MOULD, ENCAPSULATING DEVICE AND METHOD OF ENCAPSULATION

Abstract: The invention relates to a mould for encapsulating electronic components mounted on a carrier, comprising: at least two mould parts displaceable relative to each other, at least one of which is provided with a recess, and feed means for encapsulating material, wherein at least one of the mould parts is provided with a runner which connects on one side to a wall of a mould part co-defining a mould cavity and connects on the other side to a side of the mould part remote from the mould cavity. The invention also relates to an encapsulating device of which such a mould forms part, and to a method for encapsulating electronic components mounted on a carrier.

Description: Mould, encapsulating device and method of encapsulation The invention relates to a mould for encapsulating electronic components mounted on a carrier, comprising at least two mould parts displaceable relative to each other, at least one of which is provided with a recess. The invention also relates to an encapsulating device for this purpose, comprising: a mould as described above, drive means for positioning and causing the mould parts to move relative to each other and feed means for encapsulating material. Finally, the invention also relates to a method for encapsulating electronic components mounted on a carrier. Such a mould, encapsulating device and method form known art with which, using for instance epoxy resin, a package of encapsulating material can be applied round an electronic component arranged on a carrier. This technique is used particularly for encapsulating semiconductor products, such as for instance chips. There is a tendency in the market towards arranging packages of encapsulating material on a carrier which are increasingly larger in terms of surface area. During further processing these can be for instance sawn into separate parts. This technique is also known as "C.S.P.", which is derived from "chip size packaging". The existing moulds and methods have the drawback that when the mould parts are closed a part of the electronic components can come into contact with a mould part. This can for instance cause damage to the components and/or contact wires ("leads") can be deformed. This is the particular consequence of a carrier not being completely flat when it is placed in a mould. Particularly carriers on which larger packages of encapsulating material must be arranged so that a plurality of electronic components can be moulded simultaneously with one package have such a three-dimensional form. The reason for this is that these carriers are in general thermally treated at many points during placing of the electronic components. This results in stresses in the carrier which, when it is placed in a mould, can result in the carrier not being completely flat. As described above, this results in possible damage to the electronic components and or connecting wires. The present invention has for its object to provide an improved mould, encapsulating device and method for encapsulating electronic components mounted on a carrier, with which damage to electronic components and contact wires can be prevented. The invention provides for this purpose a mould of the type stated in the preamble, wherein at least one of the mould parts is provided with a runner which connects on one side to a wall of a mould part co-defining a mould cavity and connects on the other side to a side of the mould part remote from the mould cavity. The runner preferably takes a multiple fonn and at least one wall of the mould part co-defming the mould cavity is provided with a number of apertures onto which runners connect. With such a mould a carrier can be sucked against a mould part before closing of the mould, whereby the carrier lies more or less flat against the relevant mould part. Thus is prevented that, when the mould is closed, electronic components and/or contact wires come into contact with a counter-mould part because the carrier is not flat. Avoiding this contact means that damage to electronic components and/or contact wires is prevented. When the mould is provided with a larger number of apertures onto which runners connect, the carrier can be placed in flat position on a mould part with more precision. The increases the reliability of the mould. In a preferred embodiment a plurality of runners connecting onto the wall co-defming the mould cavity are in mutual communication and are connected to a single runner which connects onto a side of the mould part remote from the mould cavity. By extracting gases through a single runner it can thus be achieved that the carrier is adhered by suction at a plurality of positions. A mould with great reliability can thus be realized with a simple suction. The runner preferably debouches in a wall defining a mould cavity, which wall is screened from the feed opening for encapsulating material by the carrier when encapsulating material is fed to the mould. In order to prevent encapsulating material entering the runner, the runner and feed opening for encapsulating material must be placed relative to each other such that during the encapsulating they are mutually separated by a carrier. It is noted here that it is recommended that the wall defining a mould cavity is formed by the bottom of the lower mould part. The force of gravity thus co-acts with the suction through the runner, which makes it easier to position the carrier more or less flat. An additional advantage is that the carrier is easier to place on a bottom wall of the lower mould part than for instance in an upper mould part. In yet another preferred embodiment a plurality of runners debouch in a wall co- defming the mould cavity and the outer ends of the runners are arranged in the wall in patterns such that they are located precisely where the mould cavity is formed such that space is left clear for receiving encapsulating material. The electronic components arranged on the carrier will also be situated precisely at the position where the spaces are left clear for receiving encapsulating material. These components must anyway be encapsulated by the encapsulating material. In order to now position the carrier as accurately as possible in the mould precisely where these components are situated, it is important to have the runners also debouch at these positions. It will then be possible to exert a force on the carrier in the direction of the wall at the position where the runners debouch. In yet another preferred embodiment a mould part provided with a runner is also provided with at least one aligning edge for positioning a carrier relative to the mould part. Since it can be difficult to displace a carrier again relative to a mould part once the former has been adhered by suction by the runner, it is recommended to first place the carrier at the correct position and then to activate the suction action by means of the runner. Another option is to activate the suction action of the runner immediately on placing, and in this case it is recommended to place the carrier directly at the correct position in the mould part. The aligning edge is also useful here. The invention also comprises an encapsulating device of the type stated in the preamble which also comprises a fan connecting onto the side of the runner remote from the mould cavity. This fan is preferably adapted to extract gases from the runner. For suction of the carrier by means of the runner it is necessary for an underpressure to be applied in the runner. This is realized by means of the fan which extracts gases. A carrier can thus also remain sucked against a mould part when the mould is opened, whereby the carrier with encapsulating material can be "pulled loose" from an opposite mould part. This opposite mould part (for instance the top mould) can thus be embodied without ejector pins. In a further preferred embodiment the fan is adapted to blow gases into a runner. A force can be exerted on the carrier with such an encapsulating device such that the carrier is released from the mould part in which it is located. It is thus possible to embody the mould in simplified manner compared to the moulds applied in the prior art. These after all employ ejector pins for pressing a carrier out of the mould after applying of the encapsulating material. It will be apparent that a mould incorporating a number of ejector pins has an emphatically more complex structure than a mould in which these can be omitted or arranged in more limited number. An additional advantage of blowing gases into the runner is that in this manner the runner can be cleaned of possible contaminants. It is thus also recommended to apply at least limited overpressure in the runner during cleaning of the mould so that no contaminants can be brushed or otherwise carried into the runner. The invention also relates to a method for encapsulating electronic components mounted on a carrier, comprising the steps of: A) positioning at least one carrier relative to a mould part, B) applying an underpressure in the runner connecting onto a wall co-defming the mould cavity, whereby the carrier is sucked against the wall, C) closing the mould by moving the mould parts towards each other, D) feeding encapsulating material to the part of the mould cavity left clear by the carrier, and E) opening the mould halves and removing the carrier with encapsulating material arranged thereon. By means of this method the carrier can be placed in close-fitting connection against a wall of a mould part before the mould is closed. This results in the advantages as already described above. The invention also provides a method for encapsulating electronic components mounted on a carrier, wherein the above described step B) is omitted but wherein during step E) an overpressure is applied in at least one runner connecting onto a wall co-defining the mould cavity. The runner is thus employed to eject the carrier with encapsulating material ananged thereon, or at least to release it from a mould half. As a result, the mould can be given a simplified form. Finally, the invention includes a method which comprises the steps A) to E) as described above and wherein during step E) an overpressure is also applied in at least one runner connecting onto a wall co-defming the mould cavity. With this method the advantages of the two methods described separately above are combined. That is, the carrier can be arranged close-fittingly in a mould part and, after the encapsulating process, the carrier will be released from the relevant mould part by overpressure in the runner. The advantages of both methods are hereby also combined. The present invention will be further elucidated with reference to the non-limitative embodiment shown hereinbelow. The figure shows a view of a schematic three- dimensional representation of a mould according to the invention in partly exploded situation. The figure shows a mould 1 consisting of an upper mould part 2 and a lower mould part 3. Lower mould part 3 is provided with a central beam 4 in which recesses 5 are arranged for placing pellets of encapsulating material. Also situated in central beam 4 in each recess 5 are plungers (not shown) with which pressure can be applied to the encapsulating material. Support plates 6,7 are ananged on either side of central beam 4. Support plate 7 is shown in a detached position while support plate 6 is shown in an assembled position. Support plates 6,7 are provided with a large number of apertures 8 which are placed together in groups. These apertures 8 connect onto runners 9 which run through support plates 6,7 and which are only shown for a few of the apertures 8 by means of broken lines. These runners 9 connect onto tracks 10 ananged in a base block 11. Base blocks 11 are adapted to bear support plates 6,7. Each base block 11 is provided with an internal bore 12 which connects onto tracks 10. Base blocks 11 are each provided with an outlet 13 of the bores 12. By now connecting a fan (not shown) onto each outlet 13, air can be drawn in through bore 12, tracks 10, runners 9 and finally apertures 8. The suction of air through apertures 8 can be utilized to place carriers such as for instance lead frames or B.G.As in flat position on the support plates 6,7. It is also possible to release earners from support plates 6,7 by increasing the pressure close to the outlet 13. This increased pressure will be transmitted to the apertures 8, which at least simplifies release of the carriers. It is noted that the groups of apertures 8 are placed such that in terms of shape they conespond with the shape of the spaces 14 which are left clear in the contact side 15 of the upper mould part 2. These spaces 14 will be filled with encapsulating material, which implies that the carriers will contain electronic components precisely at that position where spaces 14 are situated. It is therefore important that the carrier is in flat position particularly at these positions. It is for this reason that the apertures 8 are ananged at precisely these positions. Although the invention is elucidated with reference to only a single embodiment, it will be apparent to all that the invention is in no way limited to the described and shown embodiment. On the contrary, many more variations are possible for the skilled person within the scope of the invention. It is thus possible for instance to anange apertures 8 also, or only, in the upper mould part 2, whereby release of a carrier provided with encapsulating material can be realized by applying an overpressure on apertures 8. In addition, there are numerous possible variations in respect of the number and positions of apertures 8.

Claims: Claims 1. Mould for encapsulating electronic components mounted on a carrier, comprising: - at least two mould parts displaceable relative to each other, at least one of which is provided with a recess, and - feed means for encapsulating material, wherein at least one of the mould parts is provided with a runner which connects on one side to a wall of a mould part co-defming a mould cavity and connects on the other side to a side of the mould part remote from the mould cavity. 2. Mould as claimed in claim 1, wherein the runner takes a multiple form and at least one wall of a mould part co-defining the mould cavity is provided with a number of apertures onto which runners connect. 3. Mould as claimed in claim 2, wherein a plurality of runners connecting onto the wall defining the mould cavity are in mutual communication and are connected to a single runner which connects onto a side of the mould part remote from the mould cavity. 4. Mould as claimed in any of the foregoing claims, wherein the runner debouches in a wall defining a mould cavity, which wall is screened from the feed opening for encapsulating material by a carrier when encapsulating material is fed to the mould. 5. Mould as claimed in any of the foregoing claims, wherein a plurality of runners debouch in a wall co-defining the mould cavity and the outer ends of the runners are ananged in the wall in patterns such that they are located precisely where the mould cavity is formed such that space is left clear for receiving encapsulating material. 6. Mould as claimed in any of the foregoing claims, wherein a mould part provided with a runner is also provided with at least one aligning edge for positioning a carrier relative to the mould part. 7. Encapsulating device for encapsulating electronic components mounted on a carrier, comprising: - a mould as claimed in any of the foregoing claims, - drive means for positioning and causing the mould parts to move relative to each other, - feed means for encapsulating material, and - a fan connecting onto the side of the runner remote from the mould cavity. 8. Encapsulating device as claimed in claim 7, wherein the fan is adapted to extract gases from the runner. 9. Encapsulating device as claimed in claim 7 or 8, wherein the fan is adapted to blow gases into the runner. 10. Method for encapsulating electronic components mounted on a carrier, comprising the steps of: A) positioning at least one carrier relative to a mould part, B) applying an underpressure in the runner connecting onto a wall co-defining the mould cavity, whereby the carrier is sucked against the wall, C) closing the mould by moving the mould parts towards each other, D) feeding encapsulating material to the part of the mould cavity left clear by the carrier, and E) opening the mould halves and removing the carrier with encapsulating material ananged thereon. 11. Method for encapsulating electronic components mounted on a carrier, comprising the steps of: A) positioning at least one carrier relative to a mould part, C) closing the mould by moving the mould parts towards each other, D) feeding encapsulating material to the part of the mould cavity left clear by the carrier, and E) opening the mould halves and removing the carrier with encapsulating material ananged thereon, wherein during step E) an overpressure is applied in at least one runner connecting onto a wall co-defining the mould cavity. 12. Method as claimed in claim 10, wherein during step E) an oveφressure is applied in at least one runner connecting onto a wall co-defining the mould cavity.

Inventors: CLAASSEN ANTONIUS BERNARDUS, TOMASSEN MARCEL GERARDUS ANTON, CLAASSEN, ANTONIUS, BERNARDUS, TOMASSEN, MARCEL, GERARDUS, ANTONIUS
Applicants: CLAASSEN ANTONIUS BERNARDUS, FICO BV, TOMASSEN MARCEL GERARDUS ANTON, CLAASSEN, ANTONIUS, BERNARDUS, FICO B.V., TOMASSEN, MARCEL, GERARDUS, ANTONIUS
Application year: 1999
Main classification: H01L21
IPC codes: H01L21