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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.
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 ...
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 ...
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) ...
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 ...
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 ...
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 ...
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 ...
Analog Technologies Corp.
In this case, the soldering appears to be on a crimped lug terminal. No flux should be allowed to wick ...
Need for Reflow Profiles
What is lost to the "experts" in this field is that a single profile cannot work for multiple CCAs for ...
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 ...
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 ...
Tombstone problems
Most likely the culprit is an imbalance of wetting between the two pads on each end of the component, caused ...
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 ...
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 ...
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 ...
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 ...
Rechecking Thermal Profiles
All good inputs from the experts, but I'll add one more. When you create a profile for a given circuit ...
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 ...
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 ...
Legend Marking Discoloration
The symbolization epoxy is usually initially anatase-based, which provides the brilliant definition. However, this phase changes to rutile in the ...
Wave Soldering System Nitrogen Use
If your wave soldering system came with a nitrogen inerting option, it should have a flowmeter somewhere on the nitrogen ...
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 ...
What is the IPC Definition for Uncommonly Harsh?
The answers to your questions lie with your customer or end user's requirements, and not within any specification. This is ...
Soldering Lead-free Components with Tin-lead Solder
It is true that a homogenous alloy mix must be achieved. If you have lead-rich areas in the resultant solder ...
QFN Open Solder Joints
My suspicion is that possibly during the initial reflow, but more likely during the second reflow, row 1 (the outside ...
Stencil Cleaning Frequency
There isn't any "standard" for the number of prints between wipes. It is up to you to determine how many ...
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 ...
Reflow Oven Testing and Calibrating
Some of the advice given in this column makes sense, some doesn't. It is true that scrap production boards are ...
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 ...
Overlap Solder Joint Failures
In looking at your application for soldering two 8mm flex circuits, outsourcing this process immediately comes to mind. I would ...
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 ...
Solder Paste Prep Before Use
Hello, S.S. These are very good questions; it is really good that you understand the importance and have an interest ...
Issues with BGA Components Near PCB Edges
There are a number of other factors to consider when placing BGAs closer to the edge of the PWB other ...
ENIG Solderability Issues
The specifications you describe, 130 microinches nickel and 3 - 5 microinches gold, fits the description for electroless nickel, immersion ...
MELF Component Misalignment
If the absence of chipbonder corrects the problem, then the only root cause I can think of is that the ...
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 ...
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 ...
ESD Grounding - 1 Meg Ohm Resistor
This is a good question. A 1 megohm resistor allows any static charge, whether from the bench through the product ...
Soldering Station Calibration
When attempting to answer this question, I cannot bring up brand names so just let me say this: I would ...
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 ...
Concerns Replacing High Speed Components with No-Clean
Yes, you should be concerned, and it is very good of you to ask rather than ignore this warning. Very-high ...
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 ...
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 ...
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 ...
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 ...
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, ...
Solder Paste Life on the Stencil
The printing process you describe is the one most commonly used in most electronics assembly factories today. Dispense paste on ...
Plating Lead Free Parts for Tin/Lead Assembly
Let me just point you to this article in Circuits Assembly 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 ...
Cleanliness After Coating Removal
Typically, depending on the type of CCA and the type of coating, after the coating is removed for rework and ...
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 ...
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 ...
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; ...
Inspection and Maintenance for Soldering Irons
From J-STD-001E: 3.9 Soldering Tools and Equipment Tools and equipment shall [DID2D3] be selected, used and maintained such that no ...
Wave Solder Pot Contaminated with Lead
You have all of the answers you need as to how to dilute the pot with fresh lead-free solder (and ...
Flux Aging Study
Refer to J-STD-004. This is the industry standard for requirements for soldering fluxes, and has a lot of information on ...
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 ...
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 ...
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 ...
Soldering Wires to SMT Pads
The pad, trace, and the wire size are determined by the current-carrying capacity required of the circuit. This is determined ...
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 ...
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 ...
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 ...
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. ...
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 ...
Water Washing Pressure
It's hard to answer this question without knowing what the delicate parts are, and what type of circuit card assembly ...
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 ...