JPS62270739A - Copper alloy for lead frame - Google Patents

Abstract

PURPOSE:To satisfy various characteristics of a lead frame material and also to improve strength as well as electric conductivity, by incorporating, as essential components, specific amounts of Co and Zr to Cu. CONSTITUTION:A copper alloy for lead frames has a composition consisting of, by weight, 0.10-0.70% Co, 0.10-1.50% Zr, and the balance essentially Cu. If necessary, one or more kinds among 0.02-0.3% P, 0.05-0.5% Mn, 0.001-0.01% B, 0.01-0.35% Si, 0.05-0.20% Fe, 0.05-0.20% Ti, and 0.05-0.20% Cr are incorporated by 0.001-0.8%, in total, to the above copper alloy. Moreover, it is preferable that oxygen content and the grain size of the alloy are regulated to <=0.0010% and <=15mum, respectively. In this alloy, an intermetallic compound of Co and Zr is dispersedly precipitated finely and uniformly, so that strength and electric conductivity can be improved and superior heat resistance, plating suitability, etc., can be obtained.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Field of Industrial Application] This invention is a copper alloy suitable for lead frames for semiconductor devices such as ICs and LSIs, and which has particularly excellent conductivity and strength. This invention relates to a copper alloy for lead frames.

[Conventional technology]

Traditionally, lead frames for semiconductor devices have been made of alloy 42 (Fe-42%Ni) or copper, which has a coefficient of thermal expansion similar to that of Si, which is the material of semiconductor chips, and has excellent sealing properties for ceramics, glass, etc. Alloy (Fe29
Ni-17Co) etc. have been widely used. However, in recent years, as semiconductor devices such as LSIs have become more highly integrated, their power consumption has also increased, and lead frame materials are also required to have good heat dissipation (thermal conductivity). I hated it.

Improvements have been made to the bonding method between the lead frame and Si chip, and the sealing material has changed from ceramic and glass to epoxy resin, etc., resulting in improved thermal conductivity compared to conventional 42 alloys, etc. Good.

Copper thread lead frame materials, which have excellent resin moldability, are increasingly being used. Also.

As ICs, etc. become smaller and have more bins, lead frame materials are also becoming thinner, so it is important that the lead frame has sufficient mechanical strength so that it will not easily deform during IC assembly and inspection. There is a need.

In general, the properties required for lead frame materials include the following, including the above-mentioned thermal conductivity and strength.

(1) Excellent heat dissipation (thermal conductivity).

(聰) Relatively high strength.

(1) Good repeat bendability.

Qvl: Excellent heat resistance.

M: Good plating properties with solder, etc.

Furthermore, it is desired that the above-mentioned characteristics be satisfied and that the cost be lower. Therefore, efforts are currently being made to develop copper-based materials that satisfy these properties at higher levels.

By the way, the currently used copper lead frame material is CDA194 (Cu-2,45!1Fe
-0,1*Zn), Cu-0,1596Sn alloy, phosphor bronze (Cu-5% an-Q, 1% P), Cu-
Examples include 2%5n-0,2%Ni alloy.

[Problem that the invention seeks to solve]

However, these copper alloys do not necessarily satisfy the requirements for lead frame materials in terms of the balance between electrical conductivity (proportional to thermal conductivity) and strength. For example CDA 1
94 has a high electrical conductivity (65%lAC3), but its tensile strength (4S#f/IIj2) is slightly insufficient, and phosphor bronze has sufficient strength (53kEf/am2) but has a low electrical conductivity (1s 41AC8). Quite low.

As described above, conductivity and strength generally have contradictory properties, and if one is high, the other is low, so it has been difficult to obtain a copper-based lead frame material that satisfies both.

This invention was made to solve the above-mentioned problems, and is suitable as a lead frame for semiconductor devices that has excellent conductivity and strength, and also satisfies other requirements for lead frame materials. It provides copper alloys.

[Means for solving problems]

The copper alloy for lead frames according to the present invention is C.

0.10-0.70 wt 96. Zr0.10~1
．． 50 wt 96, and the remainder substantially consists of Cu.

[Effect]

In the present invention, in the specified composition range as described above, an intermetallic compound of Co and 2' is precipitated in a very uniform and finely dispersed manner in the Cu matrix, so that the above-mentioned improvements in electrical conductivity and strength are achieved. The obtained alloy has further improved heat resistance and adhesion properties.

〔Example〕

Hereinafter, this invention will be described in Examples 1 to 7 and Comparative Examples 8 to 1.
The explanation will be based on 0.

First, the composition shown in the table was prepared using a high-frequency bath furnace.

A piece with a thickness of 20 uX@80s+m and a length of 21011j1 was melted. Next, each lump was subjected to homogenization heat treatment at 800°C for 4 hours, and hot forged to a thickness of 121111XI.
After making it into a plate of l & 601111 x length 450sum 9
The surface was side-faced by 2sIII. Thereafter, intermediate annealing and cold rolling were repeated to process the material to a thickness of Q4 m.
Furthermore, these plates were heated at 450″cX1h in a nitrogen atmosphere.
After RFI blunting, the specimens were cooled down to obtain each sample with a plate thickness of 0.25 mm at a final cold working rate of 37%. However, for sample 43, after solution treatment with a thickness of 04 fl for 800' x 1 hr, it was cold worked at a processing rate of 37 mm, and then
Aging treatment was performed at 0°C for 2 hours.

Various properties such as electrical conductivity, tensile strength, repeated bendability, solder plating adhesion, and heat resistance were measured for each of these plate-shaped samples. The results are shown in the table.

Regarding repeated bendability, MIL-8TD-883
A method similar to test method B was used. That is, the thickness is 0.25+111XIl@? from each of the above plate-shaped samples. A rectangular sample with a length of 2° was collected as shown in Figure 9.

Grip part A with R=94m edge, B111.
(2) Horsefly Hold the above rectangular sample (3) at j=5g,
5oool load (add 41 and apply K 9 as shown by the arrow)
0' reciprocating bending was performed and the number of repeated bendings until breakage was measured. Here, the number of times of repeated bending is a value calculated by counting 90° left and right reciprocations as one time in nine drawings.

In addition, solder plating adhesion was determined by cleaning the surface of a rectangular sample similar to that used in the measurement of the above-mentioned repeated bending characteristics with 15 g of 6 salt and immersing it in a 60Sn-40Pb solder bath of 230 t' for 10 seconds in the atmosphere. 150”C inside
The samples held at 200° C. for 500 hr and 500 hr at 200° C. were subjected to 90° V bending and evaluated based on the presence or absence of peeling of the plating layer. In the table.

ISO”CX 500hr, 200℃x soo
The plating adhesion was good under both conditions of hr, and the adhesion was good under tso'c.
Items that were defective (with peeling) under ``C'' are marked with Δ.9 Items that were defective under both conditions are marked with X.Furthermore, regarding heat resistance, 350t
The tensile strength after heating was measured and evaluated.

According to the results in the same table, the Cu-Co-Zr alloy of the present invention has high electrical conductivity 1 strength that satisfies the property level required for lead frame materials, excellent repeated bending property,
Good solder plating adhesion and heat resistance are achieved.

In addition, P5 is seen in the samples of A3 to Muro.

If Mn* B and Si are used in combination, the oxygen content will be reduced, improving the integrity of the lump, suppressing the oxidative loss of Zr, which is the main component contained, and stabilizing the Zr content, making manufacturing work easier. At the same time, it is possible to further improve the adhesion of plating such as solder, which is important when used as a lead frame. In addition, the oxygen content is 0
．． It is appropriate to suppress the amount of these deoxidizing agents to 0.010 wt% or less.

Po, 02-0.3wt%, Mn0.05-0.5w
t%, B0. OO1-0.01wt%, Si 0.
01 to 0.35 wt% is appropriate. In other words, if the gap is small, the deoxidizing effect will be weak.

Too much content will have a negative effect on electrical conductivity, etc.

In addition, as seen in the samples from Mu 5 to Grave 7, Fe.

A slight addition of Ti and Cr to 1/kfj5 slightly lowered the electrical conductivity, but had the effect of improving strength and heat resistance. Regarding the amount of these metals added, if the amount is too small, the effect will be small, and if it is too large, the conductivity '*g will be reduced.
e 0.05~0.20 wt%, Ti0.05~
0.20wt%.

Cr 0.05 to 0.20 wt% is appropriate.

In addition, these P, Mn, B, Si, Fe
, Ti, Cr, etc. total addition is 0.01
~0.8 wt% is appropriate; if it is less than this, the effect of addition will be small, and if it is more than this, it will have an adverse effect on various objects.

Next, as seen in the comparative example, the content of CO and Zr is less than 0.1 wt% &8. 9 in the sample of Mu S
Poor strength, repeated bendability, and heat resistance.

On the other hand, the 410 sample with a Zr content of more than 1.5 Qwt% has excellent strength, repeated bending properties, and heat resistance, but has low conductivity and poor solder plating adhesion, and is cost-effective. It is also disadvantageous as a lead frame material. Although it is not shown in the table.

Similar results are obtained when the Co content is greater than 0.70 wt%.

Furthermore, in the alloy of the present invention, the grain size is 15
By making the alloy smaller than μm, the bending workability and repeated bendability of Alloy 9 can be further improved. The following method is suitable for reducing the grain size of the alloy as described above. Namely.

The cu-co-zr alloy with the composition of this invention is a precipitation hardenable alloy, and like general precipitation hardenable alloys, it cannot be subjected to high-temperature solution treatment followed by busy aging treatment to cause precipitation. Although it is possible, solution treatment at high temperatures will coarsen the crystal grains. Therefore, as the precipitation treatment described above, it is effective to perform R cooling (R medium cooling) after annealing at a relatively low temperature to cause precipitation during the cold storage process. This results in 1
A fine grain size of 5 μm or less is achieved, and an appropriate annealing temperature in this case is 400 to soo'c.

〔Effect of the invention〕

As described above, according to the present invention, Co 0.10
~0.70wt%, Zr0-IQ~1.5Qwt%, and the balance was substantially Cu, so the electrical conductivity.

The present invention has the effect of providing a copper alloy that is excellent in both strength and can be used as a lead frame material for semiconductor devices that satisfies various requirements for other lead frame materials.

[Brief explanation of drawings]

The drawings are explanatory diagrams illustrating a method of repeated bending tests on samples according to an example of the present invention and a comparative example. In the figure, (1) and (2) are grip parts A, B,
+31 is the sample, and (4) is the weight.

Claims (4)

[Claims] (1) Co0.10~0.70wt%, Zr0.10~
A copper alloy for lead frames containing 1.50 wt% of Cu, with the remainder substantially consisting of Cu. (2) P0.02-0.3wt%, Mn0.05-0.
5wt%, B0.001-0.01wt%, Si0.0
1-0.35wt%, Fe0.05-0.20wt%,
Ti0.05~0.20wt%, and Cr0.05~0
．． 20wt% of at least one species in a total amount of 0.001~
The copper alloy for lead frames according to claim 1, which contains 0.8 wt%. (3) The copper alloy for lead frames according to claim 1 or 2, which has an oxygen content of 0.0010 wt or less. (4) The copper alloy for lead frames according to any one of claims 1 to 3, which has a crystal grain size of 15 μm or less.