We search for industry news, so you don't need to.
Ask the Experts Panel  
Questions Index  ■  Submit a Question  ■  Experts Panel  ■  Join the Panel

Edithel Marietti
image

Senior Manufacturing Engineer
iDirect
Edithel is a chemical engineer with 20 year experience in manufacturing & process development for electronic contract manufacturers in US as well as some major OEM's. Involved in SMT, Reflow, Wave and other assembly operations entailing conformal coating and robotics.

Edithel Marietti has submitted responses to the following questions.
SMT Target Component Placement
In this case the ideal placement is determined by your pad size. Pad size should not exceed the specifications recommended ...
Insufficient Barrel Fill on Through-hole Components
There are several types of lead retention mechanisms. These are design to provide extra support between the lead and the ...
How to Re-qualify BGA Spheres
Some manufacturers assign a shelf life on 1-2 years to their spheres. One way to re-qualify is by performing a ...
Cleaning Under Low Clearance Components
If you have the option to use a no-clean solder paste formulation then even better. You can still use a ...
What Caused SMT Pads to Oxidize After Reflow
There is a slight possibility that the Nickel in the ENIG oxidized after reflow. I have ran hundreds of ENIG ...
Requirements for Installing Leaded vs. Lead-free Press Fit Connectors
There is no difference. It all depends on connector size and the number of pins. However, there might be a ...
Solution for Warped PCBAs
Once the PCB is populated there is really not much you can do to remove the warp. Unwarping a PCBA ...
No-Clean Flux Residue After Selective Soldering
If your no-clean flux residues are not visible to the naked eye after selective soldering, congratulations you are running a ...
Moisture Sensitivity Level for Bare Boards
I have not seen a MSL value assigned to bare boards. However, there is some relationship between the surface finish ...
Specific Solder To Control Dendritic Growth
Most of the time PCB fabricators operate on very tight budgets. Asking the fabricator to use a different type of ...
What Is Causing Slanted Pins After Reflow
Due to the rheology of solder paste and density of the component you might experience the pogo pin to float ...
Solder Balling Prediction Formula
I don't believe there is a mathematical way to solve for this type of defect but here are some ideas ...
IPC-A-610 Class 3 - IPC-A-600 Class 2
One question we need to answer first is what is the end use of the assembly that you are building. ...
Solder Balling Splash After Reflow
By reading the details of the question I believed you've solved your issue. If you experience solder ball with only ...
Recommended Solder Paste Aperture Configuration
I will follow the manufacturer's recommended pad shape. However, when dealing with such small components, your solder type and stencil ...
Two Year Component Date Code Mandate
I do not know of a written standard except for moisture sensitive devices. It seems that many companies have adopted ...
Recommended Fiducial Shape
I recommend using a full circle instead of the donut. ...
What Is This Contamination?
Looking at the images gives me several ideas as to what happened: The wash process before coating was not able ...
BGA Placement Paste or Only Flux
When it comes to lead-free I prefer to deposit paste on the PCB BGA pads to maintain a steady process ...
Frequency of Temperature and Relative Humidity Tracking
If your monitors have the capability of recording the information so that you may produce it at any time then ...
Solder Paste Thickness Measurements
I never used locations but I learned that the best way to measure solder paste thickness is to measure the ...
Reliability Concerns When Converting to Lead-free
This is a problem. I'd rather order 100 new boards with ENIG finish. Solder joint reliability and function are highly ...
How To Reduce Solder Joint Voids in QFN Components
You can reduce the stencil aperture by 50% to 80% of the thermal pad area and also by segmenting it ...
Stainless Steel Benches and ESD
Stainless steel is a highly conductive metal not suitable for electronic work. This type of tables need a hard ground ...
Solder Mask Thickness Tolerance
I do not believe there is a standard value. Solder mask thickness depends on the material and product class. In ...
Using Solder Paste Beyond the Expiration Date
White residue on assemblies using water-soluble pate could be the result from many factors. However, you mentioned that the solder ...
Question About PPM Defect Rate for Reversed Packages
Very seldom you'll find a reversed package from a component supplier. On the other hand, reversed packages from SMT placement ...
Concerns With Silver Finish Component Leads
Were the terminations dipped in silver or electroplated? It is recommended to use a SAC alloy when dealing with components ...
Selective Solder System Purchased At Auction
There are two options. One is to purge the system by removing all solder old from the pot(s). The other ...
Solder Paste Mixing
If the vendor's requirements for handling and storage of solder paste are followed mixing it with a plastic spatula should ...
Ultrasonic Cleaning and Surfactants
You may add a surfactant/detergent. Pay special attention to the data-sheet for additional instructions, temperature & pressure settings. You do ...
Partially Visible or Hidden Solder Connections
Since one side is covered, I believe that without X-RAY it is almost impossible to conclude that you have 75% ...
Initial Screen Print Test Board
This is a good practice in order to set your printer when you run a PCB for the first time. ...
Reusing recovered solder paste
I'd recommend to first look over the solder paste datasheet provided by the paste manufacturer and see if there is ...
Dust contamination after selective soldering
Correct, the wash won't remove this type of residue. Try to answer these questions; when did the issue begin (was ...
Questions Regarding Underfill Options
There is IPC J-STD-030 Guideline for Selection and Application of Underfill Material for Flip Chip and other Micropackages. It provides ...
Stencil Pattern for Thermal Pads on QFNs
There are some basic rules for QFN pad arrays. A widely used one is to use square pads of 1 ...
Mixed Process Solder Joint Appearance, Smooth or Grainy?
If you are using tin/lead 63/37 solder paste you should see a smooth & shiny surface.  ...
Environment Impact on Assembly, Printing and Reflow
From the data provided I take that your particle count is 100,000 per cubic meter.  If this is the case, ...
BGA Solder Ball Shelf Life
Many BGA manufacturers have a standard 2-year shelf life for their products.  I have also seen others which recommend just ...
Calculating PCB Hole Diameters
Many manufacturers have the capability of producing boards with a via aspect ratio of 10:1.  If we apply this specification ...
Tin-lead Component Projections
It seems that the Aerospace and Defense Industry will continue to use tin-lead processes & components at least until 2019. ...
Conformal Coating in Nitrogen Environment
You may use air as you have a good filtering and drying system. ...
Viscosity of Solder Paste Before Printing
Due to the different brands, flux chemistries, test methods and solder paste properties I do not believe there is a ...
QFN Test Failures Caused by Flux
The test engineer is probably right. There had been studies on the effects of no-clean flux residues on RF assemblies. ...
Can a Few Contaminated Joints Cause an Assembly to Fail RoHS Compliance?
The maximum ppm value for Lead is 0.1% by weight or 1000 ppm.  If you calculated that the added Lead ...
Bottom Terminated Components and Vias
Tenting on the top side only will minimize the risk of voiding caused by outgassing as the solder flows down ...
Wave Soldering System Nitrogen Use
Many wavbe soldering machines come equipped with flowmeters for air & nitrogen. These flowmeters usually measure Cubic Feet per Minute ...
Estimating Failure Rate During Rework
One alternative is to examine your rework area and answer the following questions: Total rework time. (min) Cost of rework ...
LED Component Shift During Reflow
Check your profile.  There is a possibility that outgassing is causing the shifting of LED's. ...
Hot Air Solder 0201s and 01005s
There are several companies that offer mini and micro soldering/de-soldering tweezers just for this type of work. I recommend checking ...
PCBA Inspection Process Causing Damage
True. Moving the PCBA on a hard surface will sometimes scratch components, and stress soldered joints. There are many table-top ...
What is the IPC Definition for Uncommonly Harsh?
When using the term "uncommonly harsh" it usually refers to meeting military specifications. For example, equipment used in airplanes, tanks, ...
Floor Life of MSD Parts
Assuming by the information provided I believe you are talking about an MSD classification of 3 which amounts to 168 ...
Gold Edge Contact Rework
First we need to understand the nature of the residues. Are they a product of process control, equipment performance, board ...
QFN Open Solder Joints
I'd recommend you review your land pattern design, reflow settings, solder mask, amount of solder paste being deposited on those ...
Stencil Cleaning Frequency
There is no established industry standard for a stencil cleaning interval. It depends on the complexity of the assembly, the ...
Customer Approval for Repairs
IPC 7711 Section 1.7 establishes: When rework, repair, or modification of newly manufactured products is conducted, appropriate approvals may be ...
Jumper Wire Limits
I do not believe there is a limit as long as you don not break form, fit and function.  It ...
BGA Ball Sheer Testing
The goal of a shear test is to see the BGA "break" which points toward a ductile fracture. What you ...
Cleanliness Standards for Electronic Components
I have not seen any other document that provides specs for component cleanliness other than IPC but you are not ...
Overlap Solder Joint Failures
Not knowing much about your process and end product; the joint between strips could be flexing thus generating a solder ...
Solder Paste Prep Before Use
You will know if 1.5 to 2 hours is enough by checking the inside temperature of the jar by introducing ...
Tiny Solder Balls After Reflow
I've experienced the same condition after stencil misprints. First, check your stencil print wash settings and purge the stencil solvent ...