Richard D. Stadem

Advanced Engineer/Scientist

General Dynamics

Richard D. Stadem is an advanced engineer/scientist for General Dynamics and is also a consulting engineer for other companies. He has 38 years of engineering experience having worked for Honeywell, ADC, Pemstar (now Benchmark), Analog Technologies, and General Dynamics.

Richard D. Stadem has submitted responses to the following questions.

BGA Reballing Question
As usual, Circuit Technology Center has a complete reliability handle on this type of rework! Bob LePage covered everything. I ...

BGA Solder Ball Wetting
There is a yellow arrow pointing to the right solder ball, so I am assuming that is the only issue ...

Solder Ball Wrinkles
I recognize this issue immediately when I see it, simply because I have been "fortunate" enough to be heavily involved ...

Trays for MLS Baking
Most companies use Durostone CAS761 or very similar materials for trays, fixtures, and tooling intended for hot processing of ESD ...

Baking Old PCBs Prior To Reflow
Refer to IPC-1601 for answers to all questions regarding baking of circuit boards, including methods for determining optimum bake times ...

Polyurethane Conformal and Acrylic Coating on the Same PCB
Common sense tells me that the requirements the original product was built to remain in place. Because your original product ...

Coils Rotated After Reflow
It's a pretty large coil so I doubt that the wetting tension could pull it very well, and if it ...

Design Specs for Selective Soldering
The experts have given you some good information, but nobody addressed the original request, which design standards have this info? ...

Conformal Coating Bubbles
Yes, it definitely is a defect condition. One of the biggest reasons for bubbles in the conformal coating is moisture ...

Solder Joint Blow Holes
I have to agree with John DeLeeuw and Fritz Byle. The fact that the blowholes affect only the LEDs with ...

Oxidation of Solder Balls During Secondary Reflow
Assuming you mean BGA solder joints, it is very unlikely that good solder joints created during reflow 1 would oxidize ...

Moisture Barrier Bag Calculation
With regard to Mr. Olan's comment regarding the purpose of vacuum sealing food, one is in fact sealing to keep ...

Acceptability Standard for Plated Hole Barrel Fill
Keep in mind that without lead protrusion you may have difficulty achieving a complete hole fill the length of the ...

SOT (Small Outline Transistor) Body Cracks
All of the experts have chimed in with good information on placement pressure, reflow profiles, etc. But I just wanted ...

Seeking Advise for a Solder Reflow Recipe
The experts have spoken well, but here is just one more thing to be aware of. Assemblies going through a ...

Looking for Long-term Component Storage Options
I generally do not like to disagree with the experts, but long-term storage requirements for legacy electronic components (and actually, ...

BGA Component Grounding Problem
If you are having issues at only a single data point and the issue is lower than expected resistance to ...

Competing Reflow Oven Zones
Kind of funny none of the experts remembered the most important tip of all, the effect of loading the oven ...

Pad Missing ENIG Plating
To provide a flat pad, nickel is plated to the copper at a thickness of approximately 150 microinches (not 150 ...

BGA Solder Ball Collapse
Actually, Dr. Prasad is correct, but with two caveats;The pad diameters of both the BGA pad and the PWB pad ...

Application Using No-Clean and Water Soluble Fluxes
If you plan on washing the water-soluble PTH flux anyway, ie, washing every board in an in-line or submersible washing ...

Baking Concerns for Stacked Trays of Components
The correct standard to reference when performing bakeout of components is J-STD-033D, not J-STD-003A as was mentioned, because the question ...

Contamination From Anti-static Foam
I agree with Dr. Pauls recommendations, assuming it is not a coated CCA. However, I would follow that with an ...

What's Causing Cloudy Conformal Coating
I agree with the experts who called out moisture. Initially I was suspecting moisture in the coating itself, which typically ...

SMT Target Component Placement
All of the suggestions from the experts are worth investigation, but you may have an issue with the tolerance of ...

SMT Target Component Placement
Another factor is the surface wettability of the component leads. If they are partially oxidized then uneven wetting forces may ...

Cleaning Under Low Clearance Components
Charlie Pitary's comments are right on the money. Kyzen has saponifiers (surfactants) that enable wash water to clean under less ...

What Caused SMT Pads to Oxidize After Reflow
The "corrosion" could also be caused by improper/insufficient nickel plating (plating skips), or too long of a time between nickel ...

What Is Causing Slanted Pins After Reflow
If you have a mating connector, it is quite possible you can pull the mating sockets out and use the ...

What Is This Contamination?
I don't think I see corrosion here. Corrosion is not selective, and does not discriminate on where it wants to ...

BGA Placement Paste or Only Flux
I have used pasteless BGA and flipchip assembly processes for many, many years, with no issues whatsoever. In fact, with ...

What Is Causing Connectors to Bow?
When going through reflow, the PWB itself will bow or sag. As the board cools down from the max reflow ...

Using Solder Paste Beyond the Expiration Date
One of the most critical parts of the water-soluble flux cleaning process is to get the remaining wash water blown ...

Initial Screen Print Test Board
The experts seem to be unanimous, and I agree it is a good idea. Not only for the reasons stated, ...

Partially Visible or Hidden Solder Connections
For nearly all PTH components, there is usually some clearance between the bottom of the part and the surface of ...

Components Falling Off During Wave Soldering
I have to presume you are speaking of a buttercoating when you say the board type has a "lacquer" finish. ...

Mixed Process Solder Joint Appearance, Smooth or Grainy?
Nearly all components today have a RoHS-compliant finish. You should expect shiny well-wetted solder joints using a Sn63 solder and ...

Soldering Components with Silver Pads
Use of 2% silver solder and the shorter profile is correct. Dissolution is a self-limiting process, so if you have ...

Tough Hand Soldering Problem
For soldering to large glass panels, solar panels, diachromatic and ultrachromatic glass, aluminum panels, ceramics, and other large heatsinks I ...

Viscosity of Solder Paste Before Printing
Whatever the viscosity range listed on the Technical Data Sheet for the particular solder paste you are using should be ...

LED Component Shift During Reflow
In looking at the picture and blowing it up, I note there are many unplated holes all around these parts. ...

Copper Dissolution Rate
I am surprised nobody mentioned the original Bible for electronics soldering, Soldering in Electronics written by R.J. Klein Wassink. He ...

PCBA Inspection Process Causing Damage
Both hard and soft surfaces present their own issues, including the ability to keep one clean versus the other. The ...

What is the IPC Definition of Uncommonly Harsh?
The answers to your questions lie with your customer or end user's requirements,and not within any specification. This is because ...

Stencil Cleaning Frequency
There isn't any "standard" for the number of prints between wipes. It is up to you to determine how many ...

QFN Open Solder Joints
My suspicion is that possibly during the initial reflow, but more likely during the second reflow, row 1 (the outside ...

Gold Plating and Embrittlement
First I want to clarify that we are only talking about gold-plated component lead and terminations here, and not the ...

Cleanliness Standards for Electronic Components
Component cleanliness is "sort of" covered within the JEDEC standards, but typically they will reference MIL-PRF-STDs for component cleanliness. Two ...

Overlap Solder Joint Failures
In looking at your application for soldering two 8mm flex circuits, outsourcing this process immediately comes to mind. I would ...

Solder Paste Prep Before Use
Hello,S.S. Theseare very good questions; it is really good that you understand the importanceand have an interest in controlling your ...

ENIG Solderability Issues
The specifications you describe, 130 microinches nickel and 3 - 5 microinches gold, fits the description for electroless nickel, immersion ...

Exposed Copper Risk
When soldering the end of the chip resistor to the exposed ground plane, simply flux and solder the exposed copper ...

How Many Fiducials Per Solder Paste Stencil?
PLACEMENT fiducials are often repeated on the top and bottom PWB artwork to facilitate the Pick/Pace machine's ability to "re-zero" ...

MELF Component Misalignment
If the absence of chipbonder corrects the problem, then the only root cause I can think of is that the ...

Adhesion Problems with Conformal Coating
All of the experts have spoken well, but in addition to needing a very clean and somewhat etched surface, it ...

Contamination Using Solvent Dispensers
The experts are all correct and unanymous, do not use IPA tankards on production benches as they are really sumps ...

Class 3 Pin Contact Question
This sounds like a design issue. On the one hand, if the tinned pin was originally gold plated, the gold ...

ESD Grounding - 1 Meg Ohm Resistor
This is a good question. A1 megohm resistor allows any static charge, whether from the bench through the product and ...

Rechecking Thermal Profiles
All good inputs from the experts, but I'll add one more. When you create a profile for a given circuit ...

Challenges with 01005 Components
You may wish to consider an ionizer set-up for the pick/place machine. It helps to reduce the static buildup from ...

Soldering Station Calibration
When attempting to answer this question, I cannot bring up brand names so just let me say this: I would ...

Very Low Temp PCBs
One must not automatically assume that In100 is the ideal solder joint alloy for use in space or any other ...

Circuit Board Bow and Twist
All of the experts here had excellent and very experienced inputs. Here is one more: I recently had a PWB ...

Excess Flux Residue After Hand Soldering
In this case, the soldering appears to be on a crimped lug terminal. No flux should be allowed to wick ...

Rise of Bismuth Levels in our Solder Pots
First of all, you are correct in that J-STD-001 sets the limit for Bismuth at .25% for standard Sn60 or ...

Solder Mask Ghosting
In a previous life, I worked in the commercial sector of the industry, and have a lot of experience with ...

Test Probe Problems After Pin-In-Paste
You can use a clamp type toggle on the test fixture that comes down on the connector pins only. The ...

Blow Holes and Disturbed Joints
Bob Lazzara is probably closest to the correct answer; bake the boards per IPC-1601 by taking one PWB fresh from ...

Burned Chip Repair
There is not quite enough information, but based on the picture alone it appears as if a large blob of ...

Confused About IPC-A-610 Class 2 vs. Class 3
There should be a Contract Letter between your company and the customer. The Contract Letter or the Statement of Work ...

Concerns Replacing High Speed Components with No-Clean Solder
Yes, you should be concerned, and it is very good of you to ask rather than ignore this warning. Very-high ...

Concerns Replacing High Speed Components with No-Clean Solder
One more note regarding no-clean flux residues left on an assembly: Just because the flux is completely heated and fully ...

Selective Printing for BGA Components
I absolutely think you should go ahead and do that, and save about 3 cents per BGA in paste. What ...

What Causes Component Rotation During Reflow?
Sorry, guys, wrong again. The reason the 2-pin inductors rotate during reflow is due to their physical properties, but nothing ...

What Causes Component Rotation During Reflow?
It depends on exactly which 2-pin inductor package is being discussed. If it is a standard SMT inductor like https://www.mouser.com/ds/2/400/nductor_automotive_decoupling_klz1608-hr_en-1108665.pdf ...

How to Eliminate Via Pits
Yes, there are processes that can be used. I assume you are trying to achieve flat filled vias in the ...

Legend Marking Discoloration
The symbolization epoxy is usually initially anatase-based, which provides the brilliant definition. However, this phase changes to rutile in the ...

Pre-bake in a Vacuum
Adding a vacuum bake may reduce the time required to get to your evacuation goal slightly, but whenever baking in ...

Pre-bake in a Vacuum
One other caveat: pulling too strong of a vacuum while baking out moisture can actually cause the component body to ...

Via Wall Thickness Test
The best method is used for several of my client companies for continual monitoring of via walls and copper traces ...

Through Hole Connector Solder Joint Hole Fill
There are three methods of verifying PTH hole-fill. The first two are Visual inspection and X-ray. A third method is ...

Through Hole Connector Solder Joint Hole Fill
One other related note on the inspectability subject: Sometimes all it takes to get a minimum of 75% hole fill ...

ESD and Humidification
I am glad you made the distinction of handling completed circuit card assemblies (CCAs) into systems (box level), as opposed ...

Jumper Wire Gauge
Good answer, Leo. I would also like to point out two things. The IPC 7711/7721 standard also provides a chart ...

Component Shifting
I doubt very much that your issue is due to vibration, based on your description of the problem. I also ...

Spotting After DI Water Cleaning
You can have very clean, properly de-ionized water coming in and cleaning the soils and fluxes from your CCAs, but ...

Double Sided Reflow for Micro BGA Components
Fritz Byle has good answers. I agree with him in not trying to use IR. As far as using SAC305 ...

What Are Realistic Guidelines for PCB Flexing?
I would like to point out that the amount of warpage given in IPC-A-600 applies at the assembly (CCA) level ...

A Generic Reflow Profile
I agree with the experts that you should profile individual assemblies, but I just wanted to add that when profiling, ...

Epoxy Wicking up Wire Insulation
You don't say how many wires per circuit board, or how many circuit boards you need to do this to, ...

Dross Particles Sticking to PCBs
If the problem is not caused by flux, wave height, flux and dross entrapped in the sump, pump, or impellers, ...

Un-cleaned PCB Assemblies Potted
All of these comments are good ones, but to add to David Whalley's comment about batteries on the assembly, don't ...

Cleanliness After Coating Removal
Typically, depending on the type of CCA and the type of coating,after the coating is removed for rework and the ...

Zip-lock Bags vs. Heat Sealed Bags
No, zip-loc bags should not be used for storing MSDs, for the reasons the experts say, but also I am ...

Rework of Underfilled Array Packages
I can certainly attest to Brian Czaplicki's AirVac Engineering milling machine, having seen it in action many, many times. There ...

Silver Solder for Audio Circuits
I used to run my own Contract Electronics Manufacturing company in a previous life. As part of that I built ...

SMT Component Glue Strength
There IS a test procedure within the IPC-TM-650 standard,which is an invaluable document but yours absolutely FREE at http://ipc.org/4.0_Knowledge/4.1_Standards/test/2.4.42.pdf;available right ...

Cause of Cracking on SOT23 Components
It appears that there is some impact damage on the side of the component near the horizontal crack, although it ...

Inspection and Maintenance for Soldering Irons
From J-STD-001E: 3.9 Soldering Tools and EquipmentTools and equipment shall [DID2D3] be selected, used and maintained such that nodamage or ...

BGA Die and Pry Testing
While there is not enough info to make a sure call, I took your pictures and magnified them using a ...

Flux Aging Study
Refer to J-STD-004. This is the industrystandard for requirements for soldering fluxes, and has a lot of information oncertification, shelf ...

Conformal Coating in Low Humidity Environments
Dr. Pauls, could you expand on your answer slightly? We very much respect your knowledge on the subject of conformal ...

Conformal Coating in Low Humidity Environments
The only two downsides of coating in low-humidity environments that I can think of are also present in any humidity ...

White Discoloration After Ultrasonic Cleaning
A cleaning solvent that is chemically matched to the flux being used is required for satisfactory cleaning. It is also ...

Gold Edge Contact Flux Contamination Failures
A number of questions came up as I read about your problem. I will attempt to touch on all of ...

Gold Plated Hole Defects
Mr. Roberson is correct. I suspect you are using lead-free solder which does not wet out to the edges of ...

Glued SMT Components Falling Off
The issue is all of the above, plus a few more factors, including a combination of the material properties (CTE) ...

IPC-A-610 Criteria
In addition to the excellent comments on the historical basis of reliability testing from which Class 3 criteria evolved, let ...

Idle Wave Solder Temperature
It depends (ka-ching) on several factors.Some wave solder machines contain 1800 lbs of solder, whereas others may only hold 200 ...

Insufficient Plated Hole Fill with Electrolytic Capacitors
All of the experts have spoken; all have good suggestions to try. One simple method that often improves hole fill ...

HASL vs. Immersion Gold
Regarding Levine's comment that "Gold embrittles solder", that does NOT apply to ENIG. The gold thickness of ENIG, as defined ...

Soldering Wires to SMT Pads
The pad, trace, and the wire size are determined by thecurrent-carrying capacity required of the circuit. This is determined by ...

Solder Paste Viscosity
It is probably not a good idea. It would be better to perform the viscosity check just prior to printing, ...

CEM1 Laminate Issues
CEM1 is a paper-core material laminated with a thin layer of fiberglass. It is not usually able to withstand higher ...

OSP Poor Wetting
The reason you see it on one particular PWB part number and not other PWB part numbers is probably because ...

Wave Solder Pot Contaminated with Lead
You have all of the answers you need as to howto dilute the pot with fresh lead-free solder (and isn't ...

Contract Assembly in a Prison
Check with OK Industries, Hakko, AirVac (DRS24, DRS25or similar model). All of these companies (and others as well) have hot-gas ...

Components Jumping Out During Wave Soldering
It is not uncommon for through-hole parts to rise up out of their holes when coming into contact with the ...

Type 4 Solder Ball Use
At my client companies, we use type 4 for most products, type 3 for others, and for some special applications ...

Rework or Repair?
Gold edge contact re-plating is considered to be a Repair, not a Rework, and is detailed as such in IPC ...

3D Solder Paste Inspection
Automated solder pasteinspection (SPI)systems are very common in the U.S. and abroad. There are many companies who make SPI equipment. ...

Spec for Baking Assemblies Prior to Rework
You can completely dry any fully populated CCA at room temperature if you choose to, but there is an inverse ...

Flux Recommendation for BGA Rework
Funny you should ask! Yesterday I went with my youngest son to the local game shop to return his Xbox ...

Is Rework Unacceptable?
Well sure, if the assembly does not have any components, or else you have perfect processes and perfect operators. If ...

Solder Paste Mixing After Storage
I think this is a good practice, except for one small detail. The vendor of solder paste centrifuges recommends going ...

Uncontrolled Environment Causing Problems
Rather than repeating them here, see my response to another similar enquiry having to do with handling of solder paste. ...

Water Washing Pressure
It's hard to answer this question without knowing what the delicate parts are, and what type of circuit card assembly ...

Lead Free Reflow Oven Zone Count
From my experience, most companies are quite comfortable with a 7-zone reflow oven, which I think has been the standard ...

Batch Reflow vs. In-line Reflow
You select cleaning methods and solvent chemistry based on the flux chemistry used, right? Likewise, you select soldering processes based ...

Soldering to Hard Gold
It takes special knowledge of chemical deoxidants, entirely different kinds of solders (not alloys), and special process expertise in order ...

Application of Flux for Hand Soldering
Indeed, as all of the experts have stated,tacky flux (or gel flux)is the way to go. I did not even ...

Need for Reflow Profiles
What is lost to the "experts" in this field is that a single profile cannot work for multiple CCAs for ...

BGA Rework Flux Recommendation
Never use liquid flux for BGA rework, it will not stick around long enough, as you have discovered. As the ...

Soldering Lead-free Components with Tin-lead Solder
It is true that a homogenous alloy mix must beachieved. If you have lead-rich areas in the resultant solder joint, ...

Plating Lead Free Parts for Tin/Lead Assembly
Let me just point you to this article in CircuitsAssembly magazine. It will answer many of your questions.http://www.circuitsassembly.com/cms/magazine/207-2010-articles/9439-a-novel-process-for-automated-lead-tinning

Issues with BGA Components Near PCB Edges
There are a number of other factors to consider whenplacing BGAs closer to the edge of the PWB other than ...

Reflow oven testing and calibrating concern
Some of the advice given in this column makes sense, somedoesn't. It is true that scrap production boards are good ...

Type III vs. Type IV solder paste
All good answers. However, a word of caution. Arbitrarily switching from Type 3 to Type 4 is not a good ...

Is Pre-Bake Standard for Rework?
Sorry to those who said no, but that is incorrect. The correct answer is: it depends- on a lot of ...

How Many Zones Needed for a Lead-free Profile?
what do you mean "For REWORK you need a minimum of 4 independent top and bottom zones for heating and ...

How Many Zones Needed for a Lead-free Profile?
What do you mean "For REWORK you need a minimum of 4 independent top and bottom zones for heating and ...

Control Electronic Static Discharge
As Leo has so wisely pointed out, do not assume that all portions of any machine are grounded through the ...

Proper method to bake PCB's
Dr. Toleno and president Lazarra are both correct. Refer to IPC-1601, it completely covers PWB bake-out, methods for determining optimum ...

Cleaning PCB Boards with window cleaner?
Window cleaner? How visionary! Does it help you find shorts inside the PWB? Do you also use a squeegee? Looking ...

Books or Publications of today's electronics assembly
You may wish to consider taking the SMTA's class for certification in SMT Assembly. It would quickly provide you a ...

Tombstone problems
Most likely the culprit is an imbalance of wetting between the two pads on each end of the component, caused ...

Tombstone problems
A couple of other comments I would like to add: 1. If you are using Type 3 paste, switching to ...