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Plating anomalies and defects, Part 1: plating defects can have multiple origins, so don't jump to conclusions.

It is a good idea to begin this month's edition of Positive Plating by presenting a few different plating defects and discussing some of the possible causes and remedies rem·e·dy  
n. pl. rem·e·dies
1. Something, such as medicine or therapy, that relieves pain, cures disease, or corrects a disorder.

2. Something that corrects an evil, fault, or error.

 to resolve the problem. Many of these defects have multiple origins. Defects can be the result of multiple problems throughout the manufacturing process, and this may not manifest manifest 1) adj., adv. completely obvious or evident. 2) n. a written list of goods in a shipment.

MANIFEST, com. law. A written instrument containing a true account of the cargo of a ship or commercial vessel.
 in the process where the defect defect - bug  actually occurred. When trying to identify the root cause of a defect, it is often best to not jump to conclusions. Not understanding a defect's true genesis will lead to incorrect Incorrect means to not be correct and may also refer to:
  • Politically incorrect
  • Incorrectly formatted data, a computer error
See also
  • Correctness
  • Anomalously numbered roads in Great Britain
  • Disputes in English grammar (Incorrect English)
 remedies to these issues. I will discuss some defects and possible remedies.

Blisters (Hole-Wall Pullaway)

The common complaint one hears is, "The copper plating Copper plating is the process in which a layer of copper is deposited on the item to be plated by using an electric current. Three basic types of processes are commercially available based upon the complexing system utilized.  is peeling." Ok, but where is it peeling from, off of the copper surface or from within the via? What about the interconnect (1) To attach one device to another.

(2) A physical port (plug, socket) or wireless port (transmitter, receiver) used to attach one device to another.
? Is the peeling layer the electroless copper deposit or the electrolytic e·lec·tro·lyt·ic
1. Of or relating to electrolysis.

2. Produced by electrolysis.

3. Of or relating to electrolytes.

 copper? These are the questions one must answer in order to properly trouble shoot the defect. FIGURE 1 shows a real-life real-life  
Actually happening or having happened; not fictional: a documentary with footage of real-life police chases. 
 example of a blistered or peeling deposit. The copper deposit has actually flaked off or blistered from the hole. In some cases, the deposit does not completely flake off Verb 1. flake off - come off in flakes or thin small pieces; "The paint in my house is peeling off"
peel, flake, peel off

chip, chip off, break away, break off, come off - break off (a piece from a whole); "Her tooth chipped"
 the surface, but instead, pulls away from the hole wall. This condition is referred to as hole-wall pullaway (HWPA).

Now the question is where is the origin of the blister blister, puffy swelling of the outer skin (epidermis) caused by burn, friction, or irritants like poison ivy. A response of the body to protect deeper tissue, blisters generally contain serum, the liquid component of blood. ? In this case, the good news is that we are only looking at the electroless copper. There has yet to be an electrolytic copper deposit applied to the circuit board, but that is all one can tell at this point.

A more typical example of HWPA is depicted de·pict  
tr.v. de·pict·ed, de·pict·ing, de·picts
1. To represent in a picture or sculpture.

2. To represent in words; describe. See Synonyms at represent.
 in FIGURE 2. The deposit pulled away from the hole-wall but did not fracture fracture, breaking of a bone. A simple fracture is one in which there is no contact of the broken bone with the outer air, i.e., the overlying tissues are intact. In a comminuted fracture the bone is splintered.  or flake off. Nonetheless, this is a defect and must be remedied. The root cause of HWPA is very similar to those that lead to flaking and blistering blis·ter·ing
See vesiculation.

So, one is dealing with the origin of the blister or peeling deposit prior to electrolytic copper plating. TABLE 1 lists the most common causes for this type of defect. Further information about the hole wall condition can be determined by a careful review of the microsection or through SEM analysis.

Keep in mind that there is no substitute for process control. All of the operators should have a basic understanding of why certain processes must be controlled within the stated limits. This will go a long way in preventing costly rejects.



MICHAEL CARANO is global manager for strategic business development at OM Group, Inc. and can be reached at
TABLE 1. Common causes of NWPA.

Cause                            Look at

Excessive catalyzation           Dwell times, temperatures

Smooth topography on resin       * besmear process not able to
                                 produce a topography
                                 * excessive solvent penetration
                                 * Insufficient rinsing after
                                 cleaner/conditioner step
                                 * Inadequate etching of the
                                 resin-poor topography

Electroless copper deposition    * Check rate coupons-is dep
rate too                         rate higher than normal?
high                             * Check operating temperature
                                 of electroless copper
                                 * Check concentrations of the
                                 key additives-copper, sodium
                                 hydroxide, HCHO, stabilizer

Cause                            Remedy

Excessive catalyzation           Reduce time and temperatures
                                 in catalyst

Smooth topography on resin       * Review resin type-higher Tg
                                 resins are more difficult to
                                 desmear-excessive lamination
                                 temperatures and cure
                                 times over cross link material.
                                 * Make sure cleaner conditioner
                                 is free-rinsing--consider
                                 reducing concentration
                                 and dwell times
                                 * Measure weight loss of the
                                 test coupons after Besmear

Electroless copper deposition    * Check specific gravity of
rate too                         electroless copper solution
high                             --solution bail-out to bring
                                 specific gravity in range
                                 * Reduce operating temperature
                                 * Analyze and adjust
                                 concentrations to recommended
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Author:Carano, Michael
Publication:Printed Circuit Design & Fab
Date:Jun 1, 2009
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