Fritz Byle has submitted responses to the following questions.

BGA reballing question
The concern of course is, as the alloy in the stripping pot gets contaminated with Pb-free solder, the remaining solder ...

Pad Missing ENIG Plating
Skipped pads can occasionally occur with ENIG, or other chemically deposited coatings (I've seen it with Immersion Ag, for instance). ...

Tarnished OSP Circuit Boards
If you are seeing oxidation on the pads as they are received, that is certainly not normal. Either the OSP ...

IPC SOIC Defect Question
Historically the reason for this difference is that the ceramic or glass-bodied parts have glass seals that may be damaged ...

Adding Chlorine to a DI (Deionization) Water System
If you're adding chlorine to the water after it is deionized, you've defeated the purpose of deionization. Chlorine is very ...

BGA Solder Ball Collapse
There's really no hard answer to this question. The one thing you can count on is that the Pb-Free alloys ...

Reflow Profile for Mixed Lead-Free and Leaded
The big change is the move from the fusible SnPb HASL finish to a non-fusible surface finish; since you cannot ...

Application Using No-Clean and Water Soluble Fluxes
You'd need to be absolutely sure that you removed all of the water soluble flux residue, as any remaining residue ...

What's Causing Cloudy Conformal Coating
It's clear (pun intended) that the conformal coating has been degraded in the area between the leads, and that an ...

Allowable Bow and Twist on Round PC Fab
My approach would be as follows:Calculate the dimensions of the largest square you can draw on the circular partUse the ...

Reflow Oven - 5 Zone or 8 Zone
From a practical perspective, five (heating) zones is certainly enough, given that the length of the zones is configured properly. ...

Moisture Sensitive Components in Flooded Storage Facility
Short answer, there are probably alternatives. Whether they are worth it depends on the value of the components, including their ...

Insufficient Barrel Fill on Through-hole Components
I'll assume that this is a wave soldering process, and not a selective soldering process (though the concerns are similar). ...

SMT Target Component Placement
The key question is whether the location of the LED is shifted prior to reflow, or shifting during reflow. You ...

How to Re-qualify BGA Spheres
The pertinent question to consider is, what physical processes do we expect might degrade performance of the spheres, and have ...

Cleaning Under Low Clearance Components
Yes, your fears are absolutely justified. Residual water-wash flux is very corrosive, and it will be near impossible to ensure ...

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?
Theappearance of the final joint depends on the make-up of the non-SnPb finish onthe part, and the amount of said ...

Environment Impact on Assembly, Printing and Reflow
Themajority of SMT assembly areas are not formally controlled to a particulatecount. That said, the particulate levels in most world-class ...

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 number ...

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
Firstand foremost, tenting on both sides without filling is not recommended. Thereis a high risk of entrapped chemistry which can ...

Wave Soldering System Nitrogen Use
You'llneed some type of flow meter somewhere. The best solution is an electronic,totalizing flowmeter installed directly upstream of the wave ...

Copper Dissolution Rate
You'reright... everyone seems to have a different number for the rate. This is becausethe test methods used vary so widely. ...

PCBA Inspection Process Causing Damage
I'dagree that any time we slide a PCBA across a surface, there is some risk. If thesurface is clean and ...

What is the IPC Definition for Uncommonly Harsh?
Thelanguage here may seem very vague, and there is, I think, actually a goodreason for this. I don't think that ...

Floor Life of MSD Parts
Sinceyou specify 168 hours as the floor life, I will assume that your devices areMSL 3. You probably do not ...

Gold Edge Contact Rework
The"residue" might actually be a surface condition caused by the platingconditions, usually by plating too quickly (too high current density). ...

Gold Plating and Embrittlement
Whetherthere is a risk of embrittlement depends on several variables:Amount of gold expected to be leached (soldered area*goldthickness)Solder volume in ...

Overlap Solder Joint Failures
Thedescription of "cold" solder joints is not conclusive as to root cause, howeverthat should not prevent us from envisioning a ...

Solder Paste Prep Before Use
Inorder to determine if your warm-up time after removal from refrigeration isadequate, insert a temperature probe into the center of ...

Tiny Solder Balls After Reflow
Themost likely culprit here is the volatile materials in the solder paste. It'snot the only possibility, but you have done ...

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 exhausted ...

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
Ina word, yes, you should be concerned. The level of risk really depends on theenclosure and operating environment. If the ...

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 and ...

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'venot heard of anyone doing the scoring after SMT, though I’m sure it has beendone. I can’t think of any ...

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'svery hard to tell from the tiny photo, but it looks like the roughness isconfined to the solder on the ...

Solder Paste Past Shelf Life
Ifyou do not have internal capability to re-certify the material, contact themanufacturer. They should be able to re-certify it. The ...

Concave Via Fillets Causing Problems
Inorder to reduce or eliminate the dimples, we first need to list the rootcause(es):Solder shrinkage during solidificationEntrapped gasses that shrink ...

Options for Reballing BGA Components
Iwould re-ball using spheres and tacky flux. I would not use paste. There aretwo main reasons for this:The variability inpaste ...

MSD Components Baked Too Long
The biggest risk of baking too long is loss ofsolderability. Many parts today have pure (or nearly pure) tin finishes. ...

Conformal Coating Press Fit Connectors
Afterreview of the pertinent section of IPC-A-610, I actually don't see that thereis any requirement for all soldered surfaces to ...

Production Floor Temperature and Humidity Loggers
Whetherone logger is enough is entirely dependent on the facility. In facilities whereairflow into/out of the facility is tightly controlled, ...

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 driving ...

ESD Grounding - 1 Meg Ohm Resistor
The1-megohm resistance is used for two reasons:It limits the speedthat charge is passed, avoiding rapid discharge of an item, which ...

What Is Acceptable Bending For Assembled PCBs?
The limits of acceptable bending depend strongly onthe type and size of components mounted. BGAs in particular are sensitive tobending ...

Rechecking Thermal Profiles
Yes,you should periodically run a thermal profile. With the controls in place onmost modern convection-based ovens, the risk of a ...

Mixing Silicone and Acrylic Conformal Coatings
In a word, "yes." Adhesion of the acrylic to the siliconematerial, or to any residues left after removal of same, ...

Soldering Station Calibration
Personally, despite what the manufacturer says, Iwould still verify that they are within tolerance at the desired setpoint, anddo this ...

Minimum Component Lead to Lead Spacing for Wave Soldering
Theminimum practical pitch for multi-lead components such as connectors is about1.27mm (0.050”); I have not personally dealt with any with ...

Frequency of Checking Solder Paste Viscosity
Thereare some issues that make checking viscosity less useful than it might be: Differences in the equipment used (manufacturers usually ...

Wave Solder Pot Alloy Adjustment Formula
I'llassume that you have room in the pot to make a small addition without firstremoving some. We will be adding ...

IPC 610 Class 3 with Missing Non-functional BGA Pads
Froman inspection standpoint, no, I don’t believe that boards with thenon-functional lands meet the intent of the specification, since solder ...

Very Low Temp PCBs
Ingeneral, you want to look at indium-based solder alloys. Pure indium is usedfor seals in cryogenic applications and would definitely ...

Reduce Glare During Assembly
Diffuselighting is going to make the biggest difference overall. You may be able toreduce some glare by using polarized glasses, ...

Conformal Coating Recommendation
Conformalcoating is certainly one component to an environmental protection strategy.Some cautions here:Remember that conformal coating will not protect from liquidwater, ...

Excess Flux Residue After Hand Soldering
Theamount of flux does not seem excessive. Soldering this type of terminalrequires a fairly high volume of solder, so there ...

Circuit Board Bow and Twist
Thereare four main possible causes to look at:Design (copperimbalance)Fabrication (processerror)Support issues(sagging due to gravity)Mechanical stressesapplied (oven conveyor) Because the boards ...

Rise of Bismuth Levels in our Solder Pots
Couldbismuth be coming from the components? Short answer, yes, it could. Is itlikely? Not so much. I know of some ...

ESD Conductive Floor Tile Worry
If the worst case is defined as 10^4 (10k) ohms fromsource to ground, then there is most definitely a concern, ...

Lead-Free Solder Contaminated with Lead
First, I completely agreethat you need to address the root causes of the Pb contamination to avoid arecurrence. As far ...

Suggested Limit for PCBA Heat Cycles
Theanswer is "it depends." We can think about rework cycles as taking up someportion of the useful thermo-mechanical life of ...

Solder Mask Ghosting
Likeyou, I am skeptical that you've got the same problem across multiple suppliersand PWB types. Seems much more likely that ...

Test Probe Problems After Pin-In-Paste
Youare correct suspecting that you are addressing the symptom and not the rootcause, but addressing the root cause (elimination of ...

Burned Chip Repair
Ingeneral, whether you can effectively make the repair depends on:Gaining access to thereplacement part,Determining that thePWB has not been damaged ...

Confused About IPC-A-610 Class 2 vs. Class 3
I agree that the classes in the IPC-A-610 (or theJ-STD-001 document for that matter) are completely unrelated to whether aproduct ...

Bottom Side Chip Bonding
Thisis a really good question. In fact, there is a bunch of incorrect informationout there on this. There are a ...

Challenging Cleaning Problem
Giventhat you really would prefer to clean due to your high-impedance circuitry, youneed to find an economical, reliable way to ...

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
ForBGA components down to about 0.8mm pitch, HASL is an acceptable finish. Yourcomponent, with a 0.6mm ball diameter, surely has ...

Concerns Replacing High Speed Components with No-Clean Solder
I'llassume that by 1GB you meant 1 GHz. In short, yes, there can be problems withsome pastes. To make a ...

Head-In-Pillow Reject Rate
What'sacceptable has a lot to do with the tolerance for failures in the specificproduct and application. Also, you may find ...

Solder Caking to Bottom of PCBs After Wave
Hard to say exactly, but if the problem appearedimmediately after changing out the pot, I would bet on differences in ...

Octagonal Pads for 0402 Chip Caps
Ihave not seen this exact strategy, but it does make sense. The octagonalpattern (effectively a square with the corners cut ...

Selective Printing for BGA Components
Ifthe BGA is depopulated but PWB lands are present, sure, you can simply notprint the lands where no balls are ...

What Causes Component Rotation During Reflow?
Thereason behind the rotation is unbalanced wetting forces. As the paste begins toreflow, it wets one side of the inductor ...

Extending Shelf Life for Jars of Solder Paste
The first course of action should be to talk with atechnical resource at the manufacturer. It's highly likely that the ...

How to Eliminate Via Pits
Youhave two things working against you here. The first and most important is thatalmost all alloys shrink during solidification. For ...

Bow and Twist Requirements
Theshort answer is, whatever your contract with the customer says. If I assumethat it says nothing about bow & twist, ...

Legend Marking Discoloration
Thedarkening is of course caused by thermal decomposition of the ink. This type ofdegradation is typically accelerated above a threshold ...

BGA Joint Voids - Accept or Reject
Let'sfirst address the question of IPC-610 acceptability. The acceptabilitycriterion for voiding in IPC-610 is currently <25% void area on transmissionx-ray. ...

Pre-bake in a Vacuum
Yes,in theory this will work. The vacuum will lower the boiling point of watervapor, and also decrease the partial pressure ...

Via Wall Thickness Test
Yes, there is. The method commonly in use by PWB fabricators isthe micro-resistance method. In commercially available equipment (e.g. UPACaviderm), ...

Double Sided BG
I'll assume that the BGAs are not back-to-back; ifthey are, that's another question entirely. If they are not back-to-back, thenprofiling ...

Step Stencil Question
Youmay find that you need a small increase in pressure. Whether you do or notdepends on the design of the ...

Dam & Fill vs. Conformal Coating
A dam & fill strategy may be driven by a need forstronger environmental protection, for high voltage isolation, for mechanicalstabilization ...

Through Hole Connector Solder Joint Hole Fill
Ourcompany faces this problem daily since our products (aerospace electronics) usethick PWBs and PTH connectors with high pin counts in ...

PoP Assembly Options
Of the two options presented, Option 1 results in one lessreflow cycle for the entire assembly, and that is a ...

Removal of Non-functional Pads from Inner Layers
An interesting question to be sure. Fabricatorsnormally do prefer it, because it makes drilling easier. Copper is a tough,stringy metal, ...

ESD and Humidification
Let's do a thought exercise. Assume we have a workstationlocated in a very dry area, but otherwise configured with dissipative ...

Solder Paste Viscosity
If you decrease the particle size of the powder while keepingthe metal percentage the same, the viscosity will increase. The ...

Spotting After DI Water Cleaning
The spotting could conceivably be due to fine, insolublematerial suspended in the water. Such material would not necessarily contributeto reduction ...

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. How ...

Long Term Component Storage
As an Aerospace & Defense OEM, we have the samerequirements, and have implemented LTS (Long-Term Storage) protocols to dealwith it. ...

Standards for Pin-in-Paste
The answer to the pin-to-hole ratio question is usually to makethe hole as small as tolerances will allow. We are ...

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 caninvolve tool tip ...

Cause of Green/Blue Oxide Buildup
What you are seeing are most likely not oxides, but "metalsalts" which are corrosion products. In a marine environment, it ...

What Are Realistic Guidelines for PCB Flexing?
IPC A-600 applies only to unassembled PWBs. The reason for thereference to SMT boards is that raw PWBs that will ...

Stencil Cleaning Procedure
The practical answer is "it is if they can show that it does thejob." What you really care about is ...

Pin-in-Paste Problems
It's difficult to give specific recommendations, since we don'tknow the exact geometry and materials of construction of the pin. In ...

Lifted Lead on SOT Component
Assessing root cause on this defect is tricky. One or more ofseveral possible causes may be in play. Let's imagine ...

Reflow Oven Calibration Schedule
A good basic recommendation is to run a weekly profile, and todo control charting on the temperatures and timings to ...

A Generic Reflow Profile
In general, no there is not. Through careful testing, you mayfind that you can narrow the number of required profiles ...

Reduced pH and Specific Gravity of Flux
Let's take specific gravity first... if it is low, that means thatthere is more solvent and less solids present (I'm ...

Epoxy Wicking up Wire Insulation
Three opportunities present themselves:Modifyor change the epoxy such that it does not wickModifythe curing process for the current epoxySealthe wire-to-board ...

Solder Paste Life on the Stencil
You probably don't need to change it. I'll make the assumptionthat your 250g additions represent about half the volume on ...

White Legend Ink Turning Pink
Let's think about the possible ways that a pink color could begenerated:Theink picked up traces of a red dye from ...

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 3)Toe ...

Dross Particles Sticking to PCBs
If the pot surface has been cleaned, then the dross particlesare coming from immersed parts. Dross often gets entrained in ...

Solder Paste Alloy Check
The two biggest problems here are:Even a pretty "warm" SnPb profile is just barely above themelting point of the Pb-free ...

Un-cleaned PCB Assemblies Potted
There are two very different possible scenarios here:The flux used was a water-soluble fluxThe flux used was a rosin-based flux ...

Solder Balls During Rework
I would need to see samples to be sure, but I would bet that thesolder balls are forming because the ...

Transfer Efficiency Greater Than 100%
Yes, it is possible for transfer efficiency actually be greaterthan 100%, and yes, it is possible that systematic error in ...

Cleanliness After Coating Removal
Cleanlinesshere is a big concern, since urethane coatings normally require highly alkalinestrippers to remove. The residues from these strippers are ...

Pin-in-Paste Standards
Normally you are struggling to get adequate paste volume andrequired volume increases as the square of the PTH diameter, so ...

Solder Popping Out of Holes
It'shard to say for sure, not knowing more specifics of the PWB construction andthe thermal history of the board. What ...

Zip-lock Bags vs. Heat Sealed Bags
In a word, no. When the components are placed in the MoistureBarrier Bag (MBB) we'll assume they are dry. We ...

How to Remove Adhesive Bonded Resistors
A"hot tweezer" adapter for a soldering station probably will do the trick forremoval. It will heat both joints and the ...

Voids with Back to Back BGA Components
It'snot uncommon for voids that may have been present at a size too small to detectto grow during the second ...

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 380W/(m*K). ...

Insufficient Barrel Fill on Through-hole Components
If you search for generic recommendations on how much over-sizeyour hole needs to be, you'll find a wide range of ...

Cause of Cracking on SOT23 Components
Itseems that mechanical damage after placement is the most likely scenario. Isthe problem position near a board edge by any ...

SMT Component Glue Strength
There are two basic alternatives:Use a shear tester and shear the component off using aflat-faced rod to push the component ...

Test for Flux Penetration
What we used to do was to use a plate with perforations ofvarious sizes arranged in a pattern that repeated ...

Improve DPPM for Wave Soldering Using Nitrogen
It's possible that a nitrogen environment will improveperformance. It's also possible that for some defect types it will increasedefects. The ...

BGAs Mixing Tin-Lead and Lead-Free
In either case, if full mixing of the alloys is ensured by thereflow profile, reliability of the resultant joints is ...

Rework for OSP Assemblies
I can think of one scenario where procedures might need to bemodified; when rework needs to be performed on the ...

Deionized Water Sample Testing
Absorption of ionic species such as CO2 from the atmosphereas well as very small amounts of contaminants from containers can ...

BGA Die and Pry Testing
In short, I think it's unlikely that the root cause of theobserved defect is Kirkendall voiding. What's needed for root ...

Options to Cut Inspection Time
Without much more knowledge of your situation, my gut reactionwould be to say "no." It's almost always better to invest ...

Class 3 Cleaning Requirements
The answer is "it depends."Whether or not you need to make any changes to cleaning operations dependsentirely on the requirements ...

Reflow of Double Sided Micro BGAs
Before we discuss in detailwhat you need to do, let's first list the risks you have to deal with:Risk of ...

Mixing Different SAC305 Solders
If both of the manufacturers certify that their products conformto the requirements of J-STD-006, then the solders should be interchangeable.There ...

Solder Mask Mis-registration Issue
Let's start with the industry specifications; IPC-6012 statesthat no encroachment of mask on non-soldermask-defined BGA lands is allowable,except of course ...

Tacky Substance Under Zero Clearance Parts
It is very normal for flux residue to remain under theselow-clearance components and to potentially bridge between contacts, in fact ...

Can Solder Joint Geometry Change Resistance?
First and foremost, adding a resistance in the circuit shouldnot increase the current. If you model it, you should find ...

Syringe Dispensed Solder Paste for Hand Soldering
Syringe-dispensed solder paste can be an acceptable substitutefor wire + liquid flux; some pastes work better than others for thisapplication. ...

Fastening Surface Mounted Connectors Before or After Refow?
Asfar as I know, there is no general guidance, due to the fact that eachconnector design is unique. In general, ...

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 residues, after ...

Blind Hole Pin Soldering
It's definitelypossible that gas will be trapped and out-gas as it expands. Depending on theexact geometry of the design, this ...

Reflow Causing Warp
If you are stuck withthe design, then the only recourse is to mitigate the warping. If there aremounting holes available ...

Black Land Edges
I'll make the assumption that the Ni-Au finish is ENIG, meaninga very thin Au layer, less than 6µin. I can ...

Variation in Solder Paste Thickness
I believe your answer lies in the "edge effects." The smalleraperture has an area ratio, AR(1) of 0.62. This is ...

Gold Plated Hole Defects
It's almost always harder to fill open holes than holes withleads in them. The presence of a lead in a ...

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 and verifiedthat ...

Soldering Multilayer Ceramic Chip Capacitors
The degree of sensitivity of the ceramic cap depends on severalthings, including the body size and the type of dielectric. ...

Idle Wave Solder Temperature
There are two significant downsides to cooling the pot below thesolidification temperature:Repeated solidification and re-melting puts mechanical stresseson the immersed ...

Insufficient Plated Hole Fill with Electrolytic Capacitors
Contributing root causes of this defect can be one or more ofthe following:Too many ties to inner ground planes, coupled ...

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 andprobably ...