JP2910398B2 - Solder bump formation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a solder bump, and more particularly to a method for forming a solder bump for mounting a semiconductor device.

[0002]

2. Description of the Related Art Conventionally, as a method of forming solder bumps required for flip chip mounting of semiconductor elements, there is a technique of supplying solder by plating or vapor deposition.

FIGS. 4A to 4D are process sectional views showing a method of forming a solder bump on a semiconductor element by a plating method. First, Cr is formed by sputtering or the like on the entire surface of the LSI 9 on which the wiring layer 15 and the protective layer 10 are formed on the silicon substrate 11.
And a diffusion preventing layer 16 of Ni or the like. [FIG. 4A] Next, a resist layer 20 is applied to the entire surface, exposed and developed to remove the resist layer 20 at the electrode portion. Thereafter, a thick solder layer 19 is formed on the electrode portion by plating. [FIG. 4 (b)] After plating, the resist layer 20 is removed, and the diffusion preventing layer 16 and the adhesive layer 17 other than the electrode portion are removed by etching using the solder layer 19 as a mask, thereby completing the solder supply step. [FIG. 4 (c)] When solder is supplied by vapor deposition, the adhesive layer and the diffusion preventing layer are formed by forming a resist layer and removing portions other than the electrode portion in advance, and in the vapor deposition process instead of plating, only the electrode portion has holes. Then, a soldered layer is formed only on the electrode part. Usually, the solder layer 19 on the LSI is heated and melted and formed into the spherical solder bump 12.
[FIG. 4 (d)] FIGS. 5 (a) and 5 (b) show a metal sheet punched out with a predetermined diameter and thickness using a punch and a die proposed in Japanese Patent Application No. 02-178854, and a direct electrode is formed using a punch. The method of crimping a metal piece is shown above. Punch 1 at predetermined position on substrate 7
And die 3 are positioned. The metal sheet 2 is punched with the punch 1, and the punched metal piece 18 is pressed onto the substrate 7 at the tip of the punch 1. This method can also be applied to solder supply.

[0004]

The conventional solder bump forming method as described above has the following problems. That is, the plating method and the vapor deposition method require complicated processes,
In order to attach a solder layer having a large thickness, the processing time becomes longer, and therefore, the bump formation cost becomes higher,
There were problems such as the need for large capital investment.
Furthermore, in these methods, it is difficult to obtain a highly reliable solder due to a composition deviation easily, it is a factor that lowers the yield in semiconductor devices, etc., and it is necessary to process in a wafer state, so that flexibility is required. There is also a problem. Further, there is another problem that it is difficult to obtain a uniform film by the plating method, so that a bump having a uniform shape cannot be obtained. Punch the solder sheet,
The method of punching with a die and directly pressing the solder pieces using a punch for punching does not have the disadvantages described above.However, since the punched pieces of solder are supplied to the electrodes by pressing, the surface layer has a mechanical strength. In the case of a weak semiconductor device, it is necessary to control the altitude of the pressing force of the punch. In addition, in order to obtain an adhesive force between the solder and the electrode, it is necessary to apply Au or the like, which easily alloys with the solder, to the surface of the electrode and to heat the substrate, which has a problem in reliability such as diffusion of Au into the solder. .

[0005]

According to the solder bump forming method of the present invention, a solder piece formed by pressing is placed on a temporary placement plate in an arrangement in which the arrangement of electrodes on a substrate is inverted, and then the solder piece is formed. This is a method in which a solder piece and an electrode, which are arranged by overlapping a substrate, are brought into contact with each other, and the solder piece is transferred from the temporary arrangement plate to an electrode of the substrate. Here, after the solder pieces are transferred from the temporary arrangement plate to the electrodes of the substrate, the transferred solder pieces may be melted into a spherical shape and adhered to the electrodes by heating the substrate. Another method of forming a solder bump of the present invention is to arrange a solder piece formed by press working on a temporary placement board in an arrangement in which the arrangement of electrodes on a board is inverted, and then place the temporary placement board and the board on top of each other. In this method, the solder pieces are brought into contact with the electrodes, and then the solder pieces are transferred from the temporary placement plate to the electrodes of the substrate by heating the substrate and simultaneously melted to form a spherical shape and adhere to the electrodes. Solder pieces are placed on the temporary placement board by pressing the solder pieces formed by punching the sheet-like solder material directly onto the temporary placement board using the punch used for the punching process, or by dropping on the temporary placement board Do.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIGS. 1A to 1E show a first embodiment of the present invention.
FIG. First, a heated foam release sheet 13 in which an adhesive layer foams due to heating used in dicing or the like and the adhesive strength is reduced is stuck on the glass plate 5 to form a temporary arrangement plate 21. [FIG. 1 (a)] Next, a tin-lead solder sheet 14 having a thickness of 150 μm is punched out with a punch 1 and a die 3 having a diameter of 200 μm, and a solder piece 4 is directly pressed by a punch 1 onto a heat-foaming peeling sheet 13, thereby temporarily. The solder pieces 4 were arranged on the arrangement plate 21. The arrangement of the solder pieces 4 needs to be an inverted arrangement of the electrodes of the LSI 9. [Figure 1
(B)] Next, on the LSI 9 on which the flux 5 is applied by a spin coater of about 7 μm, the temporary placement plate 21 is placed on the LSI electrode 8 while the positions of the electrodes 8 of the LSI 9 and the solder pieces 4 are aligned. The temporary placement plate 21 was heated to 100.degree. C. while pressing with low pressure. [FIG. 1C] Next, when the temporary placement plate 21 is pulled up, the solder pieces 4 are separated from the temporary placement plate 21 and transferred to the LSI electrodes 8. [FIG. 1 (d)] Thereafter, the LSI 9 was heated to 200 ° C. to melt the solder pieces 4 to form spherical solder bumps 12. [FIG. 1 (e)] The heat-foamed peeling sheet of the temporary placement plate 21 loses its tackiness by heating at 100 ° C., whereas the flux has tackiness.
Transfer to the SI electrode 8 becomes possible. When the solder piece 4 is directly placed on the electrode by using the punch 1 and the die 3, the electrode surface layer needs to be made of a metal such as Au which is easy to adhere to the solder, and the pressing force of the punch 1 is 40 g. However, in the case of the present invention, a surface layer of Ni, Cu or the like may be used, and the pressing force per electrode is about 3
Good transfer was also possible with g. Further, the flux 5 applied to the LSI can also function to remove the solder and the oxide layer of the electrode at the time of melting after the transfer. On the other hand, if it is too thin, the reducing action at the time of melting is insufficient, and the bump shape becomes poor. A suitable flux thickness was 4 to 50 percent of the solder material.

FIGS. 2A to 2C show a second embodiment of the present invention.
FIG. Temporary arrangement plate 2 as in the first embodiment
As No. 1, solder pieces 4 were arranged using a glass plate on which a heat-foamed release sheet was stretched. In this embodiment, the flux 7 is formed on the LSI 9 only by screen printing on the electrodes. [Figure 2
(A)] Next, the temporary arrangement plate 21 was positioned and mounted so that the position of the electrode 8 of the LSI 9 and the position of the solder piece 4 coincided with each other, and the temporary arrangement plate 21 was heated to 100 ° C. while applying low pressure. [Figure 2
(B)] Next, when the temporary placement plate 21 is pulled up, the solder pieces 4 are separated from the temporary placement plate 21 and transferred to the LSI electrodes 8. Thereafter, the LSI 9 was heated to 200 ° C. to melt the solder pieces 4 to form spherical solder bumps 12. [FIG. 2 (c)]
In this case, since the flux is formed only on the electrodes, defects due to the flow of the solder pieces at the time of melting are less likely to occur.

In the first and second embodiments, a heat-foamable release sheet is used as a sheet to be adhered to the surface of the glass plate 5, but a UV-curable sheet whose adhesiveness is reduced by irradiation with ultraviolet light may be used. In the case where a process for reducing the adhesiveness is performed after being superimposed on the substrate as in the embodiment, the provisionally arranged plate 21 is used.
The base material needs to be made of a material such as a glass plate 5 that transmits irradiation light. Further, in the first and second embodiments, the process of reducing the adhesiveness after overlapping with the substrate 9 was performed. However, the process may be performed immediately after the solder pieces 4 are arranged on the temporary arrangement plate 21 and then the substrate 9 may be overlapped. Good.

FIGS. 3A to 3D show a third embodiment of the present invention.
FIG. In this embodiment, the glass plate 5 coated with the flux 5 is used as the temporary arrangement plate 21.
[FIG. 3 (a)] A solder piece 4 is arranged using a punch 1 and a die 3. Next, the LSI 9 was heated to 100 ° C., and the temporary arrangement plate 21 was positioned and mounted on the LSI 9, and the LSI 9 and the temporary arrangement plate 21 were heated to weld the solder pieces 4 on the electrodes. [FIG. 3 (c)] Thereafter, the temporary placement plate 21 was pulled up while the solder was being melted, and the spherical solder bumps 12 were obtained. [FIG. 3 (d)] In the case of the present embodiment, the solder pieces are melted while the temporary placement plate 21 is positioned on the LSI 9, so that the lower surface of the glass plate 5 and the electrode 8 are heated so that the solder bumps 12 do not collapse during heating. It is desirable to keep the distance constant. In addition, the temporary arrangement plate 21 of the present embodiment
Alternatively, a flat plate made of a material compatible with solder having a finely uneven surface may be used. In this case, the solder pieces are temporarily fixed by unevenness on the surface, and when the solder is melted, the temporary placement plate 2
1 does not weld.

In the method of the present invention, since the solder piece is formed by press punching, the uniformity of the supplied amount is good, and the bump height after melting is 150 ± 2 μm. The solder bumps on the high-precision LSI electrodes thus obtained are large and suitable for flip-chip mounting of LSIs having electrodes arranged at high density. As described above, by using the method of the present invention, solder bumps can be formed on LSI electrodes arranged at high density with higher precision, lower cost and less mechanical impact than conventional ones.
The solder used in the present invention can be applied not only to tin-lead solder but also to gold-tin solder, indium-based solder, tin-based solder, gold-silicon solder, gold-germanium solder and the like. Further, the present invention is applied not only to the LSI but also to the formation of bumps on a wiring board which is vulnerable to mechanical shock.

[0012]

As described above, the present invention is a method of transferring a solder piece formed by a press method to a temporary arrangement plate and then transferring the same, so that a solder bump having a uniform volume can be relatively easily formed on a substrate. There is an effect that it can be formed without applying a mechanical load. In addition, there is an advantage that a wet process or a vacuum process is not required, the process is simplified, and there is little restriction on a supplied solder material and an electrode structure, so that highly reliable bonding can be easily obtained.

[Brief description of the drawings]

FIGS. 1A to 1E are process cross-sectional views of a first embodiment of the present invention.

FIGS. 2A to 2C are process cross-sectional views of a second embodiment of the present invention.

FIGS. 3A to 3D are process cross-sectional views of a third embodiment of the present invention.

FIGS. 4A to 4D are process cross-sectional views showing a conventional solder bump forming method by a plating method.

FIGS. 5A and 5B are process cross-sectional views showing a conventional solder supply method by a punching method using a punch and a die.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Punch 2 Metal sheet 3 Dice 4 Solder piece 5 Glass plate 6 Flux 7 Substrate 8 Electrode 9 LSI 10 Protective layer 11 Silicon substrate 12 Solder bump 13 Heated foam peeling sheet 14 Solder sheet 15 Wiring layer 16 Diffusion prevention layer 17 Adhesive layer 18 Metal Piece 19 Solder layer 20 Resist layer 21 Temporary placement board

Claims (11)

(57) [Claims] 1. A punch is formed by pressing a solder piece formed by press working.
After sequentially arranging the electrodes of the substrate from the tip in an inverted arrangement on the temporary arrangement plate via an adhesive layer , the temporary arrangement plate and the substrate are overlapped with each other, and the arranged solder pieces and the electrodes are arranged. Contact and place the placed solder pieces in front of the temporary placement plate
A method for forming a solder bump, wherein the method is separated from the adhesive layer and transferred to an electrode of the substrate. 2. The method according to claim 1, wherein after transferring the solder pieces from the temporary arrangement plate to the electrodes of the substrate, the substrate is heated to melt the transferred solder pieces into a spherical shape and adhere to the electrodes. Solder bump formation method. 3. A punch is formed by pressing a solder piece formed by press working.
After sequentially arranging the electrodes of the substrate from the tip on the flat temporary arrangement plate in an inverted arrangement, the solder pieces arranged on the temporary arrangement plate and the substrate are brought into contact with the electrodes, and then the substrate is contacted. A method for forming a solder bump, wherein a solder piece arranged by heating is transferred from a temporary arrangement plate to an electrode of a substrate, and simultaneously melted to form a spherical shape and adhere to the electrode. 4. A solder piece formed by punching a sheet-like solder material is pressed directly onto a temporary placement plate using a punch used for the punching process, or dropped on the temporary placement plate. 4. The method for forming a solder bump according to any one of items 3 to 3. 5. The method according to claim 1, wherein the surface layer of the temporary placement plate is made of a layer whose adhesiveness is reduced by heating, and has a step of performing a heat treatment simultaneously with or before the transfer to the substrate after the solder pieces are placed. 5. The method for forming a solder bump according to any one of claims 4 to 4. 6. The method according to claim 1, wherein the surface layer of the temporary placement plate is made of a layer whose adhesiveness is reduced by light irradiation, and has a step of irradiating with light before or simultaneously with transfer to the substrate after arranging the solder pieces. A method for forming a solder bump according to any one of claims 1 to 4. 7. The method for forming a solder bump according to claim 3 , wherein the surface of the temporary placement plate is in a fine uneven state . 8. The solder bump forming method according to claim 1, wherein the solder pieces are transferred to a substrate having a surface coated with a flux. 9. The method according to claim 8, wherein the application of the flux is performed only to the electrode portion to which the solder piece is transferred. 10. The solder piece material is any one of tin-based solder, tin-lead solder, gold-tin solder, indium-based solder, gold-silicon solder, and gold-germanium solder.
10. A method for forming a solder bump according to any one of claims 9 to 9. 11. The solder bump forming method according to claim 1, wherein the formed solder bump is applied to connection of a semiconductor element.