Print head for ejecting liquid droplets

Details Print head for ejecting liquid droplets Print head for ejecting liquid droplets

2000-04-10

2002-08-20

Edwards, Laura (Department: 1734)

Metal fusion bonding

Including means to apply flux or filler to work or applicator

C228S033000, C228S260000, C228S261000, C347S001000, C347S051000, C347S054000, C222S595000, C222S603000

Reexamination Certificate

active

06435396

ABSTRACT:

FIELD OF THE INVENTION
This invention relates generally to the field of liquid ejection and specifically to a print head for ejecting liquid droplets.
BACKGROUND OF THE INVENTION
There are a growing number of technological applications that require means to inexpensively and precisely deposit small, controlled volumes of liquids. One of these important technologies involves the deposition of small solder bumps on the bond pads of integrated circuits to assist in their subsequent packaging. One of the most efficient and compact packaging schemes utilizing such solder bumps is the so-called flip chip or C4 (i.e., the Controlled Collapse Chip Connection) approach. This technology eliminates the need to wire bond connections from the bond pads to a packaging lead frame, and offers more connection pads, higher speeds, smaller die sizes, and improved heat transfer. See A. J. Babiarz, “Key Process Controls for Underfilling Flip Chips,” pp. 77-83, Solid State Technology, April 1997, which is incorporated herein in its entirety. Although C4 technology is somewhat costly in terms of time, materials, and equipment, and although it presents certain environmental issues, the use of solder bumped integrated circuits is growing at a significant rate. See P. Jones & James Blaha, “Bumped Wafers: Worth Their Weight In Gold?” pp. 54-57, Advanced Packaging, January 1999, which is incorporated herein in its entirety.
The importance of this technology is underscored by the fact that a large number of companies and governmental agencies have formed the “MicroFab Consortium” for the purpose of exploring and developing novel methods for applying solder bumps and other materials to integrated circuits, hybrids, optical, and other devices. The literature suggests that MicroFab has successfully developed manufacturing prototypes of piezoelectrically actuated print heads for ejecting low-melting point solder balls of well-defined sizes at rates approaching a couple of kilohertz (kHz). Although piezoelectric-based printers have several attractive characteristics, they are limited by the fact that piezoelectric strengths decrease rapidly with rising temperatures and vanish at their Curie temperatures. Curie temperatures of useful ceramics are well under 300C. Thus the ability to manipulate solder viscosity and surface tension by raising temperature is limited in such print heads. Other significant disadvantages to using piezoelectric-based print heads includes their complexity and the great difficulty in mass producing them in large, inexpensive, relatively light weight arrays.
Thus, a need exists for a print head that is functional over a wider range of temperatures to eject a greater variety of solders, brazes and other materials. Preferably, such a print head would be easily produced in large quantities out of inexpensive materials such as silicon, glasses, and metals.
SUMMARY OF THE INVENTION
In view of the foregoing considerations, an embodiment of the present invention includes a disposable print head for ejecting controlled amounts of liquid (e.g., solder) at a high rate onto the surface (e.g., an integrated circuit) in close proximity to the ejecting source. The embodiment involves the use of a controlled burst of gas that is developed by rapidly heating a metallic hydride film with a laser to disassociate the hydrogen therefrom. The pressure created by the burst of hydrogen gas is used to eject an amount of a liquid (e.g., a solder) from an appropriate conduit that is fed liquid from a reservoir. The surfaces in the print head that contact the liquid are coated to assist in priming the print head for a subsequent ejection event.


REFERENCES:
patent: 4607267 (1986-08-01), Yamamuro
patent: 5364011 (1994-11-01), Baker
patent: 5377961 (1995-01-01), Smith et al.
patent: 5401191 (1995-03-01), Krage
patent: 5613633 (1997-03-01), French et al.
patent: 5779971 (1998-07-01), Tsung Pan et al.
patent: 5876615 (1999-03-01), Predetechensky
patent: 5894980 (1999-04-01), Orme-Marmarelis et al.
patent: 5988480 (1999-11-01), Farnworth
patent: 6015083 (2000-01-01), Hayes
patent: 6076723 (2000-06-01), I-Tsung Pan
patent: 6121131 (2000-09-01), Eldridge
patent: 6216966 (2001-04-01), Prendergast et al.
patent: 6224180 (2001-05-01), Pham-Van-Diep
patent: 6288437 (2001-09-01), Forbes
patent: 6322202 (2001-11-01), Ahn
“Key Process Controls For Underfilling Flip Chips”—Alec J. Bablarz, Asymtek, Carlsbad, CA (Solid State Technology, Apr. 1997, pp. 77-78, 81, 83).
“Bumped Wafers—Worth Their Weight In Gold?”—Paul Jones and Jim Blaha (Advanced Packaging, Jan. 1999, pp. 55-57).
“Antifuse Structures, Methods, and Applications”; Ser. No. 09/259,363; Filed Feb. 26, 1999.
“Fluid Statics”—Eugene A. Avallone and Theodore Baumeister III, Editors (Marks' Standard Handbook For Mechanical Engineers).
“Gases and Metals”—Francis J. Norton (pp. 516-559).
“Flow of Gases Through Tubes and Orifices”—David G. Worden (pp. 80-117).

Affiliated with

Also associated with

Rating

Print head for ejecting liquid droplets does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Print head for ejecting liquid droplets, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Print head for ejecting liquid droplets will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2960288