What Caused SMT Pads to Oxidize After Reflow
There are three possibilities here:
The finish was ENIG, but the gold was improperly applied (too thin) or the gold ...
|
Moisture Sensitivity Level for Bare Boards
You are correct that the MSL of the bare board can vary; the factors affecting moisture sensitivity, roughly in order ...
|
Specific Solder To Control Dendritic Growth
It's certainly not unheard-of for a customer to specify which solder paste to use. Contract manufacturers tend to not like ...
|
Solder Balling Splash After Reflow
The small, uniform size of most of the balls visible on the x-ray image strongly suggests to me that they ...
|
IPC-A-610 Class 3 - IPC-A-600 Class 2
Yes, they are different requirements. If we can make the case that a PWB designed and inspected to IPC-A-600 Class ...
|
What Is This Contamination?
There is almost definitely corrosion going on, so the question is what is the source? From what we can see, ...
|
Frequency of Temperature and Relative Humidity Tracking
There's no standard that I'm aware of. From a practical standpoint, it's very dependent on the physical characteristics of your ...
|
BGA Placement Paste or Only Flux
The flux-only scenario has been used for many years for flip-chip and for fine-pitch BGA mounting to some degree. It ...
|
Solder Paste Thickness Measurements
It's a conundrum, to be sure. In an ideal world, we want to be certain that the volume of paste ...
|
Reliability Concerns When Converting to Lead-free
In my opinion, yes, there is reason for concern. There has been some research that suggests that Pb content in ...
|
Old Components and Blow Holes
I can certainly see old components causing wetting problems. If the wetting problems are spotty, localized issues and some happen ...
|
What Is Causing Connectors to Bow?
I'm carefully scrutinizing the image, and based on what I can see, it looks like the last 5 or 6 ...
|
How To Reduce Solder Joint Voids in QFN Components
Window-paning is the accepted method of optimizing the solder paste deposition for the large pad under QFN components. The optimal ...
|
Is Solder Mask Considered an Insulator
Solder mask should never be considered an insulator. It can have porosity and pinholes, and we should therefore not consider ...
|
Solder Mask Thickness Tolerance
The 0.8-mil thickness is probably near the higher end, but in range for a photoimageable mask, provided that the measurement ...
|
Question About PPM Defect Rate for Reversed Packages
We'll have to assume that we are ruling out "systematic" errors, e.g. an entire reel of parts loaded opposite of ...
|
Using Solder Paste Beyond the Expiration Date
A white powder suggests to me a metal salt. If the powder is on the board (outside the solder joint) ...
|
Concerns With Silver Finish Component Leads
Silver as an alloying addition to SnPb solder will change the mechanical properties of the solder, making it somewhat stronger ...
|
Selective Solder System Purchased At Auction
Really the best solution is to replace the pot. A pot designed for SnPb solder may not be appropriate for ...
|
Problems With Large Voids
There are several possible contributing causes for the large voids, including:
Lack of egress for gasses generated during reflow
Higher ...
|
Ultrasonic Cleaning and Surfactants
In short, yes. Deionized water does have a high surface tension, and because the ultrasonic cleaning process relies on cavitation, ...
|
Partially Visible or Hidden Solder Connections
In situations similar to the one you show, it is often possible to get a very good estimate of the ...
|
Initial Screen Print Test Board
There are a couple reasons why it might be a good idea:
It will get the paste roll worked (sheared) ...
|
Components Falling Off During Wave Soldering
I'm not at all familiar with lacquer coating, but that should be of little importance. Here's what to look for: ...
|
Mixed Process Solder Joint Appearance, Smooth or Grainy?
The
appearance of the final joint depends on the make-up of the non-SnPb finish on
the part, and the amount ...
|
Environment Impact on Assembly, Printing and Reflow
The
majority of SMT assembly areas are not formally controlled to a particulate
count. That said, the particulate levels in ...
|
Soldering Components with Silver Pads
Since you state that the silver dissolves into the solder, I will assume that there is more than an immersion ...
|
0201 Pick & Place Nozzle Plugging
First, you are correct that you should carefully consider the transition to a 0.004" stencil. There will be an impact ...
|
BGA Solder Ball Shelf Life
The shelf life, as defined by the manufacturer, takes into account all aspects of the package, but let's stick to ...
|
Tough Hand Soldering Problem
The "land" area for the wire attachment is typically made of the same material as the grid. Depending on the ...
|
Selective Soldering Frame Causing Cold Solder Joints
Yes, absolutely. Most wave soldering systems are a little challenged with getting adequate preheat and maintaining it across the gap ...
|
Conformal Coating in Nitrogen Environment
Without very specific knowledge of your process, including the coating materials involved, my comments must be rather general. The main ...
|
Viscosity of Solder Paste Before Printing
Short answer... the one that works (four that paste).
Long answer we could write a textbook on. In essence, the ...
|
QFN Test Failures Caused by Flux
Short answer, we can't rule it out. At high frequencies, typically above 1 GHz, some flux residues can create losses ...
|
Can a Few Contaminated Joints Cause an Assembly to Fail RoHS Compliance?
If you regard all of the solder as one separable component of the assembly, I guess you could conclude that ...
|
Bottom Terminated Components and Vias
First
and foremost, tenting on both sides without filling is not recommended. There
is a high risk of entrapped chemistry ...
|
Wave Soldering System Nitrogen Use
You'll
need some type of flow meter somewhere. The best solution is an electronic,
totalizing flowmeter installed directly upstream of ...
|
Copper Dissolution Rate
You're
right... everyone seems to have a different number for the rate. This is because
the test methods used vary ...
|
PCBA Inspection Process Causing Damage
I'd
agree that any time we slide a PCBA across a surface, there is some risk. If the
surface is ...
|
What is the IPC Definition for Uncommonly Harsh?
The
language here may seem very vague, and there is, I think, actually a good
reason for this. I don't ...
|
Floor Life of MSD Parts
Since
you specify 168 hours as the floor life, I will assume that your devices are
MSL 3. You probably ...
|
Gold Edge Contact Rework
The
"residue" might actually be a surface condition caused by the plating
conditions, usually by plating too quickly (too high ...
|
Gold Plating and Embrittlement
Whether
there is a risk of embrittlement depends on several variables:
Amount of gold expected to be leached (soldered area*gold ...
|
Overlap Solder Joint Failures
The
description of "cold" solder joints is not conclusive as to root cause, however
that should not prevent us from ...
|
Solder Paste Prep Before Use
In
order to determine if your warm-up time after removal from refrigeration is
adequate, insert a temperature probe into the ...
|
Tiny Solder Balls After Reflow
The
most likely culprit here is the volatile materials in the solder paste. It's
not the only possibility, but you ...
|
Hand Soldering at Low Temperature
First, let's look at the impact on the "delta-T," or the temperature difference between the board and the soldering tip. ...
|
Solution for Grape Effect
There are two possible causes for the rough surface of solder joints on the smaller components:
The flux is being ...
|
Component Damage From IR Reflow
I suspect that this is the same issue that I have seen on another component type in the past. The ...
|
Exposed Copper Risk
In
a word, yes, you should be concerned. The level of risk really depends on the
enclosure and operating environment. ...
|
Manual or Automated Assembly?
Even moderate levels of automation can have huge benefits. I would definitely recommend starting to move down the path to ...
|
Pin in Paste Solder Dropping
Your main contributing causes to this problem are likely to be as follows, in approximate order of importance:
Pin geometry ...
|
Removal of Coatings from PCBs
The short answer to this question is "use the materials and process recommended by the coating manufacturer." It truly is ...
|
V - Scoring PCB Question
I've
not heard of anyone doing the scoring after SMT, though I’m sure it has been
done. I can’t think ...
|
How To Rework SMT Connector with Center Ground Strip
Normally we remove these using a hot-air rework station. If the board is high-mass (very thick), pre-heating the board to ...
|
Cause of Incomplete Solder Reflow
It's
very hard to tell from the tiny photo, but it looks like the roughness is
confined to the solder ...
|
Solder Paste Past Shelf Life
If
you do not have internal capability to re-certify the material, contact the
manufacturer. They should be able to re-certify ...
|
Concave Via Fillets Causing Problems
In
order to reduce or eliminate the dimples, we first need to list the root
cause(es):
Solder shrinkage during solidification ...
|
Options for Reballing BGA Components
I
would re-ball using spheres and tacky flux. I would not use paste. There are
two main reasons for this: ...
|
MSD Components Baked Too Long
The biggest risk of baking too long is loss of
solderability. Many parts today have pure (or nearly pure) tin ...
|
Conformal Coating Press Fit Connectors
After
review of the pertinent section of IPC-A-610, I actually don't see that there
is any requirement for all soldered ...
|
Production Floor Temperature and Humidity Loggers
Whether
one logger is enough is entirely dependent on the facility. In facilities where
airflow into/out of the facility is ...
|
Silver Solder for Audio Circuits
I agree with Jerry K's points (2) and (3). In addition,
let me offer some insight into what may be ...
|
ESD Grounding - 1 Meg Ohm Resistor
The
1-megohm resistance is used for two reasons:
It limits the speed
that charge is passed, avoiding rapid discharge of ...
|
What Is Acceptable Bending For Assembled PCBs?
The limits of acceptable bending depend strongly on
the type and size of components mounted. BGAs in particular are sensitive ...
|
Rechecking Thermal Profiles
Yes,
you should periodically run a thermal profile. With the controls in place on
most modern convection-based ovens, the risk ...
|
Mixing Silicone and Acrylic Conformal Coatings
In a word, "yes." Adhesion of the acrylic to the silicone
material, or to any residues left after removal of ...
|
Soldering Station Calibration
Personally, despite what the manufacturer says, I
would still verify that they are within tolerance at the desired setpoint, and ...
|
Minimum Component Lead to Lead Spacing for Wave Soldering
The
minimum practical pitch for multi-lead components such as connectors is about
1.27mm (0.050”); I have not personally dealt with ...
|
Frequency of Checking Solder Paste Viscosity
There
are some issues that make checking viscosity less useful than it might be:
Differences in the equipment used (manufacturers ...
|
Wave Solder Pot Alloy Adjustment Formula
I'll
assume that you have room in the pot to make a small addition without first
removing some. We will ...
|
IPC 610 Class 3 with Missing Non-functional BGA Pads
From
an inspection standpoint, no, I don’t believe that boards with the
non-functional lands meet the intent of the specification, ...
|
Very Low Temp PCBs
In
general, you want to look at indium-based solder alloys. Pure indium is used
for seals in cryogenic applications and ...
|
Reduce Glare During Assembly
Diffuse
lighting is going to make the biggest difference overall. You may be able to
reduce some glare by using ...
|
Conformal Coating Recommendation
Conformal
coating is certainly one component to an environmental protection strategy.
Some cautions here:
Remember that conformal coating will not ...
|
Excess Flux Residue After Hand Soldering
The
amount of flux does not seem excessive. Soldering this type of terminal
requires a fairly high volume of solder, ...
|
Circuit Board Bow and Twist
There
are four main possible causes to look at:
Design (copper
imbalance)
Fabrication (process
error)
Support issues
(sagging due to ...
|
Rise of Bismuth Levels in our Solder Pots
Could
bismuth be coming from the components? Short answer, yes, it could. Is it
likely? Not so much. I know ...
|
ESD Conductive Floor Tile Worry
If the worst case is defined as 10^4 (10k) ohms from
source to ground, then there is most definitely a ...
|
Lead-Free Solder Contaminated with Lead
First, I completely agree
that you need to address the root causes of the Pb contamination to avoid a
recurrence. ...
|
Suggested Limit for PCBA Heat Cycles
The
answer is "it depends." We can think about rework cycles as taking up some
portion of the useful thermo-mechanical ...
|
Solder Mask Ghosting
Like
you, I am skeptical that you've got the same problem across multiple suppliers
and PWB types. Seems much more ...
|
Test Probe Problems After Pin-In-Paste
You
are correct suspecting that you are addressing the symptom and not the root
cause, but addressing the root cause ...
|
Burned Chip Repair
In
general, whether you can effectively make the repair depends on:
Gaining access to the
replacement part,
Determining that the ...
|
Confused About IPC-A-610 Class 2 vs. Class 3
I agree that the classes in the IPC-A-610 (or the
J-STD-001 document for that matter) are completely unrelated to whether ...
|
Bottom Side Chip Bonding
This
is a really good question. In fact, there is a bunch of incorrect information
out there on this. There ...
|
Challenging Cleaning Problem
Given
that you really would prefer to clean due to your high-impedance circuitry, you
need to find an economical, reliable ...
|
Reflow oven testing and calibrating concern
I agree with the responders that there is no real industry standard, and
I also agree with the general sentiment ...
|
HASL Surface Finish and Coplanarity
For
BGA components down to about 0.8mm pitch, HASL is an acceptable finish. Your
component, with a 0.6mm ball diameter, ...
|
Concerns Replacing High Speed Components with No-Clean Solder
I'll
assume that by 1GB you meant 1 GHz. In short, yes, there can be problems with
some pastes. To ...
|
Head-In-Pillow Reject Rate
What's
acceptable has a lot to do with the tolerance for failures in the specific
product and application. Also, you ...
|
Solder Caking to Bottom of PCBs After Wave
Hard to say exactly, but if the problem appeared
immediately after changing out the pot, I would bet on differences ...
|
Octagonal Pads for 0402 Chip Caps
I
have not seen this exact strategy, but it does make sense. The octagonal
pattern (effectively a square with the ...
|
Selective Printing for BGA Components
If
the BGA is depopulated but PWB lands are present, sure, you can simply not
print the lands where no ...
|
What Causes Component Rotation During Reflow?
The
reason behind the rotation is unbalanced wetting forces. As the paste begins to
reflow, it wets one side of ...
|
Extending Shelf Life for Jars of Solder Paste
The first course of action should be to talk with a
technical resource at the manufacturer. It's highly likely that ...
|
How to Eliminate Via Pits
You
have two things working against you here. The first and most important is that
almost all alloys shrink during ...
|
Bow and Twist Requirements
The
short answer is, whatever your contract with the customer says. If I assume
that it says nothing about bow ...
|
Legend Marking Discoloration
The
darkening is of course caused by thermal decomposition of the ink. This type of
degradation is typically accelerated above ...
|
BGA Joint Voids - Accept or Reject
Let's
first address the question of IPC-610 acceptability. The acceptability
criterion for voiding in IPC-610 is currently <25% void area ...
|
Pre-bake in a Vacuum
Yes,
in theory this will work. The vacuum will lower the boiling point of water
vapor, and also decrease the ...
|
Via Wall Thickness Test
Yes, there is. The method commonly in use by PWB fabricators is
the micro-resistance method. In commercially available equipment (e.g. ...
|
Double Sided BG
I'll assume that the BGAs are not back-to-back; if
they are, that's another question entirely. If they are not back-to-back, ...
|
Step Stencil Question
You
may find that you need a small increase in pressure. Whether you do or not
depends on the design ...
|
Dam & Fill vs. Conformal Coating
A dam & fill strategy may be driven by a need for
stronger environmental protection, for high voltage isolation, for ...
|
Through Hole Connector Solder Joint Hole Fill
Our
company faces this problem daily since our products (aerospace electronics) use
thick PWBs and PTH connectors with high pin ...
|
PoP Assembly Options
Of the two options presented, Option 1 results in one less
reflow cycle for the entire assembly, and that is ...
|
Removal of Non-functional Pads from Inner Layers
An interesting question to be sure. Fabricators
normally do prefer it, because it makes drilling easier. Copper is a tough, ...
|
ESD and Humidification
Let's do a thought exercise. Assume we have a workstation
located in a very dry area, but otherwise configured with ...
|
Solder Paste Viscosity
If you decrease the particle size of the powder while keeping
the metal percentage the same, the viscosity will increase. ...
|
Spotting After DI Water Cleaning
The spotting could conceivably be due to fine, insoluble
material suspended in the water. Such material would not necessarily contribute ...
|
Double Sided Reflow for Micro BGA Components
Both convection and vapor phase are potentially good processes.
In either case, PWB warpage during reflow needs to be controlled. ...
|
Long Term Component Storage
As an Aerospace & Defense OEM, we have the same
requirements, and have implemented LTS (Long-Term Storage) protocols to deal ...
|
Standards for Pin-in-Paste
The answer to the pin-to-hole ratio question is usually to make
the hole as small as tolerances will allow. We ...
|
Reliability of Automated Soldering vs. Hand Soldering
There are three main sources of differences in reliability:
solder joint behavior, component damage, and cleanliness. Hand soldering can
involve ...
|
Cause of Green/Blue Oxide Buildup
What you are seeing are most likely not oxides, but "metal
salts" which are corrosion products. In a marine environment, ...
|
What Are Realistic Guidelines for PCB Flexing?
IPC A-600 applies only to unassembled PWBs. The reason for the
reference to SMT boards is that raw PWBs that ...
|
Stencil Cleaning Procedure
The practical answer is "it is if they can show that it does the
job." What you really care about ...
|
Pin-in-Paste Problems
It's difficult to give specific recommendations, since we don't
know the exact geometry and materials of construction of the pin. ...
|
Lifted Lead on SOT Component
Assessing root cause on this defect is tricky. One or more of
several possible causes may be in play. Let's ...
|
Reflow Oven Calibration Schedule
A good basic recommendation is to run a weekly profile, and to
do control charting on the temperatures and timings ...
|
A Generic Reflow Profile
In general, no there is not. Through careful testing, you may
find that you can narrow the number of required ...
|
Reduced pH and Specific Gravity of Flux
Let's take specific gravity first... if it is low, that means that
there is more solvent and less solids present ...
|
Epoxy Wicking up Wire Insulation
Three opportunities present themselves:
Modify
or change the epoxy such that it does not wick
Modify
the curing process for ...
|
Solder Paste Life on the Stencil
You probably don't need to change it. I'll make the assumption
that your 250g additions represent about half the volume ...
|
White Legend Ink Turning Pink
Let's think about the possible ways that a pink color could be
generated:
The
ink picked up traces of a ...
|
Toe Fillet Requirements on Gull Wing Components
Per J-STD-001, there is no requirement:
There is no reference to a minimum toe fillet height (Class 1, 2, and ...
|
Dross Particles Sticking to PCBs
If the pot surface has been cleaned, then the dross particles
are coming from immersed parts. Dross often gets entrained ...
|
Solder Paste Alloy Check
The two biggest problems here are:
Even a pretty "warm" SnPb profile is just barely above the
melting point of ...
|
Un-cleaned PCB Assemblies Potted
There are two very different possible scenarios here:
The flux used was a water-soluble flux
The flux used was a ...
|
Solder Balls During Rework
I would need to see samples to be sure, but I would bet that the
solder balls are forming because ...
|
Transfer Efficiency Greater Than 100%
Yes, it is possible for transfer efficiency actually be greater
than 100%, and yes, it is possible that systematic error ...
|
Cleanliness After Coating Removal
Cleanliness
here is a big concern, since urethane coatings normally require highly alkaline
strippers to remove. The residues from these ...
|
Pin-in-Paste Standards
Normally you are struggling to get adequate paste volume and
required volume increases as the square of the PTH diameter, ...
|
Solder Popping Out of Holes
It's
hard to say for sure, not knowing more specifics of the PWB construction and
the thermal history of the ...
|
Zip-lock Bags vs. Heat Sealed Bags
In a word, no. When the components are placed in the Moisture
Barrier Bag (MBB) we'll assume they are dry. ...
|
How to Remove Adhesive Bonded Resistors
A
"hot tweezer" adapter for a soldering station probably will do the trick for
removal. It will heat both joints ...
|
Voids with Back to Back BGA Components
It's
not uncommon for voids that may have been present at a size too small to detect
to grow during ...
|
Conformal Coating Over Heat Sinks
Yes, definitely mask them; the coating will impede performance.
The bulk thermal conductivity of a copper heatsink is close to ...
|
Insufficient Barrel Fill on Through-hole Components
If you search for generic recommendations on how much over-size
your hole needs to be, you'll find a wide range ...
|
Cause of Cracking on SOT23 Components
It
seems that mechanical damage after placement is the most likely scenario. Is
the problem position near a board edge ...
|
SMT Component Glue Strength
There are two basic alternatives:
Use a shear tester and shear the component off using a
flat-faced rod to push ...
|
Test for Flux Penetration
What we used to do was to use a plate with perforations of
various sizes arranged in a pattern that ...
|
Improve DPPM for Wave Soldering Using Nitrogen
It's possible that a nitrogen environment will improve
performance. It's also possible that for some defect types it will increase ...
|
BGAs Mixing Tin-Lead and Lead-Free
In either case, if full mixing of the alloys is ensured by the
reflow profile, reliability of the resultant joints ...
|
Rework for OSP Assemblies
I can think of one scenario where procedures might need to be
modified; when rework needs to be performed on ...
|
Deionized Water Sample Testing
Absorption of ionic species such as CO2 from the atmosphere
as well as very small amounts of contaminants from containers ...
|
BGA Die and Pry Testing
In short, I think it's unlikely that the root cause of the
observed defect is Kirkendall voiding. What's needed for ...
|
Options to Cut Inspection Time
Without much more knowledge of your situation, my gut reaction
would be to say "no." It's almost always better to ...
|
Class 3 Cleaning Requirements
The answer is "it depends."
Whether or not you need to make any changes to cleaning operations depends
entirely on ...
|
Reflow of Double Sided Micro BGAs
Before we discuss in detail
what you need to do, let's first list the risks you have to deal with: ...
|
Mixing Different SAC305 Solders
If both of the manufacturers certify that their products conform
to the requirements of J-STD-006, then the solders should be ...
|
Solder Mask Mis-registration Issue
Let's start with the industry specifications; IPC-6012 states
that no encroachment of mask on non-soldermask-defined BGA lands is allowable,
except ...
|
Tacky Substance Under Zero Clearance Parts
It is very normal for flux residue to remain under these
low-clearance components and to potentially bridge between contacts, in ...
|
Can Solder Joint Geometry Change Resistance?
First and foremost, adding a resistance in the circuit should
not increase the current. If you model it, you should ...
|
Syringe Dispensed Solder Paste for Hand Soldering
Syringe-dispensed solder paste can be an acceptable substitute
for wire + liquid flux; some pastes work better than others for ...
|
Fastening Surface Mounted Connectors Before or After Refow?
As
far as I know, there is no general guidance, due to the fact that each
connector design is unique. ...
|
White Discoloration After Ultrasonic Cleaning
Your residue could be one of two things:
Un-dissolved flux that has been attacked by the chemistry.
Partially dissolved flux ...
|
Blind Hole Pin Soldering
It's definitely
possible that gas will be trapped and out-gas as it expands. Depending on the
exact geometry of the ...
|
Reflow Causing Warp
If you are stuck with
the design, then the only recourse is to mitigate the warping. If there are
mounting ...
|
Black Land Edges
I'll make the assumption that the Ni-Au finish is ENIG, meaning
a very thin Au layer, less than 6µin. I ...
|
Variation in Solder Paste Thickness
I believe your answer lies in the "edge effects." The smaller
aperture has an area ratio, AR(1) of 0.62. This ...
|
Gold Plated Hole Defects
It's almost always harder to fill open holes than holes with
leads in them. The presence of a lead in ...
|
Glued SMT Components Falling Off
First, some key assumptions:
There was in fact sufficient adhesive present.
You've done a thermal profile of the curing process ...
|
Soldering Multilayer Ceramic Chip Capacitors
The degree of sensitivity of the ceramic cap depends on several
things, including the body size and the type of ...
|
Idle Wave Solder Temperature
There are two significant downsides to cooling the pot below the
solidification temperature:
Repeated solidification and re-melting puts mechanical stresses ...
|
Insufficient Plated Hole Fill with Electrolytic Capacitors
Contributing root causes of this defect can be one or more of
the following:
Too many ties to inner ground ...
|
HASL vs. Immersion Gold
There is really no one-size-fits-all answer to this question.
The answer for your application really depends on the following factors ...
|
