PCB circuit board copper sink quality control method

PCB circuit board copper sink quality control method

Electroless Plating Copper is commonly known as copper sinking. printed circuit board hole metallization technology is one of the keys to printed circuit board manufacturing technology. Strict control of the quality of the hole metallization is a prerequisite for ensuring the quality of the final product, while controlling the quality of the copper layer is critical. The commonly used test control methods are as follows:

    1. Determination of the rate of chemical copper sinking:

    The use of electroless copper plating bath has certain technical requirements for the rate of copper sinking. Too slow a rate may cause voids or pinholes in the walls of the hole; and the rate of copper sinking too fast will result in rough coating. To this end, the scientific determination of the rate of copper sinking is one of the means to control the quality of copper sink. Taking the electroless copper plating provided by Schering as an example, the method for measuring the rate of copper sinking is introduced:

    (1) Material: An epoxy substrate after copper etching, having a size of 100 × 100 (mm).

    (2) Determination procedure: A. The sample is baked at 120-140 ° C for 1 hour, and then weighed W1 (g) using an analytical balance; B. at 350-370 g / liter of chromic anhydride and 208-228 ml / liter of sulfuric acid Corrosion in the mixture (temperature 65 ° C) for 10 minutes, wash with water; C. Treat in chrome-free waste liquid (temperature 30-40 ° C) for 3-5 minutes, wash clean; D. Pre-dip, activation, reduction solution treatment according to the process conditions; E. In copper bath (temperature 25 °C) After half an hour of copper immersion, clean; F. The test piece is baked at 120-140 ° C for 1 hour to constant weight, and weighed W2 (g).

    (3) Calculation of copper sinking rate: rate = (W2-W1) 104 / 8.93 × 10 × 10 × 0.5 × 2 (μm)

    (4) Comparison and judgment: Compare and judge the measurement results with the data provided by the process data.

    2. Etching solution etching rate measuring method

    Before the through-hole plating, the copper foil is micro-etched to coarsen the micro-layer to increase the bonding force with the copper-clad layer. In order to ensure the stability of the etching solution and the uniformity of the etching of the copper foil, the etching rate is measured to ensure that it is within the range specified by the process.

    (1) Material: 0.3mm copper clad plate, degreasing, brushing, and cutting into 100×100 (mm);

    (2) Measurement procedure: A. The sample is etched in hydrogen peroxide (80-100 g / liter) and sulfuric acid (160-210 g / liter) at a temperature of 30 ° C for 2 minutes, washed and deionized water is cleaned; B. After baking at 120-140 ° C for 1 hour, weighed W2 (g) after constant weight, and the sample was weighed W1 (g) according to the condition before corrosion.

    (3) Etching rate calculation rate = (W1-W2) 104/2 × 8.933T (μm / min)

    Where: s-sample area (cm2) T-etching time (min)

    (4) Judgment: The corrosion rate of 1-2 μm/min is suitable. (1.5-5 minutes copper 270-540mg).

    3. Glass cloth test method

    In the process of hole metallization, activation and copper sinking are the key processes of electroless plating. Although qualitative and quantitative analysis of ionic palladium and reducing solutions can reflect the activation reduction performance, the reliability is not comparable to the glass cloth test. The most demanding conditions for copper in glass cloth are the best performance of activation, reduction and copper immersion. The brief introduction is as follows:

    (1) Material: The glass cloth was desulphurized in a 10% sodium hydroxide solution. And cut into 50 × 50 (mm), remove some glass filaments at the end of the four sides, so that the glass filaments are scattered.

    (2) Test procedure: A. The sample is treated according to the copper-plating process; B. Placed in the copper bath, after 10 seconds, the end of the glass cloth should be completely copper-plated, black or dark brown, all sink after 2 minutes, copper after 3 minutes The color is deepened; for the thick copper, after 10 seconds, the end of the glass cloth must be completely copper-plated, and after 30-40 seconds, all of the copper is sunk; C. Judgment: If the above effect of sinking copper is achieved, it means that the activation, reduction and copper sinking performance is good, but the reverse is worse.