Conformal Coating Removal Study

Transcription

1 Conforma Coating Remova Study

2 CONFORMAL COATING REMOVAL TECHNIQUES Why use Conforma Coating? Conforma coatings are thin ayers of synthetic resins or pastics that are appied to eectronic devices for protection against a variety of environmenta, mechanica, eectrica and chemica probems, such as: Humidity and moisture Fungus and midew Dust and dirt Apha partices Stress Mechanica shock and vibration cycing Corrosion Process sovents, fues, hydrauic fuids, other fuids Adds Dieectric strength Whie most conforma coatings are used on printed circuit boards (PCBs), they are aso used to protect discrete components, such as transistors, diodes, rectifiers, resistors and LED s; integrated circuits (ICs); and hybrid circuits, incuding muti chip modues (MCM) and chip on board (COB). Types of Industries that use Conforma Coatings Originay deveoped for miitary, aerospace, and marine appications, conforma coatings are now finding widespread use in teecommunications, industria contros and instrumentation, consumer eectronics, and the automotive industries. A appications in which product reiabiity and protection are of primary importance. Types of Conforma Coatings Currenty six major types' conforma coating chemistries are avaiabe: Epoxy Acryic Urethane Siicone Paryene Page 2 of 21

3 Utravioet cured materias We recenty took a survey of our Industry contacts and found the foowing percentages for usage of conforma coating types: Urethane 62% Siicone 47% Acryic 45% Epoxy 37% Paryene 21% Others 11% The percentages equa more than 100% because severa companies are using more than one type of conforma coating. The miitary specification for coating printed circuit assembies, MIL , recognizes 5 types of conforma coatings: Type AR (acryic) Acryics are easy to appy conforma coatings that are not that resistant to abrasions and chemicas. Type ER (epoxy) Epoxies are fairy easy to appy and very hard to remove. Type SR (siicone) Siicone conforma coatings are for high temperature environments. Type UR (urethanes) Poyurethane s are the most popuar conforma coatings, offering humidity, chemica and abrasion protection Type XY (paryene) Paraxyyene is a vacuum deposited conforma coating. They offer exceent resistance to humidity, moisture, abrasion, high temperatures and chemicas. Utravioet Cured Materias In the eary 1980s, when reguations started to be appied against voatie chemicas, an immediate need existed for sovent ess conforma coating materias. Conforma Coating manufacturers responded by deveoping utravioet (UV) curabe conforma coatings. This heped eiminate air poution and save energy by no onger requiring drying or curing after coating. Sovents were successfuy deveoped from epoxy acryates, urethane acryates, and poyester acryates. Utravioet (UV) cured materias are aso recognized, but are not isted as a separate group. They are incuded within the above five categories. Whie each of these coating types exhibits properties that make it the best choice for a particuar appication, specia attention shoud be paid to the techniques used for their remova. Page 3 of 21

4 The Remova of Conforma Coatings Now et's take two exampes of what can happen. 1. You are a manufacturer of PCB Assembies. You have just finished your production run and your engineering department comes down to the production foor and has a mandatory change that requires you to repace 2 components, on 500 boards. 2. You are a repair organisation and you need to make contact with components in abe to functionay test them and diagnose the fauts on the board. What technique are you going to use? Luckiy you have severa options avaiabe to you. They incude therma, mechanica, chemica and abrasive. Again, we recenty took a survey on the different techniques used by the companies and the resuts were: Chemica 62% Mechanica 53% 32% Abrasive 28% Again, the percentages equa more than 100% because peope are using different techniques to remove the conforma coating. The therma remova technique (incuding using a sodering iron to burn through the conforma coating) is the east recommended technique of coating remova. Most conforma coatings require a very high temperature and/or ong exposure times. This, in turn, can cause discooration, eave residues, and adversey effect soders and/or other materias used in the construction of the board or its components. remova can cause the ifting of surface mount pads from boards. Aso, temperature sensitive components may be damaged. Extreme caution must be taken when burning through conforma coating because some coatings emit very toxic vapours that are hazardous to the peope doing the stripping and those around them. Mechanica Mechanica remova techniques incude cutting, picking, sanding or scraping the area of coating to be removed. However, most of the conforma coatings are very tough and abrasion resistant, making the probabiity of damage to the board very high. Page 4 of 21

5 Chemica Unti a few years ago, chemica remova techniques were the most popuar techniques for the remova of conforma coatings without adversey affecting the board or its components. However, there is no one perfect sovent for a appications, and in some cases no sovent wi be suitabe at a. Of course, the first probem faced by anyone who must remove a conforma coating is determining the composition of the coating that is to be removed. If information concerning the nature of the coating is not incuded in the product iterature, the ony recourse is to contact the manufacturer and ask. Choosing a Sovent When choosing a sovent for the remova of a particuar conforma coating, you shoud examine the foowing criteria: 1. Does it quicky and competey remove the coating? 2. Does it seectivey remove the coating whie not damaging or adversey affecting the substrate and/or other components or devices? 3. Is it safe to work with? 4. Is it environmentay acceptabe? Since reguations vary not ony from country to country, but aso from company to company, the answer to some of these questions can ony be determined by the individua company. Abrasive (Conforma Coating Remova Workstations) The first machines used for conforma coating remova were sma sandbasting machines that were originay designed for meta deburring and etching 2. Litte or no consideration was given to the inherent probem of eectrostatic discharge (ESD). How a Conforma Coating Remova Machine Works Basicay, a cutting media is introduced into a compressed air stream and ejected through a hand hed nozze. This is directed at a component on a printed circuit board that has a conforma coating appied to it that you want to remove. Cutting Media s In the beginning, different types of cutting medias were offered to customers but no extensive testing or concusions were given to industry because the manufacturers of the sandbasting equipment made most of their profits on seing cutting media. Bioogica media such as wheat starch and wanut shes had the best resuts for stripping the conforma coating but had very high generated ESD votages, in some appications higher than 25,000 vots at point of contact. (Note: Point of Contact is were the cutting media strikes the board). Sma sandbasters wi remove the conforma coating from Page 5 of 21

6 printed circuit boards with efficiency. However, there are severa things you shoud be concerned about before you decide to use this technique. Types of Cutting Media The right type of cutting media goes aong way in eiminating the ESD probem. There are severa types of cutting medias avaiabe, some of them ESD friendy and others are not. The correct media is the one that wi best do the job for your appication and not be ESD unfriendy. Auminium oxide is a very aggressive media that can cut right through a printed circuit board. Typica ESD reading range for auminium oxide is in the 500v to 1,000 vot range. Bioogica medias (wheat starch and wanut shes) are not as aggressive as auminium oxide but they usuay eave a residue that must be ceaned off prior to re coating. These medias are not ESD friendy with votage eves exceeding 25,000 vots in many cases. Sodium bicarbonate is a popuar media but it generates high ESD eves and it aso must be thoroughy ceaned off the board before reappying a coating. There are severa types of pastic cutting medias avaiabe. These have the owest ESD generated eves, if formuated correcty, and they are aso recycabe. The ESD Probem Conforma coating remova machines have an inherent probem. They generate static eectricity. They can t hep it; it s the nature of the beast. As you probaby aready know, ESD wi ki the board you are trying to repair uness you take extreme care. Tabe 1 shows the ESD votage eves that wi cause damage to individua component types. Tabe 1 Reported Susceptibiity Ranges of Various Devices Exposed to Eectrostatic Discharge From a Person or Eectronic Equivaent 3 Device Type ESD Susceptibiity Votage Range VMOS 30 1,800 MOSFET GaAsFET EPROM 100 JFET 140 7,000 SAW OP AMP 190 2,500 CMOS 250 3,000 SCHOTTKY DIODES 300 2,500 FILM RESISTORS (THICK, THIN) 300 2,500 BIPOLAR TRANSISTORS 380 7,000 ECL 500* 1,500 Page 6 of 21

7 SCR 580 1,000 SCHOTTKY TTL 1,000 2,500 * PC board eve Soving the ESD Probem Because conforma coating remova machines are static generators, the different manufacturers or conforma coating remova systems have taken severa different approaches to soving the ESD probem. Some manufacturers insta AC or DC pused ionizer bars in the work chamber as a modification and soution. The main concern with these ionizer bars is they can go out of adjustment and thus have to be continuay adjusted to remain within specifications. One manufacturer has instaed a point ionizer on the end of their nozze to try to dissipate any static charge buit up in the media stream at point of contact. Another manufacturer has taken an entirey different approach to the ESD probem. This different approach begins in the media stream were the ESD is generated. By incorporating the atest technoogy, in ine, auto baanced ionizer, the media fow path changes. By spitting the air source, with one air path going to the media chamber and the other going to the in ine ionizer, the ionized air is injected into the media stream just before it eaves the nozze. This eiminates the static charge buit up in the media chamber. The ionized air is aso pumped into the work chamber. With this system, ESD readings are typicay in the ±10v range. Techniques vs. Type of Coating In the foowing sections, we wi expore the different conforma coating type by the different remova techniques for each. We wi aso discuss the differences between spot remova and removing the conforma coating from the entire board and try to determine the time it wi take for each. Finay, we wi expore the cean up requirements for each. Poyurethane s Offering good dieectric properties, with exceent humidity, abrasion, and chemica resistance, poyurethane conforma coatings are the most cost effective and widey used coatings. This is the one area you DO NOT want to use the therma or burn through technique. Poyurethane s wi emit a toxic gas that in time wi cause great damage to your empoyees. Mechanica Because poyurethane is so hard after it sets up, this technique is not recommended. Damage to the board most ikey wi occur. Chemica Currenty avaiabe for remova of poyurethane coatings are severa sovents that provide a wide range of speed and seectivity that can be matched to a specific appication. Page 7 of 21

8 These sovents incude: methano base / akaine activator sovents, which are the sowest and most seective; other methano base / akaine activator sovents that are somewhat faster acting and are the most popuar; and ethyene gyco ether base / akaine activator sovents, which are the fastest and east seective. Compete remova of the coating is accompished by immersion of the board into the sovent at room temperature. The amount of time required for coating remova wi vary with the sovent being used, the particuar coating used, and coating thickness. Typicay, most poyurethane coatings of inch thickness can be removed in one to three hours. The use of utrasonics or any agitation of the sovent wi hep to reduce the time required. The board shoud be removed from the sovent periodicay; if it has a miky white appearance, coating remova is not yet compete, and it shoud be returned to the sovent. Occasionay, ight brushing or wiping may be required to remove any ast traces of coating. To be certain that no residue remains from either the coating or the sovent, it is extremey important that the board be thoroughy washed in acoho (isopropano or methano) immediatey after coating remova is compete. The board may then be rinsed with deionised (DI) water and dried. Because a of these sovents contain sma amounts of ionic materias, it is advisabe to test the rinse water for ionic contamination with a conductivity meter. If you ony need to remove a sma area of the conforma coating to get at a few components or circuit traces, you can use a spot remova technique to remove poyurethane conforma coatings. In this case, you use a higher viscosity, or ge, form of the sovent, and appy it with a brush, cotton pad or cotton tipped swab. A of the sovents discussed here are avaiabe in ge form for spot remova. The foowing tabe shows information for the chemica remova for poyurethane. Poyurethane Thickness Sovent Approx. Time for Remova Conap CE See Note Hours Conap CE Hours Conap CE Hours Conap CE 1165, 1166 * Conap CE Hours Furane 5750 A/B(LV) * Furane 5750 A/B * Humisea 1A20, 1A33, 1A34, * 2A64 Hyso PC18M, PC29M * Products Research PR1568 * * = No time study done Note 1 2 types of chemicas recommended Methano Base/Acid and Ethyene Gyco Ether Base/Akaine activator. Abrasive (Workstations) The use of workstations for the spot remova of poyurethane is exceent. Because of its hardness, this technique of remova ends itsef to this appication. If a thickness of.004 is maintained, to remove the coating from an individua component wi take ess than 1 Page 8 of 21

9 minute. If the thickness of the poyurethane any greater than.004 the ony thin sacrificed is another minute or two. Remova Time Technique Spot Remova Whoe Board Again, do use this technique, it s deady N/A Mechanica Depends on the thickness and ski of the Don t even try. operator Chemica Care must be used. Masking may be required. Wi sti take about an hour The best if removing coating from the entire board. Abrasive Fastest and easiest Depends on the thickness of the coating. Cean up Mechanica Chemica Abrasive N/A Don t use this technique for poyurethane s. If attempted, itte cean up is required uness board is damaged. Messy, foow EPA reguations. Depends on media type used. If pastic, no cean up, others wi require further ceaning. Siicone Siicone conforma coatings offer high humidity, corrosion, and therma resistance, which make them the preferred choice for high temperature appications. Siicones caim to fame is for high temperature appications. The sodering iron technique is aso a high temperature appication. Use caution and watch the fumes. Consut with the manufacturer before using this technique. Mechanica Because siicones are normay more eastic than other types of coatings, this technique can be used with some success. Just remember, cutting and scraping can damage the board. Chemica Over the past severa years, chemica companies have deveoped sovents that are somewhat effective in removing siicone conforma coatings. Of these, the fastest and most popuar is a methyene choride based system. Severa hydrocarbon based sovents are aternatives to the methyene choride based sovent. If dissoving just a sma spot is a concern, you can use the sower but far more seective hydrocarbon based sovents. These Page 9 of 21

10 sower sovents wi not attack epoxy gass PC boards, their components, metas or other pastics. Whie not as fast as the methyene choride, the hydrocarbon based sovents are more seective, and when not contaminated by water, wi not attack epoxy gass PCBs, their components, metas and most pastics. As in the case of the poyurethane s, the coated board is immersed in the sovent at room temperature and aowed to stand unti the siicone has dissoved or can be easiy brushed off. The time required wi vary with the sovent used, the type of siicone coating, the coating thickness, and the amount of surface area exposed. Typicay, most coatings of inch or ess wi be removed in 15 minutes to one hour. Certain chemicay resistant siicones may require extended immersion for severa hours. The use of utrasonics or agitation wi reduce dissoving time. After coating remova is compete, it is very important that the board be thoroughy washed in acoho (isopropano or methano), then rinsed in DI water and dried. A saturated coth or cotton tipped swab may be used for spot remova. Repeated appications and brush may be necessary. Some of the newer siicones wi not come off with any form of chemica. Make sure you check with the manufacturer before you use any chemicas on newer siicones. The foowing tabe shows information for the chemica remova for siicone. Siicone Thickness Sovent Approx. Time for Remova Chemtronics Konform.003 See Note Minutes Conap CE Minutes Dow Corning 3140/3145 * RTV Dow Corning Minutes 1 Hour Dow Corning UVI * Dow Corning Hipec Minutes Dow Corning Hipec Minutes to 24 Hours Dow Corning Hipec Minutes Dow Corning * Dow Corning UVI * Dow Corning * Dow Corning UVI * Dow Corning R * GE SR Minutes GE ECC 440, 450 * W.R. Grace Amicon SC 120 * 4 WR Grace Amicon SC 3613 * WR Grace Amicon SC 930 * * = No time study done Page 10 of 21

11 Note 2-2 types of chemicas recommended - Methyene Choride Base/Acid and Hydrocarbon Base/Acid. Abrasive (Workstations) Using conforma coating remova workstations to removing siicone up to.020 thickness is extremey easy, especiay the newer siicones. Oder siicones with a thick appication can be time consuming because the media wi bounce off the siicone. Remova Time Technique Spot Remova Whoe Board Watch the fumes. Don t even try. Mechanica Depends on the thickness and ski of the Don t even try. operator Chemica Care must be used. Masking may be required. Wi sti take at east 15 minutes. Most feedback is negative. Soak time must be watched or damage wi occur. Fifteen minutes to overnight soak required. Abrasive Fastest and easiest in most cases, especiay with newer siicones. Depends on the thickness of the coating. Cean up Mechanica Chemica Abrasive Messy. Litte if any. Messy, foow EPA reguations. Depends on media type used. If pastic, no cean up, others wi require further ceaning. Acryic Acryic conforma coatings have good humidity resistance, ong pot ife, and are reativey easy to appy. However, they have poor abrasion and chemica resistance. This seems to be the most popuar way to get through acryic conforma coating. Caution must me used when using any burn through technique however. Consut the manufacturer before you use this technique. Mechanica Acryic is scraped off easiy, if not appied too thick. Damage to the board is very possibe. Chemica In the past, chemica remova of acryic coatings was done with highy voatie or fammabe sovents such as methyene choride, trichoroethane, aromatics or ketones. Many Page 11 of 21

12 of these chemicas are no onger acceptabe due to physica hazards, toxicity, or environmenta reguations. A reativey safe aternative based on butyroactone has been deveoped for remova of acryic conforma coatings. Most typica acryic coatings wi be removed within one hour after soaking in this sovent. After remova is compete, the PCB shoud be rinsed with acoho or DI water, and then dried. The foowing tabe shows information for the chemica remova for acryics. Acryic Thickness Sovent Approx. Time for Remova Conap CE Butyroactone 1 Hour Base Conap CE Hour Furane Acnane 5730 * Humisea 1B31, 1B31 66, 1B31 * FR Humisea 1B73 * Hyso PC20M * Hyso PC20 35M * * = No time study done Abrasive (Workstations) Extremey easy to take off, even to strip off a whoe board. Remova Time Technique Spot Remova Whoe Board Quick and efficient, how safe it is depends Don t even try. on the operator. Mechanica Quick and efficient. Care must be taken not Don t even try. to damage the board. Chemica Care must be used. Masking may be required. Wi sti take at east one hour. Soak time must be watched or damage wi occur. Most feedback is negative. Abrasive Fastest and easiest. Very fast compared to any other technique. Cean up Mechanica Litte if any. Litte if any. Page 12 of 21

13 Chemica Abrasive Messy, foow EPA reguations. Depends on media type used. If pastic, no cean up, others wi require further ceaning. Epoxy Epoxy conforma coatings provide good humidity, chemica, and abrasive resistance. Use extreme caution when burning through epoxy. Though no known gas is emitted, check with the manufacturer before you use this technique. Mechanica Because epoxy is so hard, this technique is not recommended. Damage to the board most ikey wi occur. Chemica Compete coating remova for repair is neary impossibe by chemica means (except in the case of hermeticay seaed hybrids), as the sovent can't discriminate between the epoxy coating, the epoxy gass printed circuit board, and any epoxy coated or potted components. However, if done carefuy, spot remova of the coating may be accompished by the appication with a cotton tipped swab of a sovent with a methyene choride base and acid activator. The foowing tabe shows information for the chemica remova for epoxies. Epoxy Thickness Sovent Approx. Time for Remova A Types Methyene Choride Base/Acid For Spot Remova ONLY Abrasive (Workstations) The use of workstations for the spot remova of epoxy is exceent. Because of its hardness, this technique of remova ends itsef to this appication. If a thickness of.004 is maintained, to remove the coating from an individua component wi take ess than 1 minute. Remova Time Technique Spot Remova Whoe Board Unknown, depends on thickness of coating. Don t even try. Mechanica Depends on the thickness and ski of the Don t even try. operator Chemica Don t even try. Don t even try. Abrasive Fastest and easiest. Labour intensive. Page 13 of 21

14 Cean up Mechanica Chemica Abrasive Litte if any. Litte if any. N/A Don t use chemicas with epoxy coatings. Depends on media type used. If pastic, no cean up, others wi require further ceaning. Paryene Paraxyyene conforma coating, or paryene, is appied by a vacuum deposition process. They offer exceent resistance to humidity, moisture, abrasion, high temperatures and chemicas. Can be done easiy. Mechanica Care must be taken. Chemica The coated board shoud be immersed in a tetrahydrofuran base sovent for a period of two to four hours. This wi cause the paryene coating to separate from the board. Rinse the board in acoho and et dry; then physicay remove the coating with tweezers. The foowing tabe shows information for the chemica remova for paryene. Thickness Sovent Approx. Time for Remova Paryene.001 Tetrahydrofuran 2 4 Hours Base Abrasive (Workstations) Paryene is the easiest coating to remove by this technique. For spot remova, it is recommended that you mask the area you were to strip. This wi give you a nice cean edge when you reappy the paryene. Remova Time Technique Spot Remova Whoe Board Very good. Don t even try. Mechanica Very good but care must be taken. Don t even try. Page 14 of 21

15 Chemica Don t even try. Don t even try. Abrasive Fastest and easiest. Fastest and easiest. Cean up Mechanica Chemica Abrasive Litte if any. Litte if any. Don t use chemicas. Depends on media type used. If pastic, no cean up, others wi require further ceaning. UV Cured Materias The passage of strict environmenta aws drasticay reducing voatie organic compound (VOC) emission eves created a widespread need for a sovent ess conforma coating. Consequenty, the eary 1980's saw the deveopment of utravioet ight (UV) curabe conforma coatings as a way to eiminate air poution, significanty reduce processing time, and reduce energy costs as compared to sovent based, thermay cured coatings. These coatings were successfuy deveoped by creating acryated oigomers: epoxy acryates, urethane acryates, poyester acryates, or combinations of severa of them. Depends on the type of UV coating. Not recommended by manufacturers. Possibe out gasses by most of these coatings. Mechanica Most UV coatings act ike a cross between poyurethane and acryic. Thickness of the appication wi determine if this technique shoud be used. Chemica Epoxy acryates provide improved chemica resistance. Acryated urethanes are fexibe and tough. However, because of the "hybrid" chemica structure of these UV cured conforma coatings, chemica remova can be a itte more compicated. Whie two different manufacturers' coatings may be of the same type of oigomer, for exampe acryated urethanes, they may be different enough in composition that they require two competey different sovents to remove them. In some cases, a combination of two sovents used in succession may be required. With some conforma coatings, such as Loctite's Shadowcure 361, no sovent was found to be suitabe. Tabe 2 provides a guide for proper sovent seection for remova of UV cured conforma coatings. Generay, the remova process is the same as that for other coating types: the PCB shoud be immersed in the appropriate sovent; when coating remova is compete, the board shoud be thoroughy washed in acoho, rinsed in DI water, and dried. Page 15 of 21

16 Remova times can vary anywhere from 15 minutes to 24 hours, depending upon the coating, coating thickness, and the sovent used. Agitation or the use of utrasonics wi speed up the procedure. Spot remova may be done by appication of the sovent with a brush, cotton pad, or cotton tipped swab. Some of the sovents may be avaiabe in a ge form for spot remova appications. Tabe 2 Sovent Seection Guide for Remova of UV Cured Conforma Coatings Conforma Coating Type Thickness Sovent Approx. Time for Remova Urethane acryates Dow Corning X Methano Base/ Acid 4 Hours Dymax Muti Cure Dimethyformamide Base 15 Minutes.006 Methyene Choride Base/Acid 15 Minutes.006 Methano Base/ Acid 1 Hour Dymax Muti Cure 984F.006 Dimethyformamide Base 15 Minutes.006 Methyene Choride Base/Acid 15 Minutes.006 Methano Base/ Acid 1 Hour Dymax Muti Cure 984RF.006 Dimethyformamide Base 15 Minutes.006 Methyene Choride Base/Acid 15 Minutes.006 Methano Base/ Acid 1 Hour Loctite Shadowcure 361 N/A No Sovent was Found Suitabe for N/A Remova W/R Grace Amicon UV N/A Methyene Choride Base/Acid 2.5 Hours 920 W/R Grace Amicon UV N/A Ethyene Gyco Ether Base/Akaine 24 Hours 920 Acryated Epoxy Urethane DuPont Quickcure B Dimethyformamide Base 15 Minutes.003 N Methypyrroidone Base 1.5 Hours.003 Methyene Choride Base/Acid 15 Minutes.003 Butyroactone Base 45 Minutes DuPont Quickcure B Dimethyformamide Base 15 Minutes.003 N Methypyrroidone Base 1.5 Hours.003 Methyene Choride Base/Acid 15 Minutes.003 Butyroactone Base 45 Minutes Siicone Page 16 of 21

17 Dow Corning X Methyene Choride Base/Acid 15 Minutes.011 Butyroactone Base 45 Minutes.011 Methano Base/ Acid 15 Minutes.011 Ethyene Gyco Ether Base/Akaine 45 Minutes Dow Corning X Methyene Choride Base/Acid 30 Minutes.004 Ethyene Gyco Ether Base/Akaine 1.25 Hours.004 Hydrocarbon Base/Acid 1 Hour Abrasive (Workstations) Because most UV coatings act ike a cross between acryic and poyurethane, this technique of remova works extremey we. Remova Time Technique Spot Remova Whoe Board Good. Don t even try. Mechanica Good but care must be taken. Don t even try. Chemica Care must be used. Masking may be See above tabe. Caution must be used. required. Wi sti take between 15 minutes and 24 hours. Abrasive Fast. Labour intensive, depending on thickness of coating. Cean up Mechanica Chemica Abrasive Litte if any. Litte if any. Messy, foow EPA reguations.. Depends on media type used. If pastic, no cean up, others wi require further ceaning. Page 17 of 21

18 Page 18 of 21 Bibiography 1. Conforma Coating Remova, Jay W. Parton, Eectronic Servicing & Technoogy, Juy New Method of Stripping Conforma Coating, Vaughn Martin, Eectronic Repair Basics, March Reprinted from Fundamenta Requirements For Static Protective Containers by J.R. Huntsman, D.M. Yenni, Jr., and G.E. Mueer, Static Contro Systems / 3M, St. Pau, Minnesota.

19 Summary by Technique Remova Time Coating Spot Remova Whoe Board Poyurethane Again, don t use this technique, it s deady N/A Siicone Watch the fumes Don t even try Acryic Quick and efficient, how safe it is depends on the Don t even try operator Epoxy Unknown, depends on thickness of coating Don t even try Paryene Very good, but be carefu Don t even try UV Cured Materias Good Don t even try Remova Time Mechanica Coating Spot Remova Whoe Board Poyurethane Depends on the thickness and ski of the operator Don t even try Siicone Depends on the thickness and ski of the operator Don t even try Acryic Quick and efficient. Care must be taken not to damage Don t even try the board Epoxy Depends on the thickness and ski of the operator Don t even try Paryene Very good but care must be taken Don t even try UV Cured Materias Good but care must be taken Don t even try Page 19 of 21

20 Remova Time Chemica Coating Spot Remova Whoe Board Poyurethane Care must be used. Masking may be required. Wi sti take about an hour The best if removing coating from the entire board Siicone Care must be used. Masking may be required. Most feedback is negative Soak time must be watched or damage wi occur. 15 minutes to overnight soak is required Acryic Care must be used. Masking may be required. Wi sti take at east one hour. Most feedback is negative Soak time must be watched or damage wi occur Epoxy Don t even try Don t even try Paryene Don t even try Don t even try UV Cured Materias Care must be used. Masking may be required Between 15 minutes and 24 hours Remova Time Abrasive Coating Spot Remova Whoe Board Poyurethane Fastest and easiest Depends on the thickness of the coating. Siicone Fastest and easiest in most cases, Depends on the thickness of the coating especiay with newer siicones. Acryic Fastest and easiest Very fast Epoxy Fastest and easiest Labor intensive Paryene Fastest and easiest Fastest and easiest UV Cured Materias Fast Labor intensive, depending on thickness of coating. Cean up Coating Poyurethane Siicone Acryic Epoxy Paryene UV Cured Materias Cean Up N/A Don t use this technique for poyurethane s. Messy Litte if any Litte if any Litte if any Litte if any Page 20 of 21

21 Cean up -Mechanica Coating Poyurethane Siicone Acryic Epoxy Paryene UV Cured Materias Cean Up If attempted, itte cean up is required uness board is damaged. Litte if any Litte if any Litte if any Litte if any Litte if any Cean up - Chemica Coating Poyurethane Siicone Acryic Epoxy Paryene UV Cured Materias Cean Up Messy, foow EPA reguations. Messy, foow EPA reguations. Messy, foow EPA reguations. N/A Don t use chemicas with epoxy coatings Don t use chemicas Messy, foow EPA reguations. Cean up - Abrasive Coating Poyurethane Siicone Acryic Epoxy Paryene UV Cured Materias Cean Up Depends on media type used. If pastic, no cean up, others wi require further ceaning. Depends on media type used. If pastic, no cean up, others wi require further ceaning. Depends on media type used. If pastic, no cean up, others wi require further ceaning. Depends on media type used. If pastic, no cean up, others wi require further ceaning. Depends on media type used. If pastic, no cean up, others wi require further ceaning. Depends on media type used. If pastic, no cean up, others wi require further ceaning. Page 21 of 21