CN102817055B - Ultrathin palladium plating and gold plating process for lead wire frame - Google Patents

Abstract

The invention discloses an ultra-thin palladium-plated gold-plated process for a lead frame, which comprises the following steps: electrolytic degreasing, lead frame substrate activation treatment, electrodeposited nickel layer, nickel layer activation treatment, electrodeposited palladium thin layer, high-frequency pulse Electrodeposition of gold-plated thin layer: Put the palladium-plated lead frame substrate into the gold plating solution for electrodeposition for 10-20 seconds, then wash with gold recovery water, dry it, and protect it with gold. The present invention forms an ultra-thin gold and palladium coating on the premise of ensuring that the test is passed. The thickness of the electroplated palladium layer is 0.02-0.1um, which is far lower than the thickness of the electroplated palladium layer of the existing process of 2-5um. The electroplated gold layer The thickness is 0.003-0.01um, which is far lower than the thickness of the gold layer electroplated by the existing process of 0.3-1.2um. While ensuring the excellent performance of the original palladium coating and gold coating, it reduces the consumption of gold and palladium, and greatly reduces the cost of precious metals. Use, effectively improve metal utilization and save costs.

Description

Ultra-thin palladium-plated gold-plated process for lead frame

【Technical field】

The invention relates to an electroplating process for a lead frame, in particular to an ultra-thin palladium-plating and gold-plating process for a lead frame, and belongs to the technical field of integrated circuit chip processing and manufacturing.

【Background technique】

Gold has extremely high chemical stability, insoluble in common acids, only soluble in aqua regia, so the gold coating has strong corrosion resistance, good anti-tarnish ability, and the coating has good ductility and is easy to polish, so it is often used as a decorative coating , such as plated jewelry, watch parts, artwork, etc. Gold has good electrical conductivity, is easy to weld, and can withstand high temperatures. The thermal conductivity of gold is 70% of that of silver. Therefore, it is widely used in the electroplating of precision instruments, printed plates, integrated circuits, military electronic tube shells, electrical contacts and other parts that require long-term stable electrical parameters.

Palladium is an excellent electrical contact material (resistivity of 0.099Ωmm/m). The coating thickness is generally 2 to 5 μm. The palladium coating has good weldability, and the palladium coating is an effective diffusion barrier layer. High-frequency components often use palladium as the middle layer to prevent the base metal from diffusing to the outer surface. The main disadvantage of palladium coating is that it is particularly sensitive to certain organic substances, and "brown powder" is easily formed on the surface, which greatly increases the contact resistance.

For the lead frame using the existing technology, the thickness of the palladium coating is 2-5 μm, and the thickness of the gold coating must reach 0.3-1.2 μm or more to meet the customer’s product test requirements. Usually, increasing the thickness of the gold/palladium layer can improve the quality and reliability of the lead frame. . However, as the price of precious metals continues to rise, so do costs. In this way, it is technically faced with the challenge of how to reduce the thickness of the gold/palladium layer to save costs while maintaining or even improving the quality and reliability of the lead frame.

【Content of invention】

The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art, and provide a lead frame ultra-thin lead frame that ensures the excellent performance of the original palladium coating and gold coating, reduces the thickness of the palladium coating and the gold coating, reduces the consumption of precious metals, and saves costs. Thin palladium-plated gold-plated process.

In order to solve the problems of the technologies described above, the present invention adopts the following technical solutions:

A lead frame ultra-thin palladium-plated gold-plated process is characterized in that comprising the following steps:

a. Electrolytic degreasing: Put the lead frame substrate into the electrolytic solution for 20-30 seconds, then wash and dry with tap water;

b. Activation treatment of the lead frame substrate: soak the electrolytically degreased lead frame substrate in an activation solution at room temperature for 10 to 20 seconds, then wash it with tap water, and then wash it with deionized water and dry it;

c. Electrodeposited nickel plating layer: Put the activated lead frame substrate into the nickel plating solution for electrodeposition for 50-60 seconds, then wash it with deionized water, and dry the lead frame;

d. Nickel layer activation treatment: put the nickel-plated lead frame substrate into the nickel activation solution and soak for 5-12s, then clean it with deionized water and dry it;

e. Electrodeposition of palladium-plated thin layer: put the nickel-activated lead frame substrate into the palladium plating solution for electrodeposition for 10-20 seconds, then wash it with deionized water and dry it;

f. High-frequency pulse electrodeposition gold-plated thin layer: put the palladium-plated lead frame substrate into the gold plating solution for electrodeposition for 10-20 seconds, then wash it with gold recovery water and dry it;

g. Over-gold protection: Put the gold-plated lead frame into the gold protection solution and soak for 5-20s, then wash and dry it with deionized water, and obtain the lead frame with ultra-thin palladium-coated gold-coated layer.

The ultra-thin palladium-plated gold-plating process for lead frames as described above is characterized in that the electrolytic solution contains an alkaline degreasing agent, and the alkaline degreasing agent is composed of degreasing powder and a wetting agent, and the degreasing powder is composed of The content is 60-80g/L, the current density of electrolysis is 5-25 amps/dm2, and the temperature of the electrolytic solution is 50-60°C.

The trade name of the above-mentioned alkaline degreasing agent is Ronaclean DLF, which is commercially available.

The ultra-thin palladium-plating and gold-plating process for lead frames as described above is characterized in that the activation solution is an acidic oxidizing agent containing 80-120 g/L of a cracking salt, and the cracking salt is a conductive activation salt.

The trade name of the crack salt contained in the above-mentioned acidic oxidizing agent is Actronal 988 crack salt, which is commercially available.

The above-mentioned ultra-thin palladium-plated gold-plated process for lead frames is characterized in that the nickel plating solution contains 50-70 g/L of nickel sulfamate, 35-55 g/L of boric acid, and the temperature of the nickel plating solution is 50-60 ° C. The pH value is 3.5-4.5, and the current density of electroplating is 5-25 ampere/square decimeter.

The above-mentioned ultra-thin palladium-plating gold-plating process for lead frame is characterized in that the thickness of the electroplated nickel layer is 0.5-2 μm.

The ultra-thin palladium-plating and gold-plating process for lead frames as described above is characterized in that the nickel activation solution contains 100-200ml/L of nickel activator, 10-30ml/L of sulfuric acid, and the temperature of the nickel activation solution is room temperature.

The trade name of the nickel activator used in the present invention is PC-1 nickel activator, which is commercially available.

The above-mentioned ultra-thin palladium-plated gold-plated process for lead frames is characterized in that the palladium plating solution contains 50-70ml/L of palladium salt solution, 250-500ml/L of open-cylinder salt, and the temperature of the palladium plating solution is 40-50 ℃, the pH value is 7.2-8.0, and the current density is 1-10 ampere/square decimeter.

The above-mentioned palladium salt solution is Palladure 200 (Rohm and Haas electronic material palladium solution, commercially available), and the described salt for opening the cylinder is Palladure 200 salt for opening the cylinder (available commercially).

The palladium content in the above-mentioned palladium plating solution should be controlled at 5.0-7.0g/L, and the specific gravity of the palladium plating solution should be controlled at 5-15. The specific gravity of the palladium plating solution can be adjusted by Palladure conductive salt (Palladure conductive salt is commercially available).

The above-mentioned ultra-thin palladium-plated gold-plated process for lead frames is characterized in that the gold plating solution contains 850-950 ml/L of pre-plating gold-plated potting agent, 2.2-3.6 g/L of potassium gold cyanide, and the gold-plated The temperature of the liquid is 40-45° C., the pH value is 3.5-4.0, and the current density is 3-10 ampere/square decimeter. The trade name of described pre-plated cylinder opener is Auro Strike GP-3 SEA (commercially available).

The gold content of the above-mentioned gold plating solution is controlled at 1.0-3.0g/L, and the specific gravity of the gold plating solution is controlled at 8-12, which can be adjusted with the trade name Auro Strike GP-3SEA conductive salt, which is commercially available.

The gold recovery water for cleaning the gold coating in the present invention is RO water, i.e. reverse osmosis water.

The ultra-thin palladium-plating and gold-plating process for lead frames as described above is characterized in that the temperature of the gold protection solution is 20-40° C., and the pH value is 2.0-3.5.

The above-mentioned gold protection solution contains 140-160 ml/L of components with trade name PostDip XP-680823-B MU (commercially available), and components 5-160 ml/L of trade name PostDip XP-680823-BAntifoam (commercially available). 20ml/L.

In the present invention, for cost saving consideration, after electrodepositing the palladium thin layer, the lead frame substrate can be washed with RO water and then rinsed with clean water, and the RO water is reverse osmosis water.

Compared with the prior art, the present invention has the following advantages:

The palladium coating of the present invention is bright and silvery in appearance, fine and smooth in crystallization, and has good connectivity and weldability, and can replace the silver plating of the inner leads and pads of the lead frame and the tin plating of the outer leads. Palladium is cheaper than silver and tin, reducing The use of precious metals silver and tin is eliminated; after palladium plating, a thin gold coating can be plated to stabilize the contact resistance, and the self-lubricating effect of the gold coating can improve wear resistance when plugging and unplugging.

The present invention forms an ultra-thin gold and palladium coating on the premise of ensuring that the test is passed. The thickness of the electroplated palladium layer is 0.02-0.1um, which is far lower than the thickness of the electroplated palladium layer of the existing process of 2-5um. The electroplated gold layer The thickness is 0.003-0.01um, which is far lower than the thickness of the gold layer electroplated by the existing process of 0.3-1.2um. While ensuring the excellent performance of the original palladium coating and gold coating, it reduces the consumption of gold and palladium, and greatly reduces the cost of precious metals. Use, effectively improve metal utilization and save costs.

This process is suitable for the surface treatment of industrial products and accessories with special requirements. It can replace the gold-plated layer for electrical contact components such as conductive rings, potentiometers, and brushes in instruments; it can be used for silver-plated conductive parts and electronic components. Discolored finish.

【Detailed ways】

The present invention is described in detail below in conjunction with specific embodiment:

An ultra-thin palladium-plated gold-plated process for a lead frame, which comprises the following steps:

a. Electrolytic degreasing: Put the lead frame substrate into the electrolytic solution of alkaline degreasing agent containing 60-80g/L degreasing powder. Electrolyze at ℃ for 20-30s, then wash the lead frame substrate with tap water and dry it;

b. Lead frame substrate activation treatment: put the electrolytically degreased lead frame substrate into an acidic oxidant solution containing 80-120 g/L of open-cyl salt at room temperature and soak for 10-20 seconds, then wash the lead frame substrate with tap water, and then use it Wash and dry with ion water;

c. Electrodeposited nickel plating layer: Put the activated lead frame substrate into a medium containing 50-70g/L of nickel sulfamate, 35-55g/L of boric acid, the temperature is 50-60°C, and the pH value is 3.5-4.5. Electrodeposition in the nickel plating solution at a current density of 5 to 25 amps/dm2 for 50 to 60 s, so that the thickness of the electroplated nickel layer is 0.5 to 2 μm, then clean the lead frame substrate with deionized water and dry it;

d. Nickel layer activation treatment: soak the nickel-plated lead frame substrate in nickel-containing activator 100-200ml/L, sulfuric acid 10-30ml/L, and room temperature nickel activation solution for 5-12s, and then use Clean the lead frame substrate with ion water and dry it;

e. Electrodeposition of palladium-plated thin layer: Put the nickel-activated lead frame substrate into Palladure 200 Palladium solution containing 50-70ml/L of Rohm and Haas electronic materials, Palladure 200 salt 250-500ml/L, and the temperature is 40 ～50℃, pH value 7.2～8.0, current density 1～10 amps/dm2 in the palladium plating solution for 10～20s, wash with palladium recovery water, then clean the lead frame substrate with deionized water and blow Dry;

f. High-frequency pulse electrodeposition gold-plated thin layer: put the palladium-plated lead frame substrate into the pre-plated gold cylinder containing 850-950ml/L, potassium gold cyanide 2.2-3.6g/L, and the temperature is 40-45°C , in a gold plating solution with a pH value of 3.5 to 4.0, electrodeposit for 10 to 20 seconds at a current density of 3 to 10 amperes per square decimeter to obtain a lead frame that has been electroplated, and then wash the lead frame with gold recovery water and dry it;

g. Over-gold protection: Put the gold-plated lead frame into the containing PostDip XP-680823-B MU140～160ml/L, PostDip XP-680823-B Antifoam 5～20ml/L, the temperature is 20～40℃, and the pH value is 2.0 Soak in ~3.5 gold protection solution for 5 ~ 20s, and then wash and dry with deionized water to obtain an ultra-thin palladium-coated gold-coated lead frame.

The above process is an immersion plating process, which can be completed in common equipment such as electroplating tanks.

The present invention is further described below by way of embodiment:

Example 1:

Put the lead frame base into an alkaline degreasing electrolytic solution containing 60g/L of degreasing powder, electrolyze for 30s at a current density of 5 amperes/dm2, and an electrolytic solution temperature of 50°C, and then wash the lead frame base with tap water blow dry again;

Soak the above-mentioned lead frame substrate in an acidic oxidant solution containing 80 g/L of open-pot salt at room temperature for 20 seconds, then wash the lead frame substrate with tap water, and then wash and dry it with deionized water;

Put the above-mentioned lead frame substrate into a nickel plating solution containing 50 g/L of nickel sulfamate and 55 g/L of boric acid at a temperature of 50° C. and a pH value of 4.5 for 60 seconds at a current density of 5 amps/dm2. The thickness of the electroplated nickel layer is 0.5-2 μm, and then the lead frame substrate is cleaned with deionized water and then dried;

Put the above-mentioned lead frame substrate into 100ml/L nickel-containing activator, 10ml/L sulfuric acid, and soak for 5s in a nickel activation solution at room temperature, then wash the lead frame substrate with deionized water and dry it;

Put the above-mentioned lead frame substrate into 50ml/L of Palladure 200 Rohm and Haas electronic material palladium solution, 250ml/L of Palladure 200 opening salt, the temperature is 50°C, the pH value is 7.2, and the current density is 1 ampere/square minute Electrodeposit in the palladium plating solution of rice for 10s, wash the lead frame substrate with deionized water after washing with palladium recovery water, and then blow dry;

Put the above-mentioned lead frame substrate into a gold plating solution containing 850ml/L of pre-plating potting agent, 2.2g/L of potassium gold cyanide, a temperature of 40°C, and a pH value of 4.0 at a current density of 3 amperes/square decimeter Electrodeposit for 10s to obtain a lead frame that has been electroplated, then wash the lead frame with gold recovery water and dry it;

Finally, put the above-mentioned lead frame into the gold protection solution containing PostDip XP-680823-B MU140ml/L, PostDip XP-680823-B Antifoam 5ml/L, the temperature is 20 ℃, and the pH value is 3.5. Wash and dry with deionized water to obtain a lead frame with an ultra-thin palladium-coated gold-plated layer.

The thickness of the palladium layer plated by the process of embodiment 1 is 0.02-0.08 um, and the thickness of the gold-plated layer is 0.003-0.007 um.

Example 2:

Put the lead frame base into an alkaline degreasing electrolytic solution containing 70g/L degreasing powder, electrolyze for 25s at a current density of 10 amperes/dm2 and a temperature of the electrolytic solution at 55°C, and then wash the lead frame base with tap water blow dry again;

Put the above-mentioned lead frame substrate into an acidic oxidant solution containing 100 g/L of open-pot salt at room temperature and soak for 15 seconds, then wash the lead frame substrate with tap water, and then wash and dry it with deionized water;

Put the above-mentioned lead frame substrate into a nickel plating solution containing 60 g/L of nickel sulfamate and 45 g/L of boric acid at a temperature of 55°C and a pH value of 4.0 at a current density of 15 amps/dm2 for 55 seconds. The thickness of the electroplated nickel layer is 0.5-2 μm, and then the lead frame substrate is cleaned with deionized water and then dried;

Put the above-mentioned lead frame substrate into 150ml/L nickel-containing activator, 20ml/L sulfuric acid, and soak for 9s in a nickel activation solution at room temperature, then wash the lead frame substrate with deionized water and dry it;

Put the above lead frame substrate into 60ml/L of Palladure 200 Rohm and Haas electronic material palladium solution, 380ml/L of Palladure 200 salt, the temperature is 45°C, the pH value is 7.6, and the current density is 5 amperes/square minute Electrodeposition in the palladium plating solution of rice for 15s, after cleaning with palladium recovery water, clean the lead frame substrate with deionized water and then blow dry;

Put the above-mentioned lead frame substrate into a gold plating solution containing 900ml/L of pre-plating gold-plated potting agent, 2.9g/L of potassium gold cyanide, a temperature of 43°C, and a pH value of 3.8 at a current density of 6 amperes/square decimeter Electrodeposit for 15s to obtain a lead frame that has been electroplated, then wash the lead frame with gold recovery water and dry it;

Finally, put the above-mentioned lead frame into the gold protection solution containing PostDip XP-680823-B MU150ml/L, PostDip XP-680823-B Antifoam 12ml/L, the temperature is 30 ℃, and the pH value is 3.0. Wash and dry with deionized water to obtain a lead frame with an ultra-thin palladium-coated gold-plated layer.

The thickness of the palladium layer plated by the process of embodiment 2 is 0.02-0.01 um, and the thickness of the gold-plated layer is 0.003-0.01 um.

Example 3:

Put the lead frame base into an alkaline degreasing electrolytic solution containing 80g/L of degreasing powder, electrolyze for 20s at a current density of 25 amps/dm2, and an electrolytic solution temperature of 60°C, then wash the lead frame base with tap water blow dry again;

Soak the above-mentioned lead frame substrate in an acidic oxidant solution containing 120 g/L of open-pot salt at room temperature for 10 seconds, then wash the lead frame substrate with tap water, and then wash and dry it with deionized water;

Put the above-mentioned lead frame substrate into a nickel plating solution containing 70 g/L of nickel sulfamate and 35 g/L of boric acid at a temperature of 60° C. and a pH value of 3.5 for 50 seconds at a current density of 25 amps/dm2. The thickness of the electroplated nickel layer is 0.5-2 μm, and then the lead frame substrate is cleaned with deionized water and then dried;

Put the above-mentioned lead frame substrate into 200ml/L nickel-containing activator, 30ml/L sulfuric acid, and soak for 12s in a nickel activation solution at room temperature, then wash the lead frame substrate with deionized water and dry it;

Put the above lead frame substrate into 70ml/L of Palladure 200 Rohm and Haas Electronic Materials palladium solution, 500ml/L of Palladure 200 opening salt, the temperature is 40°C, the pH value is 8.0, and the current density is 10 amperes/square minute Electrodeposition in the palladium plating solution of rice for 20s, wash with palladium recovery water and then clean the lead frame substrate with deionized water and then blow dry;

Put the above-mentioned lead frame substrate into a gold plating solution containing 950ml/L of pre-plating gold-plated potting agent, 3.6g/L of potassium gold cyanide, a temperature of 45°C, and a pH value of 3.5 at a current density of 10 amperes/square decimeter Electrodeposition for 20s to obtain a lead frame that has been electroplated, then wash the lead frame with gold recovery water and dry it;

Finally, put the above-mentioned lead frame into the gold protection solution containing PostDip XP-680823-B MU160ml/L, PostDip XP-680823-B Antifoam 20ml/L, the temperature is 40℃, and the pH value is 2.0 for 5s, and then use Wash and dry with deionized water to obtain a lead frame with an ultra-thin palladium-coated gold-plated layer.

The thickness of the palladium layer plated by the process of embodiment 3 is 0.04-0.1 um, and the thickness of the gold-plated layer is 0.004-0.01 um.

Example 4:

Put the lead frame base into an alkaline degreasing electrolytic solution containing 70g/L of degreasing powder, electrolyze for 25s at a current density of 151 amperes/dm2, and an electrolytic solution temperature of 60°C, and then wash the lead frame base with tap water blow dry again;

Soak the above-mentioned lead frame substrate in an acidic oxidant solution containing 90 g/L of open-pot salt at room temperature for 13 seconds, then wash the lead frame substrate with tap water, and then wash and dry it with deionized water;

Put the above-mentioned lead frame substrate into a nickel plating solution containing 65 g/L of nickel sulfamate and 40 g/L of boric acid at a temperature of 55° C. and a pH value of 3.5 for 55 seconds at a current density of 10 amps/dm2. The thickness of the electroplated nickel layer is 0.5-2 μm, and then the lead frame substrate is cleaned with deionized water and then dried;

Put the above-mentioned lead frame substrate into 180ml/L nickel-containing activator, 25ml/L sulfuric acid, and soak for 10s in a nickel activation solution at room temperature, then wash the lead frame substrate with deionized water and dry it;

Put the above lead frame substrate into Palladure 200 Palladium solution containing 65ml/L of Rohm and Haas Electronic Materials, 450ml/L of Palladure 200 salt, the temperature is 45°C, the pH value is 7.5, and the current density is 7 amperes/square minute Electrodeposition in the palladium plating solution of rice for 15s, after cleaning with palladium recovery water, clean the lead frame substrate with deionized water and then blow dry;

Put the above-mentioned lead frame substrate into a gold plating solution containing 900ml/L of pre-plating gold-plated potting agent, 2.6g/L of potassium gold cyanide, a temperature of 45°C, and a pH value of 3.5 at a current density of 5 amperes/square decimeter Electrodeposit for 15s to obtain a lead frame that has been electroplated, then wash the lead frame with gold recovery water and dry it;

Finally, put the above-mentioned lead frame into the gold protection solution containing PostDip XP-680823-B MU155ml/L, PostDip XP-680823-B Antifoam 15ml/L, the temperature is 35 ℃, and the pH value is 2.5. Wash and dry with deionized water to obtain a lead frame with an ultra-thin palladium-coated gold-plated layer.

The thickness of the palladium layer plated by the process of embodiment 4 is 0.03-0.09 um, and the thickness of the gold-plated layer is 0.004-0.09 um.

Claims (5)

1. a lead frame ultra-thin plating palladium craft of gilding, is characterized in that comprising the following steps:

A, electrolytic degreasing: leadframe base is put into electrolytic solution electrolysis 20 ~ 30s, then dry up with tap water cleaning;

B, leadframe base activation treatment: the activated solution leadframe base of electrolytic degreasing being put into room temperature soaks 10 ~ 20s, then with tap water cleaning, then dry up by washed with de-ionized water;

C, electrodeposit nickel plating layer: leadframe base activation treatment crossed puts into nickel plating bath galvanic deposit 50 ~ 60s, then dries up by washed with de-ionized water again;

D, nickel dam activation treatment: the leadframe base of nickel layer is put into nickel activated solution and soaks 5-12s, then dry up again by washed with de-ionized water;

E, galvanic deposit plating palladium thin layer: the leadframe base after being activated by nickel puts into palladium plating solution galvanic deposit 10 ~ 20s, then dries up by washed with de-ionized water again;

F, the gold-plated thin layer of high-frequency impulse galvanic deposit: the leadframe base after plating palladium is put into golden plating solution galvanic deposit 10 ~ 20s, then dry up with golden recycle-water cleaning again;

G, cross gold protection: gold-plated leadframe base is put into gold protection solution soak 5-20s, then dry up by washed with de-ionized water, obtain the lead frame of ultra-thin palladium coating gold plate;

Wherein said nickel plating bath is containing thionamic acid Nickel 50 ~ 70g/L, boronic acid containing 35 ~ 55g/L, and nickel plating bath temperature is 50 ~ 60 DEG C, and pH value is 3.5 ~ 4.5, and current density is 5 ~ 25 amperes/square decimeter;

Wherein said palladium plating solution is containing palladium salts solution 50 ~ 70ml/L, and open cylinder salt 250 ~ 500ml/L, the temperature of palladium plating solution is 40 ~ 50 DEG C, and pH value is 7.2 ~ 8.0, and current density is 1 ~ 10 ampere/square decimeter;

Wherein said golden plating solution is containing pre-gold-plated open cylinder agent 850 ~ 950ml/L, potassium auric cyanide 2.2 ~ 3.6g/L, and the temperature of described golden plating solution is 40 ~ 45 DEG C, and pH value is 3.5 ~ 4.0, and current density is 3 ~ 10 amperes/square decimeter.

2. lead frame according to claim 1 ultra-thin plating palladium craft of gilding, it is characterized in that described electrolytic solution is containing alkaline defatting agent, described alkaline defatting agent is made up of degreasing powder and wetting agent, the content of described degreasing powder is 60 ~ 80g/L, current density is 5 ~ 25 amperes/square decimeter, and the temperature of electrolytic solution is 50 ~ 60 DEG C.

3. lead frame according to claim 1 ultra-thin plating palladium craft of gilding, is characterized in that described activated solution is acidic oxidation agent, containing opening cylinder salt 80 ~ 120g/L.

4. lead frame according to claim 1 ultra-thin plating palladium craft of gilding, is characterized in that the thickness of described electroless nickel layer is 0.5 ~ 2 μm.

5. lead frame according to claim 1 ultra-thin plating palladium craft of gilding, it is characterized in that the temperature of described gold protection solution is 20 ~ 40 DEG C, pH value is 2.0 ~ 3.5.