Stripline Circuit Requiring High Dielectrical Constant/High G-Force Resistance

In the prior art, two relatively compliant mating members are formed from some material, such as a ceramic impregnated teflon, or the like. Circuit components are affixed to the inner surface of one of the members and the outer surfaces of both members are covered with a layer of copper. The ceramic material impregnated in the teflon provides the high dielectric constant which is required for relatively high frequency circuits, but it is relatively difficult to bond circuit components and copper layers onto the teflon and to laminate the teflon members together. Further, because the teflon will not withstand high temperatures, it is impossible to perform many techniques, such as welding and depositing, that would be extremely advantageous in affixing components to the members. Components, such as microwave integrated circuits are extremely difficult to affix to the members and have a tendency to break loose during high G operation. Also, because of the compliance of both members, there is a tendency for the members to deform slightly under high G operation, which seriously affects operation of the stipline circuit.

The present invention pertains to a stripline circuit requiring a relatively high dielectric constant material and a high G acceleration force resistance wherein a first flat member is formed of ceramic and a second mating flat member is formed of a compliant material or ceramic with the circuit components affixed to the ceramic material, by welding, deposition, or the like, and the two members laminated together so that the ceramic member provides the required rigidity for the package. Windows may be formed in the compliant member so that components on the ceramic member may be laser trimmed to tune the stripline circuit. In this fashion, a stripline circuit package is formed with sufficient rigidity to withstand high G acceleration forces, components may be welded and/or deposited on the ceramic so that sufficiently good bonds are provided between electrical components and the ceramic, and the package may be laser trimmed after lamination to accurately tune the circuit.

It is an object of the present invention to provide a new and improved stripline circuit utilizing at least one ceramic member in the package to provide the required high dielectric constant material and high G force resistance.

It is a further object of the present invention to provide a new and improved package for a stripline circuit utilizing welding, deposition and laser trimming techniques to obtain required operating characteristics.

These and other objects of this invention will become apparent to those skilled in the art upon consideration of the accompanying specification, claims and drawing.

The single FIGURE is an exploded view in perspective of a stripline circuit packaged in accordance with the present invention.

Referring to the single FIGURE, the numeral 10 generally designates a stripline package formed in accordance with the present invention. The package 10 includes a first member 11 and a second member 12. The member 11 is formed with an inner surface 15 and an outer surface (not shown). The member 12 is formed with an inner surface (not shown) and an outer surface 18. The thickness of the members 11 and 12 is a predetermined thickness which will provide the stripline circuit with the desired electrical characteristics when the package is complete. In the present embodiment the member 11 is formed of a ceramic material, such as alumina or the like having a relatively high dielectric constant, generally ten or above. The member 12 is formed of a ceramic or a high dielectric constant compliant material which permits ease of lamination, such as a ceramic impregnated teflon (sold under the trademark Epsilam 10, by 3M, Inc.). The material making up the member 12 has substantially the same dielectric constant as the ceramic making up the member 11 so that the dielectric constant characteristics of both members 11 and 12 are similar.

The inner surface 15 of the member 11 has electrical components fixedly positioned thereon by any of a variety of procedures. For example, a component 20 is affixed to the inner surface 15 of the member 11 by welding, a component 21 is deposited on the inner surface 15, and other bonding techniques may be utilized if desired. A copper layer 25 is affixed to the outer surface of the member 11 by some convenient means, such as bonding, deposition, or the like and a copper layer 26 is affixed to the outer surface 18 of the member 12 by bonding or the like to form ground planes for the finished stripline circuit. Because the ceramic making up the member 11 has a high resistance to heat, components can be attached thereto by welding and/or depositing material thereon in any of the well known techniques. Further, microwave integrated circuits can be fixedly attached thereto without danger of the circuits breaking loose under high G stresses.

When the circuit components have been properly positioned and affixed to the member 11, the member 12 is laminated thereto by some convenient means, such as the positioning of a film of adhesive 30 therebetween, pressing the members 11 and 12 together with the film 30 therebetween and processing the package with heat or the like to provide the required bonding. The ceramic member 11 provides the package with sufficient rigidity to prevent deforming under high G forces and further provides the package with an improved resistance to high temperatures. If additional mechanical strength or rigidity is required or if the package may be subjected to relatively high temperatures, both members 11 and 12 can be formed of ceramic. However, if both members 11 and 12 are formed of ceramic there may be some additional care required in forming the inner surfaces so that a tight lamination is possible.

A window 35 is formed in the member 12 (and also in the film 30, if required) to allow laser trimming of components affixed to the inner surface of the member 11 after the package is laminated or bonded together. While a single window is illustrated it should be understood that more may be included if addditional components require trimming. Laser trimming of the components is possible because the member 11 is formed of ceramic which will withstand the high heat of the laser during trimming. Because the package can be laser trimmed or tuned after lamination thereof, the tuning is extremely accurate and simple. Further, because welding, deposition and laser trimming can be utilized in the package 10 the cost of the stripline circuit is substantially reduced and manufacturing methods and time are substantially improved.

While I have shown and described a specific embodiment of this invention, further modifications and improvements will occur to those skilled in the art. I desire it to be understood, therefore, that this invention is not limited to the particular form shown and I intend in the appended claims to cover all modifications which do not depart from the spirit and scope of this invention.