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I found a paper about making a copper plating solution and thought I'd give it a shot. Please keep in mind I have no formal education in chemistry. I have a few questions about the preparation of the solution.

Information:

The paper lists the following ingredients:

Ingredients

In the conclusion, the authors recommend the following additives:

  • 500 ppm PEG
  • 5 ppm SPS
  • 30 ppm JGB

PEG:

The PEG I have is labeled as PEG 400. The paper doesn't say anything about this. I assume the paper calculates as if it was pure PEG, where mine is 400 g / mol? Could someone guide me on how to calculate the quantity needed to achieve 500 ppm?

Cl-:

For chlorine, I am considering hydrochloric acid. The concentration of the acid I have is 30%, and I would need 1.4 mM of chlorine. Since I need only a very small amount, It might be best to dilute the concentrated acid. I do have a very precise scale, but weighing out 0.05 gram seems a bit ridiculous.

Results:

Here is what I've calculated so far:

Chemical Molar mass Required Result
CuSO4 5H2O 159.609 g/mol 0.79 M 126 grams
H2SO4 98.079 g/mol 1.02 M 100 grams
HCl 36.46 g/mol 1.40 mM 0.05 grams
SPS - 5 ppm 5 milligrams
JGB - 30 ppm 30 milligrams
PEG400 - 500 ppm (Not sure)

This is for a 1-liter solution, with the remainder being deionized water. I'm aware of the acid-to-water addition protocol.

Prepare scaled down solutions:

Make 1% SPS solution: 1000 mg SPS + 9000 mg water = 10000mg of 1% solution.

Make 1% JGB solution: 1000 mg JGB + 9000 mg water = 10000mg of 1% solution.

Make 1% PEG solution: 1000 mg PEG + 9000 mg water = 10000mg of 1% solution.

Make 1% HCl solution: 100 mg HCl @ 36% + 3500 mg water = 3600 mg of 1% solution. 1% HCl => 36.46 / 0.01 = 3646 g/mol

Prepare electrolyte 1 kilo (more or less 1 liter)

Add CuSO4 5H2O: CuSO4 5H2O = 159.609 g/mol 0.79M * 159.609 g/mol = 126 gram

Add H2SO4: H2SO4 = 98.079 g/mol (Mine is 98%) 1.02M * 98.079 g/mol = 100 gram

Add HCl: HCl @ 1% = 3646 g/mol 0.0014M * 3646 g/mol = 5.1044 gram

Add PEG: 500ppm of PEG = 500 mg total 500mg @ 1% = 50 gram

Add SPS: 5ppm of SPS = 5 mg total 5mg @ 1% = 0.5 gram

Add JGB: 30ppm of JGB = 30 mg total 30mg @ 1% = 3 gram

Power supply:

The paper specifies a particular waveform. For now I would like to ignore this and just use a current limited DC power supply.

References:

Shin S-H, Kim T-Y, Park J-H, Suh S-J. Optimization of Additive and Current Conditions for Void-Free Filled Through-Silicon Via. Applied Sciences. 2018; 8(11):2135. https://doi.org/10.3390/app8112135

Bas Visscher
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  • Not sure about the significance of the choice of PEG MW, but for calculating ppm that would be irrelevant. Also, you have a lot of latitude in the choice of amount of PEG to add: $$\pu{100-500 ppm }= \pu{100-500 x 10^-6 g~PEG/g} ~\textrm{solution} \ \approx \pu{100-500 x 10^-3 g~ PEG/kg~\textrm{solution}}$$ If you choose to make 1 kg (approx 1 L) of solution at a concentration of 500 ppm PEG that means adding 500 mg of PEG. Given the wide suggested range you probably don't need to be particularly accurate. – Buck Thorn Oct 25 '23 at 07:32
  • The choice of waveform is probably important, but this is not my specialty. – Buck Thorn Oct 25 '23 at 07:33
  • @BuckThorn, So then, what's the difference between PEG and PEG400? I know you also have PEG 3000 for example. From what I've read, it's the molar mass of the peg. But I doubt my bottle contains pure PEG, since it's a liquid. – Bas Visscher Oct 25 '23 at 09:56
  • You can read more about PEG on the Wikipedia: https://en.wikipedia.org/wiki/Polyethylene_glycol It's a polymer, and the number of monomers in a chain determines whether its a solid or liquid at room temperature. The low MW stuff is liquid – Buck Thorn Oct 25 '23 at 15:04
  • I have found some, not so reliable, claims on the internet that the PEG should be between 1500 and 3500. Since it's not too expensive, I ordered some PEG 1500. – Bas Visscher Oct 27 '23 at 14:42
  • In the description of the polymer, 400 is the probable molecular mass of the polymer PEG. As the monomer has a molecular mass equal to $62$, it means that the polymer is a mixture of hexamers and heptameters, which may be liquid. – Maurice Oct 27 '23 at 14:44
  • Some practical remarks. 1) $\ce{HCl 1}$% does not have a molecular weight $3646$ as given in the text. Solutions like $\ce{HCl}$ $1$% do not have a molecular weight. Only pure substance have a molecular weight. $\ce{HCl}$ has a molecular weight of 36.46 g/mol. – Maurice Oct 27 '23 at 15:05
  • Some practical remarks. 1) $\ce{HCl 1}$% does not have a molecular weight $3646$ as given in the text. Solutions like $\ce{HCl}$ $1$% do not have a molecular weight. Only pure substance have a molecular weight. Pure $\ce{HCl}$ has a molecular weight of 36.46 g/mol. 2) See under ... – Maurice Oct 27 '23 at 15:15
  • In the text, the $\ce{Cl-}$ concentration is obtained by adding $\ce{HCl}$. This is not a good idea, as first $\ce{HCl}$ is a gas. Gases are difficult to weigh, and to dissolve. And if you use commercial $\ce{HCl}$ solutions instead of the gas, it is not easy to weigh with precision small amounts of liquids, like less than one gram. You should rather replace $\ce{HCl}$ by $\ce{NaCl}$ which is easy to weigh with precision, whatever the quantity chosen.
    • – Maurice Oct 27 '23 at 15:22
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    If you want to make a solution of PEG $200$ ppm, it is not important to know which sort of PEG you use. $1$ liter PEG $200$ ppm, means $200$ mg or $0.2$ g PEG, whatever the choice of PEG. You may choose PEG $300$, or PEG $1500$, or any other sort off PEG. The only important thing is the necessity of adding $0.2$ g of this PEG in one liter water. – Maurice Oct 27 '23 at 15:28
  • The same problem happens for $\ce{HCl}$ and $\ce{H2SO4}$. You may be sure of weighing $100$ g $\ce{H2SO4}$. But how will you be sure that this viscous liquid sample will be correctly transferred into water solution ? It is possible, but not easy. Think in advance about how to handle this corrosive liquid ! – Maurice Oct 27 '23 at 15:33