Tony Lentz

Tony Lentz has submitted responses to the following questions.

Tin Whiskers and Vapor Phase Reflow
The risk of tin whiskers is typically greatest with electroplated pure tin deposits, which could be used on component leads. ...

Solder Alloy Investigation
XRF can be used to identify the major constituents of an alloy without damaging the solder joints. The solder could ...

Solder Paste Print Test Boards
When changing over a line for a new PCBA, it is best to use the real PCBs, stencil, and printer ...

Full Aqueous Clean or Local Spot Clean
As you mentioned, cleaning can be done manually in the rework area or fully clean the PCBA in a washing ...

Solder Paste Stencil Inactivity
Solder paste can be left undisturbed on the stencil for 1-4 hours and remain printable. The actual length of time ...

How To Remove Oxidation On SMT Components
Using a solder dipping or dragging process using an aggressive flux would help to restore solderability to the component leads. ...

Solder Paste Print in Volcano Shape
The cone or volcano shape after print is normal for some solder pastes. The paste is stretched during separation of ...

Flux Residue During Pin-in-Paste
To my knowledge there is no standard practice for pin in paste reflow. It depends upon the board design, components, ...

Solder Joint Blow Holes
It may be possible that the ENIG plating process trapped moisture or process chemistries in the through holes. During wave ...

Matte Black Solder Mask Defects
During the solder mask application process, the solder mask is typically screen printed onto the circuit board. This is followed ...

Oxidation of Solder Balls During Secondary Reflow
If you are talking about solder spheres on BGA components, then oxidation can and will occur to the metal surfaces ...

Tented Via Options and Tradeoffs
Open via holes in the thermal pad will of course allow wicking of solder to the bottom side of the ...

SOT (Small Outline Transistor) Body Cracks
Cracking in component bodies usually occurs due to stresses that are applied to the components during the SMT process. With ...

Pin-in-Paste Hole Stencil Printing
The first question to consider is what is the criteria for hole fill? Are you trying to achieve 100% fill ...

Challenge Wetting Solder to Brass Pins
You could run the leads through a tinning operation prior to through-hole soldering. This would cover the brass with solder ...

Seeking Advise for a Solder Reflow Recipe
The heavy copper plane (0.040") will certainly act as a heat sink resulting in lower measured reflow temperatures than what ...

Step Stencil Squeegee Angle
We recommend using the standard 60 degree squeegee blade angle for most applications. It is beneficial to slow the print ...

Hand Sanitizer Contamination
Quaternary ammonium compounds are usually made as halide salts (e.g. chloride salts). Particles that land on circuit boards will deposit ...

Wet Based Stencil Cleaning or Dry Wipe Stencil Cleaning
Underside stencil cleaning should be performed based on the solder paste supplier's recommendations. We recommend using a 3 part cleaning ...

How to Remove Oxidization from SMT Component Leads?
Oxides can be removed from SMT component leads using common soldering fluxes. A dip flux could be used in the ...

Causes of Annular Ring Dewetting
Annular ring de-wetting could be caused by a number of things. There could be contamination in the holes left over ...

How To Measure Solder Paste Rolling Diameter
The rolling diameter of the solder paste affects the fill of the stencil apertures and therefore the printed solder paste ...

Critical Part Fixture During Reflow
Fixtures are occasionally used to hold components during reflow. The fixture itself will act as a heat sink which changes ...

Water Wash vs. No-clean
It is always safer / more reliable to wash off the flux residues along with other board contaminates. This exposes ...

Solder Contamination Sources
The most likely sources of contamination in a solder bath (wave or selective) are metals from the circuit boards and/or ...

Maximum Allowable Time Prior to Washing When Using Water Soluble Paste
The maximum allowable time for washing a water soluble solder paste depends upon the solder paste itself. The manufacturer can ...

EMI Shield Reflow Soldering Techniques
Tooling fixtures can be used for this application. The reflow profile will have to be modified to compensate for the ...

Components Falling Off During Reflow
Excessive solder paste volume on the 2nd side (top) should not lead to components falling off of the 1st side ...

Competing Reflow Oven Zones
It is best to keep the oven temperature settings less than 30 degrees C from one zone to the next. ...

Exposed Copper Defect
IPC-A-610F section 5.2.1 Soldering anomalies - Exposed basis metal states that exposed base metal is acceptable for Class 1, 2, ...

Pad Missing ENIG Plating
"Skipped" or missed pads can occur in the ENIG plating process. Normally it is caused by an issue with catalyzation ...

Tarnished OSP Circuit Boards
OSP is a permeable coating which slows tarnishing of the underlying copper. Tarnish is usually caused by air exposure over ...

Adding Chlorine to a DI (Deionization) Water System
Bacteria growth in DI water storage tanks is a common problem. It is sometimes necessary to clean out the bacteria ...

Reflow Profile for Mixed Lead-Free and Leaded
In most cases the solder paste determines the reflow profile used. One exception to this may be the lead-free hot ...

Application Using No-Clean and Water Soluble Fluxes
You could use a water soluble wire solder for subsequent processes but the flux residue must be washed off after ...

OA Flux Turning Blue
Many ingredients used in organic acid fluxes (OA) combine with copper to form blue colored compounds. It is very likely ...

Reflow Oven - 5 Zone or 8 Zone
I recommend using an 8 zone oven for lead free reflow profiles. A 5 zone oven will typically allow for ...

Insufficient Barrel Fill on Through-hole Components
Barrel fill is affected by several things including: the solder alloy and the composition of the alloy, the preheat temperature ...

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 Splashing 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 the ...

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 "cleanroom" area. The size of the airborne particles ...

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 ...