A printed circuit board including an obstructive structure

Abstract

A printed circuit board (140) including an obstructive structure (140o) is provided. The printed circuit board (140) comprises a first dam (142o-l) proximate a first conductive pad (140p) of the printed circuit board (140) and a second dam (142o-2) proximate a second conductive pad (140p) of the printed circuit board (140). The first dam (142o-l) and the second dam (142o-2) are configured to prevent obtrusions from migrating into a component-board interstitial space (180).

Description

[0001] AN OBSTRUCTIVE STRUCTURE

[0002] TECHNICAL FIELD

[0003] The embodiments described below relate to printed circuit boards and assemblies and boards and, more particularly, to an obstructive structure for the printed circuit boards and assemblies.

[0004] BACKGROUND

[0005] Printed circuit assemblies (PCAs) are sometimes subjected to dielectric withstand testing, sometimes referred to as “hipot” testing, to ensure electrical safety and isolation. The production of PCAs can introduce contaminants between joints of a component that can result in failures during hipot testing if adequate cleaning is not performed. The use of slots in the printed circuit board (PCB) or through hole components can reduce the chance of contaminants affecting hipot testing and / or provide additional creepage distance to minimize failures. However, mechanical design restrictions and high density board layouts may prevent the use of through hole components and PCB slots. Accordingly, there is a need for an obstructive structure between joints of a printed circuit component.

[0006] SUMMARY

[0007] A printed circuit board including an obstructive structure is provided. According to an embodiment, the printed circuit board comprises a first dam proximate a first conductive pad of the printed circuit board and a second dam proximate a second conductive pad of the printed circuit board. The first dam and the second dam are configured to prevent obtrusions from migrating into a component-board interstitial space.

[0008] A method of forming the printed circuit board including an obstructive structure according to the foregoing is provided.

[0009] A printed circuit assembly including an obstructive structure is provided.

[0010] According to an embodiment, the printed circuit assembly comprises the printed circuit board of the foregoing and a component bonded with the first conductive pad and the second conductive pad of the printed circuit board. The first dam is proximate a firstjoint of the component and the second dam is proximate a second joint of the component.

[0011] According to an aspect, a method of forming the printed circuit assembly according to the foregoing.

[0012] According to an aspect, a vibratory meter including an obstructive barrier comprises a sensor assembly and a meter electronics communicatively coupled with the sensor assembly, the meter electronics comprises the printed circuit assembly of the foregoing.

[0013] ASPECTS

[0014] According to an aspect, a printed circuit board including an obstructive structure comprises a first dam proximate a first conductive pad of the printed circuit board and a second dam proximate a second conductive pad of the printed circuit board. The first dam and the second dam are configured to prevent obtrusions from migrating into a component-board interstitial space.

[0015] Preferably, at least one of the first dam and the second dam extends from a surface of a printed circuit board to a component proximate plane of the componentboard interstitial space.

[0016] Preferably, the at least one of the first dam and the second dam extending from a surface of a printed circuit board comprises the at least one of the first dam and the second dam extending from one of a surface of the mask and a surface of a substrate of the printed circuit board.

[0017] Preferably, the at least one of the first dam and the second dam extending to the component proximate plane of the component-board interstitial space comprises the at least one of the first dam and the second dam one of abutting and adj acent the component proximate plane of the component-board interstitial space.

[0018] Preferably, the at least one of the first dam and the second dam is comprised of at least one of a mask layer and a silkscreen layer.

[0019] Preferably, the at least one of the first dam and the second dam has a substantially elongated rectangular shape having a longitudinal axis substantially parallel with the first conductive pad and the second conductive pad.Preferably, the printed circuit board further comprises at least a third dam and a fourth dam disposed between the first dam and the second dam.

[0020] Preferably, the third dam and the fourth dam disposed between the first dam and the second dam are configured to prevent the obtrusion from extending into the component-board interstitial space.

[0021] Preferably, the at least one of a pair of the first dam and the second dam and a pair of the third dam and the fourth dam are equally spaced from a component midline parallel to and equally spaced from the first conductive pad and the second conductive pad of the printed circuit board.

[0022] Preferably, the obstructive structure further comprises at least one relief disposed between the first dam and the second dam.

[0023] Preferably, the obstructive structure further comprises a first proximate relief proximate the first conductive pad and a second proximate relief proximate the second conductive pad.

[0024] Preferably, the first dam and the second dam being configured to prevent obtrusions from migrating into a component-board interstitial space comprises the first dam and the second dam being configured to prevent a flux from wicking along board facing surface of a component.

[0025] According to an aspect, a method of forming the printed circuit board including an obstructive structure according to the foregoing.

[0026] According to an aspect, a printed circuit assembly comprises the printed circuit board of the foregoing and a component bonded with the first conductive pad and the second conductive pad of the printed circuit board. The first dam is proximate a first joint of the component and the second dam is proximate a second joint of the component.

[0027] Preferably, the at least one of the first dam and the second dam extend from a surface of a printed circuit board to a surface of the component defining the componentboard interstitial space.

[0028] Preferably, the at least one of the first dam and the second dam extending to the surface of the component defining the component-board interstitial space comprises the at least one of the first dam and the second dam one of abutting and being proximate the surface of the component defining the component-board interstitial space.According to an aspect, a method of forming the printed circuit assembly according to the foregoing.

[0029] According to an aspect, a vibratory meter including an obstructive barrier comprises a sensor assembly and a meter electronics communicatively coupled with the sensor assembly, the meter electronics comprises the printed circuit assembly of the foregoing.

[0030] BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The same reference number represents the same element on all drawings. It should be understood that the drawings are not necessarily to scale.

[0032] FIG. 1 shows a printed circuit assembly 10 including an undesirably reduced creepage distance due to a contaminants CT being attached to wicked flux FL.

[0033] FIGS. 2 and 3 show a printed circuit assembly 100 including an obstructive structure 140o.

[0034] FIG. 4 shows an enlarged view of the printed circuit assembly 100 described with reference to FIGS. 2 and 3 where section view cross hatching and the mask and silkscreen backdrop are omitted for clarity.

[0035] FIG. 5 shows a method 500 of forming a printed circuit board including an obstructive structure, such as the printed circuit boards described above.

[0036] FIG. 6 shows a method of forming a printed circuit assembly including the obstructive structure.

[0037] FIG. 7 shows an electronics device 700 including an obstructive structure.

[0038] FIG. 8 shows a vibratory meter 805 comprising an exemplary electronics device.

[0039] DETAILED DESCRIPTION FIGS. 1 - 8 and the following description depict specific examples to teach those skilled in the art how to make and use the best mode of embodiments of an obstructive structure. For the purpose of teaching inventive principles, some conventional aspects have been simplified or omitted. Those skilled in the art will appreciate variations from these examples that fall within the scope of the present description. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple variations of the obstructive structure. As a result, the embodimentsdescribed below are not limited to the specific examples described below, but only by the claims and their equivalents.

[0040] FIG. 1 shows a printed circuit assembly 10 including an undesirably reduced creepage distance due to a contaminants CT being attached to wicked flux FL. As shown in FIG. 1, the printed circuit assembly 10 is comprised of a component 12 including a component body 12b and conductive terminals 121. The conductive terminals 121 are bonded to a printed circuit board 14. The printed circuit board 14 is shown as being comprised of a substrate 14s, conductive pads 14p, conductive traces 14t, and masks 14m. The component 12 is affixed to the printed circuit board 14 using a conductive filler 16r, which as shown is solder. The conductive terminals 121, conductive pads 14p, and conductive filler 16r form joints 16 of the component 12. A component-board interstitial space 18 is shown as being between and being defined by the component body 12b and the printed circuit board 14 and two joints 16 of the component 12.

[0041] In printed circuit assembly manufacturing the conductive joint pads and traces 14p, 14t may be formed onto a substrate using, for example, a deposition and etch process, although any suitable method may be employed, such as shaped deposition, painting, spraying, etc. The substrate 14s can be a planar dielectric comprised of one or more insulating materials, such as epoxy resin, glass fiber weave, ceramics, polymers, and / or the like. The substrate 14s may be rigid and / or flexible. The conductive pads and traces 14p, 14t are comprised of a conductor, which may include copper, silver, gold, etc., or a mix of conductors. The conductor is not limited to metals and may be comprised of non-metallic materials, such as, for example, superconductive ceramics, carbon nanotube structures, etc.

[0042] During the printed circuit assembly manufacturing, a component 12 may be placed onto the substrate 14s. The conductive filler 16r may comprise one or more conductive substances that binds the component 12 to the conductive pads 14p. The conductive filler 16r may be any suitable material, such as a mixture of tin and lead, conductive epoxies, brazing, etc. The conductive filler 16r may include or be combined with flux that can flow when subjected to high temperatures. For example, solder paste may include flux in which solder particles are suspended. It should be appreciated that the conductive filler 16r may or may not be combined with the flux. The conductivefiller 16r may be applied at elevated temperatures to, in the example of solder, melt the tin-lead mixture so that the solder flows between and / or about conductive terminals 121 of the components and the conductive pads 14p on the substrate 14s.

[0043] To prevent the conductive filler 16r from displacing away (e.g., surface flow, wicking, etc.) from the conductive pads 14p and conductive terminals 121 of the component 12, the mask 14m can be layered over the conductive traces 14t and / or the substrate 14s. The conductive pads 14p to which the component 12 is affixed are left exposed. The mask 14m can prevent the conductive filler 16r from, for example, displacing to an adjacent conductive pad of another component. The mask 14m may also serve as a dielectric layer over the conductive traces 14t to prevent an inadvertent joint with the conductive traces 14t.

[0044] When the component 12 is affixed to the conductive pads 14p, the conductive filler 16r and / or fluxes may wick along a bottom surface of the component 12 to form the wicked fluxes FL. Additionally, or alternatively, contaminants CT may migrate into the component-board interstitial space 18 during the printed circuit assembly manufacturing process. For example, some cleaning process may apply a liquid that suspends a particle smaller than the component-board interstitial space 18. The particle may inadvertently migrate and lodge in the component-board interstitial space 18. Such wicking, contaminants, materials, etc., when undesirably present and / or extending into the component-board interstitial space 18, may collectively be referred to as componentboard interstitial space obtrusions or simply obtrusions.

[0045] When the obtrusions are not present, the component-board interstitial space 18 can have sufficient dielectric strength so as to not experience a dielectric breakdown. However, the obtrusions can induce arcing when, for example, a relatively high voltage is applied to the joints 16 partially bounding the component -board interstitial space 18. For example, the printed circuit assembly 10 may undergo high voltage testing where a high voltage is applied to joints 16 of the component 12. The obtrusions may cause the printed circuit assembly 10 to fail such tests, which can be extremely costly because the test typically occurs at or near the end of the printed circuit assembly manufacturing process.

[0046] It has been determined through post failure examination and analysis that the failures are likely due to the combination of the contaminants CT and the wicked fluxesFL being present in the interstitial space. More specifically, it is believed that the wicked fluxes FL attract and adhere to the contaminants CT in such a way that a creepage distance is reduced. For example, the contaminants CT and / or the wicked fluxes FL may include metal particles that cause their dielectric strength. Accordingly, the desired or design creepage distance CD1 is effectively reduced to an undesirable creepage distance CD2. The following describes an exemplary obstructive structure that can prevent the migration of such obtrusions in the component-board interstitial space 18.

[0047] Obstructive structure

[0048] FIGS. 2 and 3 show a printed circuit assembly 100 including an obstructive structure 140o. As shown in FIGS. 2 and 3, the printed circuit assembly 100 includes a component 120 affixed to a printed circuit board 140. The conductive terminals 1201 are shown as being bound to the printed circuit board 140 to form conductive joints 160. The printed circuit assembly 100 has a generally planar shape although alternative shapes and / or form factors may be employed, such as for example slightly arched, laddered, etc. The printed circuit assembly 100 is also shown as being rigid although non-rigid, such as for example flexible, printed circuit assemblies may be employed.

[0049] Also shown are relatively thin horizontal silkscreen markings (not enumerated) to indicate the top / bottom edges of the surface mount component that could serve as dams for flux intrusions from a lateral direction (e.g., another component) of the component 120. In addition, a component midline M is shown as being disposed approximately midway between and parallel to the conductive terminals 1201 of the component 120. The component midline M may be referred to as a transversal component midline as opposed to a longitudinal midline that may extend between the two conductive terminals 1201.

[0050] The component 120 is comprised of a component body 120b and conductive terminals 1201. The component 120 may be an electronic component, such as a resistor, capacitor, inductor, and / or the like. As shown in FIGS. 2 and 3, the component 120 is comprised of two conductive terminals 1201 although more may be employed. For example, the component may be a multi-terminal component, such as an integrated circuit chip. Additionally, or alternatively, although the two conductive terminals 1201 are shown as being disposed on opposing ends of the component body 120b, alternativepositions may be employed, such as for example, 90-degree relatively offset locations. For example, a square integrated circuit component where conductive terminals are on each side of the component may be employed.

[0051] The printed circuit board 140 is shown as being comprised of a substrate 140s, conductive pads 140p, conductive traces 140t, a mask 140m, and an obstructive structure 140o. With more particularity, the conductive pads 140p and conductive traces 140t are shown as being a layer that is disposed on a component side of the substrate 140s. The conductive pads 140p and the conductive traces 140t are disposed, generally, in between the component 120 and the printed circuit board 140. Additionally, or alternatively, conductive pads and / or traces may be disposed elsewhere between and / or on other surfaces of a printed circuit board. For example, a multi-layer printed circuit board with vias may be employed.

[0052] The component 120 is affixed to the printed circuit board 140 with a conductive filler 160r. More specifically, the conductive filler 160r is disposed about and adjacent the conductive terminals 1201 of the component 120, adjacent the conductive pads 140p, and between the conductive terminals 1201 and their corresponding conductive pads 140p. Accordingly, the conductive joints 160 of the component 120 may be comprised of the conductive terminals 1201, the conductive filler 160r, and the conductive pads 140p. As shown, the conductive filler is comprised of solder, although any suitable material may be employed, such as brazing material, welding, conductive epoxies, and / or the like.

[0053] As can be appreciated, the obstructive structure 140o is disposed between the component body 120b, the substrate 140s, and the two joints 160. As will be described in more detail in the following, the obstructive structure 140o can prevent and / or limit a migration of obtrusions into the space defined by the component body 120b, the substrate 140s, and the two joints 160.

[0054] Detailed view of an obstructive structure

[0055] FIG. 4 shows an enlarged view of the printed circuit assembly 100 described with reference to FIGS. 2 and 3 where section view cross hatching, and the mask and silkscreen backdrop are omitted for clarity. As shown in FIG. 4, the obstructive structure 140o is disposed between the component body 120b, the substrate 140s, and the two joints 160. The component 120 and its component body 120b and conductive terminals1201 are shown. Also shown and enumerated in FIG. 4 is the printed circuit board 140 and its substrate 140s, and conductive pads 140p. The joints 160 and the conductive filler 160r are also shown. Also shown is a component-board interstitial space 180 illustrated as a dashed-line rectangle disposed between and defined by the component body 120b, the joints 160, and substrate 140s. The component midline M described with reference to FIGS. 2 and 3 traverses the component-board interstitial space 180. Two obtrusions comprising wicked fluxes FL are shown as extending from the joints 160 into the component-board interstitial space 180.

[0056] As shown in FIG. 4, the obstructive structure 140o is comprised of a first through fourth dam 142o-l - 142o-4, although more and / or fewer dams can be employed in alternative obstructive structures. The first through fourth dam 142o-l - 142o-4 are shown as being comprised of a mask layer 142om and a silkscreen layer 142os. The mask layer 142om and silk screen layer 142os may be comprised of material that is deposited and cured prior to the component 120 being affixed to the printed circuit board 140. Accordingly, the mask layer 142om and silkscreen layer 142os may not include metal particles and thus may have a relatively high dielectric constant.

[0057] The obstructive structure 140o is also shown as including a first through third central reliefs 144o-l - 144o-3 and a first and second proximate reliefs 146o-l, 146o-2 proximate the joints 160. The first through third central reliefs 144o-l - 144o-3 may be dimensioned to be smaller than a typical dimension of a contaminant, such as the contaminants CT described with reference to FIG. 1. The first and second proximate reliefs 146o-l, 146o-2 may be sized to prevent the wicked fluxes FL from extending further into the component-board interstitial space 180. With more particularity, the two fluxes FL are shown as extending from the conductive fillers 160r to the first and second dams 142o-l, 142o-2. As can be appreciated, the two wicked fluxes FL extend to but not beyond the first and second dams 142o-l, 142o-2.

[0058] With more particularity, the wicked fluxes FL are formed when the conductive terminals 1201, the conductive pads 140p, and / or conductive filler 160r are heated above a melting temperature of a precursor for the conductive filler 160r. For example, the precursor for the conductive filler 160r may be a solder paste that includes particles of the conductive filler 160r, such as solder particles, and a flux, such as solder flux. When heated, the particles melt into the conductive filler 160r shown in FIG. 4. Additionally,the flux can migrate to an external surface of the conductive filler 160r and subsequently wick along a surface of the component body 120b. However, while wicking the flux may encounter the first and second dams 142o-l, 142o-2, which prevent further wicking along the bottom of the component body 120b. Instead, the wicking fluxes extend into the first and second proximate reliefs 146o-l, 146o-2, thereby forming the wicked fluxes FL shown in FIG. 4.

[0059] As can be appreciated, a creepage distance CD can be defined by the first and second dams 142o-l, 142o-2. For example, the creepage distance CD shown in FIG. 4 may be a minimum creepage distance CD. That is, the design creepage distance can be a distance between an inner surface of the first and second dams 142o-l, 142o-2 because testing has determined that the two wicked fluxes will not extend further. Additionally, or alternatively, the first through fourth dam 142o-l - 142o-4, or more particularly the third and fourth dam 142o-3, 142o-4, may prevent a contaminant, such as for example, the contaminants CT described above, from migrating beneath the component 120. Accordingly, even if, for example, the wicked fluxes FL were to extend slightly past an inner surface of the first and second dam 142o-l - 142o-2, then contaminants will not be able to stick to the wicked fluxes FL.

[0060] As discussed above, the first through fourth dam 142o-l - 142o-4 are comprised of the mask layer 142om and silkscreen layer 142os. The mask layer 142om may be formed during the masking process described above. The silkscreen layer 142os can be added in a subsequent step after the masking process and prior to the component 120. The silkscreen layer 142os may be desirable to ensure that a space between a component proximate surface of the first through fourth dam 142o-l - 142o-4 is minimal or nonexistent to prevent the wicked flux FL and / or contaminants from being undesirably present in and / or extending into the component-board interstitial space 180.

[0061] As can be appreciated from the foregoing description of FIGS. 2-4, a given dam of the first through fourth dam 142o-l - 142o-4 is shown as free of transversal reliefs joining two reliefs of the first through third central reliefs 144o-l - 144o-3 and / or the first and second proximate reliefs 146o-l, 146o-2 parallel to and on opposing sides of the given dam. In addition, the height of the dams may be determined by a height of the component -board interstitial space 180. For example, the heights of the first through fourth dam 142o-l - 142o-4 may be chosen to be proximate and / or abut a substrate 140sproximate surface of the component body 120b. In the exemplary obstructive structure 140o described with reference to FIGS. 2-4, the height of the first through fourth dam 142o-l - 142o-4 may be a sum of a thickness of the mask layer 142om and the silkscreen layer 142os.

[0062] The first through third central reliefs 144o-l - 144o-3 and / or the first and second proximate reliefs 146o-l, 146o-2 are shown as having a height extending from an exposed surface of the substrate 140s to an exposed surface of the silkscreen layer 142os. In addition, the widths of the first through third central reliefs 144o-l - 144o-3 and / or the first and second proximate reliefs 146o-l, 146o-2 are shown as being different but symmetrical about the component midline M. However, reliefs of alternative obstructive structures may extend from an exposed surface of, for example, a mask to a second exposed surface of the mask and / or an exposed surface of a substrate. Additionally, or alternatively, widths of the reliefs in the alternative obstructive structure may vary, be the same, and / or be asymmetrical about a corresponding component midline. Additionally, or alternatively, the reliefs of the alternative obstructive structure can be asymmetrically disposed about the component midline.

[0063] As can be appreciated from a comparison of FIGS. 1 and 4, the design creepage distance CD associated with the obstructive structure 140o is significantly greater than the undesirable creepage distance CD1 shown in FIG. 1. In addition, the creepage distance CD is repeatable in various manufacturing conditions. For example, even if excess solder paste is employed, the wicked fluxes FL may simply fill more of the first and second proximate reliefs 146o-l, 146o-2. Since the first and second proximate reliefs 146o-l, 146o-2 are adjacent the conductive pads 140p, the wicked fluxes could fill the first and second proximate reliefs 146o-l, 146o-2 without affecting the creepage distance.

[0064] It should be appreciated that alternative obstructive structures can employ more or fewer reliefs and dams. For example, although the obstructive structure 140o shown in FIGS. 2-4 is comprised of the first through fourth dam 142o-l - 142o-4, fewer or more dams may be employed. Similarly, more or fewer reliefs may be employed.

[0065] Additionally, or alternatively, other shapes other than rectangles may be employed. For example, from a top view, dam fingers may extend between conductive terminals of a component where the component has more than one conductive terminal per side. Forexample, as discussed above, an integrated circuit component may have more than one lead on each side of a square. For similar reasons, alternative dams, from a top view, may not have elongated rectangular shapes but may instead be enclosed and nested squares when being used for, for example, the square integrated circuit example.

[0066] Accordingly, from a top perspective view, the alternating dams and reliefs may generally be aligned perpendicular to a line extending between two opposing conductive terminals of a component. Thus, a given set of alternating dam and reliefs between the two opposing conductive terminals of the component may have a generally linear rectangular shape in the space between the two opposing conductive terminals.

[0067] Additionally, the generally linear rectangular shape, with or without fingers, extensions, surface variances, slight curvatures, etc., may be pieces of a larger shape, such as the nested squares described above. Additionally, or alternatively, an alternative dam may not include a silkscrccn layer and / or may include additional layers, such as for example, a second layer of solder mask. For example, a second pass of solder mask specific to an alternative obstructive structure.

[0068] Accordingly, a printed circuit board may include an obstructive structure, such as the printed circuit board 140 and obstructive structure 140o described above. The printed circuit board may include a first dam proximate a first conductive pad of the printed circuit board and a second dam proximate a second conductive pad of the printed circuit board. The first dam and the second dam can be configured to prevent obtrusions from migrating into a component-board interstitial space.

[0069] At least one of the first dam and the second dam can extend from a surface of a printed circuit board to a component proximate plane of the component-board interstitial space. As can be appreciated from FIG. 4, a board facing surface of a component can define the component proximate plane of the component-board interstitial space, such as for example, the component-board interstitial space 180 shown in FIG. 4. At least one of the first dam and the second dam extending from a surface of a printed circuit board can comprise at least one of the first dam and the second dam extending from one of a surface of the mask and a surface of a substrate of the printed circuit board.

[0070] Additionally, or alternatively, at least one of the first dam and the second dam extending to the component proximate plane of the component-board interstitial space can comprise at least one of the first dam and the second dam one of abutting andadjacent the component proximate plane of the component-board interstitial space. As can be appreciated from FIG. 4, at least one of the first dam and the second dam can comprise at least one of a mask layer and a silkscreen layer. The silkscreen layer can advantageously extend the first and / or second layer proximate to or to abut the component proximate plane of the component-board interstitial space.

[0071] Additionally, or alternatively, as can be appreciated from FIG. 2, at least one of the first dam and the second dam may have a substantially elongated rectangular shape having a longitudinal axis substantially parallel with the first conductive pad and the second conductive pad. The obstructive structure may further comprise at least a third dam and a fourth dam disposed between the first dam and the second dam, such as those shown in FIGS. 2 through 4. Additionally, or alternatively, the third dam and the fourth dam disposed between the first dam and the second dam may be configured to prevent the obtrusion from extending into the component-board interstitial space. It should be appreciated that at least one of the first dam and the second dam, and the third dam and the fourth dam may respectively be equally spaced from a component midline parallel to and equally spaced from the first conductive pad and the second conductive pad of the printed circuit board. Accordingly, the first and second dam may be referred to as a first pair of dams and the third and fourth dam may be referred to as a second pair of dams.

[0072] It should also be appreciated that an obstructive structure can further comprise at least one relief disposed between the first and second dam and / or between the third and fourth dam. Additional pairs of dams may be employed. Additionally, or alternatively, the obstructive structure may include a first proximate relief proximate the first conductive pad and a second proximate relief proximate the second conductive pad. The first dam and the second dam being configured to prevent obtrusions from migrating into a component-board interstitial space can comprises the first dam and the second dam being configured to prevent a flux from wicking along a board facing surface of a component.

[0073] As can be appreciated, the foregoing described printed circuit board can be employed in a printed circuit assembly. In such a printed circuit assembly, such as for example the printed circuit assembly 100 described above, a component can be bonded with the first conductive pad and the second conductive pad of the printed circuit board. Accordingly, the first dam may be proximate a first joint of the component and thesecond dam can be proximate a second joint of the component. As can be appreciated from the foregoing discussion, at least one of the first dam and the second dam can extend from a surface of a printed circuit board to a surface of the component defining the component-board interstitial space. As can also be appreciated, at least one of the first dam and the second dam extending to the surface of the component defining the component-board interstitial space can comprise the at least one of the first dam and the second dam one of abutting and being proximate the surface of the component defining the component-board interstitial space.

[0074] As can be appreciated the foregoing printed circuit board can be formed using any suitable manufacturing method, such as the printed circuit board manufacturing methods described above, as the following discussion illustrates.

[0075] Methods

[0076] FIG. 5 shows a method 500 of forming a printed circuit board including an obstructive structure, such as the printed circuit boards described above. In step 510 of the method 500, the first and second conductive pads described above can be formed by deposition and etching processes. The first and second conductive pads can be formed on a substrate, such as the substrates described above. Additionally, first and second dams can respectively be formed proximate the first and second conductive pads in step 520. Accordingly, the obstructive structure is configured to prevent the fluxes and / or contaminants from migrating or extending into the component-board interstitial space. The method 500 can further include forming the additional features of the printed circuit board described above, such as for example depositing a silkscreen layer on a mask layer of the dams. As can be appreciated, the printed circuit board can be used to form a printed circuit assembly described above.

[0077] FIG. 6 shows a method of forming a printed circuit assembly including the obstructive structure. As shown in FIG. 6, the method 600 includes forming a printed circuit board, such as the printed circuit board 140 described above. The method 600 is also shown as affixing a component to the printed circuit board. For example, the method 600 can include extending at least one of the first dam and the second dam from a surface of a printed circuit board to a surface of the component defining the component -board interstitial space. Such a surface may be a board facing surface of the component. Accordingly, for example, the method 600 may also include abutting ormaking proximate at least one of the first dam and the second dam to the surface of the component defining the component-board interstitial space.

[0078] As can be appreciated, a printed circuit assembly, such as for example, the printed circuit assembly 100 described above, can be employed in an electronics device as the following describes in more detail.

[0079] Electronics device

[0080] FIG. 7 shows an electronics device 700 including an obstructive structure 140o. As shown in FIG. 7, the electronics device 700 is comprised of the printed circuit assembly 100. The printed circuit assembly 100 is shown as including the component 120 affixed to the printed circuit board 140. More particularly, the component 120 is shown as being bonded to the conductive pads 140p of the printed circuit board 140. The printed circuit assembly 100 also includes the obstructive structure 140o described above, although any suitable obstructive structure or printed circuit assembly can be employed.

[0081] The electronics device 700 is also shown as including a housing 710 to which the printed circuit assembly 100 is affixed. Also shown is an input / output interface 720 and a communications port 730. As can be appreciated, the input / output interface 720 and / or the communications port 730 can be subjected to voltages that are greater than those specified as normal operation conditions for the electronics device 700. Such voltages may be referred to as high voltages and may be par t of testing and validation of the printed circuit assembly 100. Additionally, or alternatively, such high voltages can be due to abnormal conditions in other devices, cables, components, and / or the like exposed to the input / output interface 720 and / or the communications port 730. An exemplary electronics device and its use is described in the following.

[0082] Exemplary electronics device

[0083] FIG. 8 shows a vibratory meter 805 comprising an exemplary electronics device. As shown in FIG. 8, the vibratory meter 805 comprises a sensor assembly 810 and meter electronics 820. The sensor assembly 810 responds to mass flow rate and density of a process material. The meter electronics 820 is connected to the sensor assembly 810 via leads 800 to provide density, mass flow rate, and temperature information over port 826, as well as other information. The sensor assembly 810 includes a pair of manifolds, flanges having flange necks (not enumerated), a pair of parallel conduits 813, 813',driver 818, resistive temperature detector (RTD) 819, and a left and right pick-off sensor 8171, 817r.

[0084] Both of the conduits 813, 813' are driven by driver 818 in opposite directions about their respective bending axes W and W' and at what is termed the first out-of-phase bending mode of the flow meter. This driver 818 may comprise any one of many well-known arrangements, such as a magnet mounted to the conduit 813' and an opposing coil mounted to the conduit 813 and through which an alternating current is passed for vibrating both conduits 813, 813’. A suitable drive signal 885 is applied by the meter electronics 820, via a lead, to the driver 818.

[0085] The meter electronics 820 receives the RTD temperature signal on lead 895, and sensor signals 865 appearing on leads 801 carrying left and right sensor signals 8651, 865r, respectively. The meter electronics 820 produces the drive signal 885 appearing on the lead to driver 880 and vibrate conduits 813, 813'. The meter electronics 820 processes the left and right sensor signals 8651, 865r and the RTD signal on the lead 895 to compute the mass flow rate and the density of the material passing through sensor assembly 810. This information, along with other information, is applied by meter electronics 820 over port 826 as a signal.

[0086] As can be appreciated, the leads 801 can include voltages that may be higher than desired, such as a transient high voltage. Such a transient high voltage can cause failures in components, such as when components included flux wicking along a bottom of a component in a meter electronics of a vibratory meter. However, because the meter electronics 820 described with reference to FIG. 8 comprises, at least in part, a printed circuit assembly that includes an obstructive structure, such as the obstructive structure 140o described with reference to FIG. 7, the meter electronics 820 may not fail. For example, a component in the meter electronics 820, such as a capacitor that bridges an intrinsically safe barrier, may not fail due to the high voltage transient.

[0087] With more specificity, because the printed circuit board 100 includes the obstructive structure 140o, a component-board interstitial space, such as the componentboard interstitial space 180 shown in FIG. 4, may not experience a dielectric breakdown. That is, the high voltages at the input / output interface 720 and / or the communications port 730, which can respectively correspond to an interface for the leads 801 and the port 826 shown in FIG. 8, may not cause a failure of the printed circuit assembly 100.Tliis is due to the obstructive structure 140o preventing the migration of obtrusions, such as flux, contaminants, or the like, into the component-board interstitial space. Such advantages are demonstrated by the following data.

[0088] Data

[0089] The following Tables 1 and 2 show that an obstructive structure similar to the obstructive structure 140o described above prevented dielectric breakdown in a component-board interstitial space. In Table 1, no obstructive structure is employed. That is, the component-board interstitial space did not include any dams, similar to the component-board interstitial space 18 described with reference to FIG. 1.

[0090] Table 1. No obstructive structure

[0091]

[0092] For Table 2, an obstructive structure similar to obstructive structure 140o described with reference to FIGS. 2 through 4 was employed. More specifically, the tests were performed on an obstructive structure comprised of five dams and six reliefs. The dams of similar or same dimensions were symmetrically disposed about a transversal midline of a component and had the same dimensions. The two proximal reliefs had widths smaller than that of the other reliefs. The dams all included a mask and silkscreen layer.

[0093] Table 2. With an obstructive structure

[0094]

[0095] As can be appreciated, there is a significant improvement in reliability of the printed circuit assemblies tested in the test series 1 and 2 shown in Table 2. That is, the failure rate is reduced from about 9 to 20 percent to zero percent. This can be due to preventing a decrease in creepage distance in the component-board interstitial space due to the flux and / or contaminants not migrating into the component-board interstitialspace. As can also be appreciated, the test results are based on a statistically significant number of printed circuit assemblies.

[0096] The foregoing describes the printed circuit board 140, printed circuit assembly 100, electronic device 700, methods 500, 600, and the vibratory meter 805 that include obstructive structure 140o. As described above, the obstructive structure 140o, as well as any suitable obstructive structure, can prevent an undesirable dielectric breakdown in a component-board interstitial space. For example, the obstructive structure 140o is comprised of the first and second dam 142o-l, 142o-2 that can prevent wicking of a flux that may include particles of metals or other conductive substances that can fail when exposed to a high voltage potential in the component-board interstitial space 180.

[0097] Additionally, or alternatively, the first through fourth dam 142o-l - 142o-4 can prevent the migration of contaminants that may also include conductive particles from migrating and adhering to the wicked flux FL. As a result, a creepage distance of the componentboard interstitial space may be increased thereby preventing a dielectric breakdown in the component-board interstitial space.

[0098] The detailed descriptions of the above embodiments are not exhaustive descriptions of all embodiments contemplated by the inventors to be within the scope of the present description. Indeed, persons skilled in the art will recognize that certain elements of the above-described embodiments may variously be combined or eliminated to create further embodiments, and such further embodiments fall within the scope and teachings of the present description. It will also be apparent to those of ordinary skill in the art that the above-described embodiments may be combined in whole or in part to create additional embodiments within the scope and teachings of the present description.

[0099] Thus, although specific embodiments are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the present description, as those skilled in the relevant art will recognize. The teachings provided herein can be applied to other obstructive structures and not just to the embodiments described above and shown in the accompanying figures. Accordingly, the scope of the embodiments described above should be determined from the following claims.

[0100]

Claims

We claim:

1. A printed circuit board (140) including an obstructive structure (140o), the printed circuit board (140) comprising:a first dam (142o-l) proximate a first conductive pad (140p) of the printed circuit board (140); anda second dam (142o-2) proximate a second conductive pad (140p) of the printed circuit board (140);wherein the first dam (142o-l) and the second dam (142o-2) are configured to prevent obtrusions from migrating into a component-board interstitial space (180).

2. The printed circuit board (140) of claim 1, wherein at least one of the first dam (142o-l) and the second dam (142o-2) extends from a surface of a printed circuit board (140) to a component proximate plane of the component-board interstitial space (180).

3. The printed circuit board (140) of claim 2, wherein the at least one of the first dam (142o-l) and the second dam (142o-2) extending from a surface of a printed circuit board (140) comprises the at least one of the first dam (142o-l) and the second dam (142o-2) extending from one of a surface of the mask (140m) and a surface of a substrate (140s) of the printed circuit board (140).

4. The printed circuit board (140) of claim 2, wherein the at least one of the first dam (142o-l) and the second dam (142o-2) extending to the component proximate plane of the component-board interstitial space (180) comprises the at least one of the first dam (142o-l) and the second dam (142o-2) one of abutting and adjacent the component proximate plane of the component-board interstitial space (180).

5. The printed circuit board (140) of claim 1, wherein at least one of the first dam (142o-l) and the second dam (142o-2) is comprised of at least one of a mask layer (142om) and a silkscreen layer (142os).

6. The printed circuit board (140) of claim 1, wherein at least one of the first dam (142o-l) and the second dam (142o-2) has a substantially elongated rectangular shape having a longitudinal axis substantially parallel with the first conductive pad (140p) and the second conductive pad (140p).

7. The printed circuit board (140) of claim 1, further comprising at least a third dam (142o-3) and a fourth dam (142o-4) disposed between the first dam (142o-l) and the second dam (142o-2).

8. The printed circuit board (140) of claim 7, wherein the third dam (142o-3) and the fourth dam (142o-4) disposed between the first dam (142o-l) and the second dam (142o-2) are configured to prevent the obtrusion from extending into the componentboard interstitial space (180).

9. The printed circuit board (140) of claim 7, wherein at least one of a pair of the first dam (142o-l) and the second dam (142o-2) and a pair of the third dam (142o-3) and the fourth dam (142o-4) are equally spaced from a component midline parallel to and equally spaced from the first conductive pad (140p) and the second conductive pad (140p) of the printed circuit board (140).

10. The printed circuit board ( 140) of claim 1 , wherein the obstructive structure (140o) further comprises at least one relief (144o-l, 144o-2, 144o-3) disposed between the first dam (142o-l) and the second dam (142o-2).

11. The printed circuit board (140) of claim 1, wherein the obstructive structure (140o) further comprises a first proximate relief (146o-l) proximate the first conductive pad (140p) and a second proximate relief (146o-2) proximate the second conductive pad (140p).

12. The printed circuit board ( 140) of claim 1 , wherein the first dam ( 142o- 1) and the second dam (142o-2) being configured to prevent obtrusions from migrating into a component-board interstitial space (180) comprises the first dam (142o-l) and thesecond dam (142o-2) being configured to prevent a flux (FL) from wicking along board facing surface of a component ( 120).

13. A method of forming the printed circuit board including an obstructive structure of one of claims 1 through 12.

14. A printed circuit assembly (100) comprising:the printed circuit board (140) of one of claims 1 through 12: anda component (120) bonded with the first conductive pad (140p) and the second conductive pad (140p) of the printed circuit board (140);wherein:the first dam (142o-l) is proximate a first joint (160) of the component (120); andthe second dam (142o-2) is proximate a second joint (160) of the component (120).

15. The printed circuit assembly (100) of claim 14, wherein at least one of the first dam ( 142o- 1) and the second dam (142o-2) extend from a surface of a printed circuit board (140) to a surface of the component (120) defining the component-board interstitial space (180).

16. The printed circuit assembly (100) of claim 15, wherein the at least one of the first dam (142o-l) and the second dam (142o-2) extending to the surface of the component (120) defining the component-board interstitial space (180) comprises the at least one of the first dam (142o-l) and the second dam (142o-2) one of abutting and being proximate the surface of the component (120) defining the component-board interstitial space (180).

17. A method of forming the printed circuit assembly (100) of one of claims 1418. A vibratory meter (805) including an obstructive barrier, the vibratory meter (805) comprising:a sensor assembly (810); anda meter electronics (820) communicatively coupled with the sensor assembly (810), the meter electronics (820) comprising the printed circuit assembly (100) of one of the foregoing claims 14 through 16.

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