Thin profile battery mounting contact for printed circuit boards

A battery mounting contact consists of a substrate having a battery cavity for housing a battery therein. A first contact is attached to a first surface of the substrate and extends over the battery cavity substantially planarly adjacent to the substrate first surface. A second contact extends over the battery cavity substantially planarly adjacent to a second surface of the substrate. The battery, disposed within the battery cavity, makes electrical contact by its anode with the first contact and by its cathode with the second contact, or vis versa. The battery mounting contact significantly reduces the thickness of a battery powered device.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to battery mounting contacts. More 
particularly, the present invention relates to thin profile battery 
contacts for active tags used in active radio frequency identification and 
methods of producing the same. 
2. State of the Art 
Identification and tracking of objects are important concerns for most 
business operations. Presently, a leading method of object identification 
is bar code reading. Multiple objects can be identified by checking each 
object individually using a bar code reader which reads a bar code 
attached to each object. Although using bar codes on objects is a great 
advancement over manually and individually identifying objects, the bar 
code reading process is still time consuming and is also subject to bar 
code damage and bar code reader error. Furthermore, bar code readers 
usually require human operation wherein a person passes the bar code 
affixed to the object over the bar code reader, or passes the bar code 
reader over the bar code. Such human operation also introduces human error 
into the bar code reading process. 
With such problems in bar code reading for identification, radio frequency 
identification (hereinafter "RF-ID") is rapidly becoming an important 
object identification method. The most important component of an RF-ID 
system is an information carrying tag which is affixed to the object. The 
information carrying tag functions in response to a coded radio frequency 
(hereinafter "RF") signal which the tag receives from a base station. In a 
passive information carrying tag, the tag receives its energy from the 
base station RF signal and reflects an RF carrier signal back to the base 
station. An active information carrying tag (hereinafter "active tag") 
contains a battery. The battery allows the active tag to retain, modify, 
and send information contained on the information carrying tag in response 
to the base station RF signal. 
The active tag generally consists of a semiconductor chip having RF 
circuits, logic circuits, and memory. The active tag also has an antenna, 
a battery, a substrate for mounting the components, interconnections 
between components, and a physical enclosure, such as a plastic encasement 
or lamination. 
In a typical configuration, the base station has a computer section which 
issues commands to an RF transmitter and receives commands from the RF 
receiver. The base station antenna sends RF signals to and receives RF 
signals from one or more active tags within the RF signal range, generally 
about 50 feet. 
These active tags can be attached to articles of varying shapes and sizes 
and can be used in applications such as merchandise identification, item 
delivery control (letters and packages), inventory control and tracking, 
container control and tracking, surveillance, telemetry, automatic toll 
collection, and monitoring the location of vehicles and personnel. 
As previously discussed, active tags require a battery. The functional 
specifications of the battery include a nominal cell voltage (typically 3 
volts), high energy density and specific energy. Such specifications 
generally exist in lithium batteries. Furthermore, the battery must have a 
very thin profile in order to manufacture active tags which are 
unobtrusive and/or which can be used with a credit or debit card. 
FIG. 8 illustrates a typical surface mount battery contact configuration 
300. A battery 302, having a first contact surface 304 and a second 
contact surface 306, is positioned to contact the battery second contact 
surface 306 with a second contact 312 which is mounted on a substrate 310. 
A first contact 308 contacts the battery first contact surface 304. The 
first contact 308 typically has a battery contact portion 314 which 
extends over the battery 302 to contact the battery first contact surface 
304, and a battery attachment portion 316 which is attached to the 
substrate 310. The battery first contact surface 304 may be an anode and 
the battery second contact surface 306 may be a cathode, or vice versa. 
The first contact 308 and the second contact 312 have conductive traces or 
the like (not shown) electrically connecting the first and second contacts 
308, 312 to other active tag components (not shown). Although this surface 
mount battery contact configuration 300 is useful for some semiconductor 
applications or the like, it is not conducive to most active tag 
applications. The combined height of the substrate 310, the first contact 
308, the battery 302, and the second contact 312 is too thick for most 
active tag applications. 
U.S. Pat. No. 5,558,957 issued Sep. 24, 1996 to Datta et al. teaches a 
method for making a thin flexible battery for microelectronics 
applications. However, a flexible battery requires specialized 
manufacturing techniques, which would increase the cost of the active 
tags. 
Therefore, it would be advantageous to develop an apparatus for mounting a 
commercially-available, inexpensive, thin lithium battery on a substrate 
while achieving a thin overall active tag profile without requiring 
complex processing steps or expensive components. 
SUMMARY OF THE INVENTION 
The present invention relates to a novel battery mounting contact and 
mounting technique. The battery mounting contact includes a substrate 
having a battery cavity defined therein which is slightly larger than the 
size of a predetermined battery to be mounted. A first contact is attached 
to a first surface of the substrate and extends over the battery cavity 
substantially planarly adjacent to the substrate first surface. A second 
contact extends over the battery cavity substantially planarly adjacent to 
a second surface of the substrate. The second contact may be attached to 
the substrate first surface wherein a portion of the second contact would 
extend through the battery cavity and align substantially planarly 
adjacent to the substrate second surface, or the second contact may be 
attached to the substrate second surface and extend over the battery 
cavity. The first contact and the second contact are each in electrical 
communication with separate conductive traces or the like which are, in 
turn, in electrical communication with circuitry on the substrate. The 
circuitry may include RF circuits, logic circuits, memory, and an antenna. 
A battery, having a first contact surface and a second contact surface, is 
disposed within the battery cavity between the first contact and the 
second contact. The battery first contact surface makes electrical contact 
with the first contact and the battery second contact surface makes 
electrical contact with the second contact. The battery first contact 
surface may comprise an anode and the battery second contact surface may 
comprise a cathode, or vice versa. 
By mounting the battery in such a manner, at least partially contained 
within the substrate depth, the thickness of the substrate no longer 
contributes to the overall height of the assembly because the thickness of 
the substrate can generally be reduced below the thickness of the battery. 
Although the present invention is directed to RF-ID tags, the battery 
mounting contact may be used in a variety of the applications which 
require a thin profile such as: PCMCIA cards, cellular phones, video game 
cartridges, pagers, and the like. Furthermore, the present invention is 
useful for applications with thickness limitations such as credit cards or 
"smart cards" which need to have a thickness of 0.039 inches or less.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 is an illustration of a preferred embodiment of an active tag 100 of 
the present invention. It should be understood that the figures presented 
in conjunction with this description are not meant to be actual 
cross-sectional views of any particular portion of an active tag, but are 
merely idealized representations which are employed to more clearly and 
fully depict the invention than would otherwise be possible. 
The active tag 100 comprises a substrate 102, such as a printed circuit 
board or card, preferably a glass filled epoxy circuit board, having an 
antenna 104 attached thereto, which is used to receive and transmit RF 
signals to and from a base station (not shown). The antenna 104 connects 
to a circuitry component 106. The circuitry component 106 may comprise RF 
circuits, logic circuits, and memory. 
A battery mounting contact 108 is disposed in or substantially planarly 
adjacent to a battery cavity 112. FIG. 1 is illustrated without a battery 
within the battery mounting contact 108. Referring to FIG. 2 (a 
cross-sectional view of FIG. 1 along line A--A), the battery mounting 
contact 108 comprises a contact arm 114, a contact pad 116 and a battery 
120 mounted between the contact arm 114 and the contact pad 116. The 
contact arm 114 is attached to a first surface 122 of the substrate 102 
and extends over the battery cavity 112 substantially planarly adjacent to 
the substrate first surface 122. The contact pad 116 extends over the 
battery cavity 112 substantially planarly adjacent to a second surface 124 
of the substrate 102. A first and second lamination layer of dielectric 
material or the like 118, 118' cover the first substrate surface 122 and 
the second substrate surface 124, respectively. 
The contact arm 114 and the contact pad 116 are conductive and preferably 
made of metal, such as aluminum, aluminum alloys, copper, copper alloys, 
tin plated steel, and the like. As shown in FIG. 1, the contact arm 114 
and the contact pad 116 are each in electrical communication with separate 
conductive traces 126, 128, respectively, which are, in turn, in 
electrical communication with the circuitry component 106 on the substrate 
102. The contact arm 114 may be slightly bent in the form of a lead spring 
such that the vertical or transverse distance between the contact arm 114 
and the contact pad 116 is smaller than the thickness of the battery 120. 
This results in the battery 120 being held firmly and resiliently between 
the contact arm 114 and the contact pad 116. 
As shown in FIG. 2, the battery 120, having a first contact surface 130 and 
a second contact surface 132, is disposed within the battery cavity 112 
between the contact arm 114 and the contact pad 116. The battery first 
contact surface 130 makes electrical contact with the contact arm 114 and 
the battery second contact surface 132 makes electrical contact with the 
contact pad 116. The battery first contact surface 130 may be an anode and 
the battery second contact surface 132 may be a cathode, or vice versa. 
The contact pad 116 is preferably designed in a size and shape to 
approximately match a surface area of the battery second contact surface 
(as shown in FIG. 1). This provides a sound mechanical support for the 
battery 120. The contact arm 114 is preferably thin to allow for easy 
insertion thereunder of the battery 120 into the battery cavity 112, but 
thick enough to have sufficient resiliency to firmly retain the battery 
120 in the battery cavity 112. 
FIG. 2 illustrates the substrate 102 having a thickness of about 31 mils 
(0.031 inches). The battery 120 is preferably a lithium coin cell 2016 
battery, such as manufactured by Eveready.RTM.. The designation of "2016" 
stands for 20 mm in diameter and 1.6 mm thick (0.7874 inches in diameter 
and 0.063 inches thick). The contact arm 114 and contact pad 116 are each 
approximately 0.003 inches thick. 
FIG. 3 illustrates a thin active tag 140 which is similar to the active tag 
100 of FIGS. 1 and 2. All elements in FIG. 3 which are common to FIGS. 1 
and 2 retain the same numeric designation. The thin active tag 140 
includes a thin profile battery 142 . The thin profile battery 142 is 
preferably a lithium coin cell 2005 battery (20 mm (0.7874 inches) in 
diameter and 0.5 mm (0.0197 inches) thick). This results in the combined 
thickness of the thin profile battery 142 and the contact pad 116 being 
thinner than the substrate 102 shown in FIG. 2. Thus, a thin profile 
battery 142 allows for the use of a thin substrate 144 to make a first 
surface 146 of the battery 142 substantially flush with a first surface 
148 of the thin substrate 144 and the contact pad 116 substantially flush 
with a second surface 150 of the thin substrate 144. 
As shown respectively in FIGS. 2 and 3, the contact pad 116 may be attached 
to the substrate first surface 122, 148, wherein a portion of the contact 
pad 116 extends through the battery cavity 112 and aligns substantially 
planarly adjacent to the substrate second surface 124, 150. This 
configuration has the advantage of reducing the overall height of the 
active tag 100, 140 by the thickness of the contact pad 116 which would 
have been attached to the substrate second surface 124, 150. However, as 
shown in FIG. 4, when the overall thickness of the active tag is not 
critical, the contact pad 116 can be attached to the substrate second 
surface 124. All elements in FIG. 4 which are common to FIG. 2 retain the 
same numeric designation. The contact pad 116 is connected to a conductive 
trace 162 on the opposite side of the substrate 102 through a conductive 
via 164. The conductive trace 162 is in electrical communication with the 
circuitry component 106 (shown in FIG. 1). 
FIG. 5 illustrates an active tag 170 having a substrate 172 with a battery 
cavity 174 which does not extend entirely through the substrate 172. A 
battery 176, having a first contact surface 178 and a second contact 
surface 180, is disposed within the battery cavity 174 between the contact 
arm 114 and a contact node 182 which extends through the bottom 184 of the 
battery cavity 174. 
FIG. 6 illustrates another embodiment of an active tag 190 having a 
substrate 186 with a battery cavity 188. A battery 192, having a first 
contact surface 194 and a second contact surface 194', is disposed within 
the battery cavity 188 between the contact arms 196, 196' which contact 
the first contact surface 194 and the second contact surface 194', 
respectively. This embodiment can be constructed by first attaching the 
contact arms 196, 196' to the lamination material 118, 118', respectively, 
then attaching one of the first or second battery contact surfaces 194, 
194' to one of the contact arms 196, 196' and lamination material 118, 
118'. The substrate 186 is placed over the battery 192, such that the 
battery cavity 188 fits over the battery 192. The other contact arm 196, 
196' and lamination material 118, 118' is attached to the substrate 186 
and the other of the first or second battery contact surfaces 194, 194'. 
FIG. 7 illustrates an application of the present invention wherein a base 
station 202 may transmit and receive RF signals 204 to information 
carrying tags 206. The information carrying tags 206 may retain, modify, 
and send information contained on the information carrying tags 206 in 
response to the base station: RF signals 204. 
The embodiments disclosed above may, of course, be encased on one or both 
sides by a physical enclosure, such as an injection molded plastic 
encasement or by laminating an insulative sheet thereover. 
Having thus described in detail preferred embodiments of the present 
invention, it is to be understood that the invention defined by the 
appended claims is not to be limited by particular details set forth in 
the above description as many apparent variation thereof are possible 
without departing from the spirit or scope thereof.