High volume fluid head

Details High volume fluid head High volume fluid head

1999-12-20

2002-05-07

Carrillo, Sharidan (Department: 1746)

Cleaning and liquid contact with solids

Processes

For metallic, siliceous, or calcareous basework, including...

C134S006000, C134S007000, C134S009000, C134S015000, C134S025100, C134S025400, C134S026000, C134S032000, C134S036000, C134S042000, C134S067000, C134S072000, C134S131000, C451S038000, C451S039000, C451S075000, C451S101000, C451S102000

Reexamination Certificate

active

06383303

ABSTRACT:

BACKGROUND OF THE INVENTION
(1) Field of the Invention
The invention relates to the fabrication of integrated circuit devices and, more particularly, to an apparatus for increasing the flow of cleaning fluid while not disturbing the position of the cleaned object due to cleaning fluid impact.
(2) Description of the Prior Art
Improved semiconductor device performance has for many years now been pursued by decreasing device dimensions while at the same time increasing device density. Increased device density not only applies to decreased device feature size and to decreased separation between the interconnects between device features, increased device density is also frequently achieved by denser packaging of individual devices onto device carrier surfaces. One of the more commonly applied means to achieve denser device packaging is the Printed Circuit Board (PCB) or by mounting semiconductor devices on individual substrates. The preferred method for attaching semiconductor devices to PCB's or individual substrates is soldering whereby points of electrical contact of individual devices are mechanically and electrically connected to interconnect metal lines and/or bond pads that have been provided for this purpose on the surface of the PCB or the individual substrate.
To enhance the reliability and uniformity of the solder connection that is established in this manner, solder fluxes are first deposited on the surface of the substrate. These solder fluxes must be selected such that they introduce no negative impact on the surface of the substrate, they must for instance have low corrosion and must be of long life expectancy. Of great importance in this respect is also the selection of the medium that is used to clean the solder fluxes from the surface of the substrate and the reaction that these cleaning agents have with the solder flux during the process of cleaning the substrate. In the early stages of PCB or substrate manufacturing, chlorinated hydrocarbon and chlorofluorinated solvents were mostly used to removed rosin fluxes, these cleaning agents have however been replaced due to the toxic effect of chlorinated hydrocarbon and chlorofluorinated solvents and the consequent highly negative impact that the disposal of chlorinated hydrocarbon and chlorofluorinated solvents has on the environment. As alternatives to the chlorinated hydrocarbon and chlorofluorinated solvents terpene compounds have been used extensively in recent years whereby commercially available cleaning equipment is available that is mostly directed at a cleaning process that uses terpene compounds as the cleaning agent.
In the assembly of semiconductor devices, Printed Circuit Boards (PCB's) or individual substrates have been applied extensively and for many years. The substrates serve a number of functions in assembling semiconductor components such as providing mechanical support for a large structure, heat dissipation and the ability to significantly increase the input/output interconnect capability of an assembly. The use of packaging substrates has led to related technologies and has at the same time had a significant impact on the packaging of the individual chips that are mounted onto the substrates. Semiconductor dice can be attached to a substrates using Chip On Board (COB) techniques, these COB techniques include flip chip attachment, wirebonding, and tape automated bonding (TAB). Flip chip attachment techniques consist of attaching a flip chip to a PCB or to any other substrate. The flip chip method of packaging has been specifically designed to utilize and enhance the advantages that mounting on a substrate offers. A flip chip is a semiconductor chip that has a pattern or arrays of terminals spaced around an active surface of the flip chip for face down mounting of the flip chip to a substrate. A flip chip can be provided with a number of different contact point arrangements such as the Ball Grid Array (BGA), the Slightly Larger than Integrated Circuit Carrier (SLICC) and the Pin Grid Array (PGA). With the BGA, an array of minute solder balls is arranged on the surface of the flip chip, this array of solder balls attaches the flip chip to the substrate. The arrangement for the SLICC is similar to the BGA but the solder ball pitch and diameter of the contact balls is smaller than for the BGA. For the PGA, an array of small pins extends perpendicularly from the attachment surface of a flip chip, whereby the protruding pins align with a specific arrangement of metal interconnect lines on a printed circuit board or on another substrate for attachment. It is clear that, for the BGA and SLICC type of flip chip, the solder or other conductive ball arrangement on the flip chip must be a mirror image of the connecting bond pads on the printed circuit board in order to establish precise connections between the flip chip and the board. The flip chip is bonded to the printed circuit board by refluxing the solder balls. The solder balls may also be replaced with a conductive polymer. With the PGA, the pin arrangement of the flip chip must be a mirror image of the recesses on the printed circuit board. After insertion, soldering the pins into place generally bonds the flip chip. While in most cases the interconnect wiring that is provided on the printed board consists of a suitable metal, printed board wiring can also consist of polyimide, glass reinforced epoxy and ceramics.
After semiconductor devices have been attached to a substrate, the substrate is, as previously indicated, cleaned to remove any remaining residue from the surface of the board. This process typically involves washing of the substrate in a solvent that is selected such that residue on the surface of the board is dissolved in the solvent after which the solvent is removed from the cleaning apparatus. This however results in a solvent that may contain chemicals that are harmful to the environment, which requires special treatment of the solvent solution. One of the methods that are being used to prevent impurities in a solvent is to apply solid carbon dioxide (CO
2
) particles to the surface that needs to be cleaned. These particles, upon striking the surface that needs to be cleaned, sublimate in the process of which residue on the surface of the board is absorbed and removed from that surface. The use of CO
2
however does result in the build-up of an electrostatic charge on the surface of the board that is being cleaned. This electrostatic charge must either be prevented from building up or must be removed before the board is passed on to further processing steps. The former can be accomplished by grounding the board while it is being treated by the CO
2
, the latter can at least partially be accomplished by mixing the CO
2
with another substance, such as a water mist, that prevents or alleviates the accumulation of the electrostatic charge during the cleaning process.
Solvents that are used to clean printed circuit boards must meet a number of requirements that relate to both the effectiveness of the cleaning operation and to the toxic nature of the waste products that are produced during the cleaning operation. The by-products of the cleaning operation must not result in products that are contaminating, difficult to degrade, have a long retention period and have in any other way an undesirable impact on the environment where they are disposed. For these reasons, chlorinated hydrocarbon and chlorofluorinated solvents have largely been abandoned even though these substances have excellent qualities as solvents of rosin flux and other by-products of solder operations. In recent years, terpene compounds appeared to be an attractive alternative to the previous generation of solvents, this is because terpene compounds offer significant advantages for the cleaning operation. It is for instance known that terpene compounds are widely available and are safe enough that they have been used as a food additive. Terpene compounds are also readily biodegradable and can readily be handled be regular waste disposal facilities. Terpene compou

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