JPS63288039A - Inspection of film carrier packaging - Google Patents

Abstract

PURPOSE:To prevent a defective connection due to the lack of a bump, which has been hitherto found out after a second thermocompression bonding, by a method wherein an inner lead is deformed for being subjected to the second thermocompression bonding by bringing an IC chip into contact with the bump and the lack of the bump fixed by a first thermocompression bonding is found out by a difference between the amounts of deformation of the inner lead and an inner lead which is properly subjected to the first thermocompression bonding. CONSTITUTION:An inner lead 21 is deformed by a first thermocompression bonding and thereafter, the inner lead can be deformed for being subjected to a second thermocompression bonding by bringing a bump 25 fixed thermally by pressure on the inner lead into contact with a pad of an IC chip 22. At this time, if the inner lead lacks the bump fixed by the first thermocompression bonding the, the amount of deformation of the inner lead differs compared to that of an inner lead, which is properly subjected to the first thermocompression bonding. As a difference between the amounts of deformation can be easily discriminated by according to unsharp images, difference in lightness and so on, which are displayed on an image recognition unit, the lack of the bump due to the first thermocompression bonding can be judged. Thereby, the bonding of a film carrier, wherein a bump lacks, with the IC chip can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an inspection method for detecting missing bumps during IC mounting on film carriers used in various electronic devices.

Conventional techniques There are two methods for mounting an IC on a film carrier: (1) a method using an IC with bumps; and (2) a method using an inner lead on which bumps are formed. In method (2), further, part of the (1)-1 inner lead itself is made to protrude by processing.

(2)-2 A protrusion formed separately from the inner lead is bonded to the inner lead by thermocompression.

It can be subdivided into two parts. The method (2) can be implemented in a wide range of product fields because it can be implemented without adding any special process to the IC.

Conventional method (2) is carried out as follows.

In FIG. 2a, bumps 1 are small protrusions formed by electrolytic gold plating on the upper surface of layer 3 of T i /P deposited on substrate 2 by vapor deposition.

In the figure, the inner leads 6 of the film carrier 4 are held in contact with the bumps 1 or separated from the bumps 1 by several micrometers, and the tool 6 is used to perform the first application in the direction perpendicular to the substrate 2. Perform pressure. At this time, by adjusting the temperature of the tool 6 and the force applied to the substrate 2 through the inner lead 6 and bump 1 to appropriate values, the bump 1 is transferred to the inner lead 5 as shown in FIG.

The inner lead 6 to which the bump 1 has been transferred is held in a state where the pad portion 8 formed on the IC chip 7 and the bump 1 are in contact with each other or separated from each other by several μm, as shown in FIG. Pressure is applied in a direction perpendicular to the chip 7. During this second pressurization, if the temperature of the tool 6 and the force applied to the IC chip T through the inner lead 5 and bump 1 are set to appropriate values, the pad 8 of the ICC foot and the inner lead 5
are connected through bump 1. That is, the IC chip 7 is mounted on the film carrier 4.

At this time, the bonding center of the inner lead of the film carrier, the pad center of the IC chip, and the center of the bump formed on the substrate are in an equal relationship with each other. That is, in FIG. 3a, the bonding center of the first inner lead 12a extending perpendicularly to the film carrier running direction of the film carrier 11 and the bonding center of the second inner lead 12b facing the film carrier running direction and The distance in the vertical direction is L! , the distance in the direction parallel to the film carrier running direction between the third inner lead 12C extending in the direction perpendicular to the two inner leads 12a and 12b and the fourth inner lead 12d facing the third inner lead 12C is L. A and four inner leads 12a.

Pads 14a, 14b of the IC chip 13 in the figure corresponding to the bonding centers of 12b, 12c, 12d
, 14c, 14d glue, , the distance corresponding to L is px,
Similarly, in the same figure C, the corresponding bump 1sa
, 15b, 1sc, 1sd L! , the lengths corresponding to La are Bx and Ba, then L=p =13...
・・・・・・・・・・・・・・・(1) x x
x L=p=13 ・・・・・・・・・・・・・・・
)) y y y It is designed so that the following formula holds.

The problem to be solved by the invention: An IC is attached to a film carrier by the method described in "Prior art".
When mounting a bump, if a part of the bump transferred to the inner lead is defective or missing, the defect cannot be discovered and the IC pad and bump are bonded, resulting in a good IC chip being replaced with a defective film. There was a risk that it would become a carrier implementation. This is due to the following reason.

That is, in d4C of FIG. 2, bump 1 and xC chip 7
The upper pads 8 must be joined at a distance of several micrometers or in a state in which they are in contact. However, whether bump 1 exists on inner lead 6 or not depends on whether bump 1 exists on substrate 2 or not.
The only way is to check if there is any left or not, or to directly look at the inner lead 6. However, the method of looking at the inner lead 6 from the bump 1 side requires a complicated device mechanism.
It is difficult to realize.

Means for Solving the Problems Technical means of the present invention for solving the above problems include a step of first thermocompression bonding the bumps formed on the substrate to the inner leads of the film carrier; In a film carrier mounting method that includes a step of thermocompression bonding a bump to a pad portion of an IC chip, and then a second thermocompression bonding of the bump to a pad portion of an IC chip, the inner lead is bonded by contact between the IC chip and the bump for the second thermocompression bonding. It is characterized in that missing bumps due to the first thermocompression bonding are detected based on the difference in the amount of deformation of the inner lead.

For production The effects of the technical means of the present invention are as follows.

In other words, since the inner lead is deformed by the first thermocompression bonding and then subjected to the second thermocompression bonding, the inner lead can be deformed by bringing the bumps thermocompression bonded to the inner lead into contact with the pads of the IC chip. .

At this time, if the inner lead is missing the bump formed by the first thermocompression bonding, the amount of deformation will be different from that of the inner lead to which the first thermocompression bonding has been correctly performed.

The difference in the amount of deformation can be easily determined by the blurring of the image, the difference in brightness, etc. in the image recognition device, so it is possible to determine whether the bump is missing due to the first thermocompression bonding.

This makes it possible to prevent a film carrier with missing bumps from being bonded to an IC chip, and as a result, a good IC chip will not be rendered unusable due to poor mounting due to missing bumps.

EXAMPLE A first example of the present invention will be described below based on the drawings.

FIG. 1 shows a case where the coordinates of the center 21a of the inner lead 21 and the pad 23 on the IC chip 22 are the same, and only the position of the bump 26 is different.

In FIG. 1, the effective length of the inner lead 21 (the length from the root of the inner lead 21 to the bonding center) is l, and the position of the bump 26 is moved along the inner lead 21 to the outer circumferential side of the bump by C from the conventional position. Suppose it is expanded.

At this time, the height from the bottom surface of the inner lead 21 to the top surface of the bump 26 is set as D, that is, the inner lead 2
When the inner lead 21 is floated and joined using the tool 26, the inner lead 21 undergoes a first deformation as shown in the figure. At this time, a bump 25 is placed on the bonding center 21a of the inner lead 21.
Adjust the above D so that it can be joined.

After bonding the bump 26 and the inner lead 21, when bonding the bump 26 and the pad portion 23 of the IC chip 22, the second cause transformation.

In this case, if the bump 26 is correctly present on the inner lead 21, the result will be as shown in figure d, but if the bump 26 is not present, the inner lead 21 will be in an inclined state as shown in figure e. , the height of the bonding center of the inner lead 21 is located at a lower position by the height of the bump 26 compared to other locations where the bump 26 is correctly located. Both of these matters can be easily identified by a visual recognition device by the blurring of the image, the difference in brightness, etc., and the lack of the bump 26 can be detected before bonding the bump 25 and the pad portion 23 on the IC chip 22. It becomes possible to understand.

In addition, in Figure 1, L=4.12m 1 = 1.00■ D = 0.50 cod The amount of bump movement is! -0.20m.

Next, a second embodiment of the present invention will be explained. The center 31a of the inner lead 31 in FIG. 4a and the I in FIG.
This is a diagram in which all the coordinates of the pad 33 on the C chip 32 and the bump 35 in FIG.

In this case, L=! 1. B-! A 5P relationship is established. In the first embodiment, the inner leads 21, 21 after bonding are on the same plane, as shown in FIG. 1C, but in this embodiment,
As shown in Figure C, each inner lead 31, 31 is bent downward and joined. In other words, I
This means that the pad surface 38 of the C chip 32 and the wiring surface 39 of the film carrier are joined at different heights by δ.

Such a state reduces contact between the inner lead 31 and the edge 40 of the IC chip 32, and has the effect of reducing defects.

In this example, P = = 4.12■ B: 4.28 mI, =
4.02 wm l = 1, 05 wmD
= 0.15 sm δ = 0.32m, it was possible to perform the bonding.

When the inner lead 31 is mounted with an angular change as in this embodiment, there is almost no difference in the slope of the inner lead 31 depending on whether or not there is a bump 35, so there is almost no difference in brightness in the visual recognition device, but the image Missing bumps can be detected as blur.

Effects of the Invention As described above, the present invention provides a film carrier mounting inspection method in which, in the step of second thermocompression bonding of bumps to pads of an IC chip, contact between the IC chip and the bumps for the second thermocompression bonding By deforming the inner lead and detecting missing bumps caused by the first thermocompression bonding based on the difference in the deformation of the inner lead, it is possible to prevent connection failures due to missing bumps that were conventionally discovered after the second thermocompression bonding. It becomes possible. If connection failures can be prevented, good IC chips will no longer be usable due to poor mounting, making it possible to reduce production costs.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing the first embodiment of the present invention, Fig. 2 is a cross-sectional view showing the conventional process, Fig. 3 is a plan view showing the length relationship of conventional IC chips, etc., and Fig. 4 is a cross-sectional view showing the first embodiment of the present invention. is a sectional view showing a second embodiment of the present invention. 1.25, 35...bump, 2, 24.34.
...Board, 5,21.31...Inner lead, 6°26.36...Tool, 7.22.
32...-, IC chip, 8, 23, 33...
··pad. Name of agent: Patent attorney Toshio Nakao and 1 other person 2t
-in79-de(b+ 4-buff' 5--(nnoly y C--tool 7-zc nap 71 8-to" button 311 1 (-11) 4ruhe 1 & zu 4-inner lead (51L ~If(-)%”nf

Claims (1)

[Claims] A step of first thermocompression bonding the bumps formed on the substrate to the inner leads of the film carrier, and a second step of thermocompression bonding the bumps to the pads of the IC chip after thermocompression bonding the bumps to the inner leads. In the film carrier mounting method, the inner lead is deformed by contact between the IC chip and the bump for the second thermocompression bonding, and missing bumps due to the first thermocompression bonding are detected based on the difference in the amount of deformation of the inner lead. A film carrier mounting inspection method.