DE2207769C3 - Solvents for epoxy and polyester resins as well as methods for releasing metal parts embedded in epoxy or polyester resins - Google Patents

Description

The invention relates to a solvent for dissolving or partially dissolving from epoxy resin or Plastics formed from polyester resins, consisting of a mixture formed from organic acids, in which contains methylene chloride and formic acid. The invention also relates to a method for releasing or partially releasing metal parts made of plastic, in particular from a plastic part formed entirely or partially from epoxy resin or polyester resin.

For testing vias on printed circuit boards it is often necessary to expose connection points. Furthermore, it is often useful before use of a material intended for the manufacture of printed circuit boards, but unknown, the nature of the resin base determine.

Various resins including Polyester resins, are right resistant to organic acids. Are z. B. Machines or devices with polyester resins contaminated, then one uses - provided that mechanical removal of such impurities, z. B. by grinding, should be avoided - a highly concentrated nitric acid. It goes without saying that when using such highly concentrated inorganic acids, the parts made of metal also be attacked. Intended to assess vias in various printed circuit boards Metal compounds are exposed, it is also desirable that these are undamaged Can be tested. To dissolve epoxy resins, it is known to also use methylene chloride in Use in conjunction with formic acid. However, there is the disadvantage here that on the one hand the solution process takes a relatively long time and on the other hand such organic acids that also attack metal parts.

The invention is therefore based on the object of avoiding the aforementioned disadvantages To create solvents for epoxy resin and polyester resin, which are particularly suitable for this should be to solve plastics of the aforementioned type quickly, but not attack metal parts. It was found that a solvent made up of a mixture of

40-40% by weight,

preferably 74% by weight methylene
chloric !.

IO

15th

20th

30th

40

5-40% by weight,

preferably 20% by weight formic acid,

04-10% by weight,

preferably 5% by weight monochloroacetic acid and

04-10% by weight,

preferably 1% by weight glycerine
or glycol

the desired requirements met Compared to the known solvents for dissolving resins aforementioned type z. B. also of lacquers and paints, the one formed according to the invention differs Solvent in particular through the addition of a very strong organic acid, namely monochloroacetic acid and the addition of glycerine or glycol. The monochloro acetic acid serves as an accelerator for Accelerating the dissolution process, where however the glycerine or glycol during the dissolution process and after the dissolution process has taken place, the metal parts embedded in the workpiece are wetted with a protective film This prevents air and acid from coming in until the loosened or loosened ones are rinsed out Metal parts prevented It is important here that the maximum amount of 10 wt .-% of monochloroacetic acid must not be exceeded, otherwise the very thin protective film cannot take effect. The aim is to remove metal parts that are quite sensitive to attack by monochloroacetic acid from circuit boards it is advisable to keep the proportion of this acid low within the specified amount. The values mentioned with preference thus represent an optimum, namely when using the Solvent for dissolving epoxy and polyester resins that bond with metal parts of various types of metal are in a mechanical bond.

As a solvent for dissolving metal parts from plastics, such as epoxy resins, it is known to use organic acids to which phenols or cresols are added. The latter substances are, however, at difficult to remove in a subsequent treatment of the wastewater.

For detaching or partially detaching metal parts from one made of epoxy resin or polyester resin existing plastic part, preferably a printed circuit board, is the plastic part according to the invention in a solvent consisting of

40-90 wt. O / o,

preferably 74% by weight methylene chloride,

5-40% by weight,

preferably 20% by weight formic acid,

0.5-10 wt. O / o,

preferably 5% by weight monochloroacetic acid,

0.5-10% by weight,

preferably 1% by weight glycerine
or glycol

embedded. In this way it is possible to use the metal structure of e.g. B. plated through double-laminated or to expose multi-layer printed circuit boards without mechanical processing. It can be that Quality of the »hollow rivets« produced during the galvanic treatment, also from the outside be examined. In a corresponding manner, metal parts contaminated with such resins can be removed

3 4

clean. Impurities on fixed equipment writings for handling corrosive chemicals

th and racks will apply to the invention.

Solvent mixture wetted and after an empirical If the solvent is known, so can also by

to be determined dissolution time rubbed off. It will do the spectrographic analysis of the solution for that

however, it should be noted that the resin used in application 5 determines circuit board manufacture

of this solvent the special safety precautions.

Claims (2)

Patent claims: 1. Solution center! for dissolving (partially) dissolving plastics made from epoxy or polyester resins, which contains a mixture of organic acids as well as "> methylene chloride and formic acid, thereby marked that it was made 40 to 90 weight percent methylene chloride
5 to 40% by weight formic acid
04 to 10% by weight monochloroacetic acid,
0.1 to 10 wt% glycerin or glycol consists 2. Use of a solvent mixture according to claim 1 for dissolving plastics with metal parts embedded therein or in an adhesive bond.