DSC differential scanning calorimeter for testing the curing degree of PCB ink

Curing reaction refers to the chain reaction between epoxy functional groups and hardeners at an appropriate temperature. Curing degree is an important parameter for thermosetting polymer materials, and curing reactions are generally exothermic reactions. The amount of heat released is related to the type of resin functionality, the number of functional groups involved in the reaction, the type and dosage of curing agent, etc However, for a resin system with a determined formula, the heat of curing reaction is constant.

The curing degree of PCB ink can be tested using differential scanning calorimetry (DSC).Differential scanning calorimeterIt is a thermal analysis instrument that studies the thermal properties of materials by measuring the power difference (in the form of heat) between a sample and a reference at a programmed temperature as a function of temperature. DSC can measure the curing reaction temperature and thermal effect of materials, and understand the curing behavior of materials during heating.

In the PCB industry, the curing degree of epoxy based PCBs can be evaluated through DSC testing. For example, industry standards believe that when Δ Tg (change in glass transition temperature) is greater than 5 ℃, the curing degree of the material is incomplete and needs to be improved; When Δ Tg is less than 5 ℃, the product is completely cured. In addition, the DSC differential scanning calorimeter has sensitive testing accuracy and good repeatability, making it easy to determine the curing degree.

Differential scanning calorimeter is one of the effective tools for testing the curing degree of PCB ink. It can provide important information about the curing behavior of materials, help optimize production processes, and improve product quality.

　　1、 Working principle of DSC differential scanning calorimeter　

Heat flux DSC is a type of heat exchange calorimeter. The heat exchange between the sample and its surrounding environment can be measured through a specified thermal conduction path with a given thermal resistance. The heat exchange paths include disk type, turret type, and cylinder type measurement systems. Among them, disk based measurement systems are commonly used, with heat exchange carried out using disks that support solid samples. This system can quickly and accurately perform DSC measurements over a wide temperature range, which requires specific atmospheres such as nitrogen, oxygen, etc. In DSC with a disc measurement system, the main heat flows symmetrically from the furnace behind the disc to the sample crucible and reference crucible located on the disc. When no sample is added to the sample crucible, the heat flowing into the sample crucible and the reference crucible is the same, usually expressed in the form of a potential difference, where Δ T remains relatively constant. If any phase transition occurs in the sample, the steady-state equilibrium is disrupted, resulting in a differential signal proportional to the difference in heat flux rates between the two crucibles.

　　Figure 1 Measurement Unit of Heat Flux DSC

　2、 Operation steps for DSC testing PCB

1. Sample preparation:

Take a certain amount of PCB samples and ensure that the sample size is suitable for placement in the crucible of the DSC instrument.

2. Measuring instruments

DZ-DSC300 Differential Scanning Calorimeter

Instrument brand:Nanjing DaZhan Testing Instrument

3. Instrument settings:

3.1 Start the DSC instrument and set appropriate test parameters, including heating rate (usually 10-20 ° C/min) and temperature range (e.g. 25 ° C to 280 ° C).

3.2 Ensure that the preparation of the reference material is consistent with the sample to avoid data errors.

4. Testing process:

Place the sample into the sample slot of the DSC instrument and start the test. DSC will record the endothermic or exothermic reactions of the sample through temperature changes, generating a heat flow curve.

5. Analyze data:

Figure 1 Measurement Chart

Through the DSC curve (Figure 1), the transition temperature (such as glass transition temperature Tg) and heat flux changes of the ink during the curing process can be observed. The degree of curing is usually determined by Δ Tg (glass transition temperature change), and a Δ Tg greater than 5 ° C indicates incomplete curing.

6. Result Explanation

By analyzing the DSC curve of the sample and combining it with the change in Δ Tg, the curing degree of PCB ink can be determined. Low curing degree may affect the electrical performance and reliability of PCB boards.