening, thereby exposing the underlying base metal of the standoff in the opening. During attachment to a substrate such as a printed circuit board, the standoff may be exposed to molten solder. The solderphilic coating on the outer surface of the standoff may attract the molten solder, whereas the solderphobic base metal in the threaded opening may help prevent solder from contaminating the threads in the opening.

Description

BACKGROUND

This relates generally to mechanical structures, and, more particularly, to threaded structures such as threaded standoffs for use in assembling electronic devices.

Threaded structures such as threaded standoffs are often used in assembling electronic devices. For example, a threaded standoff may be used in attaching a component to a printed circuit board.

Standoffs are often attached to printed circuit boards using solder. If care is not taken, molten solder can wick onto portions of the threads in a standoff. This can make it difficult or impossible to insert a screw into the standoff.

It would therefore be desirable to be able to provide improved structures such as improved standoffs and other threaded structures that are exposed to solder.

SUMMARY

Threaded structures such as threaded standoff structures may be provided with features that control the flow of solder. The features may include solderphobic and solderphilic surface regions.

A base structure for a standoff may be formed from a solderphobic material such as brass. An opening may be formed in the base structure. The standoff may be coated with a solderphilic coating such as an inner layer of nickel and an outer layer of tin. The solderphilic coating may be formed on an interior surface and an exterior surface of the standoff. A tapping tool may be used to remove the solderphilic coating from the interior surface of the standoff by tapping threads into the standoff opening. Removing the solderphilic coating from the interior surface may expose the solderphobic base metal of the standoff in the opening.

During attachment of the standoff to a substrate such as a printed circuit board, the standoff may be exposed to molten solder. The solderphilic coating on the exterior surface of the standoff may attract the molten solder, thereby securing the standoff to the substrate. The exposed solderphobic base metal in the threaded opening may help prevent solder from contaminating the threads in the opening, thereby allowing a screw to be fully inserted into the threaded opening.

Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an illustrative electronic device such as a laptop computer with electronic device structures that may be assembled using threaded standoffs in accordance with an embodiment of the present invention.

FIG. 2 is a perspective view of an illustrative electronic device such as a handheld electronic device with electronic device structures that may be assembled using threaded standoffs in accordance with an embodiment of the present invention.

FIG. 3 is a perspective view of an illustrative electronic device such as a tablet computer with electronic device structures that may be assembled using threaded standoffs in accordance with an embodiment of the present invention.

FIG. 4 is a cross-sectional side view of an illustrative electronic device with electronic device structures that may be assembled using threaded standoffs in accordance with an embodiment of the present invention.

FIG. 5 is a cross-sectional side view of a conventional standoff that has been exposed to molten solder during the process of mounting the standoff to a printed circuit board.

FIG. 6 is a cross-sectional side view of a standoff with solderphobic threads in accordance with an embodiment of the present invention.

FIG. 7 is a diagram of an illustrative deposition tool that maybe used to coat a standoff in accordance with an embodiment of the present invention.

FIG. 8 is a diagram of an illustrative electroplating tool that maybe used to coat a standoff in accordance with an embodiment of the present invention.

FIG. 9 is a diagram of an illustrative machining tool that maybe used to form an opening in a standoff in accordance with an embodiment of the present invention.

FIG. 10 is a diagram of an illustrative tapping tool that maybe used to cut threads in the opening of a standoff in accordance with an embodiment of the present invention.

FIG. 11 is a diagram showing illustrative steps involved in forming a standoff with solderphobic threads and a solderphilic exterior surface in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION

Structures such as metal fasteners and other structures are often used in assembling printed circuit boards, electronic components, connectors, and other structures associated with an electronic device. For example, threaded structures such as threaded standoffs, threaded bosses, and threaded nuts may be used in attaching one or more structures together in an electronic device.

Threaded structures such as threaded standoffs may be mounted to a substrate such as a printed circuit board. Threaded standoffs may, for example, be soldered to solder pads on the surface of a printed circuit board. Threaded standoffs may be provided with solder control features such as solderphilic surfaces and solderphobic surfaces.

Illustrative electronic devices that may be provided with threaded structures having solder control features are shown in FIGS. 1, 2, and 3. FIG. 1 shows how electronic device 10 may have the shape of a laptop computer having upper housing 12A and lower housing 12B with components such as keyboard 16 and touchpad 18. Assemblies such as printed circuit boards having threaded engagement structures may be mounted within upper housing 12A and/or lower housing 12B.

FIG. 2 shows how electronic device 10 may be a handheld device such as a cellular telephone, music player, gaming device, navigation unit, or other compact device. In this type of configuration for device 10, housing 12 may have opposing front and rear surfaces. Display 14 may mounted on a front face of housing 12. Display 14 may, if desired, have a display cover layer or other exterior layer that includes openings for components such as button 36 and speaker port 38. Assemblies such as printed circuit boards having threaded engagement structures may be mounted within housing 12.

FIG. 3 shows how electronic device 10 may be a tablet computer. In electronic device 10 of FIG. 3, housing 12 may have opposing planar front and rear surfaces. Display 14 may be mounted on the front surface of housing 12. As shown in FIG. 3, display 14 may have a cover layer or other external layer with an opening to accommodate button 36.

The configurations for device 10 shown in FIGS. 1, 2, and 3 are merely illustrative. In general, electronic device 10 may be a laptop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular telephone, a media player, or other handheld or portable electronic device, a smaller device such as a wrist-watch device, a pendant device, a headphone or earpiece device, or other wearable or miniature device, a television, a computer display that does not contain an embedded computer, a gaming device, a navigation device, an embedded system such as a system in which electronic equipment with a display is mounted in a kiosk or automobile, equipment that implements the functionality of two or more of these devices, or other electronic equipment.

Device 10 may have a housing enclosure such as housing 12. Housing 12, which is sometimes referred to as a case or enclosure, may be formed of materials such as plastic, glass, ceramics, carbon-fiber composites and other composites, metal, aluminum, other materials, or a combination of these materials. Device 10 may be formed using a unibody construction in which most or all of housing 12 is formed from a single structural element (e.g., a piece of machined metal or a piece of molded plastic) or may be formed from multiple housing structures (e.g., outer housing structures that have been mounted to internal frame elements, welded standoffs, engagement structures, engagement member receiving structures, or other internal housing structures).

Device 10 may have one or more displays such as display 14. Display 14 may be a liquid crystal display, an organic light-emitting diode (OLED) display, or other suitable display. Display 14 may include display pixels formed from light-emitting diodes (LEDs), organic light-emitting diodes (OLEDs), plasma cells, electronic ink elements, liquid crystal display (LCD) components, and/or other suitable display pixel structures. Display 14 may, if desired, include capacitive touch sensor electrodes for a capacitive touch sensor array or other touch sensor structures (i.e., display 14 may be a touch screen).

As shown in FIG. 4, device 10 may include electronic components such as printed circuit board 22 and components 40. Components 40 may include integrated circuits or other circuit components, batteries, cameras, compasses, wireless communications circuits, antennas, circuit board connectors such as board-to-board connectors or other circuitry. Components 40 may be mounted on top surface 22T and/or bottom surface 22B of printed circuit board substrate 22.

Printed circuit board 22 and components 40 may be used to run software code for device 10, such as internet browsing applications, voice-over-internet-protocol (VOIP) telephone call applications, e-mail applications, media playback applications, operating system functions, antenna and wireless circuit control functions, etc.

Printed circuit board 22 and components 40 may be used in implementing suitable communications protocols. Communications protocols that may be implemented using printed circuit board 22 and components 40 include internet protocols, wireless local area network protocols (e.g., IEEE 802.11 protocols—sometimes referred to as Wi-Fi®), protocols for other short-range wireless communications links such as the Bluetooth® protocol, protocols for handling cellular telephone communications services, etc.

Printed circuit board 22 may include one or more layers of dielectric and one or more layers of conductor. Printed circuit board 22 may, for example, be a rigid printed circuit board formed form a material such as fiberglass-filled epoxy (e.g., FR4), may be a flexible printed circuit formed from materials such as polyimide (sometimes referred to as a “flex circuit”), or may be formed from other suitable materials or combinations of these materials.

If desired, device 10 may be provided with a structural member such as cowling 24. Some of components 40 may be mounted between printed circuit board 22 and cowling 24. Cowling 24 may be mounted on top of one or more printed circuit board connectors. For example, cowling 24 may be fastened over first and second mating connectors and may help hold the first and second mating connectors together. Printed circuit board connectors may be used in connecting printed circuit board 22 to other printed circuits in device 10 such as a flex circuit.

As shown in FIG. 4, device 10 may include threaded structures such as standoffs 28. Standoffs 28 may be soldered to solder pads on the surface of printed circuit board 22. Standoffs 28 may have threads that receive corresponding threaded screws such as screws 32. Standoffs 28 and screws 32 may be used to assemble structures such as shielding cans, cowlings, housing members, connector structures, and other electronic device structures. In the illustrative configuration shown in FIG. 4, each screw 32 may pass through a hole in cowling 24 and may be received by a threaded opening in standoff 28, thereby attaching cowling 24 to printed circuit board 22.

Threaded structures such as standoffs 28 may be used in assembling any suitable structures. The example of FIG. 4 in which standoffs 28 are used in mounting cowling 24 to printed circuit board 22 over components 40 is merely illustrative.

FIG. 5 is a cross-sectional side view of a conventional standoff mounted to a printed circuit board. As shown in FIG. 5, standoff 280 includes threaded opening 460 in brass body 500. Brass body 500 is coated with solderphilic coating 480. Coating 480 includes an inner nickel layer and an outer tin layer. When standoff 280 is mounted to metal pad 420 on printed circuit board 220, molten solder 520 is attracted to the tin in coating 480. This causes some of solder 520 to wick upwards in region 490 on the outer surface of standoff 280. The presence of the solderphilic tin layer on the surface of the threads in threaded opening 460 also tends to cause solder 520 to wick upwards and over some of the threads in opening 460, as shown by wicked solder portion 440 at the base of opening 460. The presence of solder portion 440 over the threads in standoff 280 can make it difficult or impossible to properly insert a screw into opening 440.

A standoff having a configuration that can help avoid solder contamination in the threaded opening is shown in FIG. 6. As shown in the cross-sectional side view of FIG. 6, standoff 28 may be mounted on metal pad 42 (sometimes referred to as a solder pad) on printed circuit board 22 using solder 52. To prevent solder from wicking over the threads in threaded opening 78, threaded opening 78 may be provided with a solderphobic surface (interior surface 54), whereas the remainder of standoff 28 (e.g., exterior surface 56) may be coated with a solderphilic coating such as solderphilic coating 48.

Surface 54 may be formed by exposing solderphobic brass from base structure 50. Surface 56 may be formed by coating base structure 50 with solderphilic coating 48. Solderphilic coating 48 may, for example, include an inner layer of nickel and an outer layer of tin. Solderphilic coating 48 may attract solder 52 more strongly than solderphobic surface 54.

During soldering operations, solder portion 58 may wick up and over the solderphilic outer surface on the sides of standoff 28 and may wick along the solderphilic outer surface on the bottom of standoff 28, thereby securely mounting standoff 28 to printed circuit board 22. At the same time, solderphobic surface 54 may help prevent solder 52 from wicking onto threads in lower region 60 of opening 78.

Any suitable manufacturing equipment may be used to form threaded structures such as threaded standoff member 28 of FIG. 6. As shown in FIG. 7, coatings such as solderphilic metal coatings may be deposited on the surface of standoff 28 using deposition tool 62. Deposition tool 62 may deposit coating materials 64 from source 66. Deposition tool 62 may use evaporation, sputtering, spraying, dipping, or other physical vapor deposition techniques in applying coatings to standoff 28. Deposition tool 62 may also use chemical vapor deposition techniques and other techniques for applying coatings to standoff 28, if desired.

As shown in FIG. 8, electrochemical deposition techniques may be used in coating standoff 28. For example, electroplating tool 70 may be used in coating standoff 28 with metal layers. During coating, standoff 28 may be lowered in direction 74 until some or all of standoff 28 is immersed in electroplating bath 76 in electroplating vessel 68. If desired, electroplating tool 70 may first plate standoff 28 with an inner layer of nickel and may subsequently plate standoff 28 with an outer layer of tin.

FIG. 9 shows how standoff 28 may be machined using machining tool 82. Machining tool 82 may have drill bits or other bits such as bit 80. Motor 72 may rotate bits such as bit 80 to drill openings such as opening 78 in standoff 28. Machining tool 82 may include stamping tools and other tools that form parts into desired shapes using pressure, laser cutting tools, plasma cutting tools, etc.

The example of FIG. 9 in which a machining tool is used to form an opening in standoff member 28 is merely illustrative. If desired, standoff member 28 may be provided with an opening during an initial manufacturing process. For example, base structure 50 (FIG. 6) may be formed from a casting process in which liquid metal is poured into a mold. The mold may have a hollow cavity shaped such that the resulting solidified part has an opening (e.g., a through hole such as through hole 78 of FIG. 6).

FIG. 10 shows how standoff 28 may be threaded using tapping tool 84. Tapping tool 84 may have a tap such as tap 86. Motor 88 may rotate tap 86 to cut threads on interior surface 54 of standoff 28. In addition to forming threads in opening 78, tapping tool 84 may also be used to remove coatings such as solderphilic metal coatings from interior surface 54 (e.g., tapping tool 84 may be used to cut threads in opening 78 while simultaneously exposing the base material that forms standoff 28).

With one suitable arrangement, standoff 28 may be formed using an approach of the type shown in FIG. 11. As indicated by arrow 90, standoff 28 may initially be a solid part with no openings or holes, as shown by solid base portion 50. Base portion 50 may be formed from a solderphobic material such as brass or other solderphobic materials (e.g., solderphobic metals).

As indicated by arrow 92, opening 78 may be formed in base portion 50 using machining tools such as machining tool 82. As shown in FIG. 11, interior surface 54 may initially be planar or substantially planar (e.g., opening 78 may initially be formed without threads).

As indicated by arrow 94, base portion 50 may be coated with a solderphilic coating such as coating 48 (e.g., an inner layer of nickel followed by an outer layer of tin or other suitable metals). Coating tools 98 may be used in forming solderphilic coating 48 on the surface of base structure 50. Coating tools 98 may include, for example, deposition tool 62 of FIG. 7 or plating tool 70 of FIG. 8. As shown in FIG. 11, all or substantially all of the surface of base portion 50 is coated with solderphilic coating 48 (e.g., coating 48 is formed on both interior surface 54 and exterior surface 56 of standoff 28).

As indicated by arrow 96, threads may be cut on interior surface 54 of standoff 28 using tapping tools such as tapping tool 84. Cutting threads on surface 54 may also remove solderphilic coating 48 from surface 54, thereby exposing base portion 50 in opening 78. Because the tapping process exposes the brass material that makes up base 50, the threads of threaded inner surface 54 of standoff 28 may be solderphobic and may help prevent solder from contaminating threads in opening 78. In contrast, solderphilic coating 48 on exterior surface 56 may encourage solder 52 to wick under the lower surface of standoff 28 and up the edges of standoff 28 to assist in forming a satisfactory bond with solder pad 42 on printed circuit board 22 (FIG. 6) during assembly.

The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention.

Claims

1. A method for forming a threaded standoff comprising:

with a machining tool, forming an opening in a base structure;

with a coating tool, coating a surface of the base structure with a solderphilic coating; and

with a tapping tool, forming threads in the opening while removing the solderphilic coating from the opening.

2. The method defined in claim 1 wherein the solderphilic coating comprises a material selected from the group consisting of: tin and nickel, and wherein removing the solderphilic coating from the opening comprises removing the material from the opening.

3. The method defined in claim 1 wherein the base structure comprises brass and wherein coating the surface of the base structure with the solderphilic coating comprises coating the brass with the solderphilic coating.

4. The method defined in claim 1 wherein the coating tool comprises a deposition tool, wherein the solderphilic coating comprises metal, and wherein coating the surface of the base structure with the solderphilic coating comprises depositing the metal on the surface of the base structure with the deposition tool.

5. The method defined in claim 1 wherein the coating tool comprises an electroplating tool, wherein the solderphilic coating comprises metal, and wherein coating the surface of the base structure with the solderphilic coating comprises electroplating the metal on the surface of the base structure with the electroplating tool.

6. The method defined in claim 1 wherein the base structure comprises brass and wherein removing the solderphilic coating from the opening comprises removing the solderphilic coating to expose the brass within the opening.

7. The method defined in claim 1 wherein the base structure is formed from a first material, wherein the solderphilic coating is formed from a second material, wherein the second material attracts solder more strongly than the first material, and wherein removing the solderphilic coating from the opening comprises removing the second material to expose the first material in the opening.

8. A method for forming a threaded standoff comprising:

forming an opening in a standoff member;

with a coating tool, coating a surface of the standoff member with a solderphilic coating; and

removing the solderphilic coating from the opening by forming threads in the opening with a tapping tool.

9. The method defined in claim 8 wherein the solderphilic coating comprises a material selected from the group consisting of: tin and nickel, and wherein coating the surface of the standoff member with the solderphilic coating comprises coating the surface of the standoff member with the material.

10. The method defined in claim 8 wherein the standoff member comprises brass and wherein removing the solderphilic coating from the opening comprises removing the solderphilic coating to expose the brass in the opening.

11. The method defined in claim 8 wherein the standoff member comprises an interior surface and an exterior surface, wherein the interior surface defines the opening, and wherein coating the surface of the standoff member with the solderphilic coating comprises coating the interior surface and the exterior surface with the solderphilic coating.

12. The method defined in claim 8 wherein forming the opening in the standoff member comprises drilling the opening in the standoff member with a machining tool.

13. The method defined in claim 8 wherein coating the surface of the standoff member with the solderphilic coating comprises coating the surface of the standoff member with the solderphilic coating after forming the opening in the standoff member.

14. The method defined in claim 8 wherein the coating tool comprises a deposition tool, wherein the solderphilic coating comprises metal, and wherein coating the surface of the standoff member with the solderphilic coating comprises depositing the metal on the surface of the standoff member using the deposition tool.

15. The method defined in claim 8 wherein the coating tool comprises an electroplating tool, wherein the solderphilic coating comprises metal, and wherein coating the surface of the standoff member with the solderphilic coating comprises electroplating the standoff member with the metal using the electroplating tool.

16. The method defined in claim 8 wherein the standoff member is formed from a first material, wherein the solderphilic coating is formed from a second material, wherein the first material repels solder more strongly than the second material, and wherein removing the solderphilic coating from the opening comprises removing the second material to expose the first material in the opening.

17. A method for forming a threaded standoff that has a solderphilic surface that is configured to receive solder when attaching the threaded standoff to a solder pad and that has a threaded opening that is configured to receive a screw, the method comprising:

forming an opening in a metal standoff member;

forming the solderphilic surface by coating the metal standoff member with a solderphilic coating; and

removing the solderphilic coating within the opening to expose underlying metal of the metal standoff member by tapping threads into the metal standoff member in the opening.

18. The method defined in 17 wherein the underlying metal comprises a solderphobic material and wherein removing the solderphilic coating within the opening comprises removing the solderphilic coating to expose the solderphobic material in the opening.

19. The method defined in claim 17 wherein the solderphilic coating comprises an inner layer of nickel and an outer layer of tin and wherein forming the solderphilic surface comprises coating the metal standoff member with the inner layer of nickel and the outer layer of tin.

20. The method defined in claim 17 wherein forming the opening in the metal standoff member comprises machining the opening in the metal standoff member with a machining tool before forming the solderphilic surface.