Greg York

Greg York has submitted responses to the following questions.

Full Aqueous Clean or Local Spot Clean
I would strongly recommend full cleaning through an aqueous cleaning system preferably with a Proprietary cleaner to ensure proper cleaning ...

Solder Paste Print in Volcano Shape
Normally non-contact print. Check there is no gap between board and stencil and that you have good solid support under ...

Design Specs for Selective Soldering
In an ideal world to keep the Selective area to be soldered close together so the jet and nozzle isn’t ...

Coils Rotated After Reflow
Is this being dragged round by internal baffles/curtains as its quite large? ...

Solder Joint Blow Holes
It is possible and been seen before, due to the unevenness of the HASL it was enough to let the ...

Step Stencil Squeegee Angle
Angle of squeegee for stepped is exactly the same as normal, more important is not to over pressurize the squeegee ...

Wet Based Stencil Cleaning or Dry Wipe Stencil Cleaning
I would only recommend wet clean, then vac, then Dry. Using a 50gsm material not 68gsm. Seen too many Dry ...

Solder Contamination Sources
We see generally the following while analysing solder Copper from HASL Solder process running too high will push copper levels ...

Solder Balling Prediction Formula
Mid Chip Solder Beading is a problem caused by a few Technical issues and the main cause is when the ...

Selective Soldering Frame Causing Cold Solder Joints
Ensure the Solder pot is heated to at least 275C so the Selective pallet is suitably warmed to allow heat ...

What Is Causing Connectors to Bow?
Have seen this a number of times recently with all kinds of Connectors including SO-DIMM ones so pretty fine, so ...

BGA Component Grounding Problem
his maybe useful especially if you are using 0.004" thick stencils. I have seen (last six months) many issues of ...

Insufficient Barrel Fill on Through-hole Components
Ensure sufficient flux wicking. Ensure sufficient top side preheat BUT not too hot so as to burn off all the ...

Pad Missing ENIG Plating
OSP should be OK as long as the Copper is precleaned and not too thick over the Gold. ...

Tarnished OSP Circuit Boards
Without more information it's hard to determine, but OSP is a good finish if the Copper is pre cleaned correctly ...

Application Using No-Clean and Water Soluble Fluxes
Wouldn't be advisable as the No Clean flux residue stands a very good chance of going white when it comes ...

What is Causing Solder Joint Cracking?
From the Picture it looks like there could be some blackening around the joint are you sure this hasn't Electromigrated ...

Dross Particles Sticking to PCBs
It sounds like you have Undercured Solder Resist causing the surface of the resist to become tacky and not allowing ...

What's Causing Cloudy Conformal Coating
It's possible it could be contamination in the sub surface of the Solder resist and conformal coating this then gives ...

Reflow Oven - 5 Zone or 8 Zone
As long as you profile correctly it shouldn't really matter as we have many users, varied in size and complexities ...

Solution for Grape Effect
Flux has exhausted is most likely the issue, try an alternative Paste or ask the Paste manufacturer to increase the ...

Method for cleaning boards after misprint
You must not wipe the Misprinted board, instead, immerse the whole PCB in a Solvent cleaner and we use compressed ...

Cleaning Under Low Clearance Components
Mostly, they are correct although there are newer Water Soluble pastes available which give a much longer cleaning window and ...

Specific Solder To Control Dendritic Growth
No its not unusual to find this specified to CEMS but what is unusual is that the fault has been ...

Recovering Solder from Dross
The main concern is not effectively dedrossing out the contamination such as Copper, Lead, Gold, Nikel and other elements that ...

What Is This Contamination?
Looks likely you have some corrosive residue left in the via and leaching out, causing the corrosion and subsequent failure. ...

Old Components and Blow Holes
To be honest not normally as there should be nothing on the components to attract moisture in the first place. ...

Cause of Unusual Contamination?
I would agree with the uniform wetting and sizes being from solder powder and probably from poorly cleaned screens spreading ...

Using Solder Paste Beyond the Expiration Date
Without an image of the problem it is very hard to say, never a good idea to use out of ...

Solder Splashing During Wave Soldering
Without further information it's hard to say but could be flux left on the PCB while going through the wave ...

Tombstone problems
We have achieved second side reflow using SAC305 Paste but this is fairly hit and miss and subject to pad ...

Best method to clean 'no-clean' solder paste
Unfortunately we find the only way to remove Misprints effectively is by using solvents or suitable Semi Aqueous products be ...

Reusing recovered solder paste
This day and age and usability of Paste you shouldn't be wasting much at all. I certainly wouldn't reuse any ...

Dust contamination after selective soldering
I would try to add additional Germanium as this may have depleted or even Tin/P as this will treat the ...

Components Falling Off During Wave Soldering
If it's a Lacquer coating then it could be the old type rosin Lacquer which would liquefy around 82C causing ...

Mixed Process Solder Joint Appearance, Smooth or Grainy?
I would expect a smooth finish as the very thin plate of the RoHS components shouldn't effect the melting point ...

White Discoloration After Ultrasonic Cleaning
More than likely the Waxes as the Rosins will be normally very soluble portion of flux. The Paste manufacturers use ...

Flux Oozing from Insulated Wires
All comments above are noted, I would thin back your existing flux by 50% and check soldering. IF OK reduce ...

Lead-free Dross Removal
We recommend our customers use a Top up Bar called Tin/P this in turn mixes with the solder and while ...

Stencil Issue with PLCC Component
Unsure why they would initially look good but under testing they require more solder BUT if this is corrct then ...

Tough Hand Soldering Problem
Without more information its very hard to say, but with 100% humidity and chillers being blown onto the glass I ...

QFN Test Failures Caused by Flux
This is highly unlikely, but is possible never say never, especially if using an ROM1 Paste or even ROM0 Classification. ...

LED Component Shift During Reflow
Probably floating on too much flux or alloy. Try cross hatching pad. ...

Solder Paste Prep Before Use
Youshould really allow 6 to 8 hours for the paste to acclimatise naturally and nottry to force heat the paste ...

Tiny Solder Balls After Reflow
Have you checked you are not using the wrong under stencil wiping roll that is too thick for vacuum then ...

Exposed Copper Risk
I would suggest you purchase some solder mask touch up pens and simply touch in the areas of exposed Copper. ...

Concave Via Fillets Causing Problems
You could always try to reduce the dewetting causing the concave joints by speeding up the process just a little ...

Frequency of Checking Solder Paste Viscosity
It should not be necessary to check solder paste viscosity with the most modern formulations. Most will now last over ...

Solder Mask Ghosting
I know it's hard to believe but a very real problem that has been occurring for many years, we have ...

Cleaning Military Circuit Boards Contaminated with Sand
I would try a very weak Saponifier solutionbubbled through a cleaning tank to remove the sand and other residues. Thistechnique ...

BGA Joint Voids - Accept or Reject?
If this was mine I would reject as it doesn't appear to have reflowed correctly nor does it appear to ...

Double Sided Reflow for Micro BGA Components
If the PCB permits I would use normal SAC305 on one side then a Sn,Bi,Ag alloy that's reflows at 170C ...

A Generic Reflow Profile
No there is no justification for using one profile unless you really want to produce potential scrap PCB's. I usually ...

Epoxy Wicking up Wire Insulation
Heat-shrink sleeve would that work??? ...

Solder Paste Life on the Stencil
It is completely dependent on paste type, we have several types where you change half of it after four hours ...

Problems with Insufficient Barrel Fill
Comment: Check solder bathtime and temperature and ensure you use a flow accelerator to improve thesolders ability to flow well. ...

Problem with 'No Clean' Solder Flux Residue
Firstly determine if this is flux residue ornot. Try applying a small amount of flux to the TOP of a ...

Improve DPPM for Wave Soldering Using Nitrogen
Highly unlikely in fact no one to my knowledgehere in the UK use Nitrogen inerting anymore. I would also not ...

Rework for OSP Assemblies
I would use a slightly more active flux and clean off any residue remaining with a good cleaner. This should ...

Mixing Different SAC305 Solders
As long as the impurities are the same or less than your existing Alloy with the exceptions of Bi then ...

Solder Mask Mis-registration Issue
I would say there should be no tolerance to resistbleed onto BGA pads. Mostly because there are Plasticizers that are ...

Can Solder Joint Geometry Change Resistance?
Flux residues especially those from HASL PCB'scan cause this issue. Wash the bare PCB thoroughly then test the drainage. If ...

Gold Plated Hole Defects
So many answers are possible be it leaded or Lead free soldering BUT the one that may best fit is ...

Glued SMT Components Falling Off
It would be nice to know if the glue is still adhering to the resist on the board or if ...

Insufficient Plated Hole Fill with Electrolytic Capacitors
It's really difficult to suggest something without knowing how the other components are wicking on the PCB and the solderable ...

HASL vs. Immersion Gold
HASL will produce a much thicker deposit of solder to wet to BUT it can leave traces of Hydrobromic Acid ...

Wave Solder Pot Contaminated with Lead
Unfortunately the only thing you can do is bail out an amount of solder to bring you back under 0.1 ...

What is Causing Oxidation?
Couldnt be due to Nitric Acid residues used to plate the Silver onto the Copper in the first place being ...

Cold Solder Joints on 0603 Components
I would of thought it could of been more like you have sheared thinned the paste too much especially if ...

Dewetting of Acrylic Conformal Coating
Test the Solder Resist with a good Solvent Stencil Cleaner and see if you get any discolouration off the wipe ...

Special Cleaning Needs for BGA and QFN Components
Please do not use Water Soluble (OA)Flux under tight components, also IF you HAVE TO CLEAN then do not use ...

Dewetting of Acrylic Conformal Coating
It doesn't sound like a flux issue but more like a problem with un cured solder resist. Try and check ...

Delay Before Washing Water Soluble Flux
The answer is really about what type of Water Soluble Flux you are using. Some that are not H1 or ...

Best Way to Eliminate Dross?
One of the most overlooked aspect of dross contamination is the quality of the solder bar to start with. If ...

Source of Wave Solder Bridging
We really need to know if this is Lead Free or Leaded Wave Soldering as they do process differently. ONE ...

Cause of Solder Icicles
Check boards are being fluxed right first and then check top board preheat is around 100-110C, both these can cause ...

BGA Rework Clean-up?
If its no clean paste that has been used to apply the original BGA then this residue will be fine ...

Post Print Inspection Issue
Search Google for misprint cleaners many different effective machines in the market so you don't have to scrap off the ...

Flux Residue Causing Test Issues
A good No Residue flux will not interfere with Test, we do see allot of residues from Solder Pallets and ...

Tinning Selective Soldering Machine Nozzles
From the sounds of it the flux you are using for the Tinning application is not strong enough to give ...

Solder Joint Explosions
If the PCB's are HASL finished, the problem may be due to improper rinsing of the HASL fluids/fluxes used. They ...

Advantages Using OSP Surface Finish
Flatest surface for SMT placement. No possible contamination from Bareboard assembly chemicals interfering with long term reliability. Shelf life should ...

BGA Rework Flux Recommendation
It is best to use proper Rosin based rework flux gel as this will aid with the heat transfer to ...

Solder Fillet Peaks
I would test a higher percentage flux content solder wire first ...

Recommendation for PCB Surface Finish
I would recommend ENIG for both leaded and lead free. ...

Concerns Using Aluminum Flux Tank
Using Aluminium flux tank is not the best idea especially if using a VOC Free flux as this will attack ...

Flux Residue Visible After 3 Months
Most No Clean or No Residue fluxes are not Hygroscopic and tested according to the various standards and do not ...

Tombstoning Dilemma
Tombstoning can be designed out with Stencil/Pad layout and turning the PCB in reflow so both sides of the component ...

Hot or Cold DI Water Rinse
I would strongly recommend heated DI water as some wetting agents used in fluxes will Gel if hit with cold ...

Tacky Flux Residue Problem
The amber tacky residues would probably be the Rosin carrier for the Solder Paste. I assume this is a Water ...

Components Lifting During Wave Soldering
Firstly, make sure the component lead lengths are not catching on the solder nozzle, if they are cut them shorter. ...

Problems with blow holes
Lead To hole Ratios are fairly important but not normally a cause for Blow Holes. If you are using Single ...

SMT Component Shift
Component shift on identical boards through same type of oven can be due to air flow through the nozzles of ...

No clean flux stains during reflow
Have you tried cleaning out the tunnel and extraction these do get gummed up with flux. The stains should be ...

How to eliminate micro solder balls?
Check the solder resist cure as this will be the most significant factors. Take a ball under at least 60x ...

Blow Holes on Clinched Radial Lead Components
It is possible that if the clinch is too tight then the LED will form/sit over the top of the ...

Alternative to Conformal Coating
Not seen any precut sheet suited to this but a good chemical alternative is Rosin Lacquer as Rosin naturally repels ...

Screen Print Shelf Life
Stencil and shelf life will be dependant completely on chemistries and formulations used in your paste choice. Some water soluble ...