Patent Application
20080084678
The present invention is illustrated by way of example, and not limitation, in the accompanying figures, in which like references indicate similar elements, and in which:
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
Various embodiments of the present invention provide a printed circuit board and a method for imbedding a battery in a printed circuit board. The method includes connecting the battery to a first inner pad and a second inner pad, and forming a first battery contact for electrically connecting the first inner pad and a first outer pad. The method further includes electrically isolating the first battery contact, and forming a second battery contact for electrically connecting the second inner pad and a second outer pad.
Various embodiments of the present invention further provide a printed circuit board. The printed circuit board includes a plurality of core layers and a battery imbedded between two of the plurality of core layers. The printed circuit board further includes a first outer pad connected to a first battery contact pad, and a second outer pad connected to a second battery contact pad.
Before describing in detail the particular method for imbedding a battery in a printed circuit board in accordance with the present invention, it should be observed that the present invention resides primarily in combinations of method steps and apparatus components related to the method for imbedding the battery in the printed circuit board. Accordingly, the apparatus components and method steps have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.
In this document, relational terms such as first and second and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms ‘comprises,’ ‘comprising,’ or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element preceded by ‘comprises . . . a’ does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.
The term ‘another’, as used herein, is defined as at least a second or more. The terms ‘including’ and/or ‘having’, as used herein, are defined as comprising.
The PCB 100 also includes a battery 106, which is integrated on the inner core layer 104. As is known to one of ordinary skill in the art, the term battery is defined as a device that stores energy and makes it available in electrical form. As used herein, the term battery implies a single cell device generally known as an electrochemical battery. In an example battery of an embodiment of the present invention, the battery is a high temperature lithium cell capable of withstanding temperatures up to 200° C. In any case, the temperature that the battery is capable of withstanding is such that the battery can endure the temperatures produced during the PCB fabrication process.
The battery 106 includes a first battery contact pad 112 and a second battery contact pad 114. The outer core layer 102 of the PCB 100 includes a first outer pad 108 and a second outer pad 110. The first outer pad 108 and the second outer pad 110 provide outer connections for the first battery contact pad 112 and the second battery contact pad 114, respectively. Further, the inner core layer 104 includes a first inner pad 116 and a second inner pad 118. The first inner pad 116 is connected to the first battery contact pad 112, and the second inner pad 118 is connected to the second battery contact pad 114. In one embodiment, the first battery contact pad 112 is a printed anode for the battery 106 and the second battery contact pad 114 is a printed cathode for the battery 106.
The connections are made by using a conductive medium 120. Examples of the conductive medium 120 include conductive epoxy, solder, and the like. In an embodiment of the present invention, the conductive medium 120 is Kwik-Stik™ silver colloid manufactured by Structure Probe, Inc. In any case, the conductive medium 120 functions to carry electrical signals between the battery 106 and the inner core layer 104.
A first battery contact via 122 electrically connects the first outer pad 108 to the first inner pad 116. Similarly, a second battery contact via 124 electrically connects the second outer pad 110 to the second inner pad 118. In an embodiment of the present invention, the first outer pad 108, the second outer pad 110, the first inner pad 116, and the second inner pad 118 are metallic. As such, the first outer pad 108, the second outer pad 110, the first inner pad 116, and the second inner pad 118 are electrically conductive.
In one embodiment of the present invention, the outer pads 108, 110 comprise metallic copper material. In one embodiment of the present invention, the inner pads 116, 118 also comprise metallic copper material. In one embodiment of the present invention, the vias 122, 124 are made electrically conductive by copper plating. In any case, the vias 122, 124 may be mechanically drilled into the PCB 100.
The PCB 100 further includes one or more prepreg layers, provided between the plurality of core layers. A prepreg layer 126, as shown in
In one embodiment, each of the plurality of core layers of the PCB 100 is coated with a black oxide coating prior to the battery 106 being imbedded in the PCB 100. In such an embodiment, a part of the black oxide coating is selectively removed to prevent any obstruction to the integration of the battery.
The PCB 100 further includes a plurality of electronic components (not shown) and a plurality of holes (not shown). The electronic components are connected to form a circuit. Examples of the electronic components integrated on the PCB include, but are not limited to, capacitors, resistors, diodes, transistors, and Integrated Circuits (ICs). The holes may be copper-plated and provide electrical connections for the plurality of electronic components. In any case, the battery 106 powers the electronic components present in the PCB 100.
In one embodiment, the plurality of core layers, one or more prepreg layers present in the PCB, and the battery imbedded in the PCB are laminated together by using a press lamination process. In one embodiment, the lamination process is a FR4 press process. As such, the FR4 press process may be performed for approximately an hour at 181° C. Alternatively, the FR4 press process may be performed for approximately 40-45 minutes at approximately 181° C. In other alternatives, the FR4 press process may be carried out at temperatures ranging from approximately 150° C. to approximately 230° C. depending on the substrate used in the plurality of core layers. In any case, as used above, approximately is defined as “close to” as understood by one of ordinary skill in the art. For example, in the above one embodiment, the term is defined to be within one hour and within 181° C.
Continuing with
At step 306, the first battery contact is electrically isolated. In one embodiment, electrically isolating the first battery contact includes selectively etching a conductive layer around the first battery contact. Electrical isolation of the first battery contact is carried out to isolate the first battery contact via from the plurality of holes on the PCB.
At step 308, a second battery contact is formed between a second outer pad, present on the outer core layer, and the second inner pad. A second battery contact via is drilled to form the second battery contact. In one embodiment, the second battery contact via is made electrically conducting by covering the second battery contact via with copper, although other elements may be used, e.g. silver, and reference to copper is not meant to be limiting on an embodiment of the present invention. In one embodiment, prior to covering the second battery contact via, a plating mask is applied on the top and bottom portions of the first battery contact. Covering the second battery contact via with copper may be performed by electroless plating the second battery contact via with copper. After electroless plating, the plating mask is removed and re-applied on the top and bottom portions of the first battery contact. The second battery contact via is then electroplated with copper and the plating mask is removed from the top and bottom portions of the first battery contact. The plating mask is applied to prevent copper deposition on the first battery contact during electroless plating and the electroplating of the second battery contact via. Examples of plating mask include, but are not limited to, a Kapton tape and a photoimageable film.
The method of
After the battery 106 is imbedded in the PCB 100, a circuit pattern is imaged on the PCB 100, followed by pattern plating, etching, and other existing fabrication processes, to process the PCB 100.
In an embodiment of the present invention, the battery to be imbedded in the PCB is a rechargeable battery, e.g. battery 106. While embedding the rechargeable battery, the first battery contact via and the second battery contact via can be drilled and plated simultaneously. The battery may discharge because of simultaneous plating of the first battery contact via and the second battery contact via. However, the battery can be recharged after the battery has been imbedded in the PCB.
Therefore, as described above, the present invention provides a new PCB and a method for imbedding a battery in a PCB. Since the battery is embedded in the PCB, the electronic device using the PCB does not require a separate battery to power the electronic device. Also, no separate contacts and solder are required for connecting the electronic components to the battery because of the presence of pads on the outer core layer.
It is expected that one of ordinary skill, notwithstanding possibly significant effort and many design choices motivated by, for example, available time, current technology, and economic considerations, when guided by the concepts and principles disclosed herein will be readily capable of generating such software instructions and programs and ICs with minimal experimentation.
In the foregoing specification, the present invention and its benefits and advantages have been described with reference to specific embodiments. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of present invention. The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims. The present invention is defined solely by the appended claims including any amendments made during the pendency of this application and all equivalents of those claims as issued.
