Karl Seelig

Karl Seelig has submitted responses to the following questions.

Conformal Coating Bubbles
Based on the IPC-a-610 Rev G section 10.8.2. Per IPC-A-610 Rev G, section 10.8.2, one of the conformal coat defects ...

Oxidation of Solder Balls During Secondary Reflow
Regarding the question following question, "Can solder balls oxidize and create opens during a second reflow if the circuit board ...

Pin-in-Paste Hole Stencil Printing
Trying to fill the PTH with paste is typically the last thing you want to do. The reason I say ...

Point to Pint Soldering vs Drag Soldering
Drag soldering for though hole is difficult. Board design plays into the equation. If the board has high density ground ...

Wet Based Stencil Cleaning or Dry Wipe Stencil Cleaning
There are many ideas on this subject. From my experience as a onetime solder paste developer is the stencil cleaning ...

Adding Chlorine to a DI (Deionization) Water System
This is not recommended. You may as well just use tap water it would be safer. Most bactericides are chloride ...

Reflow Profile for Mixed Lead-Free and Leaded
Mixing leaded solder with lead-free components can be detrimental to the reliability of the solder. Regarding profile it depends on ...

Reliability Concerns When Converting to Lead-free
Please refer to my paper from 2001. Lead Contamination in Lead-Free Electronics Assembly ...

Using Solder Paste Beyond the Expiration Date
White residue from water-soluble paste is normally a corrosion product from the powder and the flux medium. It is a ...

Gold Plating and Embrittlement
The embrittlement in solder connections occurs when the weight percentage of gold to solder increase. The alloy of the solder ...

Solder Paste Viscosity
Before any expert can truly answer this question, several factors must be divulged. First, why are you measuring viscosity? What ...

Opens at BGA Component Corner Balls
This is a classic example of Solderability-related Head-in-Pillow (SR-HiP). There is usually not a 100% fix, however, the best way ...

Stencil Issue with PLCC Component
There are two issues happening here. Although you have a stencil aperture of 1:1, it does not mean you are ...

Source of Wave Solder Bridging
In wave soldering, any termination that will wet to the solder while being submerged has the ability to bridge. It's ...

Square vs. Round
AIM has conducted extensive printing tests on BGA's using a Kho Young volume measurement instrument. Square apertures repeatedly outperform round ...

Guidelines for Pin-in-Paste
In order to calculate the volume of solder paste needed, you will first have to calculate the volume of the ...

Solder Fillet Peaks
If the solder is flowing properly it is unlikely that it is caused by the temperature of the soldering iron. ...

Baking lead-free and lead PCB's before assembly
Why do you have to bake PCBs? Also what is the finish? Depending on the reason you more than likely ...

Tombstone problems
There are many ROHS components that have been causing soldering issues. Many are manufacturer specific. Tombstoning can be controlled by ...

Lead-free bar solder for wave soldering
There is not any testing that I am aware of comparing brands of lead free solder. However there are a ...

Reflow parameters for lead-free BGA
The profile should be according to the paste supplier's recommendations. You may want to run a hotter spike if you ...

Lead-free soldering problem
It sounds like "head in pillow." This is a situation where the solder paste doesn't fully wet the BGA ball. ...

Lead-Free Reflow Soldering
For most lead free reflow, 7 zones are required. This is not to say you cannot run with 5, but ...

Solder alloy function
Your question is very involved and can not be answered in a simple paragraph or even a book. However some ...

Proper method to bake PCB's
Why do you have to bake PCBs? Also what is the finish? Depending on the reason you more than likely ...

Copper Dissolution issue
Copper dissolution in wave is affected by several sources, first is the copper plate density on the board. This seems ...

Tin lead soldering of lead free components
This is a very common question. There are papers that have been published that show the lead/tin soldered SAC BGAs ...

Cleaning an assembled board with IPA
Cleaning no-clean is not normally recommended but there are times it is necessary. IPA is not a good cleaner. A ...

Wave Soldering creating blowhole
Is this lead free solder or tin/lead? In lead free it seems that blow holes or surface voiding is more ...

Need lead-free wire solder for hand soldering
First of all there should be proper ventilation so that the assembler should not smell the flux. Many fluxes contain ...

0201 capacitors creating process problem
What is the issue? Tomb stoning? Or not wetting? Tomb stoning can be profiled out to some extent with a ...

Hand soldering process for lead-free
Hand solder temperature is dependent on the density of the board. Typically a 750F iron tip is a good starting ...

Reflow of "high-lead" flip chip device
Soldering to high lead bumps can be a big problem. First how are the bumps formed? They could be heavily ...

Reflow soldering lead free components creates tombstones
Tomb stoning is a problem when going to lead free. Reflow profiles and component finishes will have the biggest impact ...

Lead free BGA's and HASL
It is possible to assemble Lead Free BGA with tin/lead HASL but, as mentioned in previous compatibility issues, this is ...

RoHS tantalum capacitors burning during functional test
Yes we have seen this type of issue before. These are very difficult to assemble in reflow depending on the ...

Studies showing the effects of PCB finish on manufacturability
Unfortunately I do not know of any manufacturing studies where defects were tracked between different board finishes. They all have ...

Lead-free transition using HAL lead-free boards
Reverse compatibility is not an issue. The HASL coating either SAC or SN100C will work fine with a tin lead ...

Do we have to process a 2 side SMT boards within 24 hours of breaking the seal on the packaging?
Immersion silver board finishes are very susceptible atmospheric reaction but not normally form oxygen. Sulfur is the killer of immersion ...

De-wetting problems
Dewetting on specific areas of the board can be from several sources. Dewetting typically is caused by a solderability issue ...

Can we pour left over paste into the solder pot?
Adding solder paste to a wave pot can be a messy practice. The flux in paste is approximately 50% by ...

Epoxy replacement for solder
Conductive epoxies where going to revolutionize the electronic assembly industries in the late 70's when they were first introduced to ...

Pre-wash boards prior to conformal coating
Conformal coatings have to be tested against the particular flux that is on the board. Typically a low residue wave ...

Concerned about "tin pest"
Tin pest is typical an issue only with high purity tin or inoculated samples. There have been test run by ...

Preferred PCB finish between ENIG and immersion silver?
Both finishes have a plus and minus. ENIG has a history already, stores very well and in general works well ...

BGA component re-balled with lead free spheres
First is the Sn/Pb BGA going to be attached with Sn/Pb on to a lead free finished board such as ...

What is the best method to select a spray fluxer?
Not all spray fluxers are created equally. First of all make sure the spray fluxer has materials of constriction compatible ...