Questions & Answers on Solder

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Solder

Editorial Team - PCB Directory

Jan 22, 2021

Solder Flux is a chemical cleaning agent used when soldering electronic components onto printed circuit boards. It is used in both manual hand-soldering as well as the different automated soldering processes used by PCB contract manufacturers.Printed Circuit boards usually have copper traces which can oxidize when exposed to air or get contaminated while handling the board. This can prevent the fo...read more

What is a Cold Solder Joint?

Solder

Editorial Team - PCB Directory

Jan 11, 2021

A Cold Solder Joint occurs when solder fails to melt entirely to form a proper joint. A cold solder joint or an improperly formed joint can be the trigger for reliability problems of an electronic assembly. Cold solder joints increase the electrical resistance of the solder joints, and hence reduce the reliability of the solder joints.There are a number of factors that can cause cold solder joints...read more

What is Low-temperature Solder Paste?

Solder

Editorial Team - PCB Directory

Jan 17, 2021

One of the most important parameters when selecting a solder paste is its melting temperature. A Low-temperature solder paste can be broadly classified as one that melts at a temperature below 180° C.Low temperature soldering is required in a number of cases specially when dealing with heat-sensitive devices, parts with significant differences in their coefficients of thermal expansion, compon...read more

What is No-Clean Solder Paste?

Solder

Editorial Team - PCB Directory

Jan 17, 2021

No-Clean Solder Paste is a paste that doesn’t require cleaning after the solder reflow process. After the reflow process, most solder pastes leave behind some flux/residue on the board. This can cause issues if the residue is conductive or corrosive. The reside/flux left behind by No-Clean Solder Paste is non-conductive, non-corrosive and won't interfere with the electrical conductivity ...read more

What is a Flux Remover?

Editorial Team - PCB Directory

May 18, 2021

A Flux Remover is a chemical solvent that is used to clean or remove flux residue, white residue, and other impurities from the surface of a PCB. Typically, the isopropyl alcohol or water-based solvents are used as flux removers.Flux residue is usually found on the Printed Circuit Board after the soldering process, during desoldering, when repairing the PCB or in the rework process. This residue n...read more

What are Mid-Chip Solder Balls?

Editorial Team - PCB Directory

May 18, 2021

Mid-Chip Solder Balls occur when some solder paste detaches from the bulk deposits on the pads and gets stuck under the component. When this cools, it looks like a ball of solder sticking out from under the component. The mid-chip balling defect usually occurs in surface mount / chip components like resistors, inductors and capacitors. This defect reduces the aesthetics of the board more than reli...read more

Viscosity of Solder Paste

Solder

Editorial Team - PCB Directory

May 22, 2021

Solder paste is a complex viscous fluid that is non-newtonian in nature. This means that the viscosity is not constant and varies based on the shear stress applied to it. The viscosity of a fluid is defined by its resistance to flow. In the case of solder paste, the viscosity is inversely proportional to the amount of shear stress applied to it. If the applied stress increases, the viscosity of so...read more

What is Halogen-Free Solder Paste?

Solder

Editorial Team - PCB Directory

Jan 17, 2021

Halogen-Free Solder Paste as the name suggests is a solder paste that does not contain Halogen. Fundamentally, halogens in solder paste refer to chlorine and bromine. Chlorine, is found in circuit boards, and is primarily in the form of residual materials left over from production of non-brominated epoxy resins used in board assembly. Bromine in electronics is usually added to organic materials su...read more

What are Lifted Pads on Printed Circuit Boards?

Editorial Team - PCB Directory

May 22, 2021

A lifted pad on a printed circuit board is a pad that detached from the surface of a PCB. This results in an improper connection to the lead or component causing the PCB board to malfunction or not work. This defect is usually found on single-side PCBs that use a thin copper layer with no through-hole plating. It is caused by excess heat and/or excessive force on the solder joint. The lifted pad i...read more

What is Slump in Solder Paste?

Solder

Editorial Team - PCB Directory

May 22, 2021

Solder Paste Slump is the tendency to paste to spread after application on the PCB. Theoretically, once the paste is deposited on the circuit board, it should remain in the same state until a component is placed on it. However, in the real world, the solder paste tends to spread. This can result in various PCB defects like solder bridges between two adjacent pads which can create a short circuit. ...read more

What is Response to Pause in Solder Paste?

Solder

Editorial Team - PCB Directory

May 22, 2021

During the PCB Assembly process, SMT lines often need to be stopped to replenish components in the pick and place machines or fix a faulty machine. During this pause, the solder paste being used can stiffen. The stiffening causes inconsistencies in the volume of the solder being deposited on the board. Large volume variations in solder during the printing process are not wanted and can lead to def...read more

What is Solder Paste Tack?

Solder

Editorial Team - PCB Directory

May 22, 2021

One of the most important properties of solder paste is its ‘Stickyness’ or Tack. The stickiness ensures that components placed on the solder paste can be held in position before the solder joint is made.This property is a measure of how long the solder paste can maintain its stickiness over time. It is important to know this as there can be significant time gaps between when the paste...read more

What is Peelable Solder Mask?

Editorial Team - PCB Directory

Feb 15, 2022

A Peelable solder mask is a type of solder mask that can be peeled off the surface of a printed circuit board. This type of solder mask is used to protect specific areas of a PCB during reflow soldering, wave soldering, or surface finish process. It is applied over the pads or plated through holes prior to the PCB assembly process and prevents the accumulation of excess solder on empty pads during...read more

What is Water-Soluble Solder Paste?

Solder

Editorial Team - PCB Directory

Jan 17, 2021

Water-Soluble Solder Paste as the name suggests is solder paste whose flux residue left after the solder reflow process can be dissolved or removed with water.The PCB assembly world now mostly uses no-clean solder, where flux residues can also be safely left on the board, without creating leakage current or corrosion issues. However, though the flux residue of no-clean solder paste is not conducti...read more

What is Wave Soldering?

Editorial Team - PCB Directory

Nov 13, 2021

Wave Soldering is the process of soldering through hole components onto a PCB by passing the exposed leads of the components placed on a board over a wave of molten solder. The solder wave flows under the PCB board and applies solder to the leads of components placed on the PCB board. It is primarily usedto solder thru hole components on printed circuit boards. It is not usually used to solder sur...read more

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