US20090170408A1

US20090170408A1 - Integrated Circuit Package Contact Cleaning

Info

Publication number: US20090170408A1
Application number: US11/967,415
Authority: US
Inventors: C.C. Lee; Leo Yu; W.L. Wang; Tser-Tsun Chui; C.S. Liao; Wade Chang
Original assignee: Texas Instruments Inc
Current assignee: Texas Instruments Inc
Priority date: 2007-12-31
Filing date: 2007-12-31
Publication date: 2009-07-02

Abstract

The invention provides methods and apparatus for automated contamination removal in association with integrated circuit manufacturing and testing. Disclosed embodiments include methods for cleaning electrical contacts of integrated circuit packages with steps for transporting the package from a first position to a second position and, during the transit, bringing the electrical contacts into engagement with one or more cleaning station. Aspects of the disclosed apparatus include a package transit chute for moving packages from a first position to a second position and one or more cleaning stations between the first and second positions. The cleaning stations further include one or more cleaning mats positioned for cleaning electrical contacts of packages transported in the chute.

Description

TECHNICAL FIELD

The invention relates to electronic semiconductor devices and manufacturing. More particularly, the invention relates to apparatus and methods for cleaning packaged microelectronic integrated circuit (IC) assemblies in association with manufacturing processes.

BACKGROUND OF THE INVENTION

Generally speaking, semiconductor devices such as integrated circuits (ICs) are manufactured by forming layered metallic circuit components and patterns on a semiconductor wafer. Numerous such ICs are formed on a single wafer. The individual ICs are separated from one another by a singulation process, such as sawing. Each IC is typically mounted on a metallic leadframe, and the IC-leadframe assembly is then encapsulated within a package. Package material, or “encapsulant” is commonly made from viscous or semi-viscous plastic or epoxy resin, which is cured to form a hardened protective cover to shield the protect the IC assembly from environmental hazards such as dust, heat, moisture, mechanical shock, and external electricity. Subsequent to packaging, the packaged IC assemblies are ordinarily subjected to testing and ultimately incorporated into electronic apparatus.
In general, IC packages undergo a deflashing process to remove foreign material, i.e., contamination, from the exposed contacts designed to provide electrical connections to the outside world. However, for many packages, for example, those employing leads plated with a combination of nickel, palladium, and gold (NiPdAu), there is no flawless deflashing process known in the arts. In the event the contacts are not sufficiently cleaned, the presence of contaminants on the contacts can cause problems with final testing or use due to interfering with necessary electrical contact between the leads or contact pads and test probes.
Due to these and other technological challenges, improved IC package cleaning apparatus and methods would be useful and surprisingly advantageous. The present invention is directed to overcoming, or at least reducing the effects of one or more of the problems known in the arts.

SUMMARY OF THE INVENTION

In carrying out the principles of the present invention, in accordance with preferred embodiments, the invention provides advances in the art with novel methods and apparatus directed to providing automated contamination removal for use in association with integrated circuit manufacturing and testing.
According to one aspect of the invention, methods for cleaning the contacts of a packaged integrated circuit include the step of transporting the package on a chute from a first position to a second position. Using one or more cleaning station positioned in the chute, the package contacts are cleaned.
According to another aspect of the invention, a preferred embodiment of a system for cleaning integrated circuit package contacts includes a package transit chute for moving packages from a first position to a second position. At least one cleaning station is located in the package transit chute between the first and second positions. The cleaning station includes at least one cleaning mat positioned for engaging, and cleaning contaminants from, the contacts of packaged integrated circuits transported in the chute.
According to yet another aspect of the invention, in an example of a preferred embodiment, one or more cleaning stations are included in the path of integrated circuit packages handled by automated handling equipment adapted for receiving the output of packaged IC manufacturing equipment.
According to still another aspect of the invention, in an example of a preferred embodiment, one or more cleaning stations are included in the path of packaged integrated circuits handled by handling equipment associated with package input to automated testing equipment.
The invention has advantages including but not limited to one or more of; improvements in manufacturing output and test quality, integration of cleaning with other processes, reduced processing time, higher yields, and reduced cost. These and other features, advantages, and benefits of the present invention can be understood by one of ordinary skill in the arts upon careful consideration of the detailed description of representative embodiments of the invention in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more clearly understood from consideration of the following detailed description and drawings in which:

FIG. 1 is a partial cutaway top front perspective view of a preferred embodiment of the invention showing a package transit chute and cleaning station in use with a DIP package;

FIG. 2 is a partial side view of a preferred embodiment of the invention as in FIG. 1 in use with DIP packages;

FIG. 3 is a close-up side view of a preferred embodiment of a cleaning station and DIP package workpiece as introduced in FIGS. 1 and 2;

FIG. 4 is a top front partial cutaway perspective view of an alternative preferred embodiment of the invention showing a package transit chute and cleaning station in use with a QFN package; and

FIG. 5 is a top perspective view of an alternative embodiment of the invention illustrating an example of a cleaning station in use with a QFP package.

References in the detailed description correspond to like references in the various drawings unless otherwise noted. Descriptive and directional terms used in the written description such as first, second, top, bottom, upper, side, etc., refer to the drawings themselves as laid out on the paper and not to physical limitations of the invention unless specifically noted. The drawings are not to scale, and some features of embodiments shown and discussed are simplified or amplified for illustrating principles and features, as well as anticipated and unanticipated advantages of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

While the making and using of various exemplary embodiments of the present invention are discussed herein, it should be appreciated that the present invention provides inventive concepts which can be embodied in a wide variety of specific contexts. It should be understood that the invention may be practiced with semiconductor device package handling and transfer methods and mechanisms of various types, configurations, and materials without altering the principles of the invention. For purposes of clarity, detailed descriptions of functions and systems familiar to those skilled in the semiconductor manufacturing equipment and processing arts are not included. In general, the invention provides apparatus and methods for cleaning electrical contacts on integrated circuit packages.
A system for cleaning semiconductor device package contacts according to preferred embodiments of the invention is illustrated in the perspective view of FIG. 1. The cleaning system 10 may be used in combination with various semiconductor device package manufacturing, handling, and testing processes and equipment. A partial side view of this example of the invention is also shown in a companion illustration in FIG. 2. Preferably, the system 10 may be used for cleaning devices as they are transported from one place to another in association with handling processes. For example, assuming that packaged devices 12 (not part of the invention) are being transported from a first position 14 to a second position 16 by automated handling equipment, the system 10 may be inserted into the process as shown and described. Examples of suitable implementations include the interception of devices output from trimming machinery, or as they are input to automated test equipment. The dual inline (DIP) device 12 shown in this example is moved on a transit chute 18, typically by the force of gravity or compressed air, indicated by arrow 20, or a combination of suitable forces. Those familiar with the arts will recognize that the systems and methods described may be used for other types of semiconductor device packages with suitable modifications. The transit chute 18 typically includes channels 22 for guiding the devices 12 as they are transported from point to point (e.g., 14, 16). A cover 24 may also be included with some transit chutes 18 used in the arts. A cleaning station 26 is provided in the chute 18 in the path 20 of the devices 12. In some cases, multiple cleaning stations may be used. The cleaning station 26 has a cleaning mat 28, or numerous cleaning mats, positioned for making physical contact with, i.e., engaging, the exposed electrical contacts, in this case leads 30, of packaged devices 12 transiting the chute 18. The physical contact of the leads 30 with the cleaning mat 28 acts to clean contaminants from the leads 30 as they pass.
The cleaning mats 28 have characteristics advantageous for cleaning contaminants such as debris particles from the leads 30. Preferably, the cleaning mats 28 have a cleaning surface 32 which includes material such as alumina (Al₂O₃) or other suitable abrasive. Now referring primarily to FIG. 3, an example of the structure of a preferred embodiment of a cleaning station 26 and cleaning mat 28 in accordance with the invention is depicted in further detail. In this example of a preferred embodiment, an adhesive layer 34 provided on the “back” side of a polyethylene terephthalate (PET) film 36 is used to secure the mat 28 in the desired location at the cleaning station 26. A relatively soft pliable material 38, such as polyurethane foam on the opposing side of the film 36 is preferably impregnated with abrasive particles 40, e.g., alumina, held in place with a suitable resin 42. The preferred structure of the cleaning mat 28 is advantageous for the removal of contaminant particles, such as “micro dust”, from the electrical contacts, e.g., leads 30, brought into physical contact with it.
FIG. 4 is a partial top front perspective view of an alternative preferred embodiment of the invention showing a package transit chute 18 and cleaning station 26 in use with a QFN package 12 (not part of the invention). The package 12 transits the chute 18 from a first position 14 to a second position 16, propelled by a force (as indicated by arrow 20), preferably gravity or compressed air, causing the package 12 to pass over the cleaning station 26. The chute 18 is similar to that of the embodiment shown and described for use with DIP packages, but is adapted for the transportation of QFN packages. The electrical contacts, e.g. contact pads 44, of the QFN package 12 pass over one or more cleaning mats 28, in this example three cleaning mats 28, of the cleaning station 26. The cleaning mats 28 are configured for cleaning the contact pads 44 of the package 12 as it is moved past, cleaning contaminants from the contact pad 44 surfaces. As with other embodiments of the invention, the cleaning station 26 may be placed so that packages 12 may be cleaned in transit from a first position and a second position, in this case the opposite ends 14, 16 of the chute 18.
In alternative embodiments, the invention may also be used with pick-and-place package handling equipment. As illustrated in the example of FIG. 5, a top perspective view representative of an embodiment of such a system 10 is shown. An idle stage 46, as sometimes used in the arts to place packages 12 for transit from one processing point, e.g. trimming, to another, e.g., testing. The package 12 is placed by pick-and-place equipment (not shown) known in the arts on the idle stage positions 46 provided with cleaning stations 26. The cleaning stations 26 are provided with cleaning mats 28 so that the contacts of the packages, in this case the leads 30 of QFP packages 12 (not part of the invention) are placed in physical contact with the cleaning mat 28. Subsequently, when the packages 12 are removed from the idle stage 46, they are freer of contaminants than when they arrived due to the cleaning action of the surface 32 of the cleaning mat 28 when the contacts 30 are brought into physical contact with the cleaning station 26.
There are many potential embodiments of the invention, which may be implemented in a variety of alternative applications. For example, the invention may be used to provide cleaning of package contacts at the output of production equipment such as lead trimmers for DIP or QFP packages or in association with deflashing procedures used after block molding QFN, DIP, or QFP packages. The invention may also be used with various testing processes by incorporation of electrical contact cleaning apparatus and methods with automated test equipment (ATE), and device handling equipment. In any case, using the principles and practices of the invention disclosed, the electrical contacts of the package under production or testing, become cleaner as a result of their encounter with the surface of the cleaning mat(s), which preferably include abrasive properties as well as particle-trapping properties for removing contaminants from electrical contacts.
The methods and systems of the invention provide one or more advantages including but not limited to providing for the cleaning of packaged semiconductor device contacts in association with handling during manufacturing or testing processes. Potential advantages include increased throughput, increased testing efficiency, and reduced costs. While the invention has been described with reference to certain illustrative embodiments, those described herein are not intended to be construed in a limiting sense. For example, variations or combinations of steps or materials in the embodiments shown and described may be used in particular cases without departure from the invention. Various modifications and combinations of the illustrative embodiments as well as other advantages and embodiments of the invention will be apparent to persons skilled in the arts upon reference to the drawings, description, and claims.

Claims

1. A method for cleaning electrical contacts of an integrated circuit package, comprising the steps of:

transporting the package from a first position to a second position; and

while the package is in transit, bringing the electrical contacts into physical contact with one or more cleaning station.

2. The method of claim 1 wherein the step of transporting the package further comprises causing the package to move using primarily the force of gravity.

3. The method of claim 1 wherein the step of transporting the package further comprises causing the package to move using primarily the force of compressed air.

4. The method of claim 1 wherein the step of transporting the package from a first position further comprises receiving the package from the output of package manufacturing equipment.

5. The method of claim 1 wherein the step of transporting the package to a second position further comprises inputting the package to testing equipment.

6. A system for cleaning integrated circuit package electrical contacts comprising:

a package transit chute for moving packages from a first position to a second position; and

at least one cleaning station located in the package transit chute between the first and second positions, the cleaning station further comprising one or more cleaning mats positioned for engaging electrical contacts of packages transported in the chute, whereby engagement between the electrical contacts and the one or more cleaning mats acts to clean contaminants from the electrical contacts.

7. The system of claim 6 wherein the package transit chute is configured for the transportation of DIP packages.

8. The system of claim 6 wherein the package transit chute is configured for the transportation of QFN packages.

9. The system of claim 6 wherein the package transit chute is configured for the transportation of QFP packages.

10. The system of claim 6 wherein the one or more cleaning mats further comprise pliable material having embedded abrasive particles.

11. The system of claim 6 wherein the one or more cleaning mats further comprise an adhesive layer on one side of a polyethylene terephthalate film and polyurethane foam on the opposing side of the polyethylene terephthalate film, wherein abrasive particles are secured to the polyurethane foam with suitable resin.

12. The system of claim 6 wherein the one or more cleaning mats further comprise pliable material having embedded alumina particles.

13. A system for cleaning integrated circuit package electrical contacts comprising:

an idle stage for receiving packages in transit from a first position to a second position; and

at least one cleaning station located in the idle stage, the cleaning station further comprising one or more cleaning mats positioned for engaging electrical contacts of packages placed in the idle stage, whereby engagement between the electrical contacts and the one or more cleaning mats acts to clean contaminants from the electrical contacts.

14. The system of claim 13 wherein the idle stage is configured for receiving one or more DIP packages.

15. The system of claim 13 wherein the idle stage is configured for receiving one or more QFN packages.

16. The system of claim 13 wherein the idle stage is configured for receiving one or more QFP packages.

17. The system of claim 13 wherein the one or more cleaning mats further comprise pliable material having embedded abrasive particles.

18. The system of claim 13 wherein the one or more cleaning mats further comprise an adhesive layer on one side of a polyethylene terephthalate film and polyurethane foam on the opposing side of the polyethylene terephthalate film, wherein abrasive particles are secured to the polyurethane foam with a suitable resin.

19. The system of claim 13 wherein the one or more cleaning mats further comprise pliable material having embedded alumina particles.