Dr. Brian Toleno

Dr. Brian Toleno has submitted responses to the following questions.

Alternatives to Conformal Coating
There are a number of UV/moisture dual cure and UV/heatdual cure materials that can be applied directly (jetted or needle) ...

Rework of Underfilled Array Packages
In previous years reworkable underfill systems tended to be very soft (even at room temperature),low Tg (glass transition) type materials ...

Tombstoning Dilemma
If you review the articles the two main, statistically significant factors are: 1. Pad Design and 2. Materials. There are ...

Conformal Coating & Humidity
Conformal coating is one method of protecting a PCB from an end use environment. Conformal coatings are a thin layer ...

Adhesive for sensor attachment
There are a number of adhesives that can be used to provide support to the sensor. You want to make ...

Oxidation on pads causes poor solder joints
What pad surface finish are you using? Why do you suspect surface oxidation is the reason for BGA failure? Metal ...

IR Reflow Issue
Without having more detail it is difficult to diagnose the actual issue. With cracked or failed solder joints you would ...

Reflow for leaded and lead-free assemblies
Developing a unique profile for tin-lead and lead-free assemblies is critical. Tin-lead solder (e.g. Sn63/Pb37) melts at 183C whereas the ...

Good epoxy or cement for bonding BGA packages to PCB
Capillary flow underfills are the best solution for CSP and BGA support in handheld products like cell phones, PDAs and ...

SMT adhesive problems after wave solder process
There are several common reasons for surface mount adhesives not to provide adequate adhesion during the reflow process. The best ...

Baking lead-free and lead PCB's before assembly
With respect to baking boards or substrates, typically the reason to do this is to remove absorbed moisture from the ...

Reflow parameters for lead-free BGA
Manufacturing with a mixed metal system is, unfortunately, becoming more common as high volume manufacturers move to Pb-free. This in ...

Oxidation on plated through holes
Silver can indeed tarnish when exposed to different atmospheric contaminates. The most common forms are sulfides which readily form tarnish ...

Proper method to bake PCB's
With respect to baking boards or substrates, typically the reason to do this is to remove absorbed moisture from the ...

Tin lead soldering of lead free components
What you have run up against is the unfortunate consequence of the transition period from Sn-Pb to Pb-free. In the ...

Cleaning an assembled board with IPA
Different no-clean solder pastes produce different residues with different characteristics. You are taking the right approach in checking the compatibility. ...

Wave Soldering creating blowhole problems
The most common causes of blowholes is expansion of a liquid or gas at high temperatures escaping through the solder, ...

Lead free BGA's and HASL
One of many issues raised by the transition to Pb-free manufacturing is mixed metal assembly ( http://www.meecc.com/pres2006/Track%203%20-%20Poole.pdf). For a situation ...

Help debugging wetting problems
There are four things to look at: (1) Component (2) Solder Paste (3) Profile and (4) Board Finish. Since it ...

Coating to stop tin whisker growth?
Since the announcement of the EU legislation on RoHS and the move of electronics manufactures to a Pb-free process there ...

Studies showing the effects of PCB finish on manufacturability
I am not aware of any specific published studies regarding HASL versus other finishes for fine pitch applications. The reason ...

Is it possible to run Pb-Free reflow without nitrogen?
It is certainly possible to manufacture and reflow surface mount assemblies using Pb-free soldering materials without using nitrogen. As long ...

RoHS existing products vs. new products
Products that will be sold in the EU as of July 1, 2006 need to be compliant with the RoHS ...

Can PCB's designed for Sn/Pb be used in a Pb free assembly?
In many cases the initial Pb free builds of existing products were done using the then current board materials and ...

Advise and suggestions for assembly using 01005 capacitors.
In a word: precision. You need to make sure that your stencil can deposit the correct volume of paste. This ...

Lead-free solder pastes drop-in replacements?
The concept of a drop-in replacement has been one of the drivers for the industries solder paste development programs. The ...