Edithel Marietti

Edithel Marietti has submitted responses to the following questions.

Solder Paste Print Test Boards
For stencil printing it is always recommended to use a test board as your first print. Many companies use the ...

Solder Paste Stencil Inactivity
I never let the solder stay idle for more than 4 hours. Some paste solders can remain on the stencil ...

Storage To Prevent Corrosion
Corrosion is caused by oxidation. You need an atmosphere of oxygen & water for corrosion to begin. Nitrogen is an ...

How To Remove Oxidation On SMT Components
I’d start out with a low activity flux and inspection. If that does not work move to medium activity flux ...

Baking Old PCBs Prior To Reflow
I will go ahead and bake just for good measure. Moisture hides in weird places like inside plated through-holes. ...

Design Considerations and Impact on Assembly
One item that I have experienced is to go straight into production without running a design for manufacturing or DFM. ...

Moisture Barrier Bag Calculation
Take the largest assembly that fits inside the bag and then vacuum-seal it. Second, change everything to mils, for example ...

Acceptability Standard for Plated Hole Barrel Fill
Per J-STD-001F; "For components having pre-established lead lengths that are less than the board thickness, and the component or lead ...

Step Stencil Squeegee Angle
The purpose of the step-up or step-down stencil is to achieve maximum solder deposition in the modified area. As with ...

Hand Sanitizer Contamination
According to Sani-Cide 94 SDS, the material will react with oxidizers, strong acids and reactive metals. Tin, lead and copper ...

Point to Pint Soldering vs Drag Soldering
I believe the drag soldering technique is not the correct method considering the contacts are only 2mm apart from each ...

Wet Based Stencil Cleaning or Dry Wipe Stencil Cleaning
I've always used a combination of wet & dry. Many of the newer model printers allow you to choose any ...

Solder Contamination Sources
You have two major sources. First, your PCB. Due to the different surface finishes available you could add different types ...

Water Wash vs. No-clean
Your contract should specify which process to use. This is agreed between the two parties. It is a good practice ...

EMI Shield Reflow Soldering Techniques
You could use a pallet with spring loaded supports for the shield frames but it will increase your production costs. ...

Shelf Life Limit for Soldering Old Components
One way is to contact the component's manufacturer. In some cases they might recertify or extend the shelf life. However, ...

Adding Chlorine to a DI (Deionization) Water System
Chlorine works large water systems like swimming pools & potable water tanks. If you have a DI water tank and ...

IPC SOIC Defect Question
When solder touches a ceramic or metal component's body it could break the seal between the lead and the body ...

BGA Solder Ball Collapse
Even though tin-lead and lead-free solder differ in density & wetting ability, the flux ingredients & metal content of lead-free ...

Reflow Profile for Mixed Lead-Free and Leaded
Use the recommended solder profile for the alloy & flux chemistry and it should work. Just remember that your PCBA ...

How to Detect Counterfeit Components?
A visual check will work much better when you look for the following: Incomplete logos and/or they can be easily ...

Application Using No-Clean and Water Soluble Fluxes
One rule I follow is; "never mix flux chemistries". The activity of the organic flux used on water-soluble wire is ...

OA Flux Turning Blue
A change of color usually means that the flux is reacting with something else. In other words, your flux is ...

Baking Concerns for Stacked Trays of Components
You need to ensure that there is enough heat flowing through the trays. If they are too close to each ...

Contamination From Anti-static Foam
Since you mention this is a high value PCBA and you want it to remain operational, your best option is ...

Inspection for Hidden Solder Joints
I think the best option in this case is X-RAY. First, determine your soldering process capability (Cp & CpK) for ...

What's Causing Cloudy Conformal Coating
There is a possibility that the coating is not adhering to the IC leads. One way of testing this theory ...

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,this ...

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 ...

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 (labor rate) ...

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 pads. ...

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
IPC7711 Section 1.7 establishes: When rework, repair, or modification of newly manufactured products is conducted, appropriate approvals may be required. ...

Jumper Wire Limits
Ido not believe there is a limit as long as you don not break form, fit andfunction. It all depends ...

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
Youwill know if 1.5 to 2 hours is enough by checking the inside temperature of thejar by introducing a thermometer ...

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 ...