JPH01228698A - Forming method for preform brazing filler metal - Google Patents

Abstract

PURPOSE:To manufacture the brazing filler metal of good quality without being restricted by shape and dimension with a work receiving no mechanical or thermal deformation by taking the brazing filler metal of low m.p. as the thin sheet in the specified thickness and cutting it in the specified shape while the surface of sheet is irradiated by a laser beam. CONSTITUTION:The energy of the laser beam, by which the thin sheet making the brazing filler metal of a low m.p. in the thickness of >=5mum is irradiated directly acts the particle composing the thin sheet blank, sublimating it. When the laser beam is moved along the specified locus, cutting can be executed in the specified shape without giving heat and mechanical effects except its irradiation position without causing burr and roll over irrespective of the shape and thickness.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for forming a brazing material used for fixing silicon wafer etc. to a base when manufacturing semiconductor elements such as ICs. In particular, the present invention relates to a method of forming a preform brazing material that can stably produce a high-quality material that is low in manufacturing cost and that allows smooth brazing in high-mix, low-volume production.

[Prior Art] Various types of brazing filler metals are used for the purposes mentioned above. Since these are usually attached along the periphery of the bottom of the object to be fixed, a thin plate material is formed in advance into a perforated plate shape that matches the shape of the outer edge of the bottom of the object to be fixed. The chip is sandwiched between the chip and the base and heated to melt the brazing material and fix it. Conventionally, such a preform brazing material has been manufactured by punching and molding using a metal mold.

[Problems to be Solved by the Invention] However, the above conventional techniques have the following problems.

(1) With the recent trend toward miniaturization of elements and resource saving, brazing filler metals are also becoming extremely thin and narrow.

For example, Au-20vt$Sn solder is often used as an Au solder for Ga-As bonding, but its dimensions are 10 μm(t)Xo, 1mm(
w) xO, approximately 1 mm (f2). The same material was also used as a sealing solder for a ceramic chip package, 30 μm (t) x 2. O++vφ(
A ring-shaped material with an outer diameter) Xl and 7a+φ (inner diameter) is used. It is extremely difficult to punch and form such a fine and extremely thin material using a mold. For example, in normal punching, the clearance between the punch and die is required to be several percent of the thickness of the punched plate.
When the plate thickness is from several μm to several tens of μm, it is practically difficult to manage this clearance, making it impossible to design the mold. In addition, if the tolerance control is insufficient, good processing conditions will not be ensured, and unnecessary force will be applied to the punched material, resulting in warpage, distortion, burrs, etc.
This also causes a reduction in mold life. If warpage or burrs occur, the brazing material will not fit perfectly when placed on the joint surface, and the brazing process will not proceed smoothly or the brazing process will be defective.

(2) On the other hand, in the case of brazing filler metals, the material itself is often not suitable for punching. For example, the Au
In the case of wax-based materials, there is generally little plastic elongation;
Since many of them exhibit brittleness, as mentioned above, Wtw is as thin as several tens of μm and has a crosspiece width of about 0°1 to 0.3 m.
When punching out an i-formed sheet, the mechanical impact easily destroys it. - On the other hand, as materials other than Au-based, Hv:IO such as Pb-5n-based and Pb-In-based
~30 soft brazing filler metals are commonly used.

In such materials, the material adheres to the mold, reducing processing accuracy, and also enters the gap between the bonder and the die, causing clogging, making it difficult to perform a smooth punching operation.

(3) With the diversification of demand for semiconductor devices, there is a trend toward high-mix, low-volume production of brazing filler metals, but as is well known, the cost of molds is high, so traditional manufacturing methods are not economically viable. There are cases where this doesn't work.

(4) Lubricating oil is used to extend the life of the mold and facilitate the peeling of the molded product from the mold, but the contamination caused by this oil must be removed in the next process. In addition, there are disadvantages specific to mold processing, such as the inevitable occurrence of deformation and burrs associated with shear processing, which increases as the number of times the mold is used, and the occurrence of distortion due to heat associated with processing deformation. exist.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention involves cutting a low melting point brazing filler metal into a thin plate with a thickness of 5 μm or more and cutting it into a predetermined shape by irradiating it with a laser beam. It was designed to do so.

As a laser beam generator, an appropriate device such as a gas laser or a semiconductor laser may be used, but a Y to G laser is preferable since a device with a small output is sufficient.

The reason why the thickness of the brazing filler metal is set to 5 μm or more is because if the thickness is less than this, the heat capacity of the material becomes small and precise processing becomes impossible.

[Function] In such a preform brazing filler metal forming method,
The energy of the laser beam irradiated onto the thin plate acts directly on the molecules that make up the thin plate material, causing them to sublimate. When a laser beam is moved along a predetermined trajectory, it can be applied to any shape or thickness, and regardless of the material, without any thermal or mechanical effects other than the irradiation location.
It can be cut into a predetermined shape without warping.

Examples] Examples of the present invention will be described in more detail below.

(1) A brazing filler metal having a composition of A u-'20wt$S n was processed into a 10 μm thick material using normal processing methods (rolling and shearing).
(T)

Pulse energy: 0.01 Joule Pulse width: 0
．． 15m5 Pulse frequency: l8011z Feed rate: 300mm/win Shape and dimensions: ■Outer diameter 2.0■φ, inner diameter! , 7a+mφ ring shape (see Figure 1) ■ Square ring shape with an outer diameter of 5.0g++a opening and an inner diameter of 4.0mm opening (see Figure 2) Also, as a comparative example, this was punched using a conventional mold. The occurrence of defects during molding was investigated. The mold forming conditions are as follows.

Mold material + S K I-i or Clearance condition = 5 μm or less Mold usage number of 200,000 times/piece Mold movement speed: 602 strokes/min (2) P b -10wL$S n Waxing 70μs(t)X50am(w)XI00a
+a+(j), and cutting was performed once using a YAG laser with an output of 4 under the following conditions.

Pulse energy +0.05 Joule Pulse width +0
．． 15m5 Pulse frequency: 18011z Feed rate: 15011IIl/win Shape and dimensions: ■Outer diameter 1.0.0ml 1 opening, inner diameter 8.0ml square ring shape with 11+ opening ■Outer diameter 20. Omm port, inner diameter 17. rhm
Corner ring shape of mouth (see Figure 2) As a comparative example, the occurrence of defects was investigated when this was punched and formed using a conventional mold. The molding conditions were the same as above.

The results are shown in the table on the next page.

As shown in the results, in the molding according to the method of the present invention, no microscopic or macroscopic stress acts at all since mechanical shearing is not performed. Therefore,
Compared to the conventional case, there is no warping or distortion of the edges after cutting, and there is no possibility of breakage at the thin crosspiece regardless of the material.

In addition, since it is not fused, there is no generation of flakes, and it is possible to produce a brazing material of good quality without being affected by the number of times it is used, unlike in the case of molds.

In addition, since the method of the present invention does not rely on a mechanical mechanism, a constant quality can always be achieved under the same conditions regardless of whether the brazing filler metal to be molded is made thinner or finer, or regardless of the material of the brazing filler metal. Can be molded into solder metal. Since the shape to be cut is determined by the movement of the laser beam, changing the shape only requires changing the program for beam movement, and there is no need for additional equipment. Therefore, even in the case of high-mix, low-volume production, which has been required in recent years, it is possible to respond quickly without increasing costs.

[Effects of the Invention] As detailed above, in this invention, a low melting point brazing filler metal is made into a thin plate with a thickness of 5 μm or more, and is cut into a predetermined shape by irradiating a laser beam. , the workpiece does not undergo mechanical or thermal deformation,
It is possible to stably produce high-quality brazing filler metal regardless of restrictions on shape, size, and material properties, and there is less equipment deterioration due to changes over time and less need for maintenance, reducing operating costs. can be done.

Similarly, even if the shape of the object to be molded changes, the movement path of the laser beam can be changed, so there is no increase in costs, and the present invention provides a molding method that has sufficient economic advantages even in high-mix, low-volume production. can do.

[Brief explanation of the drawing]

1 and 2 are perspective views of embodiments of the invention, respectively.

Claims (1)

[Claims] A method for forming a preform brazing material, which comprises forming a thin plate of low melting point brazing material into a thin plate with a thickness of 5 μm or more and cutting it into a predetermined shape by irradiating it with a laser beam.