PCB Material Properties
Before we can talk about the impact of PCB material properties on the manufacturing of your board, we need to know what they are. Mechanical, electrical, thermal, and chemical qualities are among the most important.
- Bending (Flexural) Strength
When your board is bent, its ability to withstand deformation or fracture is measured. According to IPC-6013C, stiff, flex, and rigid-flex standards must be followed.
- Time to Delamination
When a PCB’s layers are exposed to temperature changes or moisture, this is a measurement of how long they will stay linked.
- Density (g/cm3)
The mass-to-volume ratio of a dielectric.
- Peel Strength
Under thermal and chemical stress, the capacity of copper layers and dielectrics to remain connected.
- Dielectric Constant
Affects a PCB material’s signal integrity and impedance. For high-speed applications, the frequency should be steady throughout a wide range of frequencies.
- Relative Permittivity
Referred to as relative dk.
- Surface Resistivity
The surface resistance of a dielectric substance to the flow of electricity. Temperature and moisture can cause it to change. To ensure good signal integrity, it should be set to a high value.
- Volume Resistivity
The volume resistance of a dielectric is measured. To ensure isolation between layers, keep it as high as possible.
- Dissipation Factor
A measurement of a PCB material’s signal or power loss. Although not a factor for digital signals, it can be significant for analogue signals, particularly at frequencies exceeding 1GHz, because Df rises with frequency.
- Electrical Strength
A PCB’s ability to withstand electrical breakdown in the z-direction.
- Glass Transition Temperature
The temperature at which a PCB substrate changes from hard to soft in a reversible manner. The temperature should be lower than the soldering temperature.
- Decomposition Temperature
The temperature at which a PCB substrate begins to degrade irreversibly. The temperature should be lower than the soldering temperature.
- Coefficient of Thermal Expansion
The pace at which a PCB expands in reaction to heat. In general, it’s best to keep it as low as possible.
- Thermal Conductivity
The rate at which heat is transmitted from one material to another. Conductors have a higher resistance than insulators.
- Methylene Chloride Resistance
Gives the percentage of methylene chloride, a volatile toxic solvent used in PCB manufacture, that has been absorbed. Dielectrics typically have a tolerance of 0.2 percent.
- Water Absorption
This figure indicates how much moisture the PCB material will absorb when submerged. This number is typically around 0.2 percent for most materials. A dielectric’s electrical and thermal characteristics may be affected.
There are time limits on how long a material can burn in reaction to combustion, according to the Standard for Safety of Flammability of Plastic Materials for Parts in Devices and Appliances (UL 94). The number of PCB materials per specimen is limited to ten.
As shown above, there are numerous PCB material qualities to consider. Let’s look at how you may use this data to improve your board’s manufacturing process.
Specifying Laminate Materials
The selection of appropriate materials is the first step in the PCB lamination process. The appropriate laminate is critical since it determines the final assembly’s stability, loss, and performance. Printed circuit board assembly can be supported by a variety of laminate alternatives.
Laminate materials play an important role in PCB performance
- Laminates consist of a resin system and reinforcement material, depending upon the laminate they are woven glass, ceramic, or glass microfibers
- Dielectric properties are highly dependent on the ratio of resin to the reinforcing material
- Specialty laminates are often required when thermal-mechanical or high frequency requirements exceed the properties of standard multifunctional epoxy based laminates
- Care should be taken when specifying laminate materials so boards can be produced consistently from lot to lot
- Specialty or “exotic” laminates come at a significant cost premium and hybrid constructions can offer significant cost reduction
- Reliability testing to validate material compatibility for lead free/CAF application is the key to success
Cerra Systems is one of the leading PCB manufacturing solutions providers with PCB manufacturing plants located in North America, Asia with certifications for MIL, AS, TS, ISO, & NADCAP. Our products are Rigid, Flex, Rigid-flex, HDI, RF, and hybrid PCBs addressing up to 64 layers and 2 mil technology. Cerra Systems Major PCB Market is Aerospace, defense, Medical, computing, cellular & Industrial. PCB Manufacturer Company in India
For more information, visit- http://cerrasystems.com/