Flow routing of multilayer PCB immersion gold deposition process

Gold sink multilayer circuit board - multi-layer circuit board process method, immersion gold process go gold craft is not available for printed circuit board process, its purpose is deposited on the surface of stable color, good brightness, smooth coating and good welding nickel gold plating. The basic process of gold deposition process is divided into four steps: pretreatment (degreasing, micro corrosion, activation, post immersion), nickel deposition, gold deposition, post treatment (scrap gold washing, DI washing, drying).


First, pretreatment


Gold pretreatment usually has the following steps: oil removal (30%AD-482), micro corrosion (60g/InaPS, 2%H2SO4), activation (10%Act-354-2), and post leaching (1%H2S04). In order to remove the copper surface oxide, and sink the palladium in the copper surface to be used as the precipitating nickel activation center. One of these processes is not good, which will affect the subsequent deposition of nickel and gold, and lead to the rejection of bulk properties. In the production process, all kinds of potions must be regularly analyzed and supplemented, controlled within the required range. For example, the more important: Micro etch rate should be controlled in the "25U 40U", the activation of copper content is more than 800PPM drops must open new cylinder, affect the quality of cleaning and maintenance of PCB potion cylinder of the antithetical couplet is large, in addition to microetch cylinder, cylinder, cylinder should be dipped after every week for each cylinder, cylinder should also be washed every week. Cleaning.


Two, sink nickel


The main component of electroless nickel drops to Ni2+ (5.1-5.8g/1) and reducing agent sodium hypophosphite (25-30g/1) and a stabilizer for more stringent requirements due to chemical nickel syrup composition range, each class must test two times in the production process, and according to the production of plate area of bare copper or experience adding reducing agent Ni2, supplementary feeding when,Should follow the small, scattered repeatedly feeding principle, in order to prevent partial plating reaction, plating solution due to accelerated aging, pH value, bath temperature is relatively large impact on the thickness of nickel, nickel solution temperature controlled at 85 DEG -90 DEG plagiarism. In PH 5.3-5.7, nickel cylinder production, the nickel cylinder temperature is reduced to 70 DEG C, to slow down the aging of the bath, the chemical nickel plating solution is sensitive to impurities, chemical composition of many harmful chemical nickel, can be divided into the following categories: inhibitors: including Pb.Sn..Hg.Ti.Bi (low melting point of heavy metal),


Organic impurities include S2, nitric acid and anionic wetting agents. All of these substances will reduce the activity, resulting in lower electroless plating speed and leakage plating, severe punishment will lead to a complete cessation of electroless nickel plating process.


Organic impurities include: in addition to the organic stabilizers mentioned above, there are also plastic agents and impurities from the equipment and solders. Although some impurities can be removed by continuous plating, they can not be completely removed.


Non stabilizers: including Pd and a small amount of copper. These two components are formed by chemical instability of nickel, making the coating rough and excessively plated on the channel wall and heater. Solid impurity: a solution that contains calcium sulfate or calcium phosphate and other insoluble substances that are trapped or brought into solution. Filtration removes solid particles.


In short: effective measures should be taken to reduce such impurities in the production process.


Three,immersion gold


Gold is a gold leaching process, the main component of gold cylinder; Au (1.5-3.5g/l), bond (Ec0.06-0.16mol/L), the nickel phosphorus alloy layer on the replacement of a gold plated monster, the coating is smooth, fine crystal, the bath pH value is generally between 4-5, control the temperature of 85 DEG -90 DEG C.


Four and aftertreatment


Gold postprocessing is also an important link to the printed circuit board, generally include: Scrap washing, DI washing, drying and other steps, conditional word can product of gold plate further washing plate with horizontal plate washing, drying. Horizontal plate washing machine according to the medicine wash (10% sulfuric acid, hydrogen peroxide, 30g/L) DI (30~50PSI), high pressure water washing DI washing, drying, drying and set up the order process, to completely remove the printed circuit board hole and surface drops and water stains, and uniform coating, good brightness of the gold plate.


 

(Source: internal information)

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