CN108486618B

CN108486618B - Method for improving uniformity of electroplated thick gold

Info

Publication number: CN108486618B
Application number: CN201810597042.6A
Authority: CN
Inventors: 张长明; 黄建国; 王强; 徐缓
Original assignee: SHENZHEN BOMIN ELECTRONIC CO Ltd
Current assignee: SHENZHEN BOMIN ELECTRONIC CO Ltd
Priority date: 2018-06-11
Filing date: 2018-06-11
Publication date: 2021-01-01
Anticipated expiration: 2038-06-11
Also published as: CN108486618A

Abstract

The invention provides a method for improving the uniformity of electroplating thick gold, which comprises the steps of manufacturing an anode baffle plate on the periphery in a gold plating groove, manufacturing a movable anode baffle plate at the lower end of the gold plating groove, and sealing 50MM edges with PP plates on the periphery of the gold plating groove to shield the current tip effect formed excessively by more liquid medicine on the periphery and gold ions; the invention controls the uniform distribution of the gold plating current by the size of the clamp and the mode of the clamping plate, and greatly ensures that the plate edge of the plate to be plated is close to the electric power distribution in the plate. Compared with the prior art, the invention realizes the improvement of the uniformity of the plating thickness, improves the gold plating uniformity from 60-70% of the conventional level in the industry to 90-95%, greatly reduces the cost of gold salt and ensures the transmission quality of signals.

Description

Method for improving uniformity of electroplated thick gold

Technical Field

The invention belongs to the technical field of PCB manufacturing, and particularly relates to a method for improving the uniformity of electroplated thick gold.

Background

The core of the active phased array antenna design is the T/R assembly. The main factors for the design consideration of the T/R component are: the number of integrated circuits of different forms, the power output, the received noise figure, the amplitude and phase control precision, etc. Because the T/R module usually adopts a multi-chip module (MCM) technology to reduce the size, reduce the weight, and improve the module integration level, and a large number of microwave chips, logic control chips, power pulse modulation chips, and the like are integrated therein, higher requirements are put forward for the microwave printed board as a multi-chip and inter-chip interconnection wiring carrier.

The microwave printed board has strict loss control on signal transmission, the accuracy of the microwave printed board reaches the millimeter wave level, the material needs to be made of a PTFE composite material with ultralow loss, and in the aspect of surface treatment, a thick gold electroplating mode is adopted, namely the thickness of the gold electroplating needs to reach more than 80 microinches, a copper layer is arranged below the gold layer, and a nickel plating layer in the traditional nickel-gold plating mode is removed for bottoming, so that the interference of the nickel layer on electromagnetism is eliminated, the influence of passive intermodulation is reduced, and the stability of signal transmission is improved.

However, the thick gold plating process is only used in a small range of high end products because gold is very expensive. The gold plating equipment is not manufactured in a differentiation mode, the gold plating uniformity is relatively poor all the time, the conventional gold thickness in the industry is required to be 1-3 micro inches, and the gold plating uniformity is generally 60-70%. However, the gold plating uniformity is enlarged to a thickness of 80 micro inches, the waste of gold salt is very serious, and the signal transmission is affected by the difference of gold thickness.

Therefore, in the surface treatment process of microwave printed boards for high-end communication, it is necessary to provide a method for improving the uniformity of plating thickness.

Disclosure of Invention

Therefore, the invention aims to provide a method for improving the uniformity of thick gold electroplating, so as to solve the problem of poor uniformity of gold plating of a microwave printed board.

The purpose of the invention is realized by the following technical scheme.

A method for improving the uniformity of electroplated thick gold comprises the following steps: incoming inspection, sand blasting, edge covering, plate loading, oil removal, first double water washing, micro etching, second double water washing, first acid leaching, third double water washing, thin gold electroplating, first gold recovery, fourth double water washing, second acid leaching, fifth double water washing, third acid leaching, sixth double water washing, thick gold electroplating, second gold recovery, seventh double water washing, plate unloading, plate maintenance tank and cleaning and drying; wherein the electroplating of the thin gold comprises: manufacturing a thin gold electroplating bath, wherein the thin gold electroplating bath is made of a ruthenium iridium titanium net, the peripheral side walls of the interior of the thin gold electroplating bath are respectively provided with a fixed anode baffle, the lower end of the interior of the thin gold electroplating bath is provided with a movable anode baffle, and the four sides of any outer side wall of the thin gold electroplating bath are respectively provided with a PP plate for preventing electroplating from forming a current tip effect; opening a cylinder of the thin gold electroplating bath, and sequentially adding a 40% Auruna551 cylinder opening agent, 275g of gold potassium cyanide and 333 ml of Auruna 551B supplement into the thin gold electroplating bath; after the cylinder of the thin gold electroplating bath is opened, fixing the plate to be plated after the third double water washing by using a bilateral hanger, correspondingly placing the plate to be plated into the thin gold electroplating bath, and electroplating thin gold by adopting a twice turning-around gold plating mode; the electroplating of thick gold comprises: manufacturing a thick gold electroplating bath, wherein the thick gold electroplating bath is made of a platinum titanium mesh, the peripheral side walls of the interior of the thick gold electroplating bath are respectively provided with a fixed anode baffle, the lower end of the interior of the thick gold electroplating bath is provided with a movable anode baffle, and the four sides of any outer side wall of the thick gold electroplating bath are respectively provided with a PP plate for preventing electroplating from forming a current tip effect; opening a thick gold electroplating bath, and sequentially adding AURUNA 5100 opening agent with the concentration of 50%, 1376g of gold potassium cyanide and 67 ml of AURUNA 5100 supplement agent into the thick gold electroplating bath; after the thick gold electroplating bath is opened, fixing the plate to be plated after the sixth double water washing by using a bilateral hanging tool, and correspondingly placing the plate to be plated into the thick gold electroplating bath to plate thick gold by adopting a twice turning gold plating mode.

Furthermore, the two ends of the bottom of the thin gold electroplating bath and the two ends of the bottom of the thick gold electroplating bath are respectively and correspondingly provided with a lifting PP floating frame for adjusting the movable anode baffle to lift up and down.

Furthermore, four sides of any outer side wall of the thin gold electroplating bath and the thick gold electroplating bath are respectively provided with a PP plate which is used for preventing the electroplating from forming a current tip effect and has a width of 50 mm.

Furthermore, bilateral conductive hooks for clamping and fixing the plate to be plated and a telescopic cross rod are arranged on the bilateral hanging tool.

Further, the telescopic maximum length of the telescopic cross rod is 300 mm.

Furthermore, the thin gold plating bath and the thick gold plating bath are horizontal swinging baths, and the swinging amplitude of the swinging baths is 30-60 mm.

The invention is through making the positive pole baffle and lower end and making the movable positive pole baffle in the gilding trough all around and sealing 50MM sides with PP board all around the gilding trough, in order to shelter from the more peripheral liquid medicine and gold ion provide the tip effect of electric current formed excessively; the invention controls the uniform distribution of the gold plating current by the size of the clamp and the mode of the clamping plate, and greatly ensures that the plate edge of the plate to be plated is close to the electric power distribution in the plate. Compared with the prior art, the invention realizes the improvement of the uniformity of the plating thickness, improves the gold plating uniformity from 60-70% of the conventional level in the industry to 90-95%, greatly reduces the cost of gold salt and ensures the transmission quality of signals.

Drawings

FIG. 1 is a schematic diagram of a thin gold plating bath according to the present invention;

FIG. 2 is a schematic diagram of the structure of a thick gold electroplating bath according to the present invention;

FIG. 3 is a process flow diagram of the present invention for improving the uniformity of electroplated thick gold.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The method aims at solving the problems that the gold plating uniformity of a microwave printed board in the current industry is enlarged to 80 micro-inches, the waste of gold salt is serious, the difference of gold thickness is large, and the gold plating uniformity is poor. The invention provides a method for improving the uniformity of electroplated thick gold.

As shown in fig. 3, the method of the present invention mainly includes: incoming inspection, sand blasting, edge covering, plate loading, oil removal, first double water washing, micro etching, second double water washing, first acid leaching, third double water washing, thin gold electroplating, first gold recovery, fourth double water washing, second acid leaching, fifth double water washing, third acid leaching, sixth double water washing, thick gold electroplating, second gold recovery, seventh double water washing, a lower plate, a plate maintenance tank and cleaning and drying.

Wherein the improvement of the invention is the processes of electroplating thin gold and electroplating thick gold.

First, a thin gold plating bath 10 and a thick gold plating bath 10' are fabricated.

As shown in FIG. 1, the thin gold plating bath 10 of this embodiment is made of ruthenium iridium titanium mesh, which is mainly formed by the rear bath wall 11, the left bath wall 12, the front bath wall 13, the right bath wall 14, and the bottom bath wall, and four sides of the outer side walls of the rear bath wall 11, the left bath wall 12, the front bath wall 13, and the right bath wall 14 are each provided with a PP plate for preventing the plating from forming a current cusp effect, the PP plate having a width of 50 mm.

Taking the front groove wall 13 as an example, the PP plates formed on the four sides of the outer side wall are 131, 132, 133 and 134; the four sides of the outer side wall of the right cell wall 14

form PP plates

141, 142, 143, 144, respectively.

An anode baffle plate assembly 20 is formed within the thin gold plating bath 10, the anode baffle plate assembly 20 being defined by a rear anode baffle plate 21, a left anode baffle plate 22, a front anode baffle plate 23, a right anode baffle plate 24, and a movable anode baffle plate 25 within the anode baffle plate assembly 20.

The two ends of the bottom of the thin gold electroplating bath 10 are correspondingly provided with a lifting PP floating frame for adjusting the up-down lifting of the movable anode baffle 25, and the up-down lifting control and adjustment of the movable anode baffle 25 can be realized through the lifting PP floating frame. For the electroplating plates with different lengths, a movable anode baffle with the height of 150mm is manufactured, and when the height of the plates is higher than 500mm, the movable anode baffle 25 is adjusted to sink to the bottom of the tank through a lifting PP floating frame so as to shield the current of the top end of the bottom; if the plate height is lower than 500mm, the movable anode baffle 25 is adjusted to ascend through the reduction of the lifting PP floating frame correspondingly along with the plate height, so that the bottom of the anode shielding position is ensured to be the same as the bottom of the plate, the lower end gold thickness caused by the lower end tip effect formed due to the plate height change can be effectively reduced, and the uniformity of the electroplated thick gold is influenced.

Similarly, as shown in FIG. 2, the thick gold plating bath 10 ' of the present embodiment is made of ruthenium iridium titanium mesh, which is mainly formed by the rear bath wall 11 ', the left bath wall 12 ', the front bath wall 13 ', the right bath wall 14 ', and the bottom bath wall, and four sides of the outer side walls of the rear bath wall 11 ', the left bath wall 12 ', the front bath wall 13 ', and the right bath wall 14 ' are each provided with a PP plate for preventing the formation of the galvanic tip effect by plating, the PP plate having a width of 50 mm.

Taking the front slot wall 13 ' as an example, the PP plates formed by the four sides of the outer side wall are 131 ', 132 ', 133 ', 134 ' correspondingly; the four sides of the outer side wall of the right cell wall 14 ' form PP plates 141 ', 142 ', 143 ', 144 ' respectively.

An anode baffle plate assembly 20 ' is formed in the thick gold plating bath 10 ', the anode baffle plate assembly 20 ' is surrounded by a rear anode baffle plate 21 ', a left anode baffle plate 22 ', a front anode baffle plate 23 ', a right anode baffle plate 24 ', and a movable anode baffle plate 25 ' is also formed in the anode baffle plate assembly 20 '.

The two ends of the bottom of the thick gold electroplating bath 10 ' are correspondingly provided with a lifting PP floating frame for adjusting the up-down lifting of the movable anode baffle 25 ', and the up-down lifting control and adjustment of the movable anode baffle 25 ' can be realized through the lifting PP floating frame. For the electroplating plates with different lengths, a movable anode baffle with the height of 150mm is manufactured, and when the height of the plates is higher than 500mm, the movable anode baffle 25' is adjusted to sink to the bottom of the tank through a lifting PP floating frame so as to shield the current of the top end of the bottom; if the plate height is lower than 500mm, the movable anode baffle 25' is adjusted to ascend through the corresponding reduction of the lifting PP floating frame along with the height of the plate, so that the bottom of the anode shielding position is ensured to be the same as the bottom of the plate, and the lower end gold thickness caused by the lower end tip effect formed due to the height change of the plate can be effectively reduced, and the uniformity of the electroplated thick gold is influenced.

A bilateral hanger is correspondingly arranged above the thin gold electroplating bath 10 and the thick gold electroplating bath 10', pressing strips, screws and adjusting nuts are designed on two sides of the bilateral hanger, a built-in spring is arranged in each screw to facilitate good conductivity of plates with different thicknesses, telescopic cross rods are designed up and down, the widest telescopic width is 300mm, and the electroplated thick gold plates exceeding 300mm cannot be produced; the electroplating thin gold plate with the width of more than 300mm can be used for disassembling the built-in spring type double-side hanger into two electroplating single-side hangers for production, and is designed in a detachable movable connection mode, so that the disassembly, the assembly and the replacement are convenient, the electroplating thin gold plate is suitable for being used for products with different specifications and sizes, the usability of the hanger is improved, the gilding production efficiency is improved, all double-side hangers with built-in springs below nuts immersed into a gilding liquid medicine part are subjected to encapsulation treatment, an insulating layer is formed, the accuracy of current is guaranteed, gold salt is saved, and the cross pollution of the liquid medicine is avoided.

It should be noted that, in the present embodiment, the thin gold plating bath 10 is connected to a pipeline with a leak-proof basin, and the internal control dimensions are as follows: l350mm W900mm H800mm, the material of the tank body is made of a 12mmPP +20mm plate, an additional steel hoop is used for reinforcing to ensure that the tank body is not deformed, a group of filter tubes are arranged in the tank, and the anode is fixed to be flat stainless steel SUS316 (5mmX40MMX1100 MM). Ruthenium iridium titanium mesh for anode, size: L600XW550X1.8 (single sided ruthenium iridium thickness 5 microns) with a minimum 2: 1 area ratio of the anode ruthenium iridium titanium mesh to the work plate. Cathode 10 × 50 × 1100SUS316 stainless steel plate. The flow rate per hour is 4000L \ H, and the circulation of the vertical PP filter (gilding) is more than 10 MTO/H. The rectifier specification is 20A/12V/(220V input), a manual control box and a timing alarm are provided, the accuracy is two decimal places, and the minimum resolution is 0.1A. The heating tube Teflon heating tube is connected with a control line of 3 KW/220V.

In this embodiment, the connection pipeline of the thick gold plating bath 10' has a water leakage prevention basin, and the internal control size is as follows: l350mm W900mm H900mm, the material of the tank body is made of a 12mmPP +20mm plate, an additional steel hoop is used for reinforcing to ensure that the tank body is not deformed, a group of filter tubes are arranged in the tank, and an anode is fixed with flat stainless steel SUS316 flat (5mmX40MMX1100 MM). The anode is made of platinum titanium mesh, and the size is as follows: L600XW550X1.8 (single-sided platinum thickness 1.5 microns). Cathode 10 × 50 × 1100SUS316 stainless steel plate. The flow rate per hour is 4000L \ H, and the circulation of the vertical PP filter (gilding) is more than 10 MTO/H. The rectifier specification is 20A/12V/(220V input), a manual control box and a timing alarm are provided, the accuracy is two decimal places, and the minimum resolution is 0.1A.

After the thin gold plating bath 10 and the thick gold plating bath 10' are completed, they need to be opened separately.

For the opening of the thin gold plating bath 10, 400 ml of Auruna551 opening agent with a concentration of 40%, 275g of aurora potassium cyanide solution with a concentration of 0.8g/L and 333 ml of aurora 551B supplement with a concentration of 50 g of gold salt are sequentially added to the thin gold plating bath 10. For every 1g of pure gold deposited, 1.5 g of 68.3% gold salt and 10 ml of 551 extender B, water and other losses are added. The gold content should not be lower than 0.8g/L, the pH should not be higher than 4.5, the specific gravity can be adjusted by using citric acid or sodium hydroxide, the specific gravity can be adjusted by using conductive salt No. 2, 18g/l can be increased by 0.01g/ml, the horizontal swing is designed, and the swing is 3-6 cm.

After the cylinder of the thin gold electroplating bath 10 is opened, fixing the plate to be plated after the third double water washing by a bilateral hanger according to the process, correspondingly placing the plate into the thin gold electroplating bath, and electroplating thin gold by adopting a twice turning gilding mode, wherein the twice turning gilding mode is to clamp the upper end of the fixed plate for electroplating, and after the electroplating is finished, turning the lower end of the plate to be clamped at the upper end for electroplating again to ensure the uniformity of the electroplating; after the thin gold electroplating is finished, carrying out first gold recovery, fourth double water washing, second acid leaching, fifth double water washing, third acid leaching and sixth double water washing in sequence, and then carrying out thick gold electroplating.

The thick gold plating bath 10 'is opened, 400 ml of AURUNA 5100 opening agent with the concentration of 50%, 4g/L of gold potassium cyanide solution (containing 1376g of gold potassium cyanide) and 67 ml of AURUNA 5100 supplement (containing 50 g of gold salt) are sequentially added into the thick gold plating bath 10', continuous filtration is carried out, horizontal swing is designed, the swing is 3-6cm so as to swing the workpiece, and the pH is adjusted by citric acid or potassium hydroxide (chemical purity). The specific gravity of the plating solution is kept between 1.15 and 1.19g/cm 3, and 20g/l AURUNA 5100 specific gravity salt can be used for raising the specific gravity of the plating bath to 0.01 g/ml.

After the thick gold electroplating bath is opened, fixing the plate to be plated after the sixth double water washing by using a bilateral hanging tool, correspondingly placing the plate to be plated into the thick gold electroplating bath, performing thick gold electroplating by adopting a twice turning gold plating mode, and sequentially performing operations such as second gold recovery, seventh double water washing, lower plate, plate culturing bath, cleaning and drying after the thick gold electroplating.

The invention achieves the purpose of improving the uniformity of electroplating thick gold by manufacturing two gold electroplating tanks to respectively carry out thin gold electroplating and thick gold electroplating, electroplating thin gold for the first time, stabilizing the deposition rate of gold plating, and then electroplating gold for the second time.

Two anode baffles are manufactured in a gold plating groove, the anode baffles are manufactured on the periphery in the gold plating groove, a movable anode baffle is manufactured at the lower end of the gold plating groove, and a PP plate is used for sealing a 50MM edge on the periphery of the gold plating groove so as to shield the current tip effect formed by excessive gold ions due to more liquid medicine on the periphery; and the movable baffle plates manufactured in the gold groove can correspondingly adjust the height of the PP floating frame according to the length and the area of the thick gold plate to be plated through the liftable PP floating frames at the two ends of the gold groove.

In conclusion, the invention improves the gold plating uniformity from the conventional level in the industry of 60-70% to 90-95% through the improvement of equipment and the innovation of a manufacturing method, greatly saves the cost of gold salt, improves the uniformity of gold thickness and ensures the transmission quality of signals.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims

1. A method for improving the uniformity of electroplated thick gold is characterized by comprising the following steps: incoming inspection, sand blasting, edge covering, plate loading, oil removal, first double water washing, micro etching, second double water washing, first acid leaching, third double water washing, thin gold electroplating, first gold recovery, fourth double water washing, second acid leaching, fifth double water washing, third acid leaching, sixth double water washing, thick gold electroplating, second gold recovery, seventh double water washing, plate unloading, plate maintenance tank and cleaning and drying; wherein the electroplating of the thin gold comprises: manufacturing a thin gold electroplating bath, wherein the thin gold electroplating bath is made of ruthenium iridium titanium mesh, the peripheral side wall of the interior of the thin gold electroplating bath is respectively provided with a fixed anode baffle, the lower end of the interior of the thin gold electroplating bath is provided with a movable anode baffle, the four sides of any outer side wall of the thin gold electroplating bath are respectively provided with a PP plate which is used for preventing the electroplating from forming a current tip effect and has the width of 50mm, then opening a cylinder of the thin gold electroplating bath, sequentially adding 400 ml of Auruna551 cylinder opener with the concentration of 40 percent, 0.8g/L of Auruna potassium cyanide solution and 333 ml of Auruna 551B replenisher into the thin gold electroplating bath, supplementing 1.5 g of 68.3 percent gold salt and 10 ml of 551 replenisher B every 1g of pure gold deposited, the gold content is not lower than 0.8 g/liter, the pH is not higher than 4.5, adjusting and adjusting the specific gravity by using citric acid or sodium hydroxide, namely adjusting the proportion by using a conductive salt No. 2 and the proportion, level of designSwinging, wherein the swing amplitude is 3-6cm, after the cylinder opening of the thin gold electroplating bath is finished, fixing the plate to be plated after the third double water washing by using a bilateral hanger according to the process, correspondingly placing the plate into the thin gold electroplating bath, electroplating thin gold by adopting a twice turning gilding mode, turning gilding twice, namely clamping the upper end of the fixed plate for electroplating, turning the lower end of the plate to be clamped at the upper end after the electroplating is finished, and electroplating again to ensure the uniformity of electroplating; after the thin gold electroplating is finished, sequentially carrying out first gold recovery, fourth double water washing, second acid leaching, fifth double water washing, third acid leaching and sixth double water washing, and then carrying out thick gold electroplating; the thick gold electroplating method comprises the steps of manufacturing a thick gold electroplating bath, wherein the thick gold electroplating bath is made of a platinum titanium mesh, the peripheral side walls of the inside of the thick gold electroplating bath are respectively provided with a fixed anode baffle, the lower end of the inside of the thick gold electroplating bath is provided with a movable anode baffle, four sides of any outer side wall of the thick gold electroplating bath are respectively provided with a PP plate which is used for preventing the electroplating from forming a current tip effect and has the width of 50mm, then opening a cylinder of the thick gold electroplating bath, sequentially adding 400 milliliters of AURUNA 5100 open-tank agent with the concentration of 50%, 4g/L gold potassium cyanide solution and 67 milliliters of AURUNA 5100 supplement into the thick gold electroplating bath, carrying out continuous filtration, horizontally swinging, swinging by 3-6cm to swing a workpiece, adjusting the pH by using citric acid or potassium hydroxide, and keeping the specific gravity of the plating bath at 1.15-1.19 g/cm³20g/l AURUNA 5100 has the specific gravity of 0.01g/ml higher than that of heavy salt in a plating bath, after the cylinder opening of the thick gold plating bath is completed, the plate to be plated after the sixth double water washing is fixed by a double-side hanger, and the plate to be plated is correspondingly placed in the thick gold plating bath to be plated with thick gold by adopting a twice turning-around gold plating way.

2. The method for improving the uniformity of the electroplated thick gold according to claim 1, wherein a lifting PP floating frame for adjusting the up-and-down lifting of the movable anode baffle is correspondingly arranged at both ends of the bottom of the thin gold electroplating bath and the thick gold electroplating bath.

3. The method for improving the uniformity of electroplated thick gold according to claim 2, wherein the bilateral hanging tool is provided with bilateral conductive hooks for clamping and fixing a plate to be electroplated and a telescopic cross rod.

4. The method for improving the uniformity of electroplated thick gold of claim 3, wherein the telescopic maximum length of the telescopic cross bar is 300 mm.

5. The method for improving the uniformity of electroplated thick gold according to claim 4, wherein the thin gold electroplating bath and the thick gold electroplating bath are horizontal swinging baths with a swinging amplitude of 30 mm-60 mm.