Apparatus and method for detecting and removing contaminants on mold for packaging electronic components

Abstract

The invention relates to a cleaning device for detecting and removing contaminants on a mold for encapsulating an electronic component, in particular a semiconductor, the cleaning device comprising: a light source for illuminating a surface of the mold; an optical detector for detecting the irradiated contaminants on the surface of the mold; a movable cleaner for removing contaminants; and a controller for the cleaner. The invention also relates to a cleaning method for such a mould.

Description

Technical Field

[0001] The invention relates to a cleaning device and a method for detecting and removing contaminants on a mold for packaging electronic components, especially semiconductors. Background Art

[0002] Electronic components are used on a large scale and may be formed, for example, of diodes (e.g., light emitting diodes or LEDs), transistors, integrated circuits (ICs / chips), chip-based sensors for detecting force, pressure, fingerprints, light and images, and chip-based actuators (MEMS; micro-electromechanical systems) and / or other types of semiconductors. The electronic components may typically be mounted on a carrier (also referred to as a substrate). The carrier may be formed of, but not limited to, a wafer, a lead frame, or a (printed circuit board) board.

[0003] When electronic components are incorporated into electronic devices, it is often necessary to at least partially shield (encapsulate) the electronic components, for which reason a housing may be molded around the electronic components. The most common molding techniques for encapsulating such small electronic components are transfer molding and compression molding. The electronic components may be completely embedded in such a molded housing, but for the functionality of the electronic components, the components may also be at least partially free of the housing, to allow access to the electronic components, for example for detection purposes, and / or to cool the electronic components during use. Partly due to increasing miniaturization, the demands for shape accuracy of encapsulated electronic components are very high, and even more so due to the high demands for quality and accuracy of encapsulated electronic components, it is important to achieve encapsulation with high accuracy.

[0004] For good molding results of fully or partially encapsulated electronic components (e.g. semiconductors), it is essential that the mold is substantially clean before the molding process begins. It is well known to clean the mold at the beginning of the molding cycle, when the mold parts are open (placed at a mutual distance) and before the electronic components, usually attached to a carrier, are placed in the mold. Cleaning can be performed by complete brushing, possibly combined with extraction of loose contaminants. After cleaning, the mold parts are closed and the molding process can be started by bringing liquid molding material into the mold opening.

[0005] The contaminants may have a random distribution on the mold surface and may consist, for example, of residues from previous molding actions and / or suspended particles from the environment. The contaminants may typically be in the form of particles, spheres, or blocks. The size of the contaminants may be (but not limited to) less than 250 μm, less than 100 μm, or even less than a few microns. These contaminants may also have a tendency to adhere to the mold surface due to adhesion (e.g., EMC epoxy), electrostatic charging, and / or gravity.

[0006] A problem with the prior art is that removing contaminants from a mold used to package electronic components is not a controlled process and / or the removal of contaminants is often incomplete, so that remaining contaminants may hinder high-quality packaging of the electronic components. Summary of the invention

[0007] The object of the present invention is therefore to overcome these drawbacks and to provide a device and a method for detecting and removing contaminants on moulds for packaging electronic components which allow a better and more controlled cleaning of such moulds.

[0008] In order to solve the problems of the prior art, the present invention provides a cleaning device for detecting and removing contaminants on a mold for packaging electronic components, especially semiconductors, the cleaning device comprising: at least one light source, the at least one light source is used to irradiate the mold surface with at least one light beam; at least one optical detector, the at least one optical detector is used to detect the position of at least one irradiated contaminant on the mold surface; a relatively movable cleaner for removing contaminants from the mold surface; and a controller, the controller is used to drive the relatively movable cleaner to the detected position. Preferably, the at least one light source is a laser.

[0009] The cleaning device utilizes a light beam, which is defined here as a directional projection of light energy radiated from a light source, or as an alternative definition, a line of electromagnetic radiation (massless elementary particles called photons) that flows essentially in one direction. The light beam irradiating the mold surface will cause scattering of light (and therefore also in a direction different from the light beam) when the light beam irradiates the contaminants (particles) located on the mold surface. This scattering of light will be relatively easily detected by an optical detector (e.g., a visual camera), so the sensitivity of the optical detector is enhanced due to the use of the light beam in combination with the optical detector. The advantage of the cleaning device according to the present invention is that small contamination particles that are usually invisible to the optical detector can now also be seen. The enhanced visual detection capability of the contaminants enables the manipulation (control) of the cleaner so that it is driven to move to those contaminated mold surface positions (e.g., X, Y positions detected on the mold surface). After the relatively movable cleaner reaches the contaminated position, the relatively movable cleaner can remove the contaminants. Due to the enhanced sensitivity of visual detection, the present cleaning device will be able to improve the cleaning of the mold surface, which will improve the quality of the resulting packaged electronic components. And since only the contaminants have to be removed rather than the entire surface having to be cleaned, cleaning is efficient (saving time) and the chances of new contamination occurring during the cleaning phase are therefore also limited. Furthermore, the cleaner according to the invention is able to verify the state of the mould surface to provide certainty of cleanliness.

[0010] By "relatively movable cleaner" it is indicated that the cleaner may be movable and the mould surface may be stationary, but the cleaner may also be stationary and the mould surface may be movable, or alternatively both the cleaner and the mould surface may be movable.

[0011] In a particular embodiment, at least one light source is a laser. Laser sources typically have a very high light emission and are typically also provided as a (laser) beam. Due to the high intensity, the scattered light effect of irradiating the contaminants will have a relatively high intensity and thus detecting the locations where the light scattering occurs will be easier to detect, resulting in a cleaning device with enhanced sensitivity. In order to enhance the sensitivity of the cleaning device according to the invention, the ambient light can be (at least partially) separated from the mold surface to be cleaned, as the ambient light can define the detection accuracy.

[0012] In another embodiment, at least one of the light beams is a flat beam. With a flat beam, reference is made to a light beam having a cross-section whose width is greater than its height. With such a flat beam, a wider portion of the mold surface can be irradiated at once. Thus, a flat beam can reduce the cycle time for mold surface inspection. Likewise, irradiation of the mold surface can be a less critical sub-process. Additionally, a flat beam having a fairly high (e.g., a height of several millimeters) can be advantageous, since a beam contacting the mold surface at an acute angle will then illuminate a larger area of ​​the mold surface. Such a beam can be generated by using a laser diode with an adjustable focus.

[0013] The beam can be stationary to illuminate the entire mold surface at once, but it is also possible to make the beam movable relative to the mold surface. The beam illuminating the entire mold surface can be a sub-process performed sequentially, for example so that the beam is illuminated on the mold surface. The entire surface can be illuminated with a single beam moving over the surface, but depending on the size of the mold surface and the size of the beam, the beam can also be moved multiple times over different strips on the mold surface.

[0014] At least one light source may be positioned to illuminate the mold surface with a light beam at an acute angle, for example less than 30 degrees, preferably less than 20 degrees, more preferably less than 10 degrees, most preferably less than 5 degrees. An advantage of this type of illumination (also known as flood illumination or grazing illumination) is that light scattering resulting from contact of the light beam with contaminants is well distinguished from the light beam itself and is therefore relatively easy to detect.

[0015] The controller may include a memory for storing the position of the detected pollutant, which enables the detection of the pollutant to be decoupled from the removal of the detected pollutant. Subsequently, the relatively movable cleaner can be relatively movable along the surface of the mold surface to be distributed, so that the detected pollutant can be removed from the mold surface. In order to remove this pollutant, the relatively movable cleaner can be provided with a blower head, a suction head, a brush sweep head, a laser head, and / or a scraping head. The automatic cleaning operation can be activated via directional air flow (air wall), suction (vacuum cleaner), brush sweep, mechanical removal (scraper), and / or laser cleaning. In another embodiment, the relatively movable cleaner can also be provided with a combination of at least a suction head and a brush sweep head, a laser head, and / or a scraping head, and the suction head enables the brush sweep head, the laser head, and / or the scraping head to move along the suction head. Such an embodiment enables to remove pollutants further away from the mold surface by suction from the brush sweep head, the laser head, and / or the scraping head. For effective and efficient cleaning, the relatively movable cleaning means have a contact area preferably at least 5 mm wide.The scrapers of the scraper head may also have a designed tilt play to produce an accurate contact surface and an effective scraping front.

[0016] The cleaner according to the invention can also be implemented in dual form (with back-facing light sources, optical detectors, and relatively movable cleaners) for dual detection and removal, which means dual detection and removal of contaminants simultaneously from surfaces of opposing mold parts with facing surfaces. Such an embodiment enables simultaneous cleaning of facing sides of opposing (open) mold parts, thereby limiting cycle times.

[0017] The present invention also provides a cleaning method for detecting and removing contaminants on a mold for packaging electronic components, especially semiconductors, comprising the following method steps: A) irradiating the mold surface of the mold for packaging electronic components with at least one light beam; B) detecting the position of the irradiated contaminants on the mold surface; and C) manipulating a relatively movable cleaner to remove the detected contaminants. By this method, the advantages as described above with respect to the cleaning device according to the present invention can also be achieved, and these advantages are therefore included here by reference. The method can be performed relatively with a combination of readily available components and is able to improve the quality of the packaged electronic components, which additionally provides clarity / certainty of the cleaning state of the mold surface cleaned by the method according to the present invention.

[0018] As described above, the mold surface can be preferably irradiated with a laser beam, because such a light source has high intensity and can be directed in a beam, more preferably a flat beam. The beam can movably irradiate the mold surface so that the entire surface of the mold to be cleaned can be illuminated, and in order to improve the visibility of the contaminants, the beam can irradiate the mold surface at an acute angle, for example less than 30 degrees, preferably less than 20 degrees, more preferably less than 10 degrees, and most preferably less than 5 degrees. The advantage of such acute angle illumination relative to frontal illumination of the mold surface is that less obvious roughness and scratches of the mold surface can be found. Subsequently, the position of the detected contaminant can be stored, which helps to move the cleaner relative to the surface of the mold surface to the position of the detected contaminant.

[0019] In order to further enhance the cleaning capabilities of the method according to the invention, a dual detection method can be used to detect areas where contaminants may be located. In a first detection step, areas with potential contaminants (not yet irradiated) can be detected, after which a second detection step can be performed, in which areas with potential contaminants are irradiated. This enables the background information (detected during the first detection step) to be removed from the information collected during the second detection step, thus enabling a higher level of detection and thus enhancing the cleaning results.

[0020] A relatively movable cleaner located at the location where contaminants are detected can remove these contaminants by suction, blowing, brushing, and / or mechanical engagement. In addition, not only the location of the detected contaminants can be stored, but also the location of the cleaning area, the scratch area, the acceptable irregularity of operation, or the location of the exclusion area for cleaning (e.g., the area with the mold vacuum hole) can be stored to prevent "false" detection. These contaminants can move in the outward direction of the mold surface to be cleaned, and if they are not guided away from the mold area to be cleaned, they can be removed in two or more subsequent steps.

[0021] The method according to the invention can be carried out by using the cleaning device according to the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will be further explained based on the non-limiting exemplary embodiments shown in the following figures. Corresponding elements are indicated by corresponding reference numerals in the figures. Herein is shown: Figure 1 is a schematic diagram of a first portion of a cleaning device according to the present invention; Figure 2 is a schematic diagram of a second part of a cleaning device according to the present invention, the second part being similar to Figure 1 The first parts shown together form a complete cleaning device according to the invention; Figure 3 is a cross-sectional side view of an optional scraper head portion of a cleaning device according to the present invention; Figure 4 is a schematic diagram of a scraper during a cleaning operation; and Figure 5 is a schematic diagram of the process steps of a cleaning method for detecting and removing contaminants according to the present invention. DETAILED DESCRIPTION

[0023] Figure 1 A schematic diagram of a first part of a cleaning device 1 according to the invention is shown, in which a mold surface 2 is illuminated by four light sources 3 (here lasers). Since the laser rays of light 4 irradiate the contaminant 5 from the side (seen from the surface of the mold surface 2), the laser light is deflected, and the deflected light 6 enables a camera 7 to detect the contaminant 5 on the mold surface 2 relatively simply (when compared to the case where no lateral illumination of the contaminant 5 is used). After the position of the contaminant 5 on the mold surface 2 (e.g. X, Y coordinates) is detected, these positions (X, Y coordinates) are recorded. 1 , Y 1 , X 2 , Y 2 , ...) are stored in database 8.

[0024] Figure 2 The second part of the cleaning device 1 according to the invention is shown. Figure 1 The first part shown together constitutes a complete cleaning device 1. Here, the mold surface 2 with the assigned contaminants 5 is cleaned by a cleaner 9 which is relatively movable relative to the mold surface 2. The computer 10 is fed with the distribution of the detected contaminants 5 from the database 8. The computer (controller) 10 controls the controller 11 so that the cleaner moves relative to the mold surface 2 in the X, Y direction (see arrows). Figure 2 In the embodiment, the mold surface is stationary, but as an alternative, the mold surface can also be moved by the computer 10. Using a cleaner (here a brush or a broom), the contaminants 5 can be moved outwards (see arrow P 1 ), away from the operating part of the mold surface 2.

[0025] Figure 3 A sectional side view of a cleaning device embodied as a scraper head 12 is shown. Here, a central scraper element 13 is surrounded by an air channel 14, through which an air flow can be supplied. Such a scraper head 12 combines two cleaning technologies; scraping and blowing.

[0026] exist Figure 4 , schematically shows a scraper 15 during a cleaning operation, wherein contaminants 5 on the mold surface 2 are removed by the scraper 15 (see arrow P 2), the deflected scraper 15 provides a sharp contact front 16.

[0027] Figure 5 A schematic diagram 20 of process steps of a cleaning method for detecting and removing contaminants 5 on a mold surface 2 according to the present invention is shown. In process step A, the mold surface 2 of a mold for packaging electronic components is irradiated with at least one light beam. In a subsequent process step B, the position of the irradiated contaminants on the mold surface is detected and the position of the contaminants is stored in a database 8. In the next process step C, a relatively movable cleaner is manipulated based on the position information retrieved from the database 8 to remove the detected contaminants 5 from the mold surface 2. In addition to the process described here, an initial detection of the mold surface can also be included to enable background information to be removed from the information collected during the second (irradiation) detection step.

Claims

1. A cleaning device for detecting and removing contaminants on a mold for packaging electronic components, especially semiconductors, the cleaning device comprising: - at least one light source for illuminating the mold surface with at least one light beam; - at least one optical detector for detecting the position of at least one irradiated contaminant on the mold surface; - a relatively movable cleaner for removing contaminants from the mold surface; as well as - A controller for driving the relatively movable cleaning device to the detected position.

2. The cleaning device according to claim 1, characterized in that The at least one light source is a laser.

3. The cleaning device according to claim 1 or 2, characterized in that: The at least one light beam is a flat light beam.

4. The cleaning device according to any one of the preceding claims, characterized in that The light beam impinges upon the surface of the mold surface.

5. Cleaning device according to any one of the preceding claims, characterized in that The light beam is a relatively movable light beam.

6. Cleaning device according to any one of the preceding claims, characterized in that The at least one light source is positioned to illuminate the mold surface with a light beam at an acute angle.

7. The cleaning device according to claim 6, characterized in that: The acute angle is less than 30 degrees, preferably less than 20 degrees, more preferably less than 10 degrees, and most preferably less than 5 degrees.

8. Cleaning device according to any one of the preceding claims, characterized in that The controller includes a memory to store the locations of detected contaminants.

9. Cleaning device according to any one of the preceding claims, characterized in that The relatively movable cleaner is capable of moving along the surface of the mold surface.

10. Cleaning device according to any one of the preceding claims, characterized in that The relatively movable cleaning device is provided with a blower head, a suction head, a brush head, a laser head and / or a scraping head.

11. The cleaning device according to claim 10, characterized in that The brush head, laser head, and / or scraping head of the relatively movable cleaner can move along the suction head.

12. A cleaning method for detecting and removing contaminants on a mold for packaging electronic components, especially semiconductors, the cleaning method comprising the following method steps: A) irradiating a mold surface of a mold for encapsulating electronic components with at least one light beam; B) detecting the location of the irradiated contaminants on the mold surface; and C) Manipulating the relatively movable cleaner to remove the detected contaminants.

13. The cleaning method according to claim 12, characterized in that: The mold surface is irradiated with a laser beam.

14. The cleaning method according to claim 12 or 13, characterized in that: The light beam is movable to illuminate the mold surface.

15. The cleaning method according to any one of claims 12 to 14, characterized in that: The beam strikes the mold surface at an acute angle.

16. The cleaning method according to claim 15, characterized in that: The acute angle is less than 30 degrees, preferably less than 20 degrees, more preferably less than 10 degrees, and most preferably less than 5 degrees.

17. The cleaning method according to any one of claims 12 to 16, characterized in that: The location of the detected contaminant is stored.

18. The cleaning method according to any one of claims 12 to 17, characterized in that: The relatively movable cleaner moves along the surface of the mold surface to the location of the detected contaminant.

19. The cleaning method according to any one of claims 12 to 18, characterized in that: The relatively movable cleaner removes detected contaminants by suction, blowing, brushing and / or mechanical engagement.

20. The cleaning method according to any one of claims 12 to 19, characterized in that: When carrying out the method, a cleaning device according to any one of claims 1 to 11 is used.

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