JP2680170B2 - Heating device for die bonding of semiconductor chips - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to die bonding using a conductive paste at a predetermined position on a lead frame in which a semiconductor chip in an electronic component is formed in a strip shape of an appropriate length. In this case, the present invention relates to a heating device for drying and curing the conductive paste after the semiconductor chip is bonded with the conductive paste.

[Conventional technology]

Conventionally, this type of heating device is disclosed in, for example, Japanese Patent Laid-Open No. 58-34933.
As described in Japanese Unexamined Patent Publication (Kokai), a lead frame to which a semiconductor chip is bonded with a conductive paste is continuously conveyed in the longitudinal direction of the lead frame at a constant speed, and a heating block is attached to the lead block. The lead frame is arranged so as to extend along the conveying direction, and the lead frame is continuously conveyed while being in contact with the heating block, so that the conductive paste is continuously dried and cured. Is configured.

In this case, if the heating temperature at the time of drying / curing the conductive paste is increased, the time required for drying / curing is shortened, but if the heating temperature is high, bubbles are generated in the conductive paste or When the paste becomes brittle, the adhesive strength of the conductive paste is reduced, and the rate of defective products increases.

Therefore, in the conventional heating device, the heating temperature in the heating block must be set to a low temperature so as not to cause a decrease in the adhesive strength due to the conductive paste. Since the length along the direction becomes long, the heating device becomes significantly large.

Moreover, the conventional heating device heats the lead frame by continuously contacting the lead frame, which is being conveyed in the longitudinal direction, with the heating block. The conductive paste applied to the lead frame is continuously conveyed while being in constant contact with the lead frame, and the conductive paste is generated by contact sliding between the lead frame and the heating block during drying and curing of the conductive paste. Since minute vibrations are continuously received without interruption, the adhesive strength of the conductive paste is significantly reduced, and the semiconductor chip mounting device is misaligned, resulting in the accuracy of the semiconductor chip mounting position. There was also a problem that it would decrease.

[Problems to be solved by the invention]

A technical problem of the present invention is that the above-mentioned problems of the conventional heating device, that is, the heating device becomes large, the adhesive strength of the conductive paste is reduced, and the accuracy of the mounting position of the semiconductor chip is reduced. To eliminate the problem.

[Means for solving the problem]

In order to achieve this technical problem, according to the present invention, between a pair of left and right endless chains, a plurality of lead frame support members extending in a direction perpendicular to the longitudinal direction of the endless chains are provided in the longitudinal direction of the endless chains. The both endless chains are mounted at appropriate intervals along the space, and an intermittent feeding mechanism for intermittently conveying the both endless chains at the intervals of the lead frame support member is provided, while one end of the both endless chains is provided. A lead frame formed by bonding a semiconductor chip to a top surface of the lead frame supporting member by using a conductive paste as an adhesive and the longitudinal direction of the lead frame is parallel to the longitudinal direction of the lead frame supporting member. In this state, the semiconductor chip mounting portion of the lead frame is fed so as to project from one side edge of the lead frame supporting member in the longitudinal direction. And a feed mechanism for feeding the lead frame on the upper surface of the lead frame supporting member in the longitudinal direction of the lead frame at the other end of the both endless chains, and A structure in which a plurality of vertically movable heating blocks are arranged so as to come into contact with the lower surface of the lead frame on the upper surface of the lead frame supporting member when the heating blocks are raised between the lead frame supporting members. I chose

[Functions and effects of the invention]

In this configuration, when the intermittent conveyance in each lead frame supporting member mounted between both endless chains is stopped, the upper surface of each lead frame supporting member is attached to the upper surface at one end of each endless chain. The lead frame formed by bonding the semiconductor chips with the conductive paste is sequentially fed by the feeding mechanism.

In this way, the lead frame support member into which the lead frame has been fed is intermittently conveyed toward the other end of both endless chains, and when the intermittent conveyance is stopped, the heating block Rises to contact the lower surface of the lead frame supported by the lead frame supporting member to heat the lead frame. By repeating this heating at a plurality of heating block locations, the conductive paste is removed. When the conductive paste is completely dried and hardened, the lead frame is moved at the other end portions of the two endless chains by the feeding mechanism in the longitudinal direction of the lead frame supporting member. Is sent from.

That is, according to the present invention, as in the conventional case, the lead frame is connected along the longitudinal direction of the lead frame and is conveyed, and the heating block is brought into contact with the lead frame to thereby form the conductive paste. Instead of drying and curing the lead frame, the lead frame is intermittently conveyed in the direction perpendicular to the longitudinal direction of the lead frame by the lead frame support member mounted between the two endless chains. When the transport is stopped, the conductive paste is dried and hardened by contacting the vertical heating block with the lower surface of the lead frame. However, it is possible to prevent the heating device from becoming large as in the conventional case, and thus it is possible to significantly reduce the size of the heating device.

Moreover, according to the present invention, as described above, the lead frame is intermittently conveyed in the direction perpendicular to the longitudinal direction of the lead frame by the lead frame support member mounted between the endless chains, and this intermittent When transporting is stopped, the lower surface of this lead frame is brought into contact with a vertically moving heating block to dry and cure the conductive paste, so that during the drying and curing of the conductive paste, Since the vibration applied to the lead frame can be significantly reduced as compared with the conventional case, it is possible to surely prevent the adhesive strength of the conductive paste from being lowered and the mounting position of the semiconductor chip from being displaced. It also has an effect.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In the figure, reference numerals 1 and 2 denote a pair of left and right machine frame frames, and reference numerals 3 and 4 denote a pair of left and right end chains, and both endless chains 3 and 4 are between the two machine frame frames 1 and 2. It is wound around four sprockets 5, 6, 7, 8 attached to the.

Reference numeral 9 indicates a lead frame supporting member extending in a direction perpendicular to the longitudinal direction of the both endless chains 3 and 4, and a plurality of lead frame supporting members 9 are provided between the endless chains 3 and 4. While mounting the endless chains 3 and 4 at appropriate intervals along the longitudinal direction, the bidirectional ends 3 and 4 are mounted at intervals of the lead frame support member 9 by an intermittent feeding mechanism such as a step motor (not shown). It is configured to be intermittently transported.

In this intermittent conveyance, the conveyance of the lead frame supporting member 9 is stopped for an appropriate time (for example, about 30 seconds), and then the lead frame supporting member 9 is conveyed by the interval.

Further, the rollers 10 and 11 provided at both ends of the lead frame support member 9 are slidably engaged with the guide rails 12 and 13 fixed to the inner side surfaces of the machine frame frames 1 and 2, respectively. By doing so, each lead frame support member 9
The guide rails 12 and 13 guide each other so that they are conveyed in a horizontal state.

The cross section of each lead frame supporting member 9 is formed in a substantially L shape, and the lead frame A is placed on the upper surface of the lead frame supporting member 9 such that the longitudinal direction of the lead frame A is parallel to the longitudinal direction of the lead frame supporting member 9. When mounted, the semiconductor chip in the lead frame A and the mounting portion A1
Is configured so as to project from one side edge in the longitudinal direction of the lead frame supporting member 9, while a pressing member 14 made of a metal plate is provided on each lead frame supporting member 9 so as to be vertically movable ( However, reference numeral 15 is a guide pin for the vertical movement of the pressing member 14), and the pressing member 14
Is urged downward by the spring 16 so that the lead frame A is pressed by the pressing member 14 against the upper surface of the lead frame support member 9, in other words, the lead frame A is pressed. , Lead frame support member 9
It is configured to be sandwiched between and by the pressing member 14.

Reference numeral 17 indicates a feeding mechanism arranged at one end of each of the endless chains 3 and 4, and the feeding mechanism 17 makes a semiconductor chip conductive to each semiconductor chip mounting portion A ₁ in advance in a die bonding process (not shown). A lead frame A formed by adhering with a paste is sent to the lead frame supporting member 9 as shown by an arrow B in FIG. 1. When the lead frame A is sent, both machine frame frames 1, The push-up member 18 disposed between the two is raised by the pneumatic cylinder 19, and the push-up member 18 holds the push-up member 14 in the lead frame support member 9 and its spring.
The lead frame A is pushed up against 16 and, in this state, the lead frame A is fed to the upper surface of the lead frame support member 9, and then the push-up member 18 is lowered to move the lead frame A to the lead frame support member. 9 and the pressing member 14 so that they are sandwiched.

Further, reference numeral 20 indicates a delivery mechanism arranged at the other end of the endless chains 3, 4, and the delivery mechanism 20 is
The lead frame A on the upper surface of the lead frame supporting member 9 is sent out from the lead frame supporting member 9 in the longitudinal direction of the lead frame supporting member 9 as shown by an arrow C in FIG. At the time of feeding, the push-up member 21 disposed between the machine frame frames 1 and 2 is raised by the pneumatic cylinder 22, and the push-up member 21 holds the lead frame support member 9 in place.
14 is pushed up against its spring 16 so that the lead frame A is released from the pinched state.

Reference numeral 23 is a first heating block whose heating temperature is set to, for example, 140 ° C., reference numeral 24 is a second heating block whose heating temperature is set to, for example, 170 ° C. which is higher than that of the first heating block 23, and reference numeral Reference numeral 25 denotes a third heating block whose heating temperature is set to, for example, 190 ° C. higher than that of the second heating block 24, and these heating blocks 23, 24, 25
Is attached to an elevating table 28 guided vertically by guide members 26, 27, and the elevating table 28 is pneumatic cylinder when the intermittent transfer of each lead frame supporting member 9 is stopped. By ascending at 29, the upper surfaces of the heating blocks 23, 24, 25 are brought into contact with the lower surface of the lead frame A.

In this configuration, when the intermittent conveyance in each lead frame support member 9 mounted between both endless chains 3 and 4 is stopped, the upper surface of each lead frame support member 9 has two endless chains 3 and 4, respectively. At one end of the lead frame 4, a lead frame A formed by bonding a semiconductor chip to the upper surface with a conductive paste is sequentially fed by a feeding mechanism 17.

In this way, the lead frame support member A into which the lead frame A has been fed is intermittently conveyed toward the other end of both endless chains 3 and 4, and the intermittent conveyance is stopped. Each heating block 23,24,25
Rises to come into contact with the lower surface of the lead frame A supported by the lead frame support member 9 to heat the lead frame A. This heating is performed at a plurality of heating blocks 23, 24, 25. By repeating this, the conductive paste is dried and cured. When the conductive paste is completely dried and cured, the lead frame A is moved by the delivery mechanism 20 at the other end of both endless chains 3, 4. The lead frame A is sent out in the longitudinal direction of the lead frame A from the lead frame supporting member 9 to the next wire bonding step.

A cover 30 is provided above the machine frame frames 1 and 2 so as to cover the lead frame support members 9, and an inert gas such as nitrogen gas is introduced into the cover 30.
When the lead frame A is heated by the heating blocks 23, 24 and 25 and then discharged through the outlet 32, the lead frame A is prevented from being discolored due to oxidation. A partition plate 33 for partitioning the inside into an upper part and a lower part is provided inside 30, and an inert gas such as nitrogen gas is introduced into the upper chamber 30a from the inlet 31 and then discharged from the outlet in the lower chamber 30b. Of.

With this structure, the temperature of the low temperature inert gas flowing from the inlet 31 rises when flowing through the upper chamber 30a, so that the temperature of the low temperature inert gas flowing into the inlet 31 enters the lead frame A. It is possible to reliably avoid direct contact with each other, that is, cooling of the lead frame A being heated by the inert gas having a low temperature flowing from the inlet 31.

Further, in this heating device, when the lead frame A after the conductive paste is dried and cured is supplied to the wire bonding step which is the next step, a trouble may occur in the wire bonding step. Accordingly, the operation of the heating device must be stopped accordingly, and when the operation of the heating device is stopped, the lead frame A is heated for a long time, which causes deterioration of the derivable paste and the lead frame. This causes a problem such as discoloration of A.

In order to avoid this inconvenience, it is necessary to temporarily store a plurality of lead frames A sequentially fed from the heating device at a portion between the feeding portion of the lead frame A in the heating device and the wire bonding process. The buffer device 34 described above may be provided.

The buffer device 34 includes a machine frame 35 and a bracket plate 37 mounted on the machine frame 35 so as to be vertically movable via a pair of left and right guide members 36. The bracket plate 37 is provided on the front surface of the bracket plate 37. While a plurality of receiving shelves 38 for the lead frame A are provided, a screw shaft 40 rotated by a pulse motor (step motor) 39 is rotatably supported between the machine frame 35 and the bracket plate 37. The bracket plate is formed in the thread groove 41 formed on the outer peripheral surface of the screw shaft 40.
By slidingly engaging a slider 44 projecting from the back surface of 37, the bracket plate 37 is moved up and down by forward and reverse rotations of the pulse motor 29.

That is, the lead frame A sent from the lead frame support member 9 by the sending mechanism 20 is one receiving rack on the front surface of the bracket plate 37 of the buffer device 34.
It is placed on the upper surface of 38 (in this case, the bracket plate 37
Is made of a non-magnetic material such as aluminum or synthetic resin, and is embedded in the permanent magnet 43 therein, and the permanent magnet 43 holds the lead frame A on the upper surface of the shelf 38). .

Then, the bracket plate 37 moves up or down by the forward and reverse rotations of the pulse motor 39, and the lead frame A sent next from the heating device is placed on the next receiving rack 38 repeatedly. Since the plurality of lead frames A can be stored in the buffer device 34, even if a trouble occurs in the wire bonding process, it is possible to avoid stopping the operation of the heating device each time.

[Brief description of the drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is an overall plan view,
2 is an enlarged sectional view taken along the line II-II of FIG. 1, FIG. 3 is a sectional view taken along the line III-III of FIG. 1, and FIG. 4 is an enlarged sectional view taken along the line IV-IV of FIG. Is a sectional view taken along line V-V in FIG. 4, and FIG.
IV-IV sectional view of the figure, FIG. 7 is a plan view of FIG. 6, FIG. 8 is an enlarged sectional view of FIG. 1 taken along the line VIII-VIII, and FIG. 9 is an enlarged view of essential parts of FIG. FIG. 10 is a sectional view taken along line XX of FIG. The semiconductor chip mounting portion of the A ...... lead frame, A ₁ ...... leadframe, 1,2 ...... machine frame frame, 3,4 ......
Endless chain, 5,6,7,8 sprocket, 9 ...... lead frame supporting member, 10,11 ...... roller, 12,13 ...... guide rail, 14 ...... pressing member, 17 ...... lead frame feeding Mechanism, 18 ... Push-up member, 20 ... Lead frame feeding mechanism, 21 ... Push-up member, 30 ... Cover, 31 ...
Inert gas inlet, 32 ... Inert gas outlet, 34 ... Buffer device, 35 ... Machine frame, 37 ... Bracket plate, 38
...... Lead frame holder, 39 ...... Pulse motor, 40
…… Screw shaft, 41 …… Screw groove, 42 …… Slider, 43 …… Permanent magnet.

Claims (1)

(57) [Claims] 1. A plurality of lead frame support members extending between a pair of left and right endless chains extending in a direction perpendicular to the longitudinal direction of the endless chains are mounted at appropriate intervals along the longitudinal direction of the endless chains. , Both the endless chains are provided with an intermittent feeding mechanism adapted to intermittently convey the both endless chains at intervals of the lead frame supporting member, while at the one end of the both endless chains, a semiconductor chip is provided with a conductive paste. The lead frame formed by adhering the lead frames to the upper surface of each of the lead frame supporting members in a state where the longitudinal direction of the lead frame is parallel to the longitudinal direction of the lead frame supporting member and the semiconductor chip in the lead frame. A lead-in mechanism is provided in which the attachment portion projects from one side edge of the lead frame support member in the longitudinal direction, and a feed mechanism is provided. The other end portions of the endless chain, the lead frame in the upper surface of the lead frame support member,
A lead-out mechanism adapted to feed the lead frame in the longitudinal direction is provided, and a plurality of vertically movable heating blocks are provided between the lead frame support members, and the lead frame is provided when the heating block rises. A heating device for die bonding of a semiconductor chip, wherein the heating device is arranged so as to come into contact with the lower surface of the lead frame on the upper surface of the supporting member.