CN106340472B

CN106340472B - Straight-through furnace and tube core bonding machine with same

Info

Publication number: CN106340472B
Application number: CN201610522176.2A
Authority: CN
Inventors: 丹尼尔·安德烈亚斯·谢勒; 吉多·祖特尔
Original assignee: Besi Switzerland AG
Current assignee: Besi Switzerland AG
Priority date: 2015-07-07
Filing date: 2016-06-28
Publication date: 2021-05-07
Anticipated expiration: 2036-06-28
Also published as: CH711296A1; ITUA20164590A1; JP2017022370A; MY192150A; CH711296B1; KR20170006265A; DE102016112070A1; CN106340472A; KR102505372B1; DE102016112070B4; MX2016008822A; JP6844960B2; SG10201604156RA

Abstract

The invention relates to a straight-through furnace and a tube core bonding machine with the same. The invention relates to a flow-through furnace comprising a furnace body (2) and a cover (6), which enclose a channel through which a substrate can be transported and to which a working gas can be supplied. The cover (6) comprises at least one process opening. The interfaces between the individual components of the continuous furnace, which are detachably connected to one another, are formed with mating surfaces (11, 12) which face one another. At least some of the interfaces comprise grooves (15), a vacuum being able to be supplied to the grooves (15) in operation. Air that enters the inevitable gap between the mating surfaces (11, 12) is drawn away by suction through the grooves (15) and does not reach the interior space of the furnace. The invention also relates to a die bonder with such a continuous furnace.

Description

Straight-through furnace and tube core bonding machine with same

Technical Field

The present invention relates to a pass-through furnace with a releasable cover enabling access to the interior of the furnace for maintenance work. Working gas is supplied to the interior of the furnace. The invention also relates to a mounting device known as a die bonder with such a continuous furnace, wherein the working gas is a protective gas. Examples of "die" are particularly semiconductor chips, but may also be capacitors, metal platelets, etc.

Background

In the mounting of semiconductor chips, mainly power type semiconductors, are usually connected to a substrate by means of solder in order to ensure, via the solder connection, an efficient dissipation of heat losses from the semiconductor chips that occur during operation. However, other "die" are also soldered to the substrate. Metal substrates, so-called lead frames, are mainly used as substrates.

The applicant sells a die bonder suitable for this process under the name DB2009 SSI. The die bonder includes a flow-through oven through which the substrates are transported one by one to a solder station where solder is applied and melted, transported to a distribution station where solder is distributed over the substrate locations and then transported to a bonding station where semiconductor chips are placed on the liquid solder by a pick and place system. It is also possible to apply solder to the respective substrate locations and distribute it over the substrate locations in a single process station. The flow-through furnace is formed as a channel or tunnel with the necessary process openings. A protective gas atmosphere is present in the channel to prevent undesired oxidation of the substrate. Hydrogen is usually added to the protective gas to effect reduction of the oxides already present. The lower the oxygen concentration in the internal space of the furnace, the more effectively the substrate is prevented from being oxidized.

The flow-through furnace is formed by a furnace body and a cover, which delimit a channel. The cover is detachably attached to the furnace body since the furnace needs to be opened for maintenance work. The cover is relatively heavy and therefore is usually only placed on the furnace, where it is pressed against the furnace by its own weight. The covering piece can also be screwed together with the furnace body by screws. The interfaces between the individual parts of the cover and also between the cover and the furnace are formed as mutually opposite surfaces, which are designated as mating surfaces within the scope of the present disclosure. The mating surfaces ideally touch each other over a large surface area and thereby ensure that the interior space of the sealing oven is sealed off from the surrounding environment at all interfaces. Since even in the best-effort production there is an unavoidable gap between the mating surfaces through which ambient air can enter the interior space of the furnace, the mating surfaces are in principle avoided to the highest degree, and many other measures are taken to prevent ambient air from entering the channel in which the protective gas flows.

In chinese patent application CN 104658928 a, which claims priority from swiss patent application CH 708881 a1, a flow-through furnace is described in which the front side wall of the channel is formed with an elongated slot enabling the substrate to be transported by a gripper. Despite the provision of the protective gas, the interior space of such a continuous-flow furnace is hardly exposed to significant overpressure conditions, since it is of the type belonging to a semi-open continuous-flow furnace.

There are also flow-through furnaces in which different working gases are used instead of the protective gas.

Disclosure of Invention

The invention relates to a continuous furnace of the aforementioned type and also to a die bonder with such a continuous furnace. In the die bonder, the cover member of the flow-through furnace includes, for example: a process opening for applying solder to the substrate transported through the furnace; a process opening for distributing solder over the substrate location; and at least one process opening for applying a semiconductor chip to the substrate. The cover comprises at least one top cover and optionally additionally at least one plate covering one of the process openings and optionally also further elements. The process openings for applying and distributing the solder are covered, for example, by a plate which is moved to and fro in operation, for reasons which are not explained in more detail here. The plates serve to seal the respective process openings against the ingress of oxygen to the highest possible extent. In order to prevent the intrusion of ambient air into the channel through gaps existing between the individual parts of the cover and the furnace body, the interfaces between the individual parts of the cover and between the parts of the cover and the furnace body are mainly formed as mutually opposed mating surfaces. The mating surface can be, but need not be, a flat surface.

The inventors' examination has shown that oxygen reaches the channel not only at the inlet, outlet and process opening and optionally through longitudinal slots in the front side wall, but also through very fine but unavoidable gaps between the mating surfaces. To avoid this, the invention proposes that all interfaces are provided with grooves, i.e. that grooves are formed in at least one of the mutually opposite mating surfaces, and that the grooves are connected to a vacuum source via one or several closed channels and/or conduits, so that in operation a negative pressure can be supplied to the grooves. The grooves essentially function as vacuum chambers and separate the interior space of the furnace at the respective interfaces with respect to the pressure from the surroundings. The presence of a negative pressure in the groove ensures on the one hand that gases such as oxygen which reach the gap between the mating surfaces from the surroundings by diffusion and/or due to pressure differences only reach the groove and are drawn off by suction at the groove and are discharged again to the surroundings due to the negative pressure present. The underpressure prevailing in the channel on the other hand also ensures that the working gas flows from the interior space of the furnace into the channel in the event of a pressure gradient between the interior space of the furnace and the channel, and is also drawn off there by suction and discharged to the surroundings. This loss of working gas is low and acceptable.

In the flow-through furnace according to the invention, the interfaces between the individual components of the flow-through furnace, which are detachably connected to one another, are formed with mutually opposing mating surfaces. At least some, and preferably all, of the interfaces include grooves that are subjected to a vacuum during operation. Air that inevitably enters the gap between the mating surfaces is drawn away by suction through the grooves and does not reach the interior space of the furnace.

The invention will be explained in more detail by reference to embodiments and the accompanying drawings. For clarity of illustration, the drawings are diagrammatic and not drawn to scale.

Drawings

FIG. 1 shows a top view of components of a flow-through furnace according to the invention;

FIG. 2 shows a cross-sectional view of two mutually adjoining roof caps of a continuous-flow furnace;

FIG. 3 shows the interface of a flow-through furnace;

FIG. 4 shows a process opening of a continuous-flow furnace covered by a plate, and

fig. 5 shows a pressure diagram.

Detailed Description

Fig. 1 schematically shows a top view of components of a flow-through furnace 1 according to the invention, which flow-through furnace 1 is designed in particular for use in a die bonder. The continuous type furnace 1 comprises: a furnace body 2, the furnace body 2 having a base 3 and two side walls 4, 5 integral or connected to each other in an airtight manner; and a cover 6. The furnace body 2 and the cover 6 form a channel through which the substrate can be transported in the direction indicated by the arrow 7. The channel forms an interior space of the furnace. The front side wall 5 can comprise a longitudinal slot so that the substrate can be transported through the channel by means of the clamping system.

The cover 6 comprises at least one top cover, but in this embodiment comprises several

top covers

8 and 9. Each of the

caps

8, 9 comprises one or several process openings 10. The first cover 8 is designed to be moved only rarely, i.e. in particular for maintenance work. The second lid 9 is formed as a quick-change part, so that individual process adjustments, for example process openings, can be made in a short period of time. The base 3 and/or the one or

several roof caps

8, 9 comprise a plurality of holes (not shown) which can be connected to a source of protective gas, so that protective gas can be supplied to the interior space of the furnace during operation.

The first roof 8 and the second roof 9 are releasably connected to the furnace body 2. In the first embodiment, the first roof 8 rests on the furnace body 2 only by its own weight and can be removed manually for maintenance work. In the second embodiment, the first roof 8 also rests on the furnace body 2 by its own weight, but can additionally be pressed pneumatically or hydraulically against the furnace body 2 and can also be lifted pneumatically or hydraulically from the furnace body 2, for example for maintenance work. The first top cover 8 and the second top cover 9 can be screwed together with the furnace body 2 by screws. The

caps

8, 9 rest on top of each other and/or overlap each other.

The process openings 10 are usually permanently open, the process openings 10 being provided for the purpose of enabling the semiconductor chips to be placed on a substrate transported through the channel. Other process openings 10, for example process openings through which solder wires can be inserted from the outside into the channel, so that the solder can melt on the substrate, can be covered by a fixed plate or a plate that can be moved during operation.

The interfaces between the

caps

8, 9 and the furnace body 2 and the interfaces between adjacent caps and the interfaces between the plates and the associated caps are formed as mating surfaces facing each other.

In a flow-through furnace, there is therefore an interface where there is an unavoidable gap through which oxygen can reach the interior space of the furnace:

a mating surface between the first head 8 and the furnace body 2;

a mating surface between the second head 9 and the furnace body 2;

-a mating surface between adjoining

caps

8, 9; and

-a mating surface between the lid with the process opening and the plate covering the process opening.

In order to exclude or at least reduce the intrusion of ambient air through said gap, all of said interfaces, but at least the most relevant parts thereof, are provided with grooves, and said grooves are connected to a vacuum source via respective channels and/or gas conduits, which ensure that a vacuum is present in the grooves in normal operation of the continuous-flow furnace. The grooves are respectively arranged in one of the mutually opposed mating surfaces of the respective interface. Such grooves form a vacuum chamber which is connected in gas communication to the surroundings, on the one hand, through the inevitable gaps between the mating surfaces, and on the other hand to the inner space of the furnace.

Some aspects of the invention are explained in more detail below.

In order to seal the interface between the two side walls 4 and 5 by means of vacuum, the mating surfaces 12 of the furnace body 2, which are formed on the end faces of the side walls 4 and 5, are each provided with a groove 13. The groove 13 advantageously ends at a distance from the inlet and outlet of the far channel to avoid ambient air entering through the inlet or outlet of the channel being sucked directly into the groove 13, the groove 13 being able to be subdivided into sections by the separating wall 14. In this case, each segment is connected to a vacuum source. Since the mating surfaces 11 and 12 rest on each other, the groove 13 can instead be arranged on the mating surface 11 of the top cover instead of on the mating surface 12 of the furnace body 2.

In order to seal the interface between mutually adjoining

caps

8, 9 by means of vacuum, a groove 15 is applied to one of the mutually opposite mating surfaces of the two

caps

8, 9. In the first embodiment, the side surfaces of the two mutually adjoining

caps

8, 9 rest on each other as precisely as possible, and a groove 15 is formed in one of the mutually adjoining side surfaces of the first cap 8 or the second cap 9. In the second embodiment, the second top cover 8 is formed with a projection 18 (fig. 2) overlapping with the second top cover 9.

The channel 15 either leads to the channel 13, as shown in fig. 1, or is alternatively connected to a vacuum source via a separate gas line.

Fig. 2 shows a cross-sectional view of a first cap 8 and a second cap 9 according to a second embodiment adjacent to each other and bordering each other. For the sake of clarity of illustration, the top cover 8 is shown offset to the left in an upwardly inclined manner, so that the gap in which the outside air on the one hand and the protective gas on the other hand reach the groove 15 is clearly visible. The projection 18 lies as flat as possible on the second cover 9. The groove 15 is formed in one of the mutually adjoining side surfaces of the adjacent caps 8, 9 (as shown) or in the underside of the projection 18 of the first cap 8 opposite the second cap 9. The arrow 16 indicates the inflow of outside air into the gap between the protrusion 18 and the top cover 9; the arrows 17 indicate the flow of protective gas from the interior space of the furnace into the gap which exists between the two adjoining side walls of the two

roof caps

8 and 9.

Fig. 3 shows a cross-sectional view of another possibility of sucking away gas entering the gap between the two

mating surfaces

11 and 12 by suction via the grooves. This is achieved by means of an element 19, said element 19 being attached to the outer side of the flow-through furnace above the gap such that it covers the gap, and said element 19 comprising a groove 20 on the side facing the gap, the groove 20 being connected to a vacuum source.

Fig. 4 shows a top view of the top cover 9 with the process opening 10, which process opening 10 is covered by a plate 21. The board 21 can be mounted in a fixed manner or it can be carried by a writing head (not shown). The write head is for example used to guide the solder wire over the substrate in any direction in order to write a solder track on the substrate or to distribute the deposited solder over the substrate by means of needles driven by ultrasound. The plate 21 is always placed on the top cover 9 and slides back and forth. The underside of the plate 21 and the upper side of the top cover 9 are formed as mating surfaces. The trench 22 completely surrounds the process opening 10 and is connected to a vacuum source via a channel 23. A channel 23 is formed, for example, on the underside of the top cover 9 in such a way that it opens into the groove 22.

Thus, in addition to the

caps

8, 9, the cover 6 comprises one or several elements 19 and one or several plates 21.

Since the protective gas is continuously supplied in the inner space of the furnace in the operation of the flow-through furnace, the pressure in the inner space of the furnace is equal to or higher than the atmospheric pressure, while the vacuum existing in the

grooves

13, 15, 20 and 22 is lower than the atmospheric pressure. The level of vacuum in the

respective channels

13, 15, 20 and 22 is selected in such a way that there is a slight gas flow from the interior space of the furnace to the

channels

13, 15, 20 and 22. In order to achieve and set the desired vacuum, a vacuum source 24 and a common or separate adjustable pressure-controlled valve 25 are used, to which vacuum source 24 and common or separate adjustable pressure-controlled valve 25

channels

13, 15, 20 and 22 are connected via gas conduits 26. Fig. 5 shows a pressure diagram for a continuous-flow

furnace comprising channels

13 and 15.

While embodiments and applications of this invention have been shown and described, it would be apparent to those skilled in the art having the benefit of this disclosure that many more modifications than mentioned above are possible without departing from the inventive concepts herein.

Claims

1. A flow-through furnace having a furnace body (2) and a cover (6), the furnace body (2) and the cover (6) enclosing a channel having an inlet and an outlet and through which a substrate can be conveyed and to which a working gas can be supplied, wherein

The cover (6) comprising at least one process opening (10),

the furnace body (2) and the cover (6) comprise one or more separate parts which are detachably connected to each other,

the interface between the separate parts is formed as a flat connection having mutually opposing mating surfaces (11, 12), the mutually opposing mating surfaces (11, 12) being in contact with each other, and

at least some of the interfaces comprise grooves (13, 15, 20, 22), to which grooves (13, 15, 20, 22) a vacuum can be supplied in operation.

2. A die bonder with a flow-through furnace according to claim 1.