Film-detaching frame for a sintering press

Abstract

A film-detaching frame (1) for a sintering press (100) for sintering objects (8) onto a substrate (9) comprises a framework (2) provided with connection means (4) 5 suitable for connecting the film-detaching frame (1) to the upper block (13) of the press, and a plurality of inner crosspieces (3) extending between opposite sides of the framework (2) so as to space apart the protective film (11) from parts (82) of the objects to be sintered, 10 and / or of the substrates, outside the pressing areas (8a).

Description

"FILM-DETACHING FRAME FOR A SINTERING PRESS"DESCRIPTION

[0001] The present invention relates to sintering presses for sintering electronic components onto a substrate , or casings containing the electronic components , onto dissipative elements , and in particular relates to an accessory tool , known by the term " f ilm-detaching frame" , suitable for facilitating the removal of the protective film used during the step of pressing the electronic components .

[0002] As is known, in certain electronic applications , electronic power components , such as IGBTs , thermistors , MOSFETs , for example , are fixed to a substrate by interposing a sintering paste . In order for each component to be sintered correctly, it is to be pressed by a sintering press under temperature conditions suitably controlled by heating apparatuses .

[0003] In other applications , the device to be subj ected to the sintering process can consist of a casing containing an electronic board formed by the electronic components and the substrate . Such a casing is sintered onto a dissipative element .

[0004] In other applications , the sintering press can be employed to perform lamination processes in which the obj ect to be subj ected to sintering does not compri se anyelectronic component .

[0005] For simplicity, in the continuation of the present description, any one of electronic components , casings thereof or obj ects intended for lamination wi ll be referred to as an obj ect to be sintered . Similarly, any element involved as the sintering obj ect playing the role of structural support will be referred to as a substrate , such as the substrate for electronic components or a massive dissipative element in the case of sintering electronic casings onto dissipative elements , for example .

[0006] A sintering press usually comprises a base forming a pressing plane on which one or more substrates are positioned . The press comprises an upper block equipped with a pressing unit provided with one or more pressing members for each substrate . At least one of the upper block and the base is movable upwards in height .

[0007] Such pressing members are operable , for example , by means of a pressuri zed fluid circuit to apply a predetermined and controllable pressure to the obj ects to be sintered .

[0008] In some embodiments , the press is equipped with a system for replacing a protective film, e . g . , a film made of PTFE , to be interposed between the pressing members of the pressing unit and the obj ects to be sinteredpositioned on the lower base . Such a system is fixed to the mounting structure of the sintering press and comprises a winder and an unwinder, both motori zed, for example , with brushless gearmotors .

[0009] In some embodiments , such an apparatus is capable o f moving parallel to the movement axis of the planes of the sintering press to allow a better replacement of the protective film and avoid tears to the latter or the occurrence of folds .

[0010] In some embodiments , the protective film i s supported by a peripheral frame , commonly re ferred to as a " film-detaching frame" . Such a film-detaching frame also prevents substrates from adhering to the protective film following the sintering cycle , thus limiting the movement of the substrates along the vertical axis of the sintering press when opening the latter .

[0011] In a working configuration, the substrates and / or obj ects to be sintered can have complex geometries and protruding parts along the vertical axis which could tear the protective film .

[0012] Another problem caused by such components having a three-dimensional geometry is the high risk of misalignment of the obj ects to be sintered with respect to the respective substrate following the contact between the protective film and protruding parts of the assemblyformed by substrate and obj ects to be sintered during the sintering press closing operation .

[0013] Therefore , the contact between protective film and such protruding parts is to be avoided to improve the success of the process .

[0014] An attempt to find a solution to such a problem includes using multiple j uxtaposed strips of protective film arranged so as to avoid the protruding elements . However, this solution involves apparent increased complexity in managing the tensioning and alignment of each of these strips of protective film during the process .

[0015] Moreover, with this technical solution it is not possible to perform a complete separation between the region of the pressing members and that of the components to be sintered, thus increasing the risk of contamination during the entire process time .

[0016] It is the obj ect of the present invention to propose a film-detaching frame and a sintering press capable of preventing contact between the protective film, even when it is made in a single piece and not in strips , and protruding parts of the substrate and / or obj ects to be sintered so as to avoid the fi lm from being torn and reduce the risk of misalignment between obj ects to be sintered and the related substrates during the sinteringpress closing steps .

[0017] Such an obj ect is achieved by a fi lm-detaching frame according to claim 1 and a sintering press according to claim 5 . The dependent claims describe preferred embodiments of the invention .

[0018] The features and advantages of the film-detaching frame and the sintering press according to the invention will be however apparent from the following description of preferred embodiments thereof , given by way of a nonlimiting indication, with reference to the accompanying drawings , in which :

[0019] - figure 1 is an elevation view of an example of a sintering press ;

[0020] - figure 2 is a top perspective view of the filmdetaching frame of the sintering press according to the invention, with the support of the pressing unit shown in phantom;

[0021] - figure 3 is an axial section of the sintering press mold, in the inactive press configuration ;

[0022] - figure 4 is a s imilar view to the preceding one , but with the press in the closing configuration; and

[0023] - Figure 5 is an enlarged view of a detail of the press at a pressing member, j ust before the impact with an obj ect to be sintered .

[0024] In said drawings , a sintering press for sinteringobjects 8 onto a substrate 9 is indicated as a whole by reference numeral 100.

[0025] The objects 8 to be sintered (e.g., electronic power devices such as IGBTs, diodes, thermistors, MOSFETs) are positioned on the substrate 9 with the interposition of a layer of sintering paste.

[0026] In some embodiments, the objects 8 to be sintered are to be processed with a predetermined surface pressure, e.g., 30 MPa, at a predetermined temperature, e.g., 260°C, for a predetermined time, e.g., between 180 and 300 seconds.

[0027] The sintering press 100 comprises a mounting structure 50 which extends vertically and supports a base 10 at the bottom and an upper block 13 at the top provided with a pressing unit 14.

[0028] Base 10 forms a pressing plane 102 which supports one or more substrates 9.

[0029] The mounting structure 50 is provided with longitudinal guides 90 along which at least one of the upper unit 13 and the base 10 translates vertically with respect to the other, for example by means of a hydraulic or electric actuator 80, between an open or inactive press position and a closed or active press position.

[0030] The base 10 and the upper unit 13, with the longitudinal guides 90 thereof, form the mold of thesintering press 100.

[0031] The pressing unit 14 is provided, for each substrate 9, with one or more pressing members 7 operable to apply a predetermined pressure to a pressing area of the objects 8 to be sintered. For example, the pressing area is the upper flat side 8a of the body, or casing, of the objects 8 to be sintered.

[0032] In an embodiment shown in figure 1, the at least one substrate 9 is positioned on a support block 60 placed on base 10 and provided with heating means for the substrate 9.

[0033] Press 100 comprises a protective film 11, for example made of PTFE, to be interposed between the pressing members 7 and the objects 8 to be sintered during the sintering.

[0034] In an embodiment, the protective film 11 is made in a single piece, i.e., it forms a continuous surface to be interposed between the pressing members 7 and the objects 8 to be sintered.

[0035] In an embodiment, the mounting structure also supports a winder 190 and an unwinder 192, both motorized, for example with brushless gearmotors, for the replacement of the protective film 11.

[0036] The protective film 11 is supported by a filmdetaching frame 1.

[0037] In an embodiment , the film-detaching frame 1 comprises a framework 2 and a plurality of inner crosspieces 3 .

[0038] Framework 2 is provided with connection means suitable for connecting the film-detaching frame 1 to the upper block 13 . Framework 2 thus forms a structural , i . e . , load-bearing, peripheral element of the filmdetaching frame 1 .

[0039] In an embodiment , the connection means comprise a plurality of rods 4 suitable for being constrained with possibility of sl iding in respective guide seats obtained in the upper block 13 of press 100 .

[0040] These rods 4 are positioned, for example , close to the peripheral vertexes 22 of framework 2 .

[0041] In some embodiments , the film-detaching frame 1 is elastically connected to the upper block 13 so as to be biased to remain in and return to the disengaged inactive lowered position by the pressing members 7 ( shown in Figure 3 , for example ) when the press is in the open configuration . For example , springs acting on the rods 4 are housed in the guide seats of the rods 4 .

[0042] In other embodiments , the film-detaching frame 1 tends to remain and return to the inactive lowered position by gravity .

[0043] The inner crosspieces 3 extend between oppositesides of framework 2 so as to space apart the protective film 11 from parts 82 of the obj ects 8 to be sintered and / or of the substrates 9 outside the pressing areas 8a .

[0044] For example , framework 2 is rectangular in shape and the inner crosspieces 3 are parallel to one another and to two opposite sides of framework 2 .

[0045] In an embodiment, one or more of the inner crosspieces 3 is shaped so as to form, on the side facing the obj ects 8 to be sintered, hous ing cavities 32 suitable for receiving parts 82 of the obj ects 8 to be sintered, and / or of the substrate 9 , extending in height past the pressing area 8a .

[0046] Therefore , in an embodiment , one or more of the inner crosspieces 3 has a thickness , or height , such as to allow the housing cavity 32 to be obtained in the inner crosspiece 3 .

[0047] In other embodiments , one or more of the inner crosspieces 3 is planar in shape , i . e . , it has no housing cavities 32 , and it acts as spacer for the protective film from sensitive parts of the obj ects 8 to be sintered and / or of the substrates 9 .

[0048] In an embodiment , the film-detaching frame 1 is also provided with spacers 5 extending from the side of frame 1 facing the base 10 .

[0049] The geometry of the spacers 5 can depend on that ofthe obj ects 8 to be sintered and / or substrates 9 involved in the process .

[0050] In some embodiments , the lower end of the spacers 5 comes into contact with the pressing plane 102 during the sintering press closing step, corresponding, for example , to the step of moving the base 10 in the direction of the pressing unit 14 .

[0051] The spacers 5 thus allow avoiding the film-detaching frame 1 from coming into contact with the substrates 9 and / or the obj ects 8 to be sintered following the closing of the press .

[0052] In other embodiments , spacers 5 and / or certain inner crosspieces 3 are configured to come into contact with suitable areas of the substrate 9 . Indeed, in some cases , for example in the presence of particularly lightweight substrates 9 , the substrate 9 could remain stuck to the protective film 11 when opening the mold and therefore be raised from base 10 . In this case , spacers 5 and / or crosspieces 3 hold the substrate 9 abutting against the base 10 at the beginning of the mold opening step due to the weight force of the film-detaching frame 1 and / or to the action of the elastic elements acting on the rods 4 .

[0053] In an embodiment , at least one ( 3a ) of the inner crosspieces 3 can have a di f ferent section from those of the other inner crosspieces 3 to also act as a structuralsupport of the whole film-detaching frame .

[0054] In an embodiment , the housing cavities 32 are counter-shaped with respect to the geometry of the protruding parts 82 of the obj ects 8 to be sintered and / or of the substrates 9 .

[0055] Figure 3 diagrammatically shows a mold of a sintering press 100 for electronic components 8 to be sintered, in an open configuration . Base 10 is spaced apart from the pressing unit 14 . Note the pressing members 7 and, between these and the electronic components 8 to be sintered, the protective film 11 in an inactive planar configuration . The protective film 11 is supported by the film-detaching frame 1 , the framework 2 of which extends , in a plan view, outside the plurality of pressing members 7 and related obj ects 8 to be sintered .

[0056] In an embodiment in which the pressing members 7 - and thus the obj ects 8 to be sintered - are arranged in a matrix configuration, the inner crosspieces 3 extend between the rows of pressing members 7 .

[0057] In an embodiment shown in figure 5 , the pressing members 7 can have beveled or rounded edges 7 ' in the region of contact with the protective film 11 in order to avoid the laceration thereof , facilitate the sliding thereof and avoid the film from j amming during itsreplacement / movement .

[0058] During the process of closing the sintering press , the protective film 11 switches from the planar geometry to a curvilinear geometry dictated by the spatial constraint between the film-detaching frame 1 and the pressing members 7 , as visible in Figure 4 .

[0059] In particular, it should be noted how the protective film 11 passes on the upper side of the inner crosspieces 3 , which house , on the side facing downwards , the protruding parts 82 of the obj ects 8 to be sintered or of the substrates 9 .

[0060] The protective film 11 is thus in contact with the obj ects 8 to be sintered only in the pressing area 8a, while it is spaced apart from, and thus protected from tears by, the protruding parts outside the pressing area 8a .

[0061] Therefore , the film-detaching frame also allows facilitating the process of sintering obj ects when the latter and / or the respective substrates have complex geometric configurations .

[0062] Moreover, the proposed film-detaching frame allows using a single strip of protective film 11 , with the related benefits of protective isolation and simplicity of management .

[0063] Those skilled in the art may make changes andadaptations to the embodiments of the film-detaching frame according to the invention or may replace elements with others which are functionally equivalent in order to meet contingent needs without departing from the scope of the following claims . Each of the features described as belonging to a possible embodiment can be made irrespective of the other embodiments described .

Claims

CLAIMS1. A film-detaching frame (1) for a sintering press (100) for sintering objects (8) onto a substrate (9) , wherein the sintering press (100) comprises a base (10) forming a pressing plane (102) on which one or more substrates (9) are positionable, an upper block (13) equipped with a pressing unit (14) provided, for each substrate, with one or more pressing members (7) operable to apply a predetermined pressure on a pressing area (8a) of the objects (8) to be sintered, and a protective film (11) between the pressing members (7) and the objects (8) to be sintered, the film-detaching frame (1) comprising a framework (2) provided with connection means (4) suitable for connecting the film-detaching frame (1) to the upper block (13) and a plurality of inner crosspieces (3) extending between opposite sides of the framework (2) so as to space apart the protective film (11) from parts (82) of the objects to be sintered, and / or of the substrates, outside the pressing areas (8a) .

2. Film-detaching frame according to claim 1, wherein one or more of the inner crosspieces (3) is shaped so as to form, on the side facing the objects (8) to be sintered, housing cavities (32) suitable for receiving parts (82) of the objects to be sintered, and / or of the substrates, extending in height past the pressing area(8a) .

3. Film-detaching frame according to claim 1 or 2, comprising spacers (5) extending from the side of the frame facing the base and suitable for abutting against the pressing plane (102) and / or the at least one substrate ( 9 ) .

4. Film-detaching frame according to any one of the preceding claims, wherein said connection means comprise a plurality of rods (4) suitable for being slidably constrained in respective guide seats obtained in the upper block (13) of the press.

5. A sintering press (100) for sintering objects (8) onto a substrate (9) , comprising a base (10) forming a pressing plane (102) on which one or more substrates (9) are positionable, an upper block (13) equipped with a pressing unit (14) provided, for each substrate, with one or more pressing members (7) operable to apply a predetermined pressure on a pressing area (8a) of the objects to be sintered, a film support device (1) suitable for interposing a protective film (11) between the pressing members (7) and the objects (8) to be sintered, wherein said film support device comprises a film-detaching frame (1) according to any one of the preceding claims, supported by the upper block.

6. Sintering press according to claim 5, wherein thepressing members (7) have beveled or rounded edges (7 ’ ) in the region of contact with the protective film (11) .

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