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Eric Bastow
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Senior Technical Support Engineer
Indium Corporation
Eric is an SMTA-certified process engineer (CSMTPE) and has earned his Six Sigma Green Belt from the Thayer School of Engineering at Dartmouth College. He is also a certified IPC-A-600 and 610D Specialist. He has an associate's degree in Engineering Science from the State University of New York and has authored several technical papers and articles.

Eric Bastow has submitted responses to the following questions.
What Caused SMT Pads to Oxidize After Reflow
If the gold was too thin and, therefore, porous, it is possible that the nickel layer may have oxidized. Depending ...
No-Clean Flux Residue After Selective Soldering
We have to go back to the SIR and ECM of the flux residue. Liquid/wave fluxes are tested pattern up ...
Specific Solder To Control Dendritic Growth
The answer is quite often linked to economics. If the CM buys all or a large amount of paste from ...
Recommended Solder Paste Aperture Configuration
Unfortunately there is not an industry standard for these smaller components at this time. Several big name users have developed ...
BGA Placement Paste or Only Flux
The biggest risk for using flux only would be the increased propensity for open joints. If the BGA warps during ...
Solder Paste Thickness Measurements
Ideally every paste deposit should be measured regardless of the size of the size of the board. If there is ...
Reliability Concerns When Converting to Lead-free
I am not familiar with the reliability requirements of the "industrial market". ...
Old Components and Blow Holes
The best way to identify the cause is with a cross section of the circuit board joints exhibiting the problem. ...
What Is Causing Connectors to Bow?
Either way the connector is warping as it goes through the oven. But when the solder is present it is ...
How To Reduce Solder Joint Voids in QFN Components
There are whole papers on the topic. At a minimum, usually some sort of window pane is used for the ...
Using Solder Paste Beyond the Expiration Date
It is unlikely that the issue is related to the fact that the paste has expired. It is more likely ...
Concerns With Silver Finish Component Leads
Ag does stiffen Sn containing solders through the formation of AgSn intermetallics that act like scaffolding in the solder joint. ...
Selective Solder System Purchased At Auction
The standard practice would be to flush pure Sn through the system until the Pb drops below an acceptable limit. ...
Solder Splashes During Wave Soldering
Potentially insufficient preheat not drying the flux before the wave. More common with a VOC-Free flux. If not the flux, ...
Problems With Large Voids
Use the hottest profile that the assembly can tolerate. Hot profiles typically improve wetting and better wetting reduces voiding. Use ...
Requirement for Toe Fillets
I would suggest contacting IPC directly for clarification. ...
Solder Paste Mixing
We have no recommended technique for verifying machine paste mixing as we do not recommend the use of paste mixing ...
Initial Screen Print Test Board
It is not a bad idea. It will depend much on the quality of the solder paste. Some pastes are ...
Reusing recovered solder paste
"Reusing" paste is a common practice. When removing used paste from the stencil always put it in its own unique ...
Dust contamination after selective soldering
I would first verify that the dust is indeed metallic. It could also be flux residue or PCB dust that ...
Questions Regarding Underfill Options
I would refer you the underfill manufacturer for their recommendations. ...
Stencil Pattern for Thermal Pads on QFNs
Although, a little dated, the IPC has published a document from which some basic recommendations can be gleaned. IPC-7093 - Design ...
Components Falling Off During Wave Soldering
It's possible that the lacquer could interfere with the glue's adhesion to the board surface. I suggest contacting the glue ...
Mixed Process Solder Joint Appearance, Smooth or Grainy?
It is hard to answer because such words are relative and the joint appearance can also be impacted by process ...
Environment Impact on Assembly, Printing and Reflow
I am not aware of any SMT houses that are that concerned about the air quality in the factory. If ...
Soldering Components with Silver Pads
One option would be to avoid the use of a Sn based paste and switch to an indium based paste. ...
0201 Pick & Place Nozzle Plugging
Perhaps adjusting the Z height of the placement would be the easiest thing to do. Set it little bit higher ...
BGA Solder Ball Shelf Life
Unfortunately solder suppliers have no control how their products are handled once they leave the factory. Also, the products are ...
Selective Soldering Frame Causing Cold Solder Joints
It is possible given that the frame can act as a heat sink and "wick" heat away from the areas ...
Viscosity of Solder Paste Before Printing
That is a really tough question. Static viscosity tests like Malcom and Brookfield do not wholly predict how a solder ...
QFN Test Failures Caused by Flux
Yes. If the flux was not adequately activated there could be some leakage current. ...
Can a Few Contaminated Joints Cause an Assembly to Fail RoHS Compliance?
For better or worse it does not work that way. Every solder joint on a given assembly must be RoHS ...
Bottom Terminated Components and Vias
Amkor has an application note on the topic. There are other papers on the topic as well and how it ...
Estimating Failure Rate During Rework
Reworking a solder joint typically increases the thickness of the intermetallic layer. Thickening the intermetallic layer can translate to a ...
LED Component Shift During Reflow
Depending on the amount of solder on the pad, the LED can become buoyant and "float around" on the surface ...
Copper Dissolution Rate
The testing is done by dipping a metal cylinder into an infinite amount of solder bath (no significant composition change). ...
QFN Open Solder Joints
There are two possible causes:   It could be that the open is the result of insufficient solder paste. Make ...
Stencil Cleaning Frequency
Assuming that you are talking about the frequency of an under stencil wipe, there is no standard. It is very ...
Gold Plating and Embrittlement
It depends on what the solder alloy is and how much solder is applied. But in sufficient amounts gold is ...