Prior microwave electrical devices include resistors, series shunt elements, and solid-state devices such as Schottky diodes, PIN diodes, varactor diodes, and transistors. Another prior microwave device is a bridge quad (also referred to as a sampling bridge) that includes four diodes in one package. Another prior microwave electrical device that has four diodes is a ring quad, also called a quad-ring.
One type of prior microwave device has beam leads on the top of the device to provide connections to external circuitry. The beam leads are structurally supported by diodes that make up the device. The beam leads also provide interconnections between terminals of the diodes. For example, on certain prior ring quads, the beam leads provide interconnections between the anodes and cathodes of the respective diodes.
For another type of prior microwave electrical device, metal interconnections reside on one side of the device and metalized layers for external connections reside on the other side of the device. This helps to make the device less fragile. Prior microwave devices using this alternative configuration include ring quads, bridge quads, and diodes.
Both of the prior types of microwave devices discussed above typically use glass to hold components of the devices together. For example, certain prior ring quads typically use glass to hold four diode blocks together. Metallic interconnections for those prior microwave devices typically provide only minimal support. Thus, for certain types of prior microwave devices, glass is the material that provides major structural support.
Nevertheless, the structural support provided by the glass typically is only for a portion of a prior device assembly process. During the final stages of device fabrication, prior microwave devices are typically either (1) completely encased in glass to form a hermetic seal or (2) encapsulated in epoxy.
The way glass is used for certain prior microwave devices has several disadvantages. One disadvantage is that the glass makes the prior microwave devices relatively fragile. Because of this fragility, those prior microwave devices have relatively low maximum tear strengths. This means that certain prior microwave devices can be destroyed relatively easily.
Another disadvantage associated with certain prior microwave devices is that assembly operations are relatively tedious and delicate given that beam leads of certain prior microwave devices are not covered by the glass layer. Capacitance, inductance, and balance problems can arise from improper bonding of the beam leads. The exposed and relatively large beam leads during the fabrication process are also prone to bending, which can result in capacitance, inductance, and balance problems. Dynamic resistance problems can also arise. Special care is typically required for the beam leads to seat properly during packaging.
Another disadvantage associated with glass is that air bubbles are typically formed inside the glass layer during fabrication. When the liquified glass is deposited during certain prior fabrication processes, air often enters the liquified glass and forms air bubbles inside the glass. The air bubbles inside the glass typically weaken the glass in a nonuniform way from point to point and from device to device. This results in differences in strength between prior microwave devices from device to device.
Another disadvantage with certain prior microwave devices is that glass typically is liquified as part of the fabrication process. This requires relatively high temperatures.
One type of prior integrated circuit is typically attached to a package substrate when being packaged to a lead package. The leads of the prior integrated circuit are typically bonded to respective leads of the lead package.
One disadvantage of such prior integrated circuit is that the leads of the prior integrated circuit tend to have relatively high lead inductance that typically results in electrical problems with respect to the circuit. Another disadvantage is that the packaging of the prior integrated circuit is typically relatively expensive. Another disadvantage is that the leads need to be spaced apart far enough to permit the use of wire bonding machinery.
Another type of prior integrated circuit employs beam leads formed on the top of the prior integrated circuit for attachment to a next level of interconnection. In addition, the beam leads provide connections to external circuitry. These beam leads, however, are typically relatively fragile and difficult to handle.
Another type of prior integrated circuit uses bumps on the die or substrate or both, or uses solder balls, to attach the chip directly to a substrate in a "flip chip" fashion. One disadvantage with these approaches is that there may be different thermal expansions with respect to the chip and the substrate, which in some cases can lead to failure of the solder connection. Moreover, such arrangements may result in the chip being easily damaged during handling.