The present invention relates to a cleaning unit for a mould for encapsulating electronic components, to a moulding system for encapsulating electronic components mounted on a carrier, and to a method for encapsulating electronic components mounted on a carrier using such a moulding system.

Electronic components are used on a huge scale and can for instance be formed by diodes (for example, light emitting diodes or LEDs), transistors, integrated circuits (IC/chips), chip-based sensors for detecting force, pressure, fingerprint, light and images, and chip-based actuators (MEMS; microelectromechanical 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 can be formed by, but not limited to, a wafer, a lead frame, or a (printed circuit) board.

When incorporating carrier based electronic components in electronic equipment it is often required to at least partially shield (encapsulate) the electronic component for which reason a housing may be moulded around the electronic component. The encapsulating material used for moulding electronic is usually formed by a (thermocuring) polymer, such as an epoxy resin, optionally provided with a filler material or a silicone-based encapsulating material. While the electronic component may be fully embedded in such moulded housing (encapsulation) it is also possible that for the functionality of the electronic component the encapsulated components may require the electronic component to be left at least partly free of the encapsulation to allow access to the electronic component e.g. for detection purposes and/or to cool the electronic component during use. The encapsulated electronic components undergo a continuous reduction of scale and the requirements set for the precision of the package of these electronic components are becoming stricter (up to micron level (pm) in respect of form).

During the encapsulating process an encapsulation (package) is arranged around the electronic components, wherein the electronic components are enveloped at least partially by the encapsulating material. For the encapsulating use is usually made of a mould or press provided with at least two mould parts, in at least one of which at least one, but normally a plurality of mould cavities is recessed. The carrier with electronic components is placed between the mould parts, after which the mould parts are moved towards each other until they take on a closed position in which the mould cavity or cavities enclose the electronic components for encapsulating. The mould cavity or cavities are then filled with the encapsulating material, which is usually done by means of transfer moulding, for which purpose the encapsulating material may first be brought into liquid state by heating. Alternatively, the encapsulating material can also be arranged all around the electronic components by means of compression moulding. In that case the encapsulating material is introduced into the mould cavity before the mould parts are closed. After the encapsulating material is at least partially cured (chemically), the press is opened and the carrier with encapsulated electronic components is removed from the mould. Following this, the encapsulated electronic components can for instance be separated from each other in a further process.

Before the start of a new production cycle it is important that the mould parts, especially the mould part or parts comprising the at least one mould cavity, are cleaned from pollution like residual encapsulating material particles, since these may disrupt the controlled encapsulation of the electronic components of the new production cycle. According to the prior art the mould parts are in the opened and unloaded state between two subsequent production cycles cleaned for this purpose with a cleaner that may include a brush and that sucks away the pollutions like residual encapsulating material particles.

Problems of the prior art electronic component moulding processes of the types as clarified above is that cleaning a mould part from pollution like residual encapsulating material particles with a suction cleaner is not always as effective as required. Dependent on the type of mould cavity (normally of the plurality of mould cavities) in a mould part, like for instance the depth and the shape of the cavity/cavities, more or less residual encapsulating material particles or other pollutions may stay behind in or on the mould part. Such particles or other pollutions are likely disturbing the proper moulding of electronic components in a subsequent moulding cycle. Hence, the goal of the present invention is to overcome these disadvantages and provide an improved cleaning unit for a mould for encapsulating electronic components, an improved moulding system and an improved method for encapsulating electronic components, enabling a better mould part cleaning leading to an enhanced quality of the resulting encapsulated electronic components.

To solve these problems the present invention provides a cleaning unit for a mould for encapsulating electronic components, comprising: a back and forth reciprocate moveable carriage; an elongated extraction space connecting to the carriage allocated perpendicular to the direction of reciprocating moveability of the carriage; elongated skirts protruding from the carriage and allocated parallel to the elongated extraction space on the longitudinal opposite sides of the elongated extraction space, wherein the elongated skirts extend in a direction from the carriage towards a mould surface to be cleaned; and at least one suction opening connected to the elongated extraction space; wherein the elongated skirt on at least one of the longitudinal sides of the elongated extraction space has at least two parallel protruding raised edges between which raised parallel protruding edges a shielded space is located that is closed on the top side, and wherein the at least two parallel protruding raised edges of an elongated skirt on a longitudinal side of the elongated extraction space are connected to each other on the transverse sides with raised transverse edges. In this respect the top side is to be understood as the side of the shielded space that is facing away from the mould part to be cleaned. Extending in a direction from the carriage towards a mould surface to be cleaned is to be understood as a direction of extension of the elongated skirts that may typically be perpendicular to an upper surface of the mould surface to be cleaned, i.e. an elongated skirt and the upper surface of the mould enclose an angle of about 90 degrees. However, this enclosed angle may also be larger or smaller than 90 degrees. The direction is defined when the cleaning unit is positioned on or slightly above the mould surface, during operation of the cleaning unit. From the elongated extraction space gas is extracted via the suction opening. With the extraction of the gas also particles that are detached from the mould part and to be cleaned other contaminations are extracted, thus cleaning mould part with the at least one mould cavity. As this will result in a lower pressure in the elongated extraction space gas (environmental gas that is normally ambient air) will be replenished through the openings between the parallel protruding raised edges and the mould part being cleaned as there is no (substantial) other or further opening to the elongated extraction space via which gas could be supplied. The gas is thus fed towards the elongated extraction space via the (slot-shaped) openings between the two protruding edges of the elongated skirt towards the mould part to be cleaned. The replenishing gas is guided thereby along the mould part to be cleaned with a passive regulated flow path. With this flow path the supplied gas is initially flowing through a first opening between a first parallel protruding raised edge faced away from the elongated extraction space and after passage of this first opening the gas flow at least partially moves away from the mould part being cleaned into the (higher and closed) space between the raised parallel protruding edges. The raised edges may alternatively also be referred to as “flanges”. This at least partially upward flow path in the space between the raised parallel protruding edges intensifies the cleaning properties of the gas flow. Subsequent the gas flow will be directed towards the mould part to be cleaned at the location where the second raised parallel protruding edges borders the space between the raised edges. And after passage of the second (slot-shaped) opening between the second protruding edges (facing towards the elongated extraction space) of the elongated skirt and the mould part to be cleaned the gas flow will be moved away from the mould part to be cleaned again in the longitudinal extraction space. Due to the “wave-shaped” flow pattern of the gas that is forced by the present invention the cleaning capabilities of the gas flow are substantially enhanced and thus results in a better cleaning of the mould part (and more specially of the mould cavity/cavities in that mould part) than provided with the prior art cleaning units. A further advantage is that the enhanced cleaning capabilities of the cleaning unit according to the present invention may enable to limit the cleaning time and thus to safe time for a production cycle; this may enhance the production capacity of the mould for encapsulating electronic components.

To enhance the effect of the cleaning properties of the cleaning unit according to the present invention the elongated skirts on both longitudinal sides of the elongated extraction space have at least two parallel protruding raised edges. As such, the flow paths on both the longitudinal sides of the elongated extraction space provide the improved cleaning effect.

For guiding the back and forth reciprocate moveable carriage a guide rail may be provided as well as a drive for moving the carriage (along the guide). With an elongated element an element here in the context is to be understood an element (or space) that is lengthened; that has a length that is larger than its width. As for the suction opening (or plural suction openings) in the elongated extraction space it is preferred that it (or they) are so distributed that a more or less even flow results over the width of the cleaning unit is realized. Typically the height of the openings between the parallel protruding raised edges and the mould part being cleaned lie preferably between 0,5 and 5 mm.

To further enhance the cleaning properties of the cleaning unit according to the present invention in the elongated extraction space at least one brush may be allocated that is protruding from the carriage. With such a brush also a physical contact (impact) on particles/pollutions that are attached to the mould may be made so to enhance the effect of particles/pollutions coming off the mould part to be cleaned. Such a brush is preferably elongated and allocated parallel to the elongated extraction space as so the complete surface to be cleaned may be covered by the brush. However as an alternative the brush could also be an assembly of several smaller brushes. In a further alternative the brush (or brushes may be moveable (e.g. intermittently or rotational as for instance in an electric toothbrush) relative to the carriage. Also the cleaning unit may include a brush cleaner and or the means to provide a dedicated (gas)flow that sucks away pollutions/particles that are collected in or on the brush and/or use may be made of a gas flow through (hairs of) the brush to minimize the pollution of the brush.

In yet another favorable embodiment the at least two parallel protruding raised edges of an elongated skirt on a longitudinal side of the elongated extraction space may be connected to each other on the transverse sides with raised transverse edges. Such additional raised transverse edges will prevent the influx of gas from the short sides of an elongated skirt to the shielded space between the raised parallel protruding edges. This will this result in an enhance gas flow (higher speed) at the locations where the cleaning effect is sought for. The same applies, mutatis mutandis, for providing elongated skirt on the short sides of the longitudinal extraction space.

To further influence the flow pattern of the gas in the shielded space between the at least two parallel protruding raised edges the closed top side of that space may be lower at a side facing away from the elongated extraction space than at a side facing towards the elongated extraction space. With such a design the wave- formed flow pattern of the gas may be enlarged thus positively stimulating the cleaning effect of the cleaning unit.

The parallel protruding raised edges of an elongated skirt on one longitudinal side of the elongated extraction space may have substantially identical heights. As an alternative or additionally also substantial identical heights of at least one of the skirts on both the opposite sides of the elongated extraction space are optional. Thus creating a balanced gas flow between several protruding raised edges.

At least a part of the protruding raised edges may be made from a solid material like for instance a metal and/or hard plastic. However it is also possible that at least a part of the protruding raised edges is made from a flexible material, like for instance a (silicone) rubber or flexible plastic. Raised edges from a flexible material enable the cleaning unit to pass smoothly pins or other elements protruding from the mould part to be cleaned.

The elongated skirts surrounding the elongated extraction space and the suction opening, as well as an optional bush, may be assembled on one or more frame part(s), which frame part(s) is/are perpendicular displaceable onto the carriage. With such an embodiment the carriage may be displaced relative to the mould parts problem-free and without the chance of contact (towards and away from the mould part to be cleaned) while the functional parts can be kept at a greater distance from the mould parts. Only when the cleaning starts the frame part(s) may be moved towards the mould part to be cleaned. Such movement of the frame part(s) may be in a direction perpendicular to the reciprocating moveability of the carriage and perpendicular to the longitudinal extraction space. A further advantage of assembling the optional brush on one or more of such a moveable frame parts is that wear of the brush may be compensated by amendment of the trajectory of the frame part(s).

For the extraction of the gas the cleaning unit preferably also comprises a suction device connected to the suction opening. As the cleaning unit is moveable the coupling of the suction device with the rest of the cleaning unit is a flexible coupling. To position the cleaning unit relative to the mould part to be cleaned and to prevent the cleaning unit to come to close to the mould part to be cleaned (e.g. to avoid the protruding edges to damage the mould part) and to guarantee an optimal suction between the elongated skirts and the mould the cleaning unit may comprises at least one guide for supporting the cleaning unit against the mould part to be cleaned; this results in the cleaning unit to have a relative controlled position. Such a guide may for instance be formed by one more contact rollers.

The present invention also provides a moulding system for encapsulating electronic components mounted on a carrier, comprising: at least one mould with at least two mould parts which are displaceable relative to each other, at least one of the mould parts with a mould cavity recessed in a contact side, which mould parts are configured to engage with the mould cavity around the electronic components to be encapsulated; and a cleaning unit according to the present invention moveable from at least one position in between the mould parts of the at least one mould when the mould parts of the mould are spaced apart and a position remote from the mould parts when the mould parts are in contact. The advantages of the cleaning unit are already clarified above and are here incorporated in relation to the moulding system according to the present invention. The cleaning unit may interact with a single mould but it is also possible that a single cleaning unit services two or more moulds; the cleaning unit is in such a situation movable relative to the moulds. The mould, or the plural moulds are normally assembled to fix the mutual orientations. Also such an assembly of one or more moulds and a cleaning unit is often shielded with a joint enclosure to shield the assembly and to promote safety.

The present invention also provides a method for encapsulating electronic components mounted on a carrier using a moulding system according to the present invention, comprising the processing steps of: A) positioning a carrier carrying one or more electronic components between two mould parts such that the electronic components face a mould cavity; B) moving the mould parts towards each other, such that the mould parts are clamping the carrier between the mould parts, the at least one mould cavity is enclosing the electronic components to be encapsulated; C) bringing a moulding material in the mould cavity; and D) moving the mould parts apart from each other, and removing the carrier with moulded electronic components from the mould parts; wherein after process step D) during a process step E) the cleaning unit is moved between the mould parts and the elongated extraction space is moved along the mould cavity containing mould part, whereby the elongated extraction space cleans the at least one mould cavity while simultaneously a gas with detached particles is extracted via the suction opening connected to the elongated extraction space, and whereby environmental gas is supplied to the suction opening through the openings between the parallel protruding raised edges and the mould part being cleaned. The advantages of the cleaning unit and the moulding system according to the present invention are already clarified above and are here incorporated in relation to the method for encapsulating electronic components according to the invention. The method is simply to automated and results in better cleaned mould parts after process step E) is completed. The method may be used to clean only one mould part, preferably the mould part containing the mould cavity/cavities, but is also possible to clean (two) opposite mould parts. In the latter situation both the mould parts may contain one or more mould cavities, but it is also possible that both the mould part contain one or more mould cavities. The process step E) may also be combined with the supply of encapsulating material (e.g. pellet-shaped) to a mould part.

The gas may be supplied with a gas flow via a first opening between a parallel protruding raised edge faced away from the elongated extraction space and after passage of the first opening the gas flow at least partially moves away from the mould part being cleaned into the space between the raised parallel protruding edges. Due to the gas flow “at least partially moving away” from the mould part being cleaned contaminants/loose particles will be carried away from the mould part, which is the demand during cleaning.

The gas when supplied, with a gas flow via a first opening between a first parallel protruding raised edge and the mould part being cleaned, and when supplied via a second opening of a second parallel protruding raised edge and the mould part being cleaned, before the passage of the first and second opening the gas flow at both locations has at least a component that is directed towards the mould part being cleaned. At the described locations the gas flow is at least partially directed towards the mould part to be cleaned, which supportive to loosening contaminants/particles from the mould part at two locations, again a feature that leads towards a more effective cleaning of the mould part.

In a further preferred embodiment of the method according to the present invention additionally the cleaning unit from at least one position may blow a gas flow against the mould part being cleaned during process step E). An additional gas flow directed towards the mould part to be cleaned may further be supportive for an improved cleaning.

The invention will be further elucidated on the basis of the non-limitative exemplary embodiments shown in the following figures. Corresponding elements are designated in the figures with corresponding reference numerals. Herein shows: figure 1 a schematic perspective view on a cleaning unit according to the present invention allocated between two mould parts of a moulding system for encapsulating electronic components; figure 2A a schematic perspective cross-cut view on a cleaning unit according to the present invention; figure 2B a cross-cut side view of the cleaning unit as shown in figure 2A; figure 3 a perspective bottom view on a further embodiment of cleaning unit according to the present invention; and figures 4A - 4C schematic perspective cross-cut views on alternative skirts to be incorporated in alternative embodiments of cleaning units according to the present invention.

Figure 1 shows a schematic perspective view on a cleaning unit 1 that is reciprocally (arrow Pi) moved along guides 2 between a position remote from the mould parts (to enable mould parts 3, 4 to closed on a carrier with electronic components) and a working route between the upper mould part 3 and the lower mould part 4 when the mould parts 3, 4 are spaced apart (as depicted). The cleaning unit 1 will be explained on the hand of subsequent figures in more detail but clearly visible in this figure 1 is also flexible coupling 5 on one side connected to a suction device (not depicted here) and on the other side (facing towards the cleaner) connected to an extraction tube 6 that leads to a suction opening in the cleaning unit 1 . Figure 2A shows a schematic perspective cross-cut view on a cleaning unit 10 acting on a mould part 11 including a plurality of moulding cavities 12, while figure 2B shows the same cleaning unit but in a cross-cut side view. The cleaning unit 10 comprises an elongated extraction space 13 wherein in this embodiment a brush

14 is allocated, however also an embodiment without a brush 14 is part of the present invention. The elongated extraction space 13 is connected with a carriage

15 and is closed on a top side 16 except for suction openings 17 through which air is extracted via flexible couplings (hoses) 18 leading towards a (not shown) suction device (pump) to realize an underpressure in the elongated extraction space 13. On both sides of the longitudinal sides of the elongated extraction space 13, and parallel to the elongated extraction space 13, elongated skirts 19 protrude from the carriage 15 thus further closing off the elongated extraction space 13. Both the elongated skirts 19 (in this embodiment) have two parallel protruding raised edges 20 , 21 between which raised parallel protruding edges 20, 21 a shielded space 22 is located that is closed on a top side 23. The underpressure in the elongated extraction space 13 will result in the supply of environmental gas through (slotshaped) openings 24, 25 between the parallel protruding raised edges 20, 21 and the mould part 11 being cleaned. Due to the (passive) influencing of the gas flow through the through (slot-shaped) openings 24, 25 and the shielded space 22 towards the suction openings 17 in the elongated extraction space 13 a waveshaped flow pattern will occur that is supportive in detaching particles 26 from the mould part 11 (and out of the moulding cavities 12)

Figure 3 shows a perspective bottom view on a cleaning unit 30 according to the present invention, wherein an elongated extraction space 31 is provided with three slot-shaped suction openings 32 (but different from the embodiment shown in the figures 2A and 2B here a brush lacks). Also here on both sides of the longitudinal sides of the elongated extraction space 31 are parallel elongated skirts 33 provided, both skirts 33 having two parallel protruding raised edges 34, 35 between which edges 34, 35 a shielded space 36 is located. On the on the transverse side of the shielded space 36 raised transverse edges 37 are provided to further close the shielded space 36 and to force as much of the outside air sucked in to pass the raised edges 34, 35. Also visible is that the elongated extraction space 31 on the transverse sides - with the same intention - is provided with transverse extraction space edges 38. On the transverse sides the cleaning unit 30 also comprises four guide rollers 39 for supporting the cleaning unit 30 against a mould part to be cleaned.

Figures 4A - 4B show schematic cross-cuts of alternative skirt embodiments 40, 41 , 42 for cleaning units according to the present invention. The skirt embodiment 40 shown in figure 4A has a first raised edge 43 on the side facing away from the elongated extraction space and a second raised edge 44 both bordering a shielded space 45. In this embodiment the shielded space 45 is lower on the side facing away from the elongated extraction space than on the side facing towards the elongated extraction space. The flow path of the air sucked in is demonstrated with the arrows P2, P3 and P4. Initially the outside air is sucked in towards a passage 46 beneath first raised edge 43 whereby the air flow is partially directed towards a mould part 47 to be cleaned (see arrow P2). After passing the passage 46 the air flow enters the shielded space 45 whereby the air flow will party move away (upward in the figure) from the mould part 47 to be cleaned (see arrow P ₃ ). And subsequently the air flow will be sucked in towards a passage 48 beneath second raised edge 44 whereby the air flow is again partially directed towards the mould part 47 to be cleaned (see arrow P4). The result is a “wave-shaped” flow pattern.

In the embodiment of the alternative skirt 41 shown in figure 4B there are three raised edges 49, 50, 51 protruding, adding an additional “wave” to the flow pattern of the air sucked in. And also in the embodiment 42 shown in figure 4C there are three raised edges 52, 53, 54 protruding, however here the intermediate shielded spaces 55, 56 have curved tops 57, 58 whereby the top at the ’’inflow side” is lower than on the “outflow side”.