The prepreg(PP) is the material that must be used to make multilayer PCB which is a sheet material composed of a resin and a carrier. The resin is in the B-stage, under the action of temperature and pressure, has fluidity and can rapidly cure and complete the bonding process, and forms an insulating layer together with the carrier. Commonly known as prepreg or bonding sheet. In order to ensure high reliability and quality stability of the multilayer printed circuit board(PCB), it is necessary to perform quality inspection (test lamination method) on the properties of the semi-solid film. 

    The prepreg characteristics include both pre-lamination characteristics and post-lamination characteristics. The properties before lamination mainly refer to: resin content percentage, fluidity percentage, volatile matter content percentage and gel time (second). The properties after lamination refer to electrical properties, thermal shock properties and flammability. For this reason, in order to ensure the high reliability of the multilayer printed circuit board(PCB) and the stability of the lamination process parameters, it is very important to detect the characteristics of the electroplated prepreg before lamination. 

1. Resin content (percentage) determination: 

(1) test piece production: plated prepreg fiber direction by circuit board, at 45° angle Cut into pieces of about 100 grams of 100 × 100 (mm) pieces;

(2) Weighing: Accurately weigh W1 (g) with a precision of 0.001 g;

(3) Heating and pressurizing: the temperature of the pressing plate heating plate is adjusted to 171±3°C. When the test piece is placed in the heating plate, the pressure is 14±2Kg/cm2 or more, and the heating and pressing are performed for 5 minutes, and the effluent gel is cut off. Weighing W2 (g);

(4) Calculation: Resin flow rate (%) = (W1-W2) / W1 × 1003. Gel time measurement:

a. Test piece production: According to the direction of the board plated prepreg fiber, cut into 50×50 at an angle of 45° (mm) several pieces (about 15 grams per piece);

b. Heating and pressurizing: adjusting the temperature of the heating plate to 171±3° C., and the pressure to be 35 Kg/cm 2 for 15 seconds;

c. Measurement: The test piece was measured from the start time of pressurization to the curing time. 

2. Volatile content side:

(1) test piece production: according to the direction of the board plated prepreg fiber, cut into a piece of 100 × 100 (mm) at a 45 ° angle;

(2) Weighing: use the accuracy of 0.001 gram balance to weigh W1 (g);

(3) Heating: using an air circulating thermostat, heating at 163 ± 3 ° C for 15 minutes and then weighing W2 (g) with a balance;

(4) Calculation: Volatile (%) = (W1-W2) / W1 × 100

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