Dye-based circuit mount testing

An apparatus may include a housing forming an enclosure having an edge seatable on a printed circuit board (PCB). The enclosure edge may include an edge portion. The housing may be configured to transfer a force applied to the housing to a surface mount component mounted on the PCB to dismount the surface mount component. The apparatus may include a dye inlet formed by the housing and configured to conduct a dye into the enclosure. Another apparatus may include at least one gasket mounted to the enclosure edge to contact the major surface of the PCB adjacent to the surface mount component for forming a seal with the PCB. A method may include enclosing a surface mount component in an enclosure formed in a nozzle apparatus, introducing a dye into the enclosure, and applying a force to the nozzle apparatus to dismount the surface mount component.

BACKGROUND

The present inventions relate to testing interconnections, such as solder joints, to detect defects that may negatively affect the integrity of a joint, and more specifically to dye-based circuit mount testing of solder joints that connect packaged semiconductors to a printed circuit board (PCB) or other substrate.

A semiconductor package assembly, also called a package, is a carrier for one or more integrated circuits. A package may provide leads, pins, and/or other structures to permit electrical, electronic, and/or mechanical interconnections between the packaged integrated circuit and the supporting PCB or other substrate. A surface-mount component (SMC) is a type of package that may be mounted directly to the surface of a substrate, for example, by soldering its leads and/or pins to the PCB. A ball-grid array (BGA) is a type of SMC that replaces the leads and pins with a grid of solder balls placed on the bottom of the package and held in place, for example, by a flux until soldered. BGA packaging enables a high density of solder-joint connections between the package and the substrate. However, a solder-joint connection may exhibit defects, such as cracks, separations, and/or voids, that may negatively affect the electrical, electronic, and/or mechanical properties of the joint.

BRIEF SUMMARY

According to one embodiment, an apparatus may include a housing forming an enclosure having an edge seatable on a major surface of a printed circuit board. The enclosure edge may include an edge portion configured to be positioned adjacent to at least a portion of a perimeter of a surface mount component that is mounted on the major surface of the printed circuit board and received in the enclosure. The housing may be configured to transfer a force to the surface mount component when the force is applied to the housing appropriate to press the edge portion against the portion of the perimeter of the surface mount component, whereby the surface mount component is dismounted from the printed circuit board when a sufficient such force is applied. The apparatus may additionally include a dye inlet formed by the housing and configured to conduct a dye into the enclosure, and thereby onto the surface mount component when the housing edge is seated on the major surface of the printed circuit board with the surface mount component positioned within the enclosure.

According to another embodiment, an apparatus may include a housing forming an enclosure having an edge seatable on a major surface of a printed circuit board. The enclosure edge may include an edge portion configured to be positioned adjacent to at least a portion of a perimeter of a surface mount component that is mounted on the major surface of the printed circuit board and received in the enclosure. The housing may be configured to transfer a force to the surface mount component when the force is applied to the housing appropriate to press the edge portion against the portion of the perimeter of the surface mount component, whereby the surface mount component is dismounted from the printed circuit board when a sufficient such force is applied. The apparatus may additionally include at least one gasket mounted to the enclosure edge to contact the major surface of the printed circuit board adjacent to the surface mount component such that a seal is formed when the gasket is pressed against the major surface of the printed circuit board.

According to a further embodiment, a method may include enclosing a surface mount component mounted on a major surface of a printed circuit board via a nozzle apparatus. The nozzle apparatus may define an enclosure with an opening, the surface mount component being received within the enclosure. The method may additionally include introducing a dye into the enclosure through a passage in the nozzle apparatus to apply the dye to the surface mount component while the surface mount component is enclosed. The method may further include applying a force to the nozzle apparatus in a direction parallel to the major surface of the printed circuit board while the surface mount component is enclosed, the force being sufficient to move the nozzle apparatus against the surface mount component and dismount the surface mount component from the printed circuit board.

DETAILED DESCRIPTION

Referring toFIG. 1, an illustrative embodiment of a nozzle apparatus10is depicted. Nozzle apparatus10may include a housing12with one or more surfaces13. Surfaces13may form at least one enclosure14having an enclosure edge16. The enclosure may be sized to receive a surface mount component that is mounted on a major surface of a printed circuit board. Housing12may be configured to transfer a force from one or more force sources17to the surface mount component when the force is applied to the housing appropriate to press enclosure edge against a portion of a perimeter of the surface mount component, The surface mount component may be dismounted from the printed circuit board when a sufficient such force is applied.

The nozzle apparatus may additionally include at least one dye inlet30, at least one vacuum inlet34, at least one seal40, and/or one or more heaters42. The dye inlet may be formed by (or mounted to) housing12and configured to conduct a dye from one or more dye sources31into enclosure14. Seal40may be mounted to enclosure edge16to form a substantially gas-tight seal when seal40is pressed against a surface, such as a major surface of a printed circuit board (PCB). Vacuum inlet34may be formed by (or mounted to) housing12and configured to be connected to one or more vacuum sources35to draw a vacuum in the enclosure. Heaters42may be mounted to the housing and configured to heat the enclosure. Although nozzle apparatus10is shown to include housing12, dye inlet30, vacuum inlet34, seal40, and heater42, different embodiments of nozzle apparatus10may include different combinations of components, such as the housing and the dye inlet or the housing and the seal.

Referring toFIGS. 2-3, an example of nozzle apparatus10is illustrated. Housing12may generally be a rigid or partially rigid structure that forms enclosure14. Enclosure14may be an interior volume within housing12defined by, for example, walls22or other interior surface of housing12. Walls22of housing12may terminate to form an enclosure edge16configured to conform to and seat against a predetermined surface. For example, to seat against a generally planar surface, enclosure edge16may have a corresponding generally planar profile at the edge or surface adjacent to the planar surface. Enclosure edge16may define an open end or side20of enclosure14, where the internal perimeter at opening20may include an edge portion18of wall22configured to be positioned adjacent to at least a portion of the perimeter of a predetermined object received within enclosure14through opening20. By means of edge portion18positioned adjacent to the perimeter of a received object, nozzle apparatus10may transfer a force applied to housing12to the received object.

For example, housing12may be configured to seat against a major surface52of a PCB50, and enclosure edge16may be configured to receive a surface-mount component (SMC)54that is mounted on surface52. “Surface-mount component” or “SMC” herein includes semiconductor packages, such as a ball-grid-array (BGA). “Surface mount component” or “SMC” herein also may include other components of interest, such as electrical, electronic, or mechanical components, made from materials such as metal, ceramic, and/or plastic that are subject to surface-breaking defects potentially detectable through dye-penetrant inspection, the potential defects occurring on the component itself and/or on its attachment means, such as its soldered connections.

At least a portion of a received SMC54may pass within (or is received by) enclosure14, thereby positioning at least a portion of perimeter56of SMC54adjacent to edge portion18. Applying a force to housing12directed parallel to surface52of PCB50may press edge portion18against at least a portion of perimeter56of SMC54, thereby transferring the force from housing12to SMC54. By applying a sufficient force, SMC54may be dismounted and/or sheared from PCB50.

Edge portion16may be configured such that, when SMC54is received within enclosure14, the edge portion is adjacent to the entire perimeter, in contrast to only a portion of the perimeter, of a predetermined object. For example, edge portion16may be sized and shaped to fit over the entire perimeter18of a particular type of SMC54of a known size and shape. If the perimeter of SMC54is, for example, one inch on each side so that SMC54covers about one square inch of major surface52of PCB50, then edge portion16may have a matching interior perimeter one inch (plus a tolerance) on each side. The tolerance may be a mechanical clearance added to the interior perimeter to allow SMC54to be received within enclosure14without significant binding or interference. The size and shape of the mouth of enclosure14defined by edge portion18may be selected to mate with those of SMC54and/or other object(s) being tested, so that the perimeters of edge portion18and SMC54have a complimentary or part-counterpart relationship (with allowance for clearance). This complimentary relationship may exist even if SMC54or other received object has an oval, circular, polygonal, irregular, and/or other non-square and/or non-rectangular perimeter.

When mounted to a PCB, an SMC stands in relief perpendicular to (or extend perpendicularly from) the major surface of the PCB. For example, if SMC54is a ball-grid array (BGA) soldered to a PCB, then the top side of the BGA (i.e., the side opposite a solder-ball array58) may stand in relief (or extend or be spaced) from the surface of the PCB, where the relief distance or height is the sum of the thickness of the BGA package, the thickness of the solder-ball grid, and any other separations and tolerances. When housing12slips over SMC54, all or part of its relief height is received inside or within enclosure14. The enclosure may be configured to accommodate the relief height, such as by allowing an adequate separation between an interior roof24of enclosure14and a top side57of SMC54so that top side57does not interfere with the interior opening of dye inlet30, vacuum inlet34, and/or other passages and/or components of nozzle apparatus10.

Housing12may provide mechanical support for attached parts of apparatus10, and its form defines negative spaces, such as enclosure14and passages (such as dye inlet30). Housing12may be cast, formed, assembled, and/or otherwise fabricated from suitable rigid material(s). The material(s) used for housing12may have sufficient mechanical strength and/or impermeability to maintain a pressure difference, such as at least a partial vacuum within enclosure14; sufficient mechanical strength to shear off and/or otherwise dismount SMC54from PCB50; adequate resistance to corrosion, dissolution, and/or other detrimental physical and/or chemical interaction with fluids used during use; and/or sufficient thermal conductivity to allow heater42to increase the temperature of enclosure14. Metals, such as aluminum or its alloys, may possess suitable characteristics for fabricating housing12, and facilitate fabrication of holes, passages, threads, and/or other structures. However, other metals, alloys, plastics, and/or other generally rigid materials may possess appropriate properties for fabricating all or part of housing12. Although housing12may be machined from, for example, a single block of an aluminum alloy, it may alternatively be assembled from parts fabricated from other or different materials selected for their respective functional purposes.

Housing12may include at least one dye inlet30, which may be a passage through a wall22of housing12configured to conduct a dye and/or other fluid(s) into enclosure14. The term “dye” herein may include indicator fluids, developers, solvents, colorants, such as dyestuffs, stains, and pigments that may be dissolved, suspended, and/or otherwise conducted by a carrier fluid, and/or other fluids. The term may additionally refer to a substance detectable by any means, such as to inspection under visible or ultraviolet light.

Dye inlet30may be fabricated by, for example, drilling a hole through a wall22, thereby establishing a passage for fluid communication from an external dye source to enclosure14. Dye inlet30may enable the application of dye or other fluid to SMC54when enclosure edge16is seated on surface52of PCB50with SMC54positioned within the enclosure14. For example, when nozzle apparatus10is used for dye-penetrant inspection, a fluid applied to SMC54via inlet30may include a dye, such as machinist's layout fluid; or it may include a developer, such as those used for visible or florescent dyes; or it may include cleaners, such as solvents that remove excess indicator fluids and/or developers from the surface of the article under test, such as an SMC54; or it may include a series or combination of fluids.

Dye inlet30may be used to introduce a dye and/or indicator fluid(s) from one or more dye sources into enclosure14by, for example, pouring the dye into the open dye inlet30(possibly aided by a funnel and/or similar device(s)). A dye may be introduced through inlet30by means of a hose or tube inserted into inlet30. Optionally, a dye fitting, not shown, that fits sealingly into dye inlet30may be used, to which a hose or tube may be connected. Dye inlet30may be a hole with a diameter selected to match the outer diameter of the hose or tube, which may be held in place within dye inlet30by friction, sealant, adhesive, threads, and/or other means. Attaching the other end of the hose or tube to dye source(s)31(shown inFIG. 1) may enable an ongoing supply of dye through inlet30.

Nozzle apparatus10may additionally, or alternatively, include a removable dye inlet cap32, which may be applied to dye inlet30to create a substantially gas-tight closure for the dye inlet and allow enclosure14to hold pressure and/or maintain a vacuum. When installed on or in inlet30, cap22may be held in place by friction, sealant, threads, and/or other means. Removing cap32may permit the application of a dye via dye inlet30.

AlthoughFIGS. 2-3show an example nozzle apparatus10in which dye inlet30passes through a particular wall22of housing12, inlet30may alternatively, or additionally, pass through any wall(s)22of housing12. Additionally, althoughFIGS. 2-3show an example nozzle apparatus with a single inlet30, other embodiments may have multiple inlets30. For example, a nozzle apparatus10used for a procedure that employs more than one fluid, for instance at different stages of a test, may include a distinct inlet30for each distinct fluid, where each inlet30may have its own source of supply and/or suitable means of closure.

Nozzle apparatus10may additionally, or alternatively, include at least one seal40, such as a gasket, mounted on enclosure edge16. The seal may be positioned to contact surface52of PCB50and surrounding opening20of enclosure14. Compressing seal40against surface52of PCB50and/or other substrate may establish a substantially gas-tight seal between housing12and PCB50, for example to allow enclosure14to hold a pressure difference long enough to conduct a testing procedure. When all openings of housing12are sealed by gaskets, caps, and/or other suitable means, enclosure14may function as a vacuum or pressure chamber, with PCB50in effect acting as a wall of enclosure14.

Seal40may be formed from a pliable and potentially replaceable material or member. Seal40may be affixed to enclosure edge16by setting it in a groove cut into enclosure edge16, by a sealant, an adhesive, and/or other suitable means. Because seal40may be exposed to heat and/or to fluids, such as those used for dye-penetrant testing, seal40may be fabricated from a material selected for resistance to heat and to corrosion by those fluids. The nozzle apparatus may, in some embodiments, include multiple seals, such as multiple gaskets mounted concentrically on enclosure edge18.

Housing12may additionally, or alternatively, include at least one vacuum inlet34, which may be a passage through a wall22of housing12configured to allow the attachment of vacuum source(s)35(shown inFIG. 1) and the creation of a vacuum within enclosure14. Vacuum inlet34may be fabricated by, for example, drilling a hole through wall22, thereby establishing a passage in fluid communication with enclosure14. Vacuum inlet34may enable the removal (or addition) of a gas, such as atmospheric air from (or to) enclosure14, and therefore may enable the creation and maintenance of reduced (or increased) pressure.

Vacuum inlet34may support the direct or indirect connection of a vacuum or pressure source to apparatus12. For example, vacuum inlet34may be a hole with a diameter selected to match the outer diameter of a vacuum hose or tube, which may be inserted into inlet34and held in place there by friction, sealant, adhesive, threads, or other suitable means. For example, a tube37(shown inFIG. 1) may be held in place by helical threads cut into the inserted end of the tube and into inlet34, permitting attachment in the manner of a bolt and nut. Attaching the other end of the hose or tube to vacuum source35, such as a vacuum pump, may enable the creation of a vacuum inside enclosure14. In such examples, a valve38spliced into hose or tube37may act as a substantially gas-tight closure for inlet34, allowing inlet34to be sealed when desired.

Nozzle apparatus10may additionally, or alternatively, include a vacuum fitting36, such as a barb-type vacuum fitting, mounted to vacuum inlet34. Fitting36may be held in place by friction, sealant, adhesive, threads, suction, and/or other suitable means to maintain a substantially gas-tight seal between inlet34and fitting36. Fitting36may expedite the attachment of a vacuum or pressure source to apparatus10, for example, by slipping a vacuum hose over the barbed end of a barbed vacuum fitting. A valve anywhere in line between the vacuum source and enclosure14may act as a closure for inlet34and for enclosure14.

AlthoughFIGS. 2-3show a vacuum inlet14that passes through a particular wall22of housing12, inlet34may alternatively, or additionally, pass through any wall(s)22of housing12. Additionally, althoughFIGS. 2-3show a nozzle apparatus10with a single vacuum inlet34, other embodiments may have multiple vacuum inlets34.

Nozzle apparatus10may additionally, or alternatively, include one or more heaters42positioned to transfer heat to enclosure14and therefore to an article under test, such as SMC54. A heater42may be, for example, a cartridge-type heater, which may be a rod-shaped electrical heater suitable for insertion into a hole drilled in a wall22of housing12. One or more holes43for heater(s)42may be drilled parallel to the plane defined by enclosure edge16or otherwise disposed in a wall22of housing12. A heater42may be mounted outside housing12or within enclosure14. Multiple heaters42may be provided. Although nozzle apparatus10is shown to include two heaters42, the nozzle apparatus may include any suitable number of heaters, such as one, three, four or more heaters. Other heat sources may also be used, such as a heated fluid that is disposed in or travels through passageways in the housing.

Nozzle apparatus10may additionally, or alternatively, include at least one suitably shaped handle44attached to housing12. Handle44may expedite manipulation of nozzle apparatus10by its operator and/or by other testing or production equipment. Handle44may be fabricated from, for example, aluminum, its alloys, and/or from other metals, solids, and/or rigid materials. Because some procedures performed by apparatus10may involve heating enclosure14, the material used for handle44may be selected as a heat conductor and/or insulator.

Handle44may be attached to any wall22of housing12by various suitable means. For example, the handle may be attached by matched threads cut into handle44and into a hole provided for the handle in housing12, which may expedite removal of the handle when appropriate. Handle44may be used to apply force to housing12, such as a force directed perpendicular to PCB50, by gripping handle44in a chuck attached to a press. Force applied in that direction may serve to compress seal40to form a substantially gas-tight seal against PCB50. Handle44may be used to apply force directed parallel to major surface52of PCB50, for example, to apply a shearing force to SMC54by pressing edge portion18of housing12against perimeter56of SMC54.

Referring toFIGS. 4-5, the application of various forces on nozzle apparatus10is illustrated. A sealing force70perpendicular to major surface52of PCB50may be applied to nozzle apparatus10, such as to handle44and/or other suitable portions of nozzle apparatus10. The sealing force may compress seal40to aid in the formation of a substantially gas-tight seal. A vacuum may then be created in the enclosure by connecting vacuum inlet34to a vacuum force. Additionally, a shearing force72may be applied to nozzle apparatus10parallel to major surface52of PCB50sufficient to dismount or dislodge SMC54from the major surface. The sealing and/or shearing forces may be applied from one or more forces sources17(shown inFIG. 1), which may include a user, a press, and/or other suitable sources of force.

Referring toFIG. 6, an example of a method100of testing solder joint integrity of a surface mount component is depicted. WhileFIG. 6shows illustrative steps of a method according to one embodiment, other embodiments may omit, add to, and/or modify any of the steps shown in that figure. The method may include enclosing an SMC54mounted on a major surface52of a PCB50via nozzle apparatus10, at102; introducing a dye into the enclosure14through a passage in the nozzle apparatus, at104; and/or applying a force to nozzle apparatus10directed parallel to surface52sufficient to move the apparatus against SMC54and dismount SMC54from PCB50, at106.

Enclosing a SMC54may include positioning nozzle apparatus10adjacent to SMC54, so that the perimeter of SMC54aligns with the perimeter of opening20of enclosure14, then slipping apparatus10over SMC54so that some or all of the relief height of SMC54passes into enclosure14through opening20. When SMC54is received inside enclosure14, at least a portion of the perimeter56of SMC54may be adjacent to at least a portion of edge portion18of enclosure14. Opening20may be configured to fit relatively tightly over the perimeter of SMC54; or opening20may be larger than the perimeter of SMC54in one or more directions, leaving a space between enclosure edge16and SMC perimeter56on one or more sides.

Enclosing SMC54may include enclosing the entire perimeter of SMC54. Additionally, introducing a dye into enclosure14may include pouring or adding a dye fluid through the open dye inlet30. Because inlet30is in fluid communication with enclosure14, the dye may flow into enclosure14and consequently flow onto the SMC54. Nozzle apparatus10may allow the application of a dye to SMC54during the time that SMC54is inside (or received or positioned within) enclosure14. Introducing a dye into the enclosure may occur prior to applying a force to the apparatus.

Applying a force to the apparatus may including pushing or pulling housing12parallel to surface52of PCB50while SMC54is enclosed by enclosure14. This shearing force may be applied directly or indirectly to housing12, for example via handle44. The shearing force may be applied by hand or by a machine, such as a press. Nozzle apparatus10may initially move across surface52in the direction of the force until at least a portion of edge portion18of enclosure14makes contact with at least a portion of perimeter56of enclosed SMC54. After contact occurs, the substantially rigid structure of housing12may transfer the shearing force to SMC54. An initial parallel alignment of the contacting sides of enclosure14with the corresponding sides of SMC54may assist in assuring broad initial contact between edge portion18and perimeter56. Sufficient force may be applied to dismount or shear SMC54away from PCB50, for example, to allow inspection of ball-grid array solder joints for defects exposed by a penetrant dye.

Method100may additionally, or alternatively, include forming a seal between enclosure edge16of nozzle apparatus10and surface52of PCB50, at108. The seal may be formed around SMC54while the SMC is enclosed by enclosure14. Forming a seal may include applying a force to nozzle apparatus10perpendicular to surface52, in effect pressing the nozzle apparatus against PCB50. In an embodiment of nozzle apparatus10that has a seal30, the force may compress seal30to aid the formation of a substantially gas-tight seal. The force may be applied by hand, weights applied to housing12, and/or a machine (such as a press). Sealing enclosure14at enclosure edge16and/or seal40, together with sealing other openings (such as dye inlet30) may subsequently permit the creation of a pressure difference such as a vacuum within enclosure14. The seal may be formed, for example, before, during, and/or after introducing a dye.

Method100may additionally, or alternatively, include evacuating enclosure14while the seal is formed between seal40and surface52of PCB50, at110. Evacuating enclosure14may include connecting a vacuum source, such as a vacuum pump, to vacuum inlet34(such as via fitting36), and then reducing the pressure inside enclosure14relative to ambient pressure. The presence of a vacuum may help draw penetrant dyes into surface defects through capillary action. Drawing a vacuum within enclosure14while it is seated and sealed on surface52may eliminate the need to cut a section out of a PCB prior to inspection, so that the section is small enough to fit in a vacuum chamber. Evacuating the enclosure may occur after introducing a dye.

Method100may additionally, or alternatively, include heating SMC54via one or more heaters42while SMC54is enclosed in enclosure14, at112. The heating may occur after introducing a dye. During dye-penetrant testing, for example, baking SMC54after applying the dye may help harden the dye. Method100may additionally, or alternatively, include inspecting the fractured joint surfaces of SMC54for dye, such as after the SMC has been dismounted by application of the shearing force via the nozzle apparatus, at114.