Printed circuit board having an injection molded substrate

• US 4,996,391 A
• Filed: 08/03/1989
• Issued: 02/26/1991
• Est. Priority Date: 09/30/1988
• Status: Expired due to Fees

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Schmidt, Hans
• Primary Examiner(s): Nimmo, Morris H.
• Application Number:
  US07/388,818
• Time in Patent Office: 572 Days
• Field of Search: 174/68.5, 174/250, 174/255, 174/261, 174/266, 29/848, 29/849, 29/852, 361/419
• US Class Current: 174/255
• CPC Class Codes: H05K 1/00 Printed circuits
• CPC Class Codes: H05K 1/116 Lands, clearance holes or other lay-out details concerning the surrounding of a via
• CPC Class Codes: H05K 2201/0376 Flush conductors, i.e. flush with the surface of the printed circuit
• CPC Class Codes: H05K 2201/09036 Recesses or grooves in insulating substrate recess in metallic substrate H05K2201/09745
• CPC Class Codes: H05K 2201/09118 Moulded substrate
• CPC Class Codes: H05K 2201/09827 Tapered, e.g. tapered hole, via or groove bevelled, chamferred or tapered edge H05K2201/09154
• CPC Class Codes: H05K 2201/09845 Stepped hole, via, edge, bump or conductor
• CPC Class Codes: H05K 2201/09981 Metallised walls
• CPC Class Codes: H05K 2203/0143 Using a roller; Specific shape thereof; Providing locally adhesive portions thereon
• CPC Class Codes: H05K 2203/0571 Dual purpose resist, e.g. etch resist used as solder resist, solder resist used as plating resist
• CPC Class Codes: H05K 2203/0574 Stacked resist layers used for different processes
• CPC Class Codes: H05K 2203/1415 Applying catalyst after applying plating resist
• CPC Class Codes: H05K 3/064 Photoresists
• CPC Class Codes: H05K 3/107 by filling grooves in the support with conductive material H05K3/045, H05K3/101, H05K3/1258 and H05K3/465 take precedence
• CPC Class Codes: H05K 3/184 using masks
• CPC Class Codes: H05K 3/28 Applying non-metallic protective coatings H05K3/0091 takes precedence; methods for intermediate insulating layers for build-up multilayer circuits H05K3/4673
• CPC Class Codes: H05K 3/426 initial plating of through-holes in substrates without metal
• CPC Class Codes: Y10T 29/4916 Simultaneous circuit manufacturing
• CPC Class Codes: Y10T 29/49165 by forming conductive walled aperture in base

Abstract

A printed circuit board includes an injected molded substrate having a pattern recessed in the substance surface of interconnect traces, through-connections and connecting rods. A trench-shaped depression is provided in the substrate surface in the region of each interconnect trace, and a planar depression is provided in the substrate'"'"'s surface in at least one of (a) the region of each through-connection and (b) the region of each contact surfacae. The pattern of recesses is covered with a conductive metal coat, and the depth of each planar depression is greater than the depth of each trench-shaped depression, so that the metal coat fills the trench-shaped depressions to the surface of the substrate, while in the planar depressions a distance remains between the metal coat and the surface of the substrate. A solder stop lacquer can then be applied such as by roller coating, without the necessity of photo-structuring and without filling the planar depressions.

Claims

1. A printed circuit board comprising:

an injection molded substrate having a surface;

a pattern of interconnect traces, through-connections and connecting pads recessed in said substrate surface formed by a trench-shaped depression in the region of each interconnect trace and by a planar depression in at least one of (a) the region of each through-connection and (b) the region of each connecting pad; and

said planar and trench-shaped depressions having a conductive metal coat, the depth of each trench-shaped depression being dimensioned less than the depth of each planar depression, so that, as a result of the difference in depth between each trench-shaped depression and each planar depression, said metal coat fills each trench-shaped depression to the surface of the substrate, and in each planar depression a distance remains between the metal coat and the surface of the substrate.

2. A printed circuit board as claimed in claim 1 further comprising a tin layer applied by hot-tinning covering said metal coat.

3. A printed circuit board as claimed in claim 1 wherein said metal coat consists of copper chemically applied to said substrate.

4. A printed circuit board as claimed in claim 1 wherein the depth of said planar depressions is greater than the depth of said trench-shaped depressions by at least a factor 1.5.

5. A method for manufacturing a circuit board comprising:

generating a pattern of recesses in a surface of a substrate by forming a trench-shaped depression in the region of an interconnect trace and by forming a planar depression in at least one of (a) the region of a through-connection or (b) the region of a connecting pad, with the depth of said trench-shaped depression being less than the depth of said planar depression; and

applying a metal coat to said substrate so that, as a result of the difference in depth between said trench-shaped depression and said planar depression, said metal coat fills said trench-shaped depression to said surface of said substrate and in said planar depression a distance remains between the metal coat and said surface of said substrate.

6. A method as claimed in claim 5 comprising the additional step of:

covering said metal coat with a tin layer by hot-tinning.

7. A method as claimed in claim 5 wherein the step of applying said metal coat is further defined by chemically applying a copper coat to said substrate.

8. A method as claimed in claim 5 wherein the step of generating a pattern is further defined by generating a pattern of recesses in a surface of a substrate by forming a trench-shaped depression in the region of an interconnect trace and by forming a planar depression in at least one of (a) the region of a through-connection or (b) the region of a connecting pad, with the depth of said planar depression being greater than the depth of said trench-shaped depression by a factor of 1.5.

9. A printed circuit board comprising:

an injection molded substrate having a surface, the surface having a planar depression and a trench-shaped depression disposed therein, the trench-shaped depression having a metal coat to form an interconnect trace, the planar depression having a metal coat to form one of (a) a through-connection or (b) a connecting pad;

the trench-shaped depression and the planar depression each having a depth, the depth of the planar depression being greater than the depth of the trench-shaped depression so that when the metal coat is applied to the printed circuit board the metal coat fills the trench-shaped depression to the surface of the substrate while a distance remains between the metal coat and the surface of the substrate at the planar depression.

10. A printed circuit board as claimed in claim 9, further comprising a tin layer applied by hot-tinning covering the metal coat.

11. A printed circuit board as claimed in claim 9, wherein the metal coat comprises copper chemically applied to the substrate.

12. A printed circuit board as claimed in claim 9, wherein the planar depression is deeper than the trench-shaped depression by a factor greater than 1.5.

13. A method for manufacturing a circuit board from a substrate having a surface, the method comprising the steps of:

forming a trench-shaped depression in the surface of the substrate in the region of an interconnect trace that is to be placed on the circuit board;

forming a planar depression in the surface of the substrate in at least one of (a) the region of a through-connection that is to be disposed through the circuit board or (b) the region of a connecting pad that is to be placed on the circuit board, the planar depression having a greater depth in comparison to the trench-shaped depression; and

applying a metal coat to the substrate so that, as a result of the difference in depth between the planar depression and the trench shaped depression, the metal coat fills the trench-shaped depression to the surface of the substrate and in the planar depression a distance remains between the metal coat and the surface of the substrate.

14. A method as claimed in claim 13, further comprising the step of covering the metal coat with a tin layer by hot-tinning.

15. A method as claimed in claim 13, wherein the step of applying the metal coat is further defined by chemically applying a copper coat to the substrate to form the circuit board.