JPS6266641A - Die bonding method for semiconductor pellet - Google Patents

Abstract

PURPOSE:To save a using amount of preformed material without increasing reciprocating strokes at scrubbing time by preparing a plurality of preformed foil pieces to be inserted between a lead frame and a semiconductor pellet, and aligning them laterally at an interval. CONSTITUTION:When bonding a pellet 3 of width S and length L on an island 2 of width T and length X, two preformed foil pieces 4a are used, their width Wa=S/2-2A (where 2A is reciprocating stroke of scrubber) is satisfied, and the pieces are aligned at an interval 2A. The pieces 4a are elongated to be connected by scrubbing, and the pellet 3 is entirely fusion-bonded to the island 2. With this construction, expensive preformed foil pieces can be saved to reduce the bonding cost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] As shown in FIG. Alternatively, the present invention relates to a die bonding method using a preform foil piece made of fully bent foil such as solder foil.

[Conventional technology]

In this way, on the top surface of the island portion 2 having a width (T) and a length X) formed on the lead frame l, a
) When die-bonding the semiconductor pellet 3 using a preform foil piece, conventionally, the steps shown in FIGS. 7 and 8 were performed.
As shown in the figure, from a preform foil piece material tape formed to have a width (W) narrower than the width (S) of the semiconductor pellet 3 by 2A, a length L approximately equal to the length L) of the semiconductor pellet 3 is obtained. ) is cut out, this preform foil piece 4 is inserted between the semiconductor pellet 3 and the island part 2, and this preform foil piece 4 is cut out.
While heating and melting the semiconductor pellet 3 and pressing it against the island part 2 with pressure, move the semiconductor pellet 3 to the position indicated by the dashed-dotted line, which is a distance (A) to the right in the width direction from the position indicated by the solid line in FIG. and the distance from the position of the solid line in the width direction (
, A) The die bonding is performed by reciprocating the position indicated by the chain double-dashed line a number of times to the left.

This operation of reciprocating the semiconductor pellet 3 in the width direction while pressing it against the island portion 2 is called scrubbing, and this scrubbing is performed by reciprocating the semiconductor pellet 3 in the width direction to remove the molten state. This is to stretch the preform foil piece 4 to the full width of the semiconductor pellet 3 and weld the semiconductor pellet 3 to the island portion 2 of the lead frame 1 over its entire surface. Therefore, the width (W) of the preform foil piece 4 is the value obtained by subtracting the reciprocating stroke (2A) in scrubbing from the width (S) of the semiconductor pellet 3, that is, S −2
It is determined that A=W.

[Problem that the invention seeks to solve]

In this die bonding, reducing the amount of preform foil pieces 4 used as much as possible can contribute to cost reduction. For this reason, if the width (W) of the preform foil piece 4 is narrowed, the stroke 2A when reciprocating the semiconductor pellet 3 during the scrubbing must be increased.

However, increasing the reciprocating stroke in scrubbing in this way not only increases the time required for scrubbing, but also increases the
When die bonding the semiconductor pellet 3 to the
) so as not to exceed the dimension minus T.
-3>2A (stroke 2A is T
-3, the semiconductor pellet 3 will reciprocate beyond the width of the island portion 2, so that the preform foil piece 4 in the molten state will be exposed to both left and right end surfaces of the island portion 2.
There is a limit value to the increase in the reciprocating stroke in scrubbing and the reduction in the width (W) of the preform foil piece 4.

Further, in the conventional method, the width of the semiconductor pellet 3 (S
) changes, the width (W) of the preform foil piece 4 must also be changed accordingly, and this preform foil piece 4
Since it is necessary to prepare multiple types of preform foil strip material tapes with different width dimensions, inventory management of preform foil strip material tapes and replacement of preform foil strip tapes, etc. This required a great deal of effort.

Moreover, the width (W) of the preform foil piece 4 must be increased as the width (S) of the semiconductor pellet 3 becomes larger; however, when the width (W) of the preform foil piece 4 is increased, A cutting error occurs when cutting the wide preform foil piece 4 from the preform foil piece material tape.

The present invention can reduce the amount of preform foil pieces used without increasing the reciprocating stroke in scrubbing, and uses one type of preform foil piece material tape with the same width dimension to handle semiconductor pellets with different width dimensions. The purpose is to be able to respond to

[Means to solve the problem]

Therefore, in the present invention, a piece of preform foil having a width narrower than the width of the semiconductor pellet is placed on the upper surface of a predetermined portion of a lead frame, and the semiconductor pellet placed on the preform piece is heated and melted. In the die bonding method, the preform foil piece is made into a plurality of narrow width preform foil pieces, and each of the preform foil pieces is The pieces are arranged with spaces between them.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 2 and 3. A semiconductor pellet 3 having a width (S) and a length L) is placed on the top surface of an island portion 2 having a width (T) and a length X). , when performing die bonding using preform foil pieces, two preform foil pieces 4 are used as preform foil pieces.
a, 4a, and the width of both preform foil pieces 4a (
Wa) is set to a narrow width of half the width (S) of the semiconductor pellet 3 minus the reciprocating stroke (2A) in scrubbing, that is, Wa = S / 2 - 2A,
Both preform foil pieces 4a are placed side by side on the upper surface of the island portion 2 so as to leave an interval of 2A between the two preform foil pieces 4a, and the semiconductor pellet 3 is placed thereon.

Then, while both preform foil pieces 4a are heated and melted, the semiconductor pellet 3 is pressed against the island portion 2 by a distance (A) in the width direction from the position of the solid line in FIG. So-called scrubbing is performed by reciprocating between the position indicated by the dashed-dotted line, which is spaced to the right, and the position indicated by the dashed-dotted line, which is spaced from the solid line by a distance (A) to the left in the width direction.

By scrubbing with this reciprocating stroke of 2A, each of both preform foil pieces 4a is stretched in the left-right direction, but the width of both preform foil pieces 4a (
Wa) is set to Wa=S/2-2A as described above, and
By setting the interval between both preform foil pieces 4a to 2A, both preform foil pieces 4a are stretched to both left and right ends 3a, 3b of the semiconductor pellet 3, and at the same time, between the two preform foil pieces 4a, Since both preform foil pieces 4a are stretched so as to be connected to each other, the entire surface of the semiconductor pellet 3 can be welded to the island portion 2.

In this case, the total area of both preform foil pieces 4a is W a
X L X 2, and the area of the preform foil piece is
Since the area of the preform foil pieces in the conventional case can be reduced by 2AXL, that is, the area between the preform foil pieces 4a, the amount of preform foil pieces used can be reduced without increasing the reciprocating stroke in scrubbing. It is possible to save.

Then, when the width (Wa) of both preform foil pieces 4a is set to Wa-3/2-2A as described above, and the interval between both preform foil pieces 4a is set to 2A, the width of the preform foil pieces is Although the amount used is the minimum value, in reality, there should be some margin in the width (W a ) of both preform foil pieces 4a, and if the width (S) of the semiconductor pellet 3 becomes narrower. In this case, by narrowing the distance between the two preform foil pieces 4a, the preform foil pieces 4 having the same width (Wa) can be made to correspond to the semiconductor pellet 3 having a narrow width.

In addition, the width of both preform foil pieces 4a is set to @(Wa) when the amount of preform foil pieces used is the minimum as shown in FIG.
By increasing the width (Wa') as shown in Figure 4, the reciprocating stroke in scrubbing can be reduced from (2A) to (2A') by the increased width, reducing the time required for scrubbing. can be shortened, and also,
As shown in FIG. 5, the width of both preform foil pieces 4a is determined by the width (W a
), and the stroke of the reciprocating motion in the scrub is set to (2A) as above, the semiconductor pellet whose width becomes wider from (S) to width (S'). 3, and the width is (
It can also be adapted to the semiconductor pellet 3 which is narrower than S).

Note that the number of preform foil pieces 4a to be used is not limited to two as in the above embodiment, but if it is three as shown in FIG. 6, the amount of preform foil pieces 4a used can be reduced compared to the conventional case. By increasing the number of preform foil pieces 4a, the amount of preform foil pieces used can be further reduced.

〔Effect of the invention〕

As described above, according to the present invention, a plurality of preform foil pieces are inserted between the lead frame and the semiconductor pellet, and these are arranged at intervals in the width direction, thereby making it easier to scrub during die bonding. Since the amount of expensive preform material used can be reduced by the area of the spacing between the preform foil pieces, the cost required for die bonding can be reduced without increasing the reciprocating stroke.

Moreover, by setting the material tape for preform foil strips, which is the material of the preform foil strips, to a specific width dimension, it is possible to adapt to changes in the width of semiconductor pellets by simply changing the interval or number of strips arranged in a row. Therefore, it is only necessary to prepare one type of material tape for preform foil pieces, and the labor required for inventory management and replacement work of material tape for preform foil pieces can be reduced. .

Furthermore, by setting the width of each preform foil piece, it is possible to shorten the reciprocating stroke in scrubbing, and since each preform foil piece has a narrow width, the preform foil material tape It also has the advantage of reducing the occurrence of cutting errors when cutting preform foil pieces.

[Brief explanation of drawings]

FIG. 1 is a plan view of the lead frame, FIG. 2 is an enlarged plan view showing the method of the first embodiment of the present invention, and FIG. 3 is a plan view of the lead frame.
Fig. 4 is an enlarged plan view showing the method of the second embodiment of the present invention; Fig. 5 is an enlarged plan view showing the method of the third embodiment of the invention; 6 is an enlarged plan view showing a method according to a fourth embodiment of the present invention, FIG. 7 is an enlarged plan view showing a conventional method, and FIG. 1...Lead frame, 2...Island part, 3...
... Semiconductor pellet, 4a... Preform foil piece.

Claims (1)

[Claims] (1) A preform foil piece with a width narrower than the width of the semiconductor pellet is placed on the upper surface of a predetermined location in the lead frame, and the semiconductor pellet placed on top of the preform foil piece is heated and melted. In the die bonding method, the preform foil pieces are made into a plurality of narrow width preform foil pieces, and each preform foil piece is A die bonding method for semiconductor pellets, characterized in that semiconductor pellets are arranged with spaces between them.