PCB News - The Processing Flow of Circuit Board

Acid dip-full board copper electroplating-graphic transfer-acid degreasing-secondary countercurrent rinsing-micro-etching-secondary acid pickling-tinning-secondary countercurrent rinsing-acid dipping-graphic copper plating-secondary countercurrent rinsing-nickel plating -Secondary washing-citric acid immersion-gold plating-recycling-2-3 pure water washing-drying.

PCB electroplating process description

Pickling
1.Role and purpose
Remove oxides on the board surface and activate the board surface. The general concentration is 5%, and some are kept at about 10%. The main purpose is to prevent moisture from bringing in and cause unstable sulfuric acid content in the bath; the acid leaching time should not be too long to prevent oxidation of the board surface; After using for a period of time, when the acid solution becomes turbid or the copper content is too high, it should be replaced in time to prevent contamination of the surface of the electroplating copper cylinder and the plate; CP grade sulfuric acid should be used here.

2.Full board copper electroplating
Role and purpose
Protect just deposited
The thin chemical copper prevents the chemical copper from being etched away by acid after oxidation, and it is added to a certain extent by electroplating; the relevant process parameters of the full-plate copper electroplating: the main electronic components of the bath are copper sulfate and sulfuric acid, using high acid and low copper Formula to ensure the uniformity of the plate thickness distribution during electroplating and the deep plating ability for deep holes and small holes; the sulfuric acid content is mostly 180 g/l, and more than 240 g/l; the copper sulfate content is generally about 75 g/l, A trace amount of chloride ions are added to the bath liquid, which is used as an auxiliary gloss agent and the copper gloss agent to play the gloss effect together; the addition amount of the copper gloss agent or the opening amount is generally 3-5ml/L, and the addition of the copper gloss agent is generally in accordance with 1000A-hour method to supplement or according to the actual production board effect;

The current calculation of full-board electroplating is generally based on 2A/square decimeter multiplied by the electroplatable area on the circuit board.For full-board electricity, it is board length *board width * 2 * 2A/DM2; the temperature of the copper cylinder is maintained at room temperature State,the temperature generally does not exceed 32 degrees, and is mostly controlled at 22 degrees.Therefore,the copper cylinder is recommended to install a cooling temperature control system because the temperature is too high in summer.

Process maintenance: Replenish the copper polish in time according to the thousand-ampere hours every day,and add it according to 100-150ml/KAH; check whether the filter pump is working properly and whether there is air leakage; apply a clean wet cloth every 2-3 hours Clean the cathode conductive rod; analyze the copper sulphate (1 time/week), sulfuric acid (1 time/week), and chloride ion (2 times/week) content in the copper cylinder every week, and adjust the light through the Hall cell test.Clean the anode conductive rod and the electrical joints at both ends of the tank every week, and timely replenish the anode copper balls in the titanium basket. Use low current 0.2-0.5ASD to electrolyze for 6-8 hours.Check whether the anode titanium basket bag is damaged, and if it is damaged,replace it in time;check whether there is anode mud accumulated at the bottom of the anode titanium basket, and clean it up in time; and use a carbon core to continuously filter for 6-8 hours,and at the same time,low current electrolysis Miscellaneous; every six months or so,according to the pollution status of the tank liquid, it is determined whether a major treatment (active carbon powder) is required;the filter element of the filter pump should be replaced every two weeks.

Detailed processing procedures:Take out the anode, pour out the anode, clean the anode film on the surface of the anode, and put it in the barrel of the copper anode. Use a microetching agent to roughen the surface of the copper corner to a uniform pink color. After washing and drying,put it into the titanium basket and put it in the acid tank for later use; soak the anode titanium basket and anode bag in 10% lye for 6-8 hours, wash and dry, then soak with 5% dilute sulfuric acid, wash and dry for later use; Transfer the tank liquid to the spare tank, add 1-3ml/L of 30% hydrogen peroxide,start heating,wait until the temperature is about 65 degrees, turn on the air stirring, keep the air stirring for 2-4 hours; turn off the air stirring, press 3-5 g/L slowly dissolve the activated carbon powder into the tank solution. 

After the dissolution is complete, turn on the air and stir and keep it warm for 2-4 hours; turn off the air and stir, heat up, and let the activated carbon powder slowly settle into the tank Bottom; when the temperature drops to about 40 degrees, use a 10um PP filter element to add filter powder filter tank solution to the clean working tank, turn on the air and stir, put in the anode, hang into the electrolytic plate, and press 0.2-0.5ASD current density Low-current electrolysis for 6-8 hours; after laboratory analysis, adjust the sulfuric acid, copper sulfate, and chloride ion content in the tank to the normal operating range, and replenish the brightener according to the test results of the Hall cell; after the color of the electrolytic plate is uniform, that is The electrolysis can be stopped, and then the electrolytic film formation treatment is carried out at a current density of 1-1.5ASD for 1-2 hours, and a layer of uniform and dense black phosphorous film with good adhesion can be formed on the anode; try plating.

The anode copper ball contains 0.3-0.6% phosphorus,the main purpose is to reduce the anode dissolution efficiency and reduce the production of copper powder.

When replenishing drugs, if the amount of addition is large, such as copper sulfate or sulfuric acid, it should be electrolyzed at low current after adding. When adding sulfuric acid, pay attention to safety. When adding large amounts (above 10 liters),divide it several times slowly. Refill, otherwise it will cause the bath temperature to be too high, the photoagent will decompose faster, and the bath will be contaminated.

Special attention should be paid to the addition of chloride ions.Because the content of chloride ions is particularly low (30-90ppm), it must be accurately weighed with a graduated cylinder or cup before adding. 1ML hydrochloric acid contains about 385ppm of chloride ions.

Formula for adding medicine: Copper sulfate (unit: kg) = (75-X) * tank volume (liter)/1000 sulfuric acid (unit: liter) = (10%-X) g/L * tank volume (liter) Or (unit: liter) = (180-X) g/L * tank volume (liter)/1840 hydrochloric acid (unit: ml) = (60-X) ppm * tank volume (liter)/385

Acid degreasing
1.Purpose and function: Remove the oxide on the copper surface of the circuit, the remaining glue of the ink residual film, and ensure the bonding force between the primary copper and the patterned copper or nickel.
2.Remember to use acidic degreaser here, because the graphic ink is not alkali resistant and will damage the graphic circuit, so you can only use acidic degreaser before graphics electroplating.
3.During production, you only need to control the concentration and time of the degreaser. The concentration of the degreaser is about 10%, and the time is guaranteed to be 6 minutes. If the time is longer, there will be no adverse effects; the replacement of the tank liquid is also based on 15 square meters/liter. Working fluid, add 0.5-0.8L according to 100 square meters.

ipcb is a high-precision, high-quality PCB manufacturer, such as: isola 370hr PCB, high-frequency PCB, high-speed PCB, ic substrate, ic test board, impedance PCB, HDI PCB, Rigid-Flex PCB, buried blind PCB, advanced PCB, microwave PCB, telfon PCB and other ipcb are good at PCB manufacturing.