Abstract:
A component for the inkjet print head and the manufacturing method thereof are disclosed where photosensitive polymer is used as the substrate. Orifices and ink chambers are made on the substrate by photolithography. Conductive traces for interconnection to a print head chip are integrated to the substrate by combining photolithography and electroforming procedures.

Description:
This Nonprovisional application claims priority under 35 U.S.C. § 119(a) on patent application Ser. No. 092123441 filed in TAIWAN on Aug. 26, 2003, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The invention relates to a print head component and the manufacturing method thereof. In particular, the invention relates to a component for the inkjet print head that requires a low production costs and the manufacturing method thereof. 
     2. Related Art 
     The print head is a key component of inkjet printers. The assembly of current print heads is usually done by first making the orifice plate and the print head chip. Afterwards, a photosensitive adhesive is coated on the chip. Ink chambers and ink supply channels are then formed on the adhesive by photolithography. The orifice plate and the chip are aligned and attached together with the photosensitive adhesive. Finally, tape automated bonding (TAB) leads are aligned and attached onto the electrical signal pads of the chip using high temperature and pressure. 
     The signal pads of the print head chip are combined with the wire pads of a substrate using aligned embossing of the inner leads. This requires the use of inner lead bonding (ILB) equipment in semiconductor technology. During packaging, the signal pads of the print head chip and the wire pads on the substrate have to be aligned accurately. The wire pads are then connected to the signal pads by embossing. The welded region is filled with glue to increase its reliability. As this procedure requires high precision and has certain difficulty, conditions in the manufacturing process greatly affect the quality of the packaged elements. On the other hand, the orifice plate used in the existing technology is made by electroforming. First, an electroplating solution has to be precisely prepared. A good electroforming quality can be obtained only after long time experiment and calibration. Therefore, it is very hard to control the size, roundness, and thickness of the orifices in such batch produced orifice plates using this method. Moreover, the bonding strength of the metal orifice plate and the inkjet chip may be lowered with time because of the erosion of the ink inside the ink chamber. This will eventually result in local delamination. 
     One may also form orifices on the TAB by laser ablation. With reference to the U.S. Pat. No. 5,305,015, the manufacturing process starts by forming transmission holes on a TAB substrate. Signal wires are then defined by electroforming or copper foil attaching. Afterwards, a laser beam is shined and focused on the substrate to make an orifice. After a cleaning process, it is combined with the chip by embossing, thus completing the print head chip packaging. However, a laser is used to make orifices individually in this method. There are three hundred nozzles on a high resolution inkjet print head at least. Therefore, it takes a long time and the equipment is expensive. Moreover, the high temperature produced in the process often deforms the borders of the orifices. If one wants to make orifices of different sizes, different lenses have to be used to focus the laser beam. It is also very hard to remove the debris&#39; around the orifices produced in the lasing process. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, the invention provides a component for the print head and the manufacturing method thereof. Ink chambers, orifices, and conductive traces for interconnection to the chip are integrated into a substrate. 
     The disclosed manufacturing method of the print head component includes the steps of: providing a substrate; forming a sacrifice layer above the substrate; forming a metal conductive circuit above the sacrifice layer; forming a photosensitive polymer layer above the metal conductive circuit; making orifices on the photosensitive polymer layer by photolithography and providing through holes for electrical connection of the metal conductive circuit to the exterior, the orifice allowing fluid to pass and the through holes exposing the lead end of the metal conductive circuit for electrical connection with the exterior; and removing the sacrifice layer so that the photosensitive polymer layer and the metal conductive circuit attached thereon detach from the substrate. Moreover, one can form a second photosensitive polymer layer on the surface of the previous photosensitive polymer and use photolithography to form an ink chamber or channel on the second photosensitive polymer layer. The ink chamber communicate with and connects to each orifice. The channel provides ink to the ink chamber. 
     The invention further discloses a print head component, which contains: a photosensitive polymer substrate with more than one orifice for a fluid to pass through, the orifices being formed by photolithography; a metal conductive circuit with a front end and a lead end and installed on the surface of the photosensitive polymer substrate, the front end receiving external signals and the lead end providing electrical connection to the chip. The lead end of the metal conductive circuit is thus exposed to the ambient space. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will become more fully understood from the detailed description given hereinbelow illustration only, and thus are not limitative of the present invention, and wherein: 
         FIGS. 1 through 7  show the flowcharts in the first embodiment of the invention; and 
         FIGS. 8 through 11  show the flowcharts in the second embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention employs a combination of exposure, development, and electroforming methods to make an integrated print head component. Please refer to  FIGS. 1 to 7  for a first embodiment of the invention. 
     As shown in  FIG. 1 , we first deposit a metal sacrifice layer  110  on the surface of a substrate  100 . As shown in  FIG. 2 , a photoresist layer  120  is defined on the sacrifice layer  110 . As shown in  FIG. 3 , a metal conductive circuit  130  is formed in the gap of the photoresist  120  by electroforming. 
     As shown in  FIG. 4 , a photosensitive polymer layer  140  is coated on the metal conductive circuit  130 . A photolithography process is further employed to define orifices and through holes for the lead end of the metal conductive circuit as the electrical connection between the metal conductive circuit  130  and the exterior. The mask  200  has a transparent area and an opaque area. The opaque area blocks the passage of light. The transparent area allows light to pass through, thus shining on part of the photosensitive polymer layer  140  to generate cross-link. An appropriate light source is used to expose the photosensitive polymer layer  140  under the mask  200 , defining the orifices and exposing the through holes for the lead end of the metal conductive circuit. 
     As shown in  FIG. 5 , the pattern on the exposed photosensitive polymer layer  140  is developed to form the orifices and to expose the through holes for the lead end of the metal conductive circuit. 
     As shown in  FIG. 6 , the metal sacrifice layer  110  and the photo resist layer for electroforming are removed. Therefore, the metal conductive circuit  130  and the photosensitive polymer layer  140  are separated from the substrate  100  to form a soft circuit board with orifices. This above-mentioned method can quickly make the component to be packaged into an ink jet print head chip. The component includes several orifices and a metal conductive circuit, replacing the original orifice plate and TAB packaging plate. 
     As shown in  FIG. 7 , before removing the photoresist layer for electroforming the metal, the soft circuit board is turned over to form a passivation layer  150  on the surface of the metal conductive circuit  130  using photolithography. The photoresist layer is then removed at the same time when developing the pattern on the passivation layer  150 . 
     In particular, the metal sacrifice layer in the first embodiment can be substituted by another sacrifice layer made of other materials. When forming the metal conductive circuit using electroforming, a seed metal layer has to be formed on the surface of the sacrifice layer for the convenience of subsequent electroforming processes. Alternatively, one may use the photolithography method to make the metal conductive circuit directly. A metal layer is first deposited on the surface of the sacrifice layer, followed by photoresist coating, exposure, developing, and etching. 
     Moreover, the invention also disclosed a soft circuit board structure with orifices that integrates an ink chamber and a fluid channel. 
     Please refer to  FIGS. 8 through 11  for a second embodiment of the invention. The steps are the same as  FIGS. 1 through 4  in the first embodiment. First, a metal sacrifice layer is deposited on the surface of a substrate. A photoresist layer is then defined on the surface of the sacrifice layer. Afterwards, a metal conductive circuit is formed above the metal sacrifice layer by electroforming. A first photosensitive polymer layer is coated on the metal conductive circuit. After exposing the first photosensitive polymer layer using an appropriate light source and through a mask, orifices and through holes are exposed from the lead end of the metal conductive circuit are defined. 
     As shown in  FIG. 8 , a second photosensitive polymer layer  141  is formed on the surface  140  of the defined first photosensitive polymer layer  140 . An appropriate mask  200  is used to expose the second photosensitive polymer layer  141  to define the ink chamber and channel structures. 
     As shown in  FIG. 9 , the patterns on the second photosensitive polymer layer  141  and the first photosensitive polymer layer  140  are developed to form the structures of the orifices, through holes, ink chamber, and channel. 
     As shown in  FIG. 10 , the photoresist layer for the metal sacrifice layer  110  and electroforming the metal is removed, so that the metal conductive circuit  130 , the first photosensitive polymer layer  140 , and the second photosensitive polymer layer  141  are all separated from the substrate  100  to form a soft circuit board with orifices, ink chambers, and channels. 
     As shown in  FIG. 11 , one can also turn the soft circuit board over to form a passivation layer  151  on the surface of the metal conductive circuit  130  before removing the photoresist layer. The photoresist is removed when developing the passivation layer  151 . The passivation layer  151  is formed on the surface of the metal conductive circuit  130  other than the one attached with the first photosensitive polymer layer  140 . 
     This invention uses the photolithography technology to make orifices. Their roundness and thickness can be arbitrarily controlled. The quality of the component is much better than that of the prior art. One can also use different masks to make irregular orifices. Integrating the orifices and ink chamber together on the soft circuit board to form a single element can effectively reduce the cost. One does not need to make an extract orifice plate and to form the ink chamber on the chip. At the same time, the circuit board substrate, the orifices, and the ink chamber can be rapidly finished on the same platform and using the same method. 
     Certain variations would be apparent to those skilled in the art, which variations are considered within the spirit and scope of the claimed invention.