Direct nozzle plate to chip attachment

Details Direct nozzle plate to chip attachment Direct nozzle plate to chip attachment

1995-10-06

2001-02-20

Gallagher, John J. (Department: 1733)

Adhesive bonding and miscellaneous chemical manufacture

Methods

Surface bonding and/or assembly therefor

C029S890010, C029S890100, C156S273900, C347S047000

Reexamination Certificate

active

06190492

ABSTRACT:

TECHNICAL FIELD
This invention relates to thermal ink jet printheads, and, more specifically, relates to such printheads having a nozzle plate attached to a semiconductor chip having drop-ejection heating elements.
BACKGROUND OF THE INVENTION
Plastic nozzle plates that have ink chambers and conduits built-in need a means of attachment to the underlying semiconductor chip. In current designs, the chambers and other ink flow features are created by essentially conventional photo etching using a thick film photoresist layer applied to a semiconductor chip. Photoresist remaining after the imaging and etching operation is left in place and used as an adhesive layer.
The remaining photoresist is an effective adhesive because current techniques only partially cure the thick film photoresist. The lack of complete cross linking of the resist layer imparts an adhesive property to it which is used for bonding the nozzle plate down by applying temperature and pressure.
To reduce costs and to eliminate a major source of misalignment between the ink heaters or chambers and nozzle holes, it is desirable to use a single-structure nozzle plate with integrated flow features and nozzle holes built in. Several techniques may be utilized to achieve the integrated nozzle plate, such as laser machining and injection molding. In each case it is generally possible to apply an adhesive layer for connection of the nozzle plate to the underlying semiconductor chip. Heat and pressure can be applied to activate such adhesive since the nozzle plates, although they are polymer films, may be made of selected polymer materials which do not melt or degrade at the temperatures required.
Such an added layer is costly in terms of material and operation steps. Moreover, certain molded plastics, typically those of homogeneous polymeric material, cannot be used at such temperatures because the nozzle plate would melt or deform. Moreover, it is also difficult, if not impractical, to apply the adhesive layer to individual film nozzle plates after their manufacture.
Accordingly, it is the primary feature of this invention that a separate adhesive layer is avoided in the bonding of a film nozzle plate to a semiconductor chip having drop-ejection heaters for nozzles of the nozzle plate.
This invention employs adhesion by melt contact. It is widely known that such adhesion is a function of roughness or irregularity of the surfaces involved, and a preliminary roughening step may be employed in accordance with this invention.
DISCLOSURE OF THE INVENTION
In accordance with this invention, an individual thin film nozzle plate is placed on the semiconductor chip accurately positioned to form an ink jet printhead. Pressure, which may be moderate is applied, and resistors on the chip are driven in a controlled manner to a temperature to melt just the surface of contact between the chip and the nozzle plate, without any of the body of the nozzle plate reaching that temperature for a time in which it would be deformed or degraded. This may be by use of the drop-ejecting heaters or also with additional heaters added to the chip for the purpose of the bonding step.
Although surface roughness is often desirable for bonding laminations, no roughening step is necessary or practiced in the embodiments contemplated by this invention.


REFERENCES:
patent: 4666823 (1987-05-01), Yokota et al.
patent: 5305015 (1994-04-01), Schantz et al.
patent: 5408738 (1995-04-01), Shast et al.
patent: 5434607 (1995-07-01), Keefe
patent: 57-70612 (1982-05-01), None
patent: 03106657 (1991-07-01), None

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