Background technology
Tin is very good metal of a kind of weldability, and anti-corrosion capability is preferably arranged, and therefore is widely used in electronic industry.Such as in the production technique of the printed circuit board (PCB) of use for electronic products, a kind of mode be adopt hot air leveling technology (the slicker solder coating of tradition " spray tin " process using because lead and compound thereof be the hazardous and noxious substances of harm humans health and contaminate environment and day by day eliminated by industry), at the PCB surface made spraying one deck tin layer as scolder, to guarantee that PCB is in follow-up SMT(assembling) electronic devices and components have good characteristics such as weldability in the process; Another mode commonly used is the Technology of the heavy tin of chemistry that gets up of development in recent years, by chemical replacement reaction produce a layer thickness evenly, the pure tin coating of surfacing, convenient follow-up electronical elements surface attachment process, because this technology is good than the thickness evenness of hot air leveling coating, and there are not bad problems such as scolder bridging, plug-hole, be particularly suitable for the surface treatment that industry technology develops to high-density, high precision, fine rule road, closely spaced printed circuit board direction, the heavy tin of chemistry has very large development potentiality.
But the heavy tin of chemistry also faces various technical problems as process of surface treatment.Such as, the chemical tin coating forms the whisker crystal of " whisker " easily, and these whiskers can cause the problem of " micro-short circuit "; Some patents propose solution at this problem both at home and abroad, for example among the Chinese patent CN1387465 " method of copper or copper alloy electroless plating tin ", adopt methylsulfonic acid and pink salt, complexing agent and be no less than a kind of added metal constitutional chemistry tin plating electrolyte, overcome zinc-plated coating and produce " whisker " problem.
In addition, the chemical tin coating before element assembling, also occur easily the jaundice of tin face and and then the problem that welding property reduces appears, particularly be accomplished to time of electronic devices and components assembling long time the, even more serious when storage condition is slightly offset from chemical tin technology; Especially bad, when chemical tin wears out (copper ion concentration is higher in the solution), even just finished its coating of technology of chemical tin with regard to the phenomenon of appearance jaundice.
Summary of the invention
In order to overcome the above-mentioned shortcoming that existing technology exists, the invention provides a kind of chemical tin post-treatment solution, solve the chemical plating stannum coating in the problem of finishing chemical tin technology and turning to be yellow at memory period, guarantee the soldering reliability that follow-up electronic devices and components are surface-mounted, effectively promoted quality product.
The technical scheme that the problem of solution chemical tin provided by the invention surface jaundice adopts is: a kind of chemical tin post-treatment solution comprises: a kind of organic acid or mineral acid, the perhaps mixing acid of two kinds of acid, the aqueous solution of organic sequestering agent and tensio-active agent.
Furthermore, in the described liquid composite, contain organic acid and/or the mineral acid of 0.2 ~ 5g/l; 0.05 the organic sequestering agent of ~ 0.5g/l; 0.0005 the tensio-active agent of ~ 0.5g/l.
Organic acid wherein comprises in citric acid, oxysuccinic acid, gluconic acid, oxyacetic acid, the tosic acid any or the two above mixture.
Mineral acid wherein comprises sulfuric acid, phosphoric acid or the mixture of the two.
Organic sequestering agent wherein includes machine phosphonic acid and salt thereof; Can be sodium ethylenediamine tetramethylenephosphonate, hydroxy ethylene diphosphonic acid, Amino Trimethylene Phosphonic Acid.
Wherein tensio-active agent comprises among the PEG 400 to PEG1500 any or the mixture more than the two.
By technique scheme, advantage and beneficial effect that chemical tin post-treatment solution composition of the present invention has are:
The present invention increases post-treatment solution matting of the present invention behind the traditional chemical process of tin, can effectively alleviate, prevent the problem of chemical tin tin face jaundice.The present invention can guarantee the soldering reliability that follow-up electronic devices and components are surface-mounted, has effectively promoted quality product.
Embodiment
A kind of chemical tin post-treatment solution of the present invention has comprised a kind of organic acid or mineral acid, the perhaps mixing acid of two kinds of acid, the aqueous solution of organic sequestering agent and tensio-active agent.
Described organic acid comprises citric acid, oxysuccinic acid, gluconic acid, oxyacetic acid, tosic acid; Described mineral acid comprises sulfuric acid, phosphoric acid; Described organic sequestering agent includes machine phosphonic acid and salt thereof; Can be sodium ethylenediamine tetramethylenephosphonate, hydroxy ethylene diphosphonic acid, Amino Trimethylene Phosphonic Acid; Described tensio-active agent comprises among the PEG 400 to PEG 1500 any or the mixing more than the two.
The compound method of chemical tin post-treatment solution of the present invention is: at room temperature, add 0.2-5 gram mineral acid, organic acid or mixing acid in 1 premium on currency, 0.05-0.5 restrains organic sequestering agent, 0.0005 to 0.5 gram tensio-active agent.
Chemical tin post-treatment solution of the present invention, its using method comprise traditional chemical process of tin step:
1, acid clean, fully washing then;
2, microetch coarse surface, and fully washing;
3, pre-zinc-plated processing;
4, chemical tin is handled, fully washing;
5, chemical tin post-treatment solution, fully washing;
6, drying.
Be concrete effect experimental example below:
1, get and finish anti-welding operation and treat four of last surface-treated circuit cards, size 5cm X 10cm, (SkyPosit Sn950 technology, the sky, Guangzhou holds chemical company limited in technical process through chemical tin.The chemical tin SkyPosit Sn950 solution of new preparation), four all evenly pure white, nothing jaundice of circuit card tin face, wherein three (being labeled as A, B, C respectively) cleans through post-treatment solution of the present invention, concrete aftertreatment cleaning condition such as subordinate list one, these three circuit cards and an other circuit card (being labeled as D) that passes through the post-treatment solution cleaning are all under constant temperature (45 ℃) constant humidity (85%) condition then, place to take out after three months and observe, the results are shown in subordinate list two.
2, get in addition and finish anti-welding operation and treat two of last surface-treated circuit cards, size 5cm X 10cm, (SkyPosit Sn950 technology, the sky, Guangzhou holds chemical company limited in technical process through chemical tin.The chemical tin SkyPosit Sn950 solution that production line is aging, copper ion concentration 7.8g/l in the chemical tin solution), there is slight jaundice on two circuit cards (mark is respectively E, F) chemical tin surface, wherein a circuit card that is labeled as E cleans (concrete aftertreatment cleaning condition such as subordinate list one) through post-treatment solution of the present invention, tin surfaces is evenly pure white, does not have the jaundice phenomenon.
Table one: post-treatment solution preparation and clean condition
These two circuit cards (E and F) all under constant temperature (45C) constant humidity (85%) condition, are placed to take out after three months and are observed, and the results are shown in subordinate list two.
Table two yellowing phenomenon result
* the circuit card of mark D and F does not clean through the chemical tin post-treatment solution.
Clearly show from above-mentioned test result, behind the traditional chemical process of tin, increase post-treatment solution matting of the present invention, can effectively alleviate, prevent the problem of chemical tin tin face jaundice.
The above, it only is preferred embodiment of the present invention, be not that the present invention is done any pro forma restriction, so every technical solution of the present invention content that do not break away from,, all still belong in the scope of technical solution of the present invention any simple modification, equivalent variations and modification that above embodiment does according to technical spirit of the present invention.