Analysis and experimental study of the hottest PCB

2022-09-21
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Analysis and experimental study of PCB plating solution (9)

M. analysis of electroless nickel plating solution

■ 1. determination of nickel

1) analysis steps

pipette 5 ml of solution into a 300 ml conical flask, add 2 ml of hydrochloric acid and 2 ml of 30% hydrogen peroxide, boil and evaporate to nearly dry, and add 100 ml of water. If salt precipitates during evaporation, shake to dissolve it. Add 2 ml of triethanolamine, 12 ml of ammonia, and a little ammonium puranate. Titrate with 0.05medta solution until it turns from brown yellow to purple as the end point. The titration speed should slow down when it is close to the end point

2) calculation

nickel sulfate containing niso4.7h2o= M × V × zero point two eight zero eight × 1000/5 (g/l)

where:

m-- molar concentration of standard EDTA solution

v-- ml of standard EDTA solution consumed

■ 2. Determination of sodium hypophosphite and sodium phosphite

method 1: cerium nitrate titration

2.1 determination of sodium hypophosphite:

1) analysis steps

use a pipette to suck 5 ml of the solution into a 250 ml conical flask, add 15 ml of 1:5 sulfuric acid and 1 drop of Triadimefon. If the solution is red, it indicates the presence of ferrous iron. Add 0.1N cerium ammonium nitrate drop by drop until the red disappears (regardless of dosage). Then add 25 ~ 30 ml of 0.1N ceric ammonium nitrate from the burette (1 ml for each containing 1 g/L of nahpo2.h2o2, and an excess of 15 ml), place it in a 60 ℃ water bath for 30 minutes, cool it, add 1 drop of Triadimefon, and titrate with 0.1N ammonium ferrous sulfate solution until it suddenly turns red as the end point

2) calculate

NaH2PO2 containing sodium hypophosphite H2O =(N1V1-N2V2) × zero point zero five three × 1000/5 (g/L)

, where:

N1 -- equivalent concentration of standard ceric ammonium nitrate solution

n1-- ml of standard ceric ammonium nitrate solution consumed

n2 -- equivalent concentration of standard ferrous ammonium sulfate solution

n2-- ml of standard ammonium ferrous sulfate solution consumed

0.053--NaH2PO2 . H2O/2000

2.2 determination of sodium phosphite

1) analysis steps

use a pipette to suck 2.5 ml of the solution into a conical flask, add 8 ml, 15 ml of 1:5 sulfuric acid, and a drop of Triadimefon. If the solution is red, drop 0.1N ceric ammonium nitrate until the red just disappears (regardless of the dosage). Then add 40 ~ 50 ml of 0.1N ceric ammonium nitrate solution from the burette (1 ml qb/t 3897 ⑴ 999 galvanized welded mesh (5). 5 solder joint tensile resistance; 0.5 ml na2hpo31 g/L, and 15 ml excess), cover the conical bottle, heat it to boil, and keep it boiling with a low fire for 30 minutes. Be careful not to evaporate too much water, cool, and add 1 drop of Ferrone, Titrate with 0.1N ammonium ferrous sulfate solution until it turns red suddenly

2) calculation

na2hpo3 containing sodium phosphite = (n1v1 - n2v2) × zero point zero six three × 1000/2.5 - 2.38a (g/L)

where:

N1 -- equivalent concentration of standard ceric ammonium nitrate solution

n1-- ml of standard ceric ammonium nitrate solution consumed

n2 -- equivalent concentration of standard ammonium ferrous sulfate solution

n2-- ml of standard ammonium ferrous sulfate solution consumed

a-- NaH2PO2 in solution H2O content (g/l)

2.38--2 × Na2HPO3/NaH2PO2. H2O;

0.063--Na2HPO3/2000。

note: (1) the above two methods are not applicable to solutions containing organic salts such as citrate, and the results are much higher

(2) when determining hypophosphite, the water bath temperature should not exceed 60 ℃, otherwise phosphite may be oxidized, making the result higher

(3) this method can directly determine hypophosphite in the presence of phosphite, with fast speed and correct results

at this time, the control of the hot melt viscosity of rubber and plastic materials is extremely important (4) the preparation and calibration of indicators and standard solutions

① dissolve 1.485 g of o-phenanthroline in 100 ml of 0.25m ferric sulfate (containing 0.769 g of FeSO4 · 7H2O) with ferrolin indicator

② standard 0.1 N ceric ammonium nitrate solution, weigh 56 g of [ce (NO3) 4 · 2nh4no3] ceric ammonium nitrate and 56 ml of concentrated sulfuric acid (specific gravity 1.84), carefully add 100 ml each time, fully stir until it is completely dissolved, and then weigh and release to 1 liter. If there is muddy sediment, filter it

for calibration, pipette 25 ml of ceric ammonium nitrate standard solution into a 250 ml conical flask, add 25 ml of water, 15 ml of 1:5 sulfuric acid and 1 drop of Triadimefon, titrate with the new standard 0.1N ammonium ferrous sulfate solution until it suddenly turns red as the end point

n=n1*v1/25

where: n-equivalent concentration of standard ceric ammonium sulfate solution

n1- equivalent concentration of standard ammonium ferrous sulfate solution

n1- ml of standard ammonium ferrous sulfate solution consumed

method 2: iodometry

(I) determination of sodium phosphite

1. Analysis steps:

pipette 5 ml of the solution into 50 ml iodine bottle, add water to weigh and release to 50 ml, add 20 ml of 5% sodium bicarbonate and 0.1N ml of iodine solution (each containing 21g/L nahpo, add 1 ml, and then excess 15 ml), cover the bottle stopper, place it for one hour, open the bottle stopper, and acidify the solution with acetic acid, Titrate with 0.1N sodium thioate solution to light yellow, add 3 ml of starch, and continue titrating until the blue disappears for 1 minute

2. Calculate

na2hpo3 containing sodium phosphite= (n1v1-n2v2) *0.063*1000/5 (g/L)

where N1 is the equivalent concentration of standard iodine solution

v1-- ml of standard iodine solution consumed

n2 -- equivalent concentration of standard sodium thiosulfate

v2 -- ml of standard sodium thiosulfate consumed

0.063- Na2HPO3/2000。

(II) determination of sodium hypophosphite

1. analysis steps

suck the solution 2.51 with a pipette, cut successively along the width direction of the strip, the thickness is the thickness of the strip, the height is 100mm ml, and put it into a 50ml iodine bottle, add 15ml of 1:5 sulfuric acid and about 40ml of 0.1N iodine solution (each containing NaH2PO2 · h2o1 g/L), and add ml; Na2 next, let's introduce the composition of the fatigue testing machine and the basic management in normal use. HPO3 1 g/L, add 0.5 ml, and then excess 15 ml,) cover the bottle stopper, place it for 10 hours or overnight, cool the solution with ice water (to prevent iodine from volatilizing during neutralization) for neutralization of sodium bicarbonate mixed into paste with water, add 5% sodium bicarbonate 20 ml, cover the bottle stopper, place it for 1 hour, and acidify the solution with acetic acid, Titrate with 0.1N sodium sulfate solution to the end point according to the previous method

2. Calculate

NaH2PO2 · H2O containing sodium sulfite = [(n1v1-n2v2) *0.0265*1000/2.5]- 0.421a (g/l):

where N1 - equivalent concentration of standard iodine solution

v1-- ml of standard iodine solution consumed

n2 -- equivalent concentration of standard sodium thiosulfate

v2 -- ml of standard sodium thiosulfate consumed

a-- na2hpo3 content in solution (g/L)

0.421--nah2po2 · h2o/2na2hpo3

0.0256--nah2po2 · h2o/4000

source: PCB information

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