hmm two questions arised now:
first i have to inform myself about stabilizers and how long they may be useful to conserve the H2O2. i
don't assume they would help if there is one week between the prototypes.
the second issue is regenerating the fluid with air oxygen, i'm really wondering if this would also work
with this etchant.
when using hydrocloric it converts Cu2Cl2 to CuCl2 and the CuCl2 does thake the copper off the pcb and
gets Cu2Cl2 (as i have understand it). but in your bath CuSo4 builds.. have no idea how this all works
together and if your solution may be regenerated with air oxygen.. my chemistry knoweledge is bad..
i also wonder if the "battery liquid" sold at car shops is clean sulphuric acid and can be used or not.
regards
stefan
18.04.2003 16:41:15, "twb8899" <
twb8899@...> wrote:
>Stefan,
>
>We never tried using hydrochloric acid in our shop so I don't have
>any ideas on that process. Most PWB shops electroplate a metallic
>resist such as tin or solder and the etchant must be compatable with
>this resist. The copper background is etched but the tin or solder
>plated areas remain after etching.
>
>Sulfuric/peroxide etchants will darken the solder plating but won't
>etch through thus leaving the circuitry well defined and ready for
>solder reflow.
>
>I'm not certain if the hydrochloric acid based etchants will
>precipitate copper as a crystal but I assure that the sulfuric types
>will. They are also very easy to operate. I don't remember the
>peroxide consumption but it wasn't too bad since we also added a few
>ounces per day of stabilizers.
>
>For hobby and small volume use just make up the initial batch, heat
>it up, add a few ounces of peroxide whenever you want to etch and
>you're ready to go. When the copper content grows to around 8-10
>ounces per gallon it will start to form crystals at room temperature.
>
>Scrape these crystals out of the tank, add a few ounces of sulfuric
>acid and peroxide and start etching. Sulfuric acid will only be
>consumed when the crystals are formed. The main consumable will be
>hydrogen peroxide.
>
>If stabilizers are used the peroxide consumption is not bad at all.
>Technical grade peroxides already have some stabilizers and are a
>light yellow color. Food grade peroxides are clear and will be
>consumed faster as they have no stabilizer.
>
>If the etching bath is run at lower temperatures the peroxide will
>last much longer but the etch rate will slow down. This is no big
>deal for the occasional prototype. We ran our etch tank at 115
>degrees F with an etch rate of about 3 to 5 minutes for half ounce
>copper laminate. When the rate slowed down the operator just added a
>little peroxide to increase the rate. It usually took about a half
>gallon addition to speed up a fifty gallon etch tank. I'll try to
>find my notes on acid and peroxide consumption per square foot of
>etched copper and post that information later.
>
>I made our stainless etching racks from 316 stainless steel and they
>lasted over twenty years. Some of the welds on the rack handles
>showed some surface corrosion but only because I goofed and welded
>them using 304 rods. I used a plasma cutter and tig torch to make the
>racks. The PVC tank took quite a beating and finally started cracking
>after twenty or so years but the plastic was not damaged by the
>etchant.
>
>The electrowinning cell used lead anodes because they were inert in a
>sulfuric acid bath. That's why lead anodes are used in many sulfuric
>anodizing tanks. I'm sure they give out over time but they do have a
>very long service life.
>
>I now only make boards for my own products and other very small
>production runs. The etchant is ferric chloride in a small spray
>etcher. I use dry film resist or electroplated gold as an etch
>resist. If we started up large production again I would go back to
>using the sulfuric peroxide because it's so easy to use.
>
>Tom
>
>--- In Homebrew_PCBs@yahoogroups.com, Stefan Trethan
><stefan_trethan@g...> wrote:
>> hi tom!
>>
>> really great method!
>>
>> i wanted to ask if you may figure out the amount of hydrogen
>peroxyde consumed (and also if the etchant
>> was used very often which i assume or seldom. if one uses a
>soultion with H2O2 seldom (once a week or
>> so) i believe all of the H2O2 has vanished in between and needs
>replacement. the 10% you state for
>> initial use seems quite similar to the amount needed by my hcl h2o2
>method. but interesting would be if
>> it is used up very quick, then it would become more expensive with
>less using rate.
>> i know you only adjusted it via etching rate but if you may
>remember at least one time, like after some
>> holydays or so, when you haven't used the bath some days if it
>needed the full 10%?
>>
>> i'm also wondering if the copper also falls out when using
>hydrocloric acid and hydrogen peroxyde. it
>> never fell out in my etchant but maybe the concentration is yet too
>low (concerning only 35micrometer
>> copper thickness)...
>>
>> also your description of electrowinning is very nice. that is
>exactly what i hoped for.
>> i'm wondering which reason there is for the lead plates?
>> why lead?
>>
>>
>>
>> another question: you have obviously used stainless steel in your
>etchant, how did it resist?
>> perfect or was there some agression?
>>
>>
>> i see only one disadvantage of your method compared to the
>hydrocloric acid and this is availability of
>> sulphuric acid. it is much, much easier to get the hydrocloric acid
>here. it is sold in many stores, for
>> household use. sulphuric acid is only available in special stores.
>but if one needs hydrogen peroxyde he
>> has to go there anyways (if not getting it from hairdressing
>supply)..
>>
>>
>> i find your method very interesting but it would be more
>comfortable to stay with a hydrocloric
>> process... i will try if there also falls out the copper if i let
>it cool down.. (i always put the
>> etchant back into its bottle after useage, so it the copper
>concentration was diluted immediately).
>>
>> many thanks, was a great help to mee.. also some satisfaction that
>somebody else thought of electrolysis
>> and did try it (even if it showed to be not comfortable).
>>
>>
>> regards
>> stefan
>
>
>
>
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