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What does NBP's Chemical Milling
Solution do?
NBP has a
proprietary chemical milling solution for cleaning zinc die cast
based parts. This solution is a chemical bath and does not
require electrical current. It will remove the zinc oxide layer
and prepare the part for plating. It can clean out cold shut
areas, remove minor flash, debris and burrs. Our normal chemical
mill removes .0003" - .0006" of material but can be increased to
about .001". The advantages of Chemical Milling is that a thin
layer of zinc oxide or carbonate deposited over a pure zinc die
cast surface is removed and the potential for casting blisters
can be eliminated. This also allows for high temperature
applications without the casting blisters to appear under the
intermetallic stresses that are formed from the copper plate.
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Preclean: A two step process to remove most synthetic,
petroleum, vegetable, and animal based fluids used in
die-casting and machining operations.
Mill: A controlled removal of the outer layer of
die-cast. This process can remove flash, surface die-cast
blisters, and modify dimensions if necessary. This step is
essential to improve the adhesion of the subsequent copper
plating.
Copper Strike: The copper strike is a specially
formulated copper solution designed to provide excellent
adhesion to the die-cast surface. The thickness of the strike is
approximately 50 millionths of an inch.
Copper Plate: The copper plate seals the zinc to protect
it from environmental exposure. Also, copper is used to modify
dimensions. After the minimum thickness is achieved, we often
add more copper to build dimensions. A thick, continuous copper
plate is essential to protect the part from subsequent plating
solutions which are corrosive to raw zinc.
Final Plate: After copper plating, the parts may safely
be plated in nickel, tin, EN, etc.
What is the difference between an
Electrolytic & an Electroless Bath?
Unlike conventional electrolytic nickel, no electrical current
is required for deposition of Electroless Nickel. The
electroless bath provides a deposit that follows all contours of
the substrate exactly, without building up at the edges and
corners. A sharp edge receives the same thickness of deposit as
does an internal diameter.
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Do you have any Black
Finishes?
NBP has a variety of Black Finishes (in order of
increasing cost)
NBP's Econo Black - NBP's own formulations - This
molybdate black goes directly on zinc die cast. After the
molybdate coating is applied, the parts are submerged in a seal
composed of chromates and phosphates that enhance the salt spray
resistance of the coating. An organic coating, water dip
lacquer, is applied as a final coat to protect the finish and
improve appearance.
Zinc & Black Molybdate - Similar to Econo Black, but this
molybdate black is applied over a bright zinc plate to yield a
glossy, plastic like black finish. The corrosion characteristics
can be improved with a seal and/or lacquer as required.
Black Electroless Nickel - Parts are Electroless Nickel
plated and then blackened to give a metallic brown / black
appearance. This coating is used for a variety of applications
from color identification to eye appeal.
Black Electrolytic Nickel - ULTRA CONDUCTIVE - This
finish is not as intense as the Zinc & Black Molybdate but has
excellent eye appeal, yet this finish in contrast to the other
black finishes is very conductive. This coating was developed
for automotive applications where conductivity and low
reflectivity are important.
Why would I find Black Spots on Tin & Tin/Lead Plating?
Fretting is a common
problem with Tin Plating. This is surface damage created when
there is relative motions and strong contacts between parts,
usually during shipping and handling. The tin plating shows
black or worn spots caused by rubbed or scratched by another
part. This oxide does not effect the parts functionally. They
are still solderable. A way to eliminate fretting is by changing
the type of packaging. (Layer packing or plastic trays are
recommended) - Metal Finishing Guidebook 1997
Are there many problems associated with Tin Plating?
There are
many problems associated with tin plating. One of which is
whiskering, like cadmium and zinc, thin needle-like crystals
known as "whiskers" form within a period after plating that may
vary from a few weeks to several years. A whisker may measure up
to .0001" (2.5um) in diameter, and grow spontaneously to a
length of 0.375" (10 mm). Conditions that tend to promote the
growth of whiskers are compressive stresses and uniform
temperatures for long periods of time. In most applications,
these slender microscopic crystals would be unnoticed and
harmless, but in closely spaced electronic circuits they are
capable of carrying sufficient current at low voltages to cause
serious short circuits or a corona discharge.
When the formation of whiskers is known to be a potential
problem, the condition may be prevented by specifying that a
small amount of lead be included in the tin deposit. While 1-2%
lead is adequate to substantially reduce the risk of whiskering,
it is customary to specify a 93% tin - 7% lead alloy to assure
that the alloy remains sufficiently high in lead under all
conditions of electroplating to prevent the formation of
whiskers. Small quantities of antimony, copper or nickel in the
tin deposit have also been reported to prevent the formation of
whiskers.
What finishes
are good for soldering?
The most
widely used finishes for soldering are Tin, Tin/Lead & Gold.
What is electroplating?
Electroplating is a process
by which metal in ionic form migrate from a positive to a
negative electrode. An electrical current passing through the
solution causes objects at the cathode to be coated by the metal
in solution. The size, shape and weight of the objects being
plated determine how they will be plated.
Electroplating is done to protect, beautify, insulate or
increase the corrosion resistance, conductivity, or
solderability of metal objects. It demands as much skill as any
modern endeavor. Platers immerse objects into a variety of
chemical baths in order to change their surface condition.
Regardless of the finish being applied, the parts must be
"surgically" clean.
What
precious metals are used in electroplating?
Precious metals commonly used in electroplating and surface
finishing operations include gold, silver, indium, ruthenium,
palladium and rhodium. Factors that influence the selection of
precious metals are their contact characteristics, corrosion
resistance, heat resistance, reflectivity, solderability, color
and wear resistance.
Silver has an advantage of its relative low cost, but it is
susceptible to tarnishing when exposed to sulfur in the
atmosphere.
Gold has excellent solderability and electrical characteristics.
The hardness and appearance of gold can be modified with
different alloying elements.
Indium is a precious metal that has the unique quality of cold
fusing at room temperature with aluminum and copper. This cold
welded bond keeps out oxidation between the indium plated part
and the aluminum or copper base material allowing for excellent
electrical and thermal transfer contacts. This coating is the UL
approved finish for connecting aluminum wiring to a copper
receptacle.
What is Pickling &
Acid Dipping?
Metals can be immersed into solutions of acids to remove metal,
metal oxides, heat-treat scale, and foreign metals. Such
treatments generally leave the surface chemically clean and
ready for further processing. The general process is to solvent,
emulsion, or alkaline clean the parts prior to acid immersion,
so that the acid solutions will wet and/or etch uniformly.
Common Plating/Casting
Issues
Blisters (Bumps / Bubbles / Pimples / Pockets) - A thin sac
containing liquid, air, or diecast particle on or near the
surface.
Corrosion / Black Spots / Fretting - Discoloration of the
surface
Cracks - A linear discontinuity in the metal surface which
fractures the material.
Exposed Base Metal - Metal is exposed due to lack of any plating
(This condition can be verified at up to 10X magnification with
Microscope lighting.)
Flaking - A separation of peeling of plating.
Flash - Excess casting material at parting lines.
Foreign Material - Excess material such as tumbling media or
pieces of sprue or gate wedged into the part.
Incomplete Fill/Nicks - Holes that are deeper than the skin of
castings.
Slivers - A long thin piece of casting or plating.
How do I go
about getting a quotation?
All we need is a blueprint or description of the part, finish
specification (see Capabilities), tolerance or thread that
should be monitored and quantity.
Email -
Click Here
Fax - (732) 846-9779
Mail - 1010 Jersey Ave. New Brunswick, NJ 08901
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Copyright © 2013 - New Brunswick Plating, Inc. All Rights
Reserved.
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