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Karthik Vijay
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Technical Manager - Europe
Indium Corp.
Currently with Indium Corporation and responsible for technology programs and technical support for customers in Europe. Over 15 yrs experience in SMT, Power, Thermal & Semiconductor Applications. Masters Degree in Industrial Engg, State University of New York-Binghamton.

Karthik Vijay has submitted responses to the following questions.
What is Causing Solder Joint Cracking?
There are many design and application variables that can cause the solder joint to fail in operation. From a soldering ...
Cleanliness Standards for Electronic Components
From a humidity standpoint, the dewing test is a difficult one. As a materials company who supplies solder paste to ...
Overlap Solder Joint Failures
For automated assembly, an investment in fixturing would be needed to hold multiple sets of the 2 strips during heating ...
Tiny Solder Balls After Reflow
Have you tried reflowing a fresh bare board and checking for solder balls? If you see solder balls, then the ...
Substance Under Zero Clearance Parts
The zero/low standoff is preventing complate solvent volatalization that is in turn preventing the rosin residue to form an inert ...
Very Low Temp PCBs
100In (melts at 157 deg C) has historically been used for space applications and for cryogenic sealing where temperatures are ...
Pin-in-Paste Problems
With a paste solution, you can modify the stencil apertures to prevent the pin from dragging paste and reduce the ...
Silver Solder for Audio Circuits
What is the composition of the silver solder? What are the reliability requirements? There are lower-temp eutectic alloys (cheaper or ...
Solder Balls During Hand Soldering
Moisture entrapped in the PCB and/or components could be the reason for solder balling. 1 variable at a time - ...
Cold Solder Joints on 0603 Components
Assuming that the reflow profile was long and hot enough to melt the solder, what you are seeing is most ...
Use of Nitrogen for Hand Soldering
The purpose of a flux is to reduce oxide and fluxless soldering could involve (a) ultrasonic soldering to scrub the ...
Is Rework Unacceptable?
Rework unfortunately is a necessary evil. However rework can be minimized in the following ways. * An optimized print process ...
Flux Recommendation for BGA Rework
BGA rework can involve tacky flux or solder paste. Solder paste is used to compensate for BGA ball non-coplanarity. Flux ...
Stencil Issue with PLCC Component
Addition of a solder preform (which is basically a brick of solder of the same alloy as paste) to add ...
Application of Flux for Hand Soldering
Flux-cored solder wire is one way to avoid manual flux application and prevent excessive flux. Typically the flux content could ...
Lead-Free Profile Using Leaded Paste
When using a Pb-free profile for Pb-free BGAs & Sn/Pb paste, the good thing is that the Pb-free BGA balls ...
Post Print Inspection Issue
Not a whole lot can be done without cleaning the misprint on the 2nd side; and for cleaning, an automated ...
Guidelines for Pin-in-Paste
Many applications, using a solder preform in conjunction with solder paste is an easy fix to achieve 100% hole-fill. These ...
Pros and Cons of Cleaning No-clean
No-clean pastes have been used for the last 20+ years and have had a very good track record 70-75% of ...
Flux Residue Causing Test Issues
Not sure what incomplete readings mean. Are you referring to an ICT issue due to flux residue on the connector ...
Adding Weights to Small BGA's During Reflow
The reasons for opens with small light BGAs may be due to: a. Insufficient flux activity: For the smaller apertures ...
Humidity Inside Our Screen Printer
The solder paste needs to be robust enough to withstand fluctuations in humidity without drying out / slumping. Increasing humidity ...
BGA Rework Flux Recommendation
A flux with a good oxidation barrier (that protects molten solder from oxidizing for as long as possible) will do ...
Organic Flux Residue Concerns
No-clean rosin-based rework fluxes should not need any cleaning as long as the flux gets completely activated. Typically a flux ...
Soldering lead-free component, with tin-lead solder
For a Pb-free ball & Sn-Pb paste, from a reliability standpoint - it is better to completely melt the Pb-free ...
Which to Use - Rosin Flux or Water Soluble?
Rosin-based fluxes contain rosin and in most cases pass no-clean requirements. No-Clean flux-residues are benign, inert, non-hygroscopic and does not ...
Cause of Unusual Contamination?
Solder seems to have been trapped in the vias. During subsequent reflow, the solder inside the via will melt and ...
Hand Soldering Alternative
Hand soldering is manual, time-consuming and is not capable of delivering the same solder volume from pin-to-pin. A solder preform ...
Tacky Flux Residue Problem
Rework flux not activating completely / Improper rework heating cycles can affect the robustness of the solder joint and cause ...
Solder Joint Rework Question
Apart from using a solder iron and solder wire, a solder preform can be used to rework the through-hole joint. ...
Low Silver Soldering Problems
Low-Ag in SAC alloys such as SAC105 in BGA balls are very good for drop performance and are primarily used ...
How to predict possible intermetallics
Growth of intermetallics is a function of the temperature and the time for which the solder is molten - the ...
Nickel Barrier Thickness Requirement
For nickel to be an effective diffusion barrier, the thickness of nickel is typically at 150 micro-inches. ...
Type III vs. Type IV solder paste
Typically as the stencil aperture / pad dimension reduces, a smaller solder particle size may be needed. Rules of thumb ...
Hand Soldering vs. Selective Wave for small LCD
individual preforms or integrated preforms to: solder all pins in1 shot eliminate manual soldering & solder iron (just use heat ...
Define Blow Holes
Blow holes are typically caused by moisture or an organic material trapped in the bare PCB that volatilizes rapidly when ...
Opens on BGA solder joints after reflow soldering
Contaminants on the BGA balls (left behind on the balls due to due to improper cleaning during the BGA mfg ...
Adhesive for sensor attachment
NF-260 is a reworkable no-flow underfill which could do the job. See Indium Corporations rework video. A no-flow underfill is ...
Stencil Aperture changes due to board finish?
Typically there is no change in stencil apertures when changing from ENIG to OSP PCB surface finish Flux activity and ...
Removal and rework epoxy attached components
There are reworkable epoxy fluxes / no-flow underfills that are designed to come off during rework and not damage PCB ...
PCB Cleaning
Not a whole lot. A manual wipe could damage the solder mask. As long as the cleaner parameters are optimized, ...
Affects of Ultrasonic Cleaning
If the frequency of the crystal matches the frequency of the ultrasound, then there is resonance and the component can ...
Through Hole Soldering on 24 Layer Board
I agree that achieving the right amount of preheat is important, but using a solder preform rather than solder wire ...