GB2084865A

GB2084865A - Machine for washing printed circuit boards

Info

Publication number: GB2084865A
Application number: GB8130488A
Authority: GB
Original assignee: EASIFORM ENGINEERING Ltd
Current assignee: EASIFORM ENGINEERING Ltd
Priority date: 1980-10-09
Filing date: 1981-10-08
Publication date: 1982-04-21
Also published as: GB2084865B

Abstract

A machine for washing and drying printed circuit boards comprises a chamber 1 in which the boards to be washed are placed, a water inlet 2 and outlet 7, a water heater 3, a pump 4 for pumping water through sprayer 5 at the boards and recirculating it, and air heating and circulating means 8, 9 for blowing warm air over the washed boards in order to dry them. <IMAGE>

Description

SPECIFICATION Improvements in or relating to apparatus for washing and cleaning printed circuit boards This invention relates to an improved apparatus for the washing and cleaning of printed circuit boards and is primarily directed to an apparatus for washing boards using water together with an appropriate detergent to clean and remove residue from assembled electronic circuit board units.

According to this invention there is provided an apparatus for washing and cleaning printed circuit boards comprising a cabinet having a chamber into which one or more circuit boards may be loaded, a water inlet and water heating means through which heated water may be supplied to the chamber pump means through which water within the chamber may be circulated to effect washing of the boards, drain means by which water may be drained from the chamber, and air heating and circulating means by which warm air may be circulated over the circuit boards to dry same following washing.

Preferably the apparatus comprises a control means whereby the circuit boards, which may be assembled and retained within a rack system, are processed in an automatic manner by effecting a washing, initial rinse, final rinse and drying cycle. Drying of printed circuit boards can be problematic in so far as heat absorption and retention is poor which makes water removal through evaporation difficult.

One of the features of the present invention is the provision of an air circulating fan or turbine through which air may be subject to preheating and thereafter passed over the boards in order to effect drying of same whilst within the cabinet of the apparatus. The air circulating means is preferably operable to effect a high turbulence and pressure increase within the cabinet, thereby to physically dislodge and vapourize water droplets, with an appropriate exhaust being provided to ensure a constant throughput of air whereby the dew point within the cabinet is maintained at a low and constant level through ejection of the water saturated air. In a preferred arrangement a non-ionic rinsing medium is added to the final wash in order to reduce water surface tension which assists the action of water removal by means of the air circulating means.

A further feature of this invention is the provision of a preheated quantity of water which is caused to circulate within the chamber thus avoiding lengthy heating times hitherto required prior to effecting the washing process. A further advantage is that the quantity of water is available immediately at the precise required temperature, thus reducing the washing cycle time and operating costs. It is preferred to use a detergent medium in order to remove flux residues during the washing and to achieve an adequate cleaning performance. Means may be provided to ensure that the detergent addition is made automatically and in a precise and accurately controlled percentage dose.

This invention also provides a method for cleaning printed circuit boards comprising the steps of a) loading printed circuits into a chamber on a rack system, wherein the boards are held in spaced relationship, b) directing a high pressure recirculated water spray containing a washing agent at the boards for a predetermined time to effect cleaning therefrom of residues, c) directing a high pressure recirculated rinsing water spray at the boards.

One embodiment according to the invention is shown by way of an example in the accompanying drawings, wherein: Figure 1 shows schematically and in crosssection a cleaning apparatus according to the invention, and Figure 2 illustrates the processing cycle in block schematic form.

Referring to Fig. 1, the apparatus comprises a chamber 1 which is adapted to receive printed circuit boards, for example by means of a racking system with an inlet 2 for water preheated through a temperature controlled heater means 3. A pump means 4 is provided whereby a pressurised spray of water may be produced within the chamber 1 by means of a wash spray bar 5. The pump 4 recovers water from the bottom of the chamber and recirculates same.

Following the washing cycle, which may be repeated through further water changes being introduced, a pump 6 is utilized to remove the water from the chamber 1 through an outlet 7 and in order to effect drying of the boards a turbine impeller 8 is located in an upper part of the cabinet and arranged to draw in air over the heating means 9. The impeller 8 provides a high turbulence and increases the pressure within the chamber 1 whereby surplus moisture is driven off from the boards and passed through an exhaust outlet 9.

The sequence of operations carried out by the drying apparatus is effected automatically in accordance with a prearranged time cycle and Fig. 2 illustrates a typical programme.

As shown in Fig. 2, preheated quantity of water together with the addition of detergent is used at stage 10 to effect washing and removal of residues from the circuit boards, following which drainage of the water occurs at 11. Preheated water is again used at stage 1 2 in order to rinse the boards and drained at 13 followed by a further rinsing cycle 14 with drainage at 15. Following this drying is accomplished through the turbine with heated air input at 16 after which the cleaned boards may be removed.

The invention enables circuit board assemblies which have used active fluxes to be adequately washed and passivated without the need for expensive in-line cleaning equipment.

Claims

1. An apparatus for washing and cleaning printed circuit boards comprising a cabinet housing a chamber into which one or more circuit boards may be loaded, a water inlet and water heating means through which heated water may be supplied to the chamber pump means through which water within the chamber may be circulated to effect washing of the boards, drain means by which water may be drained from the chamber, and air heating and circulating means by which warm air may be circulated over the circuit boards to dry same following washing.

2. An apparatus in accordance with Claim 1, wherein said pump means feeds a plurality of spray nozzles forming pressure jets to effect washing of the boards.

3. An apparatus in accordance with Claim 1 or 2, wherein the air heating and circulating means provides an excess air pressure within the chamber.

4. An apparatus in accordance with Claim 3, wherein the air circulating means comprises a fan or turbine drawing air into the chamber over a heating means, the chamber having a flow restricting exhaust.

5. An apparatus in accordance with any preceding claim, including a control means operative to sequentially operate the water inlet and heating means, the pump means, the drain means and the air heating and circulating means, in accordance with a prefined time sequence.

6. An apparatus in accordance with any preceding claim, including a means for adding a dosage of a detergent to the washing water.

7. A method for cleaning printed circuit boards comprising the steps of: a) loading printed circuits into a chamber on a rack system, wherein the boards are held in spaced relationship, b) directing a high pressure recirculated - water spray containing a washing agent at the boards for a predetermined time to effect cleaning therefrom of residues, c) directing a high pressure recirculated rinsing water spray at the boards, d) circulating heated external air over the boards whilst maintaining an excess pressure within the chamber through a flow restricting air exhaust to effect drying.

8. Apparatus for washing circuit boards as herein described and as shown in the accompanying drawing.