Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Patent
1996-03-26
1998-07-14
Aftergut, Jeff H.
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
156295, 298901, 347 47, 347 71, 347 72, B41J 216, B41J 2135
Patent
active
057798370
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to droplet deposition apparatus and especially to ink jet printheads made of piezo-electric ceramic. In particular it relates to methods for bonding such printheads during assembly. The invention finds particular applications in the manufacture of printheads employing shear mode wall actuators.
For example, in U.S. Pat. No. 5,003,679 (EP-B-0 277 703) there is disclosed a method of making multi-channel pulsed droplet deposition apparatus comprising the steps of forming a base with one or more layers of piezo-electric material, forming a multiplicity of parallel grooves in said base which extend through said layer or layers of piezo-electric material to afford walls of said material between successive channels, locating electrodes in relation to said walls so that an electric field can be applied to effect shear mode displacement of said walls transversely to said channels and securing a top wall to the walls to close said liquid channels.
An alternative example of piezo-electric shear mode ink jet printheads is provided in U.S. Pat. No. 5,016,028 (EP-B-0 364 136), both of the above references being herein incorporated by reference.
A particular feature of a preferred embodiment of the latter reference is that for satisfactory actuation of the actuator walls between channels, the compliance ratio of the bond layer which secures the top wall to the, actuator walls (the compliance ratio is hE/He where h is the thickness of the bond layer, e is the modulus of elastic of the layer, H is the height of the walls and E is the modulus of elasticity of the walls) is less than 1 and preferably less than 0.1. For example, if H=440 .mu.m E=110 GPa and e=5 GPa, the latter value stipulates that approximately the bond layer thickness h<2 .mu.m.
Whilst a variety of techniques exist for bonding piezo-electric ceramic material to other ceramics or to glass and other substrate materials used in ink jet printhead manufacture, the most flexible and convenient technique is often adhesive bonding. The term adhesive is intended to include all suitable glues and cements. However, real difficulties are encountered in providing a uniform adhesive bond layer of thickness 2, .mu.m or less.
It is an object of this invention to overcome some or all of these difficulties in providing an improved method of manufacturing multi-channel pulsed droplet deposition apparatus.
Accordingly, the present invention consists in one aspect in a method of making multi-channel pulsed droplet deposition apparatus comprising the steps in any order of bonding together a stack of layers comprising at least one layer of piezo-electric material and a cover layer; forming a multiplicity of parallel grooves in said stack which extend at least partly through said layer of piezo-electric material to afford walls of said material between successive droplet liquid channels, said channels being closed by said cover layer; and locating electrodes in relation to said walls so that an electric field can be applied to effect shear mode displacement of said walls transversely to said channels; characterised in that the bonding together of two of said layers comprises the steps of preparing respective mating surfaces of said layers to reduce the surface roughness to the order of 2 .mu.m or less; applying an excess of adhesive and with the mating surfaces in register applying pressure and allowing adhesive to flow in the bonding plane until surface extremities of the respective mating surfaces come into substantially direct contact to produce a bond layer of mean thickness 2 .mu.m or less such as 1 .mu.m or less.
By suitably controlled lapping or grinding, it is possible to control the roughness of each of the mating faces so that when they are brought together in contact, in the absence of the bond layer, the surfaces conform so that mean separation between the faces is 2 .mu.m or less. However, when a bond layer of a suitable glue is applied to the surfaces and the surfaces are brought together in contact under pressure, the bond layer buil
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Aftergut Jeff H.
XAAR Limited
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