John Vivari

John Vivari has submitted responses to the following questions.

Solder Paste Past Shelf Life
Shelf life typically defines the warranty limit for a solder paste. Many remain fully functional beyond the published shelf life. ...

A Generic Reflow Profile
Based on the board diversity detailed in the question, it is unlikely the submitter can use just one profile for ...

Soldering Multilayer Ceramic Chip Capacitors
Ideally, solder both sides at the same time by heating the entire component uniformly to avoid unnecessary thermal stress. One ...

Is Rework Unacceptable?
Without knowing if there is a particular reason for your customer's position, it is impossible to say if it is ...

Delay Before Washing Water Soluble Flux
Not all water soluble fluxes are equally safe when left in place for extended periods before cleaning. You should contact ...

Solder Paste Mixing After Storage
If solder paste has no flux separation, is should be ok to use without any mixing. If solder paste has ...

Application of Flux for Hand Soldering
You will achieve the most precise control with paste flux. Paste fluxes come in a variety of formulas optimized for ...

Need for Reflow Profiles
Many companies can be very successful using 3 or 4 profiles and grouping boards by size or mass. Where things ...

BGA Rework Flux Recommendation
BGA rework should be done with rework flux paste, which is designed to stay active and will remain in place ...

Solder Fillet Peaks
Solder spikes are usually a function of flux performance and/or joint temperature dynamic. If the flux is fully expended, oxide ...

Flux Residue Visible After 3 Months
It is true that most resins and rosins used in no-clean flux will turn cloudy and white when they get ...

Hand Soldering Alternative
The answer depends on why the hand soldering process takes so long. If the wire is stranded and the operators ...

SMT Component Shift
The question does not specify if all components are shifting or a particular subset. Components with a high mass to ...

Screen Print Shelf Life
The answer is both solder paste and environment specific. The rate at which thesolder pastedries out due to flux evaporation ...

Recommended Rework Dwell Times
From the question, the subject seems to be for a hot air rework station where there is temperature control. If ...

Idle Time Between Soldering and Cleaning
As a rule, the sooner after reflow you clean a PCB, the easier it is to remove flux and other ...

Solder to a thin flexible circuit
There is no one answer for every application. If the flex circuit remains sufficiently planar during processing, including reflow, a ...

Oxidation on pads causes poor solder joints
Clean metal surfacesare chemically unstable. They reach a stable statethrough bonding of free oxygen, from the air, to unused bonding ...

Stencil Aperture changes due to board finish?
This will depend on your solder paste and inspection criteria. Some solder pastes do not wet out to the corners ...

IR Reflow Issue
The black body of the part is a very good absorber of IR radiation. If you put a thermocouple on ...

PCB Cleaning
Not in my experience. Wiping the board forces paste into vias along with solvent and whatever else was on the ...

Lead Free Flux
Fluxes do not contain metals, such as lead, so all fluxes are lead free. Your question must be asking about ...

Clean water soluble flux
There exist a wide variety of water soluble flux chemistries and they do not all leave the same residue. My ...