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PCB Assembly

Editorial Team - PCB Directory

Apr 24, 2020

PCB Tombstoning occurs due to a mismatch in the solder solidification time during the PCB assembly process. The term solder solidification or ‘Wetting’ comes in to the picture when surface mount components are soldered to their respective pads. To do so, solder is applied on the PCB board, after which the component is placed on the board and then passed through a reflow oven, where it ...read more

What is the Coefficient of Thermal Expansion (CTE) in a PCB?

PCB Basics

Editorial Team - PCB Directory

Apr 24, 2020

The Coefficient of Thermal Expansion (CTE) specifies how much a printed circuit board will expand/contract when it is heated or cooled. The unit of CTE is PPM/°C i.e parts per million per Celsius degree. So lets assume a PCB is made out of FR4 which has a CTE of 17 (usually it is 14 to 17 ppm/°C). If the PCB is 1 Million inches long then it will expand by 17 inches for every 1 °C incre...read more

What is BGA Reballing?

PCB Repair

Editorial Team - PCB Directory

Apr 24, 2020

The process of replacing all soldered balls on the chip ball grid array is called BGA Reballing. BGA or Ball Grid Array is a surface mount package that has an array/grid of metal alloy balls (Tin/ Silver/ Lead/ Copper) at the bottom of a package which is soldered on to a printed circuit board to provide an electrical connection. This package type requires less space than other package types as all...read more

What is a PCB Test Coupon?

Editorial Team - PCB Directory

Apr 24, 2020

During the PCB Manufacturing process, it is important to evaluate the quality of the boards being fabricated. A good way to do this is to fabricate a few extra boards called PCB Test Coupons which can be tested to evaluate the performance of the boards. PCB Test Coupons are designed to have the same spec (trace width, copper weight, via structure, etc.) as the original PCB board and are tested to ...read more

What is ENIG Plating?

Editorial Team - PCB Directory

Apr 13, 2020

ENIG (Electroless Nickel Immersion Gold) is a surface plating that is applied over the copper pads on a Printed Circuit Board to protect them from corrosion and other abnormalities. Initially, the copper pad is covered by a Nickel (Ni) layer followed by a thin immersion Gold (Au) layer. ENIG provides good oxidation resistance, excellent surface planarity and allows for easy soldering which results...read more

What is HASL - Hot Air Solder Leveling?

Editorial Team - PCB Directory

Jan 15, 2020

HASL (Hot Air Solder Leveling) is a metallic surface finishing technique, which is performed on the outermost layer of the PCB board to protect the exposed copper surfaces like tracks until the component placement and soldering is completed.The HASL coating is composed of Solder with 63% Tin and 37% Lead, and during the assembly process, this coating gets dissolved with the soldering material.The ...read more

What are PCB Gold Fingers?

PCB Basics

Editorial Team - PCB Directory

Jan 15, 2020

Gold Fingers are the gold plated narrow connectors found on the edge of printed circuit boards to enable connections between multiple boards. They are made from flesh gold, the hardest form of gold available and work for a long time with superior conductivity. The thickness of gold fingers usually ranges from 3 to 50 microns.Gold is chosen for these fingers as it has the highest corrosion resistan...read more

What are Fiducial Marks on a PCB?

PCB Basics

Editorial Team - PCB Directory

Jan 15, 2020

Fiducial marks are recognition marks, created in the form of small pads on the PCB board to act as reference points for PCB Stencil alignment and for automated component placement by Pick and Place machines. During the PCB Assembly process these points are used by automated machines to ensure correct positioning of the board. These points are also measurable and act as a frame of reference during ...read more

What is PCB V-Scoring?

PCB Basics

Editorial Team - PCB Directory

Jan 15, 2020

PCB V-Scoring is a process of cutting a ‘V’ shaped groove at the top and bottom of a printed circuit board leaving a thin layer between the Vees. Once this is done, the PCB Board can easily be separated at the V by applying minimal pressure.A single PCB board can be divided in to multiple sections by V-Scoring. This is must useful during the PCB assembly process, as all sections of the...read more

Polyester PCB Boards

PCB Substrates

Editorial Team - PCB Directory

Sep 15, 2019

Polyesters, also called Polyethylene Terephthalate (PET), are the most commonly used material to manufacture flexible PCBs. They are best-known for their flexibility, good electrical properties, and high chemical and moisture resistance.Key Characteristics:They have a melting point of 250ºC and a glass transition temperature of 80ºC.They have lower heat resistance that inhibits their use...read more

What are Copper Based PCBs?

PCB Substrates

Editorial Team - PCB Directory

Sep 14, 2019

Copper-based PCBs use copper as a primary base material in place of commonly used FR4. The copper base material is then covered with an insulating layer followed by a circuit layer. Copper core/based PCBs are known to have excellent heat dissipation and can be used for high frequency applications with minimal variation in performance over wide temperature ranges. However, these advantages do come ...read more

What are Aluminum-based PCB boards?

PCB Substrates

Editorial Team - PCB Directory

Sep 14, 2019

Aluminum-based Printed Circuit Boards use an Aluminum alloy as a base material for the PCB i.e. the dielectric layer is sandwiched between the Aluminum alloy and circuit layer. The Aluminum alloy is a composite of magnesium and silumin (Al-Mg-Si).Aluminum based PCBs are part of the Metal Core PCB family and deliver excellent thermal conductivity and insulation.Key Advantages of Aluminum Based PCBs...read more

What is Glass Transition Temperature (Tg)?

PCB Basics

Editorial Team - PCB Directory

Jul 13, 2019

Tg or the glass transition temperature is the temperature at which the base material of a PCB starts to transform from a brittle/rigid form factor to a soft, elastic one. The Tg value of a printed circuit board usually depends on the substrate used. This is one of the factors that you must consider when selecting the substrate materials for your PCB. You should make sure that the temperature where...read more

What is Loss Tangent?

PCB Basics

Editorial Team - PCB Directory

Jul 13, 2019

In PCBs, Loss tangent (tan (δ)) is the measure of signal loss due to the inherent dissipation of electromagnetic energy in the substrate of the printed circuit board. It is a dimensionless quantity and generally referred to: Loss Factor, Tan δ, Dissipation factor and Loss angle.All PCB materials have both conduction losses and dielectric losses. The conduction losses are resistive and ...read more

What are Composite Epoxy Materials (CEMs)?

PCB Substrates

Editorial Team - PCB Directory

Jul 12, 2019

Composite epoxy materials (CEMs) are made by combining two or more materials having different chemical and physical properties to achieve the desired substrate material with unique properties and characteristics. Epoxy synthetic resin is used to combine materials. It acts as a binding agent to hold the materials together. It also transfers the thermal stress between the materials and protects them...read more

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