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2000 China's PCB production value of $ 3.635 billion , accounting for 8.7 % of global PCB output value , ranking fourth in the world . In China 's PCB output value , accounting for 83.5 percent of Guangdong . Therefore , the Guangdong region PCB plating is a great industry .

According to incomplete statistics , Guangdong PCB manufacturers only one phosphor material , the annual consumption of around 10,000 tons . PCB consumption of large enterprises phosphor 400-600 tons, 200-300 tons of medium-sized enterprises . Guangdong region acid copper plating PCB needs a year up to 1000 tons. Only phosphor bronze and acid copper plating annual sales value reached 4-5 million.

Surface treatment process involved in the production of PCB degreasing , to stain the inner wall of the hole , the activation treatment , electroless copper plating , direct plating process , plating tin alloy , copper etching , plating, gold processes. Therefore requires a lot of special plating chemicals and ordinary chemical raw materials, all add up to tens of billion yuan.

Specialty chemicals currently used in the PCB industry for more than 90 % of the large international companies such as the famous American company MacDermind, ShipleyLeaRonal former German company Schering, schlotter etc. monopoly ( now LeaRona to Shipley as mergers , Schering merged Atotech, MacDermind merger of British Canning). Only a handful of domestic research institutes and plating additive manufacturers products into one of the few small PCB business. One reason is that all the raw materials for PCB production requirements are very strict , and partly because many links PCB production value of expensive economic liability after a major quality problems . Therefore, the domestic research institutes engaged in surface treatment and electroplating additive producers only increase investment , the introduction of professional high-tech talent , purchase special equipment research and development, will it be possible to enter this market has great potential PCB industry .

1 conventional PCB electroplating

PCB ( double-sided and multilayer means ) to form an industrial scale , the company benefited from PCK published in 1963 patented electroless copper formulations and Shipley then in 1961 the company published patent colloidal palladium formula. They are able to make through-hole plating line runs automatically become the basis , the foundation technology also came to be widely accepted PCB production .

Since the 1990s , the traditional chemical copper as the main hole of (PTH) process subject to many pressures and challenges.

Here is a traditional PCB production process: "missing "

Cu plating solution of common features are:

( A ) contain a complexing or chelating agents such as sodium tartrate , EDTA and EDTP;

( 2 ) reducing the Cu plating are used formaldehyde ; while stabilizer Youyi cyanide as much.

The presence of complexing agent EDTA or EDTP to create great difficulties for wastewater treatment , formaldehyde is a known carcinogen , another drawback of the traditional copper plating is: side effects of the chemical copper plating bath maintenance and management difficulties , which cause chemical copper plating quality.

Electroless Copper is often due to the cost of underutilized and vary greatly. The cost of a non- continuous production of bath bath than a continuous production of high times. Therefore , electroless copper plating process has been plagued PCB manufacturer's problem.

2. The emergence and development of direct plating technology

In the 1980s , the United States and Europe to develop a more stringent environmental requirements , especially for toxic formaldehyde and intractable chelating emissions. Forced most solution providers seeking new ways to replace the traditional copper plating hole metallization achieved. Direct plating technology and its products have been a long time trial , PCB manufacturer to obtain recognition in the mid- 1990s.

As a substitute for direct electroless copper plating technology must meet the following criteria :

( 1 ) comprises on a non- conductive epoxy glass cloth , polyimide , polytetrafluoroethylene hole wall substrate , an electrically conductive layer is formed through a special process to achieve a metal plating. And must also ensure that the coating and the substrate having a good adhesion.

( 2 ) forming a conductive layer with a chemical solution to environmental pollution, easy to carry out the "three wastes " treatment, will not cause serious pollution.

( 3 ) Process  forming a conductive layer as short as possible , but requires a wide operating range should be easy to operate and maintain.

( 4 ) be able to adapt to a variety of PCB production. Such as high thickness / aperture ratio of the PCB, blind hole PCB , PCB and other special substrates .

Currently the world's direct plating techniques classified material can be summarized into three types : the first type is based on colloidal palladium process in a non- conductive surface Pd thin conductive metal technology , the second conductive polymer material is a conductive layer grafting technique called MnO2 ; third category is the suspension of carbon or graphite -based coating film direct plating techniques.

3. PCB plating a variety of surface coating process instance

PCB in the production process , in order to meet the requirements of the board , the need to use a variety of surface coating process , such as: hole metal , copper, nickel , gold, electroless nickel, electroless gold plating , organic flux protective film and electroplating tin-based alloys. The quality of the surface coating directly affects the quality of the printed circuit board , such as: appearance, weldability, corrosion resistance, wear resistance and other properties.

PCB surface coating technology for an incomplete summary:

1 ) metal hole : you can choose electroless copper process can also be used directly to copper plating . After the PCB hole metal , coated with a metallic copper 5 ~ 8μm .

2 ) hot melt or hot air leveling process:

Process is as follows :

Acidic degreasing --- microetch --- Activation --- tin-lead plating --- --- --- back to film --- etched tin-lead solder coating layer --- --- HASL flat

Or : Acid degreasing --- microetch --- Activation --- tin-lead plating --- --- --- to film etching --- Baptist bright --- melt .

3 ) gold plating board :

Process is as follows :

Acidic degreasing --- microetch --- Activation --- copper --- gold-plated nickel --- --- --- to film etching

4 ) gold-plated plugs :

Process is as follows :

Acidic degreasing --- microetch --- Activation --- Ni --- Pre -plated low-stress gilded gilded ---

5 ) organic flux protective film :

Process is as follows :

Acidic degreasing --- microetch --- Activation --- dip fluxing organic protective film

6 ) electroless nickel gold :

Process is as follows :

Acidic degreasing --- microetch --- prepreg --- palladium activator --- after electroless nickel immersion --- --- chemical leaching of gold --- thick gold plating

7 ) to the contamination process: double board or multilayer metal hole before removing the epoxy hole contamination , ensure metal hole quality. Its process is:

Swelling --- desmear --- neutralization.

Visible electroplating , electroless plating, displacement plating : Before plating, after plating electroplating process technology in the electronics industry is very active.

4 . The latest developments PCB electroplating technology

Early PCBs final surface finishing mostly using hot-dip tin-lead solder alloy hot air leveling (HASL) process . Due to the high temperature of hot-dip (about 250 ℃), surface-mounted components must have high temperature resistance , and after hot dip solder despite HASL , its surface is still uneven , is not suitable for surface mount (SMT) the implementation of new technology, can not be used aluminum bonding (AluminiumWireBonding). Therefore , great efforts in recent years to focus on developing low-temperature operation, and can get very flat surface can be bonded to weld new alternative HASL process , and achieved significant results , the rapid spread being produced .

Currently HASL process can be successfully replaced by new technology are:

① electroless nickel / gold plating soft , it is mainly used gold wire bonding (GoldWireBonding), but requires the whole line to be turned on .

② electroless nickel / gold plating replacement (EN / IG), also known as electroless nickel gold, it is suitable for welding and aluminum wire bonding, because the whole electroless plating , the line does not have to pass it to the pilot plating .

③ electroless nickel / electroless palladium / replacement gilt (EN / EP / IG), is intended to replace the earlier gold with cheap palladium, palladium prices in recent years, however, far more than gold ( about 3 times ) , so more and more less .

④ electroless nickel / gold plating replacement / electroless gold plating , it is suitable for soldering and gold wire , aluminum wire bonding.

⑤ The organic protective agent  welding (OrganicSolderabilityPreserative, OSP), which is adapted to 1-2 times remelting (Reflow) welding , but not for bonding.

⑥ displacement tin (IT), which is a new process , the coating is very smooth , only 1μm, excellent welding performance , but the thickness can be baked to 155 ℃ 4 -hour and 3 remelting , can completely replace the HASL, but not for bonding.

⑦ replacement Ag (IS), which is the latest and greatest technology . Very smooth coating thickness of only 0.2 ~ 0.3μm, by baking 155 ℃ 4 -hour and three times remelting , while suitable for aluminum wire bonding, is a cheap and replace HASL and chemical nickel plating (EN / IG) of the new technology. It is particularly suitable for high-density thin ( " < 0.02 " = and pore PCB, such as BGA, COB board applications.