TD Material (Decomposition Temperature) in PCB: A Comprehensive Overview

According to IPC-TM-650 Protocol 2.4.24.6, Decomposition Temperature or Td is the heating temperature where a PCB substance chemically decays or decomposes. The substance loses a minimum of 5% of its mass weight. Td is measured in degrees Celsius (°C), much as Tg. The material’s capacity to withstand heat is determined by this characteristic.

TD Materials Test Method Manual

IPC-TM-650 Laminate Material Decomposition Temperature. This testing method outlines a process for figuring out the heat deposition of substrate laminate through TGA or thermogravimetric analysis. This testing method may not produce comparable findings when used on PCBs or even other composite materials.

We must first generate test samples for this test procedure. The sample can be either an unclad laminated substance (CCL) or a laminate substance with all of the copper removed that’s been roughly square-cut (using just water cooling/cleaning, no oil) to slide further into the TGA sampling pan. Sample mass (weight) typically ranges from 10 mg-30 mg. Samples must be trimmed to the required size using the right techniques and tools to reduce thermal shock and physical stress. Samples having a lesser surface area and the same mass can lose mass more slowly.

By an analogous or sanding procedure, all sample edges must be polished smooth and free of burrs. This allows the testing sample to rest entirely flat or straight over the sampling pan. Be careful not to subject the sample to excessive heat or mechanical stress. The mass readings must be accurate to within +/-0.01 mg.

Thermogravimetric Analysis

The following components must be included in an analysis of the thermogravimetric or TGA instrument:

1. Null type microbalance with 0.001 mg sensitivity
2. Dry (dew point below -68°C [-90°F]), moisture below 3.5 ppm, and nitrogen (below 20 ppm o) purge are available on the furnace.
3. A temperature controller with a regulated 10°C+/-0.1°C [18°F+/-0.18°F] per min warming rate up to 800°C [1472°F]
4. The TGA must be able to accurately measure mass to the nearest 0.01 mg.

Test Procedure

1. Before testing, the samples of the test must be baked for almost 24 hrs at 110°C+/-2°C [230.0°F+/-3.6°F] and then cooled to room temperature. The TGA analysis should begin within 15 min of withdrawing the sample from desiccators in a conventional lab setting since samples may develop mass as a result of moisture content.
2. Set the balance’s accuracy to +/-0.01 mg.
3. Adjust the sensor’s calibration of temperature to within +/-1.0°C (1.8°F).
4. The purging rate should be set at 55cc/min (0.9mL/s). Thirty minutes should pass after the TGA air purging before introducing a sample. The calibration of the instrument will be significantly impacted by the rate at which the gas flows through the cell. As a result, the instrument should be calibrated using the same rate of flow as that utilized during the test. Positioning the digital thermometer should prevent it from coming into touch with the flow rate that will be utilized for the test. It is important to place the digital thermometer such that it never makes contact with any sample. The device may be calibrated once the thermometer has been placed properly. Following this, neither the flow rate nor the sensor placement should be altered.
5. Measure the sample’s mass after placing it into the TGA.
6. The sample should be heated at a temperature of 10°C/min from ambiance (no higher than 50°C) to 550°C.
7. Keep the temperature’s track, Td (2%), where the sample weighs 2.0% which is lesser than it did when it was recorded at 50°C.
8. Keep the temperature’s track, Td (5%), when the sample weighs 5.0% which is lower than it did when it was recorded at 50°C.
9. Provide the following details: 

Check The Temperature – TD PCB Materials

Monitoring PCB temperature is essential because it can prevent failure, as high temperatures can alter a PCB’s function and structure.

Tracking the temperature of PCB is particularly crucial since the consequences of excess heat don’t have to stay isolated. They have the potential to spread quickly across specific PCB components. This leads to numerous mistakes and damages. Overheating a PCB can lead to the following types of damage:

· Loss of Structural Integrity

Extreme heat can compromise the integrity of a PCB. When it becomes too hot or cold, layers of PCBs shrink and expand. This is because they are extremely delicate to temperature variations. High temperatures can induce warping in the widths, lengths, and thicknesses of some PCB layers.

· Disruption of Circuit Line

Excessive heat can potentially harm electrical circuits. Circuit wires expand and acquire new forms when they get too hot. When this happens, the circuits may be affected by distortions, frequency shifts, and direct losses. Its conducting impedance, which really is ordinarily 50 ohms, may also change. Microwave and millimeter-wave PCBs are susceptible to harm when tiny, delicate components expand or bend at high temperatures.

· Expansion Rate

Various substances stretch at varying speeds, exacerbating the previously listed detrimental impacts. The two most common layer types on a Circuit board are conductive metallic and dielectric layers. Because they are made up of different components, they react to heat in a different way and expand in diverse ways.

As a result, an overheated PCB may experience more harm and absorption of moisture when the different sorts of layers split.

· Oxidation

Concern exists over PCB electrical components oxidizing over high glass stream temperatures. Exposed dialectic substances used in PCBs are not shielded from oxidation if a protective laminate layer is not there. In that case, the material may corrode after being subjected to extreme heat. Increased dissipation is typically the result of transmission line breakdown.

Causes Of TD PCB Materials Heating UP

· Dissipation because of component failure

When an electric component fails and eventually dissipates, it is another common cause of excessive temperature in the PCB, as it does not produce the needed amount of power. The nearby components must provide additional power to compensate for this. Creating more electricity raises concerns about overheating.

· Interference Through-Hole

Through-hole and heat-sink electrical components make up the power-supplying components of PCB. They generate heat and radiate it into space. In order to compensate for incorrectly soldered through-hole or heat sinks interference from some other PCB component. However, the other components will generate considerably more heat than usual. In this situation, there is also a risk of overheating.

· SMD Distance

Surface-mount applications connect to the PCB in a similar way as through-hole electrical components. Through-hole and heat-sink components enable a more organized current flow from them. Through-hole and SMD components, however, must be appropriately separated from one another.

If they are too far away, this current must move farther. Because of the longer time needed for the current to travel, certain receiving electrical components may get too hot. Thus, other components can begin to overheat.

· High-Frequency

Compared to other applications, high-frequency PCB devices are more likely to face high temperatures. The reason is that greater heat will definitely come from increasing power output.

For instance, a rapidly growing field of PCB development is radio-frequency circuitry. Despite their intricacy, these circuits have a variety of real-world applications. This includes wireless security in medical and industrial equipment as well as smartphones. These Boards demand special design techniques, as high-frequency PCB can produce an excess amount of heat.

· Solder – Lead-Free

The PCB sector is changing in order to reduce dangerous elements. RoHS PCBs employ solder free from lead. This requires high temperatures to flow freely.