JPH04110429A - High strength and high conductivity copper alloy for electronic equipment excellent in thermal peeling resistance of solder - Google Patents

Abstract

PURPOSE:To manufacture a high strength and high conductivity copper alloy for electronic equipment excellent in thermal peeling resistance of solder by incorporating specified ratios of Cr, Sn and Mn into Cu and preparing a copper alloy. CONSTITUTION:A high strength and high conductivity copper alloy for electronic equipment contg., by weight, 0.2 to 1.0% Cr, >0.2 to 1.0% Sn and >0.1 to 0.8% Mn, or furthermore, as auxiliary components, contg. total 0.01 to 2.0% of one or >= two kinds selected from the group consisting of Ag, Al, As, B, Be, Fe, Ge, Hf, In, Mo, Ni, Pb, Sb and V and the balance Cu with inevitable impurities and excellent in thermal peeling resistance of solder is prepd. More over, in this alloy, the content of 0 is preferably limited to <=30ppm and the content of S to <=20ppm.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a lead frame 4 of a semiconductor integrated circuit (IC).
] and terminals, connectors, relays, switches, etc. Particularly suitable for conductive applications such as solder heat and peel resistance (here, solder heat and peel resistance refers to the resistance of soldered or solder plated materials to the effects of heat, etc.) This relates to a high-strength, high-conductivity copper alloy that has excellent properties (meaning the property of having a peeling effect).

[Prior art 1] Kovar (Pe29Ni-16Co), which has a low coefficient of thermal expansion and good adhesion and sealing properties with elements and ceramics, has conventionally been used as a lead frame material for semiconductor integrated circuits.
High nickel alloys such as Fe-42Nj (Fe-42Nj) have been preferred. However, in recent years, as the degree of integration of semiconductor circuits has improved, the number of ICs with high power consumption has increased, resins are increasingly used as sealing materials, and improvements have been made to the bonding of elements and lead frames. As a result, copper-based alloys with good heat dissipation properties have come to be used for the lead frames used.

In general, lead frame systems for semiconductor integrated circuits are required to have the following characteristics.

(1) In addition to being a lead frame or electrical signal transmission part, it is also required to have the function of discharging heat generated during the packaging process and circuit use to the outside.
Exhibiting excellent thermal and electrical conductivity.

(2) Since the adhesion between the lead frame and the mold is important from the viewpoint of protecting the semiconductor element, the thermal expansion coefficients of the lead frame material and the mold material should be similar.

(3) It must have good heat resistance since various heating processes are involved during packaging.

(4) Most lead frames are manufactured by punching or bending lead frame materials, so the workability of these materials is good.

(5) Since the front side of the lead frame is plated with precious metals, the plating adhesion to these precious metals must be good.

(6) Good soldering is necessary because semi-EEI is often attached to the so-called outer lead portion, which is exposed outside the seal after packaging.

(7) Good corrosion resistance from the standpoint of equipment reliability and lifespan.

(8) Sort by price or lowest.

Oxygen-free copper, tin-containing copper, phosphor bronze, Kovar, and 42 alloy, which have been conventionally used, have advantages and disadvantages with respect to these various required properties, and do not satisfy all of these properties. On the other hand, CLICr-8n alloys have been developed as improved alloys by adding some additive elements to C1,+ -Cr-8n alloys in order to fully satisfy the above-mentioned required properties.
[Invention or Problem to be Solved] In recent years, reliability requirements for semiconductors have become more stringent, and surface mounting types that correspond to miniaturization have become more popular. It has become an important characteristic term.

In other words, lead frame and printed circuit board etc.
During use, the temperature of the lead frame and solder joint increases up to about 120'C due to external temperatures and heat generated by electricity.If exposed to such temperatures for a long time, the solder and Peeling from the lead frame occurs,
Since it is possible for a semiconductor to malfunction, if high reliability is required from the viewpoint of longevity, this solder heat peeling resistance is one of the most important characteristics. Among others, P P P
(I'1.AT P1.ASTICPACKAGE)
or PCLL (, PLASTIC+, 1>AI
) F shit) CHIP CAI? The surface-mounting type represented by Ii'1ER) is not inserted into the printed circuit board, but is surface-contacted, so half r [+ heat-resistant peelability is more important.

In addition, conventionally, as conductive spring materials for terminals, connector relays, switches, etc., inexpensive brass, nickel silver with excellent spring properties and corrosion resistance, or phosphor bronze with excellent spring properties have been used. However, brass is inferior in strength and spring properties, and nickel silver and phosphor bronze, which have excellent strength and spring properties, have a large amount of N1 in nickel silver and a large amount of Sn in phosphor bronze. Manufacturing: It is an expensive alloy due to processing constraints such as poor hot workability. Furthermore, when used for electrical equipment, etc., it has the disadvantage of low electrical conductivity.

Therefore, the emergence of an inexpensive alloy with good conductivity, strength, and spring properties has been awaited.

In the field of conductive spring materials, Cu-Cr-8
Improved alloys have been developed by adding some additive elements to n-based alloys. However, like lead frame materials for semiconductor integrated circuits, conductive spring materials are often coated with Sn or solder to reduce contact resistance and improve corrosion resistance. Heat-resistant peelability has become extremely important due to recent demands for reliability. In order to meet these strict requirements for heat-soldering and peeling properties (7), the C Ll -Cr-8n alloys developed to date cannot meet these requirements, so we developed a high-strength, high-conductivity copper alloy with improved heat-soldering and peeling properties. Yamagenka was awaited.

[Means for Solving the Problems] The present invention has been made to solve the problems, and improves the drawbacks of conventional copper-based alloys, and improves semiconductor integrated circuits (I
C) It is an object of the present invention to provide a copper alloy having suitable properties for use with conductive spring materials for lead frames, terminals, connectors, relays, switches, etc.

That is, in the present invention, Cr: exceeding 0.2vt%]
, 0w1% or less, S n : 0.2w1. % or more, 1. Ovt% or less, Mn + more than 0.1wt% and 0.8wt% or less, or further contains A as a subcomponent.
g5A1. As, B, Be, Fe5Ge, Hf
, Mo, Ni, pb, sb, v] species or two or more species in a total amount of 0.0 to 2.0wt
This is a high-strength, high-conductivity copper alloy for electronic devices that has excellent solder heat resistance and peelability, and is characterized by containing % Cu and unavoidable impurities. Such an alloy has a zero content of 30 ppm or less,
It is preferable to limit the S content to 20 ppm or less.

Next, the reason for limiting the alloy components constituting the alloy of the present invention will be explained.

Cr is added to precipitate metal Cr in the base material through aging treatment to improve strength and heat resistance.
The reason for setting w1% or less is that if it is less than 0.2wt%, the above-mentioned effect cannot be expected; on the contrary, 1. This is because if it exceeds Owt%, the conductivity, bendability, semi-porous properties, and plating adhesion will deteriorate significantly.

Sn is added to improve strength and heat resistance, and its content should be 0.0, exceeding 2vi% and 1.0w1%.
The following is 0.2wt% or less, the above effect can be expected, and 1. This is because if the content exceeds Owt%, a significant decrease in conductivity occurs.

Mn is added because it can be expected to have the effect of improving the solder heat resistance and peelability of Cu-Cr-Sn alloys. ．． ], wt% or less, the above-mentioned effect can be expected, and if it exceeds 0.8 wt%, a significant decrease in conductivity occurs.

Ag, Al5As, B5Be as subcomponents.

Fe, Ge, Hf, In, MoXNi, Pb1sb, v
A total amount of 0.01 to 2. The reason for adding Owt% is that it can be expected to have an effect of improving the strength without significantly reducing the conductivity.If the total amount added is less than 0.01w1, the above effect cannot be expected; This is because if it exceeds %, significant deterioration of conductivity and workability will occur.

O and S contents are each 30 ppm or less, 2゜ρp
The reason for setting it below m is that ○ content is 30 ppm, and
This is because if the content exceeds 20 ppm, plating adhesion will decrease.

[Example code] Next, the present invention will be specifically explained with reference to Examples.

Ingots of various compositions according to the present invention alloy and comparative alloy shown in Table 1 were melted using electrolytic copper or oxygen-free copper as a raw material in a high-frequency melting furnace in air, an inert atmosphere, or a reducing atmosphere. After face cutting these ingots, 850
Hot rolling was carried out at °C to a thickness of 8 mm, and after facing, cold rolling was carried out to a thickness of 1.5 mm. Then 950°
Solution treatment was carried out at C for 10 minutes, and the thickness was reduced to 0.5 mm by cold rolling.
It was made into a 25 mm plate, and finally aged at 420°C for 2 hours.

As evaluation items for lead frame system and spring rate,
The strength and elongation were determined by a tensile test, the bendability was determined by a 90° repeated bending test, the number of bends until breakage was determined as all+, with each reciprocation being one time, and the electrical conductivity (heat dissipation) was determined by the conductivity (%IA).
C3). Soldering properties were tested using the vertical immersion method in a half-LH bath (60% tin, 40% lead) at 230±5°C.
) for 5 seconds, and the state of solder wetting was evaluated by visually observing. Plating adhesion to the sample with a thickness of 3 μm
The sample was plated with Ag, heated at 450°C for 5 minutes, and visually observed for the presence or absence of blisters on the surface, giving an evaluation of 17. Heat resistance was expressed as the annealing temperature at which the hardness was 80% of the hardness before annealing when annealed for 5 minutes. The evaluation of solder heat resistance peeling was performed by applying 5 μm solder plating (60% tin, 4 lead) every month.
0%) and placed in a thermostat at 150°C. OOOh r
The sample was held until 100 hours, and the sample was taken out every 100 hours and bent at 90° and reciprocated once to check for peeling of the half [[). Regarding oxide film adhesion, heat a bare hand in the air at 200 to 500°C for 3 minutes to generate an oxide film on the surface, apply adhesive tape to the oxide film, and then carefully peel it off to remove the oxide film. Evaluation was made based on the presence or absence of peeling.

The spring properties were evaluated by determining the spring limit value (Kb) as Δ111. These results are shown in Table 1.

]　1 An explanation will be added regarding the present invention alloy and comparative alloy.

Invention alloys No. 1.4.6.8 and ]0.12.14 are based on the basic composition of the invention, and are excellent in strength, conductivity, and Hirata heat peeling resistance, as well as other properties. is also good. No, 2.3.5.7.9.11.13.1
No. 5 is a product in which subcomponents are added to the basic component system, and good characteristics similar to those of the basic component system can be obtained.

Comparative alloys No. 1 and No. 1 [i do not have sufficient amounts of Cr, and No. 17 and No. 17 do not have sufficient amounts of Sn, so they are inferior to the alloys of the present invention in terms of strength, spring properties, and heat resistance.

No. 18 has Cr exceeding 1.0 wt%, so
The conductivity, bendability, solderability, and plating adhesion are inferior to the alloys of the present invention. No. 19 has Sn of 1.0w1
%, the conductivity is inferior to that of the present invention.

No. 20 does not contain Mn, and the ○ content is [
Because of the high ioppm, the solder heat peeling resistance and plating adhesion are inferior to those of the alloy of the present invention. No. 21 has a high S content of 4 [ippm], so its plating adhesion is inferior to that of the alloy of the present invention.

[Effects of the Invention] As detailed above, the alloy of the present invention is excellent in strength, conductivity, solder heat resistance, and other properties. therefore,
The alloy of the present invention can be used for leads +2 and terminals of semiconductor integrated circuits,
Connector: Suitable for conductive springs such as re-I-no switches.

Claims (3)

[Claims] (1) Cr: more than 0.2wt% and less than 1.0wt%, S
n: more than 0.2wt% and less than 1.0wt%, Mn: 0.
A high-strength, high-conductivity copper alloy for electronic devices having excellent solder heat resistance and peelability, the alloy containing more than 1 wt% and 0.8 wt% or less, and the balance consisting of Cu and inevitable impurities. (2) Cr: more than 0.2wt% and less than 1.0wt%, S
n: more than 0.2wt% and less than 1.0wt%, Mn: 0.
More than 1wt% and 0.8wt% or less, and A as a subcomponent
g, Al, As, B, Be, Fe, Ge, Hf, In,
Solder heat-resistant peeling characterized by containing one or more selected from the group consisting of Mo, Ni, Pb, Sb, and V in a total amount of 0.01 to 2.0 wt%, with the balance consisting of Cu and inevitable impurities. A high-strength, high-conductivity copper alloy for electronic devices with excellent properties. (3) O content is 30 ppm or less, S content is 20 ppm
The high-strength, high-conductivity copper alloy for electronic devices as claimed in claim 1 or 2, which has excellent solder heat resistance and peelability.