Circuit board with air-bridge

A multi-layer circuit board having apertures that are selectively and electrically isolated from electrically grounded member and further having selectively formed air bridges and/or crossover members which are structurally supported by a polymeric material. Each of the apertures selectively receives an electrically conductive material.

FIELD OF THE INVENTION

The present invention relates to a circuit board and a method for making a circuit board and more particularly, to a multi-layer electronic circuit board having metallized apertures which are selectively isolated and/or disconnected from an electrical ground plane and further having selectively formed air bridges and/or crossover circuits.

BACKGROUND OF THE INVENTION

Multi-layer circuit boards operatively receive electronic components and allow the received components to be desirably interconnected to selectively and cooperatively form electrical circuits. Particularly, these components are operatively received upon opposed board surfaces and within certain interior portions of the board, thereby desirably allowing each of the electronic circuit boards to contain a relatively large amount of components which efficiently, respectively, and densely populate the respective boards.

It is desirable to allow each of the component containing surfaces or portions of a created and/or formed electronic circuit board to communicate and/or to be selectively interconnected, thereby allowing the contained electronic components to cooperatively and selectively form a relatively large number of desired electrical circuits. This desired communication and/or interconnection typically requires the use of shared electrical ground planes, the transmittal of electrical power and/or control type signals between some or all of the component containing surfaces or board portions, and/or the connection of components on each of the opposed surfaces and/or within and between certain of the interior portions and the top and/or bottom and/or other board surfaces.

This desired interconnection typically requires that one or more holes be formed or drilled through each of the circuit boards, thereby creating at least one “through hole” or “via” traversing between each of the opposed component containing surfaces and through the various interior circuit board portions. Typically this drilling process is relatively complex and time consuming, thereby increasing the overall circuit board production cost. This drilling process also undesirably damages and/or destroys many of the circuit boards, thereby further increasing overall production cost.

Further, it is desirable to form “air-bridges” or “crossover type circuits” upon one or more selected surfaces and/or within certain component containing portions of the formed circuit board in order to allow multiple levels of circuits and/or electrical interconnections to be formed upon a single board surface and/or within a certain component containing portion of the circuit board, thereby desirably increasing the amount of electrical circuits which may be created upon and/or within the created circuit board (e.g., increasing the density of the contained electrical circuitry).

These “air bridges” or crossover circuits are typically formed by rather complicated, costly, and time consuming processes. The formed bridges and crossover circuits further do not typically and efficiently accommodate certain desirable circuit board interconnection processes, techniques, and/or methodologies, such as and without limitation, the use of relatively heavy wire bonding (e.g., aluminum wire having a diameter of about five to about twenty milli-meters) or the direct connection of components to a surface of the board.

There is therefore a need to provide an electronic circuit board and a method for producing a multi-layer electronic circuit board which overcomes some or all of the previously delineated drawbacks of prior electronic circuit boards and methods for making a circuit board, which selectively allows grounded and non-ground “vias” to be desirably and selectively and efficiently formed in a cost effective manner, and which further allows for the efficient and selective formation of air-bridge members or crossover circuits which desirably accommodate diverse types of circuit interconnection processes and which increase the circuitry density within the formed electronic circuit board.

SUMMARY OF THE INVENTION

It is a first object of the present invention to provide an electronic circuit board and a method for producing an electronic circuit board which overcomes some or all of the previously delineated drawbacks of prior electronic circuit boards and of prior electronic circuit board forming methodologies and techniques.

It is a second object of the invention to provide a method for producing a multi-layer electronic circuit board which overcomes some or all of the previously delineated drawbacks of prior multi-layer electronic circuit board forming methodologies and techniques, which allows for the formation or creation of an electronic circuit board which selectively receives various electronic components, which allows for the selective, efficient, and reliable formation of metalized apertures, within the formed and/or created electronic circuit board, which cooperatively allow for communication by and between these various electronic components and which further cooperatively allow for the selective interconnection of these contained components.

It is a third object of the invention to provide a method for producing a multi-layer electronic circuit board which overcomes some or all of the previously delineated drawbacks of prior multi-layer electronic circuit board forming methodologies and techniques and which allows for the selective formation of metalized apertures, within a circuit board, which may be selectively connected or disconnected and/or selectively isolated from a formed electronic ground plane or bus.

It is a fourth object of the invention to provide a method for producing a multi-layer electronic circuit board which overcomes some or all of the previously delineated drawbacks of prior multi-layer electronic circuit board forming methodologies and techniques and which allows for the selective and efficient formation of air bridges and/or crossover circuits and/or crossover members which are adapted to accommodate a wide variety of component interconnection assemblies, techniques, and/or methodologies.

According to a first aspect of the invention a circuit assembly is provided comprising an electrically conductive core member having a first surface and a second surface; a first pre-circuit assembly having at least one air-bridge, the pre-circuit assembly operatively disposed upon the first surface of the electrically conductive core member; a second pre-circuit assembly having at least one air-bridge, the second pre-circuit assembly operatively disposed upon the second surface of the core electrically conductive member, thereby forming a circuit assembly having a first aperture which is electrically connected to the core metal member and a second aperture which is electrically isolated from the core metal member.

According to a second aspect of the present invention, a circuit assembly is provided. The circuit assembly is made by the process of forming a first pre-circuit assembly including a first core member having a first and as second surface, a first plurality of electrically conductive members disposed upon the first surface, and a second plurality of electrically conductive members disposed upon the second surface; forming a second pre-circuit assembly having first and second circuit boards, which are selectively attached to a dielectric adhesive material and which cooperatively form a separation region; coupling the dielectric adhesive material to the second plurality of electrically conductive portions; removing certain portions of the first core member, there forming a pedestal portion which abuts the separation region; extending the separation through the pedestal portion, thereby forming a circuit board.

According to a third aspect of the present invention a multi-layer circuit assembly is provided. The circuit assembly is made by the process of providing at least one member having an aluminum core portion which is contained between a top and a bottom layer of copper; providing at least one electrically conductive member having a first and a second surface; providing at least one circuit board; creating an aperture within the at least one electrical conductive member; operatively coupling the at least one circuit board to the first surface of the electrically conductive member; operatively coupling the at least one member to the second surface of the electrically conductive member; and selectively etching the aluminum core portion, thereby forming a circuit assembly.

These and other objects, aspects, and advantages of the present invention will become apparent upon reading the following detailed description in combination with the accompanying drawings.

Referring now to FIG.1(a)-(m), there is shown a process10for making an electrical circuit board assembly in accordance with the teachings of the preferred embodiment of the invention. Particularly, process10begins by obtaining and/or providing a member12having a first core portion14which is operatively contained between a first or top and a second or bottom layer or a top and a bottom member16,18, as best shown in FIG.1(a). It should be appreciated that the terms “first” and “second” should not be limited to the layer and/or member which they specifically refer to within this specification (e.g., the term “first” may alternatively refer to the bottom layer or member18.) In one non-limiting embodiment of the invention, core portion or member14comprises conventional and commercially available aluminum material while layers/members16,18comprise conventional, commercially available and substantially identical electrically conductive material, such as copper. As further shown best in FIG.1(a), layers16,18are notched. That is, certain portions of layers/members16,18are removed by a conventional etching process in order to create selectively formed apertures20within the layers16,18, thereby creating exposed “areas” or surface portions22,24,26,28,30,32,34,36,38, and40of the core member14. In one non-limiting embodiment of the invention, portions or pairs22,32;24,34;26,36;28,38; and30,40are respectively aligned (e.g., portions32,34,36,38, and40are respectively and wholly resident under portions22,24,26,28, and30). In a further non-limiting embodiment of the invention, portions22,24,26,28,30,32,34,36,38, and40are substantially similar in size and shape.

In one non-limiting embodiment of the invention, the thickness of the core member14is about fifty to two hundred micrometers while the thickness of portions16,18is substantially identical and is about five to one hundred micrometers. Other sizes, shapes, thicknesses, and/or dimensions of members14-18may be utilized.

Process10, as shown best in FIGS.1(b) and1(d), further requires the acquisition and/or creation of substantially identical layers or members42,44each of which, in one non-limiting embodiment, comprise substantially identical and commercially available layers of dielectric adhesive material having a substantially identical size, shape, and thickness.

Process10, as shown best in FIG.1(c), further requires the acquisition and/or creation of an electrically conductive member or layer46which, in one non-limiting embodiment, is formed from conventional copper material having a thickness, in one non-limiting embodiment, ranging from about five micrometers to about two hundred micrometers. Further, at least one aperture or “hole”48is created within the member or layer46by drilling, punching, and/or etching. As shown later, this at least one aperture48will selectively form a “non-grounded” via or “through hole”.

As shown best in FIG.1(e), process10further requires the acquisition and/or creation of a second member50which is substantially similar to member12. More particularly, member50includes a core portion or member52which is substantially similar to core portion14, and top or first and bottom or second members or layer portions54,56which are substantially and respectively similar to member/layer portions16,18. Layers54,56are each selectively notched and, as such, have several selectively formed apertures58which are effective to cause member50to have exposed top surface portions60,62,64,66,68and exposed bottom surface portions70,72,74,76,78. In one embodiment of the invention, portions or pairs60,70;62,72;64,74;66,76; and68,78are aligned (e.g., portions74,72,70,76, and78are respectively and wholly resident under portions64,62,60,66, and68and portions74,72,70,76, and78are respectively identical in size and shape to portions64,62,60,66, and68). In a further embodiment of the invention, portions60,62,64,66,68,70,72,74,76,78are substantially similar in size and shape.

A pre-circuit assembly92is formed in the fifth step of the process10, which is shown best in FIG.1(f). Particularly, layer18of member12is attached by a conventional process or method to the top surface80of member or layer42, effective to allow portions of layer42to overlay the previously formed apertures20within the layer18, and more particularly, to overlay the exposed portions32,34,36,38,40. The bottom surface82of member or layer42is attached, by a conventional process or method, to the top surface84of layer or member46, thereby overlaying the previously formed aperture48. The bottom surface86of the member46is attached, by a conventional process or method, to the top surface88of the layer or member44and the attached surface88overlays the previously formed aperture48. Further, the bottom surface90of the layer44overlays the top layer54of member50, effective to overlay apertures58within layer54and to, more particularly, overlay exposed portions60,62,64,66,70. This formed pre-circuit assembly92is best shown in FIG.1(f).

As best shown in FIG.1(g), process10continues with the creation of a pre-circuit assembly94which is created by selectively forming first and second apertures96,98within the formed pre-circuit assembly92. These apertures96,98may be formed by drilling, etching, punching, or by any other conventional process or methodology. Particularly, the first aperture96is aligned with (e.g., extends through) the previously created aperture48and effectively extends the previously created aperture48through the formed circuit assembly94. The second aperture98, in one non-limiting embodiment, is substantially identical in shape and size to the aperture96and is aligned with (e.g., extends through) apertures30,40. It should be realized that apertures96,98may be of various sizes and shapes and that nothing in this description should or is meant to limit these apertures96,98to any certain size or shape.

Exposed surfaces100,102of pre-circuit assembly94are respectively contained within and/or reside within and/or define the apertures96,98and form respective “interior surfaces” of apertures96,98. In one non-limiting embodiment of the invention, member46functions as or comprises an electrical ground plane (i.e., member46is physically and electrically coupled to a source of electrical ground potential). As shown, member46does not reside within aperture96and does not reside upon surface100. Hence, surface100is electrically isolated and/or electrically disconnected from member46, thereby causing aperture96to be a “non-grounded via” or a “non-grounded aperture”. Member46does reside within aperture98and does not reside upon surface102. Hence, surface102is electrically connected to member46, thereby causing aperture98to be a “grounded via” or a “grounded aperture”.

In the seventh step of process10, as best shown in FIG.1(h) andFIG. 2, the members14,52are selectively etched forming air-bridges or crossover members104, thereby creating a multi-layer circuit assembly106. The formed air-bridge or crossover members104, in one non-limiting embodiment, cooperatively form voids108.

In the eighth step of process10, which is shown best in FIG.1(i), a conventional and commercially available polymeric material112is applied to pre-circuit assembly106to substantially “fill” the cooperatively created voids108, thereby “underfilling” and structurally supporting the formed air bridges or crossover members104and creating a pre-circuit assembly110.

In the ninth step of process10, which is best shown in FIG.1(j), an electrically conductive material114is applied within and/or through the formed apertures96,98. In one non-limiting embodiment, material114substantially fills the apertures96,98thereby forming a pre-circuit assembly116having portions and/or layers14,16,18,42,44,46,52,54, and56which are electrically interconnected by the solder material114. In one non-limiting embodiment of the invention, the electrically conductive material114comprises a conventional and commercially available solder material. In a further non-limiting embodiment of the invention, the electrically conductive material114comprises a conventional and commercially available conductive adhesive which electrically interconnects the various layers residing within and/or communicated with the apertures96,98, thereby allowing the various layers to be electrically interconnected and allowing the board116to be functionally tested prior to being populated by components (i.e., the solder114allows testing type signals to be readily communicated to these layers). In a further non-limiting embodiment of the invention electrically conductive material114is applied by “wave soldering”, “reflow soldering”, or by “laser soldering”. In a further non-limiting embodiment of the invention, electrically conductive material114may be applied by “screen printing” the electrically conductive material114through apertures96,98and “cured” in a known and conventional manner.

It should be appreciated that the selective etching of core members14,52allows the air bridges and/or crossover members104to be efficiently and relatively easily formed in a cost effective manner. Further, such etching allows for the selective formation of air bridges and/or crossover members104which may have a selected shape and/or size, thereby allowing the selectively and etchably created air bridges and/or crossover members104to support a wide variety of circuits and components, effective to selectively and efficiently accommodate a wide variety of circuit interconnection methodologies and/or techniques.

It should further be appreciated that the apertures96,98may also be efficiently formed and/or created in a “single step” operation which obviates the need to separately drill or create apertures in each member/component which selectively forms the created multi-layer circuit assembly116.

Referring now to FIGS.3(a)-(f), there is shown a process140for making an electronic circuit board assembly in accordance with the teachings of an alternate embodiment of the invention. Particularly, process140begins by obtaining and/or providing a pre-circuit assembly142having a core portion or member144. As shown, several electrically conductive portions or members146are contained and/or disposed upon the top or first surface147of member144, and several electrically conductive portions or members148are contained and/or disposed upon the bottom or second surface149of member144, as shown best in FIG.3(a). In one non-limiting embodiment of the invention, core portion144comprises conventional and commercially available aluminum material while layers/members146,148comprise conventional, commercially available, and substantially identical electrically conductive material, such as copper. Hence, member142comprises, in one non-limiting embodiment, a “copper clad aluminum member”.

In the second step of process140, as shown best in FIG.3(b), a layer of adhesive material150is acquired and/or created having a top or first surface152and a bottom or second surface154. Virtually any type of adhesive material may be selectively utilized within this process140.

In the third step of process140, as shown best in FIG.3(c), a pre-circuit assembly156is provided. Particularly, in one non-limiting embodiment of the invention, pre-circuit assembly156is comprised of or includes a core portion158which contains apertures160,162,164. Particularly, core portion158contains a first electrically conductive layer or member166which is disposed on top or first surface167and a second electrically conductive layer which is disposed on bottom or second surface169. In one non-limiting embodiment of the invention, core portion158comprises conventional and commercially available laminate material while layers/members166,168comprise conventional, commercially available, and substantially identical electrically conductive material, such as copper.

In another non-limiting embodiment of the invention, core portion158may be formed from a wide variety of conventional and commercially available circuit boards159(a)-159(d) such as a conventional “FR-4” or a conventional “rigid circuit board”. As shown, boards/portions159(a) and159(b) are separated by a separation distance, region, or aperture164; portions159(c) and159(b) are separated by a separation distance, region or aperture162; and portions159(d) and159(a) are separated by a separation distance, region, or aperture160. It should be appreciated that selective numbers of “pre-formed” and commercially available boards159(a-d) may utilized within assembly140.

In the fourth step of process140, as shown best in FIG.3(d), portions148of pre-circuit assembly142are attached to the top surface152of material150. Material166of pre-circuit assembly156is attached to the bottom surface154of material150, thereby forming pre-circuit assembly170. It should be realized that circuit assembly156may be formed/created concurrently with assembly140, or separately. Moreover, the use of commercially available circuit assemblies159(a)-159(d) reduces the overall cost of process140and allows for the use of the created circuit assemblies in a wide variety of applications. Moreover, separate fabrication and/or creation of assemblies142and156allows for the separate creation of power traces and allows for a more efficient creation of the final circuit board assembly.

In the fifth step of process140, as best shown in FIG.3(e), process140continues by applying a certain etchant material (e.g., an aluminum etchant material) to certain selective portions of core portion144effective to remove or “etch away” certain selective portions of core portion144, thereby forming pillars portions172(a)-(e) of core portion144which reside upon the top surface152of material150and which may selectively overlay apertures160,162,164, thereby forming pre-circuit assembly174.

In the sixth step of process140, as shown best in FIG.3(f), process140continues by drilling or otherwise causing apertures160,162,164to extend through pre-circuit assembly174and through pillars172(a),172(c),172(e), thereby forming pre-circuit assembly176which may be selectively attached to the formed circuit116(e.g., to members16or56) or sued to replace one of the pre-circuit assemblies12,50within process10. It should be appreciated that apertures160,162,164may be electroplated or processed in a manner which allows for apertures160,162,164to form circuit interconnections.

Referring now to FIGS.4(a)-(e), there is shown a process180for making an electronic circuit board assembly in accordance with the teachings of an alternate embodiment of the invention. Particularly, process180begins by obtaining and/or providing a pre-circuit assembly or a member182having a core portion184which includes electrically conductive portions or members186which are disposed upon top or first surface187, and several electrically conductive portions or members188which are disposed upon bottom or second surface189. In one non-limiting embodiment of the invention, core portion184comprises conventional and commercially available aluminum material while layers/members186,188comprise conventional, commercially available, and substantially identical electrically conductive material, such as copper.

In the second step of process180, as shown best in FIG.4(b) and FIG.4(d), a pair of dielectric adhesive layers or members190and192are acquired and/or created. These members190,192have top surfaces194,196and bottom surfaces198,200.

In the third step of process180, as shown best in FIG.4(c), a pre-circuit assembly202is provided which is generally and relatively flexible. Particularly, assembly202comprises a substantially and relatively flexible core member or portion204having several electrically conductive portions or members206which are disposed upon the top or first surface207and having several electrically conductive portions or members208which are selectively disposed upon the second or bottom surface209.

In the fourth step of process180, as shown best in FIG.4(e), pre-circuit assembly210is provided. Particularly, pre-circuit assembly210includes a core member or portion212having several electrically conductive portions or members214disposed upon a first or top surface215and having several electrically conductive portions or members216selectively disposed upon a second or bottom surface217. In one non-limiting embodiment of the invention, core portion212comprises conventional and commercially available aluminum material while layers/members214,216comprise conventional, commercially available, and substantially identical electrically conductive material, such as copper.

In the fifth step of process180, as shown best in FIG.4(f), members188of pre-circuit assembly182are operatively attached or coupled to the top surface194of adhesive190. Portions206of pre-circuit assembly202are then operatively connected and/or coupled to the bottom surface198of material190. Portions208of pre-circuit assembly202are coupled to the top surface196of material layer192. Portions214of pre-circuit assembly210is operatively connected and/or coupled to the bottom surface200of material layer192, forming a pre-circuit assembly270which may be processed by drilling, electroplating, and/or any other process or methodology producing circuit layer interconnections and which may be selectively attached to the formed circuit116(e.g., to members16or56) or used to replace one of the pre-circuit assemblies12,50within process10. It should be appreciated that pre-circuit270may be subjected a certain etchant material(e.g., and aluminum etchant material) which “etches away” or removes certain portions of core metal members184,212and which allows the formed pre-circuit assembly to be substantially and relatively flexible.

It should be appreciated that the pre-circuit assemblies formed by processes140,180may be constructed and/or otherwise assembled by the use of multi-layer circuit boards which are formed prior to the use of processes140,180or by attaching multi-layer circuit boards formed concomitantly with process140,180. It should further be appreciated that “adhesive” or “non-adhesive” containing circuit boards and/or circuit board assemblies may be alternately and selectively used concomitantly with processes140,180. In one non-limiting embodiment of the invention, these circuit boards may be alternately and selectively used to produce circuit interconnections of the “power” type, the “signal” type, the “ground plane” type, or the “interconnection” type.

It should be understood that the invention is not limited to the exact embodiment or construction which has been illustrated and described but that various changes may be made without departing from the spirit and the scope of the invention.