Process for manufacturing an electronic component, in particular a surface-wave component working with acoustic surface waves

[0002] 1. Field of the Invention

[0003] The invention is directed to a method for manufacturing an electronic component, particularly a SAW component working with surface acoustic waves, comprising a chip with piezoelectric substrate and an active filter structures that are contacted to interconnects of a base plate, and comprising a cap-shaped housing that envelopes the chip and is tightly seated on the base plate.

[0004] 2. Description of the Related Art

[0005] For protection against disturbing environmental influences, particularly against chemically. Aggressive substances and moisture, a potentially multi-layer and after layer insert usually 2-layer, structured protective films, (Protec) by the assignee, is arranged between a base plate and a chip given active filter structures contacted to the ceramic or plastic base plate in flip-chip technique,—i.e. with bumps or, respectively, solder balls. Protected by this film, the SAW filter can have a casting compound, for example—epoxy resin, filled under it and cast around it after the flip-chip bonding without the active filter structure being thereby coated and the surface waves being undesirably attenuated.

[0006] For SAW filters of the ultra-frequency pass range that are contacted in flip-chip technique, i.e. typically given chip dimensions less than approximately 2×2 mm², it has been shown that an adequate stability given alternating temperature stressing is established even when the corresponding spaces between base plate and

[0007] As a result of observation, the object of the invention is to specify a method that enables the eliminate of the expensive PROTEC encapsulation of the SAW components and that nonetheless produces excellent SAW components.

[0008] For achieving this object in a method of the species initially cited, the invention provides that a carrier plate that can be separated into base plates is respectively provided with interconnects in the base plate regions, that one chip per base plate region is contacted to the interconnects thereof in flip-chip technique, that a cover film, particularly a metal foil or a potentially metal-coated plastic film, is applied onto the chip-equipped carrier plate, that the cover film is treated, (e.g.—heat and pressure treated,) such that it envelopes each chip—except for the chip surface facing toward the carrier plate—and lies tightly on the carrier plate surface in regions between the chips, and that the carrier plate is separated into the individual SAW components.

[0009] Developments of the invention can be derived from the discussion below and the drawing together with the description thereof.

[0010] FIG. 1 is a plan view onto an inventively employed carrier plate in a partially broken illustration;

[0011] FIG. 2 is a partially cut and broken side view of a first exemplary embodiment of a chip-equipped carrier plate according to the method of the invention; and

[0012] FIG. 3 is a second exemplary embodiment of an SAW filter fabricated according to the method of the invention, likewise in a partially cut side view; and

[0013] FIG. 4 is a flowchart illustrating the inventive method.

[0014] In FIG. 1, in the first-cited method, a carrier plate 10, for example, a ceramic or plastic plate, that can be separated into base plates 2 along the parting lines B—B and C—C is provided with interconnects (not shown in the drawing) in the respective base plate regions A, these interconnects being usually through connected to the backside base plate region. The carrier plate 10 is coated with a solderable metal grid 5 corresponding to the base plate dimensions—preferably simultaneously with the application of the interconnects—, and one chip 1 per base plate region is subsequently contacted by bumps 6 to the interconnects of it in flip-chip technique.

[0015] Finally, a cover film—namely a metal foil 3 having suitable thickness and ductility—is applied onto the chip-equipped carrier plate 10 and is pressure and heat treated for example, in an autoclave or under a vacuum, such that it tightly envelopes each chip 1 (except for the chip surface neighboring the carrier plate 10), and it lies on the metal grid in the regions between the chips 1 and is soldered to it along the solderable metal frame.

[0016] As a result of this type of processing, the metal foil 3, may also be implemented using an ultrasound application along the metal grid 5 as well, the metal foil 3 conforming to each chip 1 as a quasi as cap-shaped housing that has its face edges seated hermetically tight on the metal frame 5 or, respectively, on the carrier plate 10.

[0017] Assuming no hermetically tight closure is required between the foil and the base plate, then a plastic film 4 (see FIG. 3) that is potentially metal-coated for electromagnetic shielding can be employed instead of the metal foil 3. The plastic film may be composed, for example, of an adhesive material in the B-condition or may be adhesive-coated on its surface facing toward the carrier plate 10. This film, which can also be subjected to a pressure and heat treatment in an autoclave, also surrounds the chip hermetically tight. However, since a metal grid 5 is superfluous given plastic films, the face edge 4aof each “plastic housing” is seated directly on the carrier plate 10 or, respectively, on the base plate 2.

[0018] One may also to deep-draw the metal or plastic foil or film 34 cap-shaped in a grid dimension defined by the base plates 2 and to invert this partly deep-drawn foil over the chip-equipped carrier plate 10, after which it has its regions 3a, 4alying on the carrier plate 10 tightly joined to the carrier plate in the previously described way. This possibility is of great significance, particularly for shrink-free or low-shrink carrier plates.

[0019] The housings that have arisen in this way in a copy technique can be further-stabilized and additionally sealed hermetically tight to a metal cladding by pressing or casting, for example, with epoxy resin, as indicated with broken lines in FIG. 2 (see region 7).

[0020] Furthermore, partial layer sequences composed can be applied onto the outside and/or inside surface of the metal foil and plastic film 34, these partial layer sequences being adapted such that they attenuate disturbing acoustic volume waves, potentially in collaboration with a pressing or casting compound 7.

[0021] Filled epoxy resins are especially suited as damping compound, for example with SiO₂, W, WO₃or Ag as a filling constituent. The above-described method is illustrative of the principles of the present invention. Numerous modifications and adaptions thereof will be readily apparent to those skilled in this art without departing from the spirit and scope of the present invention.