16th November 2013

This is a follow up of the previous post for home made pcbs. Most of you who are

shopping for the first time for raw materials for making pcb must be in a

confusion as where to go....so i decided to compile some useful information for

them..

CHEMICALS : Galaxy Scientific, opposite CMC Hospital, (near the bus stand),

Vellore

CHEMICALS :

1. Laboratory supplies (Behind Pothees super market) Old Sreekandeswaram

Road ( cheap and reliable)

2. A shop in SS Kovil road (near the SBI bank)

3. A shop near martyr's column, palayam along the shops near the mosque

(haven't gone there)

Posted 16th November 2013 by Aby Raj

Labels: chemicals, pcb, shop

Shopping guide for chemicals

Careful.....The following info is for electronics

hobbyists in Vellore and Trivandrum city only

VELLORE

BLANK PCB :Ganesh Radio House, Sarathy Mansion, New bus stand, Vellore

TRIVANDRUM

BLANK PCB :

1. AB Electronics, Thakaraparambu street, East Fort

2. Power electronics, Thakaraparambu street, East Fort

3. Telematics, Thakaraparambu street, East Fort

4. Vrindha electronics, Thakaraparambu street, East Fort

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16th November 2013

Home made PCB tutorial

Aby Raj P.M. Advanced Embedded Systems,

Keltron IT Education Center

I hate storytelling and lengthy explanations but people have been

asking me for a write up on making PCBs using toner transfer

process.So I decided to make this tutorial. Here, I describe my

method of making prototype PCBs using ferric chloride. I made my

first custom PCB around 2007or 2008 and since then I have learnt a

lot regarding the various advantages and disadvantages of this

process. Way back then, I was able make only thick tracked PCBs

with few crowding of lines and took a time of 30-45 minutes. Now I

am able to make SMD PCBs and PCBs with fine traces within a

time of 5-15 min. What I mean is that making mistakes is not a

problem if you never give up. They make you learn all the important

process variables in the process.

Other processes are also there with diff chemicals but I’ll stick to

Ferric chloride based process for this tutorial since it is affordable

and safe enough. There are a lot of tutorials on the web and

relatively this tutorial is a big one but I want the reader to be fully

aware of the process and the process variables to achieve 100 %

success.

One word of caution: The following activity involves exposure to

organic/ inorganic chemical fumes, heat and PCB dust. Use

appropriate safety precautions like gloves / face mask / chemical

resistant apron during working. Although the chemicals used are not

dangerous, still it’s advisable to follow the safety guidelines properly

during working, handling and disposal.

Raw materials required

Homemade PCBs

[http://3.bp.blogspot.com/-2GPw_jklUNo/Uoc2-

j9XCaI/AAAAAAAAAFc/0CJ8OS7FVnY/s1600/raw+materials.jpg]

Single side-copper clad PCB blankUse good quality PCB blank board for your work. Good quality

boards have a nice bending strength whereas poor quality boards

bends very easily.

Glossy paper or special toner transfer paperRefer the printer manual for the correct gsm for your printer. I use

120-130 gsm paper. Improper paper usage can harm the printer or

its fuser. Please take care in this regard.

Ferric chloride (FeCl3) etchant powder

I use a low cost FeCl3 from nice chemicals. It costs around 200 Rs

max. The plastic jar shouldn’t be kept open unnecessarily since the

chemical is hygroscopic and tends to form lumps in presence of

excess moisture.

Paint thinnerCommon paint thinner can be used. Costs around 71 Rs/500 mL

Water for cleaningWater is very important because if you clean the utensils

immediately after the process, the ferric chloride stains can be

removed easily.

Equipments required

http://3.bp.blogspot.com/-mqgTPhCKYmU/Uoc-sD9MSLI/AAAAAAAAAH8/p6cZySHOwzs/s1600/Equipments+required.jpg

[http://3.bp.blogspot.com/-mqgTPhCKYmU/Uoc-

sD9MSLI/AAAAAAAAAH8/p6cZySHOwzs/s1600/Equipments+required.jpg]

Laser printerNormal B/W laser printer

Electric iron (1000 W works best)I use a Philips 1200 W iron for this purpose. When I used a low

wattage iron, I got varying performance. That’s why I suggest a min

of 1000 watts. The toner transfer phase needs a decent amount of

heat.

Paper cutterFor cutting the glossy paper.

A metallic utensil for heating chemicalUsually people don’t use this but I suggest a metal vessel for heating

chemical and water mixture since heat can accelerate the reaction.

It’s very useful in case the reaction slows down during the reaction

phase.

Heat resistant plastic container for etchingIts advantage is three fold. We may need to handle the container

during etching. So it’s better to use a plastic container for this

purpose. Also plastic won’t react with the chemicals or transfer

away the useful heat needed for the reaction.

Medium grade Tooth brush for cleaning

Required for PCB cleaning. Medium grade works best

Pcb drill-electric/handheldThere are situations when you have everything else except the drill

for making holes. Use a manual spring-action drill or an electric drill.

Electric bench drills are expensive enough for a student but you may

find one in your college PCB lab. Portable hand drill for PCB are

very rare and usually people like me tinker with small hand drills for

working with PCBs.

Another word of caution: When you make PCB designs in cad

software, make sure that drill holes are not under-dimensioned.

Sometimes people unknowingly make designs for .4 mm drill holes

while they have only .8 mm drill bits. This can be a head ache if one

fail to notice this prematurely during the design phase. When you

have limited equipment you need to make some adjustments !!

Scotch BriteBelieve me….this humble piece of equipment actually plays a very

important role.

Cleaning clothI strongly suggest to keep a waste cloth/ rag nearby to clean away

accident spillovers and also for handling uses.

A BRIEF OVERVIEW OF THE PROCESS

[http://2.bp.blogspot.com/-

q3lmsqk1Zow/Uoc3CTrSjOI/AAAAAAAAAFk/iYTjyAt1DIY/s1600/PROCESS.jpg]

PREPARE THE ARTWORK

The artwork can be made using cad softwares like Express PCB,

Cadsoft Eagle, Orcad, Altium etc… I won’t be teaching you about

making the cad layout now. Lets just assume that you have made the

layout. Evenmore, the layout can be taken from a magazine also as

popular magazines like EFY, EPE, publish PCB layouts along with

the articles.

After you prepare the artwork, print it on a glossy paper with a

good amount of resolution. I use 600 dpi but if the artwork is not

good enough then you can use a higher resolution.

PREPARE THE BOARD

For boards with lot of imperfections, use the a file, square and hacksaw to

prepare the board. If you don't have much equipment with you, use a sand paper

or scratch the edges on a rough surface to polish the board in a much

inexpensive way. Newly purchased boards are often perfect to be toner

transferred without polishing or preparation

[http://1.bp.blogspot.com/-

uD34uDTv418/Uoc_t_KpMUI/AAAAAAAAAIE/_rPDpz0BD_g/s1600/board+prepare.jpg]

Make the artwork ready for printing alongwith the glossy paper

for printing it. Use max dpi like 1200 if you are doing for the first

time. I normally settle down for 600 dpi but if you are doing this

for the first time, I recommend 1200 dpi or highest

available. Some printers have options for printing settings like

heavy paper. Use according to the manual given.

It’s always better to take a min of two copies for a given artwork

since you can always use the second one if the first one goes

wrong. Take one cut portion, place the artwork portion on shiny

copper side and fold the remaining paper as shown in the

pictures below.

TONER TRANSFER, CLEANING AND

TOUCH UP

THIS IS A SERIES OF CRITICAL STEPS THAT

DETERMINES THE INTEGRITY OF THE

RESULTING PCB

Printing and Preparation

[http://4.bp.blogspot.com/-

auknMa_2MXI/UodE45PSCxI/AAAAAAAAAIc/NxlmMazx4Nk/s1600/print.jpg]

TONER TRANSFER

[http://1.bp.blogspot.com/-FKUFbUnU8AQ/UodHF-

AN6XI/AAAAAAAAAIo/5fMCFhtgADY/s1600/print_1.jpg]

Now, heat the copper side with the artwork placed on it as shown

before. The heat of iron will melt the toner and it will stick to the

copper side facing it. Notice that the while ironing the un-laminated

side is placed down and the iron touches the copper side covered

with paper. I obtained the best results by using irons of around one

kilowatts or higher. Set the iron’s thermostat on the cotton/wool

mark. When I was a novice, after reading several web pages, I used

the highest setting. Although it turns out to be good for PCB tracks

with large inter-track spacing, it doesn’t work for small spacings. A

medium setting of wool is good for most applications. Time is also

a critical factor. Too much time like 1 min will result in separation of

copper laminate from PCB causing blisters on the laminate making it

unusable. An average time is somewhere between 5-11 seconds.

Place the iron uniformly over the copper side rather than constantly

over one area. Also try to heat all tracks by moving the uniformly or

some tracks may not get properly heated up. Tracks along

boundaries should be taken care of in this way , if they are

present…

[http://1.bp.blogspot.com/-yVWnL9PeQDc/UodI_UV59-

I/AAAAAAAAAJM/OGmrZ6vngyw/s1600/print_2.jpg]

Put the PCB immediately in water and let it soak for some 30

seconds. After that start peeling off the paper from the PCB

carefully along the tracks.

[http://3.bp.blogspot.com/-

RVWcMBy8Swc/UodIdWKJWQI/AAAAAAAAAJI/lKvCTeflRYY/s1600/print_3.jpg]

If the paper remaining seems stubborn first try to put it in running

water and simultaneously remove by gently rubbing the paper. Dry

removal will cause broken tracks.

[http://1.bp.blogspot.com/-3_WRedMpJm4/UodIdmvyyYI/AAAAAAAAAJE/86x7BJhP394

/s1600/print_4.jpg]

Still paper needs to be removed from forming interconnections and

bridges or they may cause shorts after etching. Use a tooth brush to

remove the removing traces of paper.

TOUCH UPIf some tracks are broken or a minor problem comes, do

touchup operation by using a permanent marker ink which is

good enough. Some inks will not withstand the etching

process so select a good pen or do multiple touches on the

same area.

WHAT IF THE TRACKS ARE TOO BAD….

If you get into a major problem like only 50% tracks getting

transferred, you need to start over again by removing the

toner using scrotchbrite or thinner. You can use the same

board but clean it well. This is why I recommend using

multiple copies of artwork output.

STEP 4: ETCHING, DRILLING, AND

SOLDERING THE PCB

Preparation of the chemical solution

[http://4.bp.blogspot.com/-

AU1eVuDnPv8/UodKNDR_47I/AAAAAAAAAJs/Ip4v9klZ9m8/s1600/solution.jpg]

Etching, stripping toner, drilling and

soldering

[http://2.bp.blogspot.com/-0nMz--

h_tGw/UodKNOEhQyI/AAAAAAAAAJo/0fziuhd1doY/s1600/etching.jpg]

After cleaning the etched PCB, rub vigorously with thinner soaked

cotton or cloth to strip the toner from the PCB. Drilling will finish

the whole process.

I’ve detailed the whole steps for you in a lengthy story

kind of way but once you master it, the whole thing can

be done in 5-15 minutes.

[http://4.bp.blogspot.com/-T4_ic0g3dYE/UodKMTpAR-

I/AAAAAAAAAJc/6ZRuJrdKv8w/s1600/finished.jpg]

Posted 16th November 2013 by Aby Raj

Location: Thiruvananthapuram, Kerala, India

Labels: etching, ferric chloride, pcb

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