Sealant against potting compound

• US 20020043549A1
• Filed: 10/02/2001
• Published: 04/18/2002
• Est. Priority Date: 10/02/2000
• Status: Active Grant

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Taylor, Russell, Copeland, Tom
• Granted Patent: US 6,592,018 B2
• Time in Patent Office: Days
• US Class Current: 228/179.1
• CPC Class Codes: H05K 2201/09909 Special local insulating pattern, e.g. as dam around component
• CPC Class Codes: H05K 3/284 for encapsulating mounted components H05K1/185 takes precedence
• CPC Class Codes: H05K 3/325 by abutting or pinching, i.e. without alloying process; mechanical auxiliary parts therefor adaptations of leads inserted in holes for press-fit connections H05K3/308
• CPC Class Codes: H05K 3/3452 Solder masks

Abstract

The present invention relates to the use of a peelable anti-solder mask as a sealant against potting compound. In certain electrical apparatus, a modular component (300) must be attached to a side of a printed circuit board (PCB) (110) which has previously been exposed to solder. Solder ‘pick up’ is prevented by application of a removable mask (202) over areas of the exposed side of the PCB (110) which will receive the modular component (300). Potting compound is used to protect components of electrical circuits (108) from vibration, moisture and static discharges. The anti-solder mask (202) can be used as a thin gasket to prevent the ingress of potting compound between the modular component (300) and the PCB (110).

Claims

1. A method for assembling an electrical device having a printed circuit board (110), the printed circuit board (110) having a first side (110A) and a second side (110A) and being provided with slots (412) for receiving conducting legs (414) of at least one electrical component (108), the method including the steps of:

a) masking an area (202,204) of the second side (110B) of the printed circuit board (110) with a solder-repellent mask, the masked area (202,204) comprising a first portion (204) and a second portion (202);

b) disposing said at least one electrical component (108) on the first side (110A) of the printed circuit board (110) with the conducting legs (414) extending through the slots (412) from the first side (110A) to the second side (110B);

c) fixing said at least one electrical component (108) in place by exposing the second side (110B) to solder (410) and allowing the solder (410) to solidify;

the method characterised by further including;

d) removing the solder-repellent mask from the first portion (204) to expose at least one contact (408) while leaving the solder-repellent mask in place over the second portion (202); and

e) disposing a further electrical component (300) directly against the second side (110B), a lower surface of the further electrical component (300) lying adjacent to the second side (110B), the second portion (202) corresponding to at least those points of the masked area (202,204) at which the lower surface of the further electrical component (300) touch the masked area (202,204), the second portion (202) thereby forming a seal between the further electrical component (300) and the second side (110B) of the printed circuit board (110).

2. A method according to claim 1, further including the step of:

f) submerging the electrical device in a potting compound, the second portion (202) preventing the ingress of potting compound between the further electrical component (300) and the printed circuit board (110).

3. A method according to claim 1, wherein the masked area (202,204) is a single contiguous area.

4. A method according to claim 3, wherein the second portion (202) is an outer portion of the masked area (202,204) and the first portion (204) is an inner portion of the masked area (202,204), all points on the periphery of the masked area (202,204) lying within the second portion (202).

5. A method according to claim 1, wherein the exposure to solder in step c) is achieved through a flow solder technique.

6. A method according to claim 1, wherein the further electrical component (300) is an inverter module.

7. A peelable mask for masking a printed circuit board (110) from solder pick up when solder is applied to the printed circuit board (110) and for sealing a gap between an electronic component (300) and the printed circuit board (110) from the ingress of a potting compound.

8. A peelable mask according to claim 7, wherein the mask covers a masked area (202,204) having an inner portion (204) and an outer portion (202), the mask covering the inner portion (204) being removed subsequent to soldering.