1. Field of the Invention
This invention relates to the packaging of a millimeter-wave module containing chip and wire technology or other components that require protection from the environment.
2. Background
Use of wireless technologies employing frequencies above 20 GHz (millimeter-wave technologies) are increasing. Cellular telephone and pager systems are among the most notable applications of wireless technologies.
Components in millimeter-wave systems often utilize chip and wire technology. Chip and wire technology refers to the use of a naked integrated circuit chip that is electrically and mechanically attached (soldered) to a conducting carrier where small wires bonded to pads directly on the integrated chip make connections to the chip. The chip itself is not packaged, i.e., it is an open device. Many of the electrical components used in these millimeter-wave applications are mounted on microwave antenna towers and are exposed to the elements. These components, in spite of the sensitive chip and wire technology, need to be durable.
A typical microwave transmitter system 100 is shown in FIG. 1. In FIG. 1, a base-band source of information 101 feeds a signal to be transmitted to a modulator 102. The output signal from modulator 102 is inputted to a tripler/amplifier module 103. Tripler/amplifier module 103 generates a signal having amplitude and frequency greater than the amplitude and frequency of the signal from modulator 102. Typically, the frequency of the input signal to tripler/amplifier module 103 ranges from 12 to 13.3 Ghz and the frequency of the signal from the tripler/amplifier module 103 is in the frequency range of 36 to 42 GHz (nominally 38 GHz).
The output signal from tripler/amplifier module 103 is inputted to a filter/diplexer 104 which outputs a signal to a microwave antenna 105 for broadcast. The same microwave antenna 105 receives incoming microwave signals and filter/diplexer 104 routes the incoming signal to a receiver 106. Receiver 106 receives a nominal 38 GHz signal and outputs a signal compatible with the format of base-band information 101. Many modules, especially those that utilize active microwave components such as the chip and wire technology, must be tightly sealed to prevent damage of sensitive components. For example, moisture from the surrounding atmosphere can damage or affect the operation of tripler/amplifier module 103 of FIG. 1.
FIG. 2 shows tripler/amplifier module 103. Tripler/amplifier module 103 is one that contains a monolithic microwave integrated circuit (MMIC) amplifier U1. MMIC U1 is a naked GaAs integrated circuit chip which is easily damaged if exposed to the elements (dust, pollution, moisture, solvents etc.). In addition, electrical connections to pads of MIMIC U1 (for power, biasing, etc.) are delicate and also easily damaged if exposed to the atmosphere.
Typically, modules such as tripler/amplifier module 103 are enclosed in a hermetically sealed housing 118 having hermetically sealed terminals. For example, tripler/amplifier module 103 has an RF input 111, a microwave output 115, a ground connection 112, a negative DC bias input 113, and a positive DC bias input 114. Tripler/amplifier 103 may also include other hermetically sealed inputs and outputs not shown in FIG. 2. The housing 118 of the module includes a base section 116 and a lid section 117 that encloses the internal circuitry of the tripler/amplifier module 103.
In order to protect the naked MMIC chip U1, the entire module 103 is sealed. The lid 117 is sealed to the base 116 and all of the inputs to the interior of the module (111 through 115) are hermetically sealed. Even the coaxial tube to waveguide connection 111 and the output waveguide connection 115 are sealed. This causes each of these connectors to be high cost. The total manufacturing cost of the tripler/amplifier module 103 is therefore high.
In addition, if the tripler/amplifier 103 fails, it is typically discarded because components cannot be repaired without breaking the hermetic seal. Repairs on the hermetically sealed prior art tripler/amplifier module 103 are, therefore, impractical.