Conductive EMI/RFI Shield Coating Market Information Manual Presented by: The Sherwin-Williams Company
Chemical Coatings Conductive EMI/RFI Shield Coating Market Information Manual Presented by: The Sherwin-Williams Company Conductive EMI/RFI Shield Coating Market Information Manual Compiled by The Sherwin-Williams Company, Chemical Coatings Division & Acheson Colloids Company The Sherwin-Williams Company Chemical Coatings Division - Marketing 101 Prospect Avenue N.W. Cleveland, Ohio 44115 05/05 Table of Contents Introduction…………………………………………………………………….…1 Purpose of Shielding & Trends……………………………………………....2-4 Shielding Methods & Comparisons………………………………...………5-14 Features of Conductive Shield Coatings……………………….……..…15-23 (includes application and reclamation information) How Do You Sell EMI/RFI Shield Coatings?…………………………..……24 Generic Conductive Material Selection Information………………….…25-26 Acheson Shield Coatings & Selector Guide…………………………..…27-35 Competitive Product Cross Reference& Comparison……………….....36-37 Electrical Resistance Test Methods for EMI Coating Processes…...…38-42 UL Approval Support…………………………………………………….…….43 Frequently Asked Questions…………………………………………...…44-46 Trouble-Shooting Guide………………………………………………...…47-48 Glossary……………………………………………………………….....……..49 05/05 Introduction This manual was compiled for the purpose of providing a hand-held reference guide on the EMI/RFI shield coating market; a market that represents an estimated 8 million dollars in coating sales annually. This manual is intended to educate and provide a level of confidence in the sales and service of EMI/RFI shield coatings. The manual is laid out in a presentation format in an effort to keep the subject material simple and concise as possible. Please refer to the Glossary for abbreviation explanations. It is our hope that after reviewing this manual you will have a better understanding of EMI/RFI shield coatings and the EMI/RFI shield coating marketplace. 1 05/05 What is the Purpose of Shielding? ¾ Protection of Essential Communication ¾ Allow Operation in Electrically Hostile Environment ¾ Control Interference Between Electronic Devices ¾ Data Leakage Containment 2 05/05 Areas of Use ¾ Telecom • cellular, base station, relay stations, wireless loop, satellite dishes, antennas ¾ Office Equipment • computers, fire alarm systems, PDA’s, disk drives ¾ Medical • X-ray, IV dispensing, blood counters ¾ Military • headphones, night scopes, radio systems 3 05/05 Conductive Coating Trends ¾ Increasing use in telecommunications • mobile phones, digital set-top boxes, & satellite dishes ¾ Best alternative for notebook computers • thin wall housings, higher frequencies ¾ Silver paints increasingly suitable for higher frequencies (>1 GHz) ¾ Silver plated copper blends reaching higher conductivity levels 4 05/05 How Do You Shield? ¾ Metal ¾ Plating ¾ Vacuum Metalization ¾ Conductive paint ¾ Metal Cans ¾ Foils/Inserts 5 05/05 Technology Market Share Cans Inserts Foils Plating Metal Paint Vacuum 05/05 6 Theoretical Shielding Performance (Flat Panels) ¾ Conductive Coating - 65-85dB ¾ Electroless Plating - 85-100dB ¾ Vacuum Metalization - 85-100dB 7 05/05 Shielding Type Comparison Attenuation (dB) 100 80 60 Silver Paint Vacuum Copper Paint Electroless 40 20 10 100 Frequency (MHz) ¾ Specific enclosure ¾ Prior to humidity 8 05/05 1000 Electroless Cu/Ni Plating ¾ Pro • Highly conductive • Excellent shielding performance ¾ Con • • • • Requires strict process control Decorative paints adhere poorly Selective plating is expensive Disposal of plating effluents 9 05/05 Vacuum Metalization ¾ Pro • Highly conductive • Excellent shielding performance ¾ Con • Requires strict process control • Expensive special tooling and large number of masks required • Limited number of sites world wide • Heat of application can warp thin walls 10 05/05 Conductive Coatings ¾ Pro • Numerous applications sites world wide • Very little seam leakage • Low VOC coatings available • Low cost (no need for high volume for low cost, price will go lower with more volume) ¾ Con • • • • Coating thickness from 0.5-1.5 mils Slightly lower dB Not as good abrasion resistance Need top coat in humid area 11 05/05 Adhesion to Plastic Aluminum Deposition Electroless Coating PC PC/ABS PPO/PS ABS 12 05/05 Applied Price Comparison Electroless $3.75/ft2 Paint (silver) $2.74/ft2 Paint (silver plated copper) $1.50/ft2 2 Vacuum Deposition $2.90/ft 13 05/05 Resistance vs Film Thickness Electrical Resistance versus Dry Film Thickness 0.35 Indicates optimum dry film thickness 0.3 Resistance (ohms/square/mil) 0.25 0.2 SP-017 Coating 0.15 SP-029 Coating 0.1 SP-027 Coating 0.05 0 0 0.5 1 1.5 Coating Thickness (mils) 05/05 14 2 2.5 Application Equipment Costs ¾ Robot Spray Line - $250,000 ¾ Plating Line - $1,000,000 ¾ Aluminisation Line - $1,000,000 15 05/05 Features of the Resin Bonded Coating Process ¾ Low cost equipment investment ¾ Easy application by robotic or automatic spray ¾ Excellent shielding performance depending on coating formulation (silver, silver plated copper, nickel, graphite) ¾ Better contact in mating enclosure parts ¾ Excellent mechanical properties (adhesion, abrasion resistance) ¾ Excellent environmental stability (humidity, heat, thermal shock) 16 05/05 Thin Wall Housing ¾No caused by heat or chemicals when using the correct conductive paints 17 05/05 Comprehensive Selection ¾ Nickel Coating ¾ Silver-plated Copper Coating ¾ Silver-plated Copper plus Silver Coating ¾ Silver-Nickel Blend Coating ¾ Silver Coating 18 05/05 Product Categories ¾Solvent base • • • • Quick dry Thin film build Ready for Use (RFU) and concentrates Low VOC using alcohol or acetone ¾Water-base • Low VOC 19 05/05 Shield Coating Types Attenuation (dB) 100 Ag Ag/Cu 80 Ni 60 40 20 10 100 Frequency (MHz) 20 05/05 1000 Application Techniques of Conductive Coatings ¾ Spray • Conventional (manual) • Conventional (automatic) » Siphon » Pressure fed » Pressure fed ¾ Airless ¾ HVLP • Factory Air • Turbine Fed Air ¾ Brush 21 05/05 Actual Coating Coverage ¾ Conventional Spray Methods 10-30% • Suction • Pressure Fed ¾ High Volume Low Pressure 65-85% • Most efficient • Robotic systems ¾ Airless Spray Methods 70-85% 22 05/05 Reclamation ¾Sources • Mask Washer • Paint Booths Filters/Walls ¾Value in Metals Reclamation • Copper, Silver-coated Copper • Nickel • Silver 23 05/05 How Do You Sell EMI/RFI Shield Coatings? It’s easy! Ask these simple questions: 1) Do you currently spray functional shield coatings? If yes, go to #3 If no, go to #2 2) Do you ever get asked to spray functional shield coatings? If yes, go to #3 If no, report as “No Opportunity” 3) What type of coatings and what quantities do you use? If necessary, for sales and technical support, contact your regional Acheson representative for joint follow-up. 05/05 24 What Type Of Conductive Material Do I Use? ¾ Nickel • • • • Medium resistance material @0.9 ohms/sq. Applied at 2.5 mils dry film thickness Attenuation >65 dB Oldie but still widely used (different diluent available per substrate) ¾ Silver-Plated Copper • • • • • Low price Excellent for new electronics Applied at 1.0-1.5 mils dry film thickness Resistance from 0.100 to @0.045 ohms/sq. @ 1mil Attenuation of >75 dB 25 05/05 What Type Of Conductive Material Do I Use? ¾ Silver/Nickel • • • • • Low price Excellent for new electronics Applied at 0.4 to 1.0 mils Low resistance 0.020 ohms/sq.@ 1 mil Attenuation 85 dB ¾ Silver • • • • Low resistance at thin film @0.015 ohms/sq. Applied at 0.3 to 1.0 mils High shielding protection, thin film for close tolerances Attenuation 85 dB 26 05/05 Electrodag® 456 ¾ Nickel Pigment ¾ Thermosetting Acrylic Binder System ¾ Excellent Adhesion To Metal ¾ 1.000 ohms/sq/mil Typical Resistance ¾ 65 dB Shielding Performance ¾ 991 ft2/gal @ 1 mil ¾ 3.00 lbs/gal VOC 27 05/05 Electrodag® 550 ¾ Nickel Pigment ¾ Acrylic Binder System ¾ Excellent Adhesion To Plastic ¾ 0.900 ohms/sq/mil Typical Resistance ¾ 60 dB Shielding Performance ¾ 422 ft2/gal @ 1 mil ¾ 5.47 lbs/gal VOC 28 05/05 Electrodag® SP-017 ¾ Silver-Coated Copper Pigment ¾ Acrylic Binder System ¾ Excellent Adhesion To Plastic ¾ 0.075 ohms/sq/mil Typical Resistance ¾ 75 dB Shielding Performance ¾ 295 ft2/gal @ 1 mil ¾ 6.03 lbs/gal VOC 29 05/05 Electrodag® SP-029 ¾ Silver-Coated Copper Pigment ¾ Urethane Blend Binder System ¾ Excellent Adhesion To Plastic ¾ 0.030 ohms/sq/mil Typical Resistance ¾ 75 dB Shielding Performance ¾ 168 ft2/gal @ 1 mil ¾ 6.12 lbs/gal VOC 30 05/05 Electrodag® SP-027* ¾ Silver Pigment ¾ Urethane Blend Binder System ¾ Excellent Adhesion To Plastic ¾ 0.015 ohms/sq/mil Typical Resistance ¾ 75 dB Shielding Performance ¾ 340 ft2/gal @ 1 mil ¾ 5.06 lbs/gal VOC * Available, but not covered under distributor agreement. 31 05/05 Electrodag® SP-008A ¾ Silver-Coated Copper Pigment ¾ Acrylic Latex Binder System ¾ Excellent Adhesion To Plastic Or Metal ¾ 0.250 ohms/sq/mil Typical Resistance ¾ 75 dB Shielding Performance ¾ 450 ft2/gal @ 1 mil ¾ 2.74 lbs/gal VOC 32 05/05 Electrodag® SP-019* ¾ Silver Pigment ¾ Urethane Blend Binder System ¾ Excellent Adhesion To Plastic ¾ 0.015 ohms/sq/mil Typical Resistance ¾ 75 dB Shielding Performance ¾ 552 ft2/gal @ 1 mil ¾ 1.13 lbs/gal VOC * Available, but not covered under distributor agreement. 33 05/05 Electrodag® 18DB70X* ¾ Silver-Nickel Pigment ¾ Acrylic Binder System ¾ Excellent Adhesion To Plastic ¾ 0.015 ohms/sq/mil Typical Resistance ¾ 75 dB Shielding Performance ¾ 320 ft2/gal @ 1 mil ¾ 0.50 lbs/gal VOC * Available, but not covered under distributor agreement. 34 05/05 ® E le c tro d a g E M I/R F I S h ie ld in g M a te ria ls S e le c tio n G u id e E le c tro d a g c o n d u c tiv e c o a tin g s a re d e s ig n e d to p ro te c t e n c lo s e d e le c tro n ic d e v ic e s a g a in s t ra d ia te d e le c tro m a g n e tic in te rfe re n c e a n d e le c tro s ta tic d is c h a rg e . O u r E le c tro d a g c o a tin g s h a v e b e e n e x p e rtly fo rm u la te d u s in g v a rio u s c o n d u c tiv e p ig m e n ts to a c h ie v e o p tim a l p e rfo rm a n c e in e le c tric a lly h o s tile e n v iro n m e n ts a n d a s s is t th e d e s ig n e r to c o m p ly w ith e m is s io n s re g u la tio n s w o rld w id e . P ro d u ct P ig m e n t B in d e r D ilu e n t* T y p ic a l R e s is ta n c e o h m s /s q /m il VOC lb s /g a l T h e o re tic a l C o v e ra g e S q ft/g a l @ 1 m il S h ie ld in g P e rfo rm a n c e (d B ) R e c o m m en d e d S u b s tra te s If re q uire d , d ilute to u s e r’s n e e d s 1 .0 0 0 3 .0 0 991 65 M e ta l D ilu tio n R a tio (b y v o lu m e ) (p ro d u c t:s o lv e n t) SOLVENT BASE E le c tro d a g 4 5 6 N ic k e l T h e rm o s e ttin g A c ry lic M A K or M E K E le c tro d a g 5 5 0 N ic k e l A c ry lic S B -1 , S B -8 , o r S B -1 0 1 :0 .8 ra tio 0 .9 0 0 5 .4 7 422 60 P la s tic s E le c tro d a g S P -0 1 7 S ilv e r-c o a te d Copper A c ry lic M E K , S B -1 2 :1 ra tio 0 .0 7 5 6 .0 3 295 75 P la s tic s E le c tro d a g S P -0 2 9 S ilv e r-c o a te d Copper U re th a n e B le n d A lc o h ol B le n d 3 :1 ra tio 0 .0 3 0 6 .1 2 168 75 P la s tic s E le c tro d a g S P -0 2 7 S ilv e r U re th a n e B le n d A lc o h ol 1 :1 ra tio 0 .0 1 5 5 .0 6 340 75 P la s tic s E le c tro d a g S P -0 0 8 A S ilv e r-c o a te d Copper A c ry lic L a te x W a te r R e a dy for u s e 0 .2 5 0 2 .7 4 450 75 E le c tro d a g S P -0 2 8 S ilv e r-c o a te d Copper A c ry lic W a te r R e a dy for u s e 0 .1 0 0 3 .0 2 362 75 P la s tic E le c tro d a g S P -0 1 9 S ilv e r U re th a n e B le n d W a te r R e a dy for u s e 0 .0 1 5 1 .1 3 552 75 P la s tic E le c tro d a g 1 8 D B 70 X **V O C E X E M P T S ilv e r A c ry lic A c eto n e 1 :1 ra tio 0 .0 1 5 0 .5 0 320 75 P la s tic s LOW VOC * S o lv e n t b le n d s m a y b e c h a n g e d fo r s p e c ific p la s tic a n d e n v iro n m e n ta l c o n ditio n s . S B -1 is fa s t d ry in g an d is a ls o u s ed fo r to u g h to b ite in to p las tic s u rfa c e s ; S B -8 is m e d iu m d ry in g a n d c a n b e u s e d fo r ge n e ra l p urp o s e p la s tic s ; S B -1 0 is th e s lo w e s t d ry in g a n d us e d o n s o lv e n t s e n s itiv e p la s tic s . If blu s h in g o r d ry s p ra y o c c u r a dd u p to 5 % o f d ia c eto n e a lc o h o l o r bu ty l a lc oh o l P la s tic o r m e ta l. A ls o A rc h itec tu ra l Uses E le c tro d a g m a te ria ls a re U L re c o g n iz e d p e r U L 7 4 6 C fo r a d h e s io n to c o m m on ly u s e d p la s tic s fo r e n c lo s u re a p p lic a tio n s . F o r m o re d e ta ils o n s p e c ific U L ap p ro v als c on ta c t A c h e s o n C o llo ids C om p a n y a t 1 -8 0 0 -25 5 -1 9 0 8 . ** T h is p ro d u c t w a s fo rm u la te d u s in g m a te ria ls th a t h a v e b e e n c la s s ifie d a s e x e m p t b y th e U n ite d S ta tes E n v iro n m e n ta l P ro te c tio n A g e n c y . It is re c o m m e nd e d th a t b e fore us in g th is p rod u c t, y o u c o n ta c t y o u r lo c a l a n d s ta te re g u la to ry a g e n c ie s fo r c on firm a tio n . 05/05 35 Competitive Product Cross Reference Acheson Electrodag ® Spraylat 456 and 550 None SP-017 Y2000 SP-008A Z3000 SP-029 Y2000 or B3755 36 05/05 Coating Integrity Cohesion Comparison ¾ Competitive brand does not exhibit good cohesive strength ¾ UL tests for adhesive and cohesive integrity ¾ OEMs recognize coating integrity as critical at seams and ground points Electrodag 37 05/05 Brand S Measurement of Electrical Resistance Forward Measurement of electrical resistance during the processing of EMI coatings can be confusing, especially when comparing numbers to the paint manufacturer’s method. The following paragraphs describe current industry standards, make suggestions for proper electrical resistance testing methods and explain the ohm/square/mil method. Conclusion Point-to-point resistance results are dependant on many factors including size, shape, geometry of the part, distance between the points, film thickness and type of substrate. For this reason, suppliers typically supply ohms/square/mil levels for their coatings as this data is obtained under controlled test conditions. Because the profile of the part to be coated will be different for each OEM, it is impossible to be able to state what the point-to-point resistance will be for any given part. The industry instead provides ohm/square/mil data so that end users can compare products for electrical resistivity properties. The customer is urged to use Versatronic® probes in a meter capable of reading 0.001ohm. This enables point-to-point readings over long distances and at 1 cm spacing for tight space checks (side walls, etc.) and in the ohm/square/mil method described below. It is essential that coaters monitor film thickness, degree of cure and conductivity on a daily basis to ensure optimum coating performance and control costs. 05/05 38 Measurement of Electrical Resistance Current Industry Standards There are two methods for measuring electrical resistivity: point-to-point, which is used for QC purposes and ohms/square/mil which should be used for comparing one product to another. The most common and easiest resistance measurement is point-to-point testing performed by simply touching ohmmeter probes to the painted surface. Locations of the probes are agreed upon between the OEM and coater. Drawbacks of this method, which affect resistance values, include uncontrolled normal force (pressure applied), sharpness of the probes and oxidation of the probes. While point-to-point is a good and necessary practice, it should be accompanied by film thickness and ohm/square/mil monitoring. 05/05 39 Electrical Resistance Test Method for Sprayed Electronic Coatings 4-PROBE ELECTRICAL RESISTANCE TEST METHOD FOR SPECIAL JIG SCOPE: To determine the dry film electrical resistivity of conductive coatings. EQUIPMENT: 1. Ohmmeter with low resistance capability that can accept four leads. 2. Special compression contact jig for measuring the electrical resistivity of a 1” X 3” area of coated surface. METHOD: 1. A product to be tested for electrical resistance should be applied to a suitable substrate (most commonly a glass plate or GE Lexan panel) measuring 3” in width and a minimum 4” in. length. The coating needs to be properly cured before testing. If the coating is applied onto a glass panel this same panel can be used to measure dry film thickness after resistivity has been recorded. If the coating is applied onto plastic, a glass slide (typically a 1” X 3” microscope slide) needs to be fixed onto the back of the panel, partially exposed, in the area where resistivity will be measured (see diagram #1) NOTE:Identification of application method, cure, dilution ratio, if any, and recommended film thickness can be found on the Product Data Sheet. 2. Product application for this test can be by spray or drawdown technique, as specified on the Product Data Sheet. If drawdown technique is used, it must be performed on glass substrate to accurately measure dry film thickness. 05/05 40 Electrical Resistance Test Method for Sprayed Electronic Coatings 3. A one-inch wide section should be scribed into the cured coating. This can be done using a 1” X 3” standard microscope slide. Be certain that the scribe goes completely through the coating. 4. The electrical resistance of the coating can then be tested using the special jig and the ohmmeter. The ohmmeter must accept four leads to eliminate lead resistance failures. Ensure the leads from the inner probes are wired to the source input on the ohmmeter and the outer probes are wired to the sense input of the ohmmeter. Before performing actual resistance measurements, check the electrical resistance specifications of the product being tested and set the ohmmeter at an appropriate scale. 5. Once the meter has been properly adjusted, insert the coated test panel into the special jig ensuring the scribed area is lined up with the contacts. There is a red painted area on the jig for this purpose. 6. Obtain and record the electrical resistance reading from the ohmmeter. 7. Measure the thickness of the coated glass slide using a micrometer. The measurement must be done in an area where the electrical resistance was made (see diagram #1). Remove the coating using a razor blade (in the same area the initial thickness measurement was made) and determine the thickness of the glass slide with the micrometer. Subtracting the thickness of the glass slide from the thickness of the glass slide and coating will give the thickness of the coating. 8. The electrical resistance is expressed in units of ohms per square inch at a thickness of 0.001 inch (one mil). This is possible since the compression contacts on the electrical resistance jigs are one inch apart 41 05/05 Electrical Resistance Test Method for Sprayed Electronic Coatings 9. To calculate the electrical resistance, multiply the obtained electrical resistance by the film thickness of the coating. This will give an electrical resistance value normalized to a thickness of 0.001 inch. Diagram #1 Area where resistivity will be measured Glass Slide Back (Uncoated) Front (Coated) 42 05/05 Tape UL Approval Support For a current list of UL approved companies, contact Chemical Coatings Marketing in Cleveland 43 05/05 Frequently Asked Questions Q) How much diluent can I use to make the coating go farther? Does it matter which solvent I use to dilute the product with? A) Dilutions in excess of the recommended amounts can help with such things as blushing, dry spray, and laying down lower film builds. However, there is a fine line as to the amount that can be added before performance properties such as resistance and cohesion are affected. If additional diluent is necessary to enhance application properties I would recommend no more than four additional ounces per gallon for concentrated products and no more than six additional ounces per gallon for ready-for-use products. Except to compensate for blushing or dry spray, I would always recommend the products be diluted and applied per the directions on the Product Data Sheet. The diluent used must be compatible with the other ingredients in the formulation to avoid plugging of the gun, poor wetting of the coating, poor adhesion, high resistivity, and other possible problems. Follow the Product Data Sheet to determine the proper diluent. If the proper diluent is not available contact either Technical or the assigned Application Specialist for advice on a suitable replacement. Q) What type of equipment do I need to apply these coatings? A) Because of their metal conductive pigment, EMI shielding coatings do not stay in suspension for very long (anywhere from 2 minutes to 20 minutes before settling). Recommended application equipment includes a sealed pressure pot with agitation, a pump to move material to the gun and back to the tank, and pressure regulators to control fluid and atomization levels. With the material under constant agitation in the pressure pot and constantly recirculated from the pot to the gun and back, settling out of the pigment can be eliminated. We recommend the use of a HVLP type spray gun because of the high transfer efficiency it has over conventional spray guns. Also, we recommend just enough agitation in the pressure pot to keep the material moving. Avoid creating a vortex that can bring excessive air into the product, interfering with proper application and film thickness, especially with water-based coatings. 05/05 44 Frequently Asked Questions Q) Are there special storage requirements with these coatings? A) Yes. Water-based coatings should not be stored in freezing temperatures (below 32F). Freezing waterbased coatings will change the properties of the resin and the material may be unusable. Solvent-based coatings should be stored below 90F. Storing solvent-based coatings above 90F will shorten the shelf life of the material. Q) When I open a new container do I need to use all of the material or can I repackage the product for later use? A) Coatings containing silver-coated copper as the conductive pigment should only be opened once or twice before the product is used up. The repeated exposure of these coatings to fresh air results in rapid oxidation of the copper in the product, resulting in poor resistivity. Other pigmented coatings can be reopened several times with minimal effect on the product. However, excessive headspace should be avoided to prevent solvent loss. Q) Is there a preferred method of mixing these products before application? A) Use of a paint shaker is preferred over blade mixers for two reasons. One, with a paint shaker the container does not need to be opened and exposed to the atmosphere, preventing evaporation of any volatiles, maintaining solids content. Two, there is less likelihood of excess amounts of air getting mixed into the material. Trapped air can interfere with the proper application and performance properties of the coatings, especially the waterborne materials. 05/05 45 Frequently Asked Questions Q) How can I tell if the coating is thoroughly cured? A) The best method of testing cure is to measure resistivity of the coating. While recording time and temperature, measure resistance point to point at specified locations. Resistance readings will significantly decrease as the coating cures. This decrease will end when the coating is cured. The temperature and time should be recorded for future reference as to proper cure conditions. Note: Established cure conditions are dependent upon dried film thickness. If the film thickness increases or decreases, the time and temperature necessary for proper cure will have to be reestablished. Q) Can EMI shielding coatings be topcoated? A) Yes. The resin systems used in these coatings are easily adhered to by most decorative and protective coatings. However, there will be an increase in resistivity when conductive coatings are topcoated that will need to be compensated for. 05/05 46 Troubleshooting - Coating Appearance P rob lem C ause S olution C oating blisters d uring cure 1) C oating applied too heavy 2) C oating applied too w et 3) Insufficient flash tim e before oven cure T o avoid blisters, it is m ost im portant to apply the m aterial so as to avoid too heavy and/or too w et of a film . If the coating is applied too heavy or w et, blisters m ay be avoided by increasing flash tim e. C oating cracks after cure S olvent attack on the substrate 1) C hange application technique to apply the coating drier by increasing the atom ization air and/or decreasing the volum e of m aterial. 2) A dd a sm all am ount of either D iacetone A lcohol, B utyl C ellosolve or S B -10 solvent (<4 ounces/gal). 3) R ecom m end a less aggressive coating, either w ater or alcohol based to be sued on solvent sensitive substrates. 4) A pply a thin coat, flash, then apply norm al layers. The thin coat w ill act as a barrier upon flashing, protecting the substrate. C oating is rou gh like sandp ap er D ry spray 1) C hange gun settings to increase feed and/or decrease atom ization air 2) C hange application technique by decreasing gun distance from part and/or slow ing gun speed 3) A dd sm all am ount (<4ounces/gal) of slow solvent (B utyl C ellosolve or D iacetone A lcohol) G rit in product from previously opened container S train product through 40-60 m esh filter. B lushing B lushing occurs w hen coatings containing fast solvents are applied in high hum idity conditions. To m inim ize blushing, add a sm all am ount of either B utyl C ellosolve or D iacetone A lcohol (< 4ounces/gal). C oating has w hite surface 05/05 47 Troubleshooting - Performance Properties Problem Resistance readings are higher than they should be. Coating exhibits poor cohesion in tape test. Coating exhibits poor adhesion in cross-hatch tape test 05/05 Cause Solution 1) Insufficient film build Be sure the coater has a method of measuring dried film thickness. Recommend using a glass microscope slide attached somewhere on the part that can be removed and film thickness then measured with a micrometer after the coating is cured. If the dried film thickness is less than recommended, check the container for undispersed solids. If the material was mixed uniformly, adjust gun settings to achieve proper film build. 2) Insufficient Cure If the degree of cure is suspect, place a coated part into any available oven at the recommended cure time and temperature. Once the coating has properly cured, retest for resistance. 3) Product is past shelf-life. Check the lot number to determine if product has exceeded shelf-life. 1) Poor application technique If the coating was applied too wet, cohesive failure can result due to settling of the pigment onto the substrate, leaving a resin rich-layer on top. This results in poor pigment-to-binder ratio on the bottom, where cohesive failure will occur. If the coating was applied too dry, the atomized droplets were not able to flow together and are easily pulled apart. Dry spray will also be evidenced by a rough, sandpaper-like surface. 2) Older generation EMI coating. Some older EMI coatings were formulated with low resistivity as the main criteria. To accomplish this, pigment to binder ratios were increased, trading cohesion for resistance. (Example: SP-010) If cohesion is an issue with a new project with EMI coatings, check with technical for recommended coatings that excel in this area. Contaminated surface or inappropriate substrate/coating combination The substrate needs to be free of any dirt, oils and mold release compounds before coatings will adhere. There is a UL listing available for our coatings and the substrates on which they are approved. 48 Glossary ABS Ag Cu dB - Decibel Acrylonite Butadiene Styrene Plastic* Silver Copper A numerical expression of the relative differences in power levels of electrical signals equal to ten times the common logarithm of the ratio of the two signal powers. Used in electronic, radio. Electromagnetic Interference One billion hertz The international unit of frequency, equal to one cycle per second One million hertz Nickel Unit of electrical resistance Polycarbonate Plastic* Polyphenoleneoxide Plastic* Polystyrene Plastic Radio frequency interference Shielding plastics EMI Ghz - Gigahertz hertz Mhz - Megahertz Ni Ohms PC PPO PS RFI SP *Reference Sherwin-Williams’ Plastic Selector Guide, Dyment #2004538 05/05 49
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