Listed below are case studies discussing problem resolutions that Foresite has participated in.  Some case studies were published in Circuits Assemblies; others have been published in various locations. All links are to PDF documents.

Case studies published in Circuits Assembly:

White Residues - Are They or Aren't They? (01.2006)

When it comes to white residues, a defect is not always a defect.

Know Your Sources (02.2006)

When it comes to contaminants, what you do not know can hurt you.

No Silver Lining (03.2006)

Sulfate contamination causes visible silver crystalline growth.

Stray Voltage on Low Standoff Components (04.2006)

The Doctor diagnoses an acute weak organic acid problem.

Not-So-Fine Debris (07.2006)

Left uncleaned, even staging racks can be a source of failures.

The Downside of Selective Soldering (08.2006)

If not cleaned, pallets can leave harmful residues.

What's My Risk? (09.2006)

Determining the root cause of a field failure.

Does Electronics Really Have a Surface Contamination Problem? (02.2005)

As field mounts return, our answer is yes!

Environmental Chamber Cleanliness is Critical (03.2005)

Environmental screening can only be effective if equipment is clean and in control.

Localized Contamination, Big Problems (04.2005)

Localized ionic residues can be overlooked by bulk ionic testing methods.

Destructive Testing for Reconstructing Processes (05.2005)

Cross sectional analysis is sometimes necessary in order to detect specific types of cracks and stresses.

Mean Green Corrosion (07.2005)

Selective soldering on ImAg boards built with a no clean process can be a very touchy situation.

Keep It Clean! (08.2005)

Environmental chamber cleanliness has a direct impact on product performance.

On a Flat Note (09.2005)

Flat leadless PQFN package traps flux from no-clean solder paste leaving a gooey, conductive residue that was causing product field failures through electromigration.

Escape Artist (10.2005)

Design changes involving a standoff allow for flux trapped under PQFN  to volatilize and escape.

Clean It Up! (11.2005)

Incoming bare board & component cleanliness is crucial in building reliable product.

Let it Flow (12.2005)

A short reflow profile causes flux entrapment under low standoff components.

The Key to Success (03.2004)

Examine key parameters for a successful no-clean assembly.

Is White Residue a Reliability Risk? (07.2004)

This case examines a visible white residue and explains how to determine whether or not a white residue is detrimental.

Activate That Flux (09.2004)

The importance of full heat activation of fluxes to prevent the deposition of weak organic acid (WOA) flux residues is exemplified in this case study.

Good Bonds Take Time (11.2004)

Inadequate reflow profiles cause weak joints and flux residues.

Understanding Specific Area Cleanliness (12.2004)

Ionic contamination can cause a wide array of failures.  This article shows pictures of many such failures.

Can You Clean a No-Clean Assembly? (01.2003)

Yes, you can clean a no-clean assembly!

Component Cleanliness in a No-Clean World (03.2003)

With a no clean assembly process, the component, board and assembly flux are critical variables that must be understood and controlled.

Understanding Selective Pallet Soldering Residue (09.2003)

Proper heating can eliminate flux concerns.

Low Battery (11.2003)

Localized screening tests help pinpoint the cause of battery leakage failures.

Dark Conductive Residues (03.2002)

Examining the impact of sulfur contact on copper traces.

Finding Residue Sources - Part I (05.2002)

Finding residue sources in PCBs using Six Sigma techniques.

Finding Residue Sources - Part II (08.2002)

Use the Six Sigma inter-ocular test to find residue sources in PCB fabrication.

Other cases studies we have written:

Solderability Problems:  Both Residue & Thermal Conditions

Higher thermal mass boards require close examination of soldering profiles and solder deposition.

Ventilation Condensation

The cleanliness of environmental chambers has a direct impact on product performance.

Leakage, Leakage Everywhere
In this case study, we examine the effects of surface and absorbed fabrication residues on an assembler's operation.

Garbage In = Garbage Out
In this case study, we examine the effects of elevated bromide from the fabrication process on an assemblers qualification process.

The Crystalline Entity
In this case study, we examined detrimental residues present in a water-soluble flux assembly process.

What, Me Worry About Fumes?
Low solids fluxes are finding increasing usage around the world. The cost savings afforded by the elimination of the cleaning operation is often attractive, but the world of no-clean fluxes has many dangers to the uninformed.

The Mask From Hell
A manufacturer of a low-end commercial product was experiencing a wide spread failure during burn in testing. The failure mechanism was excessive leakage currents and an almost instantaneous metal migration situation.

Remedial Cleaning of the Mask From Hell
This is a follow-on to Case Study, The Mask From Hell.

When A Cool Flux Should Be A Hot Item
In this study, we were working with an assembler who was attempting to qualify a hand soldering process to J-STD-001 A, Appendix D and F guidelines.

Talk About Being Canned
In this study, we were attempting to help an assembler track down the cause of extensive corrosion on a printed wiring assembly.

But I'm Wearing Finger Cots!
Every once in a while it is good to examine assumptions you (or your management) have made in your manufacturing process. This case study involved handling residues.

I Could Solder to Concrete
In this study, we see what can happen when you use an active flux totally outside of the manufacturers recommendations.

Peelable Mask, Unpeelable Residues
In this study we examine the effects of temporary processing materials, in this case a peelable latex temporary solder mask.

That Darn Casting
In this study we examined outside factors which were causing circuit failures during power temperature cycling (burn-in acceptance test).

Pop, Sizzle and Fry
In this study we examined the cause of laminate blistering in aqueous cleaned assemblies.

Doing Everything Right and Still Fail Qual Testing?
In this study the assembler was examining different combinations of conformal coatings and OA fluxes, using qualification guidelines of MIL-STD-2000A, Appendix A.

Just Call Me Fireproof
In this study we examine the effects of high levels of bromide residues on circuit boards, and how much bromide is a hazard.

I'm Surprised You Have Any Leads Left!
This is a case study involving component manufacturing and the residues involved.

Just Crank Up the Pressure
We look at a study in cleaning that focuses on two misconceptions: (1) that you get better cleaning by increasing the spray pressures; and (2) that global board extractions will always tell you if you have a contamination problem.

Sure Hope We Don't Get Caught
We love this line of work. We get to see all different kinds of manufacturing processes, some done exceptionally well, and some done exceptionally bad.

What a Difference a Little Soap Makes
Anyone who has small children can tell you that if you want to get the kids clean after a day of playing, water alone will not do it.

On the Average, I'm OK
In this case study we look at a problem concerning corrosion, metal migration, and electrical leakage, potentially affecting over 100,000 assemblies (field and inventory) with more produced every day.

Bare Board Roulette
This is the second of a two-part study. In part 1 (March 1998), assemblies experienced high levels of corrosion, electrical leakage and metal migration.

We're All Fed Up
Every once in a while, when doing failure analysis, it becomes necessary to try to recreate a failure mechanism in order to determine the base problem.

No More Than I Have To
Anyone with a teenager is occasionally amazed at the effort put forth to avoid work.

It Always Works for the Repairman
One of Murphy's Laws says that any broken appliance will always work when demonstrated for the repairman.
 
Parts Per Part
We love site visits. It gets us out of the everyday routine and exposes us to different cultures.
 
Microcanyons
Nearly all electronics assemblers make some sort of surface mount or mixed technology assembly.

A Problem with Teflon Insulation
Most of us consider polytetrafluoroethylene (PTFE or Teflon) as a fairly inert or benign material.

Sulfate in Vias II
In a previous column, we examined the problem that an assembler was having with high levels of sulfate remaining in small diameter (less than 3 mils) vias. In this case study we continue examining sulfates in vias.

Residues vs. SIR
In considering whether an assembly is considered as "acceptable", there are two basic schools of thought.

White Residue - Good or Bad - Part 1

This case looks at how different water qualities and cleaning chemistries affect the appearance of white residues and the cleaning effectiveness of BGAs.

White Residue - Good or Bad - Part 2

The second part of this case talks about how many white residues are conductive but not corrosive, and often come from un-cleaned flux reacting with water or soldermask absorbing cleaning chemistry.