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Georgian Simion
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Engineering and Operations Management
Independent Consultant
Georgian Simion is an independent consultant with 20+ years in electronics manufacturing engineering and operations.
Contact me at georgiansimion@yahoo.com.


Georgian Simion has submitted responses to the following questions.
No-Clean Flux Residue After Selective Soldering
Based on the product that you are using, you will have more or less no clean flux residue on the ...
Solution for Warped PCBAs
This might be a problem depending on how serious the warp is - there are IPC acceptability criteria for this ...
Moisture Sensitivity Level for Bare Boards
Usually the bare boards can be packed in pink wrap with desiccant to protect them against moisture. Based on the ...
Specific Solder To Control Dendritic Growth
It is easier said than done. You can ask your supplier for specific solder paste to be used and you ...
Channels To Reduce Voids in Large Pads
The Dpak packages are notorious for voids on the solder joints - you can alleviate this problem by changing the ...
What Is This Contamination?
With not a lot of data here are few things that I can think about - this can be some ...
Two Year Component Date Code Mandate
There are no industry standards that I know of that will limit your parts usage within a specific time frame ...
Recommended Solder Paste Aperture Configuration
A 15% reduction on the pad size and 2 mil stencil worked for the applications that I have done. The ...
Balling Splash After Reflow
From your problem statement, I do not know if you have the same PCB from different suppliers and have problem ...
Solder Balling Prediction Formula
Solder balling is a process problem that can occur from multiple causes. Stencil aperture design and stencil thickness are just ...
BGA Placement Paste or Only Flux
I do not see a risk with this process. My personal opinion is actually that the BGA pads should have ...
Old Components and Blow Holes
In general the older the component gets, the more the oxidation builds up on their leads. In the soldering process ...
What Is Causing Connectors to Bow?
I had the issue with the same type of connector years ago. The bowing occurred on the cold down zone ...
Dust contamination after selective
This can be flux residue, dross, etc. - I would say that we can speculate about this until you have a ...
Initial Screen Print Test Board
It depends on what is the population on the board. The smaller the parts/apertures, the higher risk of paste deposit ...
Reusing recovered solder paste
Re-using paste is pretty common as the solder paste price is considerable. I would advise you to: Use less paste ...
Solder Paste Mixing
The use of a mechanical (automated) mixing process is recommended to be done in conjunction with a viscometer to understand ...
Problems With Large Voids
This is a common issue on the QFN packages - most of the times the issues are related to: Stencil aperture ...
Solder Splashes During Wave Soldering
This is going to be a large work volume project. I would recommend to check the following: Wave profile settings: ...
Selective Solder System Purchased At Auction
Replace the pot - all the manufacturers have different solder pots for lead free and leaded solder as the lead free ...
Using Solder Paste Beyond the Expiration Date
It is very difficult to connect the two - did you run the same assembly with fresh paste and you've had ...
Question About PPM Defect Rate for Reversed Packages
This is not likely come from the taping and reeling service supplier. Also the pick and place equipment is going ...
Stencil Pattern for Thermal Pads on QFNs
IPC 7525 should give you everything that you need to know about apertures design. Now, for your particular case, this ...
Delamination After V-cut
This is a common issue for the V-cut depanelization process. There are multiple variables in this process to be considered: ...
Mixed Process Solder Joint Appearance, Smooth or Grainy?
The ideal appearance of the slder joints is smooth. Based on what you are doing I expect to see issues ...
Components Falling Off During Wave Soldering
The coating can be a problem but since you are using the adhesive to hold the components in place, this ...
Soldering Components with Silver Pads
If you have worked on the oven profile and also changed the solder paste type and the results are not ...
0201 Pick & Place Nozzle Plugging
The 0201 and 01005 component pads pasting is definitely a challenge.My recommendation is to actually go to a 3 mil ...
Hot Air Solder 0201s and 01005s
In order to rework small/special components, you need special tools.  From your question, I do not understand if you are ...
Need for Reflow Profiles
Completely disagree. I consider this is the perfect recipe for disaster - even if there are 3, it is like ...
Problems with Insufficient Barrel Fill
With limited information it is hard to point the exact reason why this happened. However, based on a project that ...
Issues with BGA Components Near PCB Edges
 I would not stress that much about this. However- few things to consider: Heat needed to reflow the parts - ...
Problems with blow holes
In order to express my opinion, more information is needed: Did you have problems from the very beginning with this ...
Flux Residue Causing Test Issues
In my opinion, regardless of the path you are going to follow, you will add cost to your process No ...
Coating Scored Panels Prior to Separation
If you have a scored panel and the coating gets into the V-score, my first question would be how effective ...
Soldering Lead-free Components with Tin-lead Solder
Depending on the volume you might use an alternate method to solder that component. A BGA rework station can place ...
Delamination Dilemma
In order to solve this problem, more data is needed. The PCBs can have moisture trapped from the supplier or ...
Reflow Oven Calibration Schedule
First I would check the manufacturer's recommendation and have that on the internal PM schedule. Using a KIC or MOLE ...
Toe Fillet Requirements on Gull Wing Components
Per IPC-610, there is no requirement for toe fillets. If all the other requirements are met except the toe fillet ...
Customer Approval for Repairs
As a general rule, the repair of an assembly requires customer's approval and rework does not regardless of the class ...
QFN Open Solder Joints
With limited data, I can only guess at this time. The suspect area is the ground pad. The paste deposition ...
Floor Life of MSD Parts
You definitely have to bake the components once they reach the maximum exposure limit, regardless of the color of the ...
Stencil Cleaning Frequency
There are a lot of factors that will determine the stencil cleaning frequency Assembly population complexity Smallest aperture Stencil thickness ...
BGA Shifting During Reflow
There is a lot of data to be collected in order to determine the root cause and create a counter ...
Solder Paste Mixing After Storage
There are different methods that you can use to mix the solder paste and get it to the room temperature. ...
Puzzling PCB Reflow Delamination Problem
First things first - the 100 C baking temperature will not get the moisture out of your boards unless you ...
SMT Component Lead Oxidation
As an internal fix, if it is not very difficult, fluxing the components on a FR4 board and reflow them ...
Best Way to Eliminate Dross?
The first thing that I would do is start using nitrogen that will be the main agent that will ...
Micro Solder Balls Problem
All good points from the other experts. One suggestion that I would have look at the recommendations and try ...
How to Clamp Odd Shaped Circuit Boards
There are solutions out there. Fixturing can be created for almost anything - I suggest you to get in touch ...
Hand Soldering Alternative
If this is a high volume I would immediately go to another solution for these wires - is a board ...
Solder Joint Explosions
Usually this type of defect is associated with moisture entrapped in the bare board's structure. The fact that changing the ...
What's Causing Sticky Stencil Blades?
From my point of view, you have done a little bit of change overload without really knowing what the cause ...
How to Mask Areas During Conformal Coating
From my experience, for the switches pads masking is the most effective using Kapton tape "dots" (you can find them ...
BGA Ball Sheer Testing
I would expect the separation to happen at the board level (solder joint to the pad) and/or at the component ...
Jumper Wire Limits
IPC does not specify a certain number of jumper wires to be used on a board. These are modifications required ...
Bake for Repair
Definitely you have few variables on this problem statement - how much time the board was out for, what is ...
Solder Paste Prep Before Use
First - the time out of refrigerator before use is a little short at 2 hrs. Try to increase that ...
Tiny Solder Balls After Reflow
This problem requires a true root cause analysis. Changing a lot of things without a plan and a correct data ...
Conformal Coating and Connector holes
To avoid coating material to get inside the connectors, the masking is very important. For the base of the connectors, ...
Reflow oven testing and calibrating concern
From my perspective using 1 board for everything is a bad approach. From the oven performance (daily/weekly check) - temperature, ...
Intermittent BGA Test Problems
If I would create a list related to this it would include (note: in random order): Oven profile related: head ...
Delamination Causing Scrap
As I've mentioned in my answer regarding the bake before rework question, the delamination is commonly caused by moisture ingression ...
Rechecking Thermal Profiles
Other than profiling each assembly/board when running it the first time, a periodic check is recommended to make sure that ...
Question About J-STD-001
Without running a DOE it is very difficult to assess the risks involved with this. A rule of thumb is ...
Challenges with 01005 Components
Here is a my list of important challenges: Pad design on the board associated defects: tombstoning, unsoldered parts Stencil ...
IPC 610 Class 3 with Missing Non-functional BGA Pads
If you are missing the pads (pulled in the rework process), this is a defect regardless of functionality of the ...
Blow Holes and Disturbed Joints
This issue can be caused by a lot of parameters. I do not recommend to change them all but you ...
Test Probe Problems After Pin-In-Paste
I do not know if I have a solution to your problem but I have some recommendations and questions that ...
Confused About IPC-A-610 Class 2 vs. Class 3
I've seen multiple times the association between Class 3 electronic products and aerospace applications. Usually, the space applications are expecting ...
Burned Chip Repair
This can be repaired. The questions I what and how much is damaged as well as what caused this and ...
Automatic Insertion Causing Plated Damage
After seeing the images, it is pretty obvious that this design is not suitable for clinching. There are selective soldering ...
Bottom Side Chip Bonding
Unfortunately this is another questions that bring the "it depends" answer. Usually the components placed on the first side of ...
Why Should We Consider Smart Feeders?
If you want and need traceability as well as inventory control and set-up time reduction, the smart feeder is your ...
Uncontrolled Environment Causing Problems
If these are high speed lines, I would imagine that the processing time (paste printing, pick and place, travel to ...
HASL Surface Finish and Coplanarity
One of the HASL finish characteristics is variable thickness. This can cause co-planarity issues for BGAs as well as for ...
Head-In-Pillow Reject Rate
At this failure rate the oven profile would be through the last things I recommend to be changed. It is ...
Solder Caking to Bottom of PCBs After Wave
You do not specify what type of contamination you've experienced. After cleaning and re-filling the solder pot, did you perform ...
Selective Printing for BGA Components
At first sight this looks like a good approach - however I do not see the savings being significant. This ...
Lead Free Reflow Oven Zone Count
Depending on the complexity of the board (PCB itself) as well as the population, more zones will offer you the ...
Pick Performance for SMT Placement Machine
From my point of view it depends on your production type: mass production, prototype, high mix, low volume, etc. I ...
BGA Rework Residue Concern
The residue is most likely flux. Do you use any bonding agents or under-fill on the component? Those can also ...
Uneven Conformal Coating
I've seen already all good recommendation for your problem so instead of repeating, I will add: are you performing a ...
What Causes Component Rotation During Reflow?
The SMT pin inductors have the tendency to move while going through the reflow. This is caused by the large ...
Extending Shelf Life for Jars of Solder Paste
You will have to get in contact with the supplier/manufacturer of the solder paste and approach them with a request ...
What is Causing Solder Joint Cracking?
Talking about a connector soldered to the board - this is the interface with other assemblies in the final product. ...
Legend Marking Discoloration
Theoretically and practically, the silkscreen should withstand the soldering process temperature as well as multiple cycles (SMT, Wave soldering, Selective ...
BGA Joint Voids - Accept or Reject?
This looks like excessive voiding. However, without a tool (like X-Ray voiding % check) that will give you a quantitative ...
Pre-bake in a Vacuum
From experience I can tell you that the time reduction is going to happen for sure. The vacuum will help ...
BGA Component Moisture Exposure
Baking the assemblies will not fix the parts if they got damaged during reflow. Passing test is not a separation ...
Solder Balls During Selective Soldering
The main reason for these issues it looks to be inadequate heat applied to the assembly (in the pre-heating process ...
Tombstoning Dilemma
For sure a lot of variables in this problem: Pad design Paste deposition (x, y deviation and volume/release from the ...
How to Gauge Solder Paste Volume
Several guiding rules that I've used: Always start the job (first print from the back of the stencil towards the ...
Pros and Cons of Cleaning No-clean
If it is "no-clean", why do you clean it? Cleaning the "no-clean" residues is not only costly (chemicals $$$) but ...
Leaded to Lead-Free Wave Solder Pallets
I do not see an issue with using the same pallets, as long as you've clean them thoroughly. Washing them ...
Most Important Factors for Screen Printing
The solder paste volume will make the difference between a conforming and a non-conforming solder joint. Insufficient solder and excess ...
Mixed Technology - Which First
The order can definitely be reversed - actually this is the traditional way to do it - the SMT first ...
Cold Solder Joints on 0603 Components
Since changing the used solder paste with fresh one improved the solder wetting results you can attribute the problems to ...
Component Shifting
The way this issue is defined is not completely clear. Do you perform an AOI step right after pick and ...
Standards for Pin-in-Paste
Through plated hole to pin ratio, as a lot of other things in our industry, depends on design. There are ...
Reliability of Automated Soldering vs. Hand Soldering
This process is, of course, one to avoid. When it happens though, try to keep it to a minimum. Having ...
What Causes SMT Component Shift?
There are more questions to bring up in order to get to the bottom of this issue: Are all of ...
What Are Realistic Guidelines for PCB Flexing?
Flatness of the PCBs is critical not only for processing but from a reliability point of view. I do not ...
Stencil Cleaning Procedure
IPA wipes are very popular so they are used a lot. Being a manual process though, it depends so much ...
Source of Wave Solder Bridging
Wave solder bridging can happen for various reasons. First, the data has to be collected: What type of solder is ...
Cause of Unusual Contamination?
This looks more like  metal migration through the gold plating - I would contact the PCB supplier. If this a ...
Trouble Soldering a PC104 Connector
Is there anything special with the pins that are not getting soldered? Are there the same pins that you have ...
A Generic Reflow Profile
I would definitely not recommend a generic profile. There might be "families" of boards that can use the same settings ...
Lifted Leads on QFP Components
Co-planarity is a common failure mode for the multi-leaded parts. The issue can be caused in the forming or packaging ...
Pre-Bake Standard for Rework
How many times did you see: It depends! Well, this is another one. The PCB material type is very important ...
Problems Hand Soldering 24 Layer Board
Everybody agrees that this is a heat transfer related issue. There are just too many variables here to come up ...
Post Print Inspection Issue
Obviously you will look into eliminating the root cause of the printing problems. If you have misprints however there are ...