Fritz Byle
Process Engineer
Astronautics
Fritz's career in electronics manufacturing has included diverse engineering roles including PWB fabrication, thick film print & fire, SMT and wave/selective solder process engineering, and electronics materials development and marketing. Fritz's educational background is in mechanical engineering with an emphasis on materials science. Design of Experiments (DoE) techniques have been an area of independent study. Fritz has published over a dozen papers at various industry conferences.
Fritz Byle has submitted responses to the following questions.
Water Wash vs. No-clean
I can understand that there are valid engineering arguments on both sides... on the one hand, you may not know ...
ESD Ground Wire Gauge
You are correct in assuming that it really does not matter. The ESD ground always has a series resistor of ...
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). ...
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 ...
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 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. ...
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 ...
What Is This Contamination?
There is almost definitely corrosion going on, so the question is what is the source? From what we can see, ...
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 ...
Problems With Large Voids
There are several possible contributing causes for the large voids, including: Lack of egress for gasses generated during reflow Higher ...
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 ...
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're right... everyone seems to have a different number for the rate. This is because the test methods used vary ...
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 platingc onditions, 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 thickness)Solder ...
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
Inorder to determine if your warm-up time after removal from refrigeration isadequate, insert a temperature probe into the center of ...
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 ...
Exposed Copper Risk
Ina word, yes, you should be concerned. The level of risk really depends on the enclosure and operating environment. If ...
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 ...
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
Inorder to reduce or eliminate the dimples, we first need to list the rootcause(es):Solder shrinkage during solidificationEntrapped gasses that shrink ...
Rechecking Thermal Profiles
Yes, you should periodically run a thermal profile. With the controls in place on most modern convection-based ovens, the risk ...
Soldering Station Calibration
Personally, despite what the manufacturer says, I would still verify that they are within tolerance at the desired setpoint, and ...
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
Diffuselighting is going to make the biggest difference overall. You may be able toreduce some glare by using polarized glasses, ...
Conformal Coating Recommendation
Conformal coating is certainly one component to an environmental protection strategy.Some cautions here:Remember that conformal coating will not protect from ...
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 gravity)Mechanical stresses applied (oven ...
Solder Mask Ghosting
Like you, I am skeptical that you've got the same problem across multiple suppliers and PWB types. Seems much more ...
Burned Chip Repair
In general, whether you can effectively make the repair depends on:Gaining access to the replacement part,Determining that the PWB has ...
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 ...
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 ...
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
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 isthe micro-resistance method. In commercially available equipment (e.g. UPACaviderm), ...
Profiling for Double Sided BGA
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
Youmay find that you need a small increase in pressure. Whether you do or notdepends on the design of the ...
PoP Assembly Options
Of the two options presented, Option 1 results in one lessreflow cycle for the entire assembly, and that is a ...
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 ...
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 makethe hole as small as tolerances will allow. We are ...
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 ...
A Generic Reflow Profile
In general, no there is not. Through careful testing, you may find that you can narrow the number of required ...
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 ...
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 ...
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 ...
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 ...
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). ...
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 ...
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 ...
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 ...
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 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, meaninga very thin Au layer, less than 6µin. I can ...
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 verified ...
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 ...
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 and ...
|