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Tony Lentz
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Field Applications
FCT Assembly
Tony has worked in the electronics industry since 1994. He worked as a process engineer at a circuit board manufacturer for 5 years. Since 1999, Tony has worked for FCT Companies as a laboratory manager, facility manager, and most recently a field application engineer. He has extensive experience doing research and development, quality control, and technical service with products used to manufacture and assemble printed circuit boards. He holds B.S. and M.B.S. degrees in Chemistry.

Tony Lentz has submitted responses to the following questions.
Channels To Reduce Voids in Large Pads
Voiding in large pads is caused by multiple factors. During reflow, the solder paste generates volatile gasses which become trapped ...
What Caused SMT Pads to Oxidize After Reflow
ENIG surface finish is typically resistant to oxidation from reflow, as compared to other surface finishes. Immersion silver, immersion tin ...
No-Clean Flux Residue After Selective Soldering
There is no industry standard that details how much flux residue can be left behind. The amount of no clean ...
Specific Solder To Control Dendritic Growth
It is normal for an end user or OEM to specify the IPC J-STD-004 classification for the flux used in ...
Solder Balling Prediction Formula
I am not aware of a mathematical formula to predict mid-chip beading on passive components. The stencil design can be ...
Solder Balling Splash After Reflow
Some solder pastes are prone to leaving solder balls under SMD components. This depends largely upon the amount of solder ...
Recommended Fiducial Shape
The HASL process tends to create thicker "bumps" of solder on small pads and thinner more flat deposits on large ...
What Is This Contamination?
The pictures are difficult to zoom into but it appears there is corrosion occurring. Is there a no clean flux ...
BGA Placement Paste or Only Flux
BGA's can be soldered using only gel/tacky flux. This process works well assuming there is enough solder volume in the ...
Solder Paste Thickness Measurements
In general, 30 measurements typically gives good statistical data for most parameters. Most in-line solder paste inspection systems can measure ...
Reliability Concerns When Converting to Lead-free
I believe that reliability of a solder joint really depends upon the application, the environment, and the stresses that the ...
Old Components and Blow Holes
Old components may lead to blow holes in wave soldering. As components age the oxide layer on the metal connectors ...
Solder Mask Thickness Tolerance
Solder mask thickness changes based on the location on the circuit board. The solder mask thickness over the laminate will ...
Using Solder Paste Beyond the Expiration Date
Solder paste flux and solder powder react slowly over time as the paste is stored. The by-products of those reactions ...
Concerns With Silver Finish Component Leads
Both silver and gold can cause embrittlement in 63Sn/37Pb solder joints. Normally, the concentration of silver or gold has to ...
Selective Solder System Purchased At Auction
The best option is to drain the leaded solder, clean out the machine and then perform a tin wash. Many ...
Out-gassing and Cleaning
I believe that vapor phase degreasing can be done with a vacuum purge afterwards. This would help to remove trace ...
Solder Splashes During Wave Soldering
Solder splashes during waver soldering are often caused by the application of excessive flux, and/or inadequate preheat. The volatile materials ...
Partially Visible or Hidden Solder Connections
A summary of section 4.18.3 in J-STD-001 states: The design cannot restrict the flow of solder. The visible portion of ...
Initial Screen Print Test Board
Yes it is a good idea to print 1 or two blank/scrap circuit boards before printing the first production board. ...
Reusing recovered solder paste
Normally solder paste suppliers do not recommend re-use of solder paste because performance degrades with use. If you wish to ...
Dust contamination after selective soldering
Dross dust can adhere to solder mask when the solder mask is softened through heating. The solder mask hardens as ...
Stencil Pattern for Thermal Pads on QFNs
We recommend reducing the total printed paste area to 50-60% of the ground pad based on the board copper layer ...
Mixed Process Solder Joint Appearance, Smooth or Grainy?
The tin/lead profile will not get hot enough to reflow a tin based lead free finish on the components.  The ...
Environment Impact on Assembly, Printing and Reflow
Particle count is usually used to indicate good housekeeping practices in the "clean room" area.  The size of the airborne ...
Soldering Components with Silver Pads
Solder paste is designed to dissolve some of the metal finish on both the component leads and the circuit board ...
BGA Solder Ball Shelf Life
The solder alloy itself should not change composition significantly over a period of several years. The main potential issue is ...
Selective Soldering Frame Causing Cold Solder Joints
The selective soldering frame could be contributing to cold solder joints in your wave solder process. Frames act as heat ...
Viscosity of Solder Paste Before Printing
The optimal viscosity of solder paste is normally determined by the solder paste manufacturer. There are occasions where an end ...
QFN Test Failures Caused by Flux
No clean flux residues have the potential to cause a capacitance issue. There are many conductive ingredients used in no ...
Can a Few Contaminated Joints Cause an Assembly to Fail RoHS Compliance?
The answer to this question depends upon the RoHS definition of a homogeneous material. "Homogeneous material" means one material of ...